Klebsiella spp. as nosocomial pathogens: epidemiology, taxonomy, typing methods, and pathogenicity factors

Targeting bacterial growth in biofilm conditions: rational design of novel inhibitors to mitigate clinical and food contamination using QSAR

Antimicrobial resistance (AMR) is a pressing global issue exacerbated by the abuse of antibiotics and the formation of bacterial biofilms, which cause up to 80% of human bacterial infections. This study presents a computational strategy to address AMR by developing three novel quantitative structure-activity relationship (QSAR) models based on molecular topology to identify potential anti-biofilm and antibacterial agents. The models aim to determine the chemo-topological pattern of Gram (+) antibacterial, Gram (-) antibacterial, and biofilm formation inhibition activity. The models were applied to the virtual screening of a commercial chemical database, resulting in the selection of 58 compounds. Subsequent in vitro assays showed that three of these compounds exhibited the most promising antibacterial activity, with potential applications in enhancing food and medical device safety.

The interplay of co-infections in shaping COVID-19 severity: Expanding the scope beyond SARS-CoV-2

High mortality has been reported in severe cases of COVID-19. Emerging reports suggested that the severity is not only due to SARS-CoV-2 infection, but also due to coinfections by other pathogens exhibiting symptoms like COVID-19. During the COVID-19 pandemic, simultaneous respiratory coinfections with various viral (Retroviridae, Flaviviridae, Orthomyxoviridae, and Picoviridae) and bacterial (Mycobacteriaceae, Mycoplasmataceae, Enterobacteriaceae and Helicobacteraceae) families have been observed. These pathogens intensify disease severity by potentially augmenting SARSCoV-2 replication, inflammation, and modulation of signaling pathways. Coinfection emerges as a critical determinant of COVID-19 severity, principally instigated by heightened pro-inflammatory cytokine levels, as cytokine storm. Thereby, in co-infection scenario, the severity is also driven by the modulation of inflammatory signaling pathways by both pathogens possibly associated with interleukin, interferon, and cell death exacerbating the severity. In the current review, we attempt to understand the role of co- infections by other pathogens and their involvement in the severity of COVID-19.

Bacteraemia associated with multiple septic localizations caused by Klebsiella pneumoniae sequence type ST660

We report a case of Klebsiella pneumoniae bacteraemia in an 80-year-old man in France with no history of travel to Asia, complicated by endogenous endophthalmitis, multiple cerebral microbleeds and hepatic microabscesses, associated with a Bentall endocarditis. Hypervirulence pathotype was suggested based on clinical picture, bacterial isolate genomic sequence and hypermucoidy. Interestingly, the isolate had the non-K1/K2-capsular serotype locus KL113-like, carried a KpVP-1-like virulence plasmid, and belonged to the emerging sublineage SL660 (comprising the sequence type ST660).

Changing Landscape of Antimicrobial Resistance in Neonatal Sepsis: An in silico Analyses of Multidrug Resistance in Klebsiella pneumoniae

BACKGROUND

Neonatal sepsis poses a critical healthcare concern, as multidrug-resistant Klebsiella pneumoniae ( K. pneumoniae ) infections are on the rise. Understanding the antimicrobial susceptibility patterns and underlying resistance mechanism is crucial for effective treatment.

OBJECTIVES

This study aimed to comprehensively investigate the antimicrobial susceptibility patterns of K. pneumoniae strains responsible for neonatal sepsis using in silico tools. We sought to identify trends and explore reasons for varying resistance levels, particularly for β-lactams and fluoroquinolone.

METHODS

K. pneumoniae isolated from neonates at Kanchi Kamakoti CHILDS Trust Hospital (2017-2020) were analyzed for antimicrobial resistance. Elevated resistance to β-lactam and fluoroquinolone antibiotics was further investigated through molecular docking and interaction analysis. β-lactam affinity with penicillin-binding proteins and β-lactamases was examined. Mutations in ParC and GyrA responsible for quinolone resistance were introduced to investigate ciprofloxacin interactions.

RESULTS

Of 111 K. pneumoniae blood sepsis isolates in neonates, high resistance was detected to β-lactams such as cefixime (85.91%, n = 71), ceftriaxone (84.9%, n = 106), cefotaxime (84.9%, n = 82) and fluoroquinolone (ciprofloxacin- 79.44%, n = 107). Molecular docking revealed low β-lactam binding toward penicillin-binding proteins and higher affinities for β-lactamases, attributing to the reduced β-lactam efficiency. Additionally, ciprofloxacin showed decreased affinity toward mutant ParC and GyrA in comparison to their corresponding wild-type proteins.

CONCLUSION

Our study elucidates altered resistance profiles in neonatal sepsis caused by K. pneumoniae , highlighting mechanisms of β-lactam and fluoroquinolone resistance. It underscores the urgent need for the development of sustainable therapeutic alternatives to address the rising antimicrobial resistance in neonatal sepsis.

A rare case of hypervirulent Klebsiella pneumoniae liver abscess and bacterial endophthalmitis associated with distal bile duct cancer

We report a case of a patient with distal bile duct cancer who presented with ocular pain and eye redness due to a liver abscess. The patient developed a liver abscess while waiting for surgery. Since Klebsiella pneumoniae with high viscosity was identified and imaging studies showed systemic infection, a diagnosis of klebsiella invasive syndrome was made. In addition, infectious intraocular inflammation was also observed at the same time. In addition to antibiotic therapy, vitrectomy and percutaneous transhepatic abscess drainage successfully normalized the inflammatory response and negative blood cultures were obtained. Thirty-four days after the start of treatment, surgery was performed and the postoperative course was uneventful, and the patient was discharged from the hospital on the 39th postoperative day. Forty-six months after that surgery, there has been no evidence of recurrence of cholangiocarcinoma or recurrence of infection, but unfortunately, vision loss in the right eye remains. Some Klebsiella pneumoniae are highly pathogenic and are often reported from Southeast Asia, and ocular pain and hyperemic symptoms are important physical findings.

Complete genome sequences of Klebsiella pneumoniae bacteriophages YMR1 and YMR2 isolated from sewage

Two Klebsiella pneumoniae bacteriophages, YMR1 and YMR2, which form plaques with halos, were isolated from sewage in Seoul, South Korea. YMR1 and YMR2 have double-stranded DNA genomes of 40,338 bp and 40,756 bp with 49 and 52 predicted protein-coding genes, respectively. Both are predicted to be members of the family Autographiviridae.

The transcriptional regulator Fur modulates the expression of uge, a gene essential for the core lipopolysaccharide biosynthesis in Klebsiella pneumoniae

BACKGROUND

Klebsiella pneumoniae is a Gram-negative pathogen that has become a threat to public health worldwide due to the emergence of hypervirulent and multidrug-resistant strains. Cell-surface components, such as polysaccharide capsules, fimbriae, and lipopolysaccharides (LPS), are among the major virulence factors for K. pneumoniae. One of the genes involved in LPS biosynthesis is the uge gene, which encodes the uridine diphosphate galacturonate 4-epimerase enzyme. Although essential for the LPS formation in K. pneumoniae, little is known about the mechanisms that regulate the expression of uge. Ferric uptake regulator (Fur) is an iron-responsive transcription factor that modulates the expression of capsular and fimbrial genes, but its role in LPS expression has not yet been identified. This work aimed to investigate the role of the Fur regulator in the expression of the K. pneumoniae uge gene and to determine whether the production of LPS by K. pneumoniae is modulated by the iron levels available to the bacterium.

RESULTS

Using bioinformatic analyses, a Fur-binding site was identified on the promoter region of the uge gene; this binding site was validated experimentally through Fur Titration Assay (FURTA) and DNA Electrophoretic Mobility Shift Assay (EMSA) techniques. RT-qPCR analyses were used to evaluate the expression of uge according to the iron levels available to the bacterium. The iron-rich condition led to a down-regulation of uge, while the iron-restricted condition resulted in up-regulation. In addition, LPS was extracted and quantified on K. pneumoniae cells subjected to iron-replete and iron-limited conditions. The iron-limited condition increased the amount of LPS produced by K. pneumoniae. Finally, the expression levels of uge and the amount of the LPS were evaluated on a K. pneumoniae strain mutant for the fur gene. Compared to the wild-type, the strain with the fur gene knocked out presented a lower LPS amount and an unchanged expression of uge, regardless of the iron levels.

CONCLUSIONS

Here, we show that iron deprivation led the K. pneumoniae cells to produce higher amount of LPS and that the Fur regulator modulates the expression of uge, a gene essential for LPS biosynthesis. Thus, our results indicate that iron availability modulates the LPS biosynthesis in K. pneumoniae through a Fur-dependent mechanism.

Vaccine value profile for Klebsiella pneumoniae

Klebsiella pneumoniae causes community- and healthcare-associated infections in children and adults. Globally in 2019, an estimated 1.27 million (95% Uncertainty Interval [UI]: 0.91-1.71) and 4.95 million (95% UI: 3.62-6.57) deaths were attributed to and associated with bacterial antimicrobial resistance (AMR), respectively. K. pneumoniae was the second leading pathogen in deaths attributed to AMR resistant bacteria. Furthermore, the rise of antimicrobial resistance in both community- and hospital-acquired infections is a concern for neonates and infants who are at high risk for invasive bacterial disease. There is a limited antibiotic pipeline for new antibiotics to treat multidrug resistant infections, and vaccines targeted against K. pneumoniae are considered to be of priority by the World Health Organization. Vaccination of pregnant women against K. pneumoniae could reduce the risk of invasive K.pneumoniae disease in their young offspring. In addition, vulnerable children, adolescents and adult populations at risk of K. pneumoniae disease with underlying diseases such as immunosuppression from underlying hematologic malignancy, chemotherapy, patients undergoing abdominal and/or urinary surgical procedures, or prolonged intensive care management are also potential target groups for a K. pneumoniae vaccine. A 'Vaccine Value Profile' (VVP) for K.pneumoniae, which contemplates vaccination of pregnant women to protect their babies from birth through to at least three months of age and other high-risk populations, provides a high-level, holistic assessment of the available information to inform the potential public health, economic and societal value of a pipeline of K. pneumoniae vaccines and other preventatives and therapeutics. This VVP was developed by a working group of subject matter experts from academia, non-profit organizations, public-private partnerships, and multi-lateral organizations, and in collaboration with stakeholders from the WHO. All contributors have extensive expertise on various elements of the K.pneumoniae VVP and collectively aimed to identify current research and knowledge gaps. The VVP was developed using only existing and publicly available information.

Emergence of blaNDM-5 and blaOXA-232 Positive Colistin- and Carbapenem-Resistant Klebsiella pneumoniae in a Bulgarian Hospital

The rapid spread of carbapenemase-producing strains has led to increased levels of resistance among Gram-negative bacteria, especially enterobacteria. The current study aimed to collect and genetically characterize the colistin- and carbapenem-resistant isolates, obtained in one of the biggest hospitals (Military Medical Academy) in Sofia, Bulgaria. Clonal relatedness was detected by RAPD and MLST. Carbapenemases, ESBLs, and mgrB were investigated by PCR amplification and sequencing, replicon typing, and 16S rRNA methyltransferases with PCRs. Fourteen colistin- and carbapenem-resistant K. pneumoniae isolates were detected over five months. Six carbapenem-resistant and colistin-susceptible isolates were also included. The current work revealed a complete change in the spectrum of carbapenemases in Bulgaria. blaNDM-5 was the only NDM variant, and it was always combined with blaOXA-232. The coexistence of blaOXA-232 and blaNDM-5 was observed in 10/14 (72%) of colistin- and carbapenem-resistant K. pneumoniae isolates and three colistin-susceptible isolates. All blaNDM-5- and blaOXA-232-positive isolates belonged to the ST6260 (ST101-like) MLST type. They showed great mgrB variability and had a higher mortality rate. In addition, we observed blaOXA-232 ST14 isolates and KPC-2-producing ST101, ST16, and ST258 isolates. The colistin- and carbapenem-resistant isolates were susceptible only to cefiderocol for blaNDM-5- and blaOXA-232-positive isolates and to cefiderocol and ceftazidime/avibactam for blaOXA-232- or blaKPC-2-positive isolates. All blaOXA-232-positive isolates carried rmtB methylase and the colE replicon type. The extremely limited choice of appropriate treatment for patients infected with such isolates and their faster distribution highlight the need for urgent measures to control this situation.

Enhancing acute inflammatory and sepsis treatment: superiority of membrane receptor blockade

Conditions such as acute pancreatitis, ulcerative colitis, delayed graft function and infections caused by a variety of microorganisms, including gram-positive and gram-negative organisms, increase the risk of sepsis and therefore mortality. Immune dysfunction is a characterization of sepsis, so timely and effective treatment strategies are needed. The conventional approaches, such as antibiotic-based treatments, face challenges such as antibiotic resistance, and cytokine-based treatments have shown limited efficacy. To address these limitations, a novel approach focusing on membrane receptors, the initiators of the inflammatory cascade, is proposed. Membrane receptors such as Toll-like receptors, interleukin-1 receptor, endothelial protein C receptor, μ-opioid receptor, triggering receptor expressed on myeloid cells 1, and G-protein coupled receptors play pivotal roles in the inflammatory response, offering opportunities for rapid regulation. Various membrane receptor blockade strategies have demonstrated efficacy in both preclinical and clinical studies. These membrane receptor blockades act as early stage inflammation modulators, providing faster responses compared to conventional therapies. Importantly, these blockers exhibit immunomodulatory capabilities without inducing complete immunosuppression. Finally, this review underscores the critical need for early intervention in acute inflammatory and infectious diseases, particularly those posing a risk of progressing to sepsis. And, exploring membrane receptor blockade as an adjunctive treatment for acute inflammatory and infectious diseases presents a promising avenue. These novel approaches, when combined with antibiotics, have the potential to enhance patient outcomes, particularly in conditions prone to sepsis, while minimizing risks associated with antibiotic resistance and immune suppression.

Enhancing the antimicrobial activity of silver nanoparticles against pathogenic bacteria by using Pelargonium sidoides DC extract in microwave assisted green synthesis

This study presents an optimized microwave-assisted method for the green synthesis of silver nanoparticles (AgNPs) using a root extract obtained from Pelargonium sidoides DC. The influence of temperature, reagent concentration, and irradiation time was systematically investigated to enhance synthesis yield. Characterization techniques including XRD, UV-vis, FTIR, XPS, and zetametry were employed to confirm the successful formation of nanoparticles with a metallic silver core (∼17 nm) functionalized with organic molecules derived from the plant extract. The cytotoxicity of AgNPs was assessed using a cell viability assay, while the Minimum Inhibitory Concentration (MIC) of nanoformulation against pathogenic bacteria, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and the carbapenem-resistant Klebsiella pneumoniae (KPC), was determined using the Broth microdilution method. The nanoformulation synthesized with P. sidoides extract exhibited a dose-dependent response, demonstrating superior antimicrobial efficacy compared to the pure plant extract in most cases. The MIC values ranged from 0.85 to 17.1 μg mL-1, with particularly strong performance against the drug resistant KPC strain. The enhanced antimicrobial effect is attributed to the synergistic action of the metallic silver core and phytochemicals from P. sidoides on the surface of nanoparticles, which also contribute to notable colloidal stability of AgNPs at physiological pH levels.

A New Casjensviridae Bacteriophage Isolated from Hospital Sewage for Inactivation of Biofilms of Carbapenem Resistant Klebsiella pneumoniae Clinical Isolates

Klebsiella pneumoniae, a member of the ESKAPE pathogen group, is a prominent cause of hospital-acquired infections. The WHO has recognized carbapenem-resistant K. pneumoniae as a critical-one priority pathogen. These resilient superbugs have the ability to form biofilms and present a significant global threat. In the present study, we isolated and characterized a bacteriophage SAKp02, from hospital sewage, infectious to carbapenem-resistant K. pneumoniae patient isolates. SAKp02 could infect 43 of 72 clinical isolates, indicating a broad host spectrum. Whole genome analysis classified SAKp02 within the family Casjensviridae, with a 59,343 bp genome encoding 82 ORFs. Comparative genomic analysis revealed significant differences between SAKp02 and its closest viruses, indicating a distinct genetic makeup positioning it as a novel phage strain within the lineage. The SAKp02 genome comprises bacteriolytic enzymes, including holin, endolysin, and phage depolymerase, crucial for bacterial lysis and biofilm disruption. It reduced biofilm biomass by over threefold compared to the control and eradicated 99% of viable cells within a 4 h treatment period. Scanning electron microscopy corroborated the ability of the phage to dismantle biofilm matrices and lyse bacterial cells. Safe and effective treatments are warranted, and hence, the fully characterized lytic phages with therapeutic potential against drug-resistant clinical isolates of bacteria are needed. Our study is the first to report the antibacterial and antibiofilm activity of Casjensviridae phages, and our discovery of a novel K. pneumoniae phage broadens the arsenal against the bacteria.

Complete genome sequence, phenotypic correlation and pangenome analysis of uropathogenic Klebsiella spp

Urinary tract infections (UTI) by antibiotic resistant and virulent K. pneumoniae are a growing concern. Understanding the genome and validating the genomic profile along with pangenome analysis will facilitate surveillance of high-risk clones of K. pneumoniae to underpin management strategies toward early detection. The present study aims to correlate resistome with phenotypic antimicrobial resistance and virulome with pathogenicity in Klebsiella spp. The present study aimed to perform complete genome sequences of Klebsiella spp. and to analyse the correlation of resistome with phenotypic antimicrobial resistance and virulome with pathogenicity. To understand the resistome, pangenome and virulome in the Klebsiella spp, the ResFinder, CARD, IS Finder, PlasmidFinder, PHASTER, Roary, VFDB were used. The phenotypic susceptibility profiling identified the uropathogenic kp3 to exhibit multi drug resistance. The resistome and in vitro antimicrobial profiling showed concordance with all the tested antibiotics against the study strains. Hypermucoviscosity was not observed for any of the test isolates; this phenotypic character matches perfectly with the absence of rmpA and magA genes. To the best of our knowledge, this is the first report on the presence of ste, stf, stc and sti major fimbrial operons of Salmonella enterica serotype Typhimurium in K. pneumoniae genome. The study identifies the discordance of virulome and virulence in Klebsiella spp. The complete genome analysis and phenotypic correlation identify uropathogenic K. pneumoniae kp3 as a carbapenem-resistant and virulent pathogen. The Pangenome of K. pneumoniae was open suggesting high genetic diversity. Diverse K serotypes were observed. Sequence typing reveals the prevalence of K. pneumoniae high-risk clones in UTI catheterised patients. The study also highlights the concordance of resistome and in vitro susceptibility tests. Importantly, the study identifies the necessity of virulome and phenotypic virulence markers for timely diagnosis and immediate treatment for the management of high-risk K. pneumoniae clones.

Genomic characterization of Klebsiella pneumoniae carbapenemase-producing Klebsiella pneumoniae (KPC-Kp) strains circulating in three university hospitals in Northern Italy over three years

OBJECTIVES

Genomic surveillance of Klebsiella pneumoniae carbapenemase-producing Klebsiella pneumoniae (KPC-Kp) is crucial for virulence, drug-resistance monitoring, and outbreak containment.

METHODS

Genomic analysis on 87 KPC-Kp strains isolated from 3 Northern Italy hospitals in 2019-2021 was performed by whole genome sequencing (WGS), to characterize resistome, virulome, and mobilome, and to assess potential associations with phenotype resistance and clinical presentation. Maximum Likelihood and Minimum Spanning Trees were used to determine strain correlations and identify potential transmission clusters.

RESULTS

Overall, 15 different STs were found; the predominant ones included ST307 (35, 40.2%), ST512/1519 (15, 17.2%), ST20 (12, 13.8%), and ST101 (7, 8.1%). 33 (37.9%) KPC-Kp strains were noticed to be in five transmission clusters (median number of isolates in each cluster: 5 [3-10]), four of them characterized by intra-hospital transmission. All 87 strains harbored Tn4401a transposon, carrying blaKPC-3 (48, 55.2%), blaKPC-2 (38, 43.7%), and in one case (1.2%) blaKPC-33, the latter gene conferred resistance to ceftazidime/avibactam (CZA). Thirty strains (34.5%) harbored porin mutations; of them, 7 (8.1%) carried multiple Tn4401a copies. These strains were characterized by significantly higher CZA minimum inhibitory concentration compared with strains with no porin mutations or single Tn4401a copy, respectively, even if they did not overcome the resistance breakpoint of 8 ug/mL. Median 2 (IQR:1-2) virulence factors per strain were detected. The lowest number was observed in ST20 compared to the other STs (p<0.001). While ST307 was associated with infection events, a trend associated with colonization events could be observed for ST20.

CONCLUSIONS

Integration of genomic, resistance score, and clinical data allowed us to define a relative diversification of KPC-Kp in Northern Italy between 2019 and 2021, characterized by few large transmission chains and rare inter-hospital transmission. Our results also provided initial evidence of correlation between KPC-Kp genomic signatures and higher MIC levels to some antimicrobial agents or colonization/infection status, once again underlining WGS's importance in bacterial surveillance.

Extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae: insights from a tertiary hospital in Southern Thailand

Broad-spectrum ampicillin-resistant and third-generation cephalosporin-resistant Enterobacteriaceae, particularly Escherichia coli and Klebsiella pneumoniae that have pathological features in humans, have become a global concern. This study aimed to investigate the prevalence, antimicrobial susceptibility, and molecular genetic features of extended-spectrum beta-lactamase (ESBL)-producing E. coli and K. pneumoniae isolates in Southern Thailand. Between January and August 2021, samples (n = 199) were collected from a tertiary care hospital in Southern Thailand. ESBL and AmpC-lactamase genes were identified using multiplex polymerase chain reaction (PCR). The genetic relationship between ESBL-producing E. coli and K. pneumoniae was determined using the enterobacterial repetitive intergenic consensus (ERIC) polymerase chain reaction. ESBL-producing E. coli and K. pneumoniae isolates were mostly collected from catheter urine samples of infected female patients. The ESBL production prevalence was highest in the medical wards (n = 75, 37.7%), followed by that in surgical wards (n = 64, 32.2%) and operating rooms (n = 19, 9.5%). Antimicrobial susceptibility analysis revealed that all isolates were resistant to ampicillin, cefotaxime, ceftazidime, ceftriaxone, and cefuroxime; 79.4% were resistant to ciprofloxacin; and 64.3% were resistant to trimethoprim-sulfamethoxazole. In ESBL-producing K. pneumoniae and E. coli, blaTEM (n = 57, 72.2%) and blaCTX-M (n = 61, 50.8%) genes were prominent; however, no blaVEB, blaGES, or blaPER were found in any of these isolates. Furthermore, only ESBL-producing K. pneumoniae had co-harbored blaTEM and blaSHV genes at 11.6%. The ERIC-PCR pattern of multidrug-resistant ESBL-producing strains demonstrated that the isolates were clonally related (95%). Notably, the presence of multidrug-resistant and extremely resistant ESBL producers was 83.4% and 16.6%, respectively. This study highlights the presence of blaTEM, blaCTX-M, and co-harbored genes in ESBL-producing bacterial isolates from hospitalized patients, which are associated with considerable resistance to beta-lactamase and third-generation cephalosporins.

IMPORTANCE

We advocate for evidence-based guidelines and antimicrobial stewardship programs to encourage rational and appropriate antibiotic use, ultimately reducing the selection pressure for drug-resistant bacteria and lowering the likelihood of ESBL-producing bacterial infections.

Comprehensive insights into Klebsiella pneumoniae: unravelling clinical impact, epidemiological trends and antibiotic-resistance challenges

Klebsiella pneumoniae, a challenging opportunistic bacterium, became a notable global health concern owing to its clinical impact, widespread epidemiology and escalating antibiotic resistance. This comprehensive review delves into the multifaceted dimensions of K. pneumoniae, with a focus on its clinical implications, epidemiological patterns and the critical issue of antibiotic resistance. The review also emphasizes the implications of K. pneumoniae in the context of antimicrobial stewardship and infection control. Epidemiological aspects are scrutinized, shedding light on the global distribution and prevalence of K. pneumoniae. Factors influencing its transmission and persistence in healthcare facilities and communities are examined, with patient demographics, healthcare practices and geographical variations. The review centres on antibiotic resistance, a critical issue in the era of bacteria displaying resistance to multiple drugs. The mechanisms of resistance used by K. pneumoniae against various classes of antibiotics are elucidated, along with the alarming rise of carbapenem-resistant strains. It also highlights ongoing research efforts and innovative strategies aimed at addressing this critical public health issue. This comprehensive review offers a holistic understanding of K. pneumoniae, emphasizing its clinical significance, global epidemiology and the immediate necessity for effective strategies to combat antibiotic resistance. It serves as a valuable resource for healthcare practitioners, researchers and policymakers seeking to manage better and mitigate the impact of this pathogen on public health.

Bacterial Contamination and Antimicrobial Resistance in Two-Spotted (Gryllus bimaculatus) and House (Acheta domesticus) Cricket Rearing and Harvesting Processes

Food safety for cricket production is a crucial factor in producing edible crickets with safety for consumers and sustainability for two-spotted (Gryllus bimaculatus) as well as house (Acheta domesticus) cricket production. This study was conducted by simultaneously rearing two cricket species, comprising two-spotted crickets (G. bimaculatus) and house crickets (A. domesticus). A total of 16 rearing crates were used for the present study, which were allocated into 8 rearing crates for each studied cricket species, including paper egg cartons. Cricket eggs were incubated in the rearing crates. Once the crickets hatched, tap water and powdered feed were provided ad libitum throughout the experiment. At the end of this study (35 and 42 days for the two-spotted and house crickets, respectively), all crickets were harvested, rinsed in tap water, and boiled in water for 5 min. During the rearing and harvesting processes, samples were collected from various potential contamination points for bacteria, including E. coli and Salmonella spp. There were samples of the initial input (feed, drinking water, and staff hands), rearing environment (water pipe, crate wall, living cartons, frass, and cricket surface), and harvesting crickets (harvested, washed, and boiled crickets), with a 2-week sampling interval, except for the last round of sampling for the two-spotted crickets. Subsequently, all samples were submitted to isolate and identify contaminated bacteria. The samples from the last round of sampling for both kinds of crickets were submitted to quantify the level of contamination for E. coli and Salmonella spp., including antimicrobial resistance by the disk diffusion method for the positive isolate. The results showed that bacterial contamination was found in the rearing of both cricket species, primarily involving Klebsiella spp. and Enterobacter spp., mainly found in prepared drinking water and the water pipes of drinking water supply equipment, which are potential sources of contamination with cricket frass. E. coli was found in 4.8% and 4.3% of the two-spotted and house crickets, respectively, while no presence of Salmonella spp. was detected in any submitted samples. The quantification of E. coli and Salmonella spp. indicated E. coli contamination near the water pipe and the frass of two-spotted crickets, but Salmonella spp. was undetectable in both two-spotted and house crickets. The antimicrobial resistance of isolated E. coli mainly involved penicillin G, amoxicillin, ampicillin, erythromycin, lincomycin, and tiamulin. Thus, good farm management with proper sanitation practices (such as cleaning and keeping the environment dry), as well as boiling crickets during the harvesting process, may help ensure the safety of edible cricket production.

Characterization of mAbs against Klebsiella pneumoniae type 3 fimbriae isolated in a target-independent phage display campaign

We used phage display, antibody engineering, and high-throughput assays to identify antibody-accessible targets of Klebsiella pneumoniae. We report the discovery of monoclonal antibodies (mAbs) binding to type 3 fimbrial proteins, including MrkA. We found that anti-MrkA mAbs were cross-reactive to a diverse panel of K. pneumoniae clinical isolates, representing different O-serotypes. mAbs binding to MrkA have previously been described and have been shown to provide prophylactic protection, although only modest protection when dosed therapeutically in vivo in a murine lung infection model. Here, we used a combination of binding and opsonophagocytic killing studies using a high-content imaging platform to provide a possible explanation for the modest therapeutic efficacy in vivo reported in that model. Our work shows that expression of K. pneumoniae type 3 fimbriae in in vitro culture is not homogenous within a bacterial population. Instead, sub-populations of bacteria that do, and do not, express type 3 fimbriae exist. In a high-content opsonophagocytic killing assay, we showed that MrkA-targeting antibodies initially promote killing by macrophages; however, over time, this effect is diminished. We hypothesize the reason for this is that bacteria not expressing MrkA can evade opsonophagocytosis. Our data support the fact that MrkA is a conserved, immunodominant protein that is antibody accessible on the surface of K. pneumoniae and suggest that additional studies should evaluate the potential of using anti-MrkA antibodies in different stages of K. pneumoniae infection (different sites in the body) as well as against K. pneumoniae biofilms in the body during infection and associated with medical devices.IMPORTANCEThere is an unmet, urgent need for the development of novel antimicrobial therapies for the treatment of Klebsiella pneumoniae infections. We describe the use of phage display, antibody engineering, and high-throughput assays to identify antibody-accessible targets of K. pneumoniae. We discovered monoclonal antibodies (mAbs) binding to the type 3 fimbrial protein MrkA. The anti-MrkA mAbs were found to be highly cross-reactive, binding to all K. pneumoniae strains tested from a diverse panel of clinical isolates, and were active in an opsonophagocytic killing assay at pM concentrations. MrkA is important for biofilm formation; thus, our data support further exploration of the use of anti-MrkA antibodies for preventing and/or controlling K. pneumoniae in biofilms and during infection.

A rapid and ultra-sensitive dual readout platform for Klebsiella pneumoniae detection based on RPA-CRISPR/Cas12a

The bacterium Klebsiella pneumoniae (Kp) was the primary pathogen of hospital-acquired infection, but the current detection method could not rapidly and conveniently identify Kp. Recombinase polymerase amplification (RPA) was a fast and convenient isothermal amplification technology, and the clustered regularly interspaced short palindromic repeats (CRISPR) system could rapidly amplify the signal of RPA and improve its limit of detection (LOD). In this study, we designed three pairs of RPA primers for the rcsA gene of Kp, amplified the RPA signal through single-strand DNA reporter cleavage by CRISPR/Cas12a, and finally analyzed the cleavage signal using fluorescence detection (FD) and lateral flow test strips (LFTS). Our results indicated that the RPA-CRISPR/Cas12a platform could specifically identify Kp from eleven common clinical pathogens. The LOD of FD and LFTS were 1 fg/μL and 10 fg/μL, respectively. In clinical sample testing, the RPA-CRISPR/Cas12a platform was consistent with the culture method and qPCR method, and its sensitivity and specificity were 100% (16/16) and 100% (9/9), respectively. With the advantages of detection speed, simplicity, and accuracy, the RPA-CRISPR/Cas12a platform was expected to be a convenient tool for the early clinical detection of Kp.

Urinary Tract Infections with Carbapenem-Resistant Klebsiella pneumoniae in a Urology Clinic-A Case-Control Study

BACKGROUND

The aim of our study was to analyze the factors associated with the increased risk of urinary tract infection (UTI) with carbapenem-resistant (CR) Klebsiella pneumoniae (Kpn) and the antibiotic resistance spectrum of the strains in patients. As secondary objectives, we elaborated the profile of these patients and the incidence of different types of carbapenemases.

METHODS

We conducted a retrospective case-control study in which we compared a group of 62 patients with urinary tract infections with CR Kpn with a control group consisting of 136 patients with urinary tract infections with multidrug-resistant (MDR), but carbapenem-sensitive (CS), Kpn, who were hospitalized between 1 January 2022 and 31 March 2024.

RESULTS

Compared to patients with urinary tract infections with CS Kpn, patients with urinary tract infections with CR Kpn were preponderant in rural areas (62.9% vs. 47.1%, p = 0.038) and more frequently had an upper urinary tract infection (69.4% vs. 36.8%, p < 0.01). Among the risk factors examined, patients in the study group had a higher presence of urinary catheters inserted for up to one month (50% vs. 34.6%, p = 0.03), rate of hospitalization in the last 180 days (96.8% vs. 69.9%, p < 0.01) and incidence of antibiotic therapy in the last 180 days (100% vs. 64.7%, p < 0.01). They also had a higher rate of carbapenem treatment in the last 180 days (8.1% vs. 0%, p < 0.01). Patients in the study group had a broader spectrum of resistance to all antibiotics tested (p < 0.01), with the exception of sulfamethoxazole-trimethoprim, where the resistance rate was similar in both groups (80.6% vs. 67.6%, p = 0.059). In the multivariate analysis, transfer from other hospitals (OR = 3.51, 95% and CI: 1.430-8.629) and treatment with carbapenems in the last 180 days (OR = 11.779 and 95% CI: 1.274-108.952) were factors associated with an increased risk of disease compared to the control group. The presence of carbapenemases was observed in all patients with CR Kpn, in the order of frequency New Delhi metallo-ß-lactamase (NDM) (52.2%), Klebsiella pneumoniae carbapenemase (KPC) (32.6%), and carbapenem-hydrolyzing oxacillinase (Oxa-48) (15.2%).

CONCLUSIONS

The environment of origin and previous treatment with carbapenems appear to be the factors associated with an increased risk of urinary tract infection with CR Kpn compared to patients with urinary tract infections with CS Kpn. CR Kpn exhibits a broad spectrum of antibiotic resistance, among which is resistance to carbapenem antibiotics.

Investigation of genotyping and phenotyping characteristics of carbapenem-resistant Klebsiella pneumoniae isolates

Klebsiella pneumoniae (K. pneumoniae) is a major cause of healthcare-associated infections and plays a prominent role in the widespread antibiotic resistance crisis. Accurate identification of carbapenemases is essential to facilitate effective antibiotic treatment and reduce transmission of K. pneumoniae. This study aimed to detect carbapenemase production in carbapenem-resistant K. pneumoniae strains using phenotypic and genotypic methods. A total of 67 carbapenem-resistant K. pneumoniae strains obtained from various clinical samples were utilized for identification and antimicrobial susceptibility by the Vitek 2 Compact system (Biomerieux, France). Carbapenemase production was determined by using the Polymerase chain reaction, Blue-carba test (BCT) and Carbapenem inactivation method (CIM). Out of the isolates, 59 (88.1%) were positive bla OXA-48, 16 (23.9%) bla IMP, and five (7.5%) were positive bla NDM. No bla KPC genes were detected. The CIM identified 62 (92.5%), BCT identified 63 (94%) of PCR-positive isolates. The sensitivity and specificity of the BCT and the CIM were determined to be 96.7%, 40%, and 96.7%, 25% respectively. The bla OXA-48 gene was found to be the most prevalent in K. pneumoniae isolates. Early identification of carbapenem resistance plays a vital role in designing effective infection control strategies and mitigating the emergence and transmission of carbapenem resistance, thus reducing healthcare-associated infections.

Atypical facial pustular folliculitis by Klebsiella pneumoniae: a case report

Rarely, the gram-negative bacteria Klebsiella pneumoniae causes skin infections that are frequently challenging to identify. We present a case of an atypical presentation of this specific disease in terms of its site, lack of risk factors, and length of illness.

Bacteriophage cocktail shows no toxicity and improves the survival of Galleria mellonella infected with Klebsiella spp

Klebsiella spp. are causative agents of healthcare-associated infections in patients who are immunocompromised and use medical devices. The antibiotic resistance crisis has led to an increase in infections caused by these bacteria, which can develop into potentially life-threatening illnesses if not treated swiftly and effectively. Thus, new treatment options for Klebsiella are urgently required. Phage therapy can offer an alternative to ineffective antibiotic treatments for antibiotic-resistant bacteria infections. The aim of the present study was to produce a safe and effective phage cocktail treatment against Klebsiella pneumoniae and Klebsiella oxytoca, both in liquid in vitro culture and an in vivo Galleria mellonella infection model. The phage cocktail was significantly more effective at killing K. pneumoniae and K. oxytoca strains compared with monophage treatments. Preliminary phage cocktail safety was demonstrated through application in the in vivo G. mellonella model: where the phage cocktail induced no toxic side effects in G. mellonella. In addition, the phage cocktail significantly improved the survival of G. mellonella when administered as a prophylactic treatment, compared with controls. In conclusion, our phage cocktail was demonstrated to be safe and effective against Klebsiella spp. in the G. mellonella infection model. This provides a strong case for future treatment for Klebsiella infections, either as an alternative or adjunct to antibiotics.IMPORTANCEKlebsiella infections are a concern in individuals who are immunocompromised and are becoming increasingly difficult to treat with antibiotics due to their drug-resistant properties. Bacteriophage is one potential alternative therapy that could be used to tackle these infections. The present study describes the design of a non-toxic phage cocktail that improved the survival of Galleria mellonella infected with Klebsiella. This phage cocktail demonstrates potential for the safe and effective treatment of Klebsiella infections, as an adjunct or alternative to antibiotics.

Lethal Gram-negative sepsis in healthy pigs during anaesthesia with contaminated propofol

Two healthy Landrace pigs anaesthetized with propofol suffered rapid onset of fatal sepsis. Clinical signs included severe arterial hypotension, loss of peripheral oxygenation, low end-tidal CO2, clinical onset of pulmonary oedema and cardiac dysfunction. Gross and histopathological examination revealed loss of vascular integrity with severe lung oedema and congestion, haemorrhages in several organs and fluid leakage into body cavities. Large numbers of Gram-negative bacteria, primarily Klebsiella sp., were present in the anaesthetic infusion containing propofol and were also cultured from internal organs of both pigs. The propofol was likely contaminated by bacteria after inappropriate handling and storage in the operating room. This report illustrates the potential for severe nosocomial infection when applying propofol in animals and humans and may serve as a reminder of the importance of strict aseptic practice in general, and specifically in the handling of this anaesthetic agent.

ESKAPE pathogens: antimicrobial resistance, epidemiology, clinical impact and therapeutics

The rise of antibiotic resistance and a dwindling antimicrobial pipeline have been recognized as emerging threats to public health. The ESKAPE pathogens - Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp. - were initially identified as critical multidrug-resistant bacteria for which effective therapies were rapidly needed. Now, entering the third decade of the twenty-first century, and despite the introduction of several new antibiotics and antibiotic adjuvants, such as novel β-lactamase inhibitors, these organisms continue to represent major therapeutic challenges. These bacteria share several key biological features, including adaptations for survival in the modern health-care setting, diverse methods for acquiring resistance determinants and the dissemination of successful high-risk clones around the world. With the advent of next-generation sequencing, novel tools to track and combat the spread of these organisms have rapidly evolved, as well as renewed interest in non-traditional antibiotic approaches. In this Review, we explore the current epidemiology and clinical impact of this important group of bacterial pathogens and discuss relevant mechanisms of resistance to recently introduced antibiotics that affect their use in clinical settings. Furthermore, we discuss emerging therapeutic strategies needed for effective patient care in the era of widespread antimicrobial resistance.

Bacterial septicemia and herpesvirus infection in Antarctic fur seals (Arctocephalus gazella) stranded in the São Paulo coast, Brazil

In August 2021, two juvenile male Antarctic fur seals (Arctocephalus gazella) stranded in the southeastern Brazilian coast and were referred to rehabilitation centers. The animals presented increased body temperature, prostration, respiratory distress and despite treatment died. A necropsy following a standardized protocol was performed, and formalin-fixed tissues were processed for microscopic examination. Samples were screened for morbillivirus, herpesvirus, and Brucella spp. by molecular analyses (PCR, RT-PCR). Bacteriological culture was performed in samples collected from the lungs, trachea, and lymph nodes of both cases. The main histopathologic findings were of infectious nature, including multifocal necrotizing and fibrinous mixed interstitial pneumonia, bronchiolitis, and bronchitis, with intralesional myriad bacteria associated with vascular fibrinoid necrosis. Pseudomonas aeruginosa was isolated from tracheal and lung swabs of Case 1, and Klebsiella oxytoca was found in nostril swabs, tracheobronchial lymph nodes, and lung of Case 2. Gammaherpesvirus infection was detected in both cases, and the sequences retrieved were classified into the genus Percavirus. All tested samples were PCR-negative for Brucella spp. and morbillivirus. We hypothesize that the deficient immunological status in association with starvation predisposed the reactivation of herpesvirus and secondary bacterial co-infections. To the authors' knowledge, this is the first molecular detection of herpesvirus in an Antarctic pinniped. These findings reinforce that Otariid gammaherpesvirus circulating in the Southern Hemisphere are likely endemic in the Arctocephalus genus. This report contributes to the current knowledge of health aspects affecting wild pinnipeds, especially in the poorly studied Antarctic species.

Central Venous Catheter Misplacement Into Pleural Cavity Causing Hypertensive Pleural Effusion: A Case Report

Central venous catheter (CVC) insertion is a routine procedure in the management of critically ill patients. We report a clinical case of inadvertent placement of an internal jugular vein CVC into the right pleural cavity, despite employing clinical and imaging-based techniques to ensure proper catheter positioning. Infusion of fluids and vasopressors through this misplaced catheter led to hypertensive pleural effusion and subsequent cardiorespiratory arrest. Return of spontaneous circulation was achieved after two cycles of cardiopulmonary resuscitation. While multiple imaging modalities are recommended for confirming appropriate CVC placement, each method has inherent limitations. This case highlights the imperative need for a high index of suspicion to avert such complications and pretends to review some of each method's limitations.

Outbreaks by Klebsiella oxytoca in neonatal intensive care units: Analysis of an outbreak in a tertiary hospital and systematic review

OBJECTIVE

Klebsiella oxytoca can cause nosocomial infections, affecting vulnerable newborns. There are few studies describing nosocomial outbreaks in the neonatal intensive care units (NICU). In this study, a systematic review of the literature was carried out to know the main characteristics of these outbreaks and the evolution of one is described.

METHODS

We conducted a systematic review in the Medline database up to July 2022, and present a descriptive study of an outbreak with 21 episodes in the NICU of a tertiary hospital, between September 2021 and January 2022.

RESULTS

9 articles met the inclusion criteria. The duration of outbreaks was found to be variable, of which 4 (44.4%) lasted for a year or more. Colonization (69%) was more frequent than infections (31%) and the mortality rate was 22.4%. In studies describing sources, the most frequent was the environmental origin (57.1%). In our outbreak there were 15 colonizations and 6 infections. The infections were mild conjunctivitis without sequelae. Molecular typing analysis made it possible to detect 4 different clusters.

CONCLUSIONS

There is an important variability in the evolution and results of the published outbreaks, highlighting a greater number of colonized, use of PFGE (pulsed-field gel electrophoresis) techniques for molecular typing and implementation of control measures. Finally, we describe an outbreak in which 21 neonates were affected with mild infections, resolved without sequelae and whose control measures were effective.

Hand contamination and hand hygiene knowledge and practices among commercial transport users after the SARS-CoV-2 virus (COVID-19) scare, Enugu State, Nigeria

Contaminated hands are one of the most common modes of microorganism transmission that are responsible for many associated infections in healthcare, food industries, and public places such as transportation parks. Public health approaches during COVID-19 pandemic have shown that hand hygiene practices and associated knowledge are critical measure to control the spread of infectious agent. Hence, assessment of commercial transport users' knowledge, belief and practices on hand hygiene, and potential contamination with infectious agents which is the aim of the study, aligns with general health concern of quantifying contamination risk levels to predict disease outbreaks. This study utilized a randomized sampling approach to select 10 frequently used commercial parks within two districts in the State: Enugu and Nsukka. The parameters analysed include a cross-sectional questionnaire survey, hand swab and hand washed samples collected from dominant hand of participants. A total of 600 participants responded to the questionnaire survey, while 100 participants' hand swabs were examined for microbial contamination. This study recorded a high prevalence of fungal (90.0%) and bacterial (87.0%) species; 20 species of fungus were identified with prevalence range of 1% to 14%; 21 bacterial species were isolated with prevalence range of 1% to 16%. These species were identified as either opportunistic, non-invasive, or pathogenic, which may constitute a health concern amongst immunocompromised individuals within the population. Aspergillus spp. (14%), was the most common fungal species that was exclusively found amongst Nsukka commercial users, while E. coli was the most prevalent isolated bacterial species amongst Nsukka (12%) and Enugu (20%) commercial park users. Prevalence of fungal contamination in Nsukka (94.0%; 47/50) and Enugu (86.0%; 43/50) were both high. Prevalence of bacterial contamination was higher in Enugu than Nsukka but not significantly (47[94.0%] vs. 40[80.0%], p = 0.583). A greater number of participants (99.3%) were aware of the importance of hand hygiene, however with low compliance rate aside "after using the toilet" (80%) and "before eating" (90%), other relevant hand washing and sanitizing practices were considered less important. With these observations, we can emphatically say that despite the COVID-19 scare, commercial park users within the sampled population do not efficiently practice quality hand wash and hygiene measures, hence, risking the widespread of infectious agents in situation of disease outbreak or among immunocompromised individuals.

Antibiotic Resistance in Enterococci and Enterobacteriaceae from Laboratory-Reared Fresh Mealworm Larvae (Tenebrio molitor L.) and Their Frass

The occurrence of antibiotic-resistant bacteria in foodstuff involves a human health risk. Edible insects are a precious resource; however, their consumption raises food safety issues. In this study, the occurrence of antibiotic resistant bacteria in laboratory-reared fresh mealworm larvae (Tenebrio molitor L.) and frass was assessed. Antibiotics were not used during the rearing. Enterobacteriaceae and enterococci were isolated from 17 larvae and eight frass samples. In total, 62 and 69 isolates presumed to belong to Enterobacteriaceae and Enterococcus spp., respectively, were obtained and tested for antibiotic susceptibility via disk diffusion. Based on the results, isolates were grouped, and representative resistant isolates were identified at species level through 16S rRNA gene sequencing. For enterococci resistance, percentages higher than 15% were observed for vancomycin and quinupristin-dalfopristin, whereas Enterobacteriaceae resistance higher than 25% was found against cefoxitin, ampicillin, and amoxicillin-clavulanic acid. Based on the species identification, the observed resistances seemed to be intrinsic both for enterococci and Enterobacteriaceae, except for some β-lactams resistance in Shigella boydii (cefoxitin and aztreonam). These could be due to transferable genetic elements. This study suggests the need for further investigations to clarify the role of edible insects in the spreading of antibiotic resistance determinants through the food chain.

Hypervirulent Klebsiella pneumoniae in a South African tertiary hospital-Clinical profile, genetic determinants, and virulence in Caenorhabditis elegans

Introduction

A distinct strain of Klebsiella pneumoniae (K. pneumoniae) referred to as hypervirulent (hvKp) is associated with invasive infections such as pyogenic liver abscess in young and healthy individuals. In South Africa, limited information about the prevalence and virulence of this hvKp strain is available. The aim of this study was to determine the prevalence of hvKp and virulence-associated factors in K. pneumoniae isolates from one of the largest tertiary hospitals in a South African province.

Methods

A total of 74 K. pneumoniae isolates were received from Pelonomi Tertiary Hospital National Health Laboratory Service (NHLS), Bloemfontein. Virulence-associated genes (rmpA, capsule serotype K1/K2, iroB and irp2) were screened using Polymerase Chain Reaction (PCR). The iutA (aerobactin transporter) gene was used as a primary biomarker of hvKp. The extracted DNAs were sequenced using the next-generation sequencing pipeline and the curated sequences were used for phylogeny analyses using appropriate bioinformatic tools. The virulence of hvKp vs. classical Klebsiella pneumoniae (cKp) was investigated using the Caenorhabditis elegans nematode model.

Results

Nine (12.2%) isolates were identified as hvKp. Moreover, hvKp was significantly (p < 0.05) more virulent in vivo in Caenorhabditis elegans relative to cKp. The virulence-associated genes [rmpA, iroB, hypermucoviscous phenotype (hmv) phenotype and capsule K1/K2] were significantly (p < 0.05) associated with hvKp. A homology search of the curated sequences revealed a high percentage of identity between 99.8 and 100% with other homologous iutA gene sequences of other hvKp in the GenBank.

Conclusion

Findings from this study confirm the presence of hvKp in a large tertiary hospital in central South Africa. However, the low prevalence and mild to moderate clinical presentation of infected patients suggest a marginal threat to public health. Further studies in different settings are required to establish the true potential impact of hvKp in developing countries.

The Increased Prevalence of rmpA Gene in Klebsiella pneumoniae Isolates Coharboring blaNDM and blaOXA-48-like Genes

The emergence of carbapenemase-producing Klebsiella pneumoniae poses a substantial risk to public health. It is essential to comprehend the influence of carbapenemase on the virulence characteristics of K. pneumoniae in order to devise successful strategies for combating these infections. In this study, we explored the distribution disparity of virulence determinants between carbapenemase-producing (CP-Kp, n = 52) and carbapenemase-nonproducing (CN-Kp, n = 43) isolates. The presence of carbapenemases was detected via the modified carbapenem inactivation method and confirmed by PCR. The New Delhi metallo-β-lactamase (blaNDM) and Oxacillinase-48-like (blaOXA-48-like) genes were the most prevalent (94.23% and 76.92%, respectively) in CP-Kp isolates. Coexistence of blaNDM and blaOXA-48-like was observed in 71.15% of isolates, whereas 5.77% coharbored blaNDM and blaKPC. PCR analysis revealed the presence of several virulence genes, including adhesins (fimH, 92.63%, mrkD, 97.89%), capsule-associated virulence (uge, 90.53%), the K2 capsule serotype (k2, 6.32%), the iron acquisition system (kfu, 23.16%), and the regulator of mucoid phenotype (rmpA, 28.42%). A significantly higher prevalence of rmpA was detected in the CP-Kp compared with the CN-Kp (24/52 vs. 3/43, p < 0.0001), indicating a potential association between rmpA and carbapenemase acquisition. In addition, the majority of rmpA (22/24) positive isolates in the CP-Kp isolates coharbored blaNDM and either blaOXA-48-like or blaKPC.

The correlation between intestinal colonization and infection of carbapenem-resistant Klebsiella pneumoniae: A systematic review

As a widely spread Gram-negative bacteria, Klebsiella pneumoniae (KP) mainly causes acquired infections in hospitals, such as lung infections, urinary tract infections, and bloodstream infections. In recent years, the number of multidrug-resistant KP strains has increased dramatically, posing a great threat to human health. Carbapenem-resistant KP (CRKP) can be colonized in human body, especially in gastrointestinal tract, and some colonized patients can be infected during hospitalization, among which invasive operation, underlying disease, admission to intensive care unit, antibiotic use, severity of the primary disease, advanced age, operation, coma, and renal failure are common risk factors for secondary infection. Active screening and preventive measures can effectively prevent the occurrence of CRKP infection. Based on the epidemiological status, this study aims to discuss the correlation between colonization and secondary infection induced by CRKP and risk factors for their happening and provide some reference for nosocomial infection prevention and control.

Combination Therapy for OXA-48 Carbapenemase-Producing Klebsiella Pneumoniae Bloodstream Infections in Premature Infant: A Case Report and Literature Review

The prevalence of carbapenem-resistant Klebsiella pneumoniae (CRKP) has been increasing in recent years. Chinese Infectious Disease Surveillance of Pediatrics (ISPED) showed that in 2022, its resistance rate to meropenem was 18.5%. However, there is limited data available on the treatment of CRKP infection in neonates. In this study, we present a case involving a premature infant infected with OXA-48-producing Klebsiella pneumoniae. The combined susceptibility test revealed a significant synergistic effect between ceftazidime-avibactam(CAZ-AVI), and aztreonam(ATM). The infection was successfully treated with a combination of CAZ-AVI, ATM, and fosfomycin. This case represents the first reported instance of sepsis in a premature infant caused by OXA-48-producing Klebsiella pneumoniae in China. The objective of our study is to evaluate the effectiveness and safety of combination therapy in treating CRKP infections in premature infants. We hope that the findings of this study will provide valuable insights for clinicians in their treatment approach.

Epidemiological, Virulence, and Antibiotic Resistance Analysis of Klebsiella pneumoniae, a Major Source of Threat to Livestock and Poultry in Some Regions of Xinjiang, China

Klebsiella pneumoniae (K. pneumoniae) is recognized as a zoonotic pathogen with an increasing threat to livestock and poultry. However, research on K. pneumoniae of animal origin remains limited. To address the gap, a comprehensive investigation was carried out by collecting a total of 311 samples from the farms of four animal species (dairy cow, chicken, sheep, and pig) in selected areas of Xinjiang, China. Isolates were identified by khe gene amplification and 16S rRNA gene sequencing. Genotyping of K. pneumonia isolates was performed using wzi typing and multilocus sequence typing (MLST). PCR was employed to identify virulence and resistance genes. An antibiotic susceptibility test was conducted using the Kirby-Bauer method. The findings revealed an isolation of 62 K. pneumoniae strains, with an average isolation rate of 19.94%, with the highest proportion originating from cattle sources (33.33%). Over 85.00% of these isolates harbored six virulence genes (wabG, uge, fimH, markD, entB, and ureA); while more than 75.00% of isolates possessed four resistance genes (blaTEM, blaSHV, oqxA, and gyrA). All isolates exhibited complete resistance to ampicillin and demonstrated substantial resistance to sulfisoxazole, amoxicillin/clavulanic acid, and enrofloxacin, with an antibiotic resistance rate of more than 50%. Furthermore, 48.39% (30/62) of isolates were classified as multidrug-resistant (MDR) strains, with a significantly higher isolation rate observed in the swine farms (66.67%) compared to other farms. Genetic characterization revealed the classification of the 62 isolates into 30 distinct wzi allele types or 35 different sequence types (STs). Notably, we identified K. pneumoniae strains of dairy and swine origin belonging to the same ST42 and wzi33-KL64 types, as well as strains of dairy and chicken origin belonging to the same wzi31-KL31-K31 type. These findings emphasize the widespread occurrence of drug-resistant K. pneumoniae across diverse animal sources in Xinjiang, underscoring the high prevalence of multidrug resistance. Additionally, our results suggest the potential for animal-to-animal transmission of K. pneumoniae and there was a correlation between virulence genes and antibiotic resistance genes. Moreover, the current study provides valuable data on the prevalence, antibiotic resistance, and genetic diversity of K. pneumoniae originating from diverse animal sources in Xinjiang, China.

Proteome analysis, genetic characterization, and antibiotic resistance patterns of Klebsiella pneumoniae clinical isolates

Klebsiella pneumoniae (K. pneumoniae) is a member of the ESKAPE group and is responsible for severe community and healthcare-associated infections. Certain Klebsiella species have very similar phenotypes, which presents a challenge in identifying K. pneumoniae. Multidrug-resistant K. pneumoniae is also a serious global problem that needs to be addressed. A total of 190 isolates were isolated from urine (n = 69), respiratory (n = 52), wound (n = 48) and blood (n = 21) samples collected from various hospitals in the Al-Qassim, Saudi Arabia, between March 2021 and October 2022. Our study aimed to rapidly and accurately detect K. pneumoniae using the Peptide Mass Fingerprinting (PMF) technique, confirmed by real-time PCR. Additionally, screening for antibiotic susceptibility and resistance was conducted. The primary methods for identifying K. pneumoniae isolates were culture, Gram staining, and the Vitek® 2 ID Compact system. An automated MALDI Biotyper (MBT) instrument was used for proteome identification, which was subsequently confirmed using SYBR green real-time polymerase chain reaction (real-time PCR) and microfluidic electrophoresis assays. Vitek® 2 AST-GN66 cards were utilized to evaluate the antimicrobial sensitivity of K. pneumoniae isolates. According to our results, Vitek® 2 Compact accurately identified 178 out of 190 (93.68%) K. pneumoniae isolates, while the PMF technique correctly detected 188 out of 190 (98.95%) isolates with a score value of 2.00 or higher. Principal component analysis was conducted using MBT Compass software to classify K. pneumoniae isolates based on their structure. Based on the analysis of the single peak intensities generated by MBT, the highest peak values were found at 3444, 5022, 5525, 6847, and 7537 m/z. K. pneumoniae gene testing confirmed the PMF results, with 90.53% detecting entrobactin, 70% detecting 16 S rRNA, and 32.63% detecting ferric iron uptake. The resistance of the K. pneumoniae isolates to antibiotics was as follows: 64.75% for cefazolin, 62.63% for trimethoprim/sulfamethoxazole, 59.45% for ampicillin, 58.42% for cefoxitin, 57.37% for ceftriaxone, 53.68% for cefepime, 52.11% for ampicillin-sulbactam, 50.53% for ceftazidime, 52.11% for ertapenem, and 49.47% for imipenem. Based on the results of the double-disk synergy test, 93 out of 190 (48.95%) K. pneumoniae isolates were extended-spectrum beta-lactamase. In conclusion, PMF is a powerful analytical technique used to identify K. pneumoniae isolates from clinical samples based on their proteomic characteristics. K. pneumoniae isolates have shown increasing resistance to antibiotics from different classes, including carbapenem, which poses a significant threat to human health as these infections may become difficult to treat.

Molecular characterization of hypermucoviscous carbapenemase-encoding Klebsiella pneumoniae isolates from an Egyptian hospital

This study aimed to screen antibiotic resistance and virulence genes in carbapenem-resistant hypermucoviscous Klebsiella pneumoniae isolates from an Egyptian hospital. Among 38 previously confirmed carbapenem-nonsusceptible K. pneumoniae isolates, a string test identified three isolates as positive for hypermucoviscosity. Phenotypic characterization and molecular detection of carbapenemase- and virulence-encoding genes were performed. PCR-based multilocus sequence typing and phylogenetics were used to determine the clonality and global epidemiology of the strains. The coexistence of virulence and resistance genes in the isolates was analyzed statistically using a chi-square test. Three isolates showed the presence of carbapenemase-encoding genes (blaNDM, blaVIM, and blaIMP), adhesion genes (fim-H-1 and mrkD), and siderophore genes (entB); the isolates belonged to sequence types (STs) 101, 1310, and 1626. The relatedness between these sequence types and the sequence types of globally detected hypermucoviscous K. pneumoniae that also harbor carbapenemases was determined. Our analysis showed that the resistance and virulence profiles were not homogenous. Phylogenetically, different clones clustered together. There was no significant association between the presence of resistance and virulence genes in the isolates. There is a need for periodic surveillance of the healthcare settings in Egypt and globally to understand the true epidemiology of carbapenem-resistant, hypermucoviscous K. pneumoniae.

A rational designed multi-epitope vaccine elicited robust protective efficacy against Klebsiella pneumoniae lung infection

BACKGROUND

The emergence of drug-resistant strains of Klebsiella pneumoniae (K. pneumoniae) has become a significant challenge in the field of infectious diseases, posing an urgent need for the development of highly protective vaccines against this pathogen.

METHODS AND RESULTS

In this study, we identified three immunogenic extracellular loops based on the structure of five candidate antigens using sera from K. pneumoniae infected mice. The sequences of these loops were linked to the C-terminal of an alpha-hemolysin mutant (mHla) from Staphylococcus aureus to generate a heptamer, termed mHla-EpiVac. In vivo studies confirmed that fusion with mHla significantly augmented the immunogenicity of EpiVac, and it elicited both humoral and cellular immune responses in mice, which could be further enhanced by formulation with aluminum adjuvant. Furthermore, immunization with mHla-EpiVac demonstrated enhanced protective efficacy against K. pneumoniae channeling compared to EpiVac alone, resulting in reduced bacterial burden, secretion of inflammatory factors, histopathology and lung injury. Moreover, mHla fusion facilitated antigen uptake by mouse bone marrow-derived cells (BMDCs) and provided sustained activation of these cells.

CONCLUSIONS

These findings suggest that mHla-EpiVac is a promising vaccine candidate against K. pneumoniae, and further validate the potential of mHla as a versatile carrier protein and adjuvant for antigen design.

Brain endothelial GSDMD activation mediates inflammatory BBB breakdown

The blood-brain barrier (BBB) protects the central nervous system from infections or harmful substances1; its impairment can lead to or exacerbate various diseases of the central nervous system2-4. However, the mechanisms of BBB disruption during infection and inflammatory conditions5,6 remain poorly defined. Here we find that activation of the pore-forming protein GSDMD by the cytosolic lipopolysaccharide (LPS) sensor caspase-11 (refs. 7-9), but not by TLR4-induced cytokines, mediates BBB breakdown in response to circulating LPS or during LPS-induced sepsis. Mice deficient in the LBP-CD14 LPS transfer and internalization pathway10-12 resist BBB disruption. Single-cell RNA-sequencing analysis reveals that brain endothelial cells (bECs), which express high levels of GSDMD, have a prominent response to circulating LPS. LPS acting on bECs primes Casp11 and Cd14 expression and induces GSDMD-mediated plasma membrane permeabilization and pyroptosis in vitro and in mice. Electron microscopy shows that this features ultrastructural changes in the disrupted BBB, including pyroptotic endothelia, abnormal appearance of tight junctions and vasculature detachment from the basement membrane. Comprehensive mouse genetic analyses, combined with a bEC-targeting adeno-associated virus system, establish that GSDMD activation in bECs underlies BBB disruption by LPS. Delivery of active GSDMD into bECs bypasses LPS stimulation and opens the BBB. In CASP4-humanized mice, Gram-negative Klebsiella pneumoniae infection disrupts the BBB; this is blocked by expression of a GSDMD-neutralizing nanobody in bECs. Our findings outline a mechanism for inflammatory BBB breakdown, and suggest potential therapies for diseases of the central nervous system associated with BBB impairment.

Opportunistic Pathogens in Drinking Water Distribution Systems-A Review

In contrast to "frank" pathogens, like Salmonella entrocolitica, Shigella dysenteriae, and Vibrio cholerae, that always have a probability of disease, "opportunistic" pathogens are organisms that cause an infectious disease in a host with a weakened immune system and rarely in a healthy host. Historically, drinking water treatment has focused on control of frank pathogens, particularly those from human or animal sources (like Giardia lamblia, Cryptosporidium parvum, or Hepatitis A virus), but in recent years outbreaks from drinking water have increasingly been due to opportunistic pathogens. Characteristics of opportunistic pathogens that make them problematic for water treatment include: (1) they are normally present in aquatic environments, (2) they grow in biofilms that protect the bacteria from disinfectants, and (3) under appropriate conditions in drinking water systems (e.g., warm water, stagnation, low disinfectant levels, etc.), these bacteria can amplify to levels that can pose a public health risk. The three most common opportunistic pathogens in drinking water systems are Legionella pneumophila, Mycobacterium avium, and Pseudomonas aeruginosa. This report focuses on these organisms to provide information on their public health risk, occurrence in drinking water systems, susceptibility to various disinfectants, and other operational practices (like flushing and cleaning of pipes and storage tanks). In addition, information is provided on a group of nine other opportunistic pathogens that are less commonly found in drinking water systems, including Aeromonas hydrophila, Klebsiella pneumoniae, Serratia marcescens, Burkholderia pseudomallei, Acinetobacter baumannii, Stenotrophomonas maltophilia, Arcobacter butzleri, and several free-living amoebae including Naegleria fowleri and species of Acanthamoeba. The public health risk for these microbes in drinking water is still unclear, but in most cases, efforts to manage Legionella, mycobacteria, and Pseudomonas risks will also be effective for these other opportunistic pathogens. The approach to managing opportunistic pathogens in drinking water supplies focuses on controlling the growth of these organisms. Many of these microbes are normal inhabitants in biofilms in water, so the attention is less on eliminating these organisms from entering the system and more on managing their occurrence and concentrations in the pipe network. With anticipated warming trends associated with climate change, the factors that drive the growth of opportunistic pathogens in drinking water systems will likely increase. It is important, therefore, to evaluate treatment barriers and management activities for control of opportunistic pathogen risks. Controls for primary treatment, particularly for turbidity management and disinfection, should be reviewed to ensure adequacy for opportunistic pathogen control. However, the major focus for the utility's opportunistic pathogen risk reduction plan is the management of biological activity and biofilms in the distribution system. Factors that influence the growth of microbes (primarily in biofilms) in the distribution system include, temperature, disinfectant type and concentration, nutrient levels (measured as AOC or BDOC), stagnation, flushing of pipes and cleaning of storage tank sediments, and corrosion control. Pressure management and distribution system integrity are also important to the microbial quality of water but are related more to the intrusion of contaminants into the distribution system rather than directly related to microbial growth. Summarizing the identified risk from drinking water, the availability and quality of disinfection data for treatment, and guidelines or standards for control showed that adequate information is best available for management of L. pneumophila. For L. pneumophila, the risk for this organism has been clearly established from drinking water, cases have increased worldwide, and it is one of the most identified causes of drinking water outbreaks. Water management best practices (e.g., maintenance of a disinfectant residual throughout the distribution system, flushing and cleaning of sediments in pipelines and storage tanks, among others) have been shown to be effective for control of L. pneumophila in water supplies. In addition, there are well documented management guidelines available for the control of the organism in drinking water distribution systems. By comparison, management of risks for Mycobacteria from water are less clear than for L. pneumophila. Treatment of M. avium is difficult due to its resistance to disinfection, the tendency to form clumps, and attachment to surfaces in biofilms. Additionally, there are no guidelines for management of M. avium in drinking water, and one risk assessment study suggested a low risk of infection. The role of tap water in the transmission of the other opportunistic pathogens is less clear and, in many cases, actions to manage L. pneumophila (e.g., maintenance of a disinfectant residual, flushing, cleaning of storage tanks, etc.) will also be beneficial in helping to manage these organisms as well.

Community-Acquired Solitary Brain Abscesses Caused by Hypervirulent Klebsiella pneumoniae in a Healthy Adult

A 42-year-old man was admitted to the emergency room complaining of fever and headache. His cerebrospinal fluid showed a cloudy appearance, and his white blood cell count was elevated at 2460/mm3, with a predominance of neutrophils (81%), and abnormal protein and glucose levels (510.7 mg/dL and 5 mg/dL, respectively). A lobulated lesion with rim enhancement, suggestive of abscess, was detected through magnetic resonance imaging. Klebsiella pneumoniae was detected in nasopharyngeal swab and blood cultures. The capsular serotype of K. pneumoniae was K2 and the sequence type determined by multilocus sequence typing was 23. The hypervirulent phenotype was associated with multiple virulent genes, including rmpA, rmpA2, entB, ybtS, kfu, iucA, iutA, iroB mrkD, allS, peg-344, peg-589, and peg-1631. After six weeks of receiving appropriate antibiotics and exhibiting clinical resolution of the brain abscesses, the patient was discharged. We present the first reported case of a healthy community-dwelling adult with solitary brain abscesses, and no other invasive abscesses, related to hypervirulent K. pneumoniae.

[Effect of intestinal nitrate on growth of Klebsiella pneumoniae and its regulatory mechanism]

OBJECTIVE

To explore the effect of intestinal nitrates on the growth of Klebsiella pneumoniae and its regulatory mechanisms.

METHODS

K. pneumoniae strains with nitrate reductase narG and narZ single or double gene knockout or with NarXL gene knockout were constructed and observed for both aerobic and anaerobic growth in the presence of KNO3 using an automated bacterial growth analyzer and a spectrophotometer, respectively. The mRNA expressions of narG and narZ in K. pneumoniae in anaerobic cultures in the presence of KNO3 and the effect of the binary regulatory system NarXL on their expresisons were detected using qRT-PCR. Electrophoretic mobility shift assays (EMSA) and MST analysis were performed to explore the specific regulatory mechanisms of NarXL in sensing and utilizing nitrates. Competitive experiments were conducted to examine anaerobic growth advantages of narG and narZ gene knockout strains of K. pneumoniae in the presence of KNO3.

RESULTS

The presence of KNO3 in anaerobic conditions, but not in aerobic conditions, promoted bacterial growth more effectively in the wild-type K. pneumoniae strain than in the narXL gene knockout strain. In anaerobic conditions, the narXL gene knockout strain showed significantly lowered mRNA expressions of narG and narZ (P < 0.0001). EMSA and MST experiments demonstrated that the NarXL regulator could directly bind to narG and narZ promoter regions. The wild-type K. pneumoniae strain in anaerobic cultures showed significantly increased expressions of narG and narZ mRNAs in the presence of KNO3 (P < 0.01), and narG gene knockout resulted in significantly attenuated anaerobic growth and competitive growth abilities of K. pneumoniae in the presence of KNO3 (P < 0.01).

CONCLUSION

The binary regulatory system NarXL of K. pneumoniae can sense changes in intestinal nitrate concentration and directly regulate the expression of nitrate reductase genes narG and narZ to promote bacterial growth.

Respiratory carriage of hypervirulent Klebsiella pneumoniae by indigenous populations of Malaysia

Klebsiella pneumoniae is a Gram-negative Enterobacteriaceae that is classified by the World Health Organisation (WHO) as a Priority One ESKAPE pathogen. South and Southeast Asian countries are regions where both healthcare associated infections (HAI) and community acquired infections (CAI) due to extended-spectrum β-lactamase (ESBL)-producing and carbapenem-resistant K. pneumoniae (CRKp) are of concern. As K. pneumoniae can also exist as a harmless commensal, the spread of resistance genotypes requires epidemiological vigilance. However there has been no significant study of carriage isolates from healthy individuals, particularly in Southeast Asia, and specially Malaysia. Here we describe the genomic analysis of respiratory isolates of K. pneumoniae obtained from Orang Ulu and Orang Asli communities in Malaysian Borneo and Peninsular Malaysia respectively. The majority of isolates were K. pneumoniae species complex (KpSC) 1 K. pneumoniae (n = 53, 89.8%). Four Klebsiella variicola subsp. variicola (KpSC3) and two Klebsiella quasipneumoniae subsp. similipneumoniae (KpSC4) were also found. It was discovered that 30.2% (n = 16) of the KpSC1 isolates were ST23, 11.3% (n = 6) were of ST65, 7.5% (n = 4) were ST13, and 13.2% (n = 7) were ST86. Only eight of the KpSC1 isolates encoded ESBL, but importantly not carbapenemase. Thirteen of the KpSC1 isolates carried yersiniabactin, colibactin and aerobactin, all of which harboured the rmpADC locus and are therefore characterised as hypervirulent. Co-carriage of multiple strains was minimal. In conclusion, most isolates were KpSC1, ST23, one of the most common sequence types and previously found in cases of K. pneumoniae infection. A proportion were hypervirulent (hvKp) however antibiotic resistance was low.

Deciphering the gastrointestinal carriage of Klebsiella pneumoniae

Bacterial infections pose a significant global health threat, accounting for an estimated 7.7 million deaths. Hospital outbreaks driven by multi-drug-resistant pathogens, notably Klebsiella pneumoniae (K. pneumoniae), are of grave concern. This opportunistic pathogen causes pneumonia, urinary tract infections, and bacteremia, particularly in immunocompromised individuals. The rise of hypervirulent K. pneumoniae adds complexity, as it increasingly infects healthy individuals. Recent epidemiological data suggest that asymptomatic gastrointestinal carriage serves as a reservoir for infections in the same individual and allows for host-to-host transmission via the fecal-oral route. This review focuses on K. pneumoniae's gastrointestinal colonization, delving into epidemiological evidence, current animal models, molecular colonization mechanisms, and the protective role of the resident gut microbiota. Moreover, the review sheds light on in vivo high-throughput approaches that have been crucial for identifying K. pneumoniae factors in gut colonization. This comprehensive exploration aims to enhance our understanding of K. pneumoniae gut pathogenesis, guiding future intervention and prevention strategies.

Structural and functional basis of bacteriophage K64-ORF41 depolymerase for capsular polysaccharide degradation of Klebsiella pneumoniae K64

Capsule polysaccharide is an important virulence factor of Klebsiella pneumoniae (K. pneumoniae), which protects bacteria against the host immune response. A promising therapeutic approach is using phage-derived depolymerases to degrade the capsular polysaccharide and expose and sensitize the bacteria to the host immune system. Here we determined the cryo-electron microscopy (cryo-EM) structures of a bacteriophage tail-spike protein against K. pneumoniae K64, ORF41 (K64-ORF41) and ORF41 in EDTA condition (K64-ORF41EDTA), at 2.37 Å and 2.50 Å resolution, respectively, for the first time. K64-ORF41 exists as a trimer and each protomer contains a β-helix domain including a right-handed parallel β-sheet helix fold capped at both ends, an insertion domain, and one β-sheet jellyroll domain. Moreover, our structural comparison with other depolymerases of K. pneumoniae suggests that the catalytic residues (Tyr528, His574 and Arg628) are highly conserved although the substrate of capsule polysaccharide is variable. Besides that, we figured out the important residues involved in the substrate binding pocket including Arg405, Tyr526, Trp550 and Phe669. This study establishes the structural and functional basis for the promising phage-derived broad-spectrum activity depolymerase therapeutics and effective CPS-degrading agents for the treatment of carbapenem-resistant K. pneumoniae K64 infections.

Prognosis and Characteristics of Hypermucoviscous Klebsiella pneumoniae Infection in Critically Ill Patients: A Case Series

Introduction Hypermucoviscous Klebsiella pneumoniae (hvKP) is related to invasive infections; however, there have been very few comprehensive reports on the clinical features and prognosis of critically ill patients with the infection. Methods We conducted a retrospective case series in a general intensive care unit in Japan. Patients with positive blood cultures for KP between January 1, 2020 and December 31, 2022 were included. hvKP was defined by the positivity in the string test. We analyzed the patient's characteristics at baseline, including comorbidities, abscess formation, Sequential Organ Failure Assessment (SOFA) score, Acute Physiology and Chronic Health Evaluation (APACHE) II score, septic shock, duration of hospitalization, 30-day mortality, and infection site. Results A total of 24 patients had a positive blood culture for KP; nine patients (37.5%) were positive for the string test (hvKP) while 15 (62.5%) were negative (non-hvKP). In both groups, the patients were old (mean age, hvKP 80.4 vs. non-hvKP 75.7 years) and more often male (five patients (55.6%) vs. 12 patients (80.0%)). No statistically significant difference was found between the two groups in terms of comorbidities, such as diabetes mellitus, chronic obstructive pulmonary disease, chronic kidney disease, and malignancy. No statistical difference was seen in abscess formation (two patients [22.2%] vs. one patient (6.7%)), SOFA score (5.2±4.8 vs. 4.7±3.4), APACHE II score (19.6 (15.0-20.0) vs. 17.0 (11.2-20.8)), septic shock (five patients (55.6%) vs. four patient (26.7%)), duration of hospitalization (37.2 (12.0-51.0) vs. 32.3 (9.5-21.0)), and 30-day mortality (two patients (22.2%) vs. two patients (13.3%)). Two cases with hvKP died within 24 h. No significant difference was seen in the infection sources; respiratory infection (2 (22.2%) vs. 1 (6.7%)), hepatobiliary infection (2 (22.2%) vs. 7 (46.7%)), and genitourinary infection (1 (11.1%) vs. 5 (33.3%)). Conclusions Critically ill patients with hvKP infection showed characteristics similar to those reported previously. However, the disease could rapidly become severe and have a poor prognostic outcome.

Structure of a novel form of phosphopantetheine adenylyltransferase from Klebsiella pneumoniae at 2.59 Å resolution

Phosphopantetheine adenylyltransferase (EC. 2.7.7.3, PPAT) catalyzes the penultimate step of the multistep reaction in the coenzyme A (CoA) biosynthesis pathway. In this step, an adenylyl group from adenosine triphosphate (ATP) is transferred to 4'-phosphopantetheine (PNS) yielding 3'-dephospho-coenzyme A (dpCoA) and pyrophosphate (PPi). PPAT from strain C3 of Klebsiella pneumoniae (KpPPAT) was cloned, expressed and purified. It was crystallized using 0.1 M HEPES buffer and PEG10000 at pH 7.5. The crystals belonged to tetragonal space group P41212 with cell dimensions of a = b = 72.82 Å and c = 200.37 Å. The structure was determined using the molecular replacement method and refined to values of 0.208 and 0.255 for Rcryst and Rfree factors, respectively. The structure determination showed the presence of three crystallographically independent molecules A, B and C in the asymmetric unit. The molecules A and B are observed in the form of a dimer in the asymmetric unit while molecule C belongs to the second dimer whose partner is related by crystallographic twofold symmetry. The polypeptide chain of KpPPAT folds into a β/α structure. The conformations of the side chains of several residues in the substrate binding site in KpPPAT are significantly different from those reported in other PPATs. As a result, the modes of binding of substrates, phosphopantetheine (PNS) and adenosine triphosphate (ATP) differ considerably. The binding studies using fluorescence spectroscopy indicated a KD value of 3.45 × 10-4 M for ATP which is significantly lower than the corresponding values reported for PPAT from other species.

Phenotypic and Genotypic Characterization of Pan-Drug-Resistant Klebsiella pneumoniae Isolated in Qatar

In secondary healthcare, carbapenem-resistant Enterobacterales (CREs), such as those observed in Klebsiella pneumoniae, are a global public health priority with significant clinical outcomes. In this study, we described the clinical, phenotypic, and genotypic characteristics of three pan-drug-resistant (PDR) isolates that demonstrated extended resistance to conventional and novel antimicrobials. All patients had risk factors for the acquisition of multidrug-resistant organisms, while microbiological susceptibility testing showed resistance to all conventional antimicrobials. Advanced susceptibility testing demonstrated resistance to broad agents, such as ceftazidime-avibactam, ceftolozane-tazobactam, and meropenem-vaborbactam. Nevertheless, all isolates were susceptible to cefiderocol, suggested as one of the novel antimicrobials that demonstrated potent in vitro activity against resistant Gram-negative bacteria, including CREs, pointing toward its potential therapeutic role for PDR pathogens. Expanded genomic studies revealed multiple antimicrobial-resistant genes (ARGs), including blaNMD-5 and blaOXA derivative types, as well as a mutated outer membrane porin protein (OmpK37).

The Clinical Efficacy of Adding Ceftazidime/Avibactam to Standard Therapy in Treating Infections Caused by Carbapenem-Resistant Klebsiella pneumonia with blaOXA-48-like Genes

Ceftazidime/avibactam (CAZ-AVI) is FDA-approved for managing infections caused by resistant gram-negative bacilli, particularly infections via carbapenem-resistant Enterobacterales pathogens. The clinical data are still limited, particularly those in Saudi Arabia. The present study is a retrospective cohort study that was carried out at the Armed Forces Hospital in the southern region of Saudi Arabia to compare the clinical and microbiological outcomes for CAZ-AVI-treated patients as monotherapy and as an add-on to standard therapy for carbapenem-resistant Klebsiella pneumonia (CRKP) OXA-48 infections to those treated with standard drugs. The study included CRKP OXA-48-like infected patients who were administered antibiotics for more than seven days from 1 August 2018 to May 2023. Patients' baseline characteristics and demography were extracted from the clinical records, and their clinical/microbiology efficiencies were assessed as per the corresponding definitions. Univariate and multivariate logistic regressions were conducted to identify the potential independent variable for CAZ-AVI efficiency. A total of 114 patient files were included for the evaluation. Among these patients, 64 used CAZ-AVI combined with standard therapy and were included in the intervention group, and 50 of them used standard therapy and were included in the comparative group. Following analysis, CAZ-AVI's clinical success was 42.2% (p = 0.028), while the intervention versus comparative groups showed decreased 30-day all-cause mortality (50.0% versus 70.0%; p = 0.036) and infection recurrence (7.8% versus 24.0%; p = 0.019), as well as substantially increased rates of microbial eradication (68.8% versus 42.0%; p = 0.007). CAZ-AVI add-on therapy rather than monotherapy showed statistically significant favored clinical and microbial outcomes over the standard therapy. Furthermore, sex (female %), ICU admission, and fever were negatively associated with patients' 30-day all-cause mortality, serving as independent negative factors. Only fever, CRP bio levels, inotropes, and ICU admissions were significant predictors influencing the CAZ-AVI's clinical efficiency. The duration of CAZ-AVI therapy positively influenced CAZ-AVI's microbial eradication, while both WBC counts and fever experiences were negative predictors. This study shows the effective usage of CAZ-AVI against CRKP OXA-48-like infections. The influencing independent variables depicted here should recommend that clinicians individualize the CAZ-AVI dose based on co-existing risk factors to achieve optimal survival and efficacy. Prospective multicenter and randomized control studies are recommended, with individualized CAZ-AVI precision administration implemented based on patients' characteristics.

KPC-2 allelic variants in Klebsiella pneumoniae isolates resistant to ceftazidime-avibactam from Argentina: blaKPC-80, blaKPC-81, blaKPC-96 and blaKPC-97

Ceftazidime-avibactam (CZA) therapy has significantly improved survival rates for patients infected by carbapenem-resistant bacteria, including KPC producers. However, resistance to CZA is a growing concern, attributed to multiple mechanisms. In this study, we characterized four clinical CZA-resistant Klebsiella pneumoniae isolates obtained between July 2019 and December 2020. These isolates expressed novel allelic variants of blaKPC-2 resulting from changes in hotspots of the mature protein, particularly in loops surrounding the active site of KPC. Notably, KPC-80 had an K269_D270insPNK mutation near the Lys270-loop, KPC-81 had a del_I173 mutation within the Ω-loop, KPC-96 showed a Y241N substitution within the Val240-loop and KPC-97 had an V277_I278insNSEAV mutation within the Lys270-loop. Three of the four isolates exhibited low-level resistance to imipenem (4 µg/mL), while all remained susceptible to meropenem. Avibactam and relebactam effectively restored carbapenem susceptibility in resistant isolates. Cloning mutant blaKPC genes into pMBLe increased imipenem MICs in recipient Escherichia coli TOP10 for blaKPC-80, blaKPC-96, and blaKPC-97 by two dilutions; again, these MICs were restored by avibactam and relebactam. Frameshift mutations disrupted ompK35 in three isolates. Additional resistance genes, including blaTEM-1, blaOXA-18 and blaOXA-1, were also identified. Interestingly, three isolates belonged to clonal complex 11 (ST258 and ST11) and one to ST629. This study highlights the emergence of CZA resistance including unique allelic variants of blaKPC-2 and impermeability. Comprehensive epidemiological surveillance and in-depth molecular studies are imperative for understanding and monitoring these complex resistance mechanisms, crucial for effective antimicrobial treatment strategies.

IMPORTANCE

The emergence of ceftazidime-avibactam (CZA) resistance poses a significant threat to the efficacy of this life-saving therapy against carbapenem-resistant bacteria, particularly Klebsiella pneumoniae-producing KPC enzymes. This study investigates four clinical isolates exhibiting resistance to CZA, revealing novel allelic variants of the key resistance gene, blaKPC-2. The mutations identified in hotspots surrounding the active site of KPC, such as K269_D270insPNK, del_I173, Y241N and V277_I278insNSEAV, prove the adaptability of these pathogens. Intriguingly, low-level resistance to imipenem and disruptions in porin genes were observed, emphasizing the complexity of the resistance mechanisms. Interestingly, three of four isolates belonged to clonal complex 11. This research not only sheds light on the clinical significance of CZA resistance but also shows the urgency for comprehensive surveillance and molecular studies to inform effective antimicrobial treatment strategies in the face of evolving bacterial resistance.