Epidemiology and Virulence of Klebsiella pneumoniae

Slaughterhouse wastewater as a reservoir for extended-spectrum β-lactamase (ESBL)-producing, and colistin-resistant Klebsiella spp. and their impact in a "One Health" perspective

Klebsiella spp. are ubiquitous bacteria capable of colonizing humans and animals, and sometimes leading to severe infections in both. Due to their high adaptability against environmental/synthetic conditions as well as their potential in aquiring antimicrobial/metal/biocide resistance determinants, Klebsiella spp. are recognized as an emerging threat to public health, worldwide. Currently, scarce information on the impact of livestock for the spread of pathogenic Klebsiella spp. is available. Thus, the phenotypic and genotypic properties of extended-spectrum β-lactamase-producing, and colistin-resistant Klebsiella strains (n = 185) from process- and wastewater of two poultry and pig slaughterhouses as well as their receiving municipal wastewater treatment plants (mWWTPs) were studied to determine the diversity of isolates that might be introduced into the food-production chain or that are released into the environment by surviving the wastewater treatment. Selectively-isolated Klebsiella spp. from slaughterhouses including effluents and receiving waterbodies of mWWTPs were assigned to various lineages, including high-risk clones involved in human outbreaks, and exhibited highly heterogeneous antibiotic-resistance patterns. While isolates originating from poultry slaughterhouses showed the highest rate of colistin resistance (32.4%, 23/71), carbapenem-resistant Klebsiella spp. were only detected in mWWTP samples (n = 76). The highest diversity of resistance genes (n = 77) was detected in Klebsiella spp. from mWWTPs, followed by isolates from pig (n = 56) and poultry slaughterhouses (n = 52). Interestingly, no carbapenemase-encoding genes were detected and mobile colistin resistance genes were only obeserved in isolates from poultry and pig slaughterhouses. Our study provides in-depth information into the clonality of livestock-associated Klebsiella spp. and their determinants involved in antimicrobial resistance and virulence development. On the basis of their pathogenic potential and clinical importance there is a potential risk of colonization and/or infection of wildlife, livestock and humans exposed to contaminated food and/or surface waters.

Non-thermal Plasma Treatment of ESKAPE Pathogens: A Review

The acronym ESKAPE refers to a group of bacteria consisting of Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. They are important in human medicine as pathogens that show increasing resistance to commonly used antibiotics; thus, the search for new effective bactericidal agents is still topical. One of the possible alternatives is the use of non-thermal plasma (NTP), a partially ionized gas with the energy stored particularly in the free electrons, which has antimicrobial and anti-biofilm effects. Its mechanism of action includes the formation of pores in the bacterial membranes; therefore, resistance toward it is not developed. This paper focuses on the current overview of literature describing the use of NTP as a new promising tool against ESKAPE bacteria, both in planktonic and biofilm forms. Thus, it points to the fact that NTP treatment can be used for the decontamination of different types of liquids, medical materials, and devices or even surfaces used in various industries. In summary, the use of diverse experimental setups leads to very different efficiencies in inactivation. However, Gram-positive bacteria appear less susceptible compared to Gram-negative ones, in general.

Infective endocarditis caused by Enterobacteriaceae: phenotypic and molecular characterization of Escherichia coli and Klebsiella pneumoniae in Rio de Janeiro, Brazil

The etiological agent for infective endocarditis (IE), a life-threatening disease, is usually gram-positive bacteria. However, gram-negative bacteria can rarely cause IE and 4% of cases are associated with morbidity and mortality. This study aimed to characterize Escherichia coli and Klebsiella pneumoniae isolates from the blood of patients with IE. The characteristics of blood isolates were compared with those of urinary isolates from patients with urinary tract infections (UTIs). The results of this study revealed that K. pneumoniae isolates from patients with IE were phylogenetically related to those from patients with UTI. Additionally, the resistance phenotype, resistance gene, virulence gene, and plasmid profiles were similar between the blood and urinary isolates. The isolates belonging to the sequence types (STs) 76, 36, 101 (K. pneumoniae), and 69 (E. coli) are reported to be associated with drug resistance. The Enterobacteriaceae isolates from patients with IE did not produce extended-spectrum β-lactamase or carbapenemase. Additionally, this study investigated the virulence phenotype, biofilm formation ability, and the ability to adhere to the epithelial cells in vitro of the isolates. The isolates from patients with IE exhibited weaker biofilm formation ability than the urinary isolates. All isolates from patients with IE could adhere to the renal epithelial cells. However, three isolates from patients with UTIs could not adhere to the epithelial cells. The closely related K. pneumoniae isolates (648, KP1, KP2, KP3, and KP4) could not form biofilms or adhere to the epithelial cells. In summary, the molecular analysis revealed that the genetic characteristics of IE-causing K. pneumoniae and E. coli were similar to those of UTI-causing isolates. These isolates belonged to the STs that are considered treatable. Genetically similar isolates did not exhibit the same virulence phenotype. Thus, these non-hypervirulent clones must be monitored as they can cause complex infections in susceptible hosts.

Genetic Background and Antibiotic Resistance Profiles of K. pneumoniae NDM-1 Strains Isolated from UTI, ABU, and the GI Tract, from One Hospital in Poland, in Relation to Strains Nationally and Worldwide

In recent years, there has been an observed increase in infections caused by carbapenem-resistant Klebsiella pneumonia (Kp) strains. The aim of this study was the phenotypic and genotypic analysis of eight K. pneumoniae NDM (Kp NDM) isolates, recovered in Poland during the years 2016 and 2018 from seven patients with urinary tract infections (UTIs), asymptomatic bacteriuria (ABU), or colonization of the gut. PCR melting profile genotyping indicated a close relationship between the strains derived from 2018, which were not related to the strain isolated in 2016. WGS results were analyzed in relation to international Kp isolates. Clonal and phylogenetic analyses were performed based on multilocus sequence typing (MLST) and single nucleotide polymorphisms (SNPs) of the core genome. The metallo-β-lactamase was assigned to the NDM-1 type and the sequence was identified as ST11. Eleven antimicrobial resistance genes were detected, mostly from plasmid contigs. Unprecedented profiles of plasmid replicons were described with the IncFII/pKPX-1 dominant replicon. In terms of the KL24 and O2v1 capsular antigen profiles, these isolates corresponded to Greek strains. Strains isolated from UTI, ABU, and colonization GI tract patients were not carrying environment-specific virulence genes. Based on the assessment of strain relationships at the genome level and their direction of evolution, the international character of the sublines was demonstrated, with a documented epidemic potential in Poland and Greece. In conclusion, some groups of patients, e.g., renal transplant recipients or those with complicated UTIs, who are frequently hospitalized and undergoing antibiotic therapy, should be monitored not only for the risk of UTI, but also for colonization by Kp NDM strains.

Modulation of Quorum Sensing and Biofilms in Less Investigated Gram-Negative ESKAPE Pathogens

Pathogenic bacteria have the ability to sense their versatile environment and adapt by behavioral changes both to the external reservoirs and the infected host, which, in response to microbial colonization, mobilizes equally sophisticated anti-infectious strategies. One of the most important adaptive processes is the ability of pathogenic bacteria to turn from the free, floating, or planktonic state to the adherent one and to develop biofilms on alive and inert substrata; this social lifestyle, based on very complex communication networks, namely, the quorum sensing (QS) and response system, confers them an increased phenotypic or behavioral resistance to different stress factors, including host defense mechanisms and antibiotics. As a consequence, biofilm infections can be difficult to diagnose and treat, requiring complex multidrug therapeutic regimens, which often fail to resolve the infection. One of the most promising avenues for discovering novel and efficient antibiofilm strategies is targeting individual cells and their QS mechanisms. A huge amount of data related to the inhibition of QS and biofilm formation in pathogenic bacteria have been obtained using the well-established gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa models. The purpose of this paper was to revise the progress on the development of antibiofilm and anti-QS strategies in the less investigated gram-negative ESKAPE pathogens Klebsiella pneumoniae, Acinetobacter baumannii, and Enterobacter sp. and identify promising leads for the therapeutic management of these clinically significant and highly resistant opportunistic pathogens.

Identification of a phage-derived depolymerase specific for KL64 capsule of Klebsiella pneumoniae and its anti-biofilm effect

The increasing prevalence of Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a serious threat to global health. Phages and phage-derived enzymes gained increasing attention for controling CRKP infections. In this study, a lytic phage P510 infecting KL64 type K. pneumoniae was isolated and characterized. Whole genome analysis and electron microscopy analysis showed that phage P510 belonged to genus Przondovirus, family Autographiviridae, the order Caudovirales. The tail fiber protein of the phage was predicted to encode capsule depolymerase. Further analysis demonstrated that recombinant depolymerase P510dep had polysaccharide-degrading activity against KL64-types capsule of K. pneumoniae, and its lysis spectrum matched to host range of phage P510. We also demonstrated that the recombinant depolymerase was able to significantly inhibit biofilm formation. The discovery of the phage-derived depolymerase lays the foundation for controlling the spread of CRKPs.

Resistance evolution of hypervirulent carbapenem-resistant Klebsiella pneumoniae ST11 during treatment with tigecycline and polymyxin

Hypervirulent carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) has recently aroused increasing attention, especially ST11, the predominant CRKP clone in China. Here, we report a case of hv-CRKP-associated infection and reveal the in-host evolution of its mechanism of resistance to tigecycline and polymyxin under clinical therapy. A total of 11 K. pneumoniae carbapenemase (KPC)-producing CRKP strains were consecutively isolated from a male patient who suffered from continuous and multisite infections. String and antimicrobial susceptibility tests identified seven hypermucoviscous strains and three tigecycline-resistant and four colistin-resistant strains. Galleria mellonella larvae infection model confirmed the hypervirulence. Pulsed-field gel electrophoresis (PFGE) separated three PFGE clusters among all strains, and further Southern blotting detected that bla_KPC-2 was located on the same-sized plasmid. Whole-genome sequencing showed that all strains belonged to the hv-CRKP ST11-KL64 clone. Diverse hypervirulence factors and resistance genes were identified. Further sequencing with the Nanopore platform was performed on the CRKP-Urine1 strain, which contained one virulence plasmid (pVi-CRKP-Urine1) and two resistance plasmids (pKPC-CRKP-Urine1 and pqnrS1-CRKP-Urine1). The gene mutations responsible for tigecycline or colistin resistance were then amplified with PCR followed by sequencing, which indicated that mutations of ramR and lon were the potential loci for tigecycline resistance and that the pmrB, phoQ and mgrB genes for colistin resistance. A novel frameshift mutation of lon was identified in the high-level tigecycline-resistant strain (MIC, 128 mg/L). The results indicate that the hypervirulent ST11-KL64 clone is a potential threat to antiinfection treatment and is capable of rapid and diverse evolution of resistance during tigecycline and polymyxin treatment.

From Klebsiella pneumoniae Colonization to Dissemination: An Overview of Studies Implementing Murine Models

Klebsiella pneumoniae is a Gram-negative pathogen responsible for community-acquired and nosocomial infections. The strains of this species belong to the opportunistic group, which is comprised of the multidrug-resistant strains, or the hypervirulent group, depending on their accessory genome, which determines bacterial pathogenicity and the host immune response. The aim of this survey is to present an overview of the murine models mimicking K. pneumoniae infectious processes (i.e., gastrointestinal colonization, urinary, pulmonary, and systemic infections), and the bacterial functions deployed to colonize and disseminate into the host. These in vivo approaches are pivotal to develop new therapeutics to limit K. pneumoniae infections via a modulation of the immune responses and/or microbiota.

Klebsiella spp. cause severe and fatal disease in Mozambican children: antimicrobial resistance profile and molecular characterization

Background

Klebsiella spp. are important pathogens associated with bacteremia among admitted children and is among the leading cause of death in children < 5 years in postmortem studies, supporting a larger role than previously considered in childhood mortality. Herein, we compared the antimicrobial susceptibility, mechanisms of resistance, and the virulence profile of Klebsiella spp. from admitted and postmortem children.

Methods

Antimicrobial susceptibility and virulence factors of Klebsiella spp. recovered from blood samples collected upon admission to the hospital (n = 88) and postmortem blood (n = 23) from children < 5 years were assessed by disk diffusion and multiplex PCR.

Results

Klebsiella isolates from postmortem blood were likely to be ceftriaxone resistant (69.6%, 16/23 vs. 48.9%, 43/88, p = 0.045) or extended-spectrum β-lactamase (ESBL) producers (60.9%, 14/23 vs. 25%, 22/88, p = 0.001) compared to those from admitted children. bla_CTX-M-15 was the most frequent ESBL gene: 65.3%, 9/14 in postmortem isolates and 22.7% (5/22) from admitted children. We found higher frequency of genes associated with hypermucoviscosity phenotype and invasin in postmortem isolates than those from admitted children: rmpA (30.4%; 7/23 vs. 9.1%, 8/88, p = 0.011), wzi-K1 (34.7%; 8/23 vs. 8%; 7/88, p = 0.002) and traT (60.8%; 14/23 vs. 10.2%; 9/88, p < 0.0001), respectively. Additionally, serine protease auto-transporters of Enterobacteriaceae were detected from 1.8% (pic) to 12.6% (pet) among all isolates. Klebsiella case fatality rate was 30.7% (23/75).

Conclusion

Multidrug resistant Klebsiella spp. harboring genes associated with hypermucoviscosity phenotype has emerged in Mozambique causing invasive fatal disease in children; highlighting the urgent need for prompt diagnosis, appropriate treatment and effective preventive measures for infection control.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06245-x.

Bacterial extracellular vesicles: Understanding biology promotes applications as nanopharmaceuticals

Extracellular vesicle (EV)-mediated communication between proximal and distant cells is a highly conserved characteristic in all of the life domains, including bacteria. These vesicles that contain a variety of biomolecules, such as proteins, lipids, nucleic acids, and small-molecule metabolites play a key role in the biology of bacteria. They are one of the key underlying mechanisms behind harmful or beneficial effects of many pathogenic, symbiont, and probiotic bacteria. These nanoscale EVs mediate extensive crosstalk with mammalian cells and deliver their cargos to the host. They are stable in physiological condition, can encapsulate diverse biomolecules and nanoparticles, and their surface could be engineered with available technologies. Based on favorable characteristics of bacterial vesicles, they can be harnessed for designing a diverse range of therapeutics and diagnostics for treatment of disorders including tumors and resistant infections. However, technical limitations for their production, purification, and characterization must be addressed in future studies.

Finding Order in the Chaos: Outstanding Questions in Klebsiella pneumoniae Pathogenesis

Klebsiella pneumoniae are Gram-negative facultative anaerobes that are found within host-associated commensal microbiomes, but they can also cause a wide range of infections that are often difficult to treat. These infections are caused by different pathotypes of K. pneumoniae, called either classical or hypervirulent strains.

Klebsiella pneumoniae are Gram-negative facultative anaerobes that are found within host-associated commensal microbiomes, but they can also cause a wide range of infections that are often difficult to treat. These infections are caused by different pathotypes of K. pneumoniae, called either classical or hypervirulent strains. These two groups are genetically distinct, inhabit nonoverlapping geographies, and cause different types of harmful infections in humans. These distinct bacterial groups have also been found to interact differently with the host immune system. Initial innate immune defenses against K. pneumoniae infection include complement, macrophages, neutrophils, and monocytes; these defenses are primary strategies employed by the host to clear infections. K. pneumoniae pathogenesis depends upon the interactions between the microbe and each of these host defenses, and it is becoming increasingly apparent that bacterial genetic diversity impacts the outcomes of these interactions. Here, we highlight recent advances in our understanding of K. pneumoniae pathogenesis, with a focus on how bacterial evolution and diversity impact K. pneumoniae interactions with mammalian innate immune host defenses. We also discuss outstanding questions regarding how K. pneumoniae can frustrate normal immune responses, capitalize upon states of immunocompromise, and cause infections with high mortality.

Analysis of endometrial microbiota in intrauterine adhesion by high-throughput sequencing

Background

Intrauterine adhesions (IUA) arise from scar tissue formation between the endometrial surfaces in response to mechanical or infectious injuries. However, the potential role of endometrial microbiota in IUA remains unclear. We aimed to explore the composition of endometrial microbiota and its potential role in IUA.

Methods

We retrospectively enrolled 46 patients diagnosed with IUA and 21 infertility patients without intrauterine lesions, as control subjects. All cases were diagnosed with hysteroscopy and endometrial tissues were taken from the intrauterine cavity using a hysteroscopic cutting ring without electricity study. After endometrial samples were collected, DNA was extracted and amplified for barcoded Illumina high-throughput next-generation sequencing targeted to the 16S rRNA V4 region for microbiota. Microbiota data were compared between two groups using α-diversity, β-diversity and Nonmetric Multidimensional Scaling based on Weighted Unifrac distance.

Results

At the phyla level, the dominant bacteria included Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria. Proteobacteria accounted for more than 64.48%. At the genus level, the proportions of Klebsiella, Shewanella, and Lactobacillus were higher in patients with IUA than in non- IUA participants (20.67% and 8.77%, P=0.006, 13.37% and 4.53%, P=0.175, 12.74% and 6.95%, P=0.882; respectively). The proportion of Acinetobacter was significantly lower in patients with IUA than in non- IUA participants (P=0.005).

Conclusions

Endometrial microbiota differ between patients with IUA and infertility patients without intrauterine lesions, and the potential variation of endometrial microbiota might cause IUA.

Resistance and induction of viable but non culturable states (VBNC) during inactivation of E. coli and Klebsiella pneumoniae by addition of H2O2 to natural well water under simulated solar irradiation

Inactivation of E. coli and Klebsiella pneumoniae by addition of H₂O₂ 10 mg L^-1 into natural well water samples containing natural total iron concentrations (around 0.3 mg L^-1) under simulated solar light was followed by bacterial culturability (plate count) and viability (DVC-FISH). Results showed that culturability of both bacteria was totally reduced while viability was only completely depleted for E. coli in well water samples depending of total iron concentration. Post-irradiation effects in presence of residual H₂O₂ showed that viability of both bacteria kept dropping being totally reduced for E. coli cells while K. pneumoniae decreased only 1-log. SEM micrographs showed that E. coli and K. pneumoniae cells underwent morphological changes and size reduction according to VBNC states. Different dark and photo-induced processes where physical-chemical features of groundwater samples play an important role could be responsible of bacteria abatement.

Biofilm Production by Carbapenem-Resistant Klebsiella pneumoniae Significantly Increases the Risk of Death in Oncological Patients

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a prominent cause of nosocomial infections associated with high rates of morbidity and mortality, particularly in oncological patients. The hypermucoviscous (HMV) phenotype and biofilm production are key factors for CRKP colonization and persistence in the host. This study aims at exploring the impact of CRKP virulence factors on morbidity and mortality in oncological patients. A total of 86 CRKP were collected between January 2015 and December 2019. Carbapenem resistance-associated genes, antibiotic susceptibility, the HMV phenotype, and biofilm production were evaluated. The median age of the patients was 71 years (range 40–96 years). Clinically infected patients were 53 (61.6%), while CRKP colonized individuals were 33 (38.4%). The most common infectious manifestations were sepsis (43.4%) and pneumonia (18.9%), while rectal surveillance swabs were the most common site of CRKP isolation (81.8%) in colonized patients. The leading mechanism of carbapenem resistance was sustained by the KPC gene (96.5%), followed by OXA-48 (2.3%) and VIM (1.2%). Phenotypic CRKP characterization indicated that 55.8% of the isolates were strong biofilm-producers equally distributed between infected (54.2%) and colonized (45.8%) patients. The HMV phenotype was found in 22.1% of the isolates, which showed a significant (P<0.0001) decrease in biofilm production as compared to non-HMV strains. The overall mortality rate calculated on the group of infected patients was 35.8%. In univariate analysis, pneumoniae significantly correlated with death (OR 5.09; CI 95% 1.08–24.02; P=0.04). The non-HMV phenotype (OR 4.67; CI 95% 1.13–19.24; P=0.03) and strong biofilm-producing strains (OR 5.04; CI95% 1.39–18.25; P=0.01) were also associated with increased CRKP infection-related mortality. Notably, the multivariate analysis showed that infection with strong biofilm-producing CRKP was an independent predictor of mortality (OR 6.30; CI 95% 1.392–18.248; P=0.004). CRKP infection presents a high risk of death among oncological patients, particularly when pneumoniae and sepsis are present. In infected patients, the presence of strong biofilm-producing CRKP significantly increases the risk of death. Thus, the assessment of biofilm production may provide a key element in supporting the clinical management of high-risk oncological patients with CRKP infection.

Advantages and limitations of microtiter biofilm assays in the model of antibiofilm activity of Klebsiella phage KP34 and its depolymerase

One of the potential antibiofilm strategies is to use lytic phages and phage-derived polysaccharide depolymerases. The idea is to uncover bacteria embedded in the biofilm matrix making them accessible and vulnerable to antibacterials and the immune system. Here we present the antibiofilm efficiency of lytic phage KP34 equipped with virion-associated capsule degrading enzyme (depolymerase) and its recombinant depolymerase KP34p57, depolymerase-non-bearing phage KP15, and ciprofloxacin, separately and in combination, using a multidrug-resistant K. pneumoniae biofilm model. The most effective antibiofilm agents were (1) phage KP34 alone or in combination with ciprofloxacin/phage KP15, and (2) depolymerase KP34p57 with phage KP15 and ciprofloxacin. Secondly, applying the commonly used biofilm microtiter assays: (1) colony count, (2) LIVE/DEAD BacLight Bacterial Viability Kit, and (3) crystal violet (CV) biofilm staining, we unravelled the main advantages and limitations of the above methods in antibiofilm testing. The diverse mode of action of selected antimicrobials strongly influenced obtained results, including a false positive enlargement of biofilm mass (CV staining) while applying polysaccharide degrading agents. We suggest that to get a proper picture of antimicrobials' effectiveness, multiple examination methods should be used and the results must be read considering the principle of each technique and the antibacterial mechanism.

Komodo-dragon cathelicidin-inspired peptides are antibacterial against carbapenem-resistant Klebsiella pneumoniae

Introduction.The rise of carbapenem-resistant enterobacteriaceae (CRE) is a growing crisis that requires development of novel therapeutics.

Hypothesis.To this end, cationic antimicrobial peptides (CAMPs) represent a possible source of new potential therapeutics to treat difficult pathogens such as carbapenem-resistantKlebsiella pneumoniae(CRKP), which has gained resistance to many if not all currently approved antibiotics, making treatment difficult.

Aim.To examine the anti-CRKP antimicrobial activity of the predicted cathelicidins derived fromVaranus komodoensis(Komodo dragon) as well as synthetic antimicrobial peptides that we created.

Methodology.We determined the minimum inhibitory concentrations of the peptides against CRKP. We also characterized the abilities of these peptides to disrupt the hyperpolarization of the bacterial membrane as well as their ability to form pores in the membrane.

Results.We did not observe significant anti-CRKP activity for the predicted native Komodo cathelicidin peptides. We found that the novel peptides DRGN-6,-7 and -8 displayed significant antimicrobial activity against CRKP with MICs of 4–8 µg ml−1. DRGN-6 peptide was the most effective peptide against CRKP. Unfortunately, these peptides showed higher than desired levels of hemolysis, althoughin vivotesting in the waxwormGalleria mellonellashowed no mortality associated with treatment by the peptide; however, CRKP-infected waxworms treated with peptide did not show an improvement in survival.

Conclusion.Given the challenges of treating CRKP, identification of peptides with activity against it represents a promising avenue for further research. Given DRGN-6′s similar level of activity to colistin, DRGN-6 is a promising template for the development of novel antimicrobial peptide-based therapeutics.

Klebsiella pneumoniae: A pathogenic bacteria transmitted through Hirudo nipponia that may cause illness in humans

Hirudo nipponia, or the leech, is not only an important economic pillar for farmers, but is also a precious raw material for medicinal materials. However, in recent years, H. nipponia has suffered from disease with symptoms including systemic oedema and hyperaemia. It has not yet been demonstrated which pathogen causes this disease and whether this could be transmitted to humans. In this study, Klebsiella pneumoniae was isolated and identified and the pathogenicity of the isolated strain was confirmed. Furthermore, by comparing the sequence of the pathogen isolated from leeches to the same pathogen infecting humans, we identified that the isolated strain is a threat to human health. This work emphasizes the importance of the first discovery of pathogenic bacteria from leeches similar to human pathogens, as well as the need for identifying zoonosis for both humans and aquatic animals.

The Characteristic of Virulence, Biofilm and Antibiotic Resistance of Klebsiella pneumoniae

Klebsiella pneumoniae is an important gram-negative opportunistic pathogen that causes a variety of infectious diseases, including urinary tract infections, bacteremia, pneumonia, and liver abscesses. With the emergence of multidrug-resistant (MDR) and hypervirulent K. pneumoniae (hvKP) strains, the rapid spread of these clinical strains in geography is particularly worrying. However, the detailed mechanisms of virulence and antibiotic resistance in K. pneumoniae are still not very clear. Therefore, studying and elucidating the pathogenic mechanisms and drug resistance mechanism of K. pneumoniae infection are important parts of current medical research. In this paper, we systematically summarized the virulence, biofilm, and antibiotic tolerance mechanisms of K. pneumoniae, and explored the application of whole genome sequencing and global proteomics, which will provide new clues for clinical treatment of K. pneumoniae.

Antimicrobial O-Alkyl Derivatives of Naringenin and Their Oximes Against Multidrug-Resistant Bacteria

New antimicrobial agents are needed to address infections caused by multidrug-resistant bacteria. Here, we are reporting novel O-alkyl derivatives of naringenin and their oximes, including novel compounds with a naringenin core and O-hexyl chains, showing activity against clinical strains of clarithromycin-resistant Helicobacter pylori, vancomycin-resistant Enterococcus faecalis, methicillin-resistant Staphylococcus aureus, and beta-lactam-resistant Acinetobacter baumannii and Klebsiella pneumoniae. The minimum inhibitory concentrations (MICs), which provide a quantitative measure of antimicrobial activity, were in the low microgram range for the selected compounds. Checkerboard assays for the most active compounds in combination with antibiotics revealed interactions that varied from synergistic to neutral.

Making medical devices safer: impact of plastic and silicone oil on microbial biofilm formation

BACKGROUND

Medical devices face the challenge of microbial biofilm attached to the surface. Ultimately, this may jeopardize the function of the device and increase the patient's risk of infection. However, reliable methods to prevent biofilm are lacking.

AIM

To investigate the effect of silicone oil-coated polypropylene plastic, used in a new automatic urinometer, on biofilm formation; furthermore, to explore the impact of silicone oil viscosity and compare polypropylene with polystyrene, another common medical plastic.

METHODS

Common pathogens, including extended-spectrum beta lactamase (ESBL) -producing and multi-drug-resistant bacteria, as well as Candida albicans, were investigated. Isogenic Escherichia coli strains deficient in the important biofilm forming factors curli, cellulose and type 1 fimbriae (fim D) were used to determine the possible mode of action by silicone oil. Clear flat-bottomed polypropylene or polystyrene wells were pretreated with either low- or medium-viscosity silicone oil and microbes were added. After 72 h, biofilm formation was quantified using crystal violet assay.

FINDINGS

Silicone oil-coated polypropylene plastic surfaces, regardless of the oil viscosity, significantly inhibited biofilm formation of all tested Gram-negative and Gram-positive bacteria, including ESBL-producing and multi-drug resistant strains, as well as C. albicans. Silicone oil did not affect bacterial or candida growth and curli fimbriae were found to be the main target of silicone oil. Polypropylene plastic itself without oil had a better effect in preventing biofilm formation than polystyrene.

CONCLUSION

These findings suggest a new strategy to decrease microbial biofilm formation, which may reduce hospital-acquired infections and prevent dysfunction of medical devices.

RcsAB and Fur Coregulate the Iron-Acquisition System via entC in Klebsiella pneumoniae NTUH-K2044 in Response to Iron Availability

The iron acquisition system is an essential virulence factor for human infection and is under tight regulatory control in a variety of pathogens. Ferric-uptake regulator (Fur) is one of Fe²⁺-responsive transcription factor that maintains iron homeostasis, and the regulator of capsule synthesis (Rcs) is known to regulate exopolysaccharide biosynthesis. We speculate the Rcs may involve in iron-acquisition given the identified regulator box in the upstream of entC that participated in the biosynthesis of enterobactin. To study the coregulation by RcsAB and Fur of entC, we measured the β-galactosidase activity and relative mRNA expression of entC in WT and mutant strains. The RcsAB- and Fur-protected regions were identified by an electrophoretic mobility shift assay (EMSA) and a DNase I footprinting assay. A regulatory cascade was identified with which Fur repressed rcsA expression and reduced RcsAB and entC expression. Our study demonstrated that entC was coregulated by two different transcriptional regulators, namely, RcsAB and Fur, in response to iron availability in Klebsiella pneumoniae.

Tea polyphenols inhibits biofilm formation, attenuates the quorum sensing-controlled virulence and enhances resistance to Klebsiella pneumoniae infection in Caenorhabditis elegans model

Bacteria cells can communicate with each other via quorum sensing (QS) system. Various physiological characteristics including virulence factors and biofilm formation are controlled by QS. So interrupting the bacterial communication is an alternative strategy instead of antibiotics for control bacterial infection. The aim of this study was to investigate the effects of tea polyphenols (TPs) on quorum sensing and virulence factors of Klebsiella pneumoniae. In vitro study showed that the anti-QS activity of tea polyphenols against Chromobacterium violaceum in violacein production. At sub-MICs, TPs inhibited the motility, reduced protease and exopolysaccharide (EPS) production and also biofilm formation in K. pneumoniae. In addition, in vivo study showed that tea polyphenols at 200 μg/mL and 400 μg/mL increased the survival rate of Caenorhabditis elegans to 73.3% and 82.2% against K. pneumonia infection. Our findings suggest that tea polyphenols can act as an effective QS inhibitor and can serve as a novel anti-virulence agent for the management of bacterial pathogens.

Draft Genome Sequence of Klebsiella pneumoniae UMB7779, Isolated from the Female Urinary Tract

Klebsiella pneumoniae is a pathogenic bacterium commonly responsible for urinary tract infections (UTIs). Here, we report the draft genome sequence of K. pneumoniae strain UMB7779, isolated from catheterized urine of a woman with a recurrent UTI.

Klebsiella pneumoniae is a pathogenic bacterium commonly responsible for urinary tract infections (UTIs). Here, we report the draft genome sequence of K. pneumoniae strain UMB7779, isolated from catheterized urine of a woman with a recurrent UTI.

Draft Genome Sequence of Klebsiella pneumoniae UMB7783, Isolated from the Female Bladder

Klebsiella pneumoniae is a Gram-negative bacterium that is highly pathogenic and frequently resistant to antibiotics. Here, we report the draft genome sequence of K. pneumoniae strain UMB7783, isolated from the female bladder.

Broad-Spectrum Cephalosporin-Resistant Klebsiella spp. Isolated from Diseased Horses in Austria

Simple Summary

Broad-spectrum cephalosporin-resistant Klebsiella pneumoniae is considered as a serious problem for public human health. To date, only a few broad-spectrum cephalosporin-resistant Klebsiella have been isolated from horses. Considering the zoonotic potential of the Klebsiella spp., and the close relationship between man and horse, this study intended to generate data on the genetic background of broad-spectrum cephalosporin-resistant Klebsiella spp. isolated from horses in Austria. Overall, samples isolated between 2012 and 2019 from 1541 horses underwent bacteriological testing, resulting in 51 specimens tested positive for Klebsiella ssp. Antimicrobial susceptibility tests revealed that seven Klebsiella ssp. isolates were not only cefotaxime-resistant but also showed resistance against other classes of antibiotics so that they were considered to be multidrug-resistant. Data from whole genome sequencing and mating experiments strongly suggest that the majority of antibiotic resistance genes is encoded on plasmids in these seven multidrug-resistant Klebsiella ssp. Considering the potential threat when commensal Klebsiella inhabiting a healthy human gut acquire new antibiotic resistances due to the exchange of plasmids with multidrug-resistant Klebsiella ssp. from horses, further monitoring of horses and other domestic animals for the presence of broad-spectrum cephalosporin-resistant Klebsiella, not only in Austria but worldwide is therefore advisable.

Abstract

The aim of the present study was to investigate the diversity of broad-spectrum cephalosporin-resistant Klebsiella spp. isolated from horses in Austria that originated from diseased horses. A total of seven non-repetitive cefotaxime-resistant Klebsiella sp. isolates were obtained during diagnostic activities from autumn 2012 to October 2019. Antimicrobial susceptibility testing was performed. The isolates were genotyped by whole-genome sequencing (WGS). Four out of seven Klebsiella isolates were identified as K. pneumoniae, two as K. michiganensis and one as K. oxytoca. All isolates displayed a multi-drug resistant phenotype. The detection of resistance genes reflected well the phenotypic resistance profiles of the respective isolates. All but one isolate displayed the extended-spectrum β-lactamases (ESBL) phenotype and carried CTX-M cefotaximases, whereas one isolate displayed an ESBL and AmpC phenotype and carried cephamycinase (CMY)-2 and sulfhydryl variable (SHV)-type b and Temoniera (TEM) β-lactamases. Among Klebsiella pneumoniae isolates, for different sequence types (ST) could be detected (ST147, ST307, ST1228, and a new ST4848). Besides resistance genes, a variety of virulence genes, including genes coding for yersiniabactin were detected. Considering the high proximity between horses and humans, our results undoubtedly identified a public health issue. This deserves to be also monitored in the years to come.

La batalla contra las superbacterias: No más antimicrobianos, no hay ESKAPE

La resistencia a los antimicrobianos es uno de los más grandes retos de la medicina moderna. Durante la última década, un grupo de seis bacterias han probado no sólo su capacidad para relativamente “escapar” de los efectos de casi cualquier antimicrobiano, sino también por ser la causa principal de las infecciones hospitalarias. Estos organismos en conjunto se les conoce como ESKAPE, siglas que derivan de la primera letra de la categoría taxonómica género, o sea, del nombre científico de cada una de estas bacterias (Enterococcus spp, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa y Enterobacter spp.). La presente revisión tiene como objetivo describir los principales mecanismos de resistencia asociados a este grupo de bacterias y el impacto que han tenido en el desarrollo de nuevas estrategias antimicrobianas.

Promising strategies for future treatment of Klebsiella pneumoniae biofilms

Klebsiella pneumoniae is a Gram-negative pathogenic bacterium that has the ability to aggregate as biofilm, representing one of the main agents in hospital infections, showing high rates of resistance to antibiotics. The K. pneumoniae biofilm aggregates are composed mainly of extracellular polysaccharides, eDNA and proteins. Besides, biofilms can attach to medical devices, such as endotracheal tubes and catheters, but are most dangerous on body surfaces. Here, we discuss the recent findings about the resistance mechanisms of K. pneumoniae biofilms, including genes and protein involved in 'classic', multidrug-resistant and hypervirulent strains, and also virulence factors. In addition, we also explore new strategies for possible treatment of these biofilms, and recently discovered molecules which may lead to future treatments.

Whole genome sequencing snapshot of multi-drug resistant Klebsiella pneumoniae strains from hospitals and receiving wastewater treatment plants in Southern Romania

We report on the genomic characterization of 47 multi-drug resistant, carbapenem resistant and ESBL-producing K. pneumoniae isolates from the influent (I) and effluent (E) of three wastewater treatment plants (WWTPs) and from Romanian hospital units which are discharging the wastewater in the sampled WWTPs. The K. pneumoniae whole genome sequences were analyzed for antibiotic resistance genes (ARGs), virulence genes and sequence types (STs) in order to compare their distribution in C, I and E samples. Both clinical and environmental samples harbored prevalent and widely distributed ESBL genes, i.e. bla_SHV, bla_OXA, bla_TEM and bla_{CTX M}. The most prevalent carbapenemase genes were bla_NDM-1, bla_OXA-48 and bla_KPC-2. They were found in all types of isolates, while bla_OXA-162, a rare bla_OXA-48 variant, was found exclusively in water samples. A higher diversity of carbapenemases genes was seen in wastewater isolates. The aminoglycoside modifying enzymes (AME) genes found in all types of samples were aac(6’), ant(2'')Ia, aph(3'), aaD, aac(3) and aph(6). Quinolone resistance gene qnrS1 and the multi-drug resistance oqxA/B pump gene were found in all samples, while qnrD and qnrB were associated to aquatic isolates. The antiseptics resistance gene qacEdelta1 was found in all samples, while qacE was detected exclusively in the clinical ones. Trimethroprim-sulfamethoxazole (dfrA, sul1 and sul2), tetracyclines (tetA and tetD) and fosfomycin (fosA6, known to be located on a transpozon) resistance genes were found in all samples, while for choramphenicol and macrolides some ARGs were detected in all samples (catA1 and catB3 / mphA), while other (catA2, cmIA5 and aac(6’)Ib / mphE and msrE) only in wastewater samples. The rifampin resistance genes arr2 and 3 (both carried by class I integrons) were detected only in water samples. The highly prevalent ARGs preferentially associating with aquatic versus clinical samples could ascribe potential markers for the aquatic (bla_SHV-145, qacEdelta1, sul1, aadA1, aadA2) and clinical (bla_OXA-1, bla_SHV-106,bla_TEM-150, aac(3)Iia, dfrA14, oqxA10; oqxB17,catB3, tetD) reservoirs of AR. Moreover, some ARGs (oqxA10; bla_SHV-145; bla_SHV-100, aac(6')Il, aph(3')VI, armA, arr2, cmlA5, bla_CMY-4, mphE, msrE, oqxB13, bla_OXA-10) showing decreased prevalence in influent versus effluent wastewater samples could be used as markers for the efficiency of the WWTPs in eliminating AR bacteria and ARGs. The highest number of virulence genes (75) was recorded for the I samples, while for E and C samples it was reduced to half. The most prevalent belong to three functional groups: adherence (fim genes), iron acquisition (ent, fep, fyu, irp and ybt genes) and the secretion system (omp genes). However, none of the genes associated with hypervirulent K. pneumoniae have been found. A total of 14 STs were identified. The most prevalent clones were ST101, ST219 in clinical samples and ST258, ST395 in aquatic isolates. These STs were also the most frequently associated with integrons. ST45 and ST485 were exclusively associated with I samples, ST11, ST35, ST364 with E and ST1564 with C samples. The less frequent ST17 and ST307 aquatic isolates harbored bla_OXA-162, which was co-expressed in our strains with bla_CTX-M-15 and bla_OXA-1.

Environmental persistence and disinfectant susceptibility of Klebsiella pneumoniae recovered from pinnipeds stranded on the California Coast

Hypermucoviscous K. pneumoniae (HMV) are emergent zoonotic pathogens associated with increased invasiveness and pathogenicity in terrestrial and marine mammals. In this study, HMV and non-HMV isolates recovered from stranded pinnipeds were used to investigate: 1) their persistence in sea and fresh water microcosms at 10 and 20°C, 2) their capacity to form biofilms, and 3) the biocide efficacy of four disinfectants on their planktonic and biofilm phenotypes. Results indicated that although HMV isolates were significantly more mucoviscous, non-HMV isolates displayed significantly greater capacity to form biofilms (p < 0.05). Additionally, non-HMV isolates persisted in greater numbers in both sea- and freshwater, particularly at 20°C. These two phenomena could be associated with the greater growth observed for non-HMV isolates in in-vitro growth-curve assays (p < 0.05). Similar susceptibility to disinfectants was detected in HMV and non-HMV isolates when exposed for 24 h; however, the minimal biofilm disinfectant eradication concentration for HMV isolates was significantly higher than that for non-HMV when exposed to disinfectants for 0.5 h. This information should be taken into consideration when developing biosecurity protocols in facilities holding marine mammals in captivity.

Tracking the environmental dissemination of carbapenem-resistant Klebsiella pneumoniae using whole genome sequencing

The emergence and dissemination of infections caused by carbapenem-resistant Klebsiella pneumoniae (CRKP) are of great concern worldwide, as there are limited options for their treatment. Thus, in this study, whole-genome sequencing (WGS) was applied to assess CRKP distribution and dissemination from hospital settings to the aquatic environment in order to identify the extent of the problem. Samples were collected from hospital wastewaters and receiving water bodies. Susceptible K. pneumoniae and CRKP were enumerated and isolated using standard methods. Seventeen CRKP were DNA-sequenced using an Illumina HiSeq X™ platform. De novo assembly and annotation were performed using SPAdes and RAST, respectively. The study analysed antibiotic resistance traits (antibiotic resistant genes, mobile genetic elements, and virulence genes) in CRKP isolates. Although influent of wastewater harboured the highest CRKP, wastewater treatment plants were efficient in reducing the threat. In terms of resistance per matrix, benthic sediment proved to harbour more CRKP (22.88%) versus susceptible K. pneumoniae, as revealed by their resistant quotient analysis, while effluent of wastewaters (4.21%) and water bodies (4.64%) had the lowest CRKP loads. The disseminating CRKP consisted of six sequence types (ST) - ST307 (n = 7), a novel ST3559 (n = 5), ST15 (n = 2), and one isolate of each of ST39, 152 and 298. All CRKP isolates harboured β-lactams (bla_CTX-M-15 and bla_OXA-1), quinolone (oqxA and oqxB) and fosfomycin (fosA) resistance genes as well as virulence genes. This study highlights the dissemination of 'high' importance and novel ST CRKP from hospital wastewater to waterbodies. This is concerning, particularly in the African context where a sizable number of people still rely on direct water resources for household use, including drinking. Further research is needed to systematically track the occurrence and distribution of these bacteria so as to mitigate their threat.

Prevalence of Potential Virulence Genes in Klebsiella spp. Isolated from Cows with Clinical Mastitis on Large Chinese Dairy Farms

Klebsiella spp. is a common cause of clinical mastitis (CM) in dairy cows. However, relatively less information is available about distribution of virulence factors of Klebsiella spp. isolated from cows with CM. Objectives of this study were, therefore, to determine the prevalence of hypermucoviscosity (HMV) phenotype, capsule serotypes, and potential virulence genes in Klebsiella spp. from cows in China with CM. A total of 241 Klebsiella spp. isolates were recovered from cows with CM on 123 dairy farms (each had >500 lactating cows) located in 13 provinces of China. Of the isolates, 124 (51%) and 117 (49%) were identified as Klebsiella pneumoniae and Klebsiella oxytoca, respectively. The prevalence of HMV was 16% for K. pneumoniae and 11% for K. oxytoca; entB (78%), fimH1 (55%), kfu (31%), and mrkD (24%) were the prevalent virulence genes among K. pneumoniae, whereas entB (50%), fimH1 (30%), and mrkD (22%) were prevalent in K. oxytoca. Prevalence of the lac gene was higher for K. pneumoniae (78%) than for K. oxytoca (13%), whereas the nif gene was more prevalent in K. oxytoca than in K. pneumoniae (12% and 1%, respectively). Fifty-six K. pneumoniae isolates were confirmed as K57, the most prevalent capsule serotype (45%). Twenty-one (18%), 20 (10%), and 9 (8%) of 117 K. oxytoca isolates were positive for K57, K5, and K54 serotypes, respectively. As the predominant serotype, K. pneumoniae K57 isolates had a higher prevalence of the HMV phenotype and fimH1 than non-K57 K. pneumoniae. In conclusion, virulence factors were commonly detected for both K. oxytoca and K. pneumoniae causing CM in Chinese dairy herds. HMV isolates were commonly identified, irrespective of species. In addition, as the predominant capsule in bovine K. pneumoniae, the K57 serotype may be better adapted to the udder environment; therefore, further studies targeting pathogenicity to mammary tissue should contribute new knowledge for vaccine development using this serotype.

Weak biofilm formation among carbapenem-resistant Klebsiella pneumoniae

Biofilm formation of multidrug and extensively drug resistant Klebsiella pneumoniae isolates is poorly understood. We investigated 139 diverse clinical K. pneumoniae isolates that possess various resistance patterns to evaluate the relationship between biofilm formation and resistance. Antimicrobial resistance was compared among a diverse collection of weak versus strong biofilm-forming K. pneumoniae, and predictors of strong biofilm formation were identified. Multi-drug resistant isolates were more common among weak (97.9%) versus strong biofilm formers (76%; P = 0.002). Carbapenem-resistant K. pneumoniae were 91% less likely to form strong biofilm (odds ratio 0.09; 95% confidence interval 0.02-0.33). The statistically significant inverse relationship between biofilm formation and antibiotic resistance suggests that virulence may be a trade-off for survival.

EtcABC, a Putative EII Complex, Regulates Type 3 Fimbriae via CRP-cAMP Signaling in Klebsiella pneumoniae

Biofilm formation by Klebsiella pneumoniae on indwelling medical devices increases the risk of infection. Both type 1 and type 3 fimbriae are important factors in biofilm formation by K. pneumoniae. We found that a putative enzyme II (EII) complex of the phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS), etcA (EIIA)-etcB (EIIB)-etcC (EIIC), regulated biofilm and type 3 fimbriae formation by K. pneumoniae STU1. In this study, the regulatory mechanism of etcABC in K. pneumoniae type 3 fimbriae formation was investigated. We found via quantitative RT-PCR that overexpression of etcABC enhanced the transcription level of the mrk operon, which is involved in type 3 fimbriae synthesis, and reduced the transcription level of the fim operon, which is involved in type 1 fimbriae synthesis. To gain further insight into the role of etcABC in type 3 fimbriae synthesis, we analyzed the region upstream of the mrk operon and found the potential cyclic 3′5′-adenosine monophosphate (cAMP) receptor protein (CRP) binding site. After crp was deleted in K. pneumoniae STU1 and two clinical isolates, these three crp mutant strains could not express MrkA, the major subunit of the fimbrial shaft, indicating that CRP positively regulated type 3 fimbriae synthesis. Moreover, a crp mutant overexpressing etcABC could not express MrkA, indicating that the regulation of type 3 fimbriae by etcABC was dependent on CRP. In addition, deletion of cyaA, which encodes the adenylyl cyclase that synthesizes cAMP, and deletion of crr, which encodes the glucose-specific EIIA, led to a reduction in lac operon regulation and therefore bacterial lactose uptake in K. pneumoniae. Exogenous cAMP but not etcABC overexpression compensated for the role of cyaA in bacterial lactose uptake. However, either etcABC overexpression or exogenous cAMP compensated for the role of crr in bacterial lac operon regulation that would eventually restore lactose uptake. We also found via ELISA and the luxCDABE reporter system that overexpression of etcABC increased intracellular cAMP levels and the transcription level of crp, respectively, in K. pneumoniae. In conclusion, overexpression of etcABC positively regulated cAMP production and cAMP-CRP activity to activate the mrk operon, resulting in increased type 3 fimbriae synthesis in K. pneumoniae.

Progress towards the development of Klebsiella vaccines

Introduction: Klebsiella pneumoniae (KP) are a leading cause of healthcare-associated infections. The dramatic increase in microbial resistance to third-generation cephalosporin and carbapenem 'front line' antimicrobial agents and the paucity of new antimicrobials have left clinicians with few therapeutic options and resulted in increased morbidity and mortality. Vaccines may reduce the incidence of infections thereby reducing the necessity for antimicrobials and are not subject to antimicrobial resistance mechanisms. Areas covered: We review whole cell, subunit, capsular polysaccharide (CPS), O polysaccharide (OPS) and conjugate vaccines against KP infection, as well as alternative KP vaccine platforms. Expert opinion: Vaccine-induced antibodies to KP CPS have been protective in preclinical studies, but the number of CPS types (>77) makes vaccines against this virulence factor less feasible. Since four OPS serotypes account of ~80% of invasive KP infections and anti-OPS antibodies are also protective in preclinical studies, both OPS-based conjugate and multiple antigen presenting system (MAPS) vaccines are in active development. Vaccines based on other KP virulence factors, such as outer membrane proteins, type 3 fimbriae (MrkA) and siderophores are at earlier stages of development. Novel strategies for the clinical testing of KP vaccines need to be developed.

Draft Genome Sequences of Novel Sequence Type 3559 Carbapenem-Resistant Klebsiella pneumoniae Isolates Recovered from the Environment

Here, we report a novel sequence type, 3559, from four genomes of Klebsiella pneumoniae isolates from South African hospital wastewater, influent wastewater, river water, and riverbed sediment. The genome annotation indicated a wide variety of resistance genes, including bla _KPC-2, and virulence factors revealing their possible pathogenicity.

Draft Genome Sequence of Providencia rettgeri APW139_S1, an NDM-18-Producing Clinical Strain Originating from Hospital Effluent in South Africa

Providencia rettgeri is an opportunistic pathogen implicated in various clinical infections. Here, we report the genome sequence of a Providencia rettgeri strain isolated from hospital effluent in South Africa, which harbors the New Delhi metallo-β-lactamase (NDM) variant 18 gene (bla_NDM-18).

Providencia rettgeri is an opportunistic pathogen implicated in various clinical infections. Here, we report the genome sequence of a Providencia rettgeri strain isolated from hospital effluent in South Africa, which harbors the New Delhi metallo-β-lactamase (NDM) variant 18 gene (bla_NDM-18). The 4,835,047-bp genome encodes a resistome and virulome that are of cardinal importance to Providencia infections.

Porin loss in Klebsiella pneumoniae clinical isolates impacts production of virulence factors and survival within macrophages

Clinical isolates of Klebsiella pneumoniae are often resistant to beta-lactam antibiotics via the acquisition of extended spectrum beta lactamase (ESBL) enzymes paired with loss of one or both major outer membrane porins. It has been well established that loss of OmpK35 and/or OmpK36 correlates with increased minimum inhibitory concentrations of antibiotics that target the peptidoglycan. However, little is known concerning the downstream effects porin loss might have on other major virulence factors such as the polysaccharide capsule or LPS. Furthermore, it is unknown whether these cumulative changes impact pathogenesis. Therefore, the focus of this study was to identify alterations in production of the major virulence factors due to porin loss; and to investigate the effect these changes have on host pathogen interactions. Our data demonstrates that loss of a single porin is paired with reductions in capsule, increased LPS content, and up-regulated transcription of compensatory porin genes. In contrast, loss of both porins resulted in a significant increase in capsule production. Loss of OmpK35 alone or dual porin loss was further associated with reduced oxidative burst by macrophages and increased ability of the bacteria to survive phagocytic killing. These data indicate that porin loss is accompanied by a suite of changes in other virulence-associated factors. These cumulative changes act to nullify any negative fitness effect due to lack of the nonspecific porin proteins, allowing the bacteria to grow and survive phagocytic immune responses.

Risk factors of mortality in patients with purple urine bag syndrome

Aim: Purple urine bag syndrome (PUBS) is rarely seen in clinical practice. Several studies have reported that PUBS is relatively benign in its clinical course, but this study aimed to identify risk factors for mortality related to PUBS. Materials and methods: In a PubMed search from October 1980 to August 2016, using the search term "Purple urine bag syndrome (PUBS)", 106 articles (n = 174 cases) were identified. This study excluded 58 cases. Among them, 14 cases did not include information on patient sex and four cases did not include information on patient age. Thirty-seven cases did not report the white blood cell (WBC) count, shock, fever, or etiology. Three cases did not report patient survival. This study considered 116 PUBS cases. Chi-square tests were used to compare the survival and mortality groups. Results: In relative risk analysis, uremia (17.8), shock (14.4), diabetes (4.8), leukocytosis (1.1), and female sex (1.1) were significant risk factors for mortality after PUBS. However, it is possible that PUBS cases are under-reported worldwide. Conclusions: PUBS is a warning sign of a urinary tract infection, and it often follows a relatively benign clinical course. This study found that female sex, leukocytosis, shock at presentation, comorbidity with diabetes, and uremia are risk factors for mortality associated with PUBS.

Complementary Role of CD4+ T Cells in Response to Pneumococcal Polysaccharide Vaccines in Humans

Bacterial pathogens expressing capsular polysaccharides are common causes of mucosal infections (pneumonia, intestinal), as well as often fatal, invasive infections (meningitis, bloodstream infections) in children and adults worldwide. These chemically simple but structurally complex carbohydrate structures on the bacterial surface confer resistance to recognition and clearance by the immune system through a range of mechanisms. Such recognition of capsular polysaccharides may be reduced by their limited ability to directly stimulate B cells and the T cells that may facilitate these humoral responses. The capsules may promote the evasion of complement deposition and activation and may sterically shield the recognition of other subjacent protein antigens by innate factors. Antibodies to capsular polysaccharides, elicited by infection and vaccines, may overcome these obstacles and facilitate bacterial agglutination at mucosal surfaces, as well as the opsonization and clearance of these organisms in tissues and the systemic compartment. However, the immunogenicity of these antigens may be limited by their lack of direct recognition by T cells (“T-independent” antigens) and their restricted ability to generate effective memory responses. In this review, we consider the mechanisms by which polysaccharides may initiate B cell responses and specific antibody responses and the role of T cells, particularly CD4+ follicular helper (TFH) cells to support this process. In addition, we also consider more recent counterintuitive data that capsular polysaccharides themselves may bind major histocompatibility antigen HLA class II to provide a more physiologic mechanism of T cell enhancement of B cell responses to capsular polysaccharides. Defining the contributions of T cells in the generation of effective humoral responses to the capsular polysaccharides will have important implications for understanding and translating this immunobiology for the development of more effective vaccines, to prevent the morbidity and mortality associated with these common mucosal and invasive pathogens in populations at risk.

Engineering root microbiomes for healthier crops and soils using beneficial, environmentally safe bacteria

The Green Revolution developed new crop varieties, which greatly improved food security worldwide. However, the growth of these plants relied heavily on chemical fertilizers and pesticides, which have led to an overuse of synthetic fertilizers, insecticides, and herbicides with serious environmental consequences and negative effects on human health. Environmentally friendly plant-growth-promoting methods to replace our current reliance on synthetic chemicals and to develop more sustainable agricultural practices to offset the damage caused by many agrochemicals are proposed herein. The increased use of bioinoculants, which consist of microorganisms that establish synergies with target crops and influence production and yield by enhancing plant growth, controlling disease, and providing critical mineral nutrients, is a potential solution. The microorganisms found in bioinoculants are often bacteria or fungi that reside within either external or internal plant microbiomes. However, before they can be used routinely in agriculture, these microbes must be confirmed as nonpathogenic strains that promote plant growth and survival. In this article, besides describing approaches for discovering plant-growth-promoting bacteria in various environments, including phytomicrobiomes and soils, we also discuss methods to evaluate their safety for the environment and for human health.

Risk factors of mortality in patients with purple urine bag syndrome

Aim: Purple urine bag syndrome (PUBS) is rarely seen in clinical practice. Several studies have reported that PUBS is relatively benign in its clinical course, but this study aimed to identify risk factors for mortality related to PUBS. Materials and methods: In a PubMed search from October 1980 to August 2016, using the search term "Purple urine bag syndrome (PUBS)", 106 articles (n = 174 cases) were identified. This study excluded 58 cases. Among them, 14 cases did not include information on patient sex and four cases did not include information on patient age. Thirty-seven cases did not report the white blood cell (WBC) count, shock, fever, or etiology. Three cases did not report patient survival. This study considered 116 PUBS cases. Chi-square tests were used to compare the survival and mortality groups. Results: In relative risk analysis, uremia (17.8), shock (14.4), diabetes (4.8), leukocytosis (1.1), and female sex (1.1) were significant risk factors for mortality after PUBS. However, it is possible that PUBS cases are under-reported worldwide. Conclusions: PUBS is a warning sign of a urinary tract infection, and it often follows a relatively benign clinical course. This study found that female sex, leukocytosis, shock at presentation, comorbidity with diabetes, and uremia are risk factors for mortality associated with PUBS.

Whole-Genome Sequence of a Novel Sequence Type 3136 Carbapenem-Resistant Klebsiella pneumoniae Strain Isolated from a Hospitalized Patient in Durban, South Africa

Here, we describe the genome sequence of a novel sequence type 3136 (ST3136) Klebsiella pneumoniae strain isolated in South Africa. The 5,574,236-bp genome harbored 23 resistance determinants and 12 virulence factors that are of cardinal importance to infections.

Here, we describe the genome sequence of a novel sequence type 3136 (ST3136) Klebsiella pneumoniae strain isolated in South Africa. The 5,574,236-bp genome harbored 23 resistance determinants and 12 virulence factors that are of cardinal importance to infections. The genomics of Klebsiella pneumoniae offer valuable insights into its pathogenicity.

Klebsiella pneumoniae infection of murine neutrophils impairs their efferocytic clearance by modulating cell death machinery

Neutrophils are the first infiltrating cell type essential for combating pneumoseptic infections by bacterial pathogens including Klebsiella pneumoniae (KPn). Following an infection or injury, removal of apoptotic infiltrates via a highly regulated process called efferocytosis is required for restoration of homeostasis, but little is known regarding the effect of bacterial infection on this process. Here we demonstrate that KPn infection impedes the efferocytic uptake of neutrophils in-vitro and in-vivo in lungs by macrophages. This impaired efferocytosis of infected neutrophils coincides with drastic reduction in the neutrophil surface exposure of apoptosis signature phospholipid phosphatidyserine (PS); and increased activity of phospholipid transporter flippases, which maintain PS in the inner leaflet of plasma membrane. Concomitantly, pharmacological inhibition of flippase activity enhanced PS externalization and restored the efferocytosis of KPn infected neutrophils. We further show that KPn infection interferes with apoptosis activation and instead activates non-apoptotic programmed cell death via activation of necroptosis machinery in neutrophils. Accordingly, pharmacological inhibition of necroptosis by RIPK1 and RIPK3 inhibitors restored the efferocytic uptake of KPn infected neutrophils in-vitro. Importantly, treatment of KPn infected mice with necroptosis inhibitor improved the disease outcome in-vivo in preclinical mouse model of KPn pneumonia. To our knowledge, this is the first report of neutrophil efferocytosis impairment by KPn via modulation of cell death pathway, which may provide novel targets for therapeutic intervention of this infection.

Inflammatory diseases caused by infectious or sterile injuries are often characterized by pathological accumulation of dead or dying infiltrating cells. Pneumonic sepsis caused by Klebsiella pneumoniae (KPn), an opportunistic pathogen, has similar etiology, however, the underlying mechanism remains unknown. Here we report that KPn infection subverts a protective host process termed efferocytosis, by which the phagocytic cells engulf and clear dead/dying cells thereby resolving inflammation and infection. Our results show that KPn infected neutrophils are cleared less efficiently via efferocytosis than the uninfected neutrophils. Mechanistic studies implicated a reduced exposure of “eat me” signal phosphatidyleserine (PS) via increased flippase activity and skewing of cell death pathway toward necroptosis in impaired efferocytosis of infected neutrophils. Accordingly, pharmacological reversal of PS exposure by flippase inhibition, treatment with necroptosis inhibitors restored the efferocytic clearance of KPn infected neutrophils, and improved the disease outcome in a preclinical model of pneumonic sepsis. To our knowledge this is the first report of KPn subversion of efferocytic clearance of neutrophils by impairing pro-efferocytic apoptotic signatures and activation of necroptosis machinery. This could lead to novel therapeutic targets against KPn infection and associated inflammation in pneumonic sepsis.

Variant O89 O-Antigen of E. coli Is Associated With Group 1 Capsule Loci and Multidrug Resistance

Bacterial surface polysaccharides play significant roles in fitness and virulence. In Gram-negative bacteria such as Escherichia coli, major surface polysaccharides are lipopolysaccharide (LPS) and capsule, representing O- and K-antigens, respectively. There are multiple combinations of O:K types, many of which are well-characterized and can be related to ecotype or pathotype. In this investigation, we have identified a novel O:K permutation resulting through a process of major genome reorganization in a clade of E. coli. A multidrug-resistant, extended-spectrum β-lactamase (ESBL)-producing strain - E. coli 26561 - represented a prototype of strains combining a locus variant of O89 and group 1 capsular polysaccharide. Specifically, the variant O89 locus in this strain was truncated at gnd, flanked by insertion sequences and located between nfsB and ybdK and we apply the term O89m for this variant. The prototype lacked colanic acid and O-antigen loci between yegH and hisI with this tandem polysaccharide locus being replaced with a group 1 capsule (G1C) which, rather than being a recognized E. coli capsule type, this locus matched to Klebsiella K10 capsule type. A genomic survey identified more than 200 E. coli strains which possessed the O89m locus variant with one of a variety of G1C types. Isolates from our collection with the combination of O89m and G1C all displayed a mucoid phenotype and E. coli 26561 was unusual in exhibiting a mucoviscous phenotype more recognized as a characteristic among Klebsiella strains. Despite the locus truncation and novel location, all O89m:G1C strains examined showed a ladder pattern typifying smooth LPS and also showed high molecular weight, alcian blue-staining polysaccharide in cellular and/or extra-cellular fractions. Expression of both O-antigen and capsule biosynthesis loci were confirmed in prototype strain 26561 through quantitative proteome analysis. Further in silico exploration of more than 200 E. coli strains possessing the O89m:G1C combination identified a very high prevalence of multidrug resistance (MDR) - 85% possessed resistance to three or more antibiotic classes and a high proportion (58%) of these carried ESBL and/or carbapenemase. The increasing isolation of O89m:G1C isolates from extra-intestinal infection sites suggests that these represents an emergent clade of invasive, MDR E. coli.

Identification of Two Regulators of Virulence That Are Conserved in Klebsiella pneumoniae Classical and Hypervirulent Strains

Klebsiella pneumoniae is widely recognized as a pathogen with a propensity for acquiring antibiotic resistance. It is capable of causing a range of hospital-acquired infections (urinary tract infections [UTI], pneumonia, sepsis) and community-acquired invasive infections. The genetic heterogeneity of K. pneumoniae isolates complicates our ability to understand the virulence of K. pneumoniae. Characterization of virulence factors conserved between strains as well as strain-specific factors will improve our understanding of this important pathogen. The MarR family of regulatory proteins is widely distributed in bacteria and regulates cellular processes such as antibiotic resistance and the expression of virulence factors. Klebsiella encodes numerous MarR-like proteins, and they likely contribute to the ability of K. pneumoniae to respond to and survive under a wide variety of environmental conditions, including those present in the human body. We tested loss-of-function mutations in all the marR homologues in a murine pneumonia model and found that two (kvrA and kvrB) significantly impacted the virulence of K1 and K2 capsule type hypervirulent (hv) strains and that kvrA affected the virulence of a sequence type 258 (ST258) classical strain. In the hv strains, kvrA and kvrB mutants displayed phenotypes associated with reduced capsule production, mucoviscosity, and transcription from galF and manC promoters that drive expression of capsule synthesis genes. In contrast, kvrA and kvrB mutants in the ST258 strain had no effect on capsule gene expression or capsule-related phenotypes. Thus, KvrA and KvrB affect virulence in classical and hv strains but the effect on virulence may not be exclusively due to effects on capsule production.

In addition to having a reputation as the causative agent for hospital-acquired infections as well as community-acquired invasive infections, Klebsiella pneumoniae has gained widespread attention as a pathogen with a propensity for acquiring antibiotic resistance. Due to the rapid emergence of carbapenem resistance among K. pneumoniae strains, a better understanding of virulence mechanisms and identification of new potential drug targets are needed. This study identified two novel regulators (KvrA and KvrB) of virulence in K. pneumoniae and demonstrated that their effect on virulence in invasive strains is likely due in part to effects on capsule production (a major virulence determinant) and hypermucoviscosity. KvrA also impacts the virulence of classical strains but does not appear to affect capsule gene expression in this strain. KvrA and KvrB are conserved among K. pneumoniae strains and thus could regulate capsule expression and virulence in diverse strains regardless of capsule type.

The Ferric uptake regulator (Fur) and iron availability control the production and maturation of the antibacterial peptide microcin E492

Microcin E492 is a pore-forming bacteriocin with toxic activity against Enterobacteriaceae, which undergoes amyloid aggregation as a mechanism to regulate its toxicity. To be active, it requires the posttranslational attachment to the C-terminus of a glycosylated enterochelin derivative (salmochelin), a process carried out by the proteins MceC, MceI and MceJ encoded in the MccE492 gene cluster. Both microcin E492 and salmochelin have a proposed role in the virulence of the bacterial pathogen Klebsiella pneumoniae. Besides, enterochelin is produced as a response to low iron availability and its synthesis is controlled by the global iron regulator Fur. Since the production of active microcin E492 depends on enterochelin biosynthesis, both processes could be coordinately regulated. In this work, we investigated the role of Fur in the expression of the microcin E492 maturation genes mceCJI. mceC was not regulated by Fur as it occurs with its homolog iroB in Salmonella enterica. We demonstrated that mceJI along with the previously uncharacterized gene mceX are transcribed as a single mRNA, and that Fur binds in vivo to a Fur box located upstream of the mceX-mceJI unit. Also, we established that the expression of these genes decreased in a condition of high iron availability, while this effect is abrogated in a Δfur background. Furthermore, our results indicated that MceX acts as a negative regulator of microcin E492 structural gene expression, coupling its synthesis to the iron-dependent regulatory circuit. Consequently, fur or mceX overexpression led to a significant decrease in the antibacterial activity of cells producing microcin E492. Altogether these results show that both the expression of microcin E492 maturation genes mceJI, and MceX the negative regulator of microcin E492 synthesis, are coordinated with the enterochelin production by Fur, depending on the iron levels in the medium.

Molecular detection and PCR-RFLP analysis using Pst1 and Alu1 of multidrug resistant Klebsiella pneumoniae causing urinary tract infection in women in the eastern part of Bangladesh

Klebsiella pneumoniae is the second leading causative agent of UTI. In this study, a rapid combined polymerase chain reaction and restriction fragment length polymorphism analysis was developed to identify K. pneumoniae in women, infected with urinary tract infection in the Sylhet city of Bangladesh. Analysis of 11 isolates from women at the age range of 20-55 from three different hospitals were done firstly by amplification with K. pneumoniae specific ITS primers. All of the 11 collected isolates were amplified in PCR and showed the expected 136 bp products. Then, restriction fragment length polymorphism analysis of 11 isolates were conducted after PCR amplification by 16s rRNA universal primers, followed by subsequent digestion and incubation with two restriction enzymes, Pst1 and Alu1. Seven out of 11 isolates were digested by Pst1 restriction enzymes, six isolates digested by Alu1, and while others were negative for both enzymes. Data results reveal that, women at age between 25 and 50 were digested by both enzymes. A woman aged over than 50 was negative while bellow 20 was digested by only Pst1. The results could pave the tactic for further research in the detection of K. pneumoniae from UTI infected women.