Molecular pathogenesis of Klebsiella pneumoniae

First Report of Potentially Pathogenic Klebsiella pneumoniae from Serotype K2 in Mollusk Tegillarca granosa and Genetic Diversity of Klebsiella pneumoniae in 14 Species of Edible Aquatic Animals

Klebsiella pneumoniae can cause serious pneumonitis in humans. The bacterium is also the common causative agent of hospital-acquired multidrug-resistant (MDR) infections. Here we for the first time reported the genetic diversity of K. pneumoniae strains in 14 species of edible aquatic animals sampled in the summer of 2018 and 2019 in Shanghai, China. Virulence-related genes were present in the K. pneumoniae strains (n = 94), including the entB (98.9%), mrkD (85.1%), fimH (50.0%), and ybtA (14.9%) strains. Resistance to sulfamethoxazole-trimethoprim was the most prevalent (52.1%), followed by chloramphenicol (31.9%), and tetracycline (27.7%), among the strains, wherein 34.0% had MDR phenotypes. Meanwhile, most strains were tolerant to heavy metals Cu2+ (96.8%), Cr3+ (96.8%), Zn2+ (91.5%), Pb2+ (89.4%), and Hg2+ (81.9%). Remarkably, a higher abundance of the bacterium was found in bottom-dwelling aquatic animals, among which mollusk Tegillarca granosa contained K. pneumoniae 8-2-5-4 isolate from serotype K2 (ST-2026). Genome features of the potentially pathogenic isolate were characterized. The enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR)−based genome fingerprinting classified the 94 K. pneumoniae strains into 76 ERIC genotypes with 63 singletons, demonstrating considerable genetic diversity in the strains. The findings of this study fill the gap in the risk assessment of K. pneumoniae in edible aquatic animals.

Problems Associated with Co-Infection by Multidrug-Resistant Klebsiella pneumoniae in COVID-19 Patients: A Review

To date, coronavirus disease 2019 (COVID-19) and its variants have been reported as a novel public health concern threatening us worldwide. The presence of Klebsiella pneumoniae in COVID-19-infected patients is a major problem due to its resistance to multiple antibiotics, and it can possibly make the management of COVID-19 in patients more problematic. The impact of co-infection by K. pneumoniae on COVID-19 patients was explored in the current review. The spread of K. pneumoniae as a co-infection among critically ill COVID-19 patients, particularly throughout hospitalization, was identified and recorded via numerous reports. Alarmingly, the extensive application of antibiotics in the initial diagnosis of COVID-19 infection may reduce bacterial co-infection, but it increases the antibiotic resistance of bacteria such as the strains of K. pneumoniae. The correct detection of multidrug-resistant K. pneumoniae can offer a supportive reference for the diagnosis and therapeutic management of COVID-19 patients. Furthermore, the prevention and control of K. pneumoniae are required to minimize the risk of COVID-19. The aim of the present review is, therefore, to report on the virulence factors of the K. pneumonia genotypes, the drug resistance of K. pneumonia, and the impact of K. pneumoniae co-infection with COVID-19 on patients through a study of the published scientific papers, reports, and case studies.

KbvR mutant of Klebsiella pneumoniae affects the synthesis of type 1 fimbriae and provides protection to mice as a live attenuated vaccine

Klebsiella pneumoniae is a leading cause of severe infections in humans and animals, and the emergence of multidrug-resistant strains highlights the need to develop effective vaccines for preventing such infections. Live attenuated vaccines are attractive vaccine candidates available in the veterinary field. We recently characterized that the K. pneumoniae kbvR (Klebsiella biofilm and virulence regulator) mutant was a highly attenuated strain in the mice model. In the present study, the characterization, safety, and protective efficacy of ΔkbvR strain as a live attenuated vaccine were evaluated. The synthesis and activity of type 1 fimbriae were increased in the ΔkbvR strain. All mice inoculated by the subcutaneous route with 105, 106, and 107 colony-forming units (CFU) doses of the ΔkbvR strain survived. Subcutaneous immunization with two doses of 105 or 107 CFU ΔkbvR elicited a robust humoral immune response, and provided protection against the following K. pneumoniae intraperitoneal infection. The antisera of mice immunized with 105 CFU dose improved the opsonophagocytic ability and complement-mediated lysis not only to the same serotype strain but also to the different serotype strain. The passive transfer of antisera from 105 CFU dose-immunized mice provided protection against K. pneumoniae infection. Overall, our results suggest the great potential of the ΔkbvR strain as a novel vaccine candidate against K. pneumoniae infections in herds or humans.

Host defense against the infection of Klebsiella pneumoniae: New strategy to kill the bacterium in the era of antibiotics?

Klebsiella pneumoniae (K. pneumoniae) is a typical gram-negative iatrogenic bacterium that often causes bacteremia, pneumonia and urinary tract infection particularly among those with low immunity. Although antibiotics is the cornerstone of anti-infections, the clinical efficacy of β-lactamase and carbapenems drugs has been weakened due to the emergence of drug-resistant K. pneumoniae. Recent studies have demonstrated that host defense plays a critical role in killing K. pneumoniae. Here, we summarize our current understanding of host immunity mechanisms against K. pneumoniae, including mechanical barrier, innate immune cells, cellular immunity and humoral immunity, providing a theoretical basis and the new strategy for the clinical treatment of K. pneumoniae through improving host immunity.

Les misérables: a Parallel Between Antimicrobial Resistance and COVID-19 in Underdeveloped and Developing Countries

Purpose of Review

The COVID-19 pandemic has been responsible for more than 6.3 million deaths worldwide. During the pandemic, the indiscriminate use of antibiotics has increased, contributing to the spread of multidrug-resistant bacteria. In this review, we aim to determine the spread and impact of antibiotic treatments in patients with COVID-19, focusing on underdeveloped and developing countries.

Recent Findings

Meta-analysis revealed that bacterial co-infections and secondary infections are relatively rare in COVID-19 patients, corresponding to less than 20% of hospitalized patients. Even so, most of these patients have received antibiotic treatments.

Summary

This review discusses how the COVID-19 pandemic could increase the emergence of multidrug-resistant strains to currently available antibiotics. Initially, we discussed the spread and impact of multidrug resistance of ESKAPE pathogens associated with nosocomial infections and analyzed their risk of secondary infections in patients with COVID-19. Then we highlight three factors related to the spread of resistant bacteria during the current pandemic: overprescription of antibiotics followed by self-medication. Finally, we discussed the lack of availability of diagnostic tests to discriminate the etiologic agent of a disease. All these factors lead to inappropriate use of antibiotics and, therefore, to an increase in the prevalence of resistance, which can have devastating consequences shortly. The data compiled in this study underscore the importance of epidemiological surveillance of hospital isolates to provide new strategies for preventing and controlling infections caused by multidrug-resistant bacteria. In addition, the bibliographic research also highlights the need for an improvement in antibiotic prescribing in the health system.

A review: Virulence factors of Klebsiella pneumonia as emerging infection on the food chain

Health problems can be caused by consuming foods that have been processed in unsanitary conditions; hence, the study of the impact of contamination on food and its prevention has become critical. The disease caused by Klebsiella pneumoniae in food is increasing significantly every year across the world. The main factors that are essential for the virulence of K. pneumoniae are lipopolysaccharide and polysaccharide capsules. Furthermore, K. pneumoniae is capable of forming biofilms. Capsule polysaccharides, fimbriae types 1 and 3, are crucial virulence factors contributing to biofilm formation in K. pneumoniae. The food contamination by K. pneumoniae may not directly pose a public health risk; however, the presence of K. pneumoniae refers to unhygienic practices in food handling. This article aims to demonstrate that K. pneumoniae should be considered as a potential pathogen that spreads through the food chain and that necessary precautions should be taken in the future.

Combination effect of azithromycin with TCM preparation Xiyanping injection against Klebsiella pneumoniae infection in rats

BACKGROUND

Klebsiella pneumoniae is known as one of the most principal opportunistic human pathogens. Although antibiotics such as the first-line agent azithromycin (AZM) usually are efficient for the treatment of K. pneumonia-related infections, growing threat from antibiotic resistance has become a major challenge. Various preparations based on traditional Chinese medicine (TCM) clinical experience have been developed to help combat such a global public health threat, including Xiyanping injection (XYP) that is made from the natural product andrographolide with potent heat-clearing and toxin-resolving functions.

PURPOSE

The present study aimed to demonstrate the therapeutic potential, as well as the action of mechanism of AZM in combination with XYP against K. pneumonia infection in rats.

METHODS

Pneumonia model of K. pneumoniae infection in rats was established and subjected to various treatments. The lung histopathological lesions were evaluated. ELISA and Griess techniques were used to determine the level of crucial cytokines. The protein expressions of MAPKs and NF-κB pathways were analyzed by Western blotting.

RESULTS

The combination in vivo could significantly inhibit the proliferation of K. pneumoniae in lung, improve the pathological changes of lung and reduce inflammatory factors in lung homogenate and bronchoalveolar lavage fluid, mainly by inactivating MAPKs and NF-κB signaling pathways. Combination therapy caused one-fold increase in apparent distribution volume of AZM in rats after multiple dosing, along with a significant increase of AZM level in lungs but obvious decrease in livers.

CONCLUSION

The combination therapy of AZM and XYP showed increased antibacterial and anti-inflammatory properties, indicating that it might be used to treat K. pneumoniae infection.

Liver Abscess Combined with Endogenous Endophthalmitis Caused by Genotype ST25 Serotype K2 Hypervirulent Klebsiella pneumoniae: A Case Report

At present, invasive syndrome caused by hypervirulent Klebsiella pneumoniae (HvKp) is a widespread concern, and HvKp strains of different genotypes have been isolated. Here, we report a case of community-acquired liver abscess and endogenous endophthalmitis caused by a genotype ST25 serotype K2 (ST25-K2) HvKp strain in China. A 51-year-old man with diabetes was transferred to our hospital from a local community hospital with persistent fever for > 20 days and blurred vision in his left eye. A detailed examination revealed a liver abscess, endogenous endophthalmitis, and pneumonia. Bacterial cultures of pus from the liver abscess and the vitreous abscess of the left eye yielded Klebsiella pneumoniae (Kp), which was sensitive to the recommended drugs. In addition to positive string tests, a genetic analysis showed that the strain belonged to sequence type 25 (ST25) and serotype K2, and carried already-reported virulence genes, including iucA, rmpA2, rmpA, aerobactin, and entB. The pathogenic agent isolated from this patient was identified as HvKp. The patient’s general condition improved after a combination of treatments, including antimicrobial therapy, abscess drainage, and nutritional support. Unfortunately, the patient lost the vision in his left eye and developed secondary glaucoma, resulting in inevitable enucleation. Sequence 25 serotype K2 HvKp strains have been previously associated with nosocomial infections, but none associated with community-acquired liver abscess combined with endogenous endophthalmitis has yet been reported. Clinicians must be alert to the possibility of genotype ST25-K2 HvKp infection in patients with community-acquired liver abscess combined with an invasive infection, such as ocular discomfort.

Molecular Characterization of Klebsiella pneumoniae Isolated from Sputum in a Tertiary Hospital in Xinxiang, China

Background

In clinical practice, Klebsiella pneumoniae (K. pneumoniae) is a common opportunistic pathogen responsible for nosocomial infection. This study aimed to analyze the trend of antimicrobial susceptibility and virulent characteristics of K. pneumoniae isolated from sputum. In clinics, data of the current study will help in the clinical treatment of K. pneumoniae infection.

Results

The current research showed the resistance rates of the 20 K. pneumoniae isolates against 13 antibiotics ranged from 15.0% to 80.0%. The detection rate of extended spectrum β-lactamases (ESBLs) was up to 55%, while bla_SHV was the most prevalent ESBLs genes. Four strains (25.0%) of K. pneumoniae presented hypermucoviscous phenotype (HMV). Moreover, 18 strains (90.0%) showed the stronger biofilm-forming ability. wzi, wab_G, fim_H, mrk_D were the most prevalent virulence genes in current research. Ten strains were found capsule typing and the higher genetic diversity of colonizing K. pneumoniae in this region. K₁₉ exhibited a strong positive correlation with imipenem resistance, while K₁ showed strong correlations with mag_A . Furthermore, HMV phenotype showed significantly negative correlations with multidrug-resistant.

Conclusion

In the hospital, the antibiotic resistance of K. pneumoniae (isolated from sputum samples) has a serious concern. Additionally, strains of K. pneumoniae show the higher genetic diversity.

Genetic and Functional Characterization of a Conjugative KpVP-2-Type Virulence Plasmid From a Clinical Klebsiella pneumoniae Strain

The main mechanism of virulence in Klebsiella pneumoniae is the acquisition of K. pneumoniae virulence plasmids (KpVPs), which include two dominant types, namely, KpVP-1 (carrying iuc1, iro1, rmpA, and rmpA2) and KpVP-2 (carrying iuc2, iro2, and rmpA). Both are non-conjugative and associated with different hypervirulent clones. In contrast to KpVP-1 reported in K1, K2, and other serotypes of K. pneumoniae, KpVP-2 was only reported in K2 strains and rarely characterized. In this study, we identified a conjugative KpVP-2-type virulence plasmid from a clinical hypervirulent K. pneumoniae strain. This plasmid was generated by the integration of conjugative transfer genes into the KpVP-2-type plasmid Kp52.145 II and could be readily conjugated to Escherichia coli strain EC600 and K. pneumoniae strains of various types which are clinically existing, mediating hypervirulence. Furthermore, this kind of conjugative KpVP-2-type virulence plasmid has been disseminated in clinical settings in Hong Kong and other regions of the world. The generation of conjugative virulence plasmid may promote its transmission and explain the evolution of this type of virulence plasmid.

Molecular epidemiological characteristics of carbapenem-resistant Klebsiella pneumoniae among children in China

Klebsiella pneumoniae infection and antimicrobial resistance among children are major concerns. The occurrence of hypervirulent K. pneumoniae (hvKp) infections is gradually increasing worldwide, and disinfectant resistance is also being reported. Carbapenem- and disinfectant-resistant hvKp infection has made clinical treatment and nosocomial infection control among children increasingly challenging. In this study, whole-genome sequencing was conducted among 34 Carba NP-positive carbapenem-resistant K. pneumoniae (CRKP) strains, and the distribution of antibiotic resistance genes, virulence genes and disinfectant resistance genes was determined. Eleven distinct STs were identified, and most of them were ST11 (58.8%). Among the carbapenem resistance genes, KPC-2 was predominant (61.8%), followed by NDM-1 (26.5%) and IPM-4 (11.8%), and no other carbapenemase genes were found. Twelve virulence genes were investigated. All 34 CRKP strains carried the following virulence genes: rcsA/B, entA, fimA/H and mrkA/D. The gene iucB was present in only 3 (8.9%) CRKP strains. The positive detection rates of the iroN and ybtA genes were 94.1% and 64.7%, respectively. None of the strains was found to carry the rmpA and iroB genes. Two disinfectant resistance genes were investigated in this study. Twenty-one (61.8%) strains carried both the qacE and cepA disinfectant resistance genes, 13 (38.2%) CRKP strains carried only the cepA gene, and no strains with only the qacE gene was detected. The correlations among virulence, drug resistance and disinfectant tolerance showed that the virulence and disinfectant resistance genes were distinct among several types of carbapenemase-producing CRKP strains.

Review of Known and Unknown Facts of Klebsiella Pneumoniae and its Relationship with Antibiotics

Antibiotics are commonly used to treat bacterial respiratory infections, but they can exacerbate inflammation by releasing microbial components that overstimulate the immune system, leading to greater tissue damage. Klebsiella pneumoniae is a gram-negative, rod-shaped bacteria of the family Enterobacteriaceae. Knowing about Klebsiella pneumoniae is extremely important in the present situation, as it is one of the major causal organisms of pneumonia. Internal and external factors of K. pneumoniae are responsible for the entry and multiplication inside the host. Antibiotics against K. pneumoniae are a class of Penicillins, Cephalosporins, Monobactams, and Carbapenems which have the β-lactam ring in common with variable side chains. Combating the antibiotics by synthesizing the enzymes like beta-lactamases is the main reason for the survival of these organisms against newer generation antibiotics. In this review, we have tried to discuss about Klebsiella pneumoniae, antibiotics, and their mechanism of action.

Candida Worsens Klebsiella pneumoniae Induced-Sepsis in a Mouse Model with Low Dose Dextran Sulfate Solution through Gut Dysbiosis and Enhanced Inflammation

Klebsiella pneumoniae is an opportunistic pathogen and a commensal organism that is possibly enhanced in several conditions with gut dysbiosis, and frequently detectable together with Candida overgrowth. Here, K. pneumoniae with or without Candida albicans was daily orally administered for 3 months in 0.8% dextran sulfate solution-induced mucositis mice and also tested in vitro. As such, Candida worsened Klebsiella-DSS-colitis as demonstrated by mortality, leaky gut (FITC-dextran assay, bacteremia, endotoxemia, and serum beta-glucan), gut dysbiosis (increased Deferribacteres from fecal microbiome analysis), liver pathology (histopathology), liver apoptosis (activated caspase 3), and cytokines (in serum and in the internal organs) when compared with Klebsiella-administered DSS mice. The combination of heat-killed Candida plus Klebsiella mildly facilitated inflammation in enterocytes (Caco-2), hepatocytes (HepG2), and THP-1-derived macrophages as indicated by supernatant cytokines or the gene expression. The addition of heat-killed Candida into Klebsiella preparations upregulated TLR-2, reduced Occludin (an intestinal tight junction molecule), and worsened enterocyte integrity (transepithelial electrical resistance) in Caco-2 and enhanced casp8 and casp9 (apoptosis genes) in HepG2 when compared with heat-killed Klebsiella alone. In conclusion, Candida enhanced enterocyte inflammation (partly through TLR-2 upregulation and gut dysbiosis) that induced gut translocation of endotoxin and beta-glucan causing hyper-inflammatory responses, especially in hepatocytes and macrophages.

Design, synthesis, and characterization of novel eco-friendly chitosan-AgIO3 bionanocomposite and study its antibacterial activity

This work reports a facile and green approach to preparing AgIO₃ nanoparticles decorated with chitosan (chitosan-AgIO₃). The bionanocomposite was fully characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM) images, energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD). The antibacterial effect of chitosan-AgIO₃ bionanocomposite was investigated for Pseudomonas aeruginosa, Klebsiella pneumoniae, Staphylococcus saprophyticus, Escherichia coli, and Staphylococcus aureus as pathogen microorganisms via the plate count method, disk diffusion method, and optical density (OD) measurements. The antibacterial performance of the bionanocomposite was compared with two commercial drugs (penicillin and silver sulfadiazine) and in some cases, the synthesized bionanocomposite has a better effect in the eradication of bacteria. The bionanocomposite represented great antibacterial properties. Flow cytometry was performed to investigate the mechanism of bionanocomposite as an antibacterial agent. Reactive oxygen species (ROS) production was responsible for the bactericidal mechanisms. These results demonstrate that the chitosan-AgIO₃ bionanocomposite, as a kind of antibacterial material, got potential for application in a broad range of biomedical applications and water purification. The design and synthesis of green and biodegradable antibacterial materials with simple processes and by using readily available materials cause the final product to be economically affordable and could be scaled in different industries.

Anti-Biofilm and Associated Anti-Virulence Activities of Selected Phytochemical Compounds against Klebsiella pneumoniae

The ability of Klebsiella pneumoniae to form biofilm renders the pathogen recalcitrant to various antibiotics. The difficulty in managing K. pneumoniae related chronic infections is due to its biofilm-forming ability and associated virulence factors, necessitating the development of efficient strategies to control virulence factors. This study aimed at evaluating the inhibitory potential of selected phytochemical compounds on biofilm-associated virulence factors in K. pneumoniae, as well as authenticating their antibiofilm activity. Five phytochemical compounds (alpha-terpinene, camphene, fisetin, glycitein and phytol) were evaluated for their antibacterial and anti-biofilm-associated virulence factors such as exopolysaccharides, curli fibers, and hypermucoviscosity against carbapenem-resistant and extended-spectrum beta-lactamase-positive K. pneumoniae strains. The antibiofilm potential of these compounds was evaluated at initial cell attachment, microcolony formation and mature biofilm formation, then validated by in situ visualization using scanning electron microscopy (SEM). Exopolysaccharide surface topography was characterized using atomic force microscopy (AFM). The antibacterial activity of the compounds confirmed fisetin as the best anti-carbapenem-resistant K. pneumoniae, demonstrating a minimum inhibitory concentration (MIC) value of 0.0625 mg/mL. Phytol, glycitein and α-terpinene showed MIC values of 0.125 mg/mL for both strains. The assessment of the compounds for anti-virulence activity (exopolysaccharide reduction) revealed an up to 65.91% reduction in phytol and camphene. Atomic force microscopy detected marked differences between the topographies of untreated and treated (camphene and phytol) exopolysaccharides. Curli expression was inhibited at both 0.5 and 1.0 mg/mL by phytol, glycitein, fisetin and quercetin. The hypermucoviscosity was reduced by phytol, glycitein, and fisetin to the shortest mucoid string (1 mm) at 1 mg/mL. Phytol showed the highest antiadhesion activity against carbapenem-resistant and extended-spectrum beta-lactamase-positive K. pneumoniae (54.71% and 50.05%), respectively. Scanning electron microscopy correlated the in vitro findings, with phytol significantly altering the biofilm architecture. Phytol has antibiofilm and antivirulence potential against the highly virulent K. pneumoniae strains, revealing it as a potential lead compound for the management of K. pneumoniae-associated infections.

Epidemiology, Environmental Risks, Virulence, and Resistance Determinants of Klebsiella pneumoniae From Dairy Cows in Hubei, China

Klebsiella pneumoniae (K. pneumoniae) is an opportunistic pathogen, which causes serious infections in humans and animals. To investigate the antimicrobial resistance pattern and virulence profile of K. pneumoniae, a total of 887 samples were collected from both the healthy and mastitis cows and the bedding, feed, feces, air, drinking water, spraying water, washing water, and milk cup swabs from five dairy farms in Hubei, China, during 2019 and 2020. K. pneumoniae was isolated and identified using PCR of the khe and 16S rDNA sequencing. A genotypic characterization was performed for K. pneumoniae isolates using wzi typing and multilocus sequence typing (MLST). Antimicrobial resistances were confirmed using broth microdilution against 17 antimicrobial agents and resistance and virulence genes were determined by PCR. The prevalence of K. pneumoniae was 26.94% (239/887) distributed in 101 wzi allele types (199/239, 83.26%) and 100 sequence types (STs) (209/239, 87.45%), including 5 new wzi allele type and 25 new STs. Phylogenetic analysis showed that K. pneumoniae isolated from milk, nipple swab, feed, and feces is classified in the same clone complex. By comparing with the PubMLST database, at least 67 STs have the risk of spreading in different species and regions. Interestingly, 60 STs have been isolated from humans. The isolates were highly sensitive to meropenem and colistin, but resistant to ampicillin (100%), sulfisoxazole (94.56%), cephalothin (47.28%), streptomycin (30.13%), and so on. Noteworthy, multidrug-resistant (MDR) rate was found to be 43.93% in this study. By PCR, 30 of 68 antimicrobial resistance (AMR) genes were identified; the prevalence rate of blaTEM, blaSHV, strA, strB, aadA1, and aac(6′)-Ib-cr was more than 50%. Eleven CTX-M-producing K. pneumoniae were found. The detection rate of fimH, mrkD, uge, wabG, entB, iutA, iroN, and ureA was over 85%. This study reinforces the epidemiological importance of K. pneumoniae in food-producing animals in Hubei. The emergence and spread of environmental MDR K. pneumoniae may pose a potential threat to food safety and public health.

Disinfecting Action of Gaseous Ozone on OXA-48-Producing Klebsiella pneumoniae Biofilm In Vitro

Klebsiella pneumoniae is an emerging multidrug-resistant pathogen that can contaminate hospital surfaces in the form of a biofilm which is hard to remove with standard disinfectants. Because of biofilm resistance to conservative disinfectants, the application of new disinfection technologies is becoming more frequent. Ozone gas has antimicrobial activity but there is lack of data on its action against K. pneumoniae biofilm. The aim of this study was to investigate the effects and mechanisms of action of gaseous ozone on the OXA-48-procuding K. pneumoniae biofilm. A 24 h biofilm of K. pneumoniae formed on ceramic tiles was subsequently exposed to different concentrations of ozone during one and two hours to determine the optimal ozone concentration. Afterwards, the total bacteria count, total biomass and oxidative stress levels were monitored. A total of 25 ppm of gaseous ozone was determined to be optimal ozone concentration and caused reduction in total bacteria number in all strains of K. pneumoniae for 2.0 log₁₀ CFU/cm², followed by reduction in total biomass up to 88.15%. Reactive oxygen species levels significantly increased after the ozone treatment at 182% for the representative K. pneumoniae NCTC 13442 strain. Ozone gas in the concentration of 25 ppm caused significant biofilm reduction but did not completely eradicate the K. pneumoniae biofilm formed on ceramics. In conclusion, ozone gas has great potential to be used as an additional hygiene measure in joint combat against biofilm in hospital environments.

Identification of a phage-derived depolymerase specific for KL47 capsule of Klebsiella pneumoniae and its therapeutic potential in mice

Klebsiella pneumoniae is one of the major pathogens causing global multidrug-resistant infections. Therefore, strategies for preventing and controlling the infections are urgently needed. Phage depolymerase, often found in the tail fiber protein or the tail spike protein, is reported to have antibiofilm activity. In this study, phage P560 isolated from sewage showed specific for capsule locus type KL47 K. pneumoniae, and the enlarged haloes around plaques indicated that P560 encoded a depolymerase. The capsule depolymerase, ORF43, named P560dep, derived from phage P560 was expressed, purified, characterized and evaluated for enzymatic activity as well as specificity. We reported that the capsule depolymerase P560dep, can digest the capsule polysaccharides on the surface of KL47 type K. pneumoniae, and the depolymerization spectrum of P560dep matched to the host range of phage P560, KL47 K. pneumoniae. Crystal violet staining assay showed that P560dep was able to significantly inhibit biofilm formation. Further, a single dose (50 μg/mouse) of depolymerase intraperitoneal injection protected 90%–100% of mice from lethal challenge before or after infection by KL47 carbapenem-resistant K. pneumoniae. And pathological changes were alleviated in lung and liver of mice infected by KL47 type K. pneumoniae. It is demonstrated that depolymerase P560dep as an attractive antivirulence agent represents a promising tool for antimicrobial therapy.

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Phage-derived depolymerase P560dep can digest KL47 capsule polysaccharides of CRKP.

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Depolymerase P560dep showed antibiofilm activity, preventive and protective effects of CRKP infection in lethal mouse models.

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Depolymerase P560dep as an attractive anti-virulence agent represents a promising tool for antimicrobial therapy.

Metabolic properties, gene functions, and biosafety analysis reveal the action of three rhizospheric plant growth-promoting bacteria of Jujuncao (Pennisetum giganteum)

This study aimed to identify the specific genes associated with plant growth promotion and cadmium tolerance in three bacteria strains associated with Pennisetum giganteum as well as to determine their biosafety levels in their potential use as biofertilizers for promoting plant growth and phytoremediation activities. The plant growth-promoting (PGP) abilities of Enterobacter cloacae strain RCB980 (A3), Klebsiella pneumonia strain kpa (A4), and Klebsiella sp. strain XT-2 (A7) were determined by a growth promotion trial and through testing for PGP traits such as 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzyme production, phosphorus solubilization, siderophore synthesis, and indole-3 acetic acid (IAA) production. The genes that potentially contribute to the beneficial activities of these three strains were identified through an analysis of their genomes. To establish the biosafety of the candidate PGPB, a pathological study was undertaken whereby 20 Kunming mice were injected intraperitoneally to study and analyze the effects of the strains on growth and lung paraffin sections of the mice. The strains had no obvious toxicity effect on the tested mice and were therefore not considered as highly virulent strains. These strains are thus considered non-toxic, safe, and highly recommended for use in environmental remediation strategies and agricultural production.

Presence and absence of type VI secretion systems in bacteria

The type VI secretion system (T6SS) is a molecular puncturing device that enables Gram-negative bacteria to kill competitors, manipulate host cells and take up nutrients. Who would want to miss such superpowers? Indeed, many studies show how widespread the secretion apparatus is among microbes. However, it is becoming evident that, on multiple taxonomic levels, from phyla to species and strains, some bacteria lack a T6SS. Here, we review who does and does not have a type VI secretion apparatus and speculate on the dynamic process of gaining and losing the secretion system to better understand its spread and distribution across the microbial world.

High mortality from carbapenem-resistant Klebsiella pneumoniae bloodstream infection

In this study, it was evaluated clinical data of 107 patients with bloodstream infection (BSI) by Klebsiella pneumoniae and performed phenotypic and molecular analyzes in 50.5% (54/107) of the samples, those that showed a resistance profile to carbapenemics. The bla_KPC gene was present in 90.4% (49/54) of the samples, bla_NDM gene in one sample and, in 7.4% (4/54) of the samples, no carbapenemase gene was found. In the similarity analysis, it was found 4 main clones and 11 samples were not genetically related. The median age of the patients was 58 (40-70) years old and 60.7% (65/107) were male. When comparing two groups of patients with BSI due to K. pneumoniae with and without resistance to carbapenems, the variables ICU permanence, renal failure (IR), previous use of antimicrobials, Charlson's comorbidity index (ICCi), some invasive procedures and death showed a statistically significant difference (p < 0.05). And when relating death as a dependent variable, IR, liver failure and patients with BSI XDR or PDR, were predictors of increased mortality. Our study showed a higher mortality rate in patients with BSI due to carbapenem-resistant pneumonia with additional resistance or not to polymyxins.

Biotyping, Virulotyping and Biofilm Formation Ability of ESBL-Klebsiella pneumoniae Isolates from Nosocomial Infections

The aim of this study was to investigate the frequency, molecular characterization, virulence genes, resistance genes and antimicrobial profile of nosocomial extended spectrum beta lactamase producing Klebsiella species. A total of 22 (12.2%) K. pneumoniae strains were isolated from 180 clinical samples collected from hospitalized patients in Egypt. K. pneumoniae biotypes were B1 (72.8%), B3 (13.6%) and B4 (13.6%). The isolates were classified for the capsular serotypes, 86.4% (20/22) were of K1 serotype, while only two isolates (13.64%) were of K2 serotype. Hypermucoviscous K. pneumoniae isolates accounted for 68.2%. Biofilm formation ability of K. pneumoniae was determined by microtitre plate method. The majority of the isolates (40.9%) were moderate biofilm producers, while 27.3% were strong biofilm producers. All K. pneumoniae strains were positive for fimH and traT genes, while magA was identified in only 63.6% of the isolates. The antibiotic susceptibility profile of the isolates (n=22) was determined by the disc diffusion technique using 23 different antibiotics. Streptomycin and imipenem are the most effective antibiotics against 22 tested K. pneumoniae isolates with sensitivity rates of 63.64% and 54.54%, respectively. All tested K. pneumoniae isolates showed high resistance to amoxicillin∕clavulanate (100%), cefuroxime (100%) and ceftazidime (95.45%). Extended spectrum beta lactamases (ESBL) production and the presence of ESBL related genes were tested in the isolates. All the isolates tested positive for blaVIM, NDM1, and blaTEM, while only 81.8 percent tested positive for the blaSHV gene. Increasing antimicrobial resistance in K. pneumoniae causing nosocomial infections limits the use of antimicrobial agents for treatment. Furthermore, the spread of biofilm, multiple drug resistant and ESBL-producing K. pneumoniae isolates is a public threat for hospitalized patients.

Virulence Genotype and Correlation of Clinical Severeness with Presence of the Type VI Secretion System in Klebsiella pneumoniae Isolates Causing Bloodstream Infections

Background

Klebsiella pneumoniae (K. pneumoniae) causes bloodstream infection (BSI), which is responsible for a high rate of morbidity and mortality among different populations. In mainland China, data on the correlation and features of the type VI secretion system (T6SS) gene cluster in K. pneumoniae is currently scarce. As a result, we conducted a prospective investigation to determine the involvement of the T6SS in K. pneumoniae pathogenicity and antibiotic resistance.

Methods

In this prospective analysis, we enrolled 119 individuals who had been diagnosed with K. pneumoniae bloodstream infection between July 2019 and January 2021 and acquired demographic and clinical data from their medical records. The virulence genes rmpA, rmpA2, aerobactin, iroB, hcp, vgrG, and icmF were tested for K1 and K2, antimicrobial susceptibility. Five T6SS-positive and five T6SS-negative isolates were chosen for the competition, serum resistance, and biofilm formation experiments to further gain insights regarding the microbiological properties of T6SS-positive K. pneumoniae isolates.

Results

Among 119 isolates obtained from patients with BSIs, 20 (16.8%) were T6SS positive K. pneumoniae. T6SS positive strains had four virulence genes and a greater K1 capsular serotypes rate than T6SS negative bacteria. Among hvKP isolates, the T6SS positive rate was substantially greater than the T6SS negative rate (P = 0.001). T6SS-positive K. pneumoniae strains had a lower rate of antimicrobial resistance in comparison to T6SS-negative bacteria. T6SS-positive isolates may be more competitive with Escherichia coli than T6SS-negative isolates. T6SS-positive isolates, on the other hand, did not show stronger biofilm-forming activity or a higher survival rate in the presence of normal human serum in comparison to T6SS-negative isolates.

Conclusion

T6SS-positive K. pneumoniae was common in people who had BSIs. In T6SS‐containing K. pneumoniae, the system may play a major role in bacterial competition.

The invasive Klebsiella pneumoniae syndrome: Case series

This case-series aims to report three cases of endogenous endophthalmitis due to invasive Klebsiella pneumoniae syndrome.

Case 1

A 34-year-old lady who was admitted for pneumonia developed painful blurring of vision and redness in the right eye (RE) for one week. An examination of the RE revealed visual acuity (VA) of light perception (PL) with positive relative afferent pupillary defect (RAPD), proptosis, and restriction of extraocular movement with hypopyon. The patient was treated for RE panophthalmitis with a lung abscess and was started on systemic and topical antibiotics. The vitreous tap culture grew Klebsiella pneumoniae. Despite treatment, the patient's condition deteriorated, and evisceration was undertaken.

Case 2

A 38-year-old lady presented with a acute onset of RE pain associated with blurred vision and redness for two days, and fever for one week. RE VA was hand movement with a positive RAPD and anterior chamber cells of 2+. A B-scan revealed a dome-shaped subretinal mass with exudative retinal detachment. The patient was treated for RE panophthalmitis complicated by a basal ganglia abscess. The urine and vitreous tap cultures grew Klebsiella pneumoniae. She responded to high-dose intravenous and intravitreal antibiotics. Unfortunately, her RE became phthisical.

Case 3

A 70-year-old lady presented with painless blurring of vision over the RE. The blood and urine cultures grew Klebsiella pneumoniae. RE VA was PL, and she was treated for endogenous endophthalmitis. The vitreous culture grew Klebsiella pneumoniae. Unfortunately, the RE became phthisical.

Prevalence and antibiotic resistance of Klebsiella pneumoniae in a tertiary hospital in Hangzhou, China, 2006-2020

Objective

This study analyzed the characteristics and tendencies of resistance to common antibiotics for Klebsiella pneumoniae to provide a basis for clinical treatment and prevention.

Methods

A total of 71,743 isolates were collected from hospital clinical specimens following standard procedures from 2006 to 2020. Statistical analyses were conducted on laboratory test results.

Results

A total of 3054 isolates of K. pneumoniae were mainly isolated from sputum (53.77%), urine (14.70%), and blood (8.42%). Isolation rates of strains in the AIDS, hepatology, and intensive care wards were 9.72%, 12.52%, and 16.45%, respectively. Resistance rates of imipenem, cefazolin, gentamicin, tobramycin, ciprofloxacin, and ceftazidime respectively increased from 2.33%, 27.91%, 16.28%, 13.95%, 18.60%, and 9.30% to 12.83%, 40.82%, 21.57%, 25.07%, 44.61%, and 17.78%, while piperacillin–tazobactam resistance decreased from 13.95% to 13.70%. Differences in resistance rates to seven antibiotics were significant among specimen types. Detection rates of carbapenem-resistant K. pneumoniae were significantly different among blood, sputum, and urine specimens, and between wards.

Conclusions

The prevalence and drug resistance of K. pneumoniae showed an upward trend over time, and resistance varied according to ward and specimen source. The prevention of nosocomial infections and rational drug use must be emphasized to reduce antimicrobial resistance.

Development of Loop-Mediated Isothermal Amplification Rapid Diagnostic Assays for the Detection of Klebsiella pneumoniae and Carbapenemase Genes in Clinical Samples

Klebsiella pneumoniae is an important pathogenic bacterium commonly associated with human healthcare and community-acquired infections. In recent years, K. pneumoniae has become a significant threat to global public and veterinary health, because of its high rates of antimicrobial resistance (AMR). Early diagnosis of K. pneumoniae infection and detection of any associated AMR would help to accelerate directed therapy and reduce the risk of the emergence of multidrug-resistant isolates. In this study, we identified three target genes (yhaI, epsL, and xcpW) common to K. pneumoniae isolates from both China and Europe and designed loop-mediated isothermal amplification (LAMP) assays for the detection of K. pneumoniae in clinical samples. We also designed LAMP assays for the detection of five AMR genes commonly associated with K. pneumoniae. The LAMP assays were validated on a total of 319 type reference strains and clinical isolates of diverse genetic backgrounds, in addition to 40 clinical human sputum samples, and were shown to be reliable, highly specific, and sensitive. For the K. pneumoniae–specific LAMP assay, the calculated sensitivity, specificity, and positive and negative predictive values (comparison with culture and matrix-assisted laser desorption/ionization–time of flight mass spectrometry) were all 100% on clinical isolates and, respectively, of 100%, 91%, and 90%, and 100% when tested on clinical sputum samples, while being significantly faster than the reference methods. For the bla_KPC and other carbapenemases’ LAMP assays, the concordance between the LAMP results and the references methods (susceptibility tests) was 100%, on both pure cultures (n = 125) and clinical samples (n = 18). In conclusion, we developed highly sensitive and specific LAMP assays for the clinical identification of K. pneumoniae and detection of carbapenem resistance.

Bacterial profile, antimicrobial susceptibility patterns, and associated factors of community-acquired pneumonia among adult patients in Gondar, Northwest Ethiopia: A cross-sectional study

Introduction

Community-acquired pneumonia is associated with higher morbidity, hospitalization, and mortality in adults. Likewise, antimicrobial resistance has increased in recent decades in Ethiopia. Therefore, this study was aimed to determine the bacterial isolates, their antimicrobial susceptibility patterns, and factors associated with community-acquired pneumonia among adult patients in Gondar, Northwest Ethiopia.

Materials and methods

This institutional-based cross-sectional study was conducted from April to June 2021. Sociodemographic, clinical, and other relevant data were collected using a pre-tested questionnaire. A total of 312 sputum specimens were collected using sputum cups and inoculated into blood agar, chocolate agar, mannitol salt agar, and MacConkey agar plates, which were then incubated at 37°C for 24 hours. The bacterial isolates were identified based on Gram staining, colony characteristics, and biochemical tests. Antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method. Inducible clindamycin resistance among the S. aureus isolates was detected by the D-test. Data were entered using EPI data version 4.6 and analyzed using SPSS version 20. P-value ≤ 0.05 at 95% CI was considered statistically significant.

Results

Of 312 cases, 39.4% (n = 123; 95% CI: 34.1%–44.9%) were found to have culture-confirmed pneumonia. The most common isolates were K. pneumoniae (31.0%, n = 39), S. pneumoniae (26.2%, n = 33), and S. aureus (20.6%, n = 26). The gram-positive bacteria were susceptible to chloramphenicol (100%) and clindamycin (96.6%). Gram-negative bacteria were susceptible to gentamicin (87.5%), azithromycin (87.1%), ciprofloxacin (86.6%), and ceftriaxone (79.0%) but highly resistant to ampicillin (100%), followed by tetracycline (87.1%), doxycycline (86.4%), co-trimoxazole (80.6%), and amoxicillin-clavulanic acid (79.0%). Overall, 72.2% of the isolates were multi-drug resistant to K. pneumoniae (94.9%, n = 37), E. coli (93.8%, n = 15), and S. pneumoniae (72.7%, n = 24). Only, 7.7% of S. aureus isolates showed inducible clindamycin resistance. Aging (AOR: 3.248, 95% CI: 1.001–10.545, p = 0.050), a history of pneumonia (AOR: 7.004, 95% CI: 3.591–13.658, p = 0.001), alcohol use (AOR: 6.614, 95% CI: 3.399–12.872, p < 0.001), and overcrowded living conditions (AOR: 4.348, 95% CI: 1.964–9.624, p = 0.001) were significantly associated with culture-positive sputum.

Conclusion and recommendations

This study found a high prevalence of bacteria-caused community-acquired pneumonia among adults and low susceptibility to ampicillin, tetracyclines, and amoxicillin-clavulanic acid. Therefore, culture-based bacterial identification and local antibiotic susceptibility testing should be performed regularly. Additionally, new insights into vaccine coverage against highly multi-drug resistant bacteria, particularly K. pneumoniae, are necessary.

Mechanisms regulating the airborne survival of Klebsiella pneumoniae under different relative humidity and temperature levels

In this study, Klebsiella pneumoniae was suspended in synthetic saliva in a nebulizer (N₀ ) and nebulized for 5 min (N₅ ) into an aerosol chamber and further prolonged in the aerosolization phase for 15 min (A₁₅ ) under four different conditions: 20°C, 50% relative humidity (RH); 20°C, 80% RH; 30°C, 50% RH; and 30°C, 80% RH. Samples were collected at N₀ , N₅ , and A₁₅ , then subjected to survival analysis and comparative transcriptomic analysis in order to help elucidate the underlying mechanisms of airborne survival. Survival analysis shows that a higher humidity and lower temperature were favorable for the airborne survival of K. pneumoniae, and the effect of RH was more remarkable at 20°C than that at 30°C. The RNA-seq results show that during the nebulization phase (N₀ vs. N₅ ), a total number of 201 differentially expressed genes (DEGs) were identified (103 downregulated and 98 upregulated). Comparison between nebulization and aerosolization phases (N₅ vs. A₁₅ ) indicates up to 132 DEGs, with 46 downregulated and 86 upregulated. The most notable groups of genes are those involved in cellular remodeling, metabolism and energy processes. Alarmingly, the mbl gene, which encodes antibiotic resistance in K. pneumoniae, was upregulated during the suspension phase under all the tested conditions. This study provides insights into the control of airborne transmitted diseases.

Structural characterization of the urease accessory protein UreF from Klebsiella pneumoniae

Klebsiella pneumoniae is an opportunistic pathogen that mostly affects those with weakened immune systems. Urease is a vital enzyme that can hydrolyze urea to ammonia and carbon dioxide as a source of nitrogen for growth. Urease is also a K. pneumoniae virulence factor that enables survival of the bacterium under nutrient-limiting conditions. UreF, an important nickel-binding urease accessory protein, is involved in the insertion of Ni²⁺ into the active site of urease. Here, the crystal structure of UreF from K. pneumoniae (KpUreF) is reported. Functional data show that KpUreF forms a stable dimer in solution. These results may provide a starting point for the design of urease inhibitors.

The pathogenesis of prevalent aerobic bacteria in aerobic vaginitis and adverse pregnancy outcomes: a narrative review

Background

Aerobic vaginitis is a common cause of vaginal discharge in reproductive-age women, increasing the risk of negative pregnancy outcomes such as premature delivery, abortion, premature rupture of membranes and stillbirth. However, the aetiology and pathogenesis of aerobic vaginitis causing negative pregnancy outcomes are still unclear, and there is no unified and standardized treatment method for aerobic vaginitis in the pregnancy period.

Methods

We conducted a literature search of published studies in the English language focusing on aerobic vaginitis and its association with adverse pregnancy outcomes utilizing PubMed and Web of Science from January 1973 through June 2021. The common pathogenic bacteria of aerobic vaginitis during pregnancy, such as group B Streptococcus, Escherichia coli, Staphylococcus aureus, Enterococcus faecalis and Klebsiella pneumoniae, as well as the related adverse pregnancy outcomes and existing treatments were reviewed.

Results

A total of 4534 articles were identified, and 97 studies that had inclusion criteria were subjected to careful review. The pathogenic bacteria of aerobic vaginitis can produce different toxins or affect the local immunity of patients and then lead to the occurrence of infection. Fresh wet mount microscopy is the preferred diagnostic method for aerobic vaginitis. Clindamycin is a common antibiotic used for aerobic vaginitis in pregnant women. The use of products combining probiotics has achieved excellent treatment success.

Conclusions

Future research in this field can provide insights regarding the mechanism of aerobic vaginitis-induced adverse pregnancy outcomes in humans and ways to prevent their occurrence.

Aerobic vaginitis is an infection of the vagina that increases the risk of negative pregnancy outcomes. The aetiology and pathogenesis of aerobic vaginitis causing negative pregnancy outcomes are still unclear. This paper reviews the common pathogenic bacteria of aerobic vaginitis during pregnancy, and the related adverse pregnancy outcomes. We also review the existing treatment. Currently, it is believed that the microflora in aerobic vaginitis is composed of commensal aerobic microorganisms of intestinal origin, and the most frequently encountered bacteria are group B Streptococcus, Escherichia coli, Staphylococcus aureus, Enterococcus faecalis and Klebsiella pneumoniae. The pathogenic bacteria of aerobic vaginitis can produce different toxins or affect the local immunity of patients and then lead to the occurrence of infection. Fresh wet mount microscopy is the preferred diagnostic method for aerobic vaginitis. Clindamycin is a common antibiotic used for aerobic vaginitis in pregnant women. The use of products combining probiotics has achieved excellent treatment success. This study provides a reference for future research and early diagnosis and treatment during pregnancy. Future research in this field can provide insights regarding the mechanisms of aerobic vaginitis-induced adverse pregnancy outcomes in humans and ways to prevent their occurrence.

COVID-19 Pulmonary Pathology, Ventilator-Induced Lung Injury (VILI), or Sepsis-Induced Acute Respiratory Distress Syndrome (ARDS)? Healthcare Considerations Arising From an Autopsy Case and Miny-Review

Acute respiratory distress syndrome (ARDS) caused by coronavirus disease (COVID-19) is a serious complication that requires early recognition. Autopsy reports or biopsies of the lungs in patients with COVID-19 revealed diffuse alveolar damage (DAD) at different stages; the fibrotic phase is usually associated with long-standing severe disease. Care management of hospitalized patients is not easy, given that the risk of incurring a ventilator-induced lung injury (VILI) is high. Additionally, if the patient develops nosocomial infections, sepsis-induced ARDS should be considered in the study of the pathophysiological processes. We present an autopsy case of a hospitalized patient whose death was linked to COVID-19 infection, with the histopathological pattern of advanced pulmonary fibrosis. After prolonged use of non-invasive and invasive ventilation, the patient developed polymicrobial superinfection oh the lungs. After analyzing the individual’s clinical history and pulmonary anatomopathological findings, we consider healthcare issues that should lead to an improvement in diagnosis and to more adequate standards of care management among health professionals.

Phenotypic and genetic characteristics of antimicrobial resistance of Klebsiella pneumoniae clinical isolates in hospitals of Nizhny Novgorod

Objective. To study in vitro antimicrobial resistance and prevalence of the most clinically important carbapenemases genes in Klebsiella pneumoniae clinical isolates in Nizhny Novgorod. Materials and Methods. A total of 238 K. pneumoniae clinical isolates from upper and lower respiratory tracts, abdominal cavity, urogenital tract, and wound discharge were tested in this study. Species identification was done using WalkAway 96 analyzer (Siemens, Germany) with POS Combo Type 20 tablets (Beckman Coulter, USA) and Multiscan FC spectrophotometer (Thermo Scientific, Finland) with Microlatest tablets (PLIVA-Lachema, Czech Republic). Antimicrobial resistance was determined by discdiffusion method and using microbiological analyzer WalkAway 96 (Siemens, Germany). Minimal inhibitory concentrations for colistin were determined using the “MIC Colistin” kit (Erba Mannheim, Czech Republic). Detection of carbapenemases genes (KPC, OXA-48 group, IMP, VIM and NDM) was performed by RT-PCR using CFX-96 machine (Bio-Rad, USA) and commercial kits «MDR KPC/OXA-48-FL» and «MDR MBL-FL» (AmpliSens, Russia). Results. More than 90% of K. pneumoniae isolates in Nizhny Novgorod were resistant to III–V generation cephalosporins, 53.8% – to gentamicin, 71.2% – to ciprofloxacin, 81.2% – to co-trimoxazole, 88.1% – to ertapenem, 37.1% – to doripenem, 21.6% – to imipenem, 34.3% – to meropenem, 3.2% – to colistin. Genes of КРС-like carbapenemases were detected in 13.1% of isolates, OХA-48 – in 21.6%. Metallobeta-lactamases were not identified among tested isolates. Conclusions. Currently, there are no antimicrobials that active against all K. pneumoniae isolates in Nizhny Novgorod. Carbapenems and polymyxins remain active against more than 50% of isolates.

Genetic Diversity, Antimicrobial Resistance Pattern, and Biofilm Formation in Klebsiella pneumoniae Isolated from Patients with Coronavirus Disease 2019 (COVID-19) and Ventilator-Associated Pneumonia

Introduction

Patients with acute respiratory distress syndrome caused by coronavirus disease 2019 (COVID-19) are at risk for superadded infections, especially infections caused by multidrug resistant (MDR) pathogens. Before the COVID-19 pandemic, the prevalence of MDR infections, including infections caused by MDR Klebsiella pneumoniae (K. pneumoniae), was very high in Iran. This study is aimed at assessing the genetic diversity, antimicrobial resistance pattern, and biofilm formation in K. pneumoniae isolates obtained from patients with COVID-19 and ventilator-associated pneumonia (VAP) hospitalized in an intensive care unit (ICU) in Iran.

Methods

In this cross-sectional study, seventy K. pneumoniae isolates were obtained from seventy patients with COVID-19 hospitalized in the ICU of Shahid Beheshti hospital, Kashan, Iran, from May to September, 2020. K. pneumoniae was detected through the ureD gene. Antimicrobial susceptibility testing was done using the Kirby-Bauer disc diffusion method, and biofilm was detected using the microtiter plate assay method. Genetic diversity was also analyzed through polymerase chain reaction based on enterobacterial repetitive intergenic consensus (ERIC-PCR). The BioNumerics software (v. 8.0, Applied Maths, Belgium) was used for analyzing the data and drawing dendrogram and minimum spanning tree. Findings. K. pneumoniae isolates had varying levels of resistance to antibiotics meropenem (80.4%), cefepime-aztreonam-piperacillin/tazobactam (70%), tobramycin (61.4%), ciprofloxacin (57.7%), gentamicin (55.7%), and imipenem (50%). Around 77.14% of isolates were MDR, and 42.8% of them formed biofilm. Genetic diversity analysis revealed 28 genotypes (E1-E28) and 74.28% of isolates were grouped into ten clusters (i.e., clusters A-J). Clusters were further categorized into three major clusters, i.e., clusters E, H, and J. Antimicrobial resistance to meropenem, tobramycin, gentamicin, and ciprofloxacin in cluster J was significantly higher than cluster H, denoting significant relationship between ERIC clusters and antimicrobial resistance. However, there was no significant difference among major clusters E, H, and J respecting biofilm formation.

Conclusion

K. pneumoniae isolates obtained from patients with COVID-19 have high antimicrobial resistance, and 44.2% of them have genetic similarity and can be clustered in three major clusters. There is a significant difference among clusters respecting antimicrobial resistance.

Antibacterial and antibiofilm efficacy of Ag NPs, Ni NPs and Al2O3 NPs singly and in combination against multidrug-resistant Klebsiella pneumoniae isolates

BACKGROUND

Although traditional antibiotic therapy provided an effective approach to combat pathogenic bacteria, the long-term and widespread use of antibiotic results in the evolution of multidrug-resistant bacteria. Recent progress in nanotechnology offers an alternative opportunity to discover and develop novel antibacterial agents.

METHODS

A total of 51 K. pneumoniae strains were collected from several specimens of hospitalized patients and identified by two parallel methods (biochemical tests and Vitek-2 system). The antibiotic sensitivity of isolates was evaluated by disk diffusion antibiogram and Vitek-2 system. The biofilms formation ability of antibiotic-resistant strains was examined by microtiter plate and tube methods based on crystal violet staining. The molecular technique was used to determine key genes responsible for biofilms formation of clinical isolates. The antibacterial and antibiofilm activities of Ag NPs, Ni NPs, Al₂O₃ NPs singly (NPs) and in combination (cNPs) were investigated against selected strains using standard methods. Moreover, the cytotoxicity of NPs was evaluated on mouse neural crest-derived (Neuro-2A) cell line.

RESULTS

The results of bacterial studies revealed that more than 80 % of the isolates were resistant to commonly used antibiotics and about 95 % of them were able to form biofilms. Moreover, the presence of fimA and mrkA genes were determined in all biofilm-producing strains. The results of antibacterial and antibiofilm activities of NPs and cNPs demonstrated the lower MIC and MBEC values for Al₂O₃ NPs singly as well as for Ag/Ni cNPs and Ag/Al₂O₃ cNPs in combination, respectively. Overall, the inhibitory effects of cNPs were superior to NPs against all strains. Furthermore, the results of the checkerboard assays showed that Ag NPs act synergistically with two other NPs against multidrug-resistant Klebsiella pneumoniae (MDR-K. pneumoniae) isolates. The in vitro cytotoxicity assay revealed no significant toxicity of NPs against Neuro-2A cells.

CONCLUSION

In the present study, the combination of Ag NPs, Ni NPs, and Al₂O₃ NPs were used against MDR-K. pneumoniae strains and antibacterial and antibiofilm activities were observed for Ag/Ni cNPs and Ag/Al₂O₃ cNPs.

Influence of LncRNA NKILA on Bloodstream Infection of Hypervirulent Klebsiella pneumoniae and Its Ability to Induce Delayed Neutrophil Apoptosis

Objective

Pneumonia due to hypervirulent Klebsiella pneumoniae (hvKP) is a high-risk subtype of pneumonia with high mortality and disability rates. An in-depth understanding of hvKP's pathogenic process and mechanism of action is the focus of achieving early disease diagnosis and early symptomatic treatment. This study conducted a preliminary analysis on the influence of lncRNA NKILA (NKILA) on hvKP, aiming at providing a new approach to the diagnosis and treatment of hvKP and laying a reliable foundation for subsequent NKILA-related studies.

Methods

Selected from our hospital from October 2016 to February 2018, 67 patients who were examined for the pathogenic microorganisms of alveolar lavage fluid were selected as the research subjects. Among them, 29 were diagnosed as hvKP (research group), and the other 38 had no pathogenic bacteria (control group). Serum and bronchoalveolar lavage fluid (BALF) NKILA and inflammatory factors were detected, and the clinical significance of NKILA was analyzed. In addition, neutrophils from research group were extracted and NKILA expression was increased to observe the alterations in cell apoptosis, respiratory burst intensity, and NF-kappa B inhibitor alpha (NF-κB) p65 protein.

Results

Serum and BALF levels of NKILA and inflammatory factors were higher in research group than in control group, and NKILA decreased in both cohorts after treatment (P < 0.05). NKILA had an excellent predictive effect on the occurrence of hvKP (P < 0.001) and was positively correlated with inflammatory factors (P < 0.05). Prognostic follow-up revealed that NKILA also had a good predictive value for death in hvKP patients (P < 0.05), and increased posttreatment levels predicted an increased risk of death (P < 0.05). In vitro, increased NKILA hindered the delayed apoptosis rate, decreased respiratory burst intensity of hvKP neutrophils, and activated NF-κB p65 protein (P < 0.05).

Conclusion

With an elevated expression profile in hvKP, NKILA can induce the delayed apoptosis of neutrophils, enhance the ability of releasing inflammatory mediators, and promote the progression of hvKP via activating NF-κB p65.

The Mutation in wbaP cps Gene Cluster Selected by Phage-Borne Depolymerase Abolishes Capsule Production and Diminishes the Virulence of Klebsiella pneumoniae

Klebsiella pneumoniae is considered one of the most critical multidrug-resistant pathogens and urgently requires new therapeutic strategies. Capsular polysaccharides (CPS), lipopolysaccharides (LPS), and exopolysaccharides (EPS) are the major virulence factors protecting K. pneumoniae against the immune response and thus may be targeted by phage-based therapeutics such as polysaccharides-degrading enzymes. Since the emergence of resistance to antibacterials is generally considered undesirable, in this study, the genetic and phenotypic characteristics of resistance to the phage-borne CPS-degrading depolymerase and its effect on K. pneumoniae virulence were investigated. The K63 serotype targeting depolymerase (KP36gp50) derived from Klebsiella siphovirus KP36 was used as the selective agent during the treatment of K. pneumoniae 486 biofilm. Genome-driven examination combined with the surface polysaccharide structural analysis of resistant mutant showed the point mutation and frameshift in the wbaP gene located within the cps gene cluster, resulting in the loss of the capsule. The sharp decline in the yield of CPS was accompanied by the production of a larger amount of smooth LPS. The modification of the surface polysaccharide layers did not affect bacterial fitness nor the insensitivity to serum complement; however, it made bacteria more prone to phagocytosis combined with the higher adherence and internalization to human lung epithelial cells. In that context, it was showed that the emerging resistance to the antivirulence agent (phage-borne capsule depolymerase) results in beneficial consequences, i.e., the sensitization to the innate immune response.

Type 3 Innate Lymphoid Cells as Regulators of the Host-Pathogen Interaction

Type 3 Innate lymphoid cells (ILC3s) have been described as tissue-resident cells and characterized throughout the body, especially in mucosal sites and classical first barrier organs such as skin, gut and lungs, among others. A significant part of the research has focused on their role in combating pathogens, mainly extracellular pathogens, with the gut as the principal organ. However, some recent discoveries in the field have unveiled their activity in other organs, combating intracellular pathogens and as part of the response to viruses. In this review we have compiled the latest studies on the role of ILC3s and the molecular mechanisms involved in defending against different microbes at the mucosal surface, most of these studies have made use of conditional transgenic mice. The present review therefore attempts to provide an overview of the function of ILC3s in infections throughout the body, focusing on their specific activity in different organs.

Immunoinformatics and molecular docking studies reveal a novel Multi-Epitope peptide vaccine against pneumonia infection

Pneumonia is a major endemic disease around the world, and an effective vaccine is the need of the hour to fight against the disease. When there are no appropriate antiviral and associated therapies available, vaccine development becomes even more essential. Therefore, in the present study, a variety of immunoinformatics techniques was utilized to develop a novel multi-epitope vaccine that targets the highly immunodominant type 3 fimbrial protein of Klebsiella pneumoniae, the causal organism for pneumonia. The putative B and T cell epitopes were predicted from the protein and screened for antigenicity, toxicity, allergenicity, and cross-reactivity with human proteomes. Subsequently, the selected epitopes were joined with the help of linkers to form a robust vaccine construct. In addition, an adjuvant was applied to the N-terminal of the construct to improve the immunogenicity of the vaccine. The physicochemical properties, solubility, the secondary and tertiary structure of the final vaccine were also established. MD simulations for 100 ns were employed to assess the stability of the vaccine-TLR-2 docked complex. The final vaccine was optimized and cloned in pET28a (+) vector with His-tag to achieve maximum vaccine protein expression for ease of purification. Immune simulation results indicated the potency of this vaccine candidate as a probable therapeutic agent. In conclusion, the overall results of various immunoinformatics tools and methods employed revealed that the constructed multi-epitope vaccine exhibits a high potential for stimulating both B and T-cells immune responses against pneumonia infection. However, experimental immunological studies are required to corroborate the viability of the novel multi-epitope construct as a commercial vaccine.

Whole Genome Sequencing of Pediatric Klebsiella pneumoniae Strains Reveals Important Insights Into Their Virulence-Associated Traits

Klebsiella pneumoniae is recognized as a common cause of nosocomial infections and outbreaks causing pneumonia, septicemia, and urinary tract infections. This opportunistic bacterium shows an increasing acquisition of antibiotic-resistance genes, which complicates treatment of infections. Hence, fast reliable strain typing methods are paramount for the study of this opportunistic pathogen’s multi-drug resistance genetic profiles. In this study, thirty-eight strains of K. pneumoniae isolated from the blood of pediatric patients were characterized by whole-genome sequencing and genomic clustering methods. Genes encoding β-lactamase were found in all the bacterial isolates, among which the bla_SHV variant was the most prevalent (53%). Moreover, genes encoding virulence factors such as fimbriae, capsule, outer membrane proteins, T4SS and siderophores were investigated. Additionally, a multi-locus sequence typing (MLST) analysis revealed 24 distinct sequence types identified within the isolates, among which the most frequently represented were ST76 (16%) and ST70 (11%). Based on LPS structure, serotypes O1 and O3 were the most prevalent, accounting for approximately 63% of all infections. The virulence capsular types K10, K136, and K2 were present in 16, 13, and 8% of the isolates, respectively. Phylogenomic analysis based on virtual genome fingerprints correlated with the MLST data. The phylogenomic reconstruction also denoted association between strains with a higher abundance of virulence genes and virulent serotypes compared to strains that do not possess these traits. This study highlights the value of whole-genomic sequencing in the surveillance of virulence attributes among clinical K. pneumoniae strains.

Current Stage in the Development of Klebsiella pneumoniae Vaccines

Klebsiella pneumoniae is a bacterium capable of colonizing mucous membranes, causing serious infections. Widespread antibiotic resistance in K. pneumoniae—either through intrinsic mechanisms or via acquisition from different species, especially in hospital environments—limits the therapeutic options against this pathogen, further aggravating the disease burden. To date, there are no vaccines available against K. pneumoniae infection. Although formulations based on capsular polysaccharides have been proposed, the high variability in capsular serotypes limits vaccine coverage. Recombinant vaccines based on surface exposed bacterial antigens are a promising alternative owing to their conservation among different serotypes and accessibility to the immune system. Many vaccine candidates have been proposed, some of which have reached clinical trials. The present review summarizes the current status of K. pneumoniae vaccine development. Different strategies including whole cell vaccines, outer membrane vesicles (OMVs), ribosome, polysaccharide, lipopolysaccharide (LPS), and protein-based formulations are discussed. The contribution of antibody and cell-mediated responses is also presented. In summary, K. pneumoniae vaccines are feasible and a promising strategy to prevent infections and to reduce the antimicrobial resistance burden worldwide.

The hypermucoviscosity of hypervirulent K. pneumoniae confers the ability to evade neutrophil-mediated phagocytosis

Hypervirulent Klebsiella pneumoniae (HvKP), which causes highly fatal infections, is a new threat to human health. In an attempt to investigate the underlying mechanisms of resistance to neutrophil-mediated killing and hence expression of high-level virulence by HvKP, we tested the binding affinity of HvKP strains to various types of human cells. Our data showed that HvKP exhibited weaker binding to both lung epithelial cells, intestinal Caco-2 cells and macrophages when compared to the classic, non-hypervirulent strains (cKP). Consistently, transconjugants that have acquired a rmpA or rmpA2-bearing plasmid were found to exhibit decreased adhesion to various types of human cells, and hence higher survival rate upon exposure to neutrophil cells. We further found that over production of hypermucoviscosity (HMV), but not capsular polysaccharide (CPS), contributed to the reduced binding and phagocytosis. The effect of hypermucoviscosity on enhancing HvKP virulence was further shown in human serum survival assays and animal experiments. Findings in this study therefore confirmed that rmpA/A2-mediated hypermucoviscosity in HvKP plays a key role in the pathogenesis of this organism through conferring the ability to evade neutrophil binding and phagocytosis.

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.

SdiA, a Quorum-Sensing Regulator, Suppresses Fimbriae Expression, Biofilm Formation, and Quorum-Sensing Signaling Molecules Production in Klebsiella pneumoniae

Klebsiella pneumoniae is a Gram-negative pathogen that has become a worldwide concern due to the emergence of multidrug-resistant isolates responsible for various invasive infectious diseases. Biofilm formation constitutes a major virulence factor for K. pneumoniae and relies on the expression of fimbrial adhesins and aggregation of bacterial cells on biotic or abiotic surfaces in a coordinated manner. During biofilm aggregation, bacterial cells communicate with each other through inter- or intra-species interactions mediated by signallng molecules, called autoinducers, in a mechanism known as quorum sensing (QS). In most Gram-negative bacteria, intra-species communication typically involves the LuxI/LuxR system: LuxI synthase produces N-acyl homoserine lactones (AHLs) as autoinducers and the LuxR transcription factor is their cognate receptor. However, K. pneumoniae does not produce AHL but encodes SdiA, an orphan LuxR-type receptor that responds to exogenous AHL molecules produced by other bacterial species. While SdiA regulates several cellular processes and the expression of virulence factors in many pathogens, the role of this regulator in K. pneumoniae remains unknown. In this study, we describe the characterization of sdiA mutant strain of K. pneumoniae. The sdiA mutant strain has increased biofilm formation, which correlates with the increased expression of type 1 fimbriae, thus revealing a repressive role of SdiA in fimbriae expression and bacterial cell adherence and aggregation. On the other hand, SdiA acts as a transcriptional activator of cell division machinery assembly in the septum, since cells lacking SdiA regulator exhibited a filamentary shape rather than the typical rod shape. We also show that K. pneumoniae cells lacking SdiA regulator present constant production of QS autoinducers at maximum levels, suggesting a putative role for SdiA in the regulation of AI-2 production. Taken together, our results demonstrate that SdiA regulates cell division and the expression of virulence factors such as fimbriae expression, biofilm formation, and production of QS autoinducers in K. pneumoniae.

Characterization of the Blood and Cerebrospinal Fluid Microbiome in Children with Bacterial Meningitis and Its Potential Correlation with Inflammation

Bacterial meningitis shows a higher incidence in children than adults, but signs may be scarce. Although some pathogenic microorganisms of meningitis from cerebrospinal fluid (CSF) have been reported, the signature of the representative microbiota in CSF and blood samples from patients remains incompletely revealed. To extend the understanding of the microbiome in patients, we recruited 32 children with bacterial meningitis, 30 undiagnosed infectious children, and 10 matched healthy individuals, which was followed by untargeted metagenomic next-generation sequencing (mNGS) and bioinformatic analysis. Our results showed that children with bacterial meningitis exhibited different microbiome signatures in their CSF and blood compared with undiagnosed and healthy children, and patients could be divided into varied subsets according to these signatures, including Escherichia coli, Klebsiella pneumoniae, Thermothelomyces thermophila, Lactobacillus acidophilus, and Staphylococcus haemolyticus. To further explore their potential role in patients’ conditions, we examined their correlation with clinical parameters. Importantly, microbiome signatures with compositional changes were correlated with the C-reactive protein (CRP) level in blood and granulocyte percentage in CSF. Moreover, the blood in subsets of patients with a predominance of Klebsiella pneumoniae could replace CSF as the main specimen for clinical monitoring.

IMPORTANCE This study revealed the microbial compositions in children with bacterial meningitis who were treated with antibiotics and made a comprehensive comparison between blood and CSF specimens for the risk and prognosis assessment. We found that microbiome signatures could distinguish patient subsets in the children and were correlated with the CRP level in blood and granulocyte percentage in CSF. The compositional changes in representative microbiota constituents could provide guidance for clinical monitoring and antibiotic intervention.

Detection of colistin-resistant populations prior to antibiotic exposure in KPC-2-producing Klebsiella pneumoniae clinical isolates

Although colistin is frequently regarded as the antibiotic of last resort in treating carbapenem-resistant Klebsiella pneumoniae, colistin heteroresistance may in part be associated with antibiotic treatment failure. However, we do not know how widespread the colistin heteroresistance is in carbapenem-resistant K. pneumoniae isolates. In this study, we performed colistin disc diffusion assays, E-tests, and population analysis profiling for KPC-2-producing K. pneumoniae isolates to identify colistin heteroresistance. Although no colistin-resistant colonies were detected by the disc diffusion test and E-test, a colistin-resistant subpopulation was identified in population analysis profiling in all colistin-susceptible, KPC-2-producing K. pneumoniae isolates. Colistin-resistant subpopulations were also identified even when isolates had no colistin exposure. The ratio of colistin-resistant subpopulations to the total population increased as the exposure concentration of colistin increased. In in vitro time-kill assays, regrowth was observed in all isolates after 2 h upon exposure to colistin. We identified common amino acid alterations in PhoQ, PhoP, and PmrB in colistin-resistant subpopulations from some isolates, but no substitutions were found in most resistant subpopulations from other isolates. In all colistin-resistant subpopulations, overexpression of PhoQ and PbgP was observed. In this study, we demonstrated that colistin heteroresistance may be common in KPC-2-producing K. pneumoniae isolates, which could not be detected in the disc diffusion method and E-test. Colistin heteroresistance may cause colistin treatment failure in part and may evolve into resistance. Thus, development of more reliable diagnostic methods is required to detect colistin heteroresistance.

Carbapenem-Resistant Klebsiella pneumoniae Infections in ICU COVID-19 Patients-A Scoping Review

Introduction: The spread of multidrug-resistant pathogens is a serious problem and challenge for the whole medical community. Carbapenem-resistant Klebsiella pneumoniae (CRKP) infections in immunocompromised patients have a severe course and may be fatal. Increasingly, these bacteria are exhibiting resistance to carbapenem antibiotics, which have been used as so-called drugs of last resort. The emergence of the new coronavirus and the pandemic that it has caused require changes to protect against the spread of the new SARS-CoV-2. These changes paradoxically may contribute to the spread of other infections. Methods: PubMed, Cochrane Library databases were searched using relevant keywords. A literature review of carbapenem-resistant Klebsiella pneumoniae infection in patients hospitalized for COVID-19 was conducted according to PRISMA recommendations. A written review protocol was not prepared. Results: 1016 studies in scientific databases were searched. After rejecting duplicate studies, 964 results were obtained. Inclusion and exclusion criteria were then applied, and studies were qualitatively analyzed. Finally, 11 studies were included in the review. The results of infected patients were from six countries. The prevalence of CRKP in Covid-19 patients ranged from 0.35–53%. The majority of CRKP infected patients were male (85%), with a mean age of 61 years. Among isolates, the predominant genes were KPC, OXY-48, CTX-M, TEM, NDM and SHV. Conclusion: The results presented in our review indicate the necessity of paying attention to carbapenem-resistant Klebsiella pneumoniae infections in patients with COVID-19. In order to prevent the increase of bacterial resistance, rational antibiotic therapy should be used, as well as continuous control and surveillance of hospital infections caused by multidrug-resistant organisms.