Epidemiology of Klebsiella oxytoca-associated diarrhea detected by Simmons citrate agar supplemented with inositol, tryptophan, and bile salts

Binary CuO\CoO nanoparticles inhibit biofilm formation and reduce the expression of papC and fimH genes in multidrug-resistant Klebsiella oxytoca

BACKGROUND AND AIM

Binary copper-cobalt oxide nanoparticles (CuO\CoO NPs) are modern kinds of antimicrobials, which may get a lot of interest in clinical application. This study aimed to detect the effect of the binary CuO\CoO NPs on the expression of papC and fimH genes in multidrug-resistant (MDR) isolates of Klebsiella oxytoca to reduce medication time and improve outcomes.

METHODS

Ten isolates of K. oxytoca were collected and identified by different conventional tests besides PCR. Antibiotic sensitivity and biofilm-forming ability were carried out. The harboring of papC and fimH genes was also detected. The effect of binary CuO\CoO nanoparticles on the expression of papC and fimH genes was investigated.

RESULTS

Bacterial resistance against cefotaxime and gentamicin was the highest (100%), while the lowest percentage of resistance was to amikacin (30%). Nine of the ten bacterial isolates had the ability to form a biofilm with different capacities. MIC for binary CuO\CoO NPs was 2.5 µg/mL. Gene expression of papC and fimH was 8.5- and 9-fold lower using the NPs.

CONCLUSION

Binary CuO\CoO NPs have a potential therapeutic effect against infections triggered by MDR K. oxytoca strains due to the NPs-related downregulation ability on the virulence genes of K. oxytoca.

Transmission of ST45 and ST2407 extended-spectrum β-lactamase-producing Klebsiella pneumoniae in neonatal intensive care units, associated with contaminated environments

OBJECTIVES

Given the increasing frequency of infections due to extended-spectrum β-lactamase (EBSL)-producing Klebsiella pneumoniae in humans over recent decades, infection control against this pathogen is of high importance.

METHODS

In this study, the transmission mode of ESBL-producing K. pneumoniae in neonatal intensive care units (NICU) was investigated. We collected K. pneumoniae isolates from patients admitted to the NICU and performed environmental screening of the NICU and nearby obstetrics department. All isolates were analysed using antimicrobial susceptibility testing, whole-genome sequencing, molecular typing, and antimicrobial and virulence determinant screening. The phylogenetic relationships of all the isolates were analysed using core-genome multi-locus sequence type and single-nucleotide polymorphism-based analysis, and their plasmids harbouring antimicrobial resistance genes in ST2407 were compared.

RESULTS

Eighteen K. pneumoniae isolates were collected, of which 10 isolates from patients belonged to ST45 and ST2407, and eight isolates from the environment belonged to various other clones. Although 80% and 100% of isolates from patients were ESBL-positive (bla_CTX-M-14 and bla_CTX-M-55) and possessed siderophores, respectively; fewer environmental isolates harboured antimicrobial resistance and virulence genes. For both ST45 and ST2407 isolates, the phylogenetic assessment revealed a close relationship between clinical and environmental isolates, indicating that bloodstream infections were associated with the contaminated environments.

CONCLUSIONS

Based on these results, the environmental prevalence of K. pneumoniae should be considered given its pathogenicity in humans. Early and active infection control measures could decrease the spread of multidrug-resistant K. pneumoniae.

Improved diagnosis of antibiotic-associated haemorrhagic colitis (AAHC) in faecal specimens by a new qualitative real-time PCR assay detecting relevant toxin genes of Klebsiella oxytoca sensu lato

OBJECTIVE

Toxin-producing Klebsiella oxytoca causes antibiotic-associated haemorrhagic colitis (AAHC). The disease-relevant cytotoxins tilivalline and tilimycine produced by certain K. oxytoca isolates are encoded by the non-ribosomal peptide synthetase genes A (npsA) and B (npsB). In this study, the new LightMix® Modular kit for the detection of relevant K. oxytoca sensu lato (s.l.) toxin genes was evaluated.

METHODS

DNA was extracted on the automated EMAG® platform. Amplification was done on the Light Cycler® 480 II instrument. In total, 130 residual faecal specimens collected from patients with antibiotic-associated diarrhoea were studied to determine the clinical sensitivity and specificity. Toxigenic culture served as reference method.

RESULTS

With the new kit, the limit of detection was 15 CFU/mL for all targets. For the pehX target specific to K. oxytoca s.l., 65 of 130 clinical specimens were positive, while toxin-specific targets (npsA/npsB) were positive in 47 of 130. The npsA/npsB PCR targets showed a clinical sensitivity of 100% (95%CI 80.5-100%) and a specificity of 73.5% (95%CI 64.3-81.3%) with a positive predictive value of 16.5% (95%CI 12.7-21.2%) and a negative predictive value of 100%.

CONCLUSION

Compared with culture, additional clinical specimens positive for K. oxytoca s.l. were detected with real-time PCR. The specificity of the toxin targets appears moderate due to the inferior sensitivity of the culture-based reference method. Since the developed assay is highly sensitive, it may be used as first-line method to improve the diagnosis of AAHC.

Klebsiella oxytoca Complex: Update on Taxonomy, Antimicrobial Resistance, and Virulence

Klebsiella oxytoca is actually a complex of nine species-Klebsiella grimontii, Klebsiella huaxiensis, Klebsiella michiganensis, K. oxytoca, Klebsiella pasteurii, Klebsiella spallanzanii, and three unnamed novel species. Phenotypic tests can assign isolates to the complex, but precise species identification requires genome-based analysis. The K. oxytoca complex is a human commensal but also an opportunistic pathogen causing various infections, such as antibiotic-associated hemorrhagic colitis (AAHC), urinary tract infection, and bacteremia, and has caused outbreaks. Production of the cytotoxins tilivalline and tilimycin lead to AAHC, while many virulence factors seen in Klebsiella pneumoniae, such as capsular polysaccharides and fimbriae, have been found in the complex; however, their association with pathogenicity remains unclear. Among the 5,724 K. oxytoca clinical isolates in the SENTRY surveillance system, the rates of nonsusceptibility to carbapenems, ceftriaxone, ciprofloxacin, colistin, and tigecycline were 1.8%, 12.5%, 7.1%, 0.8%, and 0.1%, respectively. Resistance to carbapenems is increasing alarmingly. In addition to the intrinsic bla_OXY, many genes encoding β-lactamases with varying spectra of hydrolysis, including extended-spectrum β-lactamases, such as a few CTX-M variants and several TEM and SHV variants, have been found. bla_KPC-2 is the most common carbapenemase gene found in the complex and is mainly seen on IncN or IncF plasmids. Due to the ability to acquire antimicrobial resistance and the carriage of multiple virulence genes, the K. oxytoca complex has the potential to become a major threat to human health.

Klebsiella oxytoca causes colonization resistance against multidrug-resistant K. pneumoniae in the gut via cooperative carbohydrate competition

Gut colonization with multidrug-resistant (MDR) bacteria enhances the risk of bloodstream infections in susceptible individuals. We demonstrate highly variable degrees of ex vivo colonization resistance against a carbapenem-resistant Klebsiella pneumoniae strain in human feces samples and subsequently isolate diverse K. oxytoca strains from protected donors. Several of these K. oxytoca strains reduce gut colonization of MDR K. pneumoniae strains in antibiotic-treated and gnotobiotic mouse models. Comparative analysis of K. oxytoca strains coupled with CRISPR-Cas9-mediated deletion of casA, a protein essential for utilization of selected beta-glucosides, identified competition for specific carbohydrates as key in promoting colonization resistance. In addition to direct competition between K. oxytoca and K. pneumoniae, cooperation with additional commensals is required to reestablish full colonization resistance and gut decolonization. Finally, humanized microbiota mice generated from K. pneumoniae-susceptible donors are protected by K. oxytoca administration, demonstrating the potential of commensal K. oxytoca strains as next-generation probiotics.

Evaluation of the Antidiarrheal and Antioxidant Effects of Some Chewing Sticks Commonly Used for Oral Hygiene in Ghana

Microbial etiology of diarrhea is a significant cause of death, especially in children in developing countries. The presence of microbes that are resistant to current treatment options for diarrhea suggests the need to find newer antimicrobial agents for treatment. Therefore, this study focused on investigating the antimicrobial effect of some Ghanaian chewing sticks commonly used for oral hygiene, Azadirachta indica, Garcinia afzelii, and Garcinia kola, against selected diarrhea-causing organisms. From the stem and bark of each plant, 70% methanolic extract was experimented on Salmonella and Shigella species, namely, Shigella sonnei, Shigella flexeneri, Salmonella typhinirium enterica, Salmonella typhi attenuated, and Klebsiella oxytoca for microbial susceptibility using the agar well diffusion method. Additionally, the antioxidant profile of the methanolic extracts were investigated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic) acid (ABTS) scavenging activities, and ferric-reducing antioxidant potential (FRAP) assays, while the total polyphenolic content was determined using the Folin–Ciocalteau reagent. G. afzelii and A. indica stem demonstrated the highest antimicrobial effect, inhibiting the growth of all test organisms. Additionally, the extracts demonstrated high antioxidant potential and were found to possess significant amounts of phenolic compounds. Therefore, methanolic extracts of G. afzelii and A. indica stem are promising candidates for the identification of safe novel compounds to mitigate diarrheal diseases.

Healthcare associated diarrhea, not Clostridioides difficile

PURPOSE OF REVIEW

The aim of this article is to review the epidemiology, cause, diagnostic evaluation, and management of healthcare-associated diarrhea (HCAD) with particular attention to current epidemiology and recent developments in diagnostics.

RECENT FINDINGS

Multiplex polymerase chain reaction gastrointestinal panels allow rapid detection of a wide array of potential enteropathogens but the role, yield, and utility of these tests have not been systematically assessed in patients with HCAD. Recent epidemiologic studies reaffirm that HCAD is predominantly a noninfectious condition most often caused by medications or underlying medical conditions, sometimes Clostridioides difficile, and occasionally viruses. Other infections are rare.

SUMMARY

Clinical assessment remains fundamental to the evaluation of HCAD and targeted testing for C. difficile is sufficient in most patients. Multiplex gastrointestinal panels may have a role in immunocompromised patients but more study is needed. Medication-induced diarrhea is common and underappreciated and not limited to antibiotics, laxatives, and enemas.

The Changing Face of the Family Enterobacteriaceae (Order: "Enterobacterales"): New Members, Taxonomic Issues, Geographic Expansion, and New Diseases and Disease Syndromes

The family Enterobacteriaceae has undergone significant morphogenetic changes in its more than 85-year history, particularly during the past 2 decades (2000 to 2020). The development and introduction of new and novel molecular methods coupled with innovative laboratory techniques have led to many advances. We now know that the global range of enterobacteria is much more expansive than previously recognized, as they play important roles in the environment in vegetative processes and through widespread environmental distribution through insect vectors. In humans, many new species have been described, some associated with specific disease processes. Some established species are now observed in new infectious disease settings and syndromes. The results of molecular taxonomic and phylogenetics studies suggest that the current family Enterobacteriaceae should possibly be divided into seven or more separate families. The logarithmic explosion in the number of enterobacterial species described brings into question the relevancy, need, and mechanisms to potentially identify these taxa. This review covers the progression, transformation, and morphogenesis of the family from the seminal Centers for Disease Control and Prevention publication (J. J. Farmer III, B. R. Davis, F. W. Hickman-Brenner, A. McWhorter, et al., J Clin Microbiol 21:46-76, 1985, https://doi.org/10.1128/JCM.21.1.46-76.1985) to the present.

Molecular typing of cytotoxin-producing Klebsiella oxytoca isolates by 16S-23S internal transcribed spacer PCR

Cytotoxin is one of the important pathogenic factors, which plays a role in the virulence of Klebsiella oxytoca. The aim of this study was to investigate molecular typing of clinical isolates of the cytotoxin-producing K. oxytoca using internal transcribed spacer (ITS) PCR. A total of 75 isolates of K. oxytoca were isolated from clinical samples; they were verified as K. oxytoca by standard microbiological tests and PCR. Production of toxin determines the cytotoxic effects on HEp-2 cells. The genetic diversity of isolates of the cytotoxin-producing K. oxytoca were defined by ITS-PCR. Of all the isolates investigated, five K. oxytoca strains isolated from stool cultures, two strains from blood samples, one strain from a wound and one strain isolated from urine had cytotoxic effects on HEp-2 cells. The ITS-PCR patterns showed genetic diversity among cytotoxin-producing isolates. The ITS-PCR method had good discriminatory power; performance of this method and interpretation of the results were easy and repeatable. Five genetic diversity patterns were identified by ITS-PCR.

Rapid characterisation of Klebsiella oxytoca isolates from contaminated liquid hand soap using mass spectrometry, FTIR and Raman spectroscopy

Microbiological monitoring of consumer products and the efficiency of early warning systems and outbreak investigations depend on the rapid identification and strain characterisation of pathogens posing risks to the health and safety of consumers. This study evaluates the potential of three rapid analytical techniques for identification and subtyping of bacterial isolates obtained from a liquid hand soap product, which has been recalled and reported through the EU RAPEX system due to its severe bacterial contamination. Ten isolates recovered from two bottles of the product were identified as Klebsiella oxytoca and subtyped using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI TOF MS), near-infrared Fourier transform (NIR FT) Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Comparison of the classification results obtained by these phenotype-based techniques with outcomes of the DNA-based methods pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST) and single nucleotide polymorphism (SNP) analysis of whole-genome sequencing (WGS) data revealed a high level of concordance. In conclusion, a set of analytical techniques might be useful for rapid, reliable and cost-effective microbial typing to ensure safe consumer products and allow source tracking.

Etiology and pathogenicity of bacterial isolates: a cross sectional study among diarrheal children below five years in central regions of Kenya

INTRODUCTION

Bacterial agents are among pathogens implicated to cause diarrhea in children resulting to huge mortality and morbidities. Bacterial etiologies causing diarrhea in children below five years are rarely investigated in Central Kenya, which would otherwise guide prescription and target health education.

METHODS

A cross-sectional study approach was applied on 163 randomly selected stool samples from children below five years who presented with diarrhea in Murang`a and Muriranja`s hospitals. The objective was to determine the bacterial agents of diarrhea. Enteric bacterial pathogens were cultured using appropriate media and identified. Statistical analyses were performed using STATA v.13. Chi-square or Fisher exact-test were used to check for evidence of relationship whenever applicable.

RESULTS

There were nearly equal distributions in gender 86 (52.8%) female vs. 77 (47.2%) male, majority (35.6%) aged between 0-12 months. Bacterial isolates were highly diverse in female than the male, children aged 49-60 months and least among those aged 0-12 months. A total of 188 bacterial isolates belonging to 11 genera were recovered. The predominant bacteria was nonpathogenic Escherichia coli 85 (45.2%), while 13 (6.9%) Escherichia coli were positive for virulence genes, including 8 (4.3%) positive for LT and STp Shiga-like or Enterotoxigenic Escherichia coli, 3 (1.6%) positive for eae and bfpA Enteropathogenic Escherichia coli and 2 (1.1%) positive for Enteroaggregative Escherichia coli gene. Others included: Salmonella 21 (11.2%), Pseudomonas 14 (7.4%), Shigella 14 (7.4%), Klebsiella 12 (6.4%), Aeromonas 8 (4.3%), Enterobacter 7 (3.7%), Proteus 8 (4.3%), Citrobactor 3 (1.6%), Yersinia 2 (1.1%) and Vibrio 1 (0.5%).

CONCLUSION

Salmonella was the major bacterial isolate and majority of the bacteria were statistically significant cause of diarrhea (p=0.001).

A tricyclic pyrrolobenzodiazepine produced by Klebsiella oxytoca is associated with cytotoxicity in antibiotic-associated hemorrhagic colitis

Cytotoxin-producing Klebsiella oxytoca is the causative agent of antibiotic-associated hemorrhagic colitis (AAHC). Recently, the cytotoxin associated with AAHC was identified as tilivalline, a known pentacyclic pyrrolobenzodiazepine (PBD) metabolite produced by K. oxytoca Although this assertion of tilivalline's role in AAHC is supported by evidence from animal experiments, some key aspects of this finding appear to be incompatible with toxicity mechanisms of known PBD toxins. We therefore hypothesized that K. oxytoca may produce some other uncharacterized cytotoxins. To address this question, we investigated whether tilivalline alone is indeed necessary and sufficient to induce cytotoxicity or whether K. oxytoca also produces other cytotoxins. LC-MS- and NMR-based metabolomic analyses revealed the presence of an abundant tricyclic PBD, provisionally designated kleboxymycin, in the supernatant of toxigenic K. oxytoca strains. Moreover, by generating multiple mutants with gene deletions affecting tilivalline biosynthesis, we show that a tryptophanase-deficient, tilivalline-negative K. oxytoca mutant induced cytotoxicity in vitro similar to tilivalline-positive K. oxytoca strains. Furthermore, synthetic kleboxymycin exhibited greater than 9-fold higher cytotoxicity than tilivalline in TC₅₀ cell culture assays. We also found that the biosynthetic pathways for kleboxymycin and tilivalline appear to overlap, as tilivalline is an indole derivative of kleboxymycin. In summary, our results indicate that tilivalline is not essential for inducing cytotoxicity observed in K. oxytoca-associated AAHC and that kleboxymycin is a tilivalline-related bacterial metabolite with even higher cytotoxicity.

Characterization and formulation into solid dosage forms of a novel bacteriophage lytic against Klebsiella oxytoca

AIM

To isolate and characterize bacteriophage lytic for the opportunistic pathogen Klebsiella oxytoca and their formulation into a range of solid dosage forms for in-vitro testing.

METHODS AND RESULTS

We report the isolation, genomic and functional characterization of a novel bacteriophage lytic for Klebsiella oxytoca, which does not infect the closely related Klebsiella pneumoniae. This bacteriophage was formulated into suppositories and troches and shown to be released and lyse underlying Klebsiella oxytoca bacteria in an in-vitro model. These bacteriophage formulations were stable for at least 49 days at 4°C.

CONCLUSIONS

The successful in-vitro assay of these formulations here suggests that they could potentially be tested in-vivo to determine whether such a therapeutic approach could modulate the gut microbiome, and control Klebsiella oxytoca overgrowth, during antibiotic therapy regimes.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study reports a novel bacteriophage specific for Klebsiella oxytoca which can be formulated into solid dosage forms appropriate for potential delivery in testing as a therapy to modulate gut microbiome during antibiotic therapies.

Practical Guidance for Clinical Microbiology Laboratories: Diagnosis of Bacterial Gastroenteritis

Bacterial gastroenteritis is a disease that is pervasive in both the developing and developed worlds. While for the most part bacterial gastroenteritis is self-limiting, identification of an etiological agent by bacterial stool culture is required for the management of patients with severe or prolonged diarrhea, symptoms consistent with invasive disease, or a history that may predict a complicated course of disease. Importantly, characterization of bacterial enteropathogens from stool cultures in clinical laboratories is one of the primary means by which public health officials identify and track outbreaks of bacterial gastroenteritis. This article provides guidance for clinical microbiology laboratories that perform stool cultures. The general characteristics, epidemiology, and clinical manifestations of key bacterial enteropathogens are summarized. Information regarding optimal specimen collection, transport, and processing and current diagnostic tests and testing algorithms is provided. This article is an update of Cumitech 12A (P. H. Gilligan, J. M. Janda, M. A. Karmali, and J. M. Miller, Cumitech 12A, Laboratory diagnosis of bacterial diarrhea, 1992).

Genotypes of Klebsiella oxytoca isolates from patients with nosocomial pneumonia are distinct from those of isolates from patients with antibiotic-associated hemorrhagic colitis

Klebsiella oxytoca acts as a pathobiont in the dysbiotic human intestinal microbiota, causing antibiotic-associated hemorrhagic colitis (AAHC), but it also infects other organs, resulting in pneumonia and urinary tract and skin infections. The virulence of K. oxytoca is still poorly understood. The production of a specific cytotoxin has been linked to AAHC pathogenesis. To investigate the clonal relationships of K. oxytoca with regard to clinical origin and virulence attributes, we established a multilocus sequence typing (MLST) method and analyzed 74 clinical K. oxytoca isolates from asymptomatic carriers and patients with AAHC, respiratory infections, and other infections. The isolates were phenotypically characterized, typed, and compared phylogenetically based on the sequences of seven housekeeping genes. MLST analysis yielded 60 sequence types, 12 of which were represented by more than one isolate. The phylogenetic tree distinguished clusters of K. oxytoca isolates between patients with AAHC and those with respiratory infections. Toxin-positive and -negative strains were observed within one sequence type. Our findings indicate that AAHC isolates share a genetic background. Interestingly, K. oxytoca isolates from nosocomial pneumonia showed a different genetic clustering, suggesting that these strains do not originate from the intestines or that they are specialized for respiratory tract colonization. Our results further indicate a polyphyletic origin and possible horizontal transfer of the genes involved in K. oxytoca cytotoxin production. This work provides evidence that K. oxytoca isolates colonizing the two main clinically relevant habitats (lower gastrointestinal [GI] tract and respiratory tract) of the human host are genetically distinct. Applications of this MLST analysis should help clarify the sources of nosocomial infections.

Clinical management and infection control of SARS: lessons learned

The outbreak of severe acute respiratory syndrome (SARS) in 2003 was the first emergence of an important human pathogen in the 21st century. Responding to the epidemic provided clinicians with extensive experience in diagnosing and treating a novel respiratory viral disease. In this article, we review the experience of the SARS epidemic, focusing on measures taken to identify and isolate patients, prevent the transmission of infection to healthcare workers and develop effective therapies. Lessons learned from the SARS epidemic will be especially important in responding to the current emergence of another highly pathogenic human coronavirus, the agent of Middle East respiratory syndrome (MERS), and to the recently emerging H7N9 influenza A virus in China. This paper forms part of a symposium in Antiviral Research on "From SARS to MERS: 10years of research on highly pathogenic human coronaviruses."

Management of an incident of failed sterilization of surgical instruments in a dental clinic in Hong Kong

BACKGROUND/PURPOSE

We describe an investigation of an incident of failed sterilization procedure in a dental clinic. We aim to illustrate the principles in performing such investigations and to highlight some of the important checkpoints in sterilization procedures.

METHODS

In response to this incident, proper sterilization of all equipment was performed immediately. On-site investigation was conducted by the investigation panel to identify the cause and risks, to coordinate post-exposure management in affected patients, and to make recommendations to prevent similar occurrence of such incidents in the future.

RESULTS

The incident was due to a rare lapse of monitoring during the autoclaving cycle. A total of 127 sources and 250 exposed patients were identified within 24 hours of the discovery of the incident for risk assessment and testing for blood-borne viruses, including hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV). A protocol was devised to manage the exposed patients against HBV, HCV, and HIV. Immunization and hyperimmune globulin for hepatitis B, and tetanus toxoids were given to the exposed patients where indicated. Exposed patients were followed-up for 6 months. We came to the decision that dating of instrument packages and signed documentation of each autoclave printout, color change of chemical indicators of each load and daily autoclave performance should be made mandatory with immediate effect.

CONCLUSION

Rapid response is extremely crucial in minimizing the impact of this incident and relieving the anxiety of the affected patients. Proper recording and documentation of autoclave cycles and regular auditing should be enforced to prevent similar incidents.

Clarithromycin-induced haemorrhagic colitis

Haemorrhagic colitis by Klebsiella oxytoca has been described as an antibiotic-associated colitis, particularly with the use of ampicillin. Here we report a patient with haemorrhagic colitis caused by K oxytoca after the use of clarithromycin. A 67-year-old Japanese woman with diabetes presented with mucobloody diarrhoea and abdominal pain. Stool culture grew K oxytoca. Colonoscopy showed the appearance of haemorrhagic colitis. Further history taking revealed that she had received a course of oral clarithromycin for upper respiratory tract infection. She had recovered by conservative treatment. We should be careful about gastrointestinal symptoms in patients on clarithromycin, which can cause haemorrhagic colitis associated with K oxytoca.