Prevalence of OmpK35 and OmpK36 porin expression in beta-lactamase and non-betalactamase- producing Klebsiella pneumoniae

Virulence, antimicrobial resistance, and molecular characteristics of carbapenem-resistant Klebsiella pneumoniae in a hospital in Shijiazhuang City from China

Carbapenem-resistant Klebsiella pneumoniae (CRKP), as one of the most common drug-resistant bacteria threatening human health, is hyper-resistant to multiple antimicrobial drugs and carbapenems, which can be dealt with only limited clinical treatment options. This study described the epidemiological characteristics of CRKP in this tertiary care hospital from 2016 to 2020. Specimen sources included blood, sputum, alveolar lavage fluid, puncture fluid, secretions from a burn wound, and urine. Among the 87 carbapenem-resistant strains, ST11 was the predominant isolate, followed by ST15, ST273, ST340, and ST626. These STs were in broad agreement with the STs defined by pulsed-field gel electrophoresis clustering analysis in discriminating clusters of related strains. Most CRKP isolates contained the blaKPC-2 gene, some isolates carried the blaOXA-1, blaNDM-1, and blaNDM-5 genes, and the isolates carrying carbapenem resistance genes were more resistant to the antimicrobials of β-lactams, carbapenems, macrolides, and fluoroquinolone. The OmpK35 and OmpK37 genes were detected in all CRKP strains, and the Ompk36 gene was detected in some CRKP strains. All detected OmpK37 had 4 mutant sites, and OmpK36 had 11 mutant sites, while no mutant sites were found in OmpK35. More than half of the CRKP strains contained the OqxA and OqxB efflux pump genes. The virulence genes were most commonly combined with urea-wabG-fimH-entB-ybtS-uge-ycf. Only one CRKP isolate was detected with the K54 podoconjugate serotype. This study elucidated the clinical epidemiological features and molecular typing of CRKP, and grasped the distribution of drug-resistant genotypes, podocyte serotypes, and virulence genes of CRKP, providing some guidance for the subsequent treatment of CRKP infection.

Virulence, antimicrobial resistance, and molecular characteristics of carbapenem-resistant Klebsiella pneumoniae in a hospital in Shijiazhuang City from China

Carbapenem-resistant Klebsiella pneumoniae (CRKP), as one of the most common drug-resistant bacteria threatening human health, is hyper-resistant to multiple antimicrobial drugs and carbapenems, which can be dealt with only limited clinical treatment options. This study described the epidemiological characteristics of CRKP in this tertiary care hospital from 2016 to 2020. Specimen sources included blood, sputum, alveolar lavage fluid, puncture fluid, secretions from a burn wound, and urine. Among the 87 carbapenem-resistant strains, ST11 was the predominant isolate, followed by ST15, ST273, ST340, and ST626. These STs were in broad agreement with the STs defined by pulsed-field gel electrophoresis clustering analysis in discriminating clusters of related strains. Most CRKP isolates contained the blaKPC-2 gene, some isolates carried the blaOXA-1, blaNDM-1, and blaNDM-5 genes, and the isolates carrying carbapenem resistance genes were more resistant to the antimicrobials of β-lactams, carbapenems, macrolides, and fluoroquinolone. The OmpK35 and OmpK37 genes were detected in all CRKP strains, and the Ompk36 gene was detected in some CRKP strains. All detected OmpK37 had 4 mutant sites, and OmpK36 had 11 mutant sites, while no mutant sites were found in OmpK35. More than half of the CRKP strains contained the OqxA and OqxB efflux pump genes. The virulence genes were most commonly combined with urea-wabG-fimH-entB-ybtS-uge-ycf. Only one CRKP isolate was detected with the K54 podoconjugate serotype. This study elucidated the clinical epidemiological features and molecular typing of CRKP, and grasped the distribution of drug-resistant genotypes, podocyte serotypes, and virulence genes of CRKP, providing some guidance for the subsequent treatment of CRKP infection.

Molecular Detection of gyrA Mutation in Clinical Strains of Klebsiella pneumoniae

BACKGROUND

Multi-drug resistant (MDR) Klebsiella pneumoniae strains cause the majority of community acquired and life-threatening infections. We aimed to detect the gyrA mutations in the clinical strains of nalidixic acid and ciprofloxacin resistant K. pneumoniae isolated from the patients with urinary tract infections.

METHODS

Bacterial strains were isolated from the patients with urinary tract infections admitted to a major hospital in Tehran, Iran (2017-2018). Bacterial identification was done according to standard microbiological tests. Antimicrobial susceptibility testing for quinolones and fluoroquinolone antibiotics was done using both disc diffusion and minimal inhibitory concentrations (MICs) methods. PCR-RFLP was used to detect the probable mutation in the gyrA gene in nalidixic acid and ciprofloxacin resistant strains. Finally sequencing was performed to detect point mutations in isolated K. pneumoniae strains.

RESULTS

One hundred K. pneumonia isolates were recovered from the urine samples of the clinical cases. Antibiotic resistance testing showed that among all K. pneumoniae isolates, 26% and 19% of the strains were resistant to nalidixic acid and ciprofloxacin respectively. MIC value was ≥4 μg/ml for ciprofloxacin resistant isolates. The results of RFLP on gyrA PCR amplicons using HinfI restriction enzyme showed point mutation in this gene in 46% of nalidixic acid and ciprofloxacin resistant K. pneumonia. The data obtained from the sequencing confirmed the RFLP results and indicated the presence of point mutations in codons 83 and 87 in the gyrA gene which leads to the substitution of different amino acids in gyrA protein.

CONCLUSION

Our findings indicated a relative increased rate of resistance against quinolones and fluoroquinolone antibiotics that raised a concern about extensive dissemination of clinical strains of nalidixic acid and ciprofloxacin resistant K. pneumonia. Point mutation of gyrA gene was responsible for the resistance in our strains however to gain more insight into the molecular characterization of quinolone-resistant isolates, other possible mechanisms of the resistance should also be investigated.

The effect of antibiotics and photodynamic therapy on extended-spectrum beta-lactamase (ESBL) positive of Escherichia coli and Klebsiella pneumoniae in urothelial cells

Background/aim

Urinary tract infections are commonly caused by the bacteria Escherichia coli and Klebsiella pneumoniae (UTI). The emergence of extended-spectrum -lactamase (ESBL)-producing bacteria strains has made UTI treatment more difficult.

Materials and methods

The aim of this study was to characterize E. coli and K. pneumoniae strains' cytotoxic effects, antibiotic sensitivity, interaction with urothelial cells, and reaction to photodynamic therapy.

Results

As demonstrated by the higher number of colonies formed, the ESBL + E. coli and K. Pneumonia showed a higher degree of binding with human urothelial cells. With the urothelial cells, K. Pneumonia had the highest binding ability. The cytotoxicity of non-ESBL generating E. coli and K. Pneumonia, on the other hand, was higher. With longer incubation, the discrepancy between the cytotoxic effects of non-ESBL producer and ESBL + E. coli decreased. K. Pneumonia was the opposite. The concentration of ESBL-negative E. coli was easily decreased by photodynamic therapy; however, after a two-hour incubation period, the number of E. coli ESBL + colonies increased from 124 percent to 294 percent.

Conclusion

With the duration of the incubation period, the number of non-ESBL-producing K. Pneumonia increased. Even with longer incubation times, the number of K. Pneumonia ESBL + colonies decreased, contrary to expectations. The findings show that the two bacterial species differed in terms of cytotoxicity, interaction with urothelial cells, and photodynamic therapy response.

Evaluation of (GTG) 5-PCR for Genotyping of Klebsiella pneumonia Strains Isolated from Patients with Urinary Tract Infections

BACKGROUND

Klebsiella pneumonia is one of the common causes of pneumonia and bacteremia in intensive care patients. The present study was aimed to determine the capability of (GTG) 5-PCR assay for molecular typing of K. pneumonia strains isolated from patients with urinary tract infections.

METHODS

In this descriptive-sectional study, K. pneumoniae strains were collected from hospitalized patients with urinary tract infection in Baqiyatallah Hospital, Tehran, Iran during 2017-2018. Isolates were identified by conventional microbiological tests. Bacterial DNA was extracted using boiling method and (GTG) 5-PCR assay was used for subtyping of the isolates. For clustering of isolates, dendrogram was generated according to the un-weighted pair group method with arithmetic (UPGMA).

RESULTS

Overall, 88 K. pneumoniae isolates were isolated and subjected to the molecular typing study. The (GTG) 5-PCR assay was able to differentiate the K. pneumoniae strains into 9 clusters including G1-G9. Genotype clusters G4 and G9 consist of highest (26) and lowest (1) number isolate, respectively.

CONCLUSION

The K. pneumonia strains isolated under the study belonged to various clones and the (GTG) 5-PCR assay as simple and rapid method can be a powerful tool for molecular typing of K. pneumoniae strains.