Phenotypic Characterization of Escherichia Coli Isolated From Urine and Stool from Short Term and Long Term Catheterized Patients

Background: Uropathogenic strains of Escherichia coli possess a number of phenotypic characters which allow them to colonize the catheter and cause infection of the same and the chances of colonization by these micro-organisms increase with the duration of catheterization. Objectives: This study was carried out to understand the differences between the phenotypic characters between the strains of E.coli isolated from the urine and gut of short term catheterized (STC) and long term catheterized (LTC) patients. Materials and Methods: Urine from the catheter and stool sample was processed by standard methods. The following special tests like α-hemolysis, haemagglutination, cell surface hydrophobicity, serum bactericidal assay, biofilm formation and congo red binding assay were performed to detect the phenotypic characters of the isolated E.coli. Antibiotic susceptibility testing was performed by Kirby Bauer method as per the Clinical Laboratory Standards Institute. Results: Majority (93.75%, 75% and 81.25%) of the E.coli isolates from urine of LTC patients were positive for MRHA, cell surface hydrophobicity and resistant to serum killing respectively, while majority (93.75%) of the urine isolates from short term catheterization. On congo red agar, the majority (80% and 60%) of isolates producing rdar type of colony and biofilm respectively,were isolated from urine of long term catheterized patients. ESBL production was noted in 68.75% of the urine isolates from long term catheterized patients. Conclusion: Serum resistance and biofilm formation are significant assays in terms of differentiating between the short term and long term catheterization and by elucidating these mechanisms better, it may become easier to combat and prevent such infections

Molecular detection of blaNDM and blaOXA-48 genes in Carbapenem-Resistant Klebsiella pneumoniae isolates from a tertiary care hospital

Background: The incidence of carbapenem-resistant Klebsiella pneumoniae (CRKP) infections is increasing globally. In India, around 65% of K. pneumoniae isolates are resistant to carbapenem antibiotics. The blaNDM is the predominant carbapenem-resistant gene in CRKP isolates. However, blaOXA-48 has also been reported to be increasing in recent days. Methods: K. pneumoniae strains isolated from the clinical specimens of patients attending a tertiary care hospital in Hyderabad from June 2021 to May 2022 were included in this study. Resistance to carbapenems and other antibiotics was screened using Kirby-Bauer’s disc diffusion method. Phenotypic tests such as the Carbapenemase Nordmann Poirel (CarbaNP) test, Modified Carbapenem Inactivation Method (mCIM), and EDTA Carbapenem Inactivation Method (eCIM) were used to detect the carbapenemase producers. The genes responsible for carbapenemase production were detected by the real-time polymerase chain reaction (RT-PCR) method. Results: Out of 1265 K. pneumoniae strains isolated, 241 (19 %) isolates showed resistance to any one of the carbapenem antibiotics tested. Phenotypic tests such as CarbaNP, mCIM, and eCIM revealed that 94.6 %, 97.1 %, and 95.4 % of CRKP isolates were carbapenemase producers, respectively. About 66.4 % of CRKP isolates harbored blaNDM, 17.4 % harbored blaOXA-48, and 16.2 % harbored both blaNDM and OXA-48 genes. None of the isolates tested positive for blaKPC, blaVIM, and blaIMP genes. Conclusion: In this study, blaNDM is the most prevalent carbapenemase gene in CRKP isolates. Furthermore, blaOXA-48 and the co-existence of both blaNDM and blaOXA-48 genes were also found. CRKP is emerging as a serious threat among drug-resistant bacterial pathogens which would complicate the treatment of bacterial infections with available antibiotics