Predominance of CTX-M Type Extended Spectrum β-lactamase (ESBL) Producers Among Clinical Isolates of Enterobacteriaceae in a Tertiary Care Hospital, Kathmandu, Nepal

ESBL problem is increasing worldwide and only limited studies on genes of ESBL are performed in Nepal.

We aimed to focus on the molecular detection of plasmid-mediated bla_TEM, bla_SHV and bla_CTX-M genes among the ESBL producing Enterobacteriaceae from different clinical samples.

A total of 550 clinical samples were processed and organisms of Enterobacteriaceae were identified using standard microbiological process. ESBL producers were screened and confirmed using the modified Kirby Bauer disc diffusion method by CLSI guidelines. Plasmids extracted from the confirmed ESBL positives were the template for PCR. bla_SHV, bla_TEM and bla_CTX-M genes were amplified using specific primers of respective genes by uniplex PCR. The presence of these genes was confirmed by gel electrophoresis.

Among 550 different clinical samples 343 (62.36%) were culture positive. Of which, 157 (45.57%) belonged to Enterobacteriaceae. Escherichia coli (45.9%) was predominant. Of these 33.2% (52/157) isolates were ESBL positive. ESBL- E. coli (52.8%) were prevalent. All ESBL positive organisms were sensitive to imipenem. Of confirmed ESBL positives, 34.6% harbored bla_TEM gene, 30.8% harbored bla_SHV gene and bla_CTX-M genes were present in all ESBL producers. Twenty-eightout of 52 (53.9%) isolates harbored multiple bla genes, the most common combination being bla_CTX-M + bla_TEM (21.2%).

We report 100% plasmid mediated CTX-M genotype among ESBL producers which might indicate rapid dissemination of bla_CTX-Mgenes from the community to the patients. Besides, there is a need for regular monitoring of antibiotic resistance in the country and de-escalate the use of antibiotics so as to preserve the antibiotics for future generation.