Background and Objectives: Extended spectrum beta lactamases (ESBLs) are responsible for resistance to third generation Cephalopsorins and Monobactums which form the mainstay of therapy in majority of clinical conditions. This study was performed to generate data on ESBLs and their CTX-M genotypes as prevalent in tertiary care centre at Kottayam, Kerala, India. The prevalence of ESBLs among Gram negative rods in specimens from lower respiratory tract in tertiary care centre at Kottayam was detected using standard methods and their CTX-M genotypes were detected using RT-PCR. The risk factors associated with the emergence of ESBLs and the spread of CTX-M enzymes were discussed.

Objectives: To determine the phenotype prevalence of ESBLs and genotype prevalence of CTX-M among Gram negative rods in specimens from respiratory tract at Government Medical College Hospital, Kottayam using standard methods and RT-PCR respectively.

Materials and Methods: 1216 specimens from lower respiratory tract namely sputum, broncholaveolar lavage and tracheal aspirate were collected during June 2017 to November 2017. Culture yielded 290 isolates of which 40 were multidrug resistant (MDR) strains. Phenotypic testing of ESBLs was done using Clinical Laboratory Standards Institute (CLSI) guidelines- disc diffusion testing. Genotypic testing of CTX-M Beta-lactamase was done using RT-PCR using primers from Gen Bank for Group I- CTX-M1, Group II- TOHO1, Group III- CTX-M825 and Group IV- CTX-M914.

Results: Phenotypic testing showed that out of 40 MDR  strains, all 40 tested positive, of which 31/220  (14%) were Klebsiella pneumoniae and 9/70  (12.8%) were E coli. Genotypic testing showed that of the 40 MDR strains, 15% of Klebsiella pneumoniae and 11% of E coli tested positive for Group III CTX-M while all tested negative for Group IV CTX-M. 10-14% of E coli and Klebsiella pneumoniae isolates tested positive for Groups I and II of CTX-M.

Conclusion: Even though CTX-M ESBLs which originated in Kluyvera species were first reported from Japan in 1980s, over the last decades, these genes have dispersed globally among Gram negative rods creating chaos in chemotherapy. This study of lower respiratory tract specimens from tertiary care centre reveals prevalence of ESBLs among multidrug resistant(MDR) strains at 72.7% in phenotype testing and 0-100% in the four gene clusters of CTX-M in genotype testing. Since the clinical microbiology laboratory is the first line of defence in the detection and control of ESBLs and failure to detect ESBLs implies treatment failure, this study stresses the importance of routine ESBL testing of atleast MDR strains and the need for clinicians to practise antibiotic stewardship earnestly.

Keywords: Extended spectrum beta lactamases (ESBLs), CTX-M gene, Multidrug resistant (MDR).

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Sheeba K Thomas

Assistant Professor, Department of Microbiology,

Government Medical College, Kottayam, Kerala, India