Abstract
BACKGROUND: Extended-spectrum beta-lactamase (ESBL)-producing organisms inactivate extended
beta-lactam antibiotics and monobactams and also exhibit coresistance to many other
classes of antibiotics. The present study was carried out to assess the prevalence
of the ESBLs and to determine the most prevalent genotype in our hospital.
MATERIALS AND METHODS: All clinically significant Gram-negative isolates were identified, and their antimicrobial
susceptibility testing was done by Kirby–Bauers' disc diffusion method. ESBL detection
was confirmed by minimal inhibitory concentration method using agar dilution technique
for those who screened positive by ceftazidime (30 μg) disc. Further, the established
ESBL-positive isolates were subjected to genotyping for bla TEM, bla CTX-M, and bla
SHV genes by using conventional polymerase chain reaction.
RESULTS: Escherichia coli was the most common (28.84%) Gram-negative bacillus followed by Klebsiella pneumoniae (18.07%), while Pseudomonas spp. (9.61%) was the most commonly identified nonfermenter. ESBL production was detected
in 160 (30.8%) isolates. Klebsiella oxytoca (46.7%) followed by E. coli (44%) were the common ESBL producers. Most predominant ESBL gene was bla TEM, found
in 122 (76.25%) isolates. Combinations of two genes were seen in 109 (68.1%) isolates,
the most common (43.12%) combination being blaTEM and blaCTX-M. In this study, 16 (10%) strains had all the three types of genes. Most of the isolated
Gram-negative bacilli (GNB) were sensitive to amikacin, imipenem, and colistin.
CONCLUSION: In our study, the 30.8% of GNB were ESBL producers. This is the only study that
shows that TEM is the most prevalent ESBL genotypes in our area. Of concern is a good
number of isolates showing all three patterns of genes (TEM, SHV, and CTX-M). Amikacin,
imipenem, and colistin were the most useful antibiotics in our setup.
Key words
Bla TEM - extended-spectrum beta-lactamase - genotyping
