Determination of frequency of Extended Spectrum Beta Lactamase (ESBL) of Klebsiella isolated from raw and school milk samples using phenotypic and genotypic Methods

Resistance to a wide range of beta-lactam family antibiotics is due to the emergence of new beta-lactamases among bacterial strains. The aim of the present study was to determine the prevalence of ESBLs in Klebsiella speices isolated from raw and pasteurized school
milk using phenotypic and genotypic methods. 

In a descriptive cross-sectional study, 200 samples of raw and pasteurized school milk were analyzed for the presence of Klebsiella spp. Samples were grown on Hektoen enteric agar medium. Suspected colonies of Klebsiella spp. were confirmed running differential tests. For the initial screening of ESBL producing organisms, the Disk Diffusion Agar method (DDA) was used. Final confirmation was done using PCR.

Out of 200 samples tested, 44 isolates were identified as Klebsiella, 32 isolates (72.7%) from raw and 12 (27.3%) from pasteurized school milk. In general, 14 (31.8%) isolates that were resistant to at least ceftazidime or cefotaxime antibiotics were selected for confirmatory testing.In Multiplex PCR assay, 6 (3%) isolates were screened for the confirmatory test (5 raw and 1 pasteurized school milk). Out of 6 isolates, 4 (2%) and 1 (0.5%) isolates contained TEM and DHA genes, and 2 (1%) and 1 (0.5%) isolates contained SHV and CITM genes, respectively.

It is difficult to identify the enzymes producing strains through the phenotypic tests; therefore, the inclusion of molecular probes using universal primers along with phenotypic tests can be used for the detection of these types of resistance, which play a major role in infection control.