MOLECULAR CHARACTERIZATION OF PSEUDOMONAS AERUGINOSA ISOLATES RECOVERED FROM HUMAN PATIENTS IN HIMACHAL PRADESH (INDIA) FOR SELECTIVE GENES: EXTENDED SPECTRUM β-LACTAMASE (ESBL), AMPICILLIN CLASS C (AMPC) AND METALLO β-LACTAMASE (MBL) GENES

The present study highlights the occurrence of β-lactamase (bla) genes belonging to different classes: extended spectrum β-lactamase genes (bla_TEM, bla_SHV, bla_CTX-M and bla_PER), metallo β-lactamase genes (bla_NDM and bla_GIM and Ampicillin class C genes (bla_PDC and bla_CMY) in P. aeruginosa isolates by PCR amplification. The isolates were recovered from human patients of Indira Gandhi Medical College & Hospital at Shimla in the state of Himachal Pradesh (India). We have previously detected different β-lactamases in 180 confirmed isolates of P. aeruginosa by phenotypic methods in our laboratory. Such isolates have been characterized in the present study for their genotypes in respect of the specified genes. Of the 56 phenotypically ESBL positive isolates, the ESBL genes (bla_TEM, bla_SHV and bla_CTX-M) could be amplified in 14 (25%), 1 (1.78%) and 6 (10.71%) isolates respectively. Of these, three isolates had both bla_TEM & bla_CTX-M genes. Of the 29 phenotypically MBL positive isolates, the bla_NDM could be amplified in 11 (37.93%) isolates only. However, no amplification was achieved in case of bla_GIM gene. AmpC-type gene derived from P. aeruginosa (bla_PDC) was successfully amplified in 11 out of 52 phenotypically AmpC positive isolates i.e. (21.15%). However, the amplification was not achieved in case of bla_CMY gene. The data reflect the occurrence of different classes of β-lactamase genes and their co-occurrence in some isolates. Based on nucleotide sequence homologies of amplicons of different genes, the NDM variants were identified as -1 and -7, TEM-1, SHV-12, CTX-M-15 in this geographic region, while the amplicon of bla_PDC showed homology to different bla_PDC variants.