This is among the premier systemic reports from India documenting phenotypic and molecular characterization of CTX-M, TEM, and SHV β-lactamases in Pseudomonas and Acinetobacter spp. With judicious use of antibiotics and strict infection control procedures, it may be possible to limit the effects of these newer β-lactamases.

While the emergence of antibacterial drug resistance is a great emerging health issue that threatens the clinical usefulness of these drugs, it is important to study the spread of antibiotic resistance genes in order to understand the relationship between resistance gene pool and its mobilization through transposons and integrons. 125 cefoxitin-resistant E. coli (109) and K. pneumoniae (16) isolates were looked for the presence of integrons in order to illustrate the location of antibiotic resistance genes (especially bla ampC ). The genotyping was done by RAPD so as to find out genetic relatedness among isolates. 55.20% (69/125) isolates were found positive for integrons. 41 isolates showed single amplification band for CS region, 20 showed two bands, 4 showed three bands and four isolates showed multiple banding patterns. Sul-1 was reported to be present in 3'CS, but we also observe 14/69 isolates that showed amplification for 5'CS-3'CS region but did not show presence of Sul-1 (when detected by PCR). Out of 109 E. coli isolates, 91 could be typed by RAPD, while 18 were found untypable. Among 91 E. coli isolates, 33 were grouped in 15 clusters while the remaining 58 isolates showed unique banding patterns indicating genetic un-relatedness. Among 16 K. pneumoniae isolates, 14 were typed by RAPD and 2 isolates were found untypable. The higher rate of resistance to several classes of β-lactam antibiotics in integron-positive isolates is probably attributable to the association of β-lactamase genes with integron-carrying plasmids and hence suggests that antibiotic drug resistance is transmitting through these mobilizing agents. As evident from RAPD-typing, most patients in our hospital were infected with different clades of organisms, thereby demonstrating clonal diversity among isolates suggesting horizontal transmission of bla genes.

No abstract

Emergence of AmpC beta-lactamases in isolates of Pseudomonas and Acinetobacter species, is a threatening condition as they mediate resistance to a wide variety of β-lactam drugs, including α-methoxy-β-lactams, such as cefoxitin, narrow-, expanded-and broad-spectrum cephalosporins, aztreonam and are poorly inhibited by βlactam inhibitor combinations. The present study was conducted to determine the occurrence of blaampC genes in these pathogenic non-fermenters for their rapid and accurate detection. Monoplex PCR was done to detect blaampC genes in 40 non-duplicate clinical Pseudomonas and Acinetobacter isolates, that were found resistant to any of the third-generation cephalosporin and cefoxitin. Multiplex PCR assay was carried out to identify family-specific AmpC beta-lactamase genes within Pseudomonas and Acinetobacter spp. PCR detected blaampC in 43.24% of Pseudomonas and 33.33% of Acinetobacter isolates. Overall 42.50% of the total isolates were found to harbour blaampC genes by PCR. By multiplex PCR, total eight (20%) isolates yielded a positive amplicon with AmpCspecific primers. High prevalence of blaampC genes in cefoxitin-resistant isolates of Pseudomonas and Acinetobacter isolates emphasizes that molecular detection methods should be carried out to know the exact prevalence of beta-lactamases.