Molecular characterization of genes encoding AmpC beta-lactamases in clinical isolates of Pseudomonas and Acinetobacter species.

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 β-lactam 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 AmpC-specific 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.

Comparative study on occurrence of class A and class C β -lactamase genes and their co-occurrence in Indian Enterobacteriaceae during years 2009 and 2010

OBJECTIVE@#To determine the occurrence of class A and class C β-lactamase genes and their co-occurrence in Indian Enterobacteriaceae.@*METHODS@#52 third generation cephalosporin resistant isolates were phenotypically detected by combination disk method and screened by PCR to identify class A and class C type β-lactamase genes.@*RESULTS@#Of the 52 isolates, 94.2% (49) were found harboring any of the bla(ESBL(s)). bla(CTX-M), bla(SHV) and bla(TEM) were present in 82.6% (43/52), 59.6% (31/52), and 42.3% (22/52) isolates, respectively. Of the 49 ESBL positive isolates 57.1% (28/49) showed co-occurrence of bla(ampC) with bla(ESBL(s)). On the contrary, the collection from 2009 showed their co-occurrence in 81.4% isolates.@*CONCLUSIONS@#The comparative study shows a downward trend for co-existence of bla(ESBL(s)) with bla(ampC) from 2009 to 2010. Further large scale studies are needed to address the co-occurrence of class A and class C β-lactamases in India and the resistance trend occurring over a period of time.

bla(CTX-M), bla(TEM), and bla(SHV) in Enterobacteriaceae from North-Indian tertiary hospital: high occurrence of combination genes

OBJECTIVE@#To delineate the frequency of occurrence of bla(CTX-M), bla(TEM), and bla(SHV) in Enterobacteriaceae from North-Indian tertiary hospital.@*METHODS@#A random collection of a subset of 45 Escherichia coli (E. coli) and 28 Klebsiella pneumoniae (K. pneumoniae) that was resistant to a third generation cephalosporin and obtained during 2007-2008 was selected for detailed screening for bla(CTX-M), bla(TEM), and bla(SHV) by monoplex PCRs. The isolates demonstrating the presence of bla(CTX-M) alleles were characterized for the specific CTX-M-genogroup by using a multiplex PCR.@*RESULTS@#Resistance to cefoperazone, ceftazidime, ceftriaxone, cefotaxime, cefoxitin and piperacillin was 100% each in K. pneumoniae isolates, whereas these resistance-rates for E. coli isolates were 93.1%, 83.8%, 91.9%, 93.6%, 97.3% and 97.1%, respectively. Concomitant resistance to aminoglycosides, quinolones and aztreonam was also noticed. Presence of any of the bla genes (bla(CTX-M), bla(TEM), and bla(SHV)) was noticed in a total of 28 (38.4%) isolates of the 73 isolates studied. Many isolates demonstrated occurrence of these genes in various combinations. bla(CTX-M), bla(TEM), and bla(SHV) were noticed in 28.8%, 10.9% and 13.7% isolates, respectively. Multiplex PCR in bla(CTX-M) harboring isolates demonstrated the presence of CTX-M-Genogroup-1 and sequencing for the specific CTX-M-type revealed presence of CTX-M-15 type. RAPD typing showed wide diversity in isolates.@*CONCLUSIONS@#This is amongst the premier report describing the simultaneous occurrence of bla(TEM), bla(SHV), and bla(ampC) in Indian Enterobacteriaceae and that wider dissemination of these genes, as demonstrated by diversity of isolates, raises concern and emphasizes a need for extensive search for the presence of these gene pools in Indian subcontinent.