The use of successive generations of beta-lactams has selected successive generations of beta-lactamases including CTX-M ESBLs, AmpC beta-lactamases, and KPC carbapenamases in Enterobacteriaceae. Moreover, this cephalosporin resistance, along with rising resistance to fluoroquinolones, is now driving the use of carbapenems and unfortunately the carbapenem resistance has emerged markedly, especially in Acinetobacter spp. due to OXA- and metallo-carbapenemases. The industry responded to the challenge of rising resistance and recently developed some novel beta-lactams such as ceftobiprole, ceftaroline etc. and many beta-lactam compounds, including beta-lactamase-inhibitors, such as BMS-247243, S-3578, RWJ-54428, CS-023, SMP-601, NXL 104, BAL 30376, LK 157, and so on are under trials. This review provides the comprehensive accounts of the developments in penicillins, cephalosporins, carbapenems, and beta-lactamase-inhibitors, and the insight about medicinal chemistry, mechanism(s) of action and resistance, potential strategies to overcome resistance due to beta-lactamases, and also the recent advancements in the development of newer beta-lactam compounds; some of which are still under trials and yet to be classified. This review will fill the gap since previously published reviews and will serve as a comprehensive update on the current topic.

To delineate the frequency of occurrence of bla(CTX-M), bla(TEM), and bla(SHV) in Enterobacteriaceae from North-Indian tertiary hospital. 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. 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. 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.

Cefoxitin-resistant Escherichia coli ( n = 109) and Klebsiella pneumoniae ( n = 16) isolates collected from patients in India in 2009 to 2010 were screened for bla _ampC families and mobilizing elements ( ISE cp1, IS 26, IS CR1, and sul -1-type class 1 integrons) and their association with bla _ampC and for the occurrence of class A beta-lactamases (BLs) (CTX-M, TEM, and SHV). The concurrent occurrences of two distinct AmpC families ( bla _CIT and bla _EBC ) and of class A with class C beta-lactamase were observed. All but one of the isolates harboring CTX-M extended-spectrum BLs (ESBLs) were carrying bla _CTX-M genogroup 1; the remaining isolate carried bla _CTX-M genogroup 9. The mobilizing elements occurred in different combinations in the study isolates.

Background: Cefotaximases (CTX-M), temoniera (TEM), and sulfhydryl variable (SHV) constitute a rapidly growing cluster of enzymes that have disseminated geographically. They are spreading to species other than Enterobacteriaceae and might be responsible for the presence of bla_CTX-M,bla_TEM, and bla_SHVgenes in Pseudomonas and Acinetobacter spp. The present study was designed to characterize CTX-M, TEM, and SHV phenotypically and genotypically in Pseudomonas and Acinetobacter spp. Materials and Methods: A total of 90 isolates (73 Pseudomonas and 17 Acinetobacter spp.), resistant to any of the third-generation cephalosporins, were randomly selected from clinical samples. Results: Of 90 isolates, 64 (71.11%) were tested positive for extended-spectrum β-lactamase (ESBL) production. Among phenotypically tested ESBL producers, forty isolates were randomly selected for molecular characterization. The prevalence of CTX-M, TEM, and SHV was found to be 57.5%, 15%, and 75%, respectively. Multiplex polymerase chain reaction assay categorized bla_CTX-Mgenes into Groups 1 and 26 where Group 1 was present in only 5 isolates and Group 25 was present in rest of the 18 isolates. Conclusion: 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.