title: Comparative in vitro activity of beta-lactam/beta-lactamase inhibitor combinations against gram negative bacteria.
abstract: OBJECTIVE
  Currently, the use of beta-lactamase inhibitors in combination with beta-lactam antibiotics represents an effective measure to combat a specific resistance mechanism of beta-lactamase producing organisms. Knowledge about the susceptibility profile of bacteria to different combination agents available is essential to guide appropriate treatment of severe infections in hospitalized patients. The present study compares the in vitro activity of three commercially available beta-lactam/beta-lactamase inhibitor combinations (piperacillin/tazobactam, cefoperazone/sulbactam, ticarcillin/clavulanic acid) against beta-lactamase producing gram negative bacteria in a tertiary care hospital in north India.
  
  
  METHODS
  A total of 9004 consecutively isolated extended spectrum beta-lactamase (ESBL) producing gram negative bacteria isolated from various clinical samples from patients admitted to the All India Institute of Medical Sciences, New Delhi, from September 2003 to August 2004 were included in the study. These isolates were screened for ESBL production by the inhibitor based test recommended by the National Committee for Clinical Laboratory Standards (NCCLS). Antibiotic susceptibility testing was carried out by disc diffusion method as per NCCLS guidelines.
  
  
  RESULTS
  Of the 9004 isolates tested, 3232 (35.89%) were sensitive and 568 (6.31%) were resistant to all three combination agents, and rest 5204 (57.80%) were resistant to at least one of the combinations. Susceptibility to piperacillin/tazobactam, cefoperazone/sulbactam, and ticarcillin/clavulanic acid was 81.37, 76.06 and 45.48 per cent respectively. Piperacillin/tazobactam exhibited significantly (P<0.05) greater antimicrobial activity against Pseudomonas spp., Escherichia coli and Klebsiella spp. compared to cefoperazone/sulbactam.
  
  
  CONCLUSIONS
  Overall piperacillin/tazobactam was observed to be the best combination agent followed by cefoperazone/sulbactam in our setting. This difference in activities of these combination agents needs to be evaluated further by ascertaining their efficacy in clinical studies.
authors.affiliation: Department of Microbiology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India.
authors.forename: Srujana
authors.initials: S
authors.lastname: Mohanty
authors.forename: Ritu
authors.initials: R
authors.lastname: Singhal
authors.forename: Seema
authors.initials: S
authors.lastname: Sood
authors.forename: Benu
authors.initials: B
authors.lastname: Dhawan
authors.forename: Bimal K
authors.initials: BK
authors.lastname: Das
authors.forename: Arti
authors.initials: A
authors.lastname: Kapil
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002438:Cefoperazone / Q000494:pharmacology; D002969:Clavulanic Acids / Q000494:pharmacology; D003428:Cross Infection / Q000517:prevention & control*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D006801:Humans; D010397:Penicillanic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D010878:Piperacillin / Q000494:pharmacology; D000077725:Piperacillin, Tazobactam Drug Combination; D013407:Sulbactam / Q000494:pharmacology; D013982:Ticarcillin / Q000494:pharmacology; D018440:beta-Lactam Resistance / Q000187:drug effects*; D065093:beta-Lactamase Inhibitors
chemical_list: D000900:Anti-Bacterial Agents; D002969:Clavulanic Acids; D065093:beta-Lactamase Inhibitors; D000077725:Piperacillin, Tazobactam Drug Combination; D002438:Cefoperazone; C043215:ticarcillin-clavulanic acid; D010397:Penicillanic Acid; D013982:Ticarcillin; D013407:Sulbactam; D010878:Piperacillin