ORIGINAL ARTICLE P J M H S VOL. 7 NO.4 OCT – DEC 2013 1143 In Vitro Activity of Piperacillin/Tazobactam against Pseudomonas Species in Paediatric Population TALHA MANNAN, AIZZA ZAFAR, NAIMA MEHDI ABSTRACT Aim: To determine the susceptibility of piperacillin/ tazobactam against Pseudomonas species Methods: This cross sectional observational study was conducted during April 2011 to March 2012 at Microbiology department of The Children’s Hospital and Institute of Child Health, Lahore. A total number of 10761 samples were collected and processed for microbiological investigations. The organisms were identified by routine laboratory tests including biochemical tests. Results: Out of 10,761 samples 2,375(22%) were positive for bacterial growth, among them 200(9.2%) were Pseudomonasspp. and 2,175(90.8%) were other than Pseudomonasspp. The highest proportion of Pseudomonas spp. was isolated from urine samples 69(34.5%) followed by blood 60(30%), swab 50(25%) and 21(10.5%) from the samples of sputum, secretion and tips. From a total 200 positive cultures of Pseudomonas spp. urology ward accounted for the highest proportion 44(18%), followed bymedical ward 36(18%). The proportions of other wards were as: OPD 30(15%), neonatology 29(14.5%), ICU 16(8%), hematologyoncology ward 14(7%), surgical ward 13(6.5%), developmental ward 7(3.5%), M/E 6(3%) and orthopedics ward 5(2.5%). Pseudomonas spp. was found highly sensitive to piperacillin/tazobactam (87.5%). Sensitivity to other antimicrobial discs was meropenem (86.5%), sulbactam/cefoperazone (82.5%), amikacin (74.5%), ciprofloxacin (64.5%), cefotaxime (17.5%), ceftriaxone (20.0%), ceftazidime (60.5%), pipemedic acid (21.75%), nitrofurantoin (18.8%) and norfloxacin (46.4%). Sensitivity of norfloxacin, nitrofurantoin. Conclusion: Piperacillin/tazobactam is the most active combination against Pseudomonas spp.and remains a very active beta-lactam when tested in vitro against clinical isolates of Pseudomonas spp. Keywords: Piperacillin/tazobactam, Pseudomonas spp. INTRODUCTION Over the past century, Pseudomonas species have become an increasingly important pathogen, leading to the characteristically high level of lethality and persistent infections 1 . Pseudomonas aeruginosa, called the "epitome" of opportunistic pathogen, almost never infects uncompromised tissue. However it can infect practically any type of tissue if that tissue has some type of compromised defenses 2 . Patients who are hospitalized for extended periods are frequently colonized by this organism and are at high risk of developing infections 3 . It is a notoriously difficult to control this organism with antibiotics or disinfectants 4 . There are three basic mechanisms by which organisms resist the action of antimicrobial agents: restricted uptake and efflux, drug inactivation and changes in target. The innate resistance of Pseudomonas aeruginosa to all classes of antibiotics has generally been attributed to the low permeability of its cell wall 5 . Piperacillin /tazobactam is a -lactamase inhibitor combination with a broad spectrum of antibacterial ---------------------------------------------------------------------- Microbiology Department, The Children's Hospital and Institute of Child Health, Lahore Correspondence: Dr. Talha Mannan activity encompassing most Gram positive and Gram negative aerobic and anaerobic bacteria, including many pathogens producing -lactamases 6 . For β- lactamase inhibitor combinations, susceptibility rates are higher for piperacillin/tazobactam when compared in all regions with piperacillin alone. Piperacillin/tazobactam remained a very active β- lactam drug when tested in vitro against clinical isolates of Pseudomonas aeruginosa 7 . Combining tazobactam, a beta-lactamase inhibitor, with the ureidopenicillin- piperacillin, successfully restores the activity of piperacillin against beta-lactamase producing bacteria. Anextremely high level of antimicrobial resistance was seen in hospital acquired infections, especially among non-enteric Gram-negative bacilli. Due to this high level of resistance, piperacillin/tazobactam represents an important contribution to the treatment of nosocomial infections 8 . METHEDOLOGY This cross sectional study was performed at the Microbiology Department of the Children’s Hospital and The Institute of Child Health Lahore, Pakistan, from July 2012 to November 2012. A total number of