Effective in Vitro Synergy of Piperacillin/Tazobactam Plus either Netilmicin or Aztreonam against Metallo-β-lactamase-producing Pseudomonas Aeruginosa

Wesam Hatem Amer,Marwa M E Abd-Elmonsef

doi:10.13189/ujmr.2016.040301

Abstract

This study was designed to compare the activity of piperacillin/tazobactam (TZP) in combination with either netilmicin (NET) or aztreonam (ATM) against metallo-β lactamases (MβL) Pseudomonas aeruginosa. Out of 46 nosocomial Ps. aeruginosa isolates, 38 (82.6%) isolates were carbapenem-resistant by disc diffusion susceptibility testing. These were then screened by imipenem + EDTA combined disc test for MβL production. Thirty (78.9%) MβL-producing isolates detected were further tested for antibiotic synergy against NET-TZP and ATM-TZP combinations by Etest synergy and Etest/agar dilution tests. Neither combination showed antagonism. The synergistic effect of NET-TZP combination was detected in (27 (90%) and 28 (93.3%), respectively) and ATM-TZP combination in (24 (80%) and 25 (83.3%), respectively) of the tested isolates by Etest synergy and Etest/agar dilution tests, respectively. Thus, we have determined the synergistic effect of these two combinations for treating MβL-producing Ps. aeruginosa. Significance and Impact of the Study: The present study has shown valuable information on the combination treatment of Ps. aeruginosa and recommends their use for treatment of resistant Ps. aeruginosa.

Highlights

Pseudomonas aeruginosa is an important opportunistic pathogen that plays a serious role in many infections especially in immuno-compromised patients [1]
Metallo-β-lactamase (MβL) production by Ps. aeruginosa is a major challenge because it confers multidrug resistance (MDR) to β-lactam agents, as well as co-resistance to fluoroquinolones and aminoglycosides [3]
Aminoglycosides are among the oldest antibiotics to treat serious infections, they have severe side effects such as nephrotoxicity, ototoxicity and, rarely, neuromuscular blockade and hypersensitivity reactions

Summary

Introduction

Pseudomonas aeruginosa is an important opportunistic pathogen that plays a serious role in many infections especially in immuno-compromised patients [1]. Infections by this organism are characterized as severe and resistant to treatment with drugs [2]. Continued emergence and rapid spread of MDR Ps. aeruginosa strains have resulted in increased morbidity, mortality and cost [1,4]. This increased the need for alternative strategies such as combination of anti-pseudomonal antibiotics as an alternative strategy in the management of these cases. Aminoglycosides are among the oldest antibiotics to treat serious infections, they have severe side effects such as nephrotoxicity, ototoxicity (vestibular and auditory) and, rarely, neuromuscular blockade and hypersensitivity reactions

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