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Open Access Research article

In vitro activity of tigecycline against clinical isolates of carbapenem resistant Acinetobacter baumannii complex in Pretoria, South Africa

Nahid H Ahmed1*, Kamaldeen Baba12, Cornelis Clay1, Ruth Lekalakala12 and Anwar A Hoosen12

Author Affiliations

1 Department of Medical Microbiology, Faculty of Health Sciences, University of Pretoria, Prinshof Campus, Pathology Building, 5 Bophelo Road, Private Bag X323, Code: 0007, Riviera, Pretoria, 0084, South Africa

2 Tshwane Academic Division of the National Health Laboratory Service, Pretoria, South Africa

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BMC Research Notes 2012, 5:215  doi:10.1186/1756-0500-5-215

Published: 3 May 2012

Abstract

Background

The presence of multi-drug resistant Acinetobacter baumannii raises a big therapeutic challenge in our hospital. Tigecycline, a new glycylcycline with expanded broad spectrum of activity against multi-drug resistant organisms was recently licensed in South Africa.

Aim

The aim of this study was to evaluate the in vitro activity of tigecycline against carbapenem resistant A. baumannii complex.

Methods

Consecutive clinical isolates of carbapenem resistant A. baumannii complex were collected between February and July 2010. Species identification and susceptibility testing was performed by Vitek-2 colorimetric compact system with Advanced Expert System (AES). Strains were tested for carbapenemase production by the modified Hodge test, according to the Clinical and Laboratory Standards Institute (CLSI) guidelines.

Results

A total of 232 carbapenem resistant clinical isolates of A. baumannii complex were collected over the six months study period; 217 (93.5%) of these were modified Hodge test positive. All isolates were susceptible to colistin and 174 (78%) susceptible to amikacin whilst 20 (9%) were susceptible to ciprofloxacin. For tigecycline 169 (75.8%) were fully susceptible, 37 (16.6%) intermediately resistant and only 17 (7.6%) were fully resistant. None of the carbapenem resistant isolates were susceptible to ampicillin, amoxicillin/clavullanic acid, piperacillin/tazobactam, cefuroxime, cefuroxime axetil, cefoxitin, cefepime or nitrofurantoin.

Conclusion

All carbapenem resistant isolates were found to be fully susceptible to colistin; amikacin and tigecycline susceptibility was 78% and 76% respectively. Treatment options for infections due to carbapenem and multi-drug resistant A. baumannii organisms are limited and hence tigecycline and amikacin may be considered. The properties of tigecycline i.e. stability, safety, low toxicity, non cross-resistance with other antibiotics and its efficacy against multi-drug resistant A. baumannii isolates make it a good choice. However, ongoing monitoring of A. baumannii susceptibility to tigecycline is needed.

Keywords:
Tigecycline; Carbapenems; Acinetobacter baumannii complex