title: In vitro activity of tigecycline against clinical isolates of carbapenem resistant Acinetobacter baumannii complex in Pretoria, South Africa.
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.
  
  
  OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: 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. nahidhussaan@gmail.com
authors.forename: Nahid H
authors.initials: NH
authors.lastname: Ahmed
authors.forename: Kamaldeen
authors.initials: K
authors.lastname: Baba
authors.forename: Cornelis
authors.initials: C
authors.lastname: Clay
authors.forename: Ruth
authors.initials: R
authors.lastname: Lekalakala
authors.forename: Anwar A
authors.initials: AA
authors.lastname: Hoosen
mesh_terms: D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000302:isolation & purification*; D000328:Adult; D015780:Carbapenems / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D008911:Minocycline / Q000031:analogs & derivatives* / Q000494:pharmacology; D013019:South Africa; D000078304:Tigecycline
chemical_list: D015780:Carbapenems; D000078304:Tigecycline; D008911:Minocycline