Abstract
BackgroundLimited knowledge of the local molecular epidemiology and the paucity of new effective antibiotics has resulted in an immense challenge in the control and treatment of extensively drug-resistant (XDR) Acinetobacter baumannii infections in Thailand. Antimicrobial combination regimens may be the only feasible treatment option in such cases. We sought to characterize the local molecular epidemiology and assess the bactericidal activity of various antibiotics individually and in combination against XDR A. baumannii in a Thai hospital.MethodsAll XDR A. baumannii isolates from Thammasat University Hospital were collected between October 2010 and May 2011. Susceptibility testing was conducted according to reference broth dilution methods. Pulse-field gel electrophoresis was used to genotype the isolates. Carbapenemase genes were detected using polymerase chain reaction. In vitro testing of clinically-relevant concentrations of imipenem, meropenem, doripenem, rifampicin and tigecycline alone and in combination with polymyxin B was conducted using multiple combination bactericidal testing.ResultsForty-nine polymyxin B-susceptible XDR A. baumannii isolates were identified. blaOXA-23 and blaOXA-51 genes were detected in all isolates. Eight clonally related clusters were identified, resulting in the initiation of several infection control measures. Imipenem, meropenem, doripenem, rifampicin, and tigecycline in combination with PB respectively, exhibited bactericidal killing in 100%, 100%, 98.0%, 100% and 87.8% isolates respectively at 24 hours.ConclusionMolecular epidemiologic analysis can aid the early detection of infection outbreak within the institution, resulting in the rapid containment of the outbreak. Imipenem/meropenem/rifampicin in combination with polymyxin B demonstrated consistent bactericidal effect against 49 blaOXA-23-harbouring XDR A. baumannii clinical isolates, suggesting a role of combination therapy in the treatment of these infections.
Highlights
Limited knowledge of the local molecular epidemiology and the paucity of new effective antibiotics has resulted in an immense challenge in the control and treatment of extensively drug-resistant (XDR) Acinetobacter baumannii infections in Thailand
As limited combination studies were performed on local Thai isolates [11,12,13,14], the objective of this study was to assess the bactericidal activity of various antibiotics individually and in combination against Extensively drug-resistant (XDR) Acinetobacter baumannii (AB), in addition to the characterization of the molecular epidemiology of XDR AB in Thailand
All isolates were resistant to meropenem, imipenem, ampicillin/sulbactam, ciprofloxacin, gentamicin, aztreonam, piperacillin/ tazobactam, ceftazidime, cefepime and amikacin based on susceptibility testing results from Thailand
Summary
Limited knowledge of the local molecular epidemiology and the paucity of new effective antibiotics has resulted in an immense challenge in the control and treatment of extensively drug-resistant (XDR) Acinetobacter baumannii infections in Thailand. In Thailand, AB infections represent a key The management of these extensively drug-resistant (XDR) AB infections is challenging due to the limited molecular epidemiologic data available. The drying antibiotic pipeline has put us at risk of having no effective treatment options against infections caused by this bacterium in the near future [3]. This dearth in new antibiotics has led to the renewed clinical use of polymyxin antibiotics, the last resort treatment. There are few concerns related to polymyxin monotherapy, the primary being the emergence of heteroresistance and adaptive resistance, potentially leading to clinical failure [5,6,7]
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