What can we learn from the dissemination of carbapenem-resistant Acinetobacter baumannii in patients with burn injury?

In this issue of the Journal of the Chinese Medical Association, Shoja et al characterize the antimicrobial susceptibility pattern, resistance mechanisms, and typing of carbapenem-resistant Acinetobacter baumannii (CRAB) isolates obtained from burn patients from a single center in Iran. They found that the rate of CRAB was high (92.5%) among burn patients. The most effective drugs with in vitro activity against A. baumannii isolates in this study were colistin, polymyxin B, and ampicillinesulbactam. Carbapenem resistance involved blaOXA-23-like and blaOXA-24-like genes. The clonal spreading of A. baumannii strains were identified among these burn patients. This study suggests the necessity of effective control measures against these multidrug-resistant pathogens. A. baumannii is an important pathogen causing various nosocomial infections, and has become one of the most commonly isolated pathogens in burn patients. Outbreaks and rapid dissemination of CRAB strains despite prevention and control measures have been reported worldwide, which most commonly occur in intensive care units. The spreading of multidrug-resistant A. baumannii (MDRAB), especially CRAB, has become a threat to public health. The most important mechanism of carbapenem resistance in A. baumannii is the production of carbapenem-hydrolyzing b-lactamases, especially Ambler classes D-carbapenemase (OXA blactamases). Most of the groups of OXA-type b-lactamases have been identified on plasmids, and have a high capacity to spread. The insertion sequence ISAba1 has been found upstream of blaOXA-23-like and blaOXA-51-like genes in A. baumannii and leads to overexpression of blaOXA genes. 8 Other less-studied mechanisms in carbapenem resistance in A. baumannii are reduced outer membrane permeability, penicillinbinding protein alterations, and overexpression of the efflux pump. BlaOXA-23-like and blaOXA-24-like genes were found among the A. baumannii isolates. Although several mechanisms would work in concert to produce the resistance phenotype, a more detailed investigation of mechanisms for carbapenem resistance is recommended for future study. Molecular typing of the relevant A. baumannii isolates was a common approach for hospital outbreak investigations. The current study showed that Clones B and C were predominantly