Study of carbapenem resistance in acinetobacter baumannii isolates from Kuwait
Al-Hasan, Ahmad Redha
Acinetobacter baumannii is a Gram-negative, non-fermenting bacillus that has developed into an important nosocomial pathogen, affecting millions of patients worldwide. The widespread ease of transmission, and ability to become multidrug resistant are some of the characteristics that, at the present time, have developed this bacterium into one of the most significant nosocomial pathogens today. The special ability it exhibits in developing resistance to a wide variety of known antimicrobial agents also helped make this a pathogen of profound importance in modern day medical microbiology. Carbapenems are used as a last resort for treating patients infected with resistant or multi-drug resistant (MDR) Acinetobacter baumannii. Hospitals have long served as reservoirs for the transmission of pathogenic bacteria, and this has become a problem in Kuwait. Unfortunately, very little research has been devoted exclusively to investigating Acinetobacter baumannii prevalence, resistance and pathogenicity in Kuwaiti Hospitals. Research on the local population in Kuwaiti Hospitals is important and beneficial to physicians, to help better diagnose and treat the infections, and prevent any outbreaks from spreading. Aim: This study aimed to examine the resistance and identify the genotypic changes in the organism as it spreads through Mubarak Al-Kabeer Hospital. Methods: A total of 88 Acinetobacter baumannii samples were collected from the Mubarak Al- Kabeer Hospital, over a three year period, 2006-2008, and they were identified phenotypically, by Vitek-2 systems, and then genotypically by PCR amplification of blaOXA-51-like gene. The resistance to the carbapenems: imipenem and meropenem, was identified by use of the Minimal Inhibitory Concentration (MIC) test. Pulsed field gel electrophoresis (PFGE) was used to type the strains and classify them into clonal groups. Identification of the blaOXA-51-like gene types of each of the isolates was done via gene sequencing. Results: All 88 isolates were identified as Acinetobacter baumannii by Vitek-2 system and were shown to carry a blaOXA-51-like gene. Resistance to Imipenem was found in 31.8% of the isolates, whereas resistance to meropenem was found in 23.8% of the isolates. Overall carbapenem resistance was observed in 55.7% of the total isolates, with a slight increase in resistance of isolated over the 3 years of collection. In all, there were 10 different blaOXA-51-like genes identified. The sequences of these genes suggested there was some degree of real-time evolution of the blaOXA-51-like genes during the study period. There were four main clonal clusters. There were three main European clones (blaOXA-66, blaOXA-69, and blaOXA-71) plus a new clone with blaOXA-51-like genes with sequences clustered around the blaOXA-98 gene. Conclusion: This study has shown four major clones were found in the hospital during the study period, three of the clones were closely associated with those found in Europe and elsewhere in the world, and one new clone, containing a blaOXA-98-like gene that appears to be more prevalent in this part of Asia. The gradual increase in resistance to carbapenems over the study period warrants further attention and study of this resilient bacterium.