MDR A. baumannii is a problematic, multidrug-resistant pathogen identified in healthcare settings worldwide, especially in ICUs . A. baumannii has a notable ability to capture and express resistance genes. All resistance mechanisms including target modification, efflux pump expression, and enzymatic inactivation have been described in A. baumannii .
In the current study, five MDR A. baumannii strains were isolated over 1 week from the same ICU. All isolates showed the same phenotypic characteristics which prompted us to start a survey study of the antimicrobial susceptibility and clonal relationship of A. baumannii strains isolated from this ICU.
All our isolates were resistant to imipenem. The main role of the A. baumannii resistance to carbapenems is mediated by oxacillinases and, less frequently, by metallo-β-lactamases [4, 5].
OXA-24/40-like, and bla
OXA-58-like genes have been repetitively reported in A. baumannii outbreaks from diverse parts of the world. The localization of numerous β-lactamase genes on plasmids facilitates their horizontal mobilization from one bacterium to another [13, 14].
All our isolates harbored the bla
OXA-51-like gene, which is ubiquitous in A. baumannii . bla
OXA-23 was the most universally identified gene, while bla
OXA-24-like and bla
OXA-58-like genes were not detected in any strain. bla
OXA-23 is the most prevalent carbapenemase-encoding gene in the Mediterranean region. This might be explained by the higher carbapenemase activity of bla
OXA-23 and/or acquisition of carbapenem resistance through horizontal gene transfer [16–18]. The bla
OXA-23 gene was either encoded on the chromosome or on plasmids and was associated with four dissimilar genetic structures, with the most common being transposons Tn2006. bla
OXA-23 has been reported in different regions of the Middle East, The United Arab Emirates, Algeria, Libya, Bahrain, and recently, Qatar [16, 19].
Mugnier et al. found an isolate from Egypt harboring plasmid containing bla
OXA-23. This finding might indicate the prevalence of the genetic environment of bla
OXA-23 in Egyptian isolates . Moreover, a recent study including three Egyptian hospitals revealed the emergence and spread of bla
NDM-1 and bla
OXA-23 in addition to the co-occurrence of 16S rRNA methylase armA with bla
NDM-1 and bla
OXA-23 in 27 distinct sequence types, 11 of which were novel among A. baumannii clinical isolates .
Per MLST results, ST195, ST208, ST231, ST441, ST499, and ST723 were the most prevalent isolates. Another Egyptian study illustrated the large diversity found within the strains where ten distinct sequence types (STs) were identified, ST408–ST414, ST331, ST108, and ST208 . However, a study showed that the most prevalent sequence types in the gulf area were ST195, ST208, ST229, ST436, ST450, ST452, and ST499 .
Taking into consideration that ST208 is the ancestor strain of several STs including ST89, ST88, ST190, ST225, and ST75, it has been identified in different parts of the world such as Japan, China, Thailand, Korea, Italy, Australia, Portugal, and the Czech Republic .
In conclusion, MDR A. baumannii strains harboring the bla
OXA 23-like gene were widely circulating in our ICU. MLST provided us with a powerful tool for identifying and epidemiologically typing our strains. Studying the epidemiology of HAIs is urgent to prevent the clonal dissemination of antibiotic-resistant pathogens, not only in hospital settings, but in the community, as well. Strict infection control measures and antimicrobial stewardship programs are necessary to contain the worldwide spread of MDR A. baumannii. Proving the clonal relation between clinical isolates emphasizes the importance of surveillance programs and strict IC measures that would influence decision-making and health policy.