OXA β-Lactamases

Abstract

SUMMARY The OXA β-lactamases were among the earliest β-lactamases detected; however, these molecular class D β-lactamases were originally relatively rare and always plasmid mediated. They had a substrate profile limited to the penicillins, but some became able to confer resistance to cephalosporins. From the 1980s onwards, isolates of Acinetobacter baumannii that were resistant to the carbapenems emerged, manifested by plasmid-encoded β-lactamases (OXA-23, OXA-40, and OXA-58) categorized as OXA enzymes because of their sequence similarity to earlier OXA β-lactamases. It was soon found that every A. baumannii strain possessed a chromosomally encoded OXA β-lactamase (OXA-51-like), some of which could confer resistance to carbapenems when the genetic environment around the gene promoted its expression. Similarly, Acinetobacter species closely related to A. baumannii also possessed their own chromosomally encoded OXA β-lactamases; some could be transferred to A. baumannii , and they formed the basis of transferable carbapenem resistance in this species. In some cases, the carbapenem-resistant OXA β-lactamases (OXA-48) have migrated into the Enterobacteriaceae and are becoming a significant cause of carbapenem resistance. The emergence of OXA enzymes that can confer resistance to carbapenems, particularly in A. baumannii , has transformed these β-lactamases from a minor hindrance into a major problem set to demote the clinical efficacy of the carbapenems.

Significant spread of extensively drug-resistant Acinetobacter baumannii genotypes of clonal complex 92 among intensive care unit patients in a university hospital in southern Iran

“…CC92 is highly prevalent throughout Asia, and it is the CC with the widest global distribution [11]. Overall, our findings corroborate previous surveys conducted in Europe, where the majority of outbreaks have been associated with CRAB producing oxacillinase OXA-23 and belonging to ICL2 [12] Similarly, in a recent study performed at a referral burns centre in Tehran, the majority of CRAB isolates assessed belonged to CC92 and carried class I integrons and OXA-23-like carbapenemase [16].…”

“…The OXA-23-like type was the first group of these betalactamses to be identified, interestingly coinciding with the introduction of carbapenems in 1985 [10]. Present in transposons, these genes have rapidly spread in successful clonal linages of A. baumannii and presently represent the predominant mechanism of carbapenem resistance, having a huge impact on the ability to treat A. baumannii infections globally [11]. Characterization of the local molecular epidemiology of A. baumannii strains involved in hospital-associated infections is critical when determining the disease burden and magnitude of nosocomial transmission related to these bacteria.…”

Molecular characterisation of multidrug-resistant Pseudomonas aeruginosa from a private hospital in Durban, South Africa

“…GES-2 hydrolyses extended spectrum cephalosporins and imipenem, to a minor extent 24 explaining the resistance to ceftazidime but the high resistance to the carbapenems may be attributed to resistance mechanisms other than β-lactamases such as impermeability and/or efflux. 25 VIM-2, a derivative of VIM-1, possesses the widest substrate for hydrolysing several antimicrobial agents such as carbapenems, cephalosporins and penicillin.…”

Сarbapenemase-Producing Gram-Negative Bacteria in a Specialized Hospital of St. Petersburg

“…VIM-продуцирующий штамм P. aeruginosa, выделенный в нашем ис-следовании, имеет значительно меньший уро-вень резистентности с МИК обоих карбапене-мов 16 мкг/мл. У всех штаммов A. baumannii выявлен ген карбапенемазы OXA51, что соответствует литературным данным о том, что наличие гена bla OX A-51 в геноме A. baumannii является видовым признаком этой бактерии [15]. Ген bla OX A-51 , имеет хромосомную локализацию, и если не изменен геномными перестройками в промоторной области, слабо экспрессирует-ся и не придает бактерии резистентный к кар-бапенемам фенотип [15].…”

“…У всех штаммов A. baumannii выявлен ген карбапенемазы OXA51, что соответствует литературным данным о том, что наличие гена bla OX A-51 в геноме A. baumannii является видовым признаком этой бактерии [15]. Ген bla OX A-51 , имеет хромосомную локализацию, и если не изменен геномными перестройками в промоторной области, слабо экспрессирует-ся и не придает бактерии резистентный к кар-бапенемам фенотип [15]. Этим может объяс-няться тот факт, что штамм № 12, в котором обнаружен только ген bla OX A-51 , чувствителен к обоим протестированным карбапенемам.…”