Our study revealed that OXA-23 carbapenemase was present in A. baumannii isolates in Antananarivo. OXA-23-type carbapenemase-producing A. baumannii are becoming increasingly widespread, with reports from Europe [25–27], South America [9, 13, 28], or Asia [29–31]. In 2002, 49 strains of imipenem resistant A. baumannii producing the carbapenenase OXA-23 were isolated in South Africa . Many strains of OXA-23 producing A. baumannii from the same clone were responsible for an epidemic of nocomial infection from 2005 to 2007 in Tunisia .
As in the present study, such isolates usually exhibit resistance to many antimicrobials, creating a serious problem for choice of therapy. In our study, patients with skin infections caused by carbapenem-resistant A. baumannii received local treatments and most survived without sequelae. On the contrary, among patients with urinary, pulmonary or blood stream infections who received only antibiotics ineffective on the A. baumannii strains isolated (third generation cephalosporins, ciprofloxacin or amoxicillin-clavulanic acid), the rate of mortality was high. Indeed 2 of 3 patients with bloodstream infection, 4 of 8 patients with pulmonary infection and 2 of 10 patients with urinary infection died.
In this study, the OXA-23-producers originated from two clones. According to Rep-PCR patterns, it appears that OXA-23-producing CRAB belonging to two predominant genotypes spread between public and private hospitals in Antananarivo. Different studies have already shown that clones of CRAB may spread in a town  or even a country . The occurrence of common Rep-PCR types in OXA-23-producing A. baumannii from various hospitals in Antananarivo suggests that dissemination of isolates contributes to the increase in prevalence of CRAB. Dissemination of CRAB in the community could be favoured by poor health facilities and the transfer of infected or colonised patients from a hospital to another. However, this is rarely the case in Antananarivo. Sharing of common healthcare staff is more likely. Indeed staff from public hospitals also works together in the various clinics of Madagascar. This hypothesis has already been evoked to explain the spread of clonal strains between different hospitals [13, 35]. If poor sanitary conditions probably explain how these CRAB clones can spread, it does not explain how these clones appeared in Antananarivo. One can suppose that resistant clones were introduced by patients treated in a developed country (hospitalization in Reunion Island is rather frequent for Malagasy patients). However, since carbapenem are not available in Madagascar, resistance to these drugs should not confer any advantage to these clones. Therefore the selection of these clones is probably due to their resistance to most drugs used in Madagascar than to resistance to imipenem.