Genome-based insights into the resistomes and mobilomes of two Providencia rettgeri strains isolated from wound infections in Madagascar.

Objectives: A molecular analysis was performed of two Providencia rettgeri (P. rettgeri) strains (Pr 297 and Pr 269) collected in 2007 and 2009 from wound swabs of patients admitted to the intensive care units at Joseph Ravoangy Andrianavalona hospital and the Military Hospital in Antananarivo, Madagascar.

Methods: The two P. rettgeri isolates were subjected to susceptibility testing. Whole genome sequencing was performed to characterise the antibiotic resistance genes, genomic islands and mobilomes (integrons, plasmids and insertion sequences).

Results: All isolates were found to be multidrug-resistant. Antibiotic-resistant genes described were amongst eight different classes of antimicrobial agents. Thirty insertion sequences and twelve genomic islands were predicted in each genome. Class 1 and class 2 integrons were found in both genomes, with gene cassette regions encompassing arr-2 - cmlA5 - bla - ant (3")-Ia and dfrA1 - sat2 - ant (3")-Ia - orfX, respectively. IncA/C2, ColM and ColE1-like plasmids were described harbouring bla, qnrD and aac(6')-Ib-cr4 genes, respectively. Phylogenetic analysis showed that Pr 297 and Pr 269 isolates were genetically identical and clustered with P. rettgeri strains described in the USA and Spain.

Conclusions: It is believed that this is the first molecular characterisation of wound infection pathogens from Madagascan patients and the first description of P. rettgeri co-producing CMY-30, OXA-10 and AAC(6')-Ib-cr4 enzymes. The diversity of the resistance determinants and mobile genetic elements was probably due to extensive horizontal gene transfer events, highlighting the need to conduct further molecular monitoring studies to understand the genomic plasticity of resistant bacteria in Madagascan hospitals.