Carbapenem Resistance and Acinetobacter baumannii in Senegal: The Paradigm of a Common Phenomenon in Natural Reservoirs

Incidence of carbapenem-resistant Acinetobacter baumannii is rising in several parts of the world. In Africa, data concerning this species and its resistance to carbapenems are limited. The objective of the present study was to identify the presence of A. baumannii carbapenem-resistant encoding genes in natural reservoirs in Senegal, where antibiotic pressure is believed to be low. From October 2010 to January 2011, 354 human head lice, 717 human fecal samples and 118 animal fecal samples were screened for the presence of A. baumannii by real time PCR targeting blaOXA51-like gene. For all samples positive for A. baumannii, the carbapenemase-hydrolysing oxacillinases blaOXA23-like and blaOXA24-like were searched for and sequenced, and the isolates harbouring an oxacillinase were genotyped using PCR amplification and sequencing of recA gene. The presence of A. baumannii was detected in 4.0% of the head lice, in 5.4% of the human stool samples and in 5.1% of the animal stool samples tested. No blaOXA24 gene was detected but six fecal samples and three lice were positive for blaOXA23-like gene. The blaOXA23-like gene isolated in lice was likely a new oxacillinase sequence. Finally, the A. baumannii detected in stools were all of recA genotype 3 and those detected in lice, of recA genotype 4. This study shows for the first time a reservoir of blaOXA23-like-positive gene in human head lice and stool samples in Senegal

CLUSTAL W2 nucleotidic alignment of the three <i>bla</i>_OXA23-like-positive <i>A. baumannii</i> found in lice (indicated louse 1 to 3) and of the six <i>bla</i>_OXA23-like-positive <i>A. baumannii</i> found in human stool samples (indicated stool 1 to 6).

<p>The <i>bla</i>_OXA23-like gene AJ132105 was taken as reference.</p

Oligonucleotide primers and TaqMan^* fluorescent probe sequence used for PCR and sequencing of <i>Acinetobacter baumannii.</i>

*<p>Applied Biosystems, Courtaboeuf, France.</p

Head lice collection in Senegal.

<p><b><i>A:</i></b> Head lice collection areas (Dakar, Kaolack, Sine-Saloum, Dielmo and Ndiop). <b><i>B:</i></b> Head lice collection sites in the suburbs of the Dakar region. Diamonds: number of lice positive for <i>A. baumannii</i>; green diamonds: <i>A. baumannii</i> negative for the <i>bla</i>_OXA23-like gene<i>;</i> red diamonds: <i>A. baumannii</i> positive for the <i>bla</i>_OXA23-like gene.</p

Carbapenemase-hydrolysing oxacillinases phylogenetic tree using neighbour-joining method.

<p>*, partial <i>bla</i>OXA-23 sequences found in Uncultured <i>Acinetobacter</i> isolated from groundwater collected from deep tube well in Nepal.</p

Repartition of stool samples and <i>A. baumannii</i>-positive stool samples.

<p>Repartition of stool samples and <i>A. baumannii</i>-positive stool samples.</p

PFGE and hybridization analysis.

<p><b>A.</b> Pulsed field gel electrophoresis (PFGE) profiles obtained for the two <i>Acinetobacter baumannii</i> strains isolated from the stool samples from two patients living in Mbao. The Low Range PFG Marker (LRM) was used as molecular weight marker. <b>B.</b> Southern blot profile obtained for the two <i>Acinetobacter baumannii</i> strains isolated from the stool samples from two patients living in Mbao after hybridization against the <i>bla</i>_{OXA-23 like} DIG-labeled probe. Arrows indicate putative plasmids.</p