[Qnr and aac (6')-Ib-cr types quinolone resistance among Enterobacteriaceae isolated in Annaba, Algeria]

To show the emergence of the qnr and aac (6')-Ib-cr genes in nalidixic acid resistant enterobacteria isolated at Annaba city in Algeria.

Enterobacterial strains (n=25) resistant to nalidixic acid have been isolated at the microbiology laboratory of the Annaba city hospital in Algeria Antibiotic susceptibility (disc diffusion method and MIC) and screening for Extended Spectrum Beta-Lactamase (ESBL) were performed according to the French Society for Microbiology guidelines. Characterization of quinolone resistance genes (qnrA, qnrB, qnrS, aac(6')-Ib-cr) was investigated by PCR. Identification of ESBL (TEM, SHV, CTX-M1, CTX-M2, CTX-M8 and CTX-M9 groups) was performed by PCR. Identification of plasmid AmpC beta-lactamases was performed by multiplex PCR. All PCR products were sequenced on both strands. Conjugation experiments were performed using azide-resistant Escherichia coli K₁₂J₅ as a recipient strain.

Among the 25 strains selected, 24 were resistant to at least four antibiotics. Six strains showed an ESBL phenotype. The qnr gene (B1 type) was found in two ESBL producing strains with at least two types of bla gene. The aac (6')-Ib gene was detected in three strains, one with the aac (6') Ib-cr variant. With specific primers, we have shown that qnrB1, CTX-M-28, TEM1, aac (6')-Ib-cr was cotransferred together and that these genes are carried by conjugative plasmids of high molecular weight.

The emergence of combination of resistance genes may pose a public health problem. Thus, a policy of surveillance of resistance seems necessary.