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JAC Advance Access published online on August 15, 2008
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkn327
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© The Author 2008. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

Original research

First report of qacG, qacH and qacJ genes in Staphylococcus haemolyticus human clinical isolates

J. E. Correa1, A. De Paulis2, S. Predari2, D. O. Sordelli1 and P. E. Jeric1,*

1 Departamento de Microbiología, Inmunología y Parasitología, Facultad de Medicina, Universidad de Buenos Aires (UBA), Buenos Aires, Argentina 2 Instituto de Investigaciones Alfredo Lanari, Universidad de Buenos Aires (UBA), Buenos Aires, Argentina

Received 10 April 2008; returned 14 June 2008; revised 11 July 2008; accepted 18 July 2008

* Corresponding author. Tel: +54-11-5950-9500 ext. 2180; Fax: +54-11-4964-2554; E-mail: paolajeric{at}yahoo.com

Objectives: To investigate phenotypically and genotypically the presence of MDR efflux pumps in 21 clinical isolates of Staphylococcus haemolyticus collected over a period of 10 years.

Methods: MICs of different antibiotics and biocides were determined by the broth dilution method in the presence/absence of carbonyl cyanide-m-chlorophenylhydrazone (CCCP), an efflux pump inhibitor. PCR followed by sequencing was performed to detect the qac genes that encode for antiseptic resistance. Clonal relationships were determined by PFGE SmaI patterns using a standard protocol.

Results: All the isolates were resistant to gentamicin, 15 to erythromycin, 18 to ciprofloxacin, 7 to chloramphenicol and 1 to tetracycline. They showed higher susceptibility to antibiotics when they were exposed to CCCP. The MICs of ethidium bromide, SDS and benzalkonium chloride were also decreased, whereas the MIC of triclosan was decreased in only four isolates in the presence CCCP. Of the 21 isolates, qacA/B was detected in 5 isolates, smr in all of the isolates, qacG in 11 isolates, qacH in 10 isolates and qacJ in 4 isolates. PFGE analysis of the 21 isolates clustered them into 14 clones at 90% similarity corresponding to differences of between 7 and 16 bands among the clones.

Conclusions: The efflux mechanism seems to be an important mechanism to confer resistance to antibiotics and biocides through MDR pumps. It was observed that several qac genes coexist in some of the isolates and seem to act simultaneously in the removal of different compounds out of the bacterial cell. The qac genes are horizontally spread among different clones.

Key Words: S. haemolyticus , multidrug resistance , efflux pumps


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