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BMC Res Notes. 2011 Oct 27;4:453. doi: 10.1186/1756-0500-4-453.

Detection of macrolide and disinfectant resistance genes in clinical Staphylococcus aureus and coagulase-negative staphylococci.

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Laboratoire d'Analyse, Traitement et Valorisation des Polluants de l'Environnement et des Produits, Faculté de Pharmacie, Monastir, Tunisia.



Staphylococcus aureus and Coagulase-negative staphylococci (CoNS) are a major source of infections associated with indwelling medical devices. Many antiseptic agents are used in hygienic handwash to prevent nosocomial infections by Staphylococci. Our aim was to determine the antibiotic susceptibility and resistance to quaternary ammonium compound of 46 S. aureus strains and 71 CoNS.


S. aureus (n = 46) isolated from auricular infection and CoNS (n = 71), 22 of the strains isolated from dialysis fluids and 49 of the strains isolated from needles cultures were investigated. Erythromycin resistance genes (ermA, ermB, ermC, msrA and mef) were analysed by multiplex PCR and disinfectant-resistant genes (qacA, qacB, and qacC) were studied by PCR-RFLP.


The frequency of erythromycin resistance genes in S. aureus was: ermA+ 7.7%, ermB+ 13.7%, ermC+ 6% and msrA+ 10.2%. In addition, the number of positive isolates in CoNS was respectively ermA+ (9.4%), ermB+ (11.1%), ermC+ (27.4%), and msrA+ (41%). The MIC analyses revealed that 88 isolates (74%) were resistant to quaternary ammonium compound-based disinfectant benzalkonium chloride (BC). 56% of the BC-resistant staphylococcus isolates have at least one of the three resistant disinfectants genes (qacA, qacB and qacC). Nine strains (7.7%) among the CoNS species and two S. aureus strains (2%) harboured the three-qac genes. In addition, the qacC were detected in 41 strains.


Multi-resistant strains towards macrolide and disinfectant were recorded. The investigation of antibiotics and antiseptic-resistant CoNS may provide crucial information on the control of nosocomial infections.

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