Antimicrobial Resistance and Detection of Biofilm in Staphylococcus aureus Isolates from Casablanca

Aims: The ability of biofilm formation seems to play an essential role in the virulence of Staphylococcus aureus. The aims of the present study were to test the sensitivity of the clinical isolates of Staphylococcus aureus to antibiotics, detect the ability of these strains to form biofilm and evaluate the correlation between biofilm formation by clinical isolates and the resistance to antibiotics.

Place and Duration of Study: Laboratory of Virology, Microbiology and Quality/ Eco-toxicology and Biodiversity, Faculty of Sciences and Techniques Mohammedia, University Hassan II Casablanca and laboratory of Bacteriology, Virology and Hygiene, Ibn Rochd University Hospital, Casablanca during October 2015 and January 2016.

Methodology: A total of 117 clinical isolates of staphylococci were collected at the University Hospital Ibn Rochd of Casablanca, Morocco and examined for antimicrobial susceptibility, presence of mecA gene and biofilm formation. Staphylococci species identification and antibiogram were performed by standard procedures using disk diffusion method. The methicillin resistance was confirmed by PCR using mecA specific primers. The biofilm formation assay was realised by the tissue culture plate method (TCP).

Results: Among all strains collected, 74 were identified as Staphylococcus aureus. Out of 74 Staphylococcus aureus, 22 strains (29.7 %) were found methicillin resistant when tested with cefoxitin disc diffusion method. 20.3 %, 18.9 % and 13.5 % were classified as resistant to kanamicin, ciprofloxacin and erythromycin respectively. All strains were found resistant to penicillin G and sensitive to teicoplanin. All isolates resistant to methicillin by cefoxitin disc diffusion method were confirmed by presence the mecA gene by PCR. Of the 74 isolates 16 (21.6 %) were non adherent, 40 (54 %) weakly adherent, 12 (16.2 %) moderately adherent and 6 (8.1 %) strongly adherent.

Conclusion: The results of this study showed that there is a correlation between biofilm formation and resistance to all the antibiotics tested, except to teicoplanin, which was active against the all strains.