Vancomycin intermediate resistant Staphylococcus aureus in the nasal cavity of asymptomatic individuals: a potential public health challenge

Abstract

Background: The potential of transmitting multidrug resistant Staphylococcus aureus from asymptomatic individuals to healthy individuals could constitute a great challenge to antimicrobial therapy. Methods: The antibiograms of the S. aureus from asymptomatic individuals were determined by disk diffusion and agar dilution assay techniques with different antibiotics and vancomycin. Results: Of the 152 S. aureus isolated, (59)38.8% isolates were multi-drug resistant strains. Streptomycin was the most effective and inhibited (135)88.82% of the isolates while ceftazidime inhibited (24)15.8% of the isolates. While (82)54.0% of the isolates inhibited by cefuroxime had resistant colonies within their inhibition zones (Rc) and ofloxacin inhibited (100)65.8% of the isolates without having resistant colonies within the inhibition zones, ceftazidime inhibited (7)4.6% of the isolates with resistant colonies within the inhibition zones. Subjecting the isolates to vancomycin showed that (27)17.8% were resistant to 2 µg/ml, (43)28.3% were resistant to 4 µg/ml and (27)17.8% of the isolates were simultaneously resistant to both concentrations of vancomycin. Although (100)65.8% of the isolates had MARindex ≥0.2, (52)34.2% of the isolates had MARindex ≤ 0.2 and (65)428% of the isolates were considered multidrug resistant strains. Conclusion: The isolation of multi-drug and vancomycin intermediate resistant strains of S. aureus in high percentage, in this study, presents a great threat to clinicians and general populace. The vancomycin intermediate resistant S. aureus (VISA) in asymptomatic individuals could be a critical concern to the therapeutic dilemma to be added to the presence of multi-drug resistance. A more sustainable therapy must be in place to prevent its dissemination or the outbreak of its infection. Keywords: Antibacterial activity; multidrug resistance; VRSA; VISA; vancomycin