Methods: Fourth Year Dental Students participated voluntarily. All information collected remained confidential (IRB 07-9-64). There were two microbial samplings – prior to disinfection and then after disinfection. Three cotton swabs moistened with PBS (0.85 M, pH 7.2) sampled the entire top surface of each laptop. The swabs went into 2.0 mL of PBS and then vortexed. Spiral plating of specimens onto two enriched trypticase soy agar (ETSA) plates and a mannitol salt agar (MSA) plate followed. Incubation was at 37˚C for 48 hours. One ETSA and the MSA plate were incubated aerobically, the other ETSA plate underwent anaerobic incubation. Then, all colony types underwent sub-culturing in trypticase soy broth with 0.25% (w/v) glucose. Aerobic incubation was at 37˚C for 48 hours. Spread plating of 0.1 mL specimens involved four types of media – MSA, cefotamine screening test (ETSA with antibiotic discs), oxacillin resistance screening agar and BBL CHROMagar (selective and differentiating for MRSA). Aerobic incubation was at 35˚C for 48 hours. After the initial sampling, three weekly disinfection processes occurred. Sampling of the laptops was the same as just described.
Results: Forty-two laptops completed all phases of the study. Specimens from pre-cleaned laptops produced 148 isolates of which 41 were S. aureus. Seven laptops yielded eleven MRSA isolates of which eight were also cefotamine resistant. Sampling after disinfection produced 114 isolates of which 49 were S. aureus. Six laptops produced eight MRSA isolates of which five were also cefotamine resistant.
Conclusion: Overall, 14.3% of all laptops evaluated produced drug resistant S. aureus isolates. Three weekly disinfection procedures did not reduce the number of drug resistant isolates present.
Partial funding of this study was from the ICR-Student Research Fellowship.