Introduction
Healthcare-associated infections are an important cause of morbidity and mortality worldwide. Environmental contamination plays an important role in the nosocomial transmission of infections, especially for Alert and multidrug resistant organisms. Several collection methods have been already described including swab or sponge samples, enrichment medium and contact plates. This study aims to compare a swab culture method (Copan FLOQSwabs® and SRK® medium) and a contact plate culture method (RODAC plate) for recovery of gram positive and negative bacteria from different patterns of environmental surfaces, to establish an internal protocol.
Methods
A 0.5 McFarland suspensions of methicillin-resistance staphylococcus aureus (MRSA, ATCC 43300) and Escherichia coli (ATCC 25922) were prepared. 25 µl aliquots of suspensions, diluted previously, were spread on 5x5 cm pieces of stainless steel and pharma wall for E. coli and MRSA, respectively. FLOQSwabs® moistened with SRK® medium were used to swab 25 cm2 areas. RODAC plates (Thermo Scientific™ Tryptone Soya Agar with disinhibitor, 24 cm2) were applied for 10 s on surface, then incubated. After sampling, swabs were immediately inserted into 1 ml of SRK medium, then 100 µl were inoculated into Blood agar plates and incubated overnight. Tests were performed in triplicate. Data were reported as CFU/cm2.
Results
Overall, target organisms were recovered from every environmental surfaces. An average value of 1.8 CFU was obtained with RODAC plates, starting from E. coli suspension spread on steel surface. In parallel, 2.1 CFU were obtained when specimens were collected by FLOQSwabs® and SRK® medium. Concerning the MRSA suspension, 1.4 and 1.7 CFU were obtained from contact plates and FLOQSwabs® in SRK® medium, respectively.
Conclusion
In conclusion, FLOQSwabs® with SRK® medium recovered slightly more amount of microorganisms than RODAC plates. Moreover, flocked swab with transport medium may be preferred due to the ability to collect specimens from irregular and large surfaces, to make dilutions before plating and for potential cost savings.