The evolution of the resistance of Staphylococcus aureus found on healthcare workers correlated with local consumption of antibiotics.

OBJECTIVE

Correlate the evolution of the resistance of Staphylococcus aureus collected from healthcare workers with the local consumption of antibiotics. MATERIAN AND METHODS: Open prospective research. Study Site. General Reference Hospital with 200 beds in a 700,000 inhabitant region, in Ponta Grossa, Paraná, Brazil.

RESULTS

Two collections (samples) of Staphylococcus aureus isolates were obtained from healthcare-workers during an approximate four-year interval. Samples 1 (n= 200) and 2 (n= 270) had this bacterium in 63 (32%) and 90 (33%) of the patients, respectively. At the same time, the annual consumption of antibiotics in DDD/1,000 patient-days was determined. The variation of resistance was significantly smaller (m.s.d.=12.11) for gentamycin (p<0.01) and (m.s.d.=9.22) for Tobramycin (p<0.05). The correlation between variation in resistance and antibiotic consumption was not significant. Workers studied in the two samples showed a significant (p<0.01) frequency (chi2=10.44) for persistent nasal carriage and for non carriage. Methicillin resistant Staphylococcus aureus was found in 12 (6%) patients of sample 1 and 11 patients (4%) of sample 2.

CONCLUSION

Stability of resistance allows us to maintain therapeutic outlines. The variation in bacterial resistance in the twice-sampled population (n=105) indicated the selection pressure of the hospital environment. The resistance that was found is representative of the hospital microbiota; this relationship represents a biological model, based on the healthcare-workers' interaction with colonizing bacteria and nosocomial infections. New studies could improve this model for other bacteria, to determine the tendency for resistance and help guide the antibiotic use.