[Efficacy of biocides against hospital isolates of Staphylococcus sensitive and resistant to methicillin, in the province of Buenos Aires, Argentina].

OBJECTIVE

To assess the response to the action of different antiseptics and disinfectants usually used in Argentinian hospitals of hospital staphylococci sensitive and resistant to methicillin. To test the effectiveness of the biocides by measuring their effective bactericidal concentrations, and to determine whether there is any correlation between biocide resistance and methicillin resistance in this bacterial population.

METHODS

The action of seven biocides was tested against 25 strains of nosocomial Staphylococcus spp. sensitive and resistant to methicillin, and in Staphylococcus aureus ATCC 6538. Hospital strains were obtained from April, 2000 to May, 2002, from clinical samples (blood culture, urine culture, catheter tip or abscess) from male and female inpatients and outpatients at two tertiary hospitals. After isolation, antibiotic sensitivity was tested with the agar diffusion method of Kirby and Bauer. The action of hospital biocides on the strains was studied with the Kelsey-Sykes test, which establishes the effective bactericide concentrations of these compounds.

RESULTS

The results showed that the response of strains sensitive and resistant to methicillin varied in comparison to the collection strain. Chlorhexidine digluconate, povidone iodine, weak tincture of iodine and alkaline glutaraldehyde were effective against most strains, regardless of whether they were sensitive or resistant to methicillin.

CONCLUSIONS

We found no indication of a relationship between resistance to methicillin and resistance to biocides. Our study shows that further research is needed to evaluate the efficacy of chemical agents against microorganisms that have been exposed to antibiotic therapies.