Staphylococcus aureus Nasopharyngeal Carriage Rates and Antimicrobial Susceptibility Patterns Among Health Care Workers and Their Household Contacts

Abstract

Dissemination of Staphylococcus aureus within hospitals by nasopharyngeal carriage of the organism by health care workers (HCW) has been well characterized for over 40 years, but physicians and nurses must be reminded of the extent of the problem. To determine the level of colonization among HCW in one hospital in Brazil, and to examine the potential spread to household contacts and the surrounding community, nasal swabs for S. aureus were done on 200 HCW, 87 household contacts, and 77 members of the community. The frequency of positive cultures in each group was recorded, and the organims were then tested for susceptibility to a panel of antibiotics. The average level of antibiotic resistance was calculated for each organism using a scoring technique termed rate of bacterial resistance (RBR). Phage typing was also done. The frequency of colonization was 63/200 (31.5%) among HCW, 27/87 (31%) among their household contacts, and 14/77 (18.1%) in members of the community (p>0.05). The level of antibiotic resistance (RBR) was significantly higher among HCW than among household contacts or the community. Phage typing revealed that 40.7% of isolates had a common phage pattern between HCW and household contacts. Among household contacts, the level of antimicrobial resistance was the same for the shared phage types as for the unique types. We conclude that nasopharyngeal carriage among HCW remains a problem, that the carriage rate is also seen among household contacts, but not in the community. Increased levels of antimicrobial resistance in the strains carried by HCW indicate that the spread of resistant organisms occurs by this mechanism. Careful control of S. aureus among HCW is an important hospital practice.