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Brazilian Journal of Infectious Diseases

versión impresa ISSN 1413-8670

Braz J Infect Dis vol.16 no.3 Salvador mayo/jun. 2012 



Drug resistance profile of staphylococci isolated from asymptomatic adults



Claudia Christianne Barros de Melo Medeiros; Magna Suely Freitas de Araujo; Henrique Douglas Melo Coutinho; José Pinto de Siqueira Júnior; Humberto Medeiros Barreto*

Universidade Federal do Piauí, Floriano, Piauí, Brazil



Dear Editor,

The emergence of multi-drug resistant (MDR) strains is a worldwide phenomenon, due to the selective pressure exerted by extensive use of antibiotics, which has hindered the treatment of staphylococcal infections. The anterior nasal vestibule and the throat are the main reservoirs of S. aureus, including methicillin-resistant S. aureus (MRSA) strains, which show a genetic predisposition to develop MDR phenotype and are a common cause of hospital- and community-acquired infections worldwide.1,2 The maintenance of the asymptomatic nasal carrier state is considered a risk factor for staphylococcal disease acquisition and staphylococci transmission to susceptible individuals.

The resistance profile of staphylococci present in the nasal vestibule of asymptomatic carriers was analyzed in the city of Natal, northeastern Brazil. These strains were isolated from nasal secretion samples collected from 52 students of dentistry. 59.6% (31/52) of isolates were identified as S. aureus, of which 6.5% (2/31) were MRSA strains. The prevalence of nasal carriage of S. aureus estimated in the present study was higher than that found by other studies in Brazilian university students,3 in the United States' general population,4 and in Malaysian adults.5

Resistance to erythromycin was found in 25.8% (8/31) of S. aureus strains, and 9.7% (3/31) of these had inducible resistance phenotype. All tetracycline resistant strains had a phenotype compatible with plasmid inheritance. The strains of isolated S. aureus and coagulase-negative staphylococci had a significant percentage of resistance to penicillin G, erythromycin, and clindamycin. Resistance to two or more classes of antibiotics was found in 29.0% (9/31) of the S. aureus strains, and was also observed in coagulase-negative staphylococci strains (Table 1).

It was found that a significant percentage of clinically healthy adults were asymptomatic carriers of S. aureus, including MDR strains. This finding may probably be attributable to indiscriminate use of antibiotics. These results emphasize the importance of effective control measures to reduce the misuse of antimicrobial agents.


Conflict of interest

All authors declare to have no conflict of interest.



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2. Silva HA, Abdallah VOS, Carneiro CL, Filho PPG. Infection and colonization by Staphylococcus aureus in a high risk nursery of a Brazilian teaching hospital. Braz J Infect Dis. 2003;7:381-6.         [ Links ]

3. Prates KA, Torres AM, Garcia LB, Ogatta SF, Cardoso CL, Tognim MC. Nasal carriage of methicillin-resistant Staphylococcus aureus in university students. Braz J Infect Dis. 2010;14:316-318.         [ Links ]

4. Mainous AG, Hueston JW, Everett CJ, Diaz VA. Nasal carriage of Staphylococcus aureus and methicillin-resistant S. aureus in the United States, 2001-2002. Ann Fam Med. 2006;4:132-7.         [ Links ]

5. Choi SC, Yin CS, Bakar AA, et al. Nasal carriage of Saphylococcus aureus among healthy adults. J Microbiol Immunol Infect. 2006;39:458-64.         [ Links ]



Received 19 June 2011
Accepted 16 July 2011



* Corresponding author. Campus Amílcar Ferreira Sobral, BR 343, KM 3.5, Bairro Meladão, Floriano, PI, 64800-000, Brazil. E-mail address:

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