Nasal colonization by CA-MRSA (Community-Acquired Methicillin-Resistant Staphylococcus aureus) has been linked to HIV disease. As such, a study was conducted in order to determine the prevalence of MRSA colonization among HIV-infected individuals and identify the factors that correlate with MRSA nasal colonization in this population.
In order to determine the prevalence of MRSA colonization, nasal samples were taken from preselected HIV-infected individuals (i.e., HIV seropostive, active clinic patients). A culturette swab was used to collect samples from both the anterior nares of each patient. Another set of samples, which was collected from both axilla of the same individuals, was obtained for comparison. Swabs were plated in on BBL CHROMagar MRSA, a medium that is both selective and differential especially designed for the purpose of qualitative detection of MRSA nasal colonization. Bacterial colonies that were found to be consistent with MRSA on the CHROMagar plates were then subjected to a confirmatory test, the Staphaurex test, for the presence of coagulase and/or protein A.
Result showed that the prevalence of MRSA nasal colonization was 10%. This rate was observed to be relatively higher compared with the previous studies. Meanwhile, the prevalence of axillary colonization was found to be 0.7%. Because of very low prevalence, it can be surmised that colonization of axillae is not significant in the pathogenesis of CA-MRSA infections among HIV-infected individuals.
In a multivariate logistic regression model, analyses showed that lower CD4 count and prior infection with MSSA or MRSA were each associated with MRSA nasal colonization. Patients with MRSA infections were observed to have lower CD4 cell counts. A low CD4 count was found to be associated with high MRSA colonization risk. The same is true for prior infection with either MRSA or MSSA.
Use of antibiotics can lower the rate of MRSA colonization. Prior studies have shown that antistaphylococcal antibiotics have a protective effect on staphylococcal nasal colonization. One type of antibiotics from which CA-MRSA isolates are almost universally susceptible is Trimethoprim-sulfamethoxazole (T/S). In the current study, a comparison on the number of individuals getting MRSA infections was made between T/S recipients and non-recipients. Results showed that 0 of 29 T/S recipients were colonized with MRSA whereas 15 of 117 non-recipients had infections. The protective effect of T/S on CA-MRSA infections has been confirmed in previous studies.
The prevalence of MRSA nasal colonization has been found to be significant among HIV-infected individuals. Factors that correlate with MRSA nasal colonization were identified as: (1) CD4 cell count; (2) prior staphylococcal infection (MSSA or MRSA); and (3) use of antibiotics (primarily T/S).
Aside from the prevalence of and the factors correlating with MRSA nasal colonization, the role of nasal colonization and other body sites on subsequent infection and utility of decolonization should be addressed in future studies.
In order to determine the prevalence of MRSA colonization, nasal samples were taken from preselected HIV-infected individuals (i.e., HIV seropostive, active clinic patients). A culturette swab was used to collect samples from both the anterior nares of each patient. Another set of samples, which was collected from both axilla of the same individuals, was obtained for comparison. Swabs were plated in on BBL CHROMagar MRSA, a medium that is both selective and differential especially designed for the purpose of qualitative detection of MRSA nasal colonization. Bacterial colonies that were found to be consistent with MRSA on the CHROMagar plates were then subjected to a confirmatory test, the Staphaurex test, for the presence of coagulase and/or protein A.
Result showed that the prevalence of MRSA nasal colonization was 10%. This rate was observed to be relatively higher compared with the previous studies. Meanwhile, the prevalence of axillary colonization was found to be 0.7%. Because of very low prevalence, it can be surmised that colonization of axillae is not significant in the pathogenesis of CA-MRSA infections among HIV-infected individuals.
In a multivariate logistic regression model, analyses showed that lower CD4 count and prior infection with MSSA or MRSA were each associated with MRSA nasal colonization. Patients with MRSA infections were observed to have lower CD4 cell counts. A low CD4 count was found to be associated with high MRSA colonization risk. The same is true for prior infection with either MRSA or MSSA.
Use of antibiotics can lower the rate of MRSA colonization. Prior studies have shown that antistaphylococcal antibiotics have a protective effect on staphylococcal nasal colonization. One type of antibiotics from which CA-MRSA isolates are almost universally susceptible is Trimethoprim-sulfamethoxazole (T/S). In the current study, a comparison on the number of individuals getting MRSA infections was made between T/S recipients and non-recipients. Results showed that 0 of 29 T/S recipients were colonized with MRSA whereas 15 of 117 non-recipients had infections. The protective effect of T/S on CA-MRSA infections has been confirmed in previous studies.
The prevalence of MRSA nasal colonization has been found to be significant among HIV-infected individuals. Factors that correlate with MRSA nasal colonization were identified as: (1) CD4 cell count; (2) prior staphylococcal infection (MSSA or MRSA); and (3) use of antibiotics (primarily T/S).
Aside from the prevalence of and the factors correlating with MRSA nasal colonization, the role of nasal colonization and other body sites on subsequent infection and utility of decolonization should be addressed in future studies.
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