Staphylococcus aureus is associated with both nasocomial and community acquired infections 1. It is categorized as either methicillin-resistant S. aureus (MRSA), or methicillin-susceptible, based on the antimicrobials a strain is susceptible to in vitro 2. MRSA poses a public health challenge, in part because of its commensal nature on human skin, and mucous membranes 34. As such, MRSA is readily passed from person-to-person, especially in hospitals), and is often difficult to eradicate 567. At the same time, Antibiotic pressure has led to regular and unwittingly demands for antibiotic use, which has increased the risk of methicillin resistance 89. MRSA strains acquire resistance to beta-lactams and aminoglycosides, the common empirical regimens in sub-Saharan Africa 1011. Knowledge of locals antimicrobial susceptibility pattern is essential to select appropriate therapy; however lack of culture and susceptibility testing at most health facilities in resource-limited settings has resulted in widespread empiric therapy. Due to budgetary constraints and lack of programs supporting antimicrobial stewardship, screening for MRSA carriage among PLWHIV in Uganda is not done. This study reports the prevalence, risk factors and DST of asymptomatic MRSA nasal carriage among PLWHIV attending ART clinic at Nyenga hospital in central Uganda.

We enrolled 219 PLWHIV, and 58.4% (N=128) were female. The majority of participants were aged 26 to 35 years, (n=86, 39.27%), and 95.0%) were on ART (Table 1).

There were 98 (44.75%) cultures which exhibited growth. Of those, 41 (41.84%) isolates were of Staphylococcus aureus. Of these, 11 participants were found to have MRSA as measured by resistance to Cefoxitin, giving a prevalence of 5.02% (95% confidence interval: 3.67-7.02). Microbiologic results are described in Figure 1.

Analysis of the factors associated factors indicated that low CD4 cell counts and deteriorating World Health Organization (WHO) clinical stages were significantly associated with the risk of MRSA colonization. Participants whose CD4 cell counts were less than 500 cells/litre (p<0.05) and WHO clinical stages II (p=0.000), III (p=0.012) and IV (p=0.001) were statistically associated with MRSA colonization, as given in Table 2.

DST testing revealed that of 41 isolated S. aureus strains, only 8 (19.51%) were sensitive to all the antibiotics tested, including penicillin. A total of 3 (7.32%) were multi-drug resistant, while 1(2.43%) was a possible XDR in regard of the antibiotics used. This study has revealed that all Staphylococcus aureus was susceptible to vancomycin 41/41 (100%), than clindamycin 24/41 (58.54%), cefoxitin 20/41 (48.78%), erythromycin 14/41 (34.15%) and penicillin 8/41 (19.51%). The susceptibility pattern for clindamycin indicated that 3/17 (17.65%) were inducible resistances, while 14/17 (82.35%) were constitutively resistant. The resistance to erythromycin was 2/46 (4.35%) among all Staphylococcus aureus isolates. The MRSA isolates were more sensitive to vancomycin with 100% sensitivity, while the rest of the antibiotics were poor to gentamycin, clindamycin, erythromycin and penicillin which all gave 100% resistance to MRSA isolates, as presented in Table 3.

To the best of our knowledge, and search, this is the first report of MRSA colonization among PLWHIV attending Nyenga Hospital in Buikwe district. The prevalence of MRSA reported here was 5.02% (95% confidence interval: 3.67-7.02), comparable to the 5.1% reported in Singapore 22, and slightly higher than 2% that was reported in Spain 23 and 2.4% in northern Ethiopia 24. On the other hand, the prevalence is lower than 15.4% reported among an adult cohort from Johns Hopkins University AIDS Service in Baltimore 25, and 16.8% in Northeast Ethiopia 26. The low prevalence of MRSA colonization in this study is ascribed to the occasional visit of PLWHIV to the health facility, since repeated visits or contact with hands of health workers in HIV infected individuals is the major risk factor for colonization 2425.

Low CD4 cell counts (less than 200 (p=0.000) and less than 500 cells/litre (p=0.003)) and deteriorating WHO clinical stages were significantly associated with MRSA colonization. This finding affirms to results from previous studies 525. Although mechanisms of resistance were unable to be further characterized, it is notable that HIV-infected clients with advanced immune suppression were more likely to carry MRSA. This is consistent with what was reported from other studies 52627.

The assessment of the drug susceptibility pattern of the MRSA isolates indicated high rates of co-resistance of MRSA to commonly prescribed antibiotics such as gentamycin, clindamycin, erythromycin and penicillin which all gave 100% resistance. This is similar to earlier reports 428. The observed high rates of resistance to penicillin, gentamycin, erythromycin, clindamycin, and vancomycin suggest that most of this colonization were caused by resistant strains 2829. The high rates of concomitant drug resistance to the commonly available reserve antibiotics for use among the HIV population is of critical attention as S. aureus is a common pathogen among PLWHIV 26. As all participants were ambulatory, those colonized by MRSA could easily transmit the pathogenic bacteria to the community. Our study findings subject to the following limitations, including that nares are not the only primary body site of colonization, so our reported prevalence could under-detect MRSA colonization in this population. In addition, we were unable to genetically characterize MRSA isolates due to resource constraints.

Our results are reassuring that the overall MRSA colonization is high in our setting. As the majority of the antibiotics in use were resistant, it raises significant concerns of very complicated clinical management. Deteriorating immunological state as measured by low CD4 cell count and advanced clinical stages of infection were significantly associated with MRSA colonization. Premised on these, we have demonstrated the need to encourage routine MRSA screening because of the associated factors.