Nasopharyngeal carriage, spa types and drug susceptibility profiles of Staphylococcus aureus from healthy children under 5 years in eastern Uganda

Abstract

Background Staphylococcus aureus carriage is a known risk factor for staphylococcal disease. However, the carriage rates vary by country, demographic group, etc. This study aimed to determine the S. aureus carriage rate in Ugandan children, and track Staphylococcus strains that can cause infection in Uganda. Methods Nasopharyngeal samples (one per child) from 742 healthy children under 5 years living in Iganga/Mayuge Health & Demographic Surveillance Site in eastern Uganda were processed for isolation of S. aureus. Genotyping was performed by spa typing and pulse field gel electrophoresis. Results The processed samples yielded 144 S. aureus isolates (one per sample/child) therefore, the S. aureus carriage rate in the children was 19.4% (144/742). Further, 45 (31.3%, 45/144) of the isolates were methicillin resistant (MRSA) yielding a carriage rate of 6.1% (45/742). All MRSA isolates were susceptible to vancomycin, linezolid and clindamycin however, compared to methicillin susceptible S. aureus (MSSA) isolates (68.8%, 99/144), MRSA were more resistant to non-beta-lactam antimicrobials –tetracycline (91.1%, 41/45), trimethoprim/sulfamethoxazole (73.3%, 33/45), erythromycin (75.6%, 34/99), chloramphenicol (60%, 19/99), gentamicin (55.6%, 25/45) and ciprofloxacin (35.6%, 16/45). Furthermore, an MRSA isolate was mupirocin resistant and 42 (93.3%, 42/45) were multidrug resistant (MDR); three (3%, 3/99) MSSA isolates were mupirocin and clindamycin resistant while 61 (61.6%, 61/99) were MDR. All MSSA/MRSA isolates were susceptible to rifampicin, vancomycin and linezolid but only two were pan-susceptible to the tested antibiotics. Seven spa types were detected in MRSA, of which t064 & t037 were predominant and associated with SCCmec types I & IV, respectively. Fourteen spa types were detected in MSSA, of which t645 & t4353 were predominant. Conclusions S. aureus (MSSA/MRSA) carriage rate in children in rural eastern Uganda is high and comparable to rates for hospitalized patients in Kampala city. Detection of mupirocin resistance is worrying as it could rapidly increase in a low-income setting should mupirocin be used for staphylococcal decolonization. Further, S. aureus strains of spa types t064, t037, t645 & t4353 are prevalent and could be responsible for majority of staphylococcal infections in Uganda.