Nasopharyngeal Carriage and Antimicrobial Susceptibility Profile of Staphylococcus Aureus among Children Under Five Years in Accra

Abstract

BACKGROUND: Staphylococcus aureus (S. aureus), although found predominantly in the anterior nares of the human population, can also colonise the nasopharynx. There are concerns regarding a potential increase in S. aureus carriage and disease after the introduction of the Pneumococcal Conjugate Vaccines (PCVs) in Africa. Hence, the need for a better understanding of the nasopharyngeal carriage prevalence of S. aureus, antimicrobial resistance profile and possible virulence genes that may assist the organism to be more infectious. AIM: To investigate S. aureus and methicillin resistant S. aureus (MRSA) nasopharyngeal carriage among children under five years in the conjugate vaccine era in Accra. METHOD: This cross-sectional study used 410 archived nasopharyngeal swab samples collected from September to December 2016 from children under five years old from selected schools in the Accra Metropolis. In this current study, S. aureus was isolated and identified using standard bacteriological methods. Further characterisation such as antimicrobial susceptibility testing (AST) according to 2017 Clinical and Laboratory Standard guidelines (CLSI), mecA and LukF-PV (Panton-Valentine Leucocidin (PVL) genes were screened by polymerase chain reaction (PCR). Data on resistance of S. aureus to standard antibiotics were generated and analysed using descriptive statistics. RESULTS: The predominant bacteria isolated were Coagulase Negative Staphylococci representing 47.3% (194/410), followed by S. aureus, 23.2% (95/410); Diphtheriodes, 5.4% (22/410); Micrococcus species, 3.7% (15/410); Klebsiella pneumoniae, 3.2% (13/410); Moraxella species and Citrobacter species had 1.5% (6/410) each; Escherichia coli, Enterobacter species and Pseudomonas species had 0.9% (2/410). The mecA mediated MRSA carriage prevalence was 2.1% (2/95) and it was found in females aged 36 months (3 years) and 52 months (4 years) old. Females recorded a higher carriage prevalence in comparison to males, but this difference was not statistically significant [51.6% (49/95) vs. 48.8% (46/95), p=0.533]. Of all the age groups, individuals in the age range of 37-48 months (3.1-4.0 years) recorded the highest S. aureus carriage prevalence of 32.6% (31/95). Resistance of S. aureus isolates to various antibiotics were as follows: penicillin, 97.9% (93/95); amoxiclav, 20% (19/95); tetracycline, 18.9% (18/95); erythromycin, 5.3% (5/95); ciprofloxacin, 2.1% (2/95) and gentamicin, 1.1% (1/95). None of the isolates were resistant to cotrimoxazole, clindamycin, linezolid, and teicoplanin. No inducible clindamycin resistance was observed with erythromycin resistance strains. Three {3.2% (3/95)} of the isolates were multidrug resistant (MDR), of which 66.7% (2/3) was MRSA and 33.3% (1/3) was Methicillin Susceptible S. aureus (MSSA). Panton-Valentine Leucocidin (LukF-PV) gene was only associated with 58% (55/95) of the MSSA. CONCLUSION: It is concluded that, a considerable proportion of school children under five years sampled from Accra harboured S. aureus in the nasopharynx and a low prevalence of mecA gene mediated MRSA. Proper antibiotic stewardship programmes are critical to limit the clinical impact of MRSA. Penicillin non-susceptibility and resistance to other beta-lactam antimicrobials were observed. Susceptibility to cotrimoxazole, clindamycin, linezolid and teicoplanin were observed coupled with low multidrug resistance among the isolates. High nasopharyngeal carriage prevalence of MSSA harbouring LukF-PV mediated PVL gene may serve as a major risk of contracting severe infection. It is recommended that holistic health intervention targeting MSSA may be required during pneumococcal vaccination campaigns.