Abstract
This cross-sectional study investigated the Staphylococcus aureus (S. aureus) and methicillin-resistant S. aureus (MRSA) nasopharyngeal carriage epidemiology in Accra approximately five years post-pneumococcal conjugate vaccines introduction in the country. Archived nasopharyngeal swabs collected from 410 children aged under five years old were bacteriologically cultured. The resultant S. aureus isolates were subjected to antimicrobial susceptibility testing and screening for carriage of the mecA and LukF-PV (pvl) genes, following standard procedures. The data obtained were analyzed with Statistical Products and Services Solutions (SPSS) using descriptive statistics and Chi square tests of associations. The isolated bacteria decreased across coagulase-negative Staphylococci (47.3%, n = 194), S. aureus (23.2%, n = 95), Diphtheroids (5.4%, n = 22), Micrococcus species (3.7%, n = 15), Klebsiella pneumoniae (3.2%, n = 13), Moraxella species and Citrobacter species (1.5% each, n = 6), Escherichia coli, Enterobacter species, and Pseudomonas species (0.9% each, n = 2). The MRSA carriage prevalence was 0.49% (n = 2). Individuals aged 37–48 months recorded the highest proportion of S. aureus carriage (32.6%, 31/95). Resistance of S. aureus to the antibiotics tested were penicillin G (97.9%, n = 93), amoxiclav (20%, n = 19), tetracycline (18.9%, n = 18), erythromycin (5.3%, n = 5), ciprofloxacin (2.1%, n = 2), gentamicin (1.1%, n = 1), cotrimoxazole, clindamycin, linezolid, and teicoplanin (0% each). No inducible clindamycin resistance was observed for the erythromycin-resistant isolates. Three (3.2%) of the isolates were multidrug resistant, of which 66.7% (2/3) were MRSA. The pvl gene was associated with 59.14% (55/93) of the methicillin-sensitive S. aureus (MSSA) isolates, but was not detected among any of the MRSA isolates.
Highlights
The human nasopharynx and oropharynx are anatomical sites colonized by a wide array of microorganisms—from commensals to potential pathogens—and a higher risk of transmission of these organisms occurs among children [1]
A total of 410 specimens collected from children under five years of age, who were recruited in a previous study focused on the epidemiology of S. pneumoniae nasopharyngeal colonization among the study participants [47], were cultured for the isolation of S. aureus
As the S. aureus nasopharyngeal carriage prevalence recorded in the current study is comparable to the nasal carriage prevalence of the organism recorded in a number of studies conducted in the country post-PCV introduction, it could be discerned that the proportion of S. aureus in the nasopharynx seems to be increasing, and this is suggestive that Pneumococcal Conjugate Vaccine-13 (PCV-13) introduction may have played a role, even if infinitesimal
Summary
The human nasopharynx and oropharynx are anatomical sites colonized by a wide array of microorganisms—from commensals to potential pathogens—and a higher risk of transmission of these organisms occurs among children [1]. Staphylococcus aureus, Moraxella catarrhalis, Haemophilus influenzae, and Streptococcus pneumoniae are examples of these organisms and have been reported to occasionally cause local and disseminated infections— such as pneumonia, bacteraemia, endocarditis, osteomyelitis, meningitis, and skin and soft tissue infections—as a sequel to colonization of these and other anatomical sites [2,3] Of these commensals, S. aureus and S. pneumoniae ( called pneumococcus) are the most clinically significant, given their high capacity to cause invasive diseases [4,5,6,7] concurrent with their predisposition to developing multidrug resistance [8,9,10,11,12,13,14]. One of these vaccines, which is currently widely used, is the Pneumococcal Conjugate Vaccine-13 (PCV-13) [17], and its introduction led to a decline in pneumococcal carriage [20]
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