Introduction

Staphylococcus aureus which is fast becoming a household name in Nigeria among orthodox and traditional practitioners came into lime-light shortly after the discovery of HIV infections in 1981 as a co-infectious agent among HIV infected individuals. Its spread has been aided by the ability to survive relatively harsh environmental conditions, the use and misuse of antibiotics, some cultural and human behaviors and non-compliance with simple control measure of regular hand washing by hospital staff (Winn et al., 2006; Mayhall, 2004). Anterior nares were identified to be the most consistent site of Staphylococcal colonization.  Staphylococcus aureus colonization of the anterior nares has also been regarded as a high risk for subsequent infection including that of MRSA (Kluytmans et al., 1997; Williams, 1946) Colonization is a very important step by MRSA before infection can occur. This occur in 20% of the human population where the colonization is said to be facilitated by clumping factor B - ClFB (Nasia and Elisa, 2008) The colonization of different parts of the body by Staphylococcus aureus has been incriminated in many disease conditions and has become a major problem in the control of both community and hospital associated infections (Smith et al., 2009) Few strains are resistant to all clinically useful antibiotics. The emergence of multidrug resistant strains of Staphylococcus aureus made continuous update on antimicrobial susceptibility profile an important process. Methicillin Resistant Staphylococcus aureus (MRSA) has been reported to be major cause of various infections throughout the world. MRSA prevalence varies from region to region, it was reported to be 25% in western part of India in 2010, 54.2% in Saudi Arabia, 69.8% in the United States and between 22-54% in Nigeria in 2006 (Khadri and Alzohairy, 2010; Kuchnert et al., 2006) They are ubiquitous and the cause of many community, endemic and epidemic nosocomial colonization and infections (CDC, 2004)  Staphylococci aureus can easily spread from man to man or can be picked up from inanimate objects like table tops, door handles, beddings, toilet seats and exchange of cell phones. These are common items often used by students who interact freely with each other. A healthy carrier can therefore serve as a pool for regular and consistent release of the organism to the community. This study was therefore carried out to investigate the level of colonization of nasal region by MRSA among healthy undergraduate students of Adekunle Ajasin University (AAU), Akungba-Akoko, Nigeria and identified carriers will be referred to the University’s Health Centre for follow up.

Materials and Methods

Study Design and area

A cross sectional study was conducted among students of the six Faculties of AAU between May and October of 2015 after an ethical approval was given by the University. The University has about 8,000 students in her regular and Part- Time programmers.

Data and Sample collection

Questionnaire was admitted on each volunteer to get their biodata and determined their suitability for the study. Thirty-two volunteers did not meet the inclusion criteria and were thus excluded from the study. Three hundred and fifty (350) apparently healthy students spread across the six Faculties of the University were recruited into the study.  Sterile swab sticks were inserted to the two nostrils and rotated gently, withdrawn and cultured immediately to prevent drying off of the samples so collected. The samples were cultured on Manitol Salt Agar, Blood agar and MacConkey agar. The identification of the isolates was according to known standard methods (Bergey, 1984) Catalase and coagulase tests were done on all Gram positive cocci colonies to determine pathogenic Staphylococcus. Confirmed S. aureus isolates were screened for methicillin resistance using Cefoxin disc (1µg). Susceptibility test of all isolates to commonly used antibiotics was done on Meuller-Hinton agar using disc diffusion method approved by NCCLS. The results were read and interpreted as sensitive or resistant according to NCCLS standard (NCCLS, 2003)

Results

The volunteers were made up of 142 males and 198 females with mean age of 19.5 ± 2.1. Ninety-eight samples (28%) were positive for S. aureus out of which 9(2.6%) were screened positive for MRSA (Table 1). Other organisms isolated were Klebsiella sp, Psuedomonas sp and Coagulase –ve Staphylococci. The frequency of isolation of MRSA was higher (1.7%) among the female volunteers. S. aureus isolates were susceptible to Erythromycin (86.5%), Augmentin (80.9%) and Gentamycin (80.9%) and highly resistant to Tetracycline (89%) (Table 2). Similar pattern of susceptibility was recorded for MRSA with 100% susceptibility to Augmentin. High activities were recorded by Ciprofloxacin and Augmentin against all other isolates (Table 3).

Table 1 Demographic characteristic in relation to the prevalence of Staphylococcus aureus and MRSA among volunteers

Table 2 Antibiogram of Staphylococcus aureus and MRSA isolates from the nasal region of volunteers

Table 3 Antibiogram of other organisms isolated from the nasal region of volunteers

Discussion

This community based study was conducted to give additional information that could possibly assist in combating the spread of MRSA. The almost equal sex population ratio of 1:1 gives the study credibility and unbiased gender assessment. In this study, a prevalence of 25.4% was recorded for S. aureus which is lower than 32.4% and 69.8% reported by Kuehnert et al., (2006) and Khadri and Alzohairy (2010) respectively. Apart from Tetracycline and Ampicillin, the susceptibility of S. aureus isolates from this study was encouraging. High resistant to Penicillin (76.4%) was reported in this study which was higher than 43.96% reported by Malapati et al., (2015) and lower to 100% reported by Tekalign and Keteman (2013), Pandey et al., (2012), Saravana (2013) and Jayatilleke and Bandara (2012). This wide variation might be due to strain differences which were not considered in this study, use and misuse of Tetracycline among the studied population or the presence of inherent or acquired resistant gene. Staphylococcus aureus susceptibility to Ciprofloxacin (91.0%) in this study which is similar to 87.5% reported by Saravanan et al., (2013)  from domestic animal, is very encouraging and may be credited to the fact that the isolates are community acquired because studies with hospital acquired strains reported very low susceptibility of 33% (Koksal et al., 2009) , 40% (Khadri and Alzohairy, 2010) and 43% (Malapati et al., 2015) The susceptibility of S. aureus in the current study to Erythromycin (86.5%) was similar to 76.2% reported by Malapati et al., (2015) and 70.0% by Abdul et al., (2011) however, the results are at variance with 95.6%, 98.3% and 90% resistance reported by Narasinga and Prabhakar (2011), Syed et al., (2011) and Kandle et al., (2003) respectively. This changing pattern of S. aureus to various antibiotics at various locations remains the major problem in combating its spread. It further stresses the importance of antibiotic sensitivity test before initiation of antibiotic in treatment of Staphylococcal infections. A prevalence of 2.6% for MRSA was recorded from this study. This appear very low when compared with 54.2% reported by Khadri and Alzohairy (2010) 32.4% reported by Kuehnert et al., (2006) 32.2% reported by Bilal and Srikanth (2013). In India, prevalence of MRSA ranged between 38 and 52% (Sangeeta et al., 2013) However, it should be noted that all these other studies were hospital based and possibly among symptomatic patients. This again support the idea of having more investigation centered on the hospital environment (among animate and inanimate objects), however, the community should not be neglected which might be serving as a reservoir for continuous infection. As expected, Methicillin Sensitive Staphylococcal aureus (MSSA) were more susceptible to antimicrobial agents tested than MRSA. High resistance was shown by MRSA to Penicillin, Ampicillin, Tetracycline and Cotrimoxazole. This is in agreement with some studies earlier conducted (Bilal and Srikanth, 2013; Vidya et al., 2010 and Arora et al., 2010). Low resistance to quinolones (Ciprofloxacin, 22.3%) in this study was contrary to the works of Bilal and Srikanth (2013) and Saikia (2009) The observation from this study was not expected because, Ciprofloxacin is one of the commonly empirically abused antibiotic with many bacteria now becoming resistant to. In this study all MRSA were susceptible to Augmentin, this give added hope for treating community acquired MRSA if the need arises. Other organism isolated along with S. aureus (Klebsiella sp, Pseudomonas aeruginosa, E. coli and CoNS) were all susceptible to Ciprofloxacin and Augmentin. These agree with the study of Nkang et al., (2009), Resih et al., (1993) and Schumacher-Perdreau (1991). Though, colonizing healthy individuals, the varied susceptibility pattern of these other organisms call for caution in any measure aimed at either reducing MRSA or eradicating it so that, changing in role from non-pathogenic status to a pathogenic one. Resistant to Chloramphenicol was higher in Klebsiella sp and Pseudomonas sp but lower among E. coli and CoNS isolates (Nkang et al., 2009). Though, the susceptibility of these isolates were poor to Ampicillin and Cotrimoxazole, it was similar to 27% and 30% reported by Alos et al. (1993) and Otoe et al., (2002) but at variance with a 100% resistance reported for these two antibiotics in the work of Okonko et al., (2009). Human anxiety about the increase in resistance has become the driving force behind continuous search for novel antimicrobial agent to combat infectious diseases. Rapid identification of nasal carriers of MRSA may indicate those at the highest risk for the development of disease, thus allowing target implementation of currently available and future interventions, including decolonization and vaccination.

Conclusion

A prevalence rate of 2.6% MRSA observed in this study was high enough to generate concern, since they were all healthy carriers. Personal hygiene is therefore advocated among this studied group to curb its spread. For a successful empirical therapy, a regular surveillance to show the current antibiogram of both CA and HA isolates is important, since the evolving of resistant strains has become obvious from various studies.

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