Staphylococcus aureus, the golden cluster seed, is a spherical bacterium frequently found in the nose, throat, intestine, vagina, and skin of human body (1). It is a pathogen of greater concern because of its ability to cause a diverse array of life-threatening infections and its capacity to adapt fast to the different environmental conditions (2,3). These features have made infections of S. aureus increasingly difficult to treat because of the fast rate at which it develops resistance to common antimicrobial agents.
Multiple antibiotic resistance is a major health concern in the treatment of staphylococcal infections, especially infections of methicillin-resistant S. aureus (MRSA) which occurs due to the extensive use of antimicrobial agents, coupled with the transmission of an appreciable proportion of the organism by person-to-person contacts (4). Hence, effective control of antibiotic use and prevention of the transmission of these strains are essential to eradicate this infectious organism.
The gut is an important habitat of parasites and bacteria which can be transmitted through objects contaminated with faeces, indicating the importance of faecal-oral transmission in humans, which can lead to mild or severe diseases in susceptible individuals or when found in sterile sites of the body (5). The presence of staphylococci in stools has been recognized as an important pathogen responsible for antibiotic-associated diarrhoea in humans (6). Reports of recent studies are also implicating the gut as an important reservoir of antibiotic-resistant S. aureus strains (7,8).
Most studies on S. aureus have so far been conducted on samples from the nose and throat but only a very few detailed studies on its colonization of the gut have been reported. Thus, there is a need for more studies on S. aureus from the gut, as an important reservoir of multiple antibiotic-resistant bacterial strains, especially in developing countries where the control of antibiotic use is inadequate. We report here the prevalence of multidrug-resistant faecal S. aureus isolates from healthy inhabitants in Amassoma, Nigeria.
MATERIALS AND METHODS
In total, 120 subjects comprising an equal number of villagers and students of the Niger Delta University, Wilberforce Island, Amassoma, Bayelsa state, Nigeria, were randomly recruited into the study for three months from March 2009. Amassoma is a very small village in Bayelsa state, south-southern Nigeria, where the new growing state university exists. Trading, farming of crops, and fishing are the occupations of the villagers.
Willingness of the subjects to participate in the study was a strong criterion for the study. The volunteers gave informed consents by providing demographic data and a completed questionnaire on the evaluation of their previous use of antibiotics. They were not on any antibiotic for at least two weeks at the time of the sampling nor had been admitted to any hospitals in the last one year before the survey. They were aged 15-35 years.
Sampling and isolation of S. aureus
Sterile cotton swabs were given to the volunteers to deep into their freshly-produced faeces and return into the swab's case. These stool samples were collected from the volunteers within 24 hours and transported within an hour to the laboratory in iced packs, where these were inoculated directly onto prepared sterilized mannitol salt agar (MSA) plates (Oxoid, UK) and streaked before incubated at 37 °C for 24 hours.
Identification of S. aureus
S. aureus was identified and differentiated from related organisms based on the colony morphology on the MSA plates. Two discrete yellow colonies on each of the MSA plates were subcultured on sterile nutrient agar (Oxoid, UK) slants aseptically and incubated at 37 °C for 24 hours. The proliferated organisms were characterized by Gram staining, productions of catalase, DNase, and coagulase (using human plasma). …