INTRODUCTION                                  

Staphylococcus aureus is a common pathogenic commensal bacterium found in warm, moist areas of the body particularly the nose, axillae, skin and perineum. The name Staphylococcus is derived from the Greek word “staphyle” which means “bunch of grapes and” “kokkos” which means “granule”. They appear as round (cocci) and firm grape-like structures under the microscope (Ryan and Ray,. 2004). Staphylococcus aureus is a Gram-positive spherical bacterium approximately 1μm in diameter. Its cells form grape-like clusters, since cell division takes place in more than one plane. It is often found as a commensal associated with skin, skin glands and mucous membranes, particularly in the nose of healthy individuals (Crossley and Archer, 1997). It has been estimated that on a rich medium, S. aureus forms medium size “golden”colonies. On sheep blood agar plates, colonies of S. aureus often cause β-hemolysis (Ryan and Ray,2004). The golden pigmentation of S. aureus colonies is caused by the presence of carotenoids and has been reported to be a virulence factor protecting the pathogen against oxidants produced by the immune system (Liu et al., 2005). Staphylococcus are facultative anaerobes capable of generating energy by aerobic respiration and by fermentation which yields mainly lactic acid. Staphylococcus sp. is catalase-positive, a feature differentiating them from Streptococcus sp., and they are oxidase-negative and require complex nutrients,e.g., many amino acids and vitamins B, for growth.

S. aureus is a gram positive organism responsible for causing skin infections and sometimes produces relatively minor skin infections such as pimples and boils. Most individuals are colonized by this bacterium, that is, the bacterium is present but is not causing disease (Wilson, 2001). Staphylococcus aureus is one of the main agents of nosocomial infections and is sometimes difficult to treat with currently available active antimicrobials (Makoni, 2002).

Staphylococcus aureus has been recognized as an epidemiologically important pathogen. Its pathogenic effect is characterized by its ability to haemolyze blood, coagulate plasma and produce a variety of extracellular enzymes and toxins. . S. aureus is present in the nasal passage, throat, hair and skin of healthy individuals (Makoni, 2002).

Staphylococcus aureus, is commonly found on the skin or in the nose of healthy people approximately 25% to 30% of the population are colonized with staph bacteria (i.e., carry the bacteria without becoming ill).

 Sometimes Staphylococcus causes a minor skin infection (pimple, pustule, or boil) that can be treated conservatively, without antibiotics. However, on occasion, Staphyloccus bacteria can cause more serious illnesses, such as infections involving soft tissue, bone, the bloodstream or the lungs.

Over the past years, treatment of some Staphylococcus infections has become more difficult because the bacteria have become resistant to various antibiotics. S. aureus that is resistant to methicillin/Oxacillin is called methicillin-resistant Staphylococcal aureus (MRSA). Staphylococcus aureus is considered to be one of the most important resistant pathogen and it was one of the earliest microorganisms in which penicil­lin resistance was detected. Methicillin-resistant S. aureus became a major threat. Methicillin was introduced in 1959 to treat infections but in 1961 shortly after the introduction of methicillin, Staphylococcus aureus isolates which had acquired resistant to methicillin was reported. Methicillin resistant Staphylococcus aureus (MRSA) is one of the greatly feared strains of S. aureus. Its resistance to most antibiotics makes its treatment to last longer and may include second- and third-tier drugs that are generally more expensive and have greater side effects. MRSA is also known to be relatively quick to mutate. According to Neihart et al., (1988), S. aureus strains carry a wide variety of multidrug resistant genes on plasmid which can be exchanged and spread among different species of Staphylococci.

MRSA is a major cause of community and hospital acquired infection causing several morbidity and mortality worldwide (Grundman et al., 2006; Vindel et al., 2009).

Recently, there has been a shift from it being a nosocomial pathogen as it is now increasingly recovered from nursing homes, prisons, school environments and communities. This shift might be associated with its mode of transmission which is primarily by direct/indirect person to person contact and also by person to surface contact (Fogg, 2002; Evans and Richard, 2009). Outbreaks of community-associated (CA)–MRSA infections have been reported in correctional facilities, among athletic teams, among military recruits, in newborn nurseries, and among men who have sex with men (Chambers, 2001, Ellis et al., 2004)

The emergence of MRSA renders the treatment more challenging (Choi et al., 2006) because they exhibit multiple drug resistance to unrelated antimicrobial agents (Truckssis et al., 1991).There is evidence that hospital acquired methicillin resistant Staphylococcus aureus (HA-MRSA) infection increases morbidity, mortality risks and costs (Cosgrove et al., 2005). MRSA was associated with hospitals; however, it is now increasingly recovered from homes, schools, offices, prisons and community.

Hospital acquired MRSA (HA - MRSA) and community acquired MRSA (CA - MRSA) are the two major groups causing MRSA infections.  MRSA has become a major cause of hospital acquired infection as CA – MRSA emerged worldwide in 1990’s (Vandenesch et al., 2003).  The spectrum of diseases caused by CA –MRSA in the community is high.  Skin and soft tissue infections are the most frequent reported clinical manifestations (Fridkin, 2005; Bagget, 2003). 

Outbreaks of community-associated (CA)–MRSA infections have been reported in correctional facilities, among athletic teams, among military recruits, in newborn nurseries, and among men who have sex with men (Chambers, 2001, Ellis et al., 2004).

CA-MRSA infections now appear to be endemic in many urban regions and cause most CA–S. aureus infections (Eady and Cove, 2003; Moran et al., 2005). Denis et al., (2004) reported that since 1995, MRSA isolates in Belgian hospitals were losing resistance to older antimicrobial drugs such as gentamicin and clindamycin. Some MRSA strains associated with CA infection have been noted to cause Hospital Acquired (HA) infections (Saiman et al., 2003). Another recent report demonstrated that CA strains had emerged as a substantial cause of HA bloodstream infections (Seybold et al., 2006). The emergence of CA-MRSA is of great concern to health officials but of greater concern is the fact that strains frequently associated with community outbreaks are now reported to be causing Hospital acquired infections. (Denis et al., 2004). This in turn renders treatment of Staphylococcal infections more challenging, considering the fact that MRSA are multidrug resistance

Hospital acquired MRSA regularly occurs and shows little variations in its incidence. Most colonized hospital patients; staff and professionals are transient carriers but may become persistent carriers especially when they have skin lesions. Thus the identification and treatment of colonized health professionals and patient can reduce the incidence of hospital acquired MRSA, as unidentified colonized patient can act as reservoir in endemic situations (Ben-David  et al., 2008).

The need to follow the trend of this infection in my own community especially amongst the post graduate students necessitated this work which is aimed at determining the prevalence of MRSA amongst the post student community of Michael Okpara University of Agriculture, Umudike, Nigeria.