The microbiological analysis of wound infection in 102 patients

In contrast to developed countries, only limited data on the prevalence, resistance and clonal structure of Staphylococcus aureus are available for African countries. Since S. aureus carriage is a risk factor for postoperative wound infection, patients who had been hospitalized in surgical wards in a Nigerian University Teaching Hospital were screened for S. aureus carriage. All S. aureus isolates were genotyped (spa, agr) and assigned to multilocus sequence types (MLST). Species affiliation, methicillin-resistance, and the possession of pyrogenic toxin superantigens (PTSAg), exfoliative toxins (ETs) and Panton-Valentine Leukocidin (PVL) were analyzed. Of 192 patients screened, the S. aureus carrier rate was 31.8 % (n = 61). Of these isolates, 7 (11.5%) were methicillin-resistant (MRSA). The isolates comprised 24 spa types. The most frequent spa types were t064, t084, t311, and t1931, while the most prevalent MLST clonal complexes were CC5 and CC15. The most frequent PTSAg genes detected were seg/sei (41.0%) followed by seb (29.5%), sea (19.7%), seh (14.7%) and sec (11.5). The difference between the possession of classical and newly described PTSAg genes was not significant (63.9% versus 59.0% respectively; P = 0.602). PVL encoding genes were found in 39.3% isolates. All MRSA isolates were PVL negative, SCCmec types I and VI in MLST CC 5 and CC 30, respectively. Typing of the accessory gene regulator (agr) showed the following distribution: agr group 1 (n = 20), group II (n = 17), group III (n = 14) and group IV (n = 10). Compared to European data, enterotoxin gene seb and PVL-encoding genes were more prevalent in Nigerian methicillin-susceptible S. aureus isolates, which may therefore act as potential reservoir for PVL and PTSAg genes.

The isolation, molecular identification and genotyping of multiresistant Staphylococcus sciuri and Staphylococcus haemolyticus from skin and soft-tissue infections are reported. Accurate and full identification of three coagulase-negative staphylococcal isolates was achieved using PCR, while the API STAPH method failed to identify an isolate of S. haemolyticus fully. The PCR assay, which detects polymorphism in the 16S-23S rRNA spacer region, is shown to be potentially useful for rapid and accurate identification of coagulase-negative staphylococci. Identical PFGE type and antibiotic-resistance profiles of two methicillin-resistant S. haemolyticus isolates in this study suggest the existence of a multiresistant community clone. INTRODUCTIONSkin and soft-tissue infections (SSTIs) are among the most common infectious diseases and are a frequent cause of visits to health-care providers. They cover a wide clinical spectrum, from superficial, localized and sometimes self-limited, to deep, rapidly spreading and potentially life-threatening. These infections may be due to a variety of infectious agents including viruses, mycobacteria, other bacteria or fungi. Early diagnosis and treatment of infections caused by bacteria remain a major clinical challenge (Alam et al., 2002). Most bacteria have multiple routes of resistance to any drug and, once resistant, can rapidly produce vast numbers of resistant progeny (Livermore, 2003). The widespread antibiotic resistance in bacteria found in SSTIs compounds treatment management by health-care practitioners, for example, resulting in prolonged hospital stay, increased trauma care and treatment costs (Bowler et al., 2001).Among the members of the genus Staphylococcus that are widely distributed in nature, some species are important human pathogens in SSTIs, causing substantial rates of morbidity and mortality (Engemann et al., 2003;Isaacs, 2003). Staphylococcus aureus, a coagulase-positive staphylococcal species, is the main aetiological agent and most frequently isolated micro-organism in various SSTIs (Bowler et al., 2001; Charalambous et al., 2003). Coagulase-negative staphylococci (CNS) have long been regarded as harmless skin commensals and dismissed as culture contaminants. However, the incidence of CNS reported as causative agents of nosocomial infections has risen substantially with the increasing use of prosthetic devices and other invasive technologies (Peters, 1988;Huebner & Goldmann, 1999;Petinaki et al., 2001). Although Staphylococcus epidermidis accounts for the majority of CNS infections, other species have also been identified in association with human infections (Buttery et al., 1997;Sandoe et al., 1999;Wallet et al., 2000). In addition, cases of multi-drug-resistant CNS species in human infection have been reported (Petinaki et al., 2001;Stepanovic et al., 2002; Basaglia et al., 2003). Limited treatment options and prolonged course of infection due to these CNS species could have severe consequences for patients. Full and accurate identification of CNS isolates...

The identification of mannitol salt positive, coagulase-negative staphylococci (CNS) is often disregarded when Staphylococcus aureus is screened in clinical samples using mannitol salt agar. However, the emergence of CNS as important human pathogens has indicated that reliable methods for the identification of clinically significant CNS are of great importance in understanding the epidemiology of infections caused by them. The identification and molecular characterization of mannitol salt positive CNS from nasal samples of medical personnel and students is reported here. A total of 84 mannitol salt positive staphylococcal isolates were obtained from 240 nasal samples, of which 15 were CNS. The API STAPH system classified the CNS isolates into six species, and one-third of the isolates were identified with confidence levels of <80 %. 16S-23S rRNA intergenic spacer length polymorphism analysis (ITS-PCR) identified only two species (Staphylococcus haemolyticus and Staphylococcus saprophyticus). This identification was confirmed by antibiotyping, species-specific PCR and PFGE. The results from this study indicate that ITS-PCR is a potentially useful and reliable tool, enabling hospital laboratories to obtain rapid, full and accurate identification of CNS at the species level. INTRODUCTIONThe identification of bacterial pathogens in human infection plays a key role in the management of patients in health care institutions. In many clinical laboratories, Staphylococcus aureus is usually isolated on nonspecific media (e.g. blood agar) and then presumptively identified before definitive overnight characterization (Kloos & Bannerman, 1995). In an attempt to achieve presumptive isolation in a single step, mannitol salt agar (MSA) was developed in 1945 for the selective isolation of pathogenic staphylococci in the clinical microbiology laboratory (Chapman, 1945;Blair et al., 1967). The growth and production of yellow colonies, due to the high salt content of the medium and fermentation of mannitol, is regarded as a presumptive tool in the identification of S. aureus. It is also described as a characteristic for the differentiation of coagulase-positive staphylococci from coagulase-negative staphylococci (CNS) (Duguid, 1989). However, there are reports that some CNS can also produce yellow colonies on MSA (Martinez et al., 1992;Merlino et al., 1996;Mir et al., 1998;Jayaratne & Rutherford, 1999;Simor et al., 2001;Zadik et al., 2001). Mannitol salt positive CNS impede and delay the isolation and subsequent identification of S. aureus in clinical samples on the primary plate. Nevertheless, they have attracted very little attention and in most cases are not identified to species level.As a group, the CNS are among the most frequently isolated bacteria in the clinical microbiology laboratory. They are becoming increasingly important as causative agents of hospital-acquired bacteraemia, with the increasing use of prosthetic devices and other invasive technologies in medical institutions (von Eiff et al., 2002 The aim of this stud...