Local Epidemiology of Nosocomial Staphylococcus aureus Infection in a Nigerian University Teaching Hospital.

Population-based studies of Staphylococcus aureus contribute to understanding the epidemiology of S. aureus infection. We enrolled surgical inpatients admitted to an African tertiary-care hospital in order to prospectively analyze the nosocomial impact of S. aureus. Data collection included an active sampling of the anterior nares and infectious foci within 48 h after admission and subsequently when clinically indicated. All S. aureus isolates were spa and agr genotyped. Possession of Panton-Valentine leukocidin (PVL) and other toxin genes was determined. We analyzed antibiotic susceptibility profiles by VITEK 2 systems and verified methicillin-resistant S. aureus (MRSA) by mecA/C PCR. Among 325 patients, 15.4% carried methicillin-susceptible S. aureus (MSSA) at admission, while 3.7% carried MRSA. The incidence densities of nosocomial infections due to MSSA and MRSA were 35.4 and 6.2 infections per 10,000 patient-days, respectively. Among all 47 nosocomial infections, skin and soft-tissue (40.4%) and bones or joints' (25.5%) infections predominated. Six (12.7%) infection-related S. aureus isolates harbored PVL genes including two (4.2%) MRSA: overall, seventeen (36.2%) isolates carried pyrogenic toxin superantigens or other toxin genes. This study illustrates the considerable nosocomial impact of S. aureus in a Nigerian University hospital. Furthermore, they indicate a need for effective approaches to curtail nosocomial acquisition of multidrug-resistant S. aureus.

Persistent Staphylococcus aureus nasal colonization in ambulatory human immunodeficiency virus-infected patients in Nigeria: Risk factors and molecular features.

This longitudinal study on Staphylococcus aureus colonization in Nigerian human immunodeficiency virus patients (n = 187) found a trend towards a higher proportion of persistent S. aureus carriage in patients with advanced human immunodeficiency virus infection, low CD4+ cell counts, and a predominance of isolates belonging to ST8/spa-CC064 in persistent carriers.

Characterization of colonizing Staphylococcus aureus isolated from surgical wards' patients in a Nigerian university hospital.

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.

Antibiotic resistance and virulence properties in Escherichia coli strains from cases of urinary tract infections.

This study determined E. coli resistance to commonly used antibiotics together with their virulence properties in Ile-Ife, Nigeria. A total of 137 E. coli isolates from cases of urinary tract infection were tested for their sensitivity to commonly used antibiotics and possession of virulence factors using standard methods. Their ability to transfer resistance was also determined. The isolates demonstrated a high and widespread resistance (51.1 % to 94.3 %) to all the antibiotics used except Nitrofurantoin (7.3 %). A total of 50 (36.5 %) of the isolates were resistant to 10 of the eleven antibiotics employed. Sixty three per cent (63 %) of the 107 trimethoprim resistant E. coli transferred their resistances while amoxicillin, gentamycin, augmentin, tetracycline and erythromycin were cotransferred with trimethoprim. Fifty one (37.2 %) of these multi-resistant isolates possessed one or more virulent factors. The study concluded that urinary tract infection due to E. coli in Ile-Ife may be difficult to treat empirically except with nitrofurantoin, due to high resistance to commonly used antibiotics. It is imperative that culture and susceptibility tests be carried out on infecting pathogen prior to treatment, in order to avoid treatment failure and reduce selective pressure that could result in the spread of uropathogenic E. coli in the environment.

Antibiotic resistance and virulence properties in escherichia coli strains from cases of urinary tract infections

This study determined E. coli resistance to commonly used antibiotics together with their virulence properties in Ile-Ife; Nigeria. A total of 137 E. coli isolates from cases of urinary tract infection were tested for their sensitivity to commonly used antibiotics and possession of virulence factors using standard methods. Their ability to transfer resistance was also determined. The isolates demonstrated a high and widespread resistance (51.1 to 94.3 ) to all the antibiotics used except Nitrofurantoin (7.3 ). A total of 50 (36.5 ) of the isolates were resistant to 10 of the eleven antibiotics employed. Sixty three per cent (63 ) of the 107 trimethoprim resistant E. coli transferred their resistances while amoxicillin; gentamycin; augmentin; tetracycline and erythromycin were co-transferred with trimethoprim. Fifty one (37.2 ) of these multi-resistant isolates possessed one or more virulent factors. The study concluded that urinary tract infection due to E. coli in Ile-Ife may be difficult to treat empirically except with nitrofurantoin; due to high resistance to commonly used antibiotics. It is imperative that culture and susceptibility tests be carried out on infecting pathogen prior to treatment; in order to avoid treatment failure and reduce selective pressure that could result in the spread of uropathogenic E. coli in the environment

Clonal expansion accounts for an excess of antimicrobial resistance in Staphylococcus aureus colonising HIV-positive individuals in Lagos, Nigeria.

Nasal colonisation with Staphylococcus aureus is a risk factor for invasive infection in human immunodeficiency virus (HIV)-positive individuals. This study aimed to characterise colonising S. aureus from regions with a high HIV prevalence. Single nasal swabs were taken from a total of 374 HIV-positive and 370 healthy individuals. Overall, 202 S. aureus carriers were detected. Compared with healthy individuals, HIV-positive subjects were more likely to be S. aureus nasal carriers (33% vs. 21%; P=0.0001). Isolates from HIV-positive individuals were more often resistant to meticillin (16% vs. 8%; P=0.13), chloramphenicol (47% vs. 16%; P<0.0001), sulfamethoxazole/trimethoprim (SXT) (90% vs. 55%; P<0.0001) and ciprofloxacin (18% vs. 0%; P<0.0001). Strains belonging to the spa clonal complexes 3772/ST25 and 064/ST8 were significantly more often isolated from HIV-positive individuals and exhibited greater resistance to ciprofloxacin, SXT and chloramphenicol (spa-CC 3772) or to meticillin (spa-CC 064), respectively. Panton-Valentine leukocidin gene content was high overall and was equally distributed between isolates from HIV-positive and healthy individuals (33% vs. 30%). Genotypic characteristics of colonising isolates were similar to those reported to cause invasive infection in Nigeria. The HIV pandemic contributes to the evolution of antimicrobial resistance in S. aureus. Measures to contain antimicrobial resistance of S. aureus in Nigeria must target risk groups such as HIV-positive individuals.

Identification and molecular characterization of mannitol salt positive, coagulase-negative staphylococci from nasal samples of medical personnel and students.

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.

The discovery of a multi-resistant Staphylococcus haemolyticus clone in the hospital and community environment in south western Nigeria.

Among clinically significant isolates of coagulase negative staphylococci, Staphylococcus haemolyticus is ranked second after Staphylococcus epidermidis. It has been associated with septicemia in newborns and various infections in persons with compromised host defenses and implanted foreign bodies. The existence of a multi-resistant Staphylococcus haemolyticus clone was discovered during a study on patients with skin and soft tissue infections at two local health clinics and in a referral hospital in South Western Nigeria. The clonal nature of these strains was determined by antibiotic susceptibility profile and pulsed field gel electrophoresis. This represents the first report of what appears to be a hospital-acquired and transmitted Staphylococcus haemolyticus clone in South Western Nigeria. Careful infection control measures and strain typing are urgently needed to understand species epidemiology and to limit the spread of multi-resistant strains within and beyond healthcare facilities.

Isolation and molecular characterization of multiresistant Staphylococcus sciuri and Staphylococcus haemolyticus associated with skin and soft-tissue infections.

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.

Wound infections in two health institutions in Ile-Ife, Nigeria: results of a cohort study.

The control of wound infections is increasingly complicated, yet treatment is not always guided by microbiological diagnosis. To describe the distribution of wound infections and causative agents, a prospective, 6-month cohort study involving 102 outpatients was conducted at the University Teaching Hospital and the Health Center in Ile-Ife, Nigeria. Location and type of infected wounds were recorded and bacterial isolates were identified by standard microbiological techniques. Almost half (40%) of all infected wounds were attributed to trauma and, in most cases, located on the extremities. Of the 162 bacterial isolates obtained from wound cultures, 39 were monomicrobial and 55 were polymicrobial; no bacterial isolate was obtained in eight cases. Staphylococcus aureus was the predominant micro-organism (25%), followed by Escherichia coli (12%), Pseudomonas aeruginosa (9%), and Staphylococcus epidermidis (9%). The diversity of micro-organisms and the high incidence of polymicrobic flora in this study give credence to the value of identifying one or more bacterial pathogens from wound cultures. The recognition of causative agents of wound infections can assist wound care practitioners in taking appropriate measures. Continuous dialogue between the microbiology department and wound care practitioners is strongly advised in order to improve treatment outcomes and slow the development of antibiotic-resistant bacteria.