The mechanisms involved in the pathogenesis of osteonecrosis of the femoral head in sickle cell disease are not fully known. The aim of this study was to identify risk factors for osteonecrosis of the femoral head among sickle cell disease patients. Clinical (frequency of painful crises and hospitalisation) and laboratory parameters (euglobulin clot lysis time, haematocrit, platelet count, and leucocyte count) of 25 consecutive patients with avascular necrosis of the femoral head from sickle cell disease were compared with those of 26 age-and sex-matched sickle cell disease patients without avascular necrosis. The group with avascular necrosis of the femoral head (mean age 23.7± 4.9 years) had a significantly higher rate of painful crises (p=0.03) and hospitalisations per year (p=0.002) than the group without avascular necrosis (mean age 21.6± 5.2 years). The group with avascular necrosis also had a significantly higher euglobulin clot lysis time than the group without avascular necrosis (p=0.001). In conclusion, it appears that not all patients with sickle cell disease have impaired fibrinolytic activity. The aetiology of avascular necrosis in sickle cell disease is multifactorial.Résumé Les mécanismes de la nécrose de la tête fémorale dans la drépanocytose sont encore relativement obscures. Le but de cette étude est de mettre en évidence les facteurs de risque de la tête fémorale chez les patients présentant une drépanocytose. Matériel et méthode : l'évaluation des paramètres cliniques (fréquence des crises, nombre d'hospitalisations) et biologique (lyse du caillot, euglobuline, hématrocrite, plaquettes et numération leucocytaire) de 25 patients consécutifs présentant une nécrose avasculaire de la tête fémorale dans le cadre d'une drépanocytose ont été comparés aux données d'une série de patients âgés en moyenne de 26 ans et présentant une drépanocytose sans nécrose aseptique. Résultats : le groupe des nécroses aseptiques de tête fémorale était âgé en moyenne de 23,7± 4,9 avec un nombre de crises douloureuses significativement plus élevé (p=0,03) et un nombre d'hospitalisation également plus élevé (p=0,002) que dans le groupe des nécroses avasculaires simples, moyenne d'âge 21,6±5,2 ans. Le groupe présentant une nécrose avasculaire présent-ant également un taux de lyse du caillot et d'euglobuline plus élevé que dans le groupe sans nécrose (p=0,001). Conclusion : il semble que les patients porteurs d'une drépanocytose comportent sur le plan biologique une activité fribrinolytique plus importante. L'étiologie de la nécrose avasculaire dans le cadre de la drépanocytose est multifactorielle.

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.

IBC appears to predict more reliably the complete etiologic organisms than STCs in chronic osteomyelitis.

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