Beta-haemolytic streptococci : group specificity in relation to clinical manifestations of infection and antimicrobial susceptibility of the various streptococcal groups at the University Teaching Hospital, Lusaka

Abstract

A total of 239 isolates of beta-haemolytic streptococci were grouped serologically using the "Streptex" rapid latex test kit (Wellcome Reagents Limited, England).The age, sex, type of the clinical specimen, and clinical diagnosis of the patients from whom the isolates were obtained were recorded, and the serologic groups of the beta-haemolytic streptococci in relation to clinical manifestations of infec¬tion determined.The antimicrobial susceptibility pattern of the isolates was determined using the comparative method of disc diffusion. On serological grouping of 239 isolates of beta-haemolytic streptococci, all isolates were found to belong to one of groups A, B, C, D, F and G.The highest number 152 (64%) were group A streptococci. Clinical manifestations of infec¬tion due to group A streptococci included upper respiratory tract infections, pyoderma, osteomyelitis, infected wounds and abscesses.Thirty two of the isolates (13%) were group B streptococci. Clinical manifestations of infections due to group B streptococci were genito-urinary tract infections (mainly in females),and neonatal meningitis.Group B strep¬tococci were also present as part of the normal flora of the genito-urinary tract in females.Groups C (14), D (17) and F (12) were found to cause infections of the genito-urinary tract and also formed part of the normal flora of the genito¬urinary tract.Groups C, F and G were isolated from cases of upper respiratory tract infections. Groups D and G also contributed to infections of wounds.On comparing the results of this study with those of studies in Britain and the United States, the percentage of streptococcal groups isolated from the various clinical sources and clinical conditions were similar except that in the U.T.H., there was a higher percentage of group A streptococci in infected wounds and group B streptococci were absent in the upper respiratory tract and in infected wounds. A study of the antimicrobial susceptibility pattern of 217 beta-haemolytic streptococcal isolates, showed that streptococci of groups A, B, C, F and G were 100% sensitive to penicillin, whereas 25% of group D enterococci were resistant to penicillin but consistently sensitive to ampicillin. All streptococcal groups A, B, C, D, F and G showed high resistance to co-trimoxazole and tetracyclines. Group A showed 51% resistance to tetracyclines while groups B, C, D, F and G showed 90-93% resistance to tetracyclines. Groups F and G showed 30-50% resistance to co-trimoxazole while groups A, B, C and D showed 73-87% resistance to co-trimoxazole.