MRC Unit The Gambia’s (MRCG) recent study Incidence of macrolide-lincosamide-streptogramin B resistance amongst beta-haemolytic streptococci in The Gambia shows that Beta-haemolytic streptococci, predominantly Group A streptococci (GAS) are associated with a wide range of infections in The Gambia.
Penicillin is the recommended first line of treatment for streptococcal infections particularly that of GAS and Group B streptococci (GBS); however macrolides and sometimes lincosamides are recommended as second line options for patients who are allergic to penicillin. Similar to other Gram-positive organisms, macrolide and lincosamide resistance have been reported to be emerging amongst beta-haemolytic streptococcal isolates globally; including reports from Southern Africa. This highlights the need to probe resistance patterns to these antibiotic groups.
In West Africa, penicillin, macrolide and lincosamide resistance among beta-haemolytic streptococci (BHS) isolates has rarely been described. However, such data are critical to detect and track the emergence of antibiotic resistance.
Funded by MRCG, Beta-haemolytic streptococci were cultured from clinical specimens from patients attending the clinic at MRCG (n = 217) and kept at -70 °C. Of these, 186 were revived and tested for penicillin susceptibility by disc diffusion, E-test methods and the D-test for determination of constitutive and inducible macrolide-lincosamide (MLSB) resistance phenotypes.
The results show majority of BHS isolates from infections were GAS. Of these, 16% were from invasive disease. Other BHS isolated included lancefield groups B (10.2%); C (4.8%), D (, 1.6%), F (2.7%), G (8.6%) and non-typeable (4.3%).
Prevalence of BHS isolated from blood cultures ranged from 0% (2005) to 0.5% (2010). 85 of the isolates were from wound infections. Of the 186 BHS isolates, none was resistant to penicillin and 14 6.1% were resistant to erythromycin. Of these, 4.3% demonstrated constitutive MLSB resistance, and 2.7% were inducible MLSB resistant. All the inducible MLSB isolates were GAS, and majority of the constitutive MLSB isolates (6/8, 75.0%) were non-GAS.
These results were reassuring that macrolide and lincosamide resistance is relatively low. However, monitoring of MLSB resistance is necessary with the global spread of resistant BHS strains.
When asked to comment on the results, Ebenezer Foster-Nyarko 1st author said “Our findings suggest that BHS antibiotic resistance, particularly due to non-GAS, non-GBS may be under-reported in West Africa.”
We are grateful to all clinical and laboratory staffs at the MRCG Clinic in Fajara who supported this study. We also thank Amara Jah, Maimuna Jarju, Sainabou Bojang, Damilola Oluwalana and Dominic Addai of the Molecular Microbiology team of MRCG, for their assistance in the microbiological analysis of the isolates.
Read more about the study on Pubmed website.