Factors Associated with Pathogenicity and Antibiotic Resistance of Local Strains of Lancefield Groups A, C and G Streptococci

Author: Lawal, Sule Folayan

Supervisor: Tolu Odugbemi

Four thousand, three hundred and ninety five throat, 4,395 nasal and 58 skin lesion swabspecimens were examined bacteriologically out of which 401 (9.12%) were positive for betahaemolytic streptococci (BHS) and 11 (0.25%) for non-haemolytic streptococci (NHS). On the basis of Lancefield group polysaccharide antigens, the isolates were classified into groups A, C, D, G and non-groupable BHS strains. On the basis of bacitracin sensitivity and biochemical analysis, these groups and ungroupable HBS strains were classified into Strept pyogenes Strept. equisimilis, Strept. canis and Strept. milleri. Six members of group A, 68 of group C and 117 of group G BHS isolates were O (SLO), deoxyribonuclease B (DNase B), hyaluronidase, M-associated protein (MAP), serum opacity factor (SOF), proteinase, M,T and R protein antigens. These antigenic components were observed in varying percentages of the isolates: all (100.0%) the six members of group A were positive for SLO and MAP, five (83.3%) for DNase B and hyaluronidase, three (50.0%) for SOF and four (66.6%) for proteinase activity; 41 (60.29%) of group C for SLO and MAP, 52 (76.47%) for DNase B, 56 (82.35%) for hyaluronidase, and nil (0.0%) for both SOF and proteinase while 68 (58.11%) of group G produced SLO, 94 (80.34%) DNase B 56 (47.86%) hyaluronidase, 104 (88.88%) MAP and nil (0.0%) for SOF and proteinase. The ultimately established group C serotype CI and group G serotypes GI - VIII examined for both indigenous and group A - cross - reacting T4 or T25 - antigen showed evidence of these antigens as follows: both serotypes CI and GI showed their indigenous T-antigen and group A cross-reacting T25 and T4 respectively, while serotypes GII - VIII showed indigenous Tantigens only. Varying proportions of those BHS strains (8: 68 for group C and 68: 117 for group G) that produced high ( > 1:80) titres of MAP were studied further. Six members of group C and 19 of group G were ultimately selected as vaccine strains for antisera production in rabbit. Five of the six members of group C and 17 out of 19 of group G successfully produced corresponding type antibodies. Distinct type antisera, one for group C and eight for group Gcorresponding respectively to group C (serotype CI) and group G (serotypes GI - VIII) eventually emerged after absorption with appropriate group C or group G heterologous strains. Other type antisera and their corresponding typeable vaccine strains turned out to be homologous to other group C or group G types. These group C and group G antisera were initially used in parallel with group A type 12 (G 12) and group G strain 51/755 antisera (controls) to screen Lancefield's extracts of 86 group C isolates and 152 group G isolates respectively for evidence of M or R like type antigen. Twelve (13.65%) of the 86 group C and 75 (50.33) of 149 group G isolates could be M-serotyped while none (0.0) showed evidence of R-like antigen/antibody activity. The remaining 76 (86.36%) group C and 74 (49.66%) group G isolates could not be serotyped with the available antisera. Twenty (Co5T'S'). The three patterns occurred in varying percentages of 63.48 (353/556), 33.27 (185/556) and 3.25 (18/556) respectively. Representative strains of the three antibiotic susceptibility patterns, Co5 S' T', Co5 S' T5, and Co' S' T' were observed further to show varying (80 - 0.62 ug/ml) rages of minimum inhibitory concentrations (MIC) of chloramphenicol co-trimoxazole, erythromycin, penicillin G, streptomycin and tetracycline for the three antibiotic - susceptibility patterns, which in the case of chloraphenicol, co-trimoxazole, erythromycin and penicillin G correlated with in vitro susceptibility and in the case of streptomycin and tetracycline correlated with in vitro resistance of the BHS isolates tested against the six antibiotics. The three representative patterns were further screened for evidence of antibiotic - resistance factors, plasmid deoxyribonucleic acid and beta-lactamase for which none of the isolates was positive.