Antibiogram of staphylococcal strains isolated from milk and milk-products.

A study of the resistance patterns of 248 staphylococcal isolates from milk and milk products to eight antimicrobial agents using the disc method showed that 80 (32.3%) were resistant to sulphafurazole, 75 (30.2%) to penicillin G, 63 (25.4%) to ampicillin, 23 (9.3%) to cloxacillin, 19 (7.7%) to tetracycline, 17 (6.9%) to streptomycin, 14 (5.6%) to erythromycin and 12 (4.8%) to chloramphenicol. One hundred and sixteen (46.8%) of the 248 staphylococcal isolates were sensitive to all the agents tested. A significant percentage (P less than 0.05) of the isolates from raw milk were resistant to erythromycin, sulphafurazole, cloxacillin, penicillin G and streptomycin compared to isolates from fermented milk. The minimum inhibitory concentrations (MIC) as determined by the tube method for isolates resistant by the disc method, were greater than or equal to 16 micrograms for ampicillin in 5 (11.9%) isolates; greater than or equal to 40 micrograms for cloxacillin, 9 (36.0%) and greater than or equal to 12 international units for penicillin G amongst 12 (22.2%) isolates. MIC values of greater than or equal to 40 micrograms were recorded for 9 (90.0%), 9 (69.2%), 8 (73.7%) and 7 (70.0%) isolates to chloramphenicol, streptomycin, erythromycin and tetracycline respectively. The relatively high level of resistance to antimicrobial agents is a reflection of misuse or abuse of these agents in the environment.