[Characterization of methicillin-resistant Staphylococcus aureus strains isolated from 1974 to 1983 in West Germany with respect to the results of lysotyping].

Abstract

A total of 594 methicillin-resistant (MER) S. aureus strains originating from the Federal Republic of Germany were both tested for their susceptibility to a number of selected antimicrobial agents, and lysotyped with the international set of S. aureus typing phages. Control groups of methicillin-sensitive, but penicillin- (PER) and gentamicin-resistant (GER) strains were tested for comparison. A group of S. aureus strains susceptible to all of the agents tested was included in the statistical evaluation of the lysotyping results. 98% of the MER and 72% of the GER S. aureus strains were cross-resistant towards at least five of the other agents tested. 84 to 97% of the MER strains were resistant to erythromycin, tetracycline, kanamycin and gentamicin. The in vitro susceptibility towards lincomycin and amikacin was in the range of 50 to 60%. The strongest in vitro efficacy--both against the MER and the GER strains--was shown by vancomycin and fusidic acid. 52.9% of the MER and 47% of the GER strains, but only 12.3% of the non-resistant strains and no more than 15% of the PER strains belonged to phage-group III; a higher proportion of these latter groups reacted with phage-group I, which was rare among the MER and the GER strains (3.2% and 7.8% respectively). The most frequent phage-patterns of the MER strains were as follows: 47/75/77, 47/54/75/77/84/85, 77/84/85, 47/54/75/77/85, 6/47/54/75/77/84/85, and 55/83A. Most of the phage-group III lysotopes occurred at numerous places across the country, while mixed lysotypes were apparently more confined to certain areas. A relatively high percentage of the MER strains, but notably also of the sensitive strains was non-typable (22.1% and 24.1% respectively), whereas the PER and the GER strains had a considerably lower rate of non-typability (9.3% and 4.8% respectively). A correlation between non-typability and multiresistance was not evident.