PHAGE-TYPING OF STAPHYLOCOCCI FROM PYOGENIC LESIONS AND CARRIERS IN AND OUTSIDE THE HOSPITAL

Abstract

Coagulase-positive staphylococci obtained from 358 consecutive patients with staphylococcal lesions during 2 years ended April 1959 were phage-typed. Also, staphylococci were isolated from carriers among 55 hospital staffs, 116 trainee nurses, 92 babies and their mothers, and 40 children in an orphanage where an outbreak of boils was in progress.
(1) There was a striking difference between staphylococcal lesions acquired in and outside the hospital. In the majority of instances, group I or type 80 strains were responsible for the hospital infections and group II or type 55/71 and others for the non-hospital cases. In the second year of survey, group I, particularly type 80 strains, have increased markedly and disseminated widely into the general public, while group II strains have decreased, showing a tendency of gradual elimination.
(2) A definite difference of phage-group distribution found among lesion-strains was also found among carrier-strains. Discrepancies in phage-group distribution between lesion-strains and carrier-strains in both hospital and non-hospital groups might suggest differences in pathogenic ability of strains, showing groups I and II strains to be more virulent and group III and the non-typable to be feebly pathogenic.
(3) The highest rate of antibiotic resistance was found in group III, nearly in group I, and the lowest in group II. The rate was higher among hospital strains than among the non-hospital. The rate of isolation of penicillin-resistant strains was fairly high in both lesions and carriers, but the streptomycin-resistants were of rare occurrence among non-hospital carriers-strains at large although they comprised 89% of type 80 strains from hospital lesions. During the second year of survey, antibioticresistant strains have remarkably increased in general, but rather decreased among hospital lesion-strains. Considering that hospital infections have recently increased in both frequency and severity in spite of this finding, resistance to antibiotics may not be taken as a prerequisite for pathogenicity of the strain.
(4) A serial survey of carriers in 2 groups of trainee nurses has shown that during the first 3 months upon entering the wards, group I strains gained an ascendancy over group II, leading to the phage-group distribution typical of hospitalstrains. This changeover of predominant types did not take place during the 2 months of preliminary training, showing that cross infection did not take place in the dormitory. There was some evidence that new flora colonized a sterile site and the carriage of one type protected against the acquisition of another. The nasal and throat mucosa of infants seem to be more susceptible to colonization by staphylococci, which are prevalent in the maternity unit, soon after birth than their mothers.
(5) Although the potentialities of Staphylococcus species to produce any kind of pyogenic conditions are indisputable, phage-typing results appear to show that some differences exist between strains in their ability to produce a particular lesion or lesions. Type 55/71, 52/52A/80, and 80/54/73 showed a higher incidence of skin lesions than the average. A larger number of skin lesions due to type 80, however, may be attributable to the prevalence of strains and not to its unusual propensity, because the incidence of skin lesions due to type 80 strains was found to be below the average. On the other hand, type 80, 80/73, and 55/71 were shown to be more liable to produce breast abscess. It seems that strains from osteomyelitis belong mostly to group II, whereas those from myositis mostly to group I.