A recent approach to the control of staphylococcal problems in hospital nurseries involves the implantation of a peni ci l l i n\x=req-\ sensitive staphylococcus (the 502A strain) in infants in an effort to interfere with colonization by more virulent organisms.1,2 The evaluation of the results of such implantation experiments depends upon accurate and definitive identification of the implanted strain and the ability to differentiate it from other strains of coagulase-positive staphylococci found in the environment. The use of two or more distinct typing systems, especially for cultures from lesions and other infections, greatly improves the reliability of the experiment. Toward this end selected representative staphylococcus strains from the Georgia study 2 were referred to the research laboratory for special serological and phage studies.
Materials and MethodsThe serological system used in this study was developed by Oeding 3-5 and by Haukenes and Oeding.6 Methods of producing reagents and performing the tests are described in a recent paper by Cohen and Oeding.7 The fluorescent antibody method was used to type several auto-agglutinating strains. Antisera for factors, a, b, cp (polyvalent), c\, h, i, k, and m were used. (During the course of this study the monovalent reagent for factor ci was de¬ veloped by adsorption of F21 antiserum with strains Center. from the stock 502A strain, a selected group of nasal and umbilical cultures from inoculated and uninoculated babies, and a few cultures from lesions were typed by both phage and serological proce¬ dures. One hundred colonies of the 502A strain were phage typed to determine the range of variation in vitro. The four colonies listed in Table 1 represent the extent of variation observed.
ResultsThe 502A strain reacted strongly with the monovalent C\ antiserum, the polyvalent cv antiserum, and with the divalent ci antiserum.In addition, it reacted weakly with polyvalent b antiserum. The strain was therefore desig¬ nated type (b)c\ but the strong Ci reaction was the most useful in identifying it. The sero¬ types and phage patterns of representative strains from a nursery study are given in Table 1. Strains of the 52/52A/80/81 com¬ plex, strains of other phage patterns, and a number of strains not typed by our phages exhibited a variety of serological types. In general, those strains associated with each other by phage type were also associated with each other by serotype.In Table 2 the serology and phage results are summarized according to epidemiological data on sources of the cultures. Twenty-three strains with serology characteristic of the 502A staphylococcus (ie, (b) Ci or [ci]) were identified among the cultures referred for special study. Twenty of these were from inoculated babies, including three from a parallel study in Cincinnati which were tested in order to ascertain the similarity between Downloaded From: http://archpedi.jamanetwork.com/ by a University of California -San Diego User on 06/12/2015
