A CONTROLLED STUDY OF THE USE OF PROPHYLACTIC ANTIMICROBIALS IN PREMATURE INFANTS

Abstract

Studies of the aerobic bacterial flora of the nose and throat were made during the first month of life in premature infants born in the hospital and selected by cyclic rotation for treatment with either penicillin plus streptomycin, sulfadiazine, oxytetracycline, or saline for a period of 10 days. The initial cultures made during the first few hours after birth yielded no growth in 90% of those from the nose and in 80% of those from the throat; in nearby every instance in which bacterial growth occurred in the initial cultures, the conditions either in the pregnancy, the delivery or the infant at birth were such as to predispose the baby to contamination. Staphylococci were most often the first organisms to appear in both nose and throat and were also the most prevalent and most persistent. Coagulase-positive strains were the most frequent in nasal cultures and coagulase-negative ones in those from the throat; the latter variety was particularly prevalent during the first 10 days. Strains of Str. viridans ranked next in incidence; they were recovered predominantly from the throat cultures and with increasing frequency through the thirtieth day. Enterococci were cultured only between the third and fifteenth days. Beta hemolytic streptococci were repeatedly recovered from a few infants in the sulfadiazine-treated group and H. influenzae was grown once from each of three infants but these organisms did not cause any overt infections. Coliform organisms first appeared during the second week and increased in frequency through the thirtieth day. The strains of staphylococci were predominantly resistant to all of the antimicrobials used, including sulfadiazine, whereas the various streptococci were almost all sensitive to these agents; however, most of the enterococci were resistant to streptomycin alone and moderately resistant to oxytetracycline. The coliform organisms were nearly all resistant to penicillin and to sulfadiazine and most of them except the strains of pseudomonas were sensitive to streptomycin, alone or in combination with penicillin and also to oxytetracycline; however, the strains of proteus were either moderately resistant or resistant to oxytetracycline. Antimicrobial therapy appeared to have only minor and limited effects on the bacteriologic findings. Enterococci were most frequently isolated during antimicrobial therapy, particularly with sulfadiazine or oxytetracycline, but strains of Str. viridans or of E. coli were rarely isolated during treatment with the latter. Implantation and persistence of beta hemolytic streptococci were not prevented by treatment with sulfadiazine although the strains isolated were sensitive to that agent in vitro. The strains of staphylococci, particularly the coagulase-positive ones, which were isolated from the infants treated with oxytetracycline included a smaller proportion that were sensitive and more that were resistant to all the antibiotics with which they were tested as compared with those obtained from the babies in any of the other therapeutic groups.