Emergence of Multiply Resistant Pneumococci

Multiple antimicrobial resistance in pneumococci was detected in Johannesburg in July, 1977, and prompted an investigation of the prevalence of resistant strains in two hospitals. Carriers of Types 6A and 19A penicillin-resistant pneumococci, resistant to antibiotic concentrations ranging between 0.12 and 4 μg per milliliter were found in 29 per cent of 543 pediatric patients and 2 per cent of 434 hospital staff members. Multiply resistant Type 19A strains, resistant to β-lactam antibiotics, erythromycin, clindamycin, tetracycline and chloramphenicol, were isolated from 128 carriers, and were responsible for bacteremia in four patients. Isolates from 40 other carriers were resistant to penicillin alone or to penicillin and chloramphenicol or to penicillin, chloramphenicol and tetracycline. Pneumococci can be screened for penicillin resistance with a modified Kirby-Bauer technic; the strains with zones of <35 mm around 6-μg penicillin disks or <25 mm around 5-μg methicillin disks should be tested for sensitivity to penicillin by measurements of minimum inhibitory concentration. (N Engl J Med 299:735–740, 1978) ALTHOUGH penicillin-resistant strains of Streptococcus pneumoniae have been selected in vitro after exposure to increasing concentrations of penicillin,1 until recently, strains resistant to >2 μg per milliliter have not been isolated from clinical specimens. Pneumococcal infections have therefore been treated empirically with penicillin, and in many laboratories, isolates have not been routinely tested for antibiotic susceptibility.2 Strains relatively resistant to penicillin (minimum inhibitory concentration ≤1 μg per milliliter) have been reported from Australia and New Guinea,34567 Canada,8 England9 and the United States,1011 and some strains resistant to up to 2 μg per milliliter have been reported from New Guinea.12 Resistance. © 1978, Massachusetts Medical Society. All rights reserved.