Characterization of nontypable Streptococcus pneumoniae-like organisms isolated from outbreaks of conjunctivitis

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Abstract
From Jan. to June, 1980, 7 colleges and universities in various parts of New york State (NYS), USA, reported outbreaks of conjunctivitis affecting at least 1500 students of both sexes. Of the 125 conjunctival swabs tested in a laboratory, organisms identified as nontypable S. pneumoniae were isolated in pure culture from 24% and in combination with other organisms from 22%. Although bile-soluble and susceptible to optochin, the isolates had a dry-colony appearance and no typable capsule with the Neufeld capsular-swelling test. Mouse passage of 4 representative NYS isolates did not stimulate production of a typable capsule. These isolates were referred to as S. pneumoniae-like organisms. Of primary importance to this study, all NYS isolates tested were similar in biochemical and immunological reactions, antibiotic susceptibility and virulence in mice. Of 18 strains from 3 other outbreaks (California, 1980; NYS, 1981; Illinois, 1981), 4 of the 6 tested biochemically gave the same biochemical reactions as the 4 NYS isolates; 16 of the 18 tested immunologically reacted strongly with antisera produced against those 4 isolates, showing line(s) of identity with each other and with the NYS isolates.