Each of three isolates of Streptococcus faecalis subsp. zymogenes harbored three R plasmids and a hemolysin-bacteriocin plasmid. The plasmids carried by one of these strains were physically characterized after their conjugative transfer. In each strain one of the plasmids carried genetic markers for resistance to gentamicin, kanamycin, sisomicin, netilmicin, and tobramycin.

The results of 20 physiological and fermentation tests and examination of the penicillin-binding proteins (PBPs) of 85 enterococcal strains demonstrated that the genus Enterococcus could be divided into at least nine distinct species : E. faecalis, E. faecium, E. durans, E. hirae, E. auium, E. gallinarum, E. casselijlavus, E. malodoratus and E. mundtii. Each species had a specific pattern of at least five PBPs, with molecular masses in the range of about 40-1 30 kDa. The pattern of PBPs may be useful for identification purposes, since some strains with unusual fermentation characteristics were assigned to species by this technique.

Of 20 clinical isolates of group A, B, G, D (Streptococcus bovis), and viridans streptococci, 5 transferred their antibiotic resistance markers into streptococcal recipients at a low frequency (10(-4) to 10(-8)) in the apparent absence of extrachromosomal elements. All strains carried genetic markers for high-level resistance to streptomycin, kanamycin, neomycin, lividomycin A, and ribostamycin, as well as resistance to macrolides and related drugs, tetracycline, and chloramphenicol.

An assay based on the utilization of degenerate primers that enable enzymatic amplification of an internal fragment of cat genes known to be present in gram-positive cocci was developed to identify the genes encoding chloramphenicol resistance in streptococci and enterococci. The functionality of this system was illustrated by the detection of cat genes belonging to four different hydridization classes represented by the staphylococcal genes catpC221, catpC1949 catpSCS79 and the clostridial gene catP, and by the characterization of a new streptococcal cat gene designated catS. A sequence related to the clostridial catQ gene, which was present in one streptococcal strain, was not detected by this assay. These results reveal that these six cat genes account for chromosomal-borne chloramphenicol resistance in 12 group A, B, and G streptococci tested. By contrast, only three of these six cat genes (catp'221, catj%94 and catpsCS7) were detected on the 10 enterococcal plasmids studied here that encode resistance to chloramphenicol.Chloramphenicol resistance (Cmr) in bacteria of clinical importance is generally due to the synthesis of the enzyme chloramphenicol acetyltransferase (CAT) which inactivates the antibiotic by converting it successively to 3-acetyl and 1,3-diacetyl derivatives (31). Comparison of the amino acid sequences of 17 CAT proteins from gram-negative and gram-positive bacteria has revealed a significant degree of homology between the various enzymes, and their phylogenetic relationship has been established (2, 18, 29). Nucleotide sequences are now available for 13 cat genes originating in gram-positive bacteria. These are the gene cat-86 from Bacillus pumilus (10); those carried by the staphylococcal plasmids pC194 (11), pC221 (32), pSCS1 (30), pSCS5 (28), pSCS6 (7), pSCS7 (29), and pUB112 (5) and by the streptococcal plasmid pIP501 (12,35) Utilization of degenerate primers in polymerase chain reaction (PCR) enables the detection of rRNA methylase genes that confer resistance to macrolide-lincosamide-streptogramin B-type (MLS) antibiotics in gram-positive bacteria (1). We have developed a similar assay in order to characterize the cat genes present in the remaining seven plasmidfree streptococci (23) and in the three Enterococcus faecalis plasmids (26) which did not detectably hybridize with catp.221 (or catpIP501) and cat C194* In addition, one E. faecalis and six Enterococcus [aecium plasmids coding for Cmr were included in this study. MATERIALS AND METHODSBacterial strains and culture conditions. The main characteristics of the strains and plasmids used in this study which carried unidentified cat genes are listed in Table 1

A method for the speciation of viridans streptococci (non-groupable) is described. The major identification criteria are based on the reactions to a series of biochemical tests, including acid production in lactose, inulin, raffinose, mannitol and sorbitol, hydrolysis of arginine, esculin and Na hippurate, and production of polysaccharides in 5% sucrose media. A total of 450 strains was isolated from blood cultures, 183 of which were from confirmed cases of subacute endocarditis. The latter were identified as follows (%): Streptococcus sanguis I (25.7), S. mitis (19.7), S. sanguis II (19.7), S. mutans (17.5), S. milleri (12), S. morbillorium (3.2) and S. salivarius (2.2). Susceptibility to antibiotics was studied for 129 of these strains: 68% were susceptible to all drugs tested, 20% were resistant only to tetracycline, 4% only to penicillin (MIC = 0.5-4 micrograms ml-1) and 8% were multiply resistant (tetracycline, macrolides and related drugs, chloramphenicol, penicillin, high-level resistance to kanamycin and/or streptomycin [MIC = 1000-80.00 micrograms ml-1].