Correlation between phenotypic characteristics and DNA relatedness within Enterococcus faecium strains.

We noted that a number of enterococcal strains isolated from human clinical specimens resembled Enterococcus faecium but were able to produce acid from glycerol, raffinose, and/or sorbitol, while others failed to form acid from mannitol. An additional concern was that many of these strains with atypical phenotypic characteristics also appeared to acquire vancomycin resistance. In order to determine if such atypical strains were variants of E. faecium or new Enterococcus species, 35 E. faecium or E. faecium-like strains (grouped into 10 phenotypes on the basis of the results of the following tests: capacity to form acid from glycerol, mannitol, raffinose, or sorbitol and susceptibility to vancomycin) and four strains of Enterococcus faecalis were taken from our culture collection, analyzed for their whole-cell protein profiles by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and identified to the species level by DNA-DNA reassociation experiments. All E. faecium-like strains, including four mannitol-negative variants, conformed to at least two of three DNA-DNA relatedness criteria: they were 70% or more related to the type strain of E. faecium at optimal conditions, they had less than 5% divergence within the related sequences, and they had a relatedness of 60% or greater under stringent conditions. The protein profiles of atypical strains were similar to those of typical strains and were easily distinguishable from those of E. faecalis and other enterococcal species. The five E. faecalis strains were 12 to 16% related to the E. faecium type strain. These results indicate that the phenotypic description of E. faecium should include all of these variable characteristics.

Antimicrobial susceptibility patterns of common and unusual species of enterococci causing infections in the United States. Enterococcal Study Group.

We collected 705 isolates of enterococci (1 per patient) from cultures of a variety of anatomic sites from patients at eight tertiary-care hospitals in six geographic regions of the United States. A total of 632 (90%) Enterococcus faecalis, 58 (8%) E. faecium, 5 E. gallinarum, 4 E. avium, 3 E. casseliflavus, 1 E. raffinosus, and 1 E. hirae isolate and 1 biochemical variant of E. faecalis were identified; 606 (86%) of these isolates were associated with clinical infections. The most common sites of isolation were the urinary tract (402 [57%]), nonsurgical wounds (94 [13%]), the bloodstream (74 [10%]), and surgical wounds (62 [9%]). High-level resistance to gentamicin or streptomycin or both was detected in 265 (38%) of the isolates. We identified two E. faecalis isolates resistant to vancomycin (MICs, 32 and 128 micrograms/ml) and 11 beta-lactamase-producing E. faecalis isolates. E. faecium isolates were significantly more resistant than E. faecalis isolates to penicillin, ampicillin, piperacillin, imipenem, and ciprofloxacin (P less than 0.001). The MICs for the 15 non-E. faecalis, non-E. faecium enterococci indicated variable resistance to ciprofloxacin and the penicillins. Antimicrobial susceptibility patterns vary among species of enterococci, and these organisms, while commonly resistant to high-level aminoglycosides, can also acquire resistance to vancomycin or the ability to produce beta-lactamase. Because of these diverse antimicrobial resistance mechanisms, successful treatment and control of enterococcal infections with current antimicrobial agents are becoming increasingly difficult.

Differentiation of Lactococcus lactis and Lactococcus garvieae from humans by comparison of whole-cell protein patterns.

We tested 12 reference and 24 clinical strains of lactococci for physiologic characteristics using a conventional test system, the Gen-Probe Enterococcus 2 chemiluminescence assay (Gen-Probe Inc., San Diego, Calif.), the Rapid Strep identification system (Analytab Products, Plainview, N.Y.), and whole-cell protein analysis. The Gen-Probe Enterococcus 2 chemiluminescence assay for Enterococcus identification was negative with all strains. Neither the conventional test nor the Rapid Strep identification system could differentiate between the two Lactococcus spp. most commonly isolated from humans. A simple procedure, based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was developed for comparing the whole-cell protein patterns of Lactococcus spp. L. lactis and L. garvieae were differentiated by unique protein patterns.

Enterococcus dispar sp. nov. a new Enterococcus species from human sources.

The partial 16S rRNA sequences of two unknown human enterococcal isolates were determined by reverse transcription in an attempt to clarify their taxonomic position. The sequence data indicate that they belong to a hitherto unknown species of Enterococcus, for which the name Enterococcus dispar sp. nov. is proposed. The type strain is NCIMB 13000.

Panel of reference strains for evaluating serologic reagents used to identify gonococci.

A panel of strains for evaluating Neisseria gonorrhoeae serologic reagents was developed. The strains selected for the panel were antigenically diverse and representative of strains isolated worldwide and had been isolated from a variety of anatomic sites. A few strains with characteristics that can cause problems in serologic tests were included. The panel of 52 gonococcal and 20 nongonococcal strains was used to evaluate two commercially produced kits with monoclonal antibody reagents, GonoGen and Phadebact, and one Phadebact kit with absorbed rabbit antiserum. The GonoGen reagent correctly identified all gonococcal strains and did not react with any of the nongonococcal strains. The Phadebact absorbed antiserum reagent correctly identified 47 of 48 gonococcal strains but reacted with 2 of the 20 nongonococcal strains. The Phadebact monoclonal antibody reagent correctly identified all the gonococcal strains; however, it gave positive reactions with 8 and trace reactions with 4 of the 20 nongonococcal strains.

Comparison of serologic screening tests for brucellosis.

The slide agglutination test (SAT), microagglutination test (MAT), and card agglutination test (CAT) were compared with each other, using the tube agglutination test (TAT) as the standard method, by two reference laboratories to determine effectiveness as screening tests for human brucellosis. TAT titers of 1,253 sera tested in both laboratories were compared. In one laboratory, 1,270 sera were tested by the TAT and SAT, while the other laboratory tested 1,261 sera by both methods. Of these sera, 1,155 were tested in one laboratory by the CAT and 187 sera were tested by the MAT. Compared with that of the TAT (greater than or equal to 160 positive), the sensitivities were 97 to 100% (SAT), 90% (CAT), and 88% (MAT). The specificities were 88 to 89% (SAT), 98% (CAT), and 88% (MAT). For populations with a low prevalence of disease, increased specificity offers higher predictive value, so the CAT and MAT are preferable for screening purposes and the choice between tests depends on the number and frequency of tests performed. All sera reactive in the CAT and MAT should be retested with the TAT.

The development by the Centers for Disease Control of a specification for streptococcal serogrouping kits and its application to Streptex and to the Phadebact Streptococcus Test.

A Centers for Disease Control (CDC) specification for evaluating commercially produced streptococcal agglutination reagents was developed and used to test Streptex and Phadebact Streptococcus Test kits. Evaluation methods and performance requirements were based on product claims made in the package labelling. Except for the reagent for Streptococcus group D, reagents of both systems identified 100% of the blind-coded reference strains when follow-up methods were done according to the manufacturers' directions. Streptex group D reagent did not identify all group D strains, but the manufacturer instructed the user to test with other methods in certain circumstances. The interaction of personnel of the Center for Infectious Diseases (CID), CDC, with commercial producers and consumers in a pre-market evaluation program is described.

Use of acetone-dried vaccines for preparing capsular antisera against the Klebsiella group and the lyophilization of Klebsiella cultures.

Capsular antisera against the 72 types of Klebsiella have been prepared in rabbits by using an acetone-dried vaccine. It was shown that encapsulated cells dried with acetone and ground to a fine powder with a mortar and pestle retain their capsules. Antisera obtained from rabbits vaccinated with these vaccines had quellung titers ranging from 1:16 to 1:64. The dried vaccine was stable after storage for over 2 years at room temperature. Encapsulated cultures lyophilized in the presence of 5% sucrose, 5% sodium glutamate, and 5% polyvinylpyrrolidone remained viable and retained their capsules after storage for 10 months at room temperature.