Direct susceptibility testing of blood culture isolates with the AutoMicrobic System (AMS).

To decrease the time needed to obtain preliminary antimicrobial susceptibility results with blood culture isolates, we inoculated a suspension of centrifuged organisms from blood culture broth directly into the AutoMicrobic System Gram-Positive (GPS) and Gram-Negative (GSC+) susceptibility cards (AMS, Vitek Systems Inc., Hazelwood, MO). Interpretive category results (susceptible, moderately susceptible, resistant) obtained by this direct method (DAMS) were then compared with results obtained by conventional inoculation (i.e., using 18-hr subcultures) of both AMS cards (CAMS method) and broth microdilution panels (MIC method, Micro-Media Systems Inc., Potomac, MD). Ninety-six Gram-positive cocci (951 antimicrobial agent--organism combinations) and 112 Gram-negative bacilli (1006 antimicrobial agent-organism combinations) were tested. When only very major (false susceptible DAMS results) and major (false resistant DAMS results) discrepancies were considered, 95% of the DAMS results for Gram-positive cocci agreed with CAMS results and 93% agreed with MIC results. Most discrepancies were observed when staphylococci were tested against oxacillin and when enterococci were tested against several antimicrobial agents. For Gram-negative bacilli, 94% of DAMS results agreed with CAMS results and 93% agreed with MIC results. Most discrepancies occurred when Enterobacter spp. and Serratia marcescens were tested against ampicillin and cefamandole. The DAMS method provides accurate and rapid preliminary susceptibility test results, usually within 6 to 7 hr of the time a positive blood culture is first detected.

Diagnosis of measles by fluorescent antibody and culture of nasopharyngeal secretions.

An indirect fluorescent antibody test (IFA) was evaluated using commercial mouse anti-measles monoclonal antibody and FITC-labeled goat anti-mouse immunoglobulin. For measles isolation, specimens were inoculated into Rhesus monkey kidney (RMK) cells and, when available, CV-1 cells. 381 specimens were tested by IFA and 408 specimens were cultured from patients suspected of having measles. For the 381 specimens tested by both methods, IFA and culture were positive for 31%, culture alone for 14%, IFA alone for 15%, and both negative for 40%. This study indicates that both IFA and culture are required for maximum measles virus detection. Of the positive specimens, 48% were detected either by IFA only (24%) or culture only (24%). IFA was positive in 69% of the culture-positive specimens and therefore, provided rapid diagnosis for many patients.

Organisms associated with gram-negative folliculitis: in vitro growth in the presence of isotretinoin.

Isotretinoin has been found to be effective in the treatment of Gram-negative folliculitis. We investigated the direct in vitro antibacterial activity of isotretinoin against Gram-negative species. The concentrations of isotretinoin tested were two and ten times greater than the maximal levels attained in the sera of patients receiving oral isotretinoin. Regardless of the inoculum size, each organism tested grew as well in isotretinoin-containing media as it did in the control medium. These findings suggest that the efficacy of isotretinoin in patients with Gram-negative folliculitis is due to mechanisms other than direct antimicrobial action.

Microflora associated with percutaneous craniofacial implants used for the retention of facial prostheses: a pilot study.

Craniofacial implants have been used successfully for the retention of facial prostheses. However, complications occur that can lead to the loss of implant integration. One such complication is infection possibly resulting from crevicular microflora activity. As part of an ongoing study, samples from crevicular sites surrounding 17 craniofacial implants were collected and submitted for microbiological assay. The results demonstrated the presence of opportunistic pathogens in many sites regardless of subjects' hygiene efforts. The significance of the findings is reviewed.

Neisseria gonorrhoeae: methods for laboratory identification.

Clinical laboratorians must use methods that will allow isolation of gonococci from both genital and extragenital sites. Whenever possible, nonselective as well as antibiotic-containing media sould be used because some gonococci are susceptible to the concentrations of vancomycin present in selective media. For identification, subculture of the primary isolate onto nonselective medium not only assures that a pure culture is used, but also provides sufficient inoculum for a rapid result. At present, the most common gonococcal identification methods are carbohydrate degradation tests performed with CTA-base carbohydrate media, buffered carbohydrate solutions, the Minitek and the BACTEC systems, and the coagglutination immunologic method. Although penicillinase-producing N. gonorrhoeae have not become as widespread a problem as expected, methods for their detection should be available in the laboratory.

Clinical Microbiology Reviews: genesis of a journal.

In 1986 planning for a new ASM review journal, Clinical Microbiology Reviews (CMR), began. CMR would publish articles primarily of interest to persons concerned with pathogenesis, laboratory diagnosis, epidemiology, and control of human and veterinary pathogens. The first issue was published in January 1988, with quarterly publication since then. The journal quickly became successful in terms of subscribers and impact on the field, earning a strong national and international reputation. The achievements of CMR are owed to many persons, including the editorial board, the production team, and especially the contributing authors.

Serovars and serum resistance of Neisseria gonorrhoeae from disseminated and uncomplicated infections.

Two hundred and seventy-four gonococcal strains isolated from patients with either disseminated (DGI) or uncomplicated (UG) infection were examined to determine their serotypes/serovars by two typing systems as well as their resistance to the bactericidal action of normal human serum. The bactericidal assays were performed in particular to determine whether isolates from patients with the clinical syndrome of DGI but negative systemic cultures (suspected DGI) were serum-susceptible. When strains containing protein IA in their outer membranes and having auxotypes other than the arginine-hypoxanthine-uracil requirement were serotyped, a significant difference was found in the distribution of serovars among strains from DGI and suspected DGI compared with UG. The two typing systems revealed both antigenic similarities and differences of gonococci from Chicago and isolates from Germany reported in another study. Like DGI strains, most suspected DGI strains contained protein IA and were resistant to the bactericidal action of serum.

Rapid detection and identification of enteric bacteria from blood cultures.

The BACTEC radiometric system and Inolex Enteric I card were used in conjunction for the rapid detection and presumptive identification of enteric gram-negative rods in blood cultures. Excellent correlation was obtained between the Inolex card and routine identification techniques when organisms from both artificially inoculated and clinical blood cultures were studied. In many instances, the culture report was available less than 24 hr after receipt of the specimen.

New medium for blood cultures.

A new medium suitable for blood cultures is described. It contains dextrose, cysteine, iron, and magnesium, in a tris(hydroxymethyl)aminomethane buffer, and a mixture of peptones derived from animal tissues, casein, and yeast. In comparison with Trypticase Soy Broth, the growth rate constants of Staphylococcus aureus, Streptococcus (Viridans group), enterococcus, and Escherichia coli were higher in this medium, and growth appeared earlier in a significant number of clinical blood cultures.

Use of the API NeIdent system for identification of pathogenic Neisseria spp. and Branhamella catarrhalis.

The API NeIdent system (Analytab Products, Plainview, N.Y.) was evaluated for identifying Neisseria spp. and Branhamella catarrhalis commonly isolated from clinical specimens. The system identified 90% of 303 Neisseria gonorrhoeae isolates, 71% of 113 Neisseria meningitidis isolates, and 63% of 16 Neisseria lactamica isolates but failed to identify any of 22 B. catarrhalis isolates. Testing of gonococcal strains of various auxotypes revealed no relationship between nutritional requirements and NeIdent profile numbers. With the Neisseria species, interpretation of the cinnamaldehyde-coupled beta-naphthylamine reactions was difficult and resulted in profile numbers not listed in the Profile Register. Positive resazurin-glucose reactions resulted in unlisted numbers for all B. catarrhalis strains. Inconsistent results were also obtained when 62 N. gonorrhoeae isolates were tested more than once on the strip. In all cases, profile variability and failure to identify these organisms were related to the beta-naphthylamide substrate tests. Expansion of the data base and modification of the substrate formulations or their interpretive criteria may increase the reliability of the NeIdent system for identifying Neisseria spp. and B. catarrhalis.