Clinical laboratory evaluation of the automicrobic system Enterobacteriaceae biochemical card.

The AutoMicrobic System Enterobacteriaceae Biochemical Card (AMS-EBC; Vitek Systems, Inc.) was evaluated in two clinical microbiology laboratories. A total of 502 consecutive clinical isolates representing members of the family Enterobacteriaceae were tested in parallel with the AMS-EBC, API 20E, and Enterotube II systems. Discrepancies between systems were resolved with the conventional methods of Edwards and Ewing (P. R. Edwards and W. H. Ewing [ed.], Identification of Enterobacteriaceae, 1972) and Ewing and Martin (W. H. Ewing and W. J. Martin, in Manual of Clinical Microbiology, 1974) AMS-EBC correctly identified 96.6% and incorrectly identified 3.4% of the isolates. When 12 or more isolates of a species were evaluated, Serratia marcescens, Proteus mirabilis, and Enterobacter cloacae posed the greatest challenge to the systems, with 92.6, 95.2, and 95.3%, respectively, being correctly identified. To confirm the accuracy of identification when all systems agreed, 93 randomly selected isolates were identified by conventional methods. The percent agreement was 100%. The reproducibility of triplicate determinations on 93 randomly selected isolates with the AMS-EBC was 99.6%. The AMS-EBC was found to be an easy, rapid, and accurate method for identification of Enterobacteriaceae.

Rapid isolation of bacteria from septicemic patients by use of an antimicrobial agent removal device.

The new Antimicrobial Removal Device increased the efficacy of conventional methods for isolating bacteria from the blood of septicemic patients. The device removes as much as 100 microgram of antibiotics per ml from whole blood without a significant decrease in bacteria. Of 51 patients studied, 31 yielded positive cultures, and the Antimicrobial Removal Device permitted earlier isolation of the causative agent from blood. Subcultured within the first 12 h yielded 12 positive isolates, as the 31 agents were isolated more rapidly after Antimicrobial Removal Device permitted earlier isolation of the causative agent from blood. Subcultures within the first 12 h yielded 12 positive isolates, as compared to 2 when subcultured without processing in the device. Overall, 21 of the 31 agents were isolated more rapidly after Antimicrobial Removal Device treatment, and four samples were positive only after such treatment. One agent was not isolated in the treated culture.

Comparison of serum and plasma specimens for syphilis serology using the reagin screen test.

One serum and three plasma samples were obtained from each of 125 normal individuals and from 140 patients with treated or untreated syphilis. Serum samples were tested by the Venereal Disease Research Laboratory (VDRL) test and by the Reagin Screen Test (RST). Plasma specimens were tested only with the RST. When tested within 24 h after collection, all specimens from normal individuals were nonreactive. Plasma specimens from normal individuals stored for up to 72 h after collection continued to yield a clearly nonreactive result in 423 of the 426 samples tested by the RST. Serum and plasma samples from syphilis patients tested within 72 h after collection by the RST yielded qualitative and quantitative results almost identical to results of serum tested by the VDRL test.

A single-bottle blood culture system: evaluation and comparison with two other systems.

A commercially available single-bottle blood culture system was evaluated at Ben Taub General Hospital, a Harris County District Hospital. Blood cultures from 1010 patients were examined with the Lederle Diagnostics one-bottle blood culture medium-SPS, Columbia broth (E-Vac, Pfizer), and an in-house-prepared brain heart infusion broth with p-aminobenzoic acid (PABA) and 0.1% agar. Of the 1010 patients examined, blood cultures from 211 (20.8%) were positive, yielding a total of 23 different species of microorganisms. Comparison of the results during clinical evaluation, as well as those from simulated blood cultures, showed that the Lederle Diagnostics blood culture bottle was as effective as the in-house-prepared brain heart infusion and commercially available Columbia broths for isolation of aerobes as well as anaerobes. The techniques used in the evaluation and the advantages of a single-bottle culture system are discussed.

Evaluation of reagin screen, a new serological test for syphilis.

A total of 1,020 serum and plasma specimens were tested using the Venereal Disease Research Laboratory (VDRL), Rapid Plasma Reagin (RPR) card, Reagin Screen (RST) and Fluorescent Treponemal Antibody-Absorption (FTA-ABS) tests. In 257 normal patients, all screening tests were nonreactive; the FTA-ABS test was reactive for one patient. In 588 patients with treated and untreated syphilis, the RST results were 91.7% in agreement with the VDRL and RPR results. In 175 patients with diseases that cause biological false reactions, the RST was 94% in agreement with the other screening tests. The titer of the RST was within one dilution of the corresponding VDRL titer in 91.7% of the 360 speciments tested and within one dilution of the RPR titer in 96.9% of 358 specimens quantitated by both tests.

Incidence and etiology of septic meningitis in a metropolitan county hospital.

From January 1, 1969 to December 31, 1974, 98,446 patients were admitted to Ben Taub General Hospital, one of the Harris County District Hospitals and a major teaching institution for Baylor College of Medicine. Spinal fluid specimens from 17,638 (17.9%) patients were cultured, and 787 (4.5%) cultures were positive for pathogenic microorganisms. Haemophilus influenzae, type B, was most frequently isolated (23.8%), followed by Streptococcus pneumoniae (16.0%), Staphylococcus aureus (9%), Neisseria meningitidis (7.3%), and Enterococcus (7.3%). Previous studies have indicated that more than 70% of all the septic meningeal infections are caused by H. influenzae, meningococcus and pneumococcus. At this hospital these organisms were isolated from 47% of the specimens studied, indicating a changing pattern in the etiology of purulent meningitis. Although pediatric patients constituted only 11.5% of the admissions, 58.4% of the pathogenic microorganisms were cultured from these patients.

Meningitis due to Aeromonas hydrophila.

A case of meningitis caused by Aeromonas hydrophila is reported. The infection complicated an otherwise successful frontotemporal craniotomy. Survey of the literature revealed that human infections due to this organism are relatively uncommon, and its causal relationship in meningitis has not been previously reported. A. hydrophila is known to cause bacteremia in patients under treatment with immunosuppresive agents. We report meningitis with bacteremia, caused by this organism, in an immunologically competent host.

Eastern equine encephalomyelitis. Histopathologic and ultrastructural changes with isolation of the virus in a human case.

Enveloped Toga virus particles were demonstrated by means of an electron microscopy in the brain tissues of a 3-year-old girl with acute encephalitis. Areas of demyelinization and necrosis throughout the white matter and brainstem were revealed by light microscopy. These viral particles were identified as eastern equine encephalomyelitis virus in postmortem isolation of the virus utilizing young mice and complement-fixation studies. To the authors' knowledge, this is the first demonstration of eastern equine encephalomyelitis virus particles in human tissues by electron microscopy.

Evaluation of the Gonosticon Dri Dot test in females with a low incidence of gonorrhea.

A group of 765 females attending a Planned Parenthood Clinic was screened for gonorrhea by inoculating Thayer-Martin plates and Transgrow bottles with specimens from the cervix. Blood was obtained at the same time and tested for anti-gonococcal antibody by using the Gonosticon Dri Dot test. In this low-incidence group, 18 positive cultures were detected by culture on Thayer-Martin plates, whereas Transgrow detected only 15 positive cultures. Of the 18 patients with gonorrhea, 11 exhibited reactive serum (agglutination of the latex particles). In the total population, 64% of the patients had nonreactive serum (no agglutination) and negative cultures; 25% had reactive serum and negative cultures. When this latter group was subdivided on the basis of race, blacks and Latin Americans were found to have a higher incidence of reactive serum with a corresponding negative culture than was found in whites. Patients who were originally culture positive and nonreactive in the Gonosticon Test were retested; three out of four patients retested within 6 to 11 days after the initial screening had converted to a positive Gonosticon test.

Differential attachment by piliated and nonpiliated Neisseria gonorrhoeae to human sperm.

Piliated type 1 Neisseria gonorrhoeae attached to 50% of human sperm after incubation of mixtures in vitro for 15 min at 35 C. In contrast, nonpiliated type 4 N. gonorrhoeae attached to only 23% of sperm. Similar results were obtained with three different strains of N. gonorrhoeae. Treatment with heat or formaldehyde to kill bacteria did not affect the amount of attachment by piliated or nonpiliated types. Escherichia coli and N. subflava, other species of piliated bacteria, attached to about 40% of sperm, and the nonpiliated species N. meningitidis and N. catarrhalis attached to a comparable number of sperm, as did type 4 N. gonorrhoeae. Prior incubation of type 1 N. gonorrhoeae with purified antibody prepared against gonococcal pili reduced the percentage of sperm with attached bacteria to the same level as that for nonpiliated type 4 gonococci. Similar treatment of other piliated organisms or of nonpiliated Neisseria did not affect the attachment of the bacteria to sperm.

Comparison of atmospheric conditions for culture of clinical specimens of Neisseria gonorrhoeae.

We cultured 55 clinical specimens of Neisseria gonorrhoeae in the following atmospheric conditions: (i) 10% carbon dioxide in a CO(2) incubator; (ii) a candle extinction jar; (iii) an air convection incubator; and (iv) an anaerobic jar without added CO(2). The number and size of colonies growing on modified Thayer-Martin medium were evaluated after incubation of cultures for 24 and 48 h at 36 C. After 24 h, the specimens from the candle extinction jar had the greatest number and size of colonies, but after 48 h growth was approximately equal for specimens from the candle jar and the CO(2) incubator. Only 19 of 55 specimens grew in the air convention incubator. None of 55 clinical specimens or of 10 laboratory strains grew anaerobically. Development of colonial morphology for colony types 1, 2, 3, and 4 was studied at 24 h on a base medium that contained no hemoglobin. The relative numbers of the four colony types in specimens were comparable after 24 h of incubation in any of the three atmospheric conditions under which growth occurred, but the different types were distinguished most readily when grown in the candle extinction jar.

Variation in colonial morphology of Neisseria gonorrhoeae after growth on media containing antimicrobial agents.

Stable colonial types 1, 2, 3, and 4 were prepared from eight strains of Neisseria gonorrhoeae. Four of the strains, termed laboratory strains, had been transferred over 100 times; three strains, termed clinical strains, were transferred only three to five times after isolation from patients, and one stabilized clinical strain was transferred purposefully 30 times after isolation from a patient. Colonial types of the three categories were grown on four media containing the following agents at the level used in diagnostic media: (i) vancomycin, colistin, and nystatin; (ii) these antibiotics plus trimethoprim lactate; (iii) trimethoprim lactate alone; and (iv) a control with no antimicrobial agents. When grown on media containing the antimicrobial agents, colonial types 1, 2, and 3 of all strains showed specific and consistent changes that precluded accurate identification of the types. In general, the colonies were smaller, more dense to transmission of light, and more granular than colonies grown on control medium. More colonies showed these type changes in the clinical strains and on media containing trimethoprim lactate. Colonies of type 4 showed little or no change. The changes in colonial morphology of types 1, 2, and 3 were pronounced enough to make colony typing difficult if the antimicrobial agents, particularly trimethoprim lactate, were present in media.

Direct immunofluorescence test for the diagnosis of genital herpesvirus infections.

Herpetic lesions of the genitalia may be confused clinically with other ulcerative, genital lesions. Direct immunofluorescence (FA) provides a rapid method of diagnosis, and the utility of this method for the diagnosis of genital ulcers was examined. One hundred and ten patients with genital lesions were examined by darkfield for syphilis and by FA and culture for herpes simplex virus (HSV) infections. Satisfactory samples were obtained from 102 patients, of which 81 were clinically suspected cases of HSV. Acetone-fixed slides of scrapings of ulcerative lesions were stained with conjugated antiserum prepared in rabbits against HSV type 2. HSV was isolated from 73% of specimens of suspected herpetic lesions, and 77% of these specimens were positive by FA. Nine percent were positive by FA only and these were not thought to represent false positives. Five percent were positive by culture only. A comparison of clinical diagnoses with laboratory findings revealed that 4% of the cases were misdiagnosed when only the clinical evaluation was considered. The data suggest that the inclusion of a diagnostic FA test for HSV along with the darkfield examination may be useful for differentiating the etiological agents of ulcerative, genital lesions.

Microtitration of Bacillus cereus hemolysin.

A microtiter procedure for the quantitation of Bacillus cereus hemolysin is described.