Identification of amino acid residues in GluR1 responsible for ligand binding and desensitization.

Although GluR1(o) and GluR3(o) are homologous at the amino acid level, GluR3(o) desensitizes approximately threefold faster than GluR1(o). By creating chimeras of GluR1(o) and GluR3(o) and point amino acid exchanges in their S2 regions, two residues were identified to be critical for GluR1(o) desensitization: Y716 and the R/G RNA-edited site, R757. With creation of the double-point mutant (Y716F, R757G)GluR1(o), complete exchange of the desensitization rate of GluR1(o) to that of GluR3(o) was obtained. In addition, both the potency and affinity of the subtype-selective agonist bromohomoibotenic acid were exchanged by the Y716F mutation. A model is proposed of the AMPA receptor binding site whereby a hydrogen-bonding matrix of water molecules plays an important role in determining both ligand affinity and receptor desensitization properties. Residues Y716 in GluR1 and F728 in GluR3 differentially interact with this matrix to affect the binding affinity of some ligands, providing the possibility of developing subtype-selective compounds.

Evaluation of the Cellmatics and direct monoclonal fluorescence antibody staining for detection of genital chlamydial infections.

Three methods for Chlamydia trachomatis detection were compared: the Cellmatics (Difco Laboratories, Detroit, MI), a commercially available tissue culture system which contains a rat cell line; a direct fluorescent Chlamydia antibody (DFA) (Microtrak, Syva Corp., Palo Alto, California) stain; and a standard tissue culture isolation method employing McCoy cells. Of the 121 specimens in the study, 20 were positive by the standard cell culture. All 20 of these specimens were also positive by the Cellmatics but only 10 were positive by DFA.

Identification of oxidase-positive, glucose-negative, motile species of nonfermentative bacilli.

Motile and glucose-negative nonfermentative bacilli are difficult to identify by commonly used procedures. We found eight features (reduction of nitrate and nitrite, acidification of fructose, and alkalinization of acetamide, arginine, histidine, saccharate, and urea) that identified 83% of 143 strains. These, along with additional biochemical tests, effected identification of 93% of the strains. Hence, only a minority of these strains required examination by microscopy (for type of flagellation and presence of inclusion bodies) for complete identification.

Probable Campylobacter fetus subsp. fetus gastroenteritis.

Three strains of Campylobacter fetus subsp. fetus isolated from cases of gastroenteritis are reported. DNA-DNA hybridizations in addition to biochemical tests were used to confirm the identification of the isolates as C. fetus since all strains grew at 42 degrees C. These isolates, like other C. fetus strains, are susceptible to cephalothin and thus would not have been detected in laboratories with Campylobacter isolation media containing this component.

Salient features of Haemophilus vaginalis.

A total of 78 strains of Haemophilus vaginalis were examined for 104 features. All strains fermented dextrin, maltose, and starch. Additionally, more than 90% of the strains fermented galactose, glucose, and ribose. Arbutin, cellobiose, melibiose, rhamnose, and salicin were not fermented by any of these strains. None of the strains acidified any of 14 alcohols or alkalinized any of 25 organic salts and amides. More than 90% of the strains hemolyzed human blood agar and hydrolyzed hippurate. No strain hemolyzed sheep blood agar. A recommendation is included for those minimal features that best differentiate H. vaginalis from other oxidase- and catalase-negative, gram-negative organisms.

A study of the Va-1 group of pseudomonads and its relationship to Pseudomonas pickettii.

The Va-1 group of denitrifying pseudomonads was characterized and compared with Pseudomonas pickettii (Va-2). They share many features but differ in their production of acid from cellobiose, lactose and maltose and in their denitrification (gas from nitrate) at 35 degrees C. DNA-DNA hybridizations between a strain of Va-1 and the type strain of P. pickettii disclosed 84% homology and hence indicated that Va-1 is a biovar of this species. Since both are potential human pathogens, features are presented that distinguish these and other phenotypically similar species that are recovered from clinical specimens.

Deoxyribonuclease: detection with a three-hour test.

A three-hour test has been developed to determine deoxyribonuclease activity of Enterobacteriaceae and staphylococci. The test is inexpensive and easy to perform. The rapid deoxyribonuclease test and the conventional method showed complete agreement with the strains tested.

Isolation and rapid identification of Haemophilus ducreyi.

During a 2-month period, 62 strains of Haemophilus ducreyi were isolated from 168 genital lesions and 2 lymph node aspirates. Of these strains, 22 were found on both chocolate agar and fetal bovine serum agar supplemented with vancomycin, 29 were found only on chocolate agar, and 9 were found only on fetal bovine serum agar. Two additional strains were isolated on sheep blood agar. All of these isolates were correctly identified with the RapID NH system (Innovative Diagnostic Systems, Inc., Decatur, Ga.) a new identification kit that has a database for Haemophilus, Neisseria, and other genera that include fastidious gram-negative bacilli.

Evaluation of acridine orange stain for detection of Trichomonas vaginalis in vaginal specimens.

Vaginal exudates from 105 patients were examined by direct wet-mount microscopy and acridine orange stain for the presence of Trichomonas vaginalis. Both procedures demonstrated greater than 90% agreement in both sensitivity and specificity. When specimens can be examined immediately after collection, it appears that wet-mount microscopy is almost as sensitive as acridine orange staining for detection of T. vaginalis.

Isolation of Campylobacter fetus from a pet turtle.

During the course of a Salmonella agona case investigation, Campylobacter fetus was isolated from a pet turtle. This is the first reported isolation of C. fetus from a turtle and suggests that turtles, in addition to being reservoirs for Salmonella species, may also be reservoirs for C. fetus.

Tests for detecting degradation of gelatin: comparison of five methods.

Five methods for detecting degradation of gelatin by bacteria were compared. These were liquefaction in nutrient broth, hydrolysis in nutrient agar, hydrolysis of charcoal gelatin strips, degradation of the gelatin on strips of photographic film, and alkalinization of gelatin agar. Degradation of photographic film is a rapid and convenient method but, like hydrolysis of gelatin in broth and in agar, may fail to detect weakly positive strains of bacteria. Alkalinization of gelatin in an agar medium is a convenient and sensitive method to detect degradation of gelatin, particularly by Pseudomonas fluorescens, but this method may not be applicable to some species.

Recovery of Yersinia enterocolitica from streams and lakes of California.

Stream and lake water from the Mammoth Lakes region of California was sampled for Yersinia enterocolitica. From 10 of the 34 sites examined, organisms were isolated that were biochemically identified as Y. enterocolitica. Only one of the ten strains could be serologically confirmed. This strain was identified as Y. enterocolitica serotype 16. Although an outbreak of enteritis in the area prompted this study, no correlation with gastrointestinal disease could be established since the majority of the strains were untypeable.

Clinical isolation of Yersinia enterocolitica: cold temperature enrichment.

A cold-temperature enrichment procedure was used to isolate Yersinia enterocolitica serotype 6 from a clinical stool specimen. The use of conventional laboratory media and enrichment procedures failed to isolate this organism.

Effect of holding temperature on isolation of Neisseria gonorrhoeae.

The effect of holding temperature on the recovery of Neisseria gonorrhoeae was studied. From 300 specimens tested, Thayer-Martin medium plates inoculated and incubated in the presence of CO2 at 35, 22, and 4 degrees C for 24 h before incubation at 35 degrees C yielded 100, 96, and 95% of all isolates ultimately recovered from 82 positive specimens. Although there was a decrease in the quantity of organisms recovered, initial incubation of specimens under refrigeration or at room temperature yielded greater than or equal to 95% of the positive specimens.

Molecular techniques for the detection of Chlamydia trachomatis.

A DNA probe assay (PACE; Gen-Probe, San Diego, Calif.) was compared with a culture reference method for the detection of Chlamydia trachomatis. Using stock isolates of each of the 15 serovars (A to K, Ba, L1, L2, and L3) of C. trachomatis, the lower limit of sensitivity for the DNA probe ranged between 1,086 inclusion-forming units (IFU) for serovar E (Bour) to 2,930 IFU for serovar L1 (440), with the only exception being serovar C (TW-3), with which 99 IFU was detected. There was no cross-reactivity with Chlamydia psittaci (Texas turkey) and Chlamydia pneumoniae (TWAR-183). Bacterial and fungal isolates representing 14 species of normal vaginal flora as well as Neisseria gonorrhoeae gave negative results with the DNA probe when tested at a level of 1.5 X 10(7) CFU/ml. In addition, the DNA probe, a direct fluorescent-antibody stain (DFA) (MicroTrak; Syva Corp., Palo Alto, Calif.), and an enzyme-linked immunosorbent assay (Chlamydiazyme; Abbott Laboratories, North Chicago, Ill.) were compared with culture for the detection of C. trachomatis, using 196 clinical cervical samples. Of the 196 samples, 20 (10%) were culture positive. Of the 176 culture-negative samples, 1 was not evaluated by DNA probe and 4, because of a lack of cellular material, were not evaluated by DFA. The sensitivities of the DNA probe, DFA, and enzyme-linked immunosorbent assay were 60, 75, and 85%, respectively, and specificities were 95, 99, and 97%, respectively. Of the false-positive direct results, there was only one specimen with which more than one direct method was positive, and with this specimen all three direct methods were positive. The majority of false-negative results by the direct methods were from specimens which by the culture method gave <100 IFU per culture.

A rapid immunofluorescent procedure for serodiagnosis of Q fever in mice, guinea pigs, sheep, and humans.

The ability to diagnose Q fever has been hampered by the fact that diagnosis depends upon difficult serologic tests such as complement fixation (CF) or slide immunofluorescence performed only at reference laboratories. A new quantitative solid phase fluorescent antibody test (FIAX) has recently been developed and applied to measure antibodies in several microbial systems. The test takes less than 2 hr to perform and employs stable reagents. We have utilized this technique and developed a rapid immunofluorescent assay for detection of antibodies to Coxiella burnetii in man and animals. Sera from guinea pigs and mice immunized with phase I vaccine and from naturally infected sheep show high levels of fluorescence against both phase I and phase II antigens by this technique. We have tested over 100 CF positive humans from a recent laboratory outbreak of Q fever and find an excellent correlation between FIAX and CF results.

Detection, identification, and comparison of Capnocytophaga, Bacteroides ochraceus, and DF-1.

Working independently, three laboratories had recognized considerable similarity among certain strains of dysgonic, fermentative, capnophilic, surface translocating, gram-negative bacilli referred to as Capnocytophaga, Bacteroides ochraceus, and Center for Disease Control biogroup DF-1. To determine the relationship among these groups, 21 strains were exchanged and independently characterized by the three laboratories. Additionally, a fourth laboratory examined the deoxyribonucleic acid homologies of the same strains. Using methods common to dental microbiology, eight of the strains had been isolated from the gingival sulcus and periodontal lesions and identified as Capnocytophaga. Three strains isolated from blood and transtracheal aspirate had been characterized by conventional anaerobic methods and recorded as B. ochraceus. Ten strains isolated from sputum, blood, throat, spinal fluid, and tracheal aspirate had been identified as DF-1 with the methods of E. O. King and a buffered single-substrate technique. All strains were similar in respect to colonial and microscopic morphology, surface translocation, biochemical features, gas-liquid chromatograms of metabolic end products, and deoxyribonucleic acid composition. We conclude that these biogroups should be termed Capnocytophaga species.

An outbreak of chancroid in Orange County, California: descriptive epidemiology and disease-control measures.

From May 1981 through February 1983, greater than 1,700 patients were examined for genital ulcers at the Orange County Special Diseases Clinic in Santa Ana, California. Of these patients, 923 had either confirmed chancroid or genital ulcers of unknown etiology. Haemophilus ducreyi was recovered from lesions or inguinal buboes of 271 patients. In the previous year, no cases of chancroid were reported in this community. Men accounted for 266 (98%) of the confirmed cases; 95% of the men were Hispanic, and at least 53% had had sexual contact with a prostitute. All five culture-positive women were prostitutes. Antimicrobial sensitivity testing showed resistance to both sulfamethoxazole and tetracycline but susceptibility to erythromycin and to the combination trimethoprim-sulfamethoxazole. Treatment of patients with chancroid, their sex partners, and temporarily incarcerated prostitutes contributed to the successful control of this outbreak.

Pleural paragonimiasis in a Southeast Asia refugee.

We report a Laotian patient with pleural paragonimiasis who did not have the usual diagnostic triad for this parasitic disease. He did not have chronic hemoptysis (considered by many to be an "invariable" finding), there were no pulmonary infiltrations, and stool and sputum examinations did not yield Paragonimus ova. The diagnosis was made on the basis of ova found in the pleural fluid. Paragonimiasis pleural effusion did not resolve with bithionol, the drug of choice for pulmonary paragonimiasis, and, as a result, chest tube drainage was required. The difference between pleural paragonimiasis and pulmonary paragonimiasis is that the classic clinical presentation of the latter (hemoptysis, ova in sputum and stools, lung infiltration, etc.) requires an intrapulmonary location on the parasite. A search for ova in the pleural fluid may be the only diagnostic tool for patients suspected of pleural paragonimiasis. With the influx of Southeast Asia refugees, this case report may be of relevance to U.S. physicians involved in the care of patients in whom not all chronic pleuropulmonary diseases are tuberculous.

Comparative evaluation of New York City and modified Thayer-Martin media for isolation of Neisseria gonorrhoeae.

Commercially manufactured New York City (NYC) medium and modified Thayer-Martin (MTM) medium were compared for their ability to isolate Neisseria gonorrhoeae from clinical specimens. Twenty-seven public health laboratories throughout California evaluated 4,802 specimens collected from patients attending either sexually transmitted disease or family planning clinics. Total of 726 and 737 N. gonorrhoeae isolates were recovered from NYC and MTM medium, respectively. Although less contamination was noted on NYC medium, MTM medium was equivalent to commercially prepared NYC medium for the isolation of N. gonorrhoeae from clinical specimens.