Epidemiology and properties of heat-stable enterotoxin-producing Escherichia coli serotype O169:H41.

Enterotoxigenic Escherichia coli (ETEC) serotype O169:H41 organisms have become the most prevalent ETEC in Japan since the first outbreak in 1991. It was assumed that the outbreaks were due to clonal spread of this new ETEC serotype. The relationship of 32 strains isolated from 6 outbreaks were examined for biotype, antibiotic susceptibility, enterotoxigenicity, protein banding pattern, lipopolysaccharide banding pattern, plasmid analysis, and ribotyping. Further, the strains were examined by haemagglutination, surface hydrophobicity, and the ability to adhere to HEp-2 cells. The present study suggests that the outbreaks were caused by multiple clones of STp-producing O169:H41 since they showed differences in ribotype and outer membrane protein banding patterns. The strains did not agglutinate human or bovine red blood cells in a mannose-resistant manner. They adhered to HEp-2 cells in a manner resembling enteroaggregative E. coli. Five strains were examined by dot-blot tests for the colonization factor antigens CFA/I, CS1, CS2, CS3, CS4, CS5, CS6, CS7, PCFO159, PCFO166 and CFA/III. Although four strains expressed CS6, no structure for CS6 was identified. A strain that the anti-CS6 MAbs did not react with could adhere to HEp-2 cells in mannose resistant manner; thus, it is unlikely that CS6 play an important role in the adhesion to the cells. Electron microscopy studies of the O169:H41 strains suggested that curly fimbriae, a possible new colonization factor, may be playing an important role in the adhesion of the bacteria to HEp-2 cells. In conclusion, outbreaks due to ETEC O169:H41 were caused by multiple clones, and the strains should be examined in detail for a possible new colonization factor.

Application of ribotyping for differentiating aeromonads isolated from clinical and environmental sources.

We have investigated the usefulness of ribotyping for the differentiation of aeromonads isolated from five patients with gastroenteritis and from the source water, treatment plant, and distribution system of a small public water supply. Aeromonas hydrophila and Aeromonas caviae were isolated from fecal specimens preserved in Cary-Blair transport medium by using blood ampicillin agar or alkaline peptone water (pH 8.4) subcultured to blood ampicillin agar plates. A. hydrophila, Aeromonas sobria, and A. caviae were isolated from duplicate 100-ml water samples by the membrane filter technique by using ampicillin dextrin agar for quantitative determination of growth and alkaline peptone water enrichment for detection of the presence or absence of aeromonads below the detection limit of the membrane filter method. In addition, free chlorine residuals and pH values were determined for all water samples and heterotrophic plate counts and total and fecal coliform analyses were performed on them. Ribotyping patterns of aeromonads recovered from well 1, detention basin, sand filter, softener, and distribution samples were compared with those of the five clinical isolates. All patient strains were unique; however, identical ribotypes of A. hydrophila and A. sobria isolated from multiple sites in the water system indicated colonization of a well, sand filters, and the softener, with the potential for sporadic contamination of distribution water. Plant operational deficiencies were noted and corrected. Ribotyping can effectively differentiate otherwise indistinguishable strains of bacteria, thus providing a powerful tool for investigation of waterborne diseases and bacteriological problems within water treatment plants and distribution systems.

Media and methods for isolation of aeromonads from fecal specimens. A multilaboratory study.

An international multilaboratory study was conducted to establish the optimal combination of culture media, incubation time and temperature for recovery of aeromonads from stools using blood ampicillin (10 mg/l) agar (BAA), starch ampicillin (10 mg/l) agar (SAA), and cefsulodin irgasan novobiocin agar (CIN) with alkaline peptone water (APW) for enrichment. Optimal recovery of aeromonads (167/186) occurred using BAA (37 degrees C; 24 h) and CIN (25 degrees C; 48 h) with APW (25 degrees C; 24 h) subcultured to BAA (37 degrees C; 24 h) and CIN (25 degrees C; 48 h).

Penicillin resistant Neisseria gonorrhoeae in low prevalence areas: implications for cost-effective management.

Though ampicillin is no longer recommended as first-line therapy for infections caused by Neisseria gonorrhoeae, the cost and efficacy of this policy in low prevalence areas has not been investigated. The problem was highlighted by an outbreak of penicillin-resistant N. gonorrhoeae in an area where the proportion of resistance had previously been only 0.14%. A decision analysis was performed to determine the cost-effectiveness of beta-lactamase screening and alternative therapies for patients attending sexually transmitted diseases clinics. Empiric therapy with an inexpensive agent active against resistant strains, such as ciprofloxacin, was the most cost-effective approach and remained more cost-effective than alternative strategies whenever the proportion of resistant isolates exceeded 3%. Ceftriaxone was less cost-effective. In low prevalence areas, and in areas where the return rate of recalled patients is high, ampicillin therapy was cost-effective, but beta-lactamase screening should be performed routinely.

Evaluation of the Directigen 1,2,3 Group A Strep Test for diagnosis of streptococcal pharyngitis.

The Directigen 1,2,3 Group A Strep Test (DGAST; BBL Microbiology Systems, Cockeysville, Md.) was compared with conventional culture methods for the detection of group A streptococci. Among 327 children, the DGAST has a sensitivity of 75.0%, a specificity of 99.1%, and positive and negative predictive values of 97.5 and 89.3%, respectively, as compared with 48-h culture results. The lower sensitivity (60.0%) in 322 adults was related to the low incidence of group A streptococcal pharyngitis in that population (7.8%). The positive and negative predictive values for adults were 93.8 and 96.7%, respectively. Only 3 of 327 (0.9%) pediatric and 2 of 322 (0.6%) adult specimens yielded uninterpretable results in the DGAST.

Giardiasis in Iowa.

The author discusses transmission and case distribution of the parasitic disease giardiasis and why it should be made reportable.

Legionnaires' disease associated with a hospital water system. A five-year progress report on continuous hyperchlorination.

In 1981, sixteen cases of nosocomial legionellosis occurred among 456 patients admitted to a new hematology-oncology unit (35 per 1000 admissions). Monoclonal antibody typing and restriction endonuclease plasmid analysis identified a unique strain (09,04) of Legionella pneumophila serogroup 1 isolated from both patients and water outlets. Continuous hyperchlorination of the hot and cold water began in January 1982, and chlorine levels of 3 to 5 mg/L have been maintained most recently. Water samples have been consistently negative for Legionella for more than five years. Four sporadic cases of nosocomial legionellosis have occurred in the hematology-oncology unit during the same period (one per 1000 admissions) associated with a different strain of L pneumophila serogroup 1 (09,00). The environmental reservoir(s) of L pneumophila serogroup 1 in these cases has not been identified. Levels of trihalomethanes (potential carcinogens) were high (greater than 100 micrograms/L) when chlorine levels of hot water exceeded 4 mg/L. Some corrosion damage to the water distribution system has occurred: the average number of leaks per month increased steadily from zero in 1982 to 5.2 in 1986. The chlorinator installation costs were +75,800, and annual operation expenses were +12,500. Continuous hyperchlorination is a promising but still experimental technique for control of nosocomial legionellosis. In our experience, epidemic disease has been controlled, but sporadic cases have continued to occur.

Clinical significance of Aeromonas species isolated from patients with diarrhea.

A total of 248 strains of Aeromonas spp. were isolated from 3,334 human fecal specimens submitted to a state public health laboratory over a 2-year period to be cultured for enteric pathogens. Cary-Blair transport medium, blood ampicillin agar, and alkaline peptone water enrichment provided optimal recovery of Aeromonas spp. A questionnaire requesting clinical and epidemiological information was sent to physicians, who submitted stool samples for testing, with each laboratory report for 107 consecutive stool isolates of Aeromonas spp. The 56 questionnaires which were completed and returned were analyzed to determine the seasonal distribution of illness and the age and sex distribution of patients; characteristic symptoms; and predisposing factors for gastrointestinal disease caused by Aeromonas spp. It was concluded that some A. hydrophila, A. sobria, and A. caviae strains are capable of causing diarrhea and that antibiotic therapy and the drinking of untreated water are significant risk factors for susceptible hosts.

Evaluation of MUREX SUDS Toxo test.

The SUDS Toxo test (MUREX Corp., Norcross, Ga.) was compared with the indirect hemagglutination test (IHA) and the indirect fluorescent-antibody test (IFA) by examining 404 serum specimens, including 64 (15.8%) specimens with IFA titers of greater than or equal to 1:2. When SUDS was compared with IHA, sensitivity (96.4%), specificity (97.9%), and negative predictive value (99.4%) indicated that there were similar reactivities between the two tests. When an IFA titer of greater than or equal to 1:16 was considered significant and IHA and SUDS were compared with IFA, IHA was slightly less sensitive but had a higher positive predictive value than did SUDS; however, there was no statistical difference between the tests. When SUDS was compared with IFA, in which a titer of greater than or equal to 1:16 was considered significant, the high negative predictive value (100%), excellent sensitivity (100%) and specificity (98.3%), and ease of performance made SUDS an attractive alternative to IHA for screening single serum specimens for toxoplasmosis.

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.

Evaluation of the Bio-EnzaBead test for syphilis.

The sensitivity and specificity of the Bio-EnzaBead test for syphilis and the fluorescent treponemal antibody-absorption (FTA-ABS) test were determined by examining 262 serum samples, including 202 serum samples from patients with confirmed syphilis in various stages. Overall correlation with patient history was 95.8% with both tests. False-negative Bio-EnzaBead tests occurred in 9 of 86 (10.5%) cases of late-latent syphilis (greater than 2 years) and in 1 of 38 (2.6%) cases for which the stage of disease could not be determined. False-negative FTA-ABS tests occurred in 5 of 86 (5.8%) cases of late-latent syphilis (greater than 2 years) and in 2 of 38 (5.3%) cases for which the stage of disease could not be determined. One false-positive test occurred with Bio-EnzaBead, and the cause could not be determined. The reproducibility of the Bio-EnzaBead test was excellent when spectrophotometric readings were calibrated against either air or substrate blanks. The Bio-EnzaBead test for syphilis is a suitable alternative to the FTA-ABS test.

Evaluation of the hemagglutination treponemal test for syphilis.

The sensitivity and specificity of the hemagglutination treponemal test for syphilis (HATTS) was compared with the fluorescent treponemal antibody-absorption test (FTA-ABS) with 491 sera. Medical histories were obtained for 153 patients with seroreactivity in either treponemal test. Overall correlation with patient history was 96.7% for the FTA-ABS and 93.9% for the HATTS. False-negative HATTS occurred in primary, late-latent (greater than 2 years), and treated syphilis. The reproducibility of the HATTS and FTA-ABS is equivalent. HATTS is an acceptable treponemal confirmatory test for syphilis, but the FTA-ABS should be used to resolve diagnostic discrepancies.

Development and testing of a filter system for isolation of Giardia lamblia cysts from water.

An inexpensive, practical, and reliable method for isolation of Giardia lamblia cysts from potable and environmental water has been developed from commercially available components. This system was successfully used to isolate cysts from well water associated with a family outbreak of giardiasis.

Increased sensitivity of acid-fast smears.

Evaluation of the centrifuges used in the mycobacteriology laboratory indicated a failure to develop sufficient relative centrifugal force for optimal concentration of acid-fast bacilli. Retrospective analysis of 14,509 specimens received between 1 July 1973 and 30 June 1975 and sedimented at 1,260 x g relative centrifugal force revealed a positive smear rate of 1.8% and a positive culture rate of 7.1%, with a correlation between positive paired smears and cultures of 25.2%. After increasing the relative centrifugal force from 1,260 x g to 3,800 x g at maximum radius, the positive smear and culture rates were 9.6 and 11.6%, respectively, with a correlation between positive paired smears and cultures of 82.4%. The sensitivity of acid-fast smears is directly related to the relative centrifugal force achieved while concentrating the specimen by centrifugation.