Comparison of media and antibiotic supplements for isolation of Helicobacter pylori from gastric biopsies.

Our objective was to improve the media and the antibiotic supplements in order to increase the detection rate of Helicobacter pylori from gastric biopsy specimens. For the primary isolation of H. pylori taken from gastric biopsies, we compared the efficacy of two media: Columbia blood agar (CBA, Difco); brain heart infusion agar (BHIA, Difco); and two antibiotic supplement sets--a commercial antibiotic supplement (SR147, Oxoid) and an in-house antibiotic supplement (IHS). Gastric biopsies obtained from 210 patients were diagnosed by culture, rapid urease test (RUT) and histology. The true positive criteria were defined as a culture or both urease and histology tests being positive. The H. pylori infection rate was 44.3% (93/ 210). To compare the two media, a total of 106 gastric biopsies were plated on CBA or BHIA with 7% human blood, containing the antibiotic supplement SR147 and incubated under microaerophilic conditions. Of the 106 samples, 48 (45.3%) case of H. pylori infection, compared to the true positive criteria. The isolation rate using a combination of the two media was 83% (40/48). Of the 40 samples, 36 (90%) and 35 (87.5%) were positive on CBA and BHIA, respectively. To compare the two antibiotic supplement sets, a total of 104 gastric biopsies were plated on CBA, containing the commercial antibiotic supplement SR147 (5 mg/l trimethoprim, 10 mg/l vancomycin, 5 mg/l amphotericin B and 5 mg/l cefsulodin) or containing IHS (5 mg/l trimethoprim, 10 mg/l vancomycin, 2 mg/l amphotericin B and 2,500 U/l polymyxin B). Of the 104 samples, 45 (43.2%) case of H. pylori infection were found compared to the true positive criteria. The isolation rate using a combination of the two selective supplement sets was 82% (37/45). Of the 37 samples, 35 (95%) and 34 (92%) were positive with SR147 and IHS, respectively. Our study indicates that the combination of the two media and two antibiotic supplements is useful for maximum recovery of H. pylori isolated from gastric biopsies. CBA, and the commercial antibiotic supplement SR147 provided higher detection rates for H. pylori than BHIA, and IHS but the differences were not statistically significant.

Enteropathogenic bacteria and enterotoxin-producing Staphylococcus aureus isolated from ready-to-eat foods in Khon Kaen, Thailand.

The objective of this study was to investigate the microbiological quality of ready-to-eat food in the Municipality of Khon Kaen, Thailand. Four categories of 186 food samples were collected: (1) high heat food; (2) low heat food; (3) no heat food; and, 4) on-site prepared fruit juices and beverages. Of the food samples, 145 (78%) failed to meet acceptable microbiological standards, including fruit juice and beverages (100%), no heat food (91.7%), low heat food (81.7%) and high heat food (57.9%). The most frequent bacterial indexes indicating unacceptability were the most probable number (MPN) of coliforms (78%), the bacterial colony count (58%), and the MPN of E. coli (46%). Pathogenic bacteria were found in 6.5% of food samples. Salmonella, Vibrio cholerae non O1 and Aeromonas hydrophila were found in 4.3, 1.6 and 0.5% of the total food samples, respectively. The serovars of Salmonella found in food were S. Derby, S. Give, S. Krefield, S. Paratyphi B, S. Verchow, S. Lexington and S. Senftenberg. Staphylococcus aureus concentrations of >10(2) CFU/g and >10(5) CFU/g were found in 10.8% and 1.1% of the food samples. Enterotoxin types AB and A of S. aureus were found in 2.7% of the food samples. These results indicate that more than half of the ready-to-eat foods tested in Khon Kaen municipality did not meet microbiological national standards and many kinds of enteropathogenic bacteria were found, suggesting food stalls may be a source of foodborne disease.

Sensitivity and specificity of an in-house rapid urease test for detecting Helicobacter pylori infection on gastric biopsy.

We developed an in-house rapid urease test (iRUT) and evaluated the efficacy and the agreement of the iRUT and the cRUT compared with culture and histology for the detection of H. pylori infection. Five iRUT media were tested with H. pylori isolates and other bacteria. The most suitable iRUT medium was further evaluated for detection of H. pylori infection. Gastric biopsies from 120 patients were diagnosed by culture, iRUT, cRUT and histology. The results of the iRUT and cRUT were read at 30 minutes, 1 hour and up to 24 hours. A true positive result was either the culture or both the RUT (cRUT or iRUT) and the histological examination being positive. The sensitivity and specificity of the iRUT result at 30 minutes, 1 hour and up to 24 hours were 77.1% and 100%, 77.6% and 100%, and 94.1% and 94.2%, respectively. Values for the same parameters of cRUT were 87.5% and 100%, 89.8% and 100%, and 100% and 94.2%, respectively. The agreement between the iRUT and cRUT was very good (kappa values > or = 0.82). Our results indicate that the iRUT is a-sensitive, specific and cost effective test. It can be appropriately applied for detecting H. pylori infection in gastric biopsy specimens.

Characterization of diarrheagenic Escherichia coli isolated from food in Khon Kaen, Thailand.

Four categories of 186 ready-to-eat food samples in Khon Kaen municipality, Thailand, were collected and investigated for fecal contamination by enumeration of Escherichia coli using the most probable number (MPN) method. Then, the E. coli isolates were presumptively identified as diarrheagenic E. coil by agglutinating with polyvalent O-antisera and monovalent O-antisera commonly found in diarrheagenic strains and were subsequently investigated for the presence of the recognized virulence genes for enteroaggregative (EAEC), enteroinvasive (EIEC), enteropathogenic (EPEC), enterotoxigenic (ETEC), and shiga toxin-producing E. coli (STEC or EHEC) by multiplex PCR assays. All E, coli isolates were examined for antimicrobial susceptibilities by the agar disc diffusion method, and the results were compared with those obtained from clinical samples. The percentage of each type of food with E. coli, including no heat food, low heat food, high heat food, and fruit juices and beverages, was higher than accepted standards at 60.4, 46.5, 38.6 and 20%, respectively. Of 140 E. coli isolates obtained from food samples, 11 isolates (7.9%) agglutinated with 6 monovalent O-antisera, including one isolate each of O6, O8, O114 and O159, two isolates of O1, and five isolates of O157. None of the 11 isolates harbored the virulence genes for EPEC, ETEC, EAEC, EIEC and STEC. Although O157 E. coli isolates were found, the most frequent, E. coli O157:H7, was not found in this study. The astA gene, however, was found in 1 E. coli isolate that showed weakly positive agglutination against the polyvalent antisera. Approximately 50% of the 140 E. coli isolates were resistance to at least one antimicrobial agent. The resistant strains showed high resistance to tetracycline (43%), co-trimoxazole (36%), ampicillin (26%) and chloramphenicol (23%), respectively. The resistance of E. coli was high for nearly all antimicrobial agents, particularly ampicillin (76%), tetracycline (70%), co-trimoxazole (69%) and nalidixic acid (44%). The results show that nearly half of the ready-to-eat food samples evaluated in Khon Kaen Municipality had levels of E. coli higher than acceptable standards. Of the diarrheagenic E. coli classified by serogroup, almost none of the isolates had virulence genes. These results indicate the disadvantage of relying on serogrouping alone for the recognition of diarrheagenic E. coli. E. coli isolated from food may not be an enteropathogenic strain. We also found that E. coli antimicrobial resistant strains are widespread in both food and humans.