Detection and genotyping of Helicobacter pylori in saliva versus stool samples from asymptomatic individuals in Northeastern Thailand reveals intra-host tissue-specific H. pylori subtypes

BACKGROUND

Two-thirds of the world's population is thought to be infected by Helicobacter pylori. Although most people infected with H. pylori are asymptomatic, this pathogen is associated with several gastric pathologies including cancer. The risk factors for colonization are still unclear and the genetic diversity within individual hosts has never been clearly investigated.

RESULT

This study determined the prevalence of, and explored risk factors for, H. pylori infection directly from paired saliva (n = 110) and stool (n = 110) samples from asymptomatic persons in Northeast Thailand. Samples were subjected to indirect immunofluorescence assay (IFA), 16S rRNA-based real-time PCR and vacA-based semi-nested PCR. Partial vacA gene sequences of H. pylori were compared between saliva and stool samples. The overall prevalence of H. pylori infection in our asymptomatic study population was 64%. Age, gender, occupation and frequency of brushing teeth were not found to be associated with H. pylori colonization. The vacA gene was successfully sequenced from both saliva and stool samples of 12 individuals. For seven of these individuals, saliva and stool sequences fell into different clusters on a phylogenetic tree, indicating intra-host genetic variation of H. pylori.

CONCLUSION

This study reports a high prevalence of H. pylori infection in asymptomatic persons in this region of Thailand and demonstrates that genotypes (vacA gene sequences) of H. pylori may differ between the oral cavity and intestinal tract.

Antimicrobial resistance and genetic diversity of the SXT element in Vibrio cholerae from clinical and environmental water samples in northeastern Thailand

Multidrug resistance in V. cholerae has been increasing around the world including northeastern Thailand. The aquatic environment is a reservoir of V. cholerae and might be an important source of resistant strains. The aims of this study were to investigate the phylogenetic relationships of int_SXT gene sequences from 31 clinical and 14 environmental V. cholerae O1 and non-O1/non-O139 isolates and 11 sequences amplified directly from environmental water samples. We also amplified class 1 integrons, the SXT elements (targeting the int_SXT gene) and antimicrobial resistance genes directly from water samples. Phylogenetic analysis displayed two major distinct clusters (clusters 1 and 2). Most V. cholerae O1 (19/20, 95%) and non-O1/non-O139 isolates (8/11, 72.7%) from clinical sources, and all sequences obtained directly from water samples, belonged to cluster 1. Cluster 2 mostly comprised environmental non-O1/non-O139 isolates (10/12, 83.3%). We successfully amplified the SXT elements directly from17.5% of water samples. Associated resistance genes were also amplified as follows: sul2 (41.3% of water samples), dfrA1 (60%), dfr18 (33.8%), strB (70%) and tetA (2.5%). Class 1 integrons were not found in water samples, indicating that the SXT element was the major contributor of multidrug resistance determinants in this region. The SXT element and antimicrobial resistance genes could be transferred from clinical V. cholerae O1 to environmental V. cholerae non-O1/non-O139 was demonstrated by conjugation experiment. These findings indicate that there may have been cross dissemination and horizontal gene transfer (HGT) of the SXT element harbored by V. cholerae O1 and non-O1/non-O139 strains isolated from clinical and environmental water sources. Environmental water might be an important source of antimicrobial resistance genes in V. cholerae in this region. Direct detection of antimicrobial resistance genes in water samples can be used for monitoring the spread of such genes in the ecosystem.

Genetic characterization of Helicobacter pylori vacA and cagA genes in Thai gastro-duodenal and hepatobiliary patients

INTRODUCTION

H. pylori has been detected in patients with hepatobiliary diseases. It is currently unclear whether the H. pylori detected in hepatobiliary patients are genetically similar to those in gastro-duodenal patients. The aim of this study was to determine H. pylori vacA and cagA genotypes in Thai patients with gastro-duodenal and hepatobiliary diseases.

METHODOLOGY

H. pylori DNA was extracted from samples from gastric biopsies of gastro-duodenal patients (n=100) and from bile samples of hepatobiliary patients (n=80). The vacA and cagA genotypes were performed via polymerase chain reaction (PCR) followed by DNA sequencing.

RESULTS

The vacA m1 was found in Thai hepatobiliary patients (90%) at a higher rate compared with gastro-duodenal patients (50%).The combined vacA s1a+c/m1 were mostly found in Thai gastro-duodenal and hepatobiliary patients. The cagA gene was detected in 94% of patients with gastro-duodenal diseases compared with 28.8% in those with hepatobiliary diseases (p<0.05). On the other hand, the Western type cagA was more prominent among hepatobiliary patients (100%) than gastro-duodenal patients (57.4%), and this type was grouped into same cluster with Thai gastro-duodenal patients via phylogenetic analysis.

CONCLUSIONS

Based on vacA and cagA analysis, we conclude that infection with H. pylori in gastro-duodenal and hepatobiliary patients may be caused by the different H. pylori strains.

Chronic Opisthorchis viverrini Infection Changes the Liver Microbiome and Promotes Helicobacter Growth

Adults of Opisthorchis viverrini reside in the biliary system, inducing inflammation of bile ducts and cholangitis, leading to hepatobiliary disease (HBD) including cholangiocarcinoma. O. viverrini infection also has major implications for the bacterial community in bile ducts and liver. To investigate this in chronic O. viverrini infection (≥ 8 months p.i.), bacterial genomic DNA from livers of hamsters and from worms was investigated using culture techniques, PCR for Helicobacter spp. and high-throughput next-generation sequencing targeting the V3-V4 hypervariable regions of prokaryotic 16S rRNA gene. Of a total of 855,046 DNA sequence reads, 417,953 were useable after filtering. Metagenomic analyses assigned these to 93 operational taxonomic units (OTUs) consisting of 80 OTUs of bacteria, including 6 phyla and 42 genera. In the chronic O. viverrini-infected group, bacterial community composition and diversity were significantly increased compared to controls. Sequences of Fusobacterium spp. were the most common (13.81%), followed by Streptococcus luteciae (10.76%), Escherichia coli (10.18%), and Bifidobacterium spp. (0.58%). In addition, Helicobacter pylori (0.17% of sequences) was also identified in the liver of chronic O. viverrini infections, but not in normal liver. The presence of H. pylori was confirmed by PCR and by use of an antibody against bacterial antigen, supporting the metagenomics data. The identities of bacteria cultured for enrichment suggested that chronic O. viverrini infection changes the liver microbiome and promotes Helicobacter spp. growth. There may be synergy between O. viverrini and the liver microbiome in enhancing immune response-mediated hepatobiliary diseases.

DETECTION OF HELICOBACTER PYLORI AND VIRULENCE-ASSOCIATED GENES IN SALIVA SAMPLES OF ASYMPTOMATIC PERSONS IN NORTHEAST THAILAND

The aims of the study were to develop nested-PCR (targeting vacA and cagA), SYBR green quantitative PCR (targeting 16S rDNA) tests and compared them with indirect fluorescent-monoclonal antibody (IFA) method for determination of the prevalence of Helicobacter pylori in 118 saliva samples from asymptomatic individuals in Khon Kaen, Thailand. Detection limit of both PCR-based assays was one cell. Prevalence of H. pylori in saliva samples was 55% based on the criterion of positivity of IFA test and one of the PCR-based methods or positivity of both PCR assays. Forty-nine percent of H. pylori detected carried cagA, encoding a cytotoxin associated with severe clinical outcomes. These results imply that the mouth may be an important reservoir for H. pylori, with nearly 50% of the virulent type that could possibly lead to gastroduodenal disease.

SXT ELEMENT, CLASS 1 INTEGRON AND MULTIDRUG-RESISTANCE GENES OF VIBRIO CHOLERAE ISOLATED FROM CLINICAL AND ENVIRONMENTAL SOURCES IN NORTHEAST THAILAND

Emergence of multiple drug resistance in Vibrio cholerae has been increasing around the world including Northeast Thailand. In this study, 92 isolates of V. cholerae (50 O1 and 42 non-O1/non-O139 isolates) from clinical and environmental sources in Northeast Thailand were randomly selected and investigated for the presence of SXT element, class 1 integron and antimicrobial resistance genes. Genotypic-phenotypic concordance of antimicrobial resistance was also determined. Using PCR-based assays, 79% of V. cholerae isolates were positive for SXT element, whereas only 1% was positive for class 1 integron. SXT element harbored antimicrobial resistance genes, dfrA1 or dfr18, floR, strB, sul2, and tetA. Overall phenotypic-genotypic concordance of antimicrobial resistance was 78%, with highest and lowest value being for trimethoprim (83%) and chloramphenicol (70%), respectively. Ninety-two percent of V. cholerae O1 strains isolated from clinical sources harbored both dfrA1 (O1-specific trimethoprim resistance gene) and dfr18 (non-O1-specific trimethoprim resistance gene), whereas only 5% of V. cholerae non-O1/non-O139 strains harbored both genes. All V. cholerae O1 isolated from environmental source harbored dfr18 but 48% of V. cholerae non-O1/non-O139 harbored dfrA1. This study indicates that SXT element was the main contributor to the circulation of multiple-drug resistance determinants in V. cholerae strains in Northeast Thailand and that genetic exchange of SXT element can occur in both V. cholerae O1 and non-O1/non-O139 strains from clinical and environmental sources.

The carcinogenic liver fluke Opisthorchis viverrini is a reservoir for species of Helicobacter

There has been a strong, positive correlation between opisthorchiasis-associated cholangiocarcinoma and infection with Helicobacter. Here a rodent model of human infection with Opisthorchis viverrini was utilized to further investigate relationships of apparent co-infections with O. viverrini and H. pylori. A total of 150 hamsters were assigned to five groups: i) Control hamsters not infected with O. viverrini; ii) O. viverrini-infected hamsters; iii) non-O. viverrini infected hamsters treated with antibiotics (ABx); iv) O. viverrini-infected hamsters treated with ABx; and v) O. viverrini-infected hamsters treated both with ABx and praziquantel (PZQ). Stomach, gallbladder, liver, colonic tissue, colorectal feces and O. viverrini worms were collected and the presence of species of Helicobacter determined by PCR-based approaches. In addition, O. viverrini worms were cultured in vitro with and without ABx for four weeks, after which the presence of Helicobacter spp. was determined. In situ localization of H. pylori and Helicobacter-like species was performed using a combination of histochemistry and immunohistochemistry. The prevalence of H. pylori infection in O. viverrini-infected hamsters was significantly higher than that of O. viverrini-uninfected hamsters (p≤0.001). Interestingly, O. viverrini-infected hamsters treated with ABx and PZQ (to remove the flukes) had a significantly lower frequency of H. pylori than either O. viverrini- infected hamsters treated only with ABx or O. viverrini-infected hamsters, respectively (p≤0.001). Quantitative RT-PCR strongly confirmed the correlation between intensity H. pylori infection and the presence of liver fluke infection. In vitro, H. pylori could be detected in the O. viverrini worms cultured with ABx over four weeks. In situ localization revealed H. pylori and other Helicobacter-like bacteria in worm gut. The findings indicate that the liver fluke O. viverrini in the biliary tree of the hamsters harbors H. pylori and Helicobacter-like bacteria. Accordingly, the association between O. viverrini and H. pylori may be an obligatory mutualism.

PHENOTYPIC AND GENOTYPIC DETECTION OF ENTEROTOXINS, TOXIC SHOCK SYNDROME TOXIN-1 AND OF METHICILLIN RESISTANCE IN STAPHYLOCOCCUS AUREUS ISOLATED FROM RETAIL READY-TO-EAT FOODS IN NORTHEASTERN THAILAND

Toxigenic Staphylococcus aureus contamination of ready-to-eat (RTE) foods is a leading cause of foodborne illness in Thailand. From 151 RTE food samples randomly collected from food vendors and food shops in Khon Kaen municipality, Thailand and after culture-based identification of S. aureus isolates, pentaplex PCR was used for simultaneous detection of super-antigenic toxin (SE) genes (sea, seb, sec, sed and tst-1) and presence of their toxins by reversed passive latex agglutination assay. S. aureus was identified in 57 isolates, of which 60% and 25% was positive for presence of super-antigenic toxin genes and toxins, respectively; and among the former isolates sea was the most common (46%), as well as its product (SEA) (14%) among the latter group. Methicillin resistance S. aureus mecA was not found in any of the isolates using both PCR and disk diffusion methods. These results showed that pentaplex PCR is a useful tool for detection of SE-encoding genes in S. aureus isolates from RTE food.

GENOTYPE AND DRUG RESISTANCE OF CLINICAL AND ENVIRONMENTAL VIBRIO CHOLERAE NON-O1/NON-O139 IN NORTHEASTERN THAILAND

A total of 124 V cholerae non-O1/non-O139 isolates were collected in Khon Kaen, Thailand from diarrheal patients, asymptomatic carriers and environmental water. The presence of virulence-associated and regulatory genes including ctxA, tcpA, zot, ace, ompU, stn, hlyA and toxR) were examined using multiplex PCR. The genomic diversity of the various V. cholerae isolates were differentiated using the random amplified polymorphic DNA (RAPD) method. Antimicrobial susceptibility was tested using disk diffusion. All of V. cholerae non-O/non-O139 isolates carried hlyA and toxR and none carried ctxA and tcpA. The zot, ace and both genes together were found in 1.6%, 4.7% and 4.7% of 64 clinical V. cholerae non-O1 isolates, respectively, while the environmental ones did not. The stn gene was found in 3.1% (2/64) of the clinical and 3.3% (2/60) of the environmental isolates. The RAPD patterns were differentiated into 45 types (A to 2S). RAPD type A (32.3%) was the most frequently found in both clinical and environmental V cholerae non-O1 strains (34.4% and 30.0%, respectively); indicating that there was a clonal relationship between some clinical and environmental isolates whereas almost all of the environmental isolates belonged to different clones. All strains were sensitive to ciprofloxacin and norfloxacin. The environmental isolates (30%) were more resistant than the clinical ones (21.9%). Resistance to sulfamethoxazole/trimethoprim and tetracycline among the clinical isolates occurred in 9.4% (6/64) in 2007, during which period the prevalence of V cholerae O1 increased. We conclude that V. cholerae non-O1/non-O139 from the aquatic environment are potentially pathogenic and this same aquatic environment may be a source of antimicrobial resistance in V. cholerae.

ROLE OF HLYA-POSITIVE VIBRIO CHOLERAE NON-O1/NON-O139 ON APOPTOSIS AND CYTOTOXICITY IN A CHINESE HAMSTER OVARY CELL LINE

Vibrio cholerae non-O1/non-O139 is capable of producing sporadic outbreaks of cholera-like diarrhea; however, the pathogenic mechanisms of this bacterium remain unclear. The objectives of this study were to: 1) compare the apoptosis induction and cytotoxicity between hlyA-positive and hlyA-negative strains of V. cholerae non-O1/non-O139; 2) clarify the molecular mechanisms by which these strains induce apoptosis; and 3) compare clinical and environmental V. cholerae non-O1/non-O139 isolates with respect to cytotoxicity and ability to induce apoptosis. Using cytotoxicity and apoptosis assays, it was shown that hlyA-positive strains of V. cholerae non-O1/non-O139 had significantly higher cytotoxic activity (70.6%) and levels of apoptosis induction (59.6%) than hlyA- negative strains (37.0% and 37.5%, respectively). Western blot analyses revealed that hlyA-positive strains had significantly increased expression of Bax; active caspase-3 and -9; and significantly decreased expression of NF-κB and Bcl-2 relative to hlyA-negative strains. Expression of BID did not differ significantly between hlyA-positive and negative strains. The truncated BID was not found, indicating that V. cholerae non-O1/non-O139 induces apoptosis through a mitochondria- dependent apoptosis pathway and not an extrinsic pathway. V. cholerae non-O1/ non-O139 isolated from clinical sources exhibited significantly higher cytotoxic activity (79%) and levels of apoptosis induction (65.2%) than bacteria isolated from environmental sources (63% and 54.6%, respectively), suggesting that the clini- cal isolates may have other virulence-associated genes besides hlyA. Our results indicate that hlyA products play a role in cytotoxicity and apoptosis induction and that a mitochondria-dependent apoptosis pathway is involved.

Synergistic effects of isomorellin and forbesione with doxorubicin on apoptosis induction in human cholangiocarcinoma cell lines

BACKGROUND

Chemotherapy for advanced cholangiocarcinoma (CCA) is largely ineffective, but innovative combinations of chemotherapeutic agents and natural compounds represent a promising strategy. In our previous studies, isomorellin and forbesione, caged xanthones isolated from Garcinia hanburyi, were found to induce cell cycle arrest and apoptosis in CCA cell lines. The subject of our inquiry is the synergistic effect(s) of these caged xanthones with doxorubicin on growth inhibition and apoptosis induction in human CCA cell lines.

METHODS

KKU-100, KKU-M139 and KKU-M156 cell lines and Chang cells were treated with either isomorellin or forbesione alone or in combination with doxorubicin. Cell viability was determined using the sulforhodamine B assay. The combined effects of plant compounds with doxorubicin were analyzed using the isobologram and combination index method of Chou-Talalay. Apoptosis was determined by ethidium bromide/acridine orange staining. Protein expressions were determined by Western blot analysis.

RESULTS

Isomorellin or forbesione alone inhibited the growth of these CCA cell lines in a dose-dependent manner and showed selective cytotoxicity against CCA cells but not against Chang cells. Isomorellin/doxorubicin combination showed a synergistic growth inhibitory effect on KKU-M139 and KKU-M156 cells, while the forbesione/doxorubicin combination showed a synergistic growth inhibitory effect on KKU-100 and KKU-M139 cells. The percentages of apoptotic cells were significantly higher in the combined treatments than in the respective single drug treatments. The combined treatments strongly enhanced the expression of Bax/Bcl-2, activated caspase-9 and caspase-3, while suppressing the expression of survivin, procaspase-9 and procaspase-3, compared with single drug treatments. The degree of suppression of NF-κB activation mediated by a decrease in the expression of NF-κB/p65, a reduction of the pIκB-α level and an increase in the IκB-α protein level, was significantly higher in the combined treatment groups than in the single drug treatment groups. The degree of suppression of MRP1 protein expression was also significantly higher in the combined treatment than in the single drug treatment groups.

CONCLUSION

The combinations of isomorellin/doxorubicin and forbesione/doxorubicin showed significant synergistic effects on the growth inhibition and apoptosis induction in KKU-M156 and KKU-100 cells. Caged xanthones may be useful adjunct treatments with chemotherapy for Opisthorchis viverrini (OV)-associated CCA.

Triplex reverse transcription-PCR for detecting viable toxigenic Vibrio cholerae in water samples in Thailand

Abstract. Detection of toxigenic Vibrio cholerae O1/O139 in aquatic environment is difficult to achieve using the culture method. For direct detection of viable toxigenic V. cholerae in aquatic environment, we developed a triplex reverse transcription (RT)-PCR, targeting genes for the outer membrane protein (ompW), cholera toxin A (ctxA) and toxin-coregulated pilli (tcpA) and compared the assay with the culture method. After enrichment of the bacteria-containing filters in alkaline peptone water for 6 hours, the sensitivity of triplex RT-PCR for detecting V. cholerae was 7 cfu/ml. Of the 80 environmental water samples collected from various regions in Northeast Thailand, triplex RT-PCR detected 15 toxigenic and 20 non-toxigenic V. cholerae, whereas the culture method detected only 3 toxigenic V. cholerae--containing water samples. These results show that this triplex RT-PCR method could be used as an alternative tool for rapid and sensitive identification of viable toxigenic V cholerae in environmental water samples.

Molecular analysis of Vibrio vulnificus isolated from cockles and patients in Thailand

Vibrio vulnificus can cause septicemia, wound infection and gastroenteritis. The most severe infections are related to consumption of raw or undercooked seafood. Virulence genes, biomarkers, antimicrobial resistance, and genetic relationships among V vulnificus isolated from clinical and environmental sources in Thailand have not hitherto been investigated. ViuB encoding vulnibactin siderophore was detected in 33% and 50% of clinical and environmental (cockle) V. vulnificus isolates, respectively, and capsular polysaccharide allele 1 in 67% and 75% of clinical and environmental isolates, respectively. Analysis of the 16 S rDNA gene revealed that type B was the most frequent in both clinical and environmental isolates (67%) whereas the non type-able (30%) was detected only in environmental isolates. The virulence-correlated gene (vcg) with both type C and E together was the most frequently found among the clinical (67%) and environmental (72%) isolates. Pulsed-field gel electrophoresis differentiated V vulnificus into 2 clusters; most cockle samples (83%) and all clinical isolates grouped into cluster II, indicating a possible clonal relationship between V. vulnificus isolated from patients and cockles. Only 20% of environmental isolates were resistant to ampicillin. These studies suggest that V vulnificus isolated from cockles has virulence genes similar to those in clinical isolates and thus may have the potential of causing disease.

Helicobacter pylori cag pathogenicity island (cagPAI) involved in bacterial internalization and IL-8 induced responses via NOD1- and MyD88-dependent mechanisms in human biliary epithelial cells

Helicobacter pylori infection has been proposed to be associated with various diseases of the hepatobiliary tract, including cancer of the bile duct epithelial cells (cholangiocarcinoma, CCA). The ability of H. pylori bacteria to cause pathogenic effects in these cells has, however, yet to be investigated. Given that the cag pathogenicity island (cagPAI) is required for H. pylori pathogenesis in gastric epithelial cells, we investigated wild-type and cag mutant strains for their ability to adhere, be internalized and induce pro-inflammatory responses in two bile duct epithelial cell lines derived from cases of CCA. The findings from these experiments were compared to results obtained with the well-characterized AGS gastric cancer cell line. We showed that the cagPAI encodes factors involved in H. pylori internalization in CCA cells, but not for adhesion to these cells. Consistent with previous studies in hepatocytes, actin polymerization and α5β1 integrin may be involved in H. pylori internalization in CCA cells. As for AGS cells, we observed significantly reduced levels of NF-κB activation and IL-8 production in CCA cells stimulated with either cagA, cagL or cagPAI bacteria, when compared with wild-type bacteria. Importantly, these IL-8 responses could be inhibited via either pre-treatment of cells with antibodies to α5β1 integrins, or via siRNA-mediated knockdown of the innate immune signaling molecules, nucleotide oligomerization domain 1 (NOD1) and myeloid differentiation response gene 88 (MyD88). Taken together, the data demonstrate that the cagPAI is critical for H. pylori pathogenesis in bile duct cells, thus providing a potential causal link for H. pylori in biliary tract disease.

Duplex PCR for detection of Salmonella and Shigella spp in cockle samples

Salmonella and Shigella spp are important causative agents of foodborne diseases. A sensitive, specific and rapid method is essential for detection of these pathogens. In this study, a duplex PCR method was developed for simultaneous detection of Salmonella and Shigella spp in cockle samples and compared with the traditional culture method. Enrichment broths for Salmonella spp recovery were also compared. Sensitivity of the duplex PCR for simultaneous detection of Salmonella and Shigella spp from pure culture was 10(3) CFU/ml (40 CFU/PCR reaction), and that of sterile cockle samples spiked with these two pathogens was 1 CFU/10 g of cockle tissue after 9 hours enrichment [3 hours in buffered peptone water (BPW), followed by 6 hours in Rappaport Vasiliadis (RV) broth or tetrathionate (TT) broth for Salmonella spp and 6 hours enrichment in Shigella broth (SB) for Shigella spp]. There was no significant difference in detection sensitivity between enrichment in RV and TT broths. Salmonella spp detected in cockles in Khon Kaen, Thailand by duplex PCR and culture method was 17% and 13%, respectively but Shigella spp was not detected. The duplex PCR technique developed for simultaneous detection of Salmonella and Shigella spp in cockle samples was highly sensitive, specific and rapid and could serve as a suitable method for food safety assessment.

Multiplex PCR for detection of superantigenic toxin genes in methicillin-sensitive and methicillin-resistant Staphylococcus aureus isolated from patients and carriers of a hospital in northeast Thailand

The aims of this study were to develop multiplex PCR for simultaneous detection of five superantigenic toxin genes (sea, seb, sec, sed and tst-1) in Staphylococcus aureus isolated from 149 clinical samples and nasal swabs from 201 healthy subjects in Thailand, and to compare prevalence and expression of those genes between methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA). The sensitivity of multiplex PCR was 10(3) CFU/ml (60 CFU/PCR reaction) for DNA templates extracted by both boiling and extraction methods. S. aureus strains from patients (65%) harbored more superantigenic toxin genes than healthy subjects (54%). MRSA (80%) isolated from patients harbored more superantigenic toxin genes than MSSA (52%). Sea was the most frequently found gene in S. aureus strains from patients and carriers. MRSAisolates harbored sea and produced SEA more frequently than MSSA isolates (p <0.05) and MRSA isolates (59%) from blood samples consisted of a higher number of superantigenic toxin producers than MSSA (9%) (p < 0.05). More S. aureus strains isolated from patients with severe septicemia contained superantigenic toxin genes (94%) and produced toxins (82%) than those from non-severe patients (64% and 57%, respectively). The multiplex PCR method described here offers a reliable tool for simultaneous detection of various staphylococcal toxin genes.

Application of tetraplex PCR for detection of Vibrio cholerae, V. parahaemolyticus, V. vulnificus and V. mimicus in cockle

A tetraplex PCR method was developed for simultaneous detection of Vibrio cholerae, V. parahaemolyticus, V. vulnificus and V. mimicus in cockle samples in comparison with conventional culture method. Specific primers targeting ompW of V. cholerae, tl of V. parahaemolyticus, hsp60 of V. vulnificus and sodB of V. mimicus were employed in the same PCR. Detection limit of the tetraplex PCR assay was 104 cfu/ml (400 cfu/PCR reaction) for pure cultures of all four species of Vibrio. In Vibrio spiked cockle samples, the limit of detection after 6 hours enrichment in alkaline peptone water was 1 cfu/10 g of cockle tissue for three Vibrio spp, except for V. mimicus that was 102 cfu/10 g of cockle tissue. When the tetraplex PCR and culture methods were applied to 100 cockle samples, V. parahaemolyticus, V. vulnificus, V. cholerae and V. mimicus were detected in 100, 98, 80 and 9% of the samples by tetraplex PCR and in 76, 42, 0 and 0% by the culture method, respectively. This developed tetraplex PCR method should be suitable for simultaneous and rapid detection of Vibrio species in food samples and for food safety assessment.

Drug response and genetic properties of Vibrio cholerae associated with endemic cholera in north-eastern Thailand, 2003-2011

Cholera, caused by Vibrio cholerae, results in significant morbidity and mortality worldwide, including Thailand. Representative V. cholerae strains associated with endemic cholera (n = 32), including strains (n = 3) from surface water sources, in Khon Kaen, Thailand (2003-2011), were subjected to microbiological, molecular and phylogenetic analyses. According to phenotypic and related genetic data, all tested V. cholerae strains belonged to serogroup O1, biotype El Tor (ET), Inaba (IN) or Ogawa (OG). All of the strains were sensitive to gentamicin and ciprofloxacin, while multidrug-resistant (MDR) strains showing resistance to erythromycin, tetracycline, trimethoprim/sulfamethoxazole and ampicillin were predominant in 2007. V. cholerae strains isolated before and after 2007 were non-MDR. All except six diarrhoeal strains possessed ctxA and ctxB genes and were toxigenic altered ET, confirmed by MAMA-PCR and DNA sequencing. Year-wise data revealed that V. cholerae INET strains isolated between 2003 and 2004, plus one strain isolated in 2007, lacked the RS1 sequence (rstC) and toxin-linked cryptic plasmid (TLC)-specific genetic marker, but possessed CTX(CL) prophage genes ctxB(CL) and rstR(CL). A sharp genetic transition was noted, namely the majority of V. cholerae strains in 2007 and all in 2010 and 2011 were not repressor genotype rstR(CL) but instead were rstR(ET), and all ctx(+) strains possessed RS1 and TLC-specific genetic markers. DNA sequencing data revealed that strains isolated since 2007 had a mutation in the tcpA gene at amino acid position 64 (N→S). Four clonal types, mostly of environmental origin, including subtypes, reflected genetic diversity, while distinct signatures were observed for clonally related, altered ET from Thailand, Vietnam and Bangladesh, confirmed by distinct subclustering patterns observed in the PFGE (NotI)-based dendrogram, suggesting that endemic cholera is caused by V. cholerae indigenous to Khon Kaen.

Molecular analysis and antimicrobial resistance of Vibrio cholerae O1 in northeastern Thailand

A total of 84 clinical Vibrio cholerae O1 isolates were collected from Khon Kaen (KK), Udon Thani (UT), Loei (LI), and Nong Khai (NK), northeastern Thailand during cholera outbreaks in 2007 and 2008. The majority of V. cholerae O1 strains carried nearly all the virulence-associated genes (ctxA, zot, and ace) except for four isolates and one isolate from UT and NK, respectively, which carried only tcpA, ompU, hlyA and toxR. None of the V. cholerae O1 strains carried sto. Pulsed field gel-electrophoresis (PFGE) profiling of 16 randomly chosen isolates showed the same PFGE pattern, except for one NK isolate, which was sensitive to all seven antibiotics used in the antimicrobial susceptibility tests. The tests revealed that multi-drug resistance to tetracycline and co-trimoxazole were present in KK strains (92%), followed by LI (75%) and UT (52%) strains. All strains were sensitive to norfloxacin but intermediate resistance to ciprofloxacin was found in a single strain from KK and LI. Differences in antimicrobial resistance among V. cholerae strains with the same PFGE pattern reflect differences in the antimicrobial agents used in each area of northeastern Thailand.

Molecular analysis of Helicobacter pylori virulent-associated genes in hepatobiliary patients

OBJECTIVES

The Helicobacter pylori virulence-associated genes in hepatobiliary patients, including vacA, iceA, babA2, cagA and cagE, have not been reported. The aim of this study was to investigate these genes and the association of those and the clinical outcomes in hepatobiliary diseases.

METHODS

Eighty H. pylori-PCR-positive cases were obtained from hepatobiliary patients, representing both cholangiocarcinoma (CCA) (n= 58) and cholelithiasis (n= 22). The diversity of virulence genes was examined by polymerase chain reaction and DNA sequencing. Phylogenetic analysis of cagA was determined using the maximum parsimony method.

RESULTS

The vacAs1a + c/m1, iceA1 and babA2 genes were the most predominant genotypes in both CCA and cholelithiasis patients. The cagA and cagE genes were found significantly more frequently in patients with CCA than those with cholelithiasis (P < 0.05). The cagA positive samples were the Western-type cagA and showed that almost all of the detected sequences in Thai hepatobiliary and Thai gastric cancer patients were classified in the same cluster but separated from the cluster of Japan and other countries.

CONCLUSIONS

The cagA and cagE genes may be associated in the pathogenesis of hepatobiliary diseases, especially of CCA. Besides the bacterial variation, other host factors may be involved in the pathogenesis of hepatobiliary cancer.

PCR-RFLP and antimicrobial susceptibility profiles of Helicobacter pylori isolated from antrum and corpus of dyspeptic patients in Thailand

The study determined the genetic heterogeneity of Helicobacter pylori isolates from antrum and corpus of the same dyspeptic patients in a Thai population and determined the relationship between the antimicrobial susceptibility (AS) profile (antibiogram) and PCR-restriction fragment length polymorphism (PCR-RFLP) pattern. One hundred and nineteen H. pylori isolates comprising 7 single and 56 paired antrum and corpus isolates obtained by gastric biopsy from 160 dyspeptic patients were analyzed. For PCR-RFLP, the 820 bp amplicon of ureC was digested with Sau3AI and HhaI, which revealed 16 (A-Q) and 19 (a- s) different PCR-RFLP patterns after Sau3AI and HhaI digestion, respectively. Combination of the restriction enzyme digestion patterns resulted in 35 distinct RFLP types. Among the 56 paired isolates, 47 were infected with H. pylori having the same AS and PCR-RFLP profiles, 7 with different AS profiles but the same PCR-RFLP profiles and 2 with different PCR-RFLP profiles but the same AS profiles. No patient was infected with H. pylori different in both PCR-RFLP and AS profiles. The results indicate that the majority of the paired H. pylori isolates displayed identical AS profile and PCR-RFLP patterns suggesting that most patients were infected with a single strain. Some patients could have been infected with single strains that were different in the AS profiles.

Helicobacter pylori in Thai patients with cholangiocarcinoma and its association with biliary inflammation and proliferation

OBJECTIVES

To investigate whether Helicobacter spp. infection and the cagA of H. pylori are associated with hepatobiliary pathology, specifically biliary inflammation, cell proliferation and cholangiocarcinoma (CCA).

METHODS

Helicobacter species including H. pylori, H. bilis and H. hepaticus were detected in the specimens using the polymerase chain reaction (PCR). Biliary inflammation of the liver and gallbladders was semi-quantitatively graded on hematoxylin and eosin (H&E)-stained slides. Biliary proliferation was evaluated by immunohistochemistry using the Ki-67-labelling index.

RESULTS

Helicobacter pylori was found in 66.7%, 41.5% and 25.0% of the patients in the CCA, cholelithiasis and control groups (P < 0.05), respectively. By comparison, H. bilis was found in 14.9% and 9.4% of the patients with CCA and cholelithiasis, respectively (P > 0.05), and was absent in the control group. The cagA gene of H. pylori was detected in 36.2% and 9.1% of the patients with CCA and cholelithiasis, respectively (P < 0.05). Among patients with CCA, cell inflammation and proliferation in the liver and gallbladder were significantly higher among those DNA H. pylori positive than negative.

CONCLUSIONS

The present findings suggest that H. pylori, especially the cagA-positive strains, may be involved in the pathogenesis of hepatobiliary diseases, especially CCA through enhanced biliary cell inflammation and proliferation.

Helicobacter pylori in Thai patients with cholangiocarcinoma and its association with biliary inflammation and proliferation

OBJECTIVES

To investigate whether Helicobacter spp. infection and the cagA of H. pylori are associated with hepatobiliary pathology, specifically biliary inflammation, cell proliferation and cholangiocarcinoma (CCA).

METHODS

Helicobacter species including H. pylori, H. bilis and H. hepaticus were detected in the specimens using the polymerase chain reaction (PCR). Biliary inflammation of the liver and gallbladders was semi-quantitatively graded on hematoxylin and eosin (H&E)-stained slides. Biliary proliferation was evaluated by immunohistochemistry using the Ki-67-labelling index.

RESULTS

Helicobacter pylori was found in 66.7%, 41.5% and 25.0% of the patients in the CCA, cholelithiasis and control groups (P < 0.05), respectively. By comparison, H. bilis was found in 14.9% and 9.4% of the patients with CCA and cholelithiasis, respectively (P > 0.05), and was absent in the control group. The cagA gene of H. pylori was detected in 36.2% and 9.1% of the patients with CCA and cholelithiasis, respectively (P < 0.05). Among patients with CCA, cell inflammation and proliferation in the liver and gallbladder were significantly higher among those DNA H. pylori positive than negative.

CONCLUSIONS

The present findings suggest that H. pylori, especially the cagA-positive strains, may be involved in the pathogenesis of hepatobiliary diseases, especially CCA through enhanced biliary cell inflammation and proliferation.

Prevalence of cagA EPIYA motifs in Helicobacter pylori among dyspeptic patients in northeast Thailand

The aims of this study were to determine the prevalence of cagA type in Helicobacter pylori isolated from dyspeptic patients in northeastern Thailand and to determine whether the pattern of cagA EPIYA motifs were associated with clinical outcomes. One hundred and forty-seven H. pylori-infected dyspeptic patients were enrolled, of whom 68 had non-ulcer dyspepsia (NUD), 57 peptic ulcer disease (PUD), 18 gastric cancer (GCA), and 4 other gastroduodenal diseases. PCR and DNA sequence analysis were used to determine the cagA genotype and the pattern of EPIYA motifs. cagA-positive H. pylori were identified in 138 (94%) of H. pylori-infected dyspeptic patients of whom 75 (54%) were of the Western-type, 44 (32%) the East Asian type and 19 (14%) of the other types. The Western type is significantly found in PUD patients (p = 0.0175). The majority of cagA EPIYA was EPIYA-ABC (43%) and EPIYA-ABD (28%). There is no significant correlation between the increase in number of EPIYA-C motifs and clinical outcomes. Thus, the most frequent cagA type found among northeastern Thai dyspeptic patients was the Western cagA type, which is significantly associated with PUD indicating a possible predictive parameter for clinical outcome.

Nested polymerase chain reaction for detection of Helicobacter pylori in gastric biopsy specimens

Sensitivity and specificity are important for tests used to defect Helicobacter pylori infection from gastric biopsy specimens. Molecular methods, such as PCR and nested PCR, are sensitive methods for H. pylori detection. The objective of this study was to evaluate the performance of PCR and nested PCR compared to culture, the rapid urease test (RUT) and histology for the diagnosis of H. pylori in 130 gastric biopsy specimens from symptomatic dyspeptic patients. Sensitivity and specificity with PCR were 91 and 100% and with nested PCR were 95 and 97%, respectively. H. pylori was detected by PCR and nested PCR at levels as low as 125 fg (70 cells) and 25 fg (14 cells), respectively. These results suggest nested PCR is a highly sensitive direct method to detect H. pylori infection from biopsy specimens.

Antibacterial activity of Psidium guajava leaf and bark against multidrug-resistant Vibrio cholerae: implication for cholera control

In clinical cholera, a 3-day course of antibiotic complements extensive rehydration therapy by reducing stool volume, shortening the illness, and averting death. However, antibiotic therapy, which has lifesaving implications for cholera, is often hindered due to multidrug resistance in Vibrio cholerae, the cause of cholera. Crude aqueous mixture and water soluble methanol extract from leaf and bark of Psidium guajava, a tropical fruit guava of the family Myrtaceae, showed strong antibacterial activity against multidrug-resistant V. cholerae O1. The in vitro minimum inhibitory concentration of the crude aqueous mixture and water soluble methanol extract, which was bactericidal against 10(7) CFU/mL of V. cholerae was determined to be 1,250 microg/mL and 850 microg/mL, respectively. The antibacterial activity of P. guajava was stable at 100 degrees C for 15-20 min, suggesting nonprotein nature of the active component. The growth of V. cholerae in rice oral rehydration saline (ORS) was completely inhibited when 10 mg/mL (wt/vol) of crude aqueous mixture was premixed with the ORS in a ratio of 1:7 (vol. extract/vol. ORS). P. guajava, which is widely distributed in Bangladesh, thus offers great potential for use in indigenous, herbal medicine for controlling epidemics of cholera.

Antimicrobial susceptibility of Helicobacter pylori isolated from gastric biopsies in dyspeptic patients

The objective of this study was to evaluate the prevalence of antimicrobial resistance in Helicobacter pylori isolated from the antrum and corpus of dyspeptic patients in Khon Kaen, Thailand, and to compare the antimicrobial susceptibility patterns of H. pylori isolated from the antrum and corpus in individual patients. Antimicrobial susceptibility was determined by disk diffusion, studying susceptibility to metronidazole, clarithromycin, amoxicillin, erythromycin, ciprofloxacin, and tetracycline. The H. pylori resistant rate to at least one of the six antimicrobial agents tested was 37%. The resistance rates were 30.2% for metronidazole, 9.2% for ciprofloxacin, 5% for clarithromycin, 2.4% for amoxicillin, and 1.7% for erythromycin and tetracycline. Single, double, and more than double antimicrobial resistances were found in 27.7, 6.7 and 2.5%, respectively. Antimicrobial susceptibility testing revealed 11 antibiotypes. The most common antimicrobial susceptibility pattern found was sensitivity to 6 antimicrobial agents (63%). H. pylori antimicrobial resistance in specimens isolated from the antrum and corpus were nearly equivalent, 37.3% (22/59) and 36.7% (22/60), respectively. Most of the H. pylori specimens isolated from the antrum and corpus in individual patients were identical (87.7%).

Association of ompU gene in Vibrio cholerae from patients and environment with bile resistance

The objective of this study was to determine whether Vibrio cholerae, possessing ompU isolated from patients and the environment, conferred bile resistance and whether other virulence genes were also related to bile resistance. Fifty-two V cholerae O1 and non-O1 isolates were examined by PCR for the presence of the virulence-associated and regulatory genes, ctxA, tcpA, zot, ace, ompU, toxR, hlyA and stn/sto. V. cholerae possessing ompU resistant to equal or greater than 10% sodium deoxycholate were found in 93% of isolates but only in 9% of V. cholerae isolates not possessing ompU. The effects of other virulence genes on bile resistance could not be ascertained in this study. Thus V cholerae non-O1 with ompU and possibly other virulence genes isolated from the environment have the potential of affecting public health.

Application of duplex-PCR in rapid and reliable detection of toxigenic Vibrio cholerae in water samples in Thailand

Toxigenic Vibrio cholerae, the cause of cholera, is a native flora of the aquatic environment which is transmitted through drinking water and still remains the leading cause of morbidity and mortality in many developing countries including Thailand. The culture method (CM), which is routinely used for assessing water quality, has not proven as efficient as molecular methods because the notorious pathogen survives in water mostly in a non-culturable state. We employed duplex-polymerase chain reaction (duplex-PCR) for detection of tcpA and ctxA genes in toxigenic V. cholerae, and compared PCR detection with CM in various waters of Khon Kaen Municipality, Thailand. We also evaluated the effect of different pre-PCR conditions on the results of ctxA and tcpA detection including: 1) water filtered and enriched in alkaline peptone water (APW) for 3 h before PCR, 2) water filtered without enrichment before PCR, and 3) use of only enrichment in APW for 6 h before PCR. Of the 96 water samples (taken from waste-water, potable and waste-water from patients' houses, and from rivers) tested, 48 (50%) were positive for ctxA and tcpA by duplex-PCR, whereas only 29 (30%) were positive for V. cholerae by CM. Of the 29 V. cholerae isolated by CM, 2 (7%) were toxigenic V. cholerae belonging to serovar O1, while the rests were non-O1/ non-O139. Results revealed, therefore, that ctxA and tcpA-targeted duplex PCR is more sensitive than CM for detection of toxigenic V. cholerae from water samples because CM detected much less toxigenic V. cholerae than the non-toxigenic V. cholerae. Template DNA as low as 100 fg or 23 cells of V. cholerae in the water sample was detected in duplex PCR. Pre-PCR filtration followed by enrichment for 3 h significantly increase in the efficiency of duplex-PCR detection of toxigenic V. cholerae.

Prevalence of Helicobacter pylori vacA, cagA, cagE, iceA and babA2 genotypes in Thai dyspeptic patients

OBJECTIVES

To investigate the prevalence of the vacA, cagA, cagE, iceA, and babA2 genotypes in Helicobacter pylori strains isolated from Thai dyspeptic patients, and to determine whether any correlation exists between these genotypes and clinical manifestations.

METHODS

Helicobacter pylori was examined in 112 patients (62 with non-ulcer dyspepsia (gastritis), 34 with peptic ulcer disease, and 16 with gastric cancer (GCA)), detected by culture or direct detection from gastric biopsies. Allelic variants of the vacA, cagA, cagE, iceA, and babA2 genotypes were identified by using the polymerase chain reaction.

RESULTS

The positive rates for the vacAs1, vacAs2, cagA, cagE, iceA1, iceA2, and babA2 genes in H. pylori of dyspeptic patients were 100%, 0%, 98.2%, 88.4%, 45.5%, 33.1%, and 92%, respectively. The allelic variant vacAs1m1 was more prevalent (58%) than vacAs1m2 (42%). The cagA and cagE genes were commonly found together (87.5%). The most predominant genotypes were vacAs1m1, cagA, cagE, iceA1, and babA2. The various genes alone or in combination had no statistically significant association with the clinical outcomes (p>0.05).

CONCLUSION

Neither single gene nor combination of vacA, cagA, cagE, iceA, and babA2 genes was significantly helpful in predicting the clinical outcome of H. pylori infection in Thai patients. The high prevalence of these genes in H. pylori isolated from Thai patient groups suggests that H. pylori strains are geographically dependent.

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.

Enzyme-linked immunosorbent assay for serodiagnosis of Helicobacter pylori in dyspeptic patients and volunteer blood donors

Helicobacter pylori, an important etiological agent in the development of gastritis, peptic ulcer and gastric carcinoma, can be detected by the enzyme-linked immunosorbent assay (ELISA). Our objectives were: (1) to evaluate the efficacy of a commercial ELISA kit (Pyloriset EIA-G III) in sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for diagnosis of H. pylori infection in Thai dyspeptic patients in Khon Kaen Thailand; and (2) to examine the seroprevalence of H. pylori among blood donors at Srinagarind Hospital's Blood Bank, Khon Kaen University, by the commercial ELISA. Gastric biopsies obtained from 137 dyspeptic patients were diagnosed by culture, rapid urease test (RUT) and histology. Serum samples from the same dyspeptic patients and 100 healthy blood donors were assayed using the commercial ELISA. H. pylori infection in dyspeptic patients was considered positive when the culture or both RUT and histology were positive. Using a cut-off value at a titer of 20 U/ml (as recommended by the manufacturer), we found the commercial ELISA kit had a sensitivity of 93.3%, specificity of 75.3%, PPV of 74.7%, NPV of 93.5% and accuracy of 83.2%. The overall H. pylori seroprevalence in the healthy blood donors was 57%. Of the 100 healthy blood donors, 39 (60.9%) of the males and 18 (50.0%) of the females were seropositive.

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.

Epidemiology of antimicrobial resistance in Salmonella isolated from pork, chicken meat and humans in Thailand

Forty samples each of pork and chicken meat were collected from local retail markets in Khon Kaen, northeast Thailand, for Salmonella isolation and identification during 2003. Fifty-four isolates of Salmonella obtained from diarrheal patients admitted at a hospital located in the same town were serotyped. All isolates were also tested for antimicrobial sensitivity against amoxicillin (Amx), chloramphenicol (Chl), norfloxacin (Nor), ciprofloxacin (Cip), gentamicin (Gm), sulfamethoxazole and Trimethoprim (Sxt), Tetracycline (Tet), Streptomycin (Str) and sulfamethoxazole (Sulfa). The results showed that 26 (65%) pork samples and 30 (75%) chicken meat samples were contaminated with Salmonella. The most prevalent serovar in pork was S. Rissen (61.5%), followed by S. Stanley and S. Lexington (11.5%). In chicken meat, the most prevalent serovar was S. Anatum (33.3%), followed by S. Rissen (16.7%). Among isolates from human patients, S. Rissen (20.4%) and S. Stanley (18.5%) were the most frequently identified serovars. All the isolates were resistant to Str and Sulfa. None were resistant to Nor and Cip. Resistance to Amx, Chl, Gm, Sxt, and Tet in pork was 15.4, 15.4, 3.9, 15.4 and 88.5%, respectively. The resistance to those antimicrobial agents in chicken meat was 30.0, 26.7, 6.7, 20 and 100%, respectively, and in human patients was 27.8, 20.4, 5.6, 31.5 and 92.6%, respectively. Statistical analysis found no difference in the rate of resistance to Amx, Chl, Gm, and Sxt among the different sources of the Salmonella isolates (p > 0.05 for each antimicrobial agent). Our results indicate that antimicrobial resistant Salmonella strains were widely spread among pork and chicken meat, and in humans.

Analysis of three phenotyping methods and pulsed-field gel electrophoresis for differentiation of methicillin resistant Staphylococcus aureus isolated from two hospitals in Thailand

Methicillin resistant Staphylococcus aureus (MRSA) is an important hospital and community-acquired pathogen. Rapid and reliable epidemiologic typing is necessary for controlling the spread of MRSA outbreak. The objective of this study was to compare the phenotyping with the genotyping method to differentiate MRSA isolates obtained from the two hospitals in Thailand (central and northeastern). Seventy-four MRSA isolates were randomly collected and confirmed by the presence of mecA gene. Antibiogram, phage typing and enterotoxin production were used for the phenotyping analysis. Pulsed-field gel electrophoresis (PFGE) with Smal digestion of chromosomal DNA was used for the genotyping analysis. We found 17 distinct profiles by the 3 phenotypic typing methods and 18 PFGE types designated as 5 major types (A-E) and 13 subtypes. The most frequent PFGE types and their related subtypes found in both hospitals were A and C, comprising 54 and 27%, respectively. The antibiogram could differentiate 6 different types. All isolates were resistant to the majority of antimicrobial agents tested, but were susceptible to vancomycin and fosfomycin. Ten (13.5%) MRSA isolates produced enterotoxin A. Nontypable phage and phage type 77 were found predominantly in MRSA isolated from the northeast and central hospital, respectively. A significant correlation was found between the phenotyping and the genotyping methods and there was a good correlation between antibiogram and PFGE. Antibiogram typing alone can be used as a useful epidemiological marker for practical purposes. PFGE types A and C were the common endemic MRSA clones in both hospitals in Thailand.

Detection of H. pylori in dyspeptic patients and correlation with clinical outcomes

The objectives of this study were to evaluate the methods used to diagnose Helicobacter pylon infection in gastric biopsies, and to evaluate the correlation between H. pylori infection and clinical outcomes. Gastric biopsies, obtained from 210 patients, were evaluated for H. pylori by culture, a commercial rapid urease test (RUT, Pronto Dry) and histological examination. A true positive result was either the culture or both the RUT and histological examination were positive. The results showed a H. pylori infection rate of 44.3% (93/210). The sensitivities, specificities, positive predictive values and negative predictive values were 88.2, 100, 100, and 91.4 % by the culture; 95.7, 98.3, 97.8, and 96.6% by RUT; and 96.8, 59.8, 59.8, and 65.7% by histological examination, respectively. The prevalences of H. pylori in non-ulcer dyspepsia (NUD), peptic ulcer dyspepsia (PUD) and gastric cancer (GCA) patients were 41.2, 57.9 and 70.6%, respectively. The chi-squared-test showed that GCA patients were significantly more frequent infected with H. pylori than NUD patients (p<0.05). Our study indicates that the RUT method was highly sensitive, specific and appropriate for routine clinical use.

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.

Salmonellosis and the food chain in Khon Kaen, northeastern Thailand

Non-typhoidal salmonellosis is a major cause of food-borne illness in Thailand. Specific serotyping of Salmonellae, linked with certain foods, can be used to identify outbreaks, transmission, and for surveillance. We aimed to identify the chain of non-typhoidal Salmonella transmission from food to humans in five slums, two open markets, four supermarkets and an abattoir in the municipality of Khon Kaen. During three months representing the cool-dry, hot-dry, and rainy seasons of 2002, culture samples were collected from water, food, pork, and chicken. Stool cultures of food venders, and others in the same area, were performed. Serological typing was done by the WHO National Salmonella and Shigella Center in Thailand. Of the food, drinking water, and stool samples from food handlers and healthy persons, 18, 7, 11, and 5%, respectively, were positive for Salmonella. Nearly all (96-98%) of the fresh pork and chicken, both from the open markets and supermarkets, were positive for Salmonella. The major Salmonella serovars were S. Anatum, S. Rissen, S. Virchow, S. Enteritidis and S. Panama, similar throughout the food chain and to the other reports that year. To reduce the incidence of human salmonellosis, several preventative measures must be taken where animals are produced, slaughtered and processed, and at home and in eateries. Vulnerable groups, such as infants, the elderly and the immuno-compromised, should be made aware of their increased susceptibility to food-borne disease.

Evaluation of polymerase chain reaction, conventional and MRSA screen latex agglutination methods for detection of methicillin-resistant, -borderline and -susceptible Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA), is difficult and expensive to treat, therefore early screening is essential. Several phenotypic and genotypic methods are used to detect MRSA; however, the method of choice remains problematic. We have evaluated four phenotypic methods, broth microdilution (MIC), oxacillin disk agar diffusion (ODD), oxacillin screening salt agar (OSS), and a new rapid phenotypic (MRSA screen latex agglutination, MSLA) with the genotypic gold standard of PCR mecA detection to determine the most appropriate method for routine laboratory use. We randomly collected 203 S. aureus isolates from patients and carriers at two hospitals in Thailand. Using MIC method, three sub-groups were differentiated from among these isolates, namely MRSA (106 isolates), borderline-resistant S. aureus (BRSA) (65 isolates), and methicillin-susceptible S. aureus (MSSA)(32 isolates). A total of 10 methicillin-resistant S. epidermidis (MRSE) isolates were also included. The sensitivity and specificity of MIC, ODD, OSS, and MSLA were 99 and 96, 100 and 97, 100 and 97, and 100 and 100%, respectively. Our study indicated that ODD is still appropriate for routine laboratory. MSLA had the highest sensitivity and specificity and is rapid but expensive, so is the most appropriate method for emergency cases. MIC method was better for BRSA detection and OSS method was more appropriate for screening clinical specimens and carriers.

Evaluation of different primers for detecting mecA gene by PCR in comparison with phenotypic methods for discrimination of methicillin-resistant Staphylococcus aureus

Detection of the mecA gene by polymerase chain reaction (PCR) is the gold standard for identifying methicillin-resistant Staphylococcus aureus (MRSA). PCR assays, employing MR1-MR2 primers (primer set 1) and MR3-MR4 primers (primer set 2) to generate 154 and 533 bp fragment, respectively, are most widely used for amplification of mecA gene. The purpose of this study was to evaluate the presence of mecA gene in 100 clinical isolates of S. aureus using PCR with the two pairs of primers. The results were compared to the broth dilution MIC method, oxacillin salt screening method (OSS) and oxacillin disk agar diffusion method (ODD). Fifteen of the 100 isolates showed a discrepancy between the mecA primer sets 1 and 2. Three isolates (3%) without the mecA gene showed discrepancies with phenotypic methods. The sensitivity, specificity and positive and negative predictive values for the 154 and 533 bp products of mecA were 79, 85, 83, 81 and 94, 100, 100, 94%, respectively. The results indicated that primer set 2 was more appropriate than primer set 1 for the detection of mecA gene in MRSA. There was a good correlation among the mecA gene detection, ODD and OSS methods. The discrepancy of three isolates between PCR and phenotypic methods should be clarified for other resistant mechanisms.

Development of EIA for detection of Chlamydia trachomatis in genital specimens

A double antibody sandwich enzyme immunoassay (EIA) for chlamydial antigen detection was developed using a monoclonal antibody against lipopolysaccharide (LPS) of Chlamydia trachomatis as a coating antibody. Polyclonal rabbit antiserum against partially purified antigen from elementary body (EB) antibody and horse-radish peroxidase conjugated goat anti-rabbit antibody were used as the primary and secondary antibody respectively. The developed EIA could detect protein of partially purified EB at the lowest concentration of 250 ng/ml. The assay was evaluated against the cell culture (CC), DNA hybridization assay (PACE2 system: Gen-Probe, San Diego, CA, USA) and a commercial enzyme immunoassay (kEIA) (Bioquest, NSW, Australia). The sensitivity, specificity, positive and negative predictive values of the developed EIA (dEIA) were 87, 96.2, 80, 97.7 for the specimens from females and 90.9, 90.7, 71.4, 97.5 for the specimens from males repectively. Cross reaction was not found with Escherichia coli, Acinetobacter anitratus, beta-Streptococcus group A, Enterobacter spp, Enterococcus, Lactobacillus spp, Neisseria spp, but it was found with Candida albicans and herpes simplex virus type 1. The developed EIA can be applied successfully for both genders, particularly males. The cost per test is less than those for CC, kEIA and PACE2.

An assessment and evaluation of methods for diagnosis of chlamydial and gonococcal infections

Chlamydia trachomatis and Neisseria gonorrhoeae were studied in 350 females and 140 males attending the sexually transmitted disease clinic and AIDS Center, Khon Kaen zone 6 and the Division of Obstetrics and Gynecology, Khon Kaen Hospital. Chlamydia trachomatis infection was diagnosed by cell culture (CC), enzyme immunoassay (EIA) (Bioquest, NSW, Australia) and nucleic acid hybridization (PACE2 system: Gen-Probe, San Diego, Calif). It was found that the sensitivity, specificity and positive and negative predictive values in females were 95.7, 100.0, 100.0, 99.7% by the cell culture; 91.3, 99.1, 87.5, 99.4% by the EIA; and 78.3, 99.7, 94.7, 98.5% by the PACE2 respectively. Values of the same parameters in males were 83.3, 100.0, 100.0, 98.5% by the cell culture; 75.0, 99.2, 90.0, 97.7% by the EIA and 91.7, 100.0, 100.0, 99.2% by PACE2 respectively. The methods for detection of Neisseria gonorrhoeae infection were conventional culture, PACE2 test and the direct examination (Gram's stain). In females, the sensitivity, specificity and positive and negative predictive values of the conventional culture were 85.7, 100.0, 100.0, 99.7% and those of the PACE2 were 85.7, 99.1, 66.7, 99.7% respectively. In males, the values of the same parameters were 81.8, 100.0, 100.0, 100.0% by the conventional culture, 95.5, 100.0, 100.0 and 99.2% by the PACE2. The prevalence of chlamydial infection in females was 6.6% (23/350) and that in males was 8.6% (12/140). The prevalence of gonococcal infection in females was 2.0% (7/350) and in males was 15.7% (22/140). The co-infection of Chlamydia trachomatis and Neisseria gonorrhoeae in females was 0.9% (3/350) and no co-infection was found in males. It is concluded that cell culture is an appropriate method for detection of Chlamydia trachomatis in both genders, particularly in females. PACE 2 test is the best method for such detection in symptomatic males while EIA is a good method in females, particularly in symptomatic females. For gonococcal detection, PACE2 test is a sensitive, specific and alternative method to the conventional culture. It can be appropriately applied for the diagnosis of gonococcal infection, particularly in males.

Transcriptional analysis of the groESL operon of Neisseria gonorrhoeae

The nucleotide sequence upstream of the groEL gene of Neisseria gonorrhoeae has been determined. Upstream of groEL is a homolog of groES and the divergently transcribed frpB gene. The promoter region of groES lacks the inverted repeat sequences (IR) that act as a regulatory element controlling the expression of similar operons in many other bacterial species. This region contains overlapping consensus sequences for sigma 32-dependent and sigma 70-dependent promoters, and an appropriately placed transcription start point was mapped downstream of these promoters. Northern hybridization demonstrated that synthesis of a full-length groES-groEL transcript was induced in heat-stressed cells. These experiments also revealed the presence of a shorter groES-specific transcript, apparently the result of the premature termination of transcription at an IR situated between the groES and groEL genes.