Teera Kusolsuk

High prevalence of CTX-M β-lactamase-producing Enterobacteriaceae in stool specimens obtained from healthy individuals in Thailand

OBJECTIVES To determine the prevalence of CTX-M beta-lactamase-producing Enterobacteriaceae in stool specimens obtained from healthy individuals in a rural area of Thailand. METHODS Bacteria in stool specimens were screened for extended-spectrum beta-lactamase (ESBL) production on McConkey agar with cefotaxime and confirmed by the double-disc synergy test. Genetic detection and genotyping of CTX-M-type ESBL was performed by PCR with bacterial DNA extracted from isolates. RESULTS A markedly high number (82 of 141, 58.2%) of the specimens showed the presence of CTX-M beta-lactamase-producing Enterobacteriaceae, as confirmed by both phenotypic and genetic examinations. The majority of the CTX-M beta-lactamase-producing bacteria were Escherichia coli (85.1%). CONCLUSIONS The study revealed the wide dissemination of CTX-M beta-lactamase-producing Enterobacteriaceae in the healthy population.

Prevalence of and risk factors associated with faecal carriage of CTX-M β-lactamase-producing Enterobacteriaceae in rural Thai communities

OBJECTIVES To determine the prevalence of CTX-M β-lactamase-producing Enterobacteriaceae and to study the risk factors associated with faecal carriage in asymptomatic rural Thai people. METHODS In all, 417 stool samples were obtained from rural Thai people and screened for extended-spectrum β-lactamases (ESBLs) using MacConkey agar supplemented with 2 mg/L cefotaxime. Results were confirmed using cefotaxime and ceftazidime with and without clavulanic acid. The bla(CTX-M) genes were identified and genotyped using PCR with bacterial DNA samples. Multivariate analysis was performed to investigate risk factors associated with the faecal carriage of CTX-M producers. RESULTS The prevalence of CTX-M-type ESBL-producing Enterobacteriaceae was 65.7%. The CTX-M-9 group (60.6%) was dominant, followed by the CTX-M-1 group (38.7%). Most of the bacteria were Escherichia coli (85.4%) and Klebsiella pneumoniae (4.7%). Of a total of 234 E. coli strains, 48.7% belonged to phylogenetic group A, 28.6% to group B1, 15.8% to group D and 6.8% to group B2. Most CTX-M producers were susceptible to carbapenems and amikacin, but resistant to tetracycline and gentamicin. In a multivariate logistic regression model, better education status (OR 2.245; 95% CI 1.297-3.884), history of hospitalization (OR 1.643; 95% CI 1.036-2.603) and the use of antibiotics within the last 3 months (OR 1.883; 95% CI 1.221-2.903) were independently associated with faecal carriage. CONCLUSIONS Faecal carriage of CTX-M-type ESBL-producing Enterobacteriaceae among asymptomatic individuals in rural Thailand remains alarmingly high, and previous antibiotic use and a history of hospitalization may contribute to its dissemination.

Outbreak of Trichinellosis Caused by Trichinella papuae, Thailand, 2006

In 2006, the Thailand Ministry of Public Health studied 28 patients from a village in northern Thailand. All had myalgia, edema, fever, and gastrointestinal symptoms; most had eaten wild boar. A muscle biopsy specimen from a patient showed nonencapsulated larvae with a cytochrome oxidase I gene sequence of Trichinella papuae.

Human monoclonal antibodies to neutralize all dengue virus serotypes using lymphocytes from patients at acute phase of the secondary infection

The global spread of the four dengue virus serotypes (DENV-1 to -4) has made this virus a major and growing public health concern. Generally, pre-existing neutralizing antibodies derived from primary infection play a significant role in protecting against subsequent infection with the same serotype. By contrast, these pre-existing antibodies are believed to mediate a non-protective response to subsequent heterotypic DENV infections, leading to the onset of dengue illness. In this study, we prepared hybridomas producing human monoclonal antibodies (HuMAbs) against DENV using peripheral blood mononuclear cells (PBMCs) from patients in the acute phase (around 1 week after the onset of illness) or the convalescent phase (around 2weeks after the onset of illness) of secondary infection. Interestingly, a larger number of hybridoma clones was obtained from patients in the acute phase than from those in the convalescent phase. Most HuMAbs from acute-phase infections were cross-reactive with all four DENV serotypes and showed significant neutralization activity to all four DENV serotypes. Thus, secondary DENV infection plays a significant role in stimulating memory cells to transiently increase the number of antibody-secreting plasma cells in patients in the early phase after the secondary infection. These HuMAbs will enable us to better understand the protective and pathogenic effects of DENV infection, which could vary greatly among secondarily-infected individuals.

Analysis of risk factors for a high prevalence of extended-spectrum {beta}-lactamase-producing Enterobacteriaceae in asymptomatic individuals in rural Thailand.

The prevalence of and risk factors associated with extended-spectrum β-lactamase (ESBL)-producing micro-organisms have not been well studied in healthy individuals. The aim of this study was to determine this in healthy individuals in Thailand. Stool samples and questionnaires obtained from 445 participants from three provinces in Thailand were analysed. The antimicrobial susceptibility of the isolates was assessed using phenotypic and genotypic methods. PCR analysis was performed to detect and group the bla(CTX-M) genes. The prevalence of CTX-M-type ESBL-producing Enterobacteriaceae in the three provinces was as follows: 29.3 % in Nan (43/147), 29.9 % in Nakhon Si Thammarat (43/144) and 50.6 % in Kanchanaburi (78/154) (P<0.001). Of the 445 samples, 33 (7.4 %), 1 (0.2 %) and 127 (28.5 %) isolates belonged to the bla(CTX-M) gene groups I, III and IV, respectively. Escherichia coli was the predominant member of the Enterobacteriaceae producing CTX-M-type ESBLs (40/43, 39/43 and 70/78 isolates in Nan, Nakhon Si Thammarat and Kanchanaburi, respectively). No statistically significant association was observed between the presence of ESBL-producing bacteria and gender, age, education, food habits or antibiotic usage. However, the provinces that had the highest prevalence of ESBL-producing Enterobacteriaceae also had the highest prevalence of use and purchase of antibiotics without a prescription. Thus, this study revealed that faecal carriage of ESBL-producing Enterobacteriaceae is very high in asymptomatic individuals in Thailand, with some variations among the provinces. This high prevalence may be linked to antibiotic abuse.

Wide dissemination of extended-spectrum β-lactamase-producing Escherichia coli in community residents in the Indochinese peninsula

Recent studies have reported a widespread distribution of extended-spectrum β-lactamase (ESBL)-producing bacteria, not only in the nosocomial setting, but also in the community; some local communities in Southeast Asia have been reported to show a high prevalence of ESBL-producing bacteria. However, the details regarding the quantitative/qualitative state of ESBL-producing bacterial spread in Southeast Asia are currently unclear. Thus, the aim of this study was to assess the state of ESBL-producing bacterial spread in community residents from the Indochinese peninsula, as a representative region of Southeast Asia. In order to achieve this aim, local community residents in Laos and Vietnam were examined for fecal carriage of ESBL-producing Enterobacteriaceae, and the findings were compared with data from a previous study in Thailand which was conducted in the same manner as this study. Between 47.0%–70.2% of the Laotian and Vietnamese residents carried ESBL-producing CTX-M genotype Enterobacteriaceae. The most common sub-genotypes of CTX-M were CTX-M-1 (33.0%–47.5%) and CTX-M-9 (47.5%–64.1%), and these rates were similar among all three countries. Taken together, these results confirmed that ESBL-producing Enterobacteriaceae are widely disseminated in Indochinese countries, such as Thailand, Laos, and Vietnam.

The second outbreak of trichinellosis caused by Trichinella papuae in Thailand

A human trichinellosis outbreak caused by Trichinella papuae occurred in the Uthai Thani Province of Thailand in September 2007. A total of 34 villagers suffering at least one of the symptoms suggestive of trichinellosis, or those who were asymptomatic but had a history of ingesting raw wild pig meat, were enrolled in the study. Twenty-two villagers had ingested undercooked pork from a hunted wild pig (Sus scrofa). One patient with a severe clinical picture was hospitalised and more than 80 non-encapsulated larvae were detected in the muscle biopsy. The larvae were identified as T. papuae by molecular analyses of the mitochondrial cytochrome c oxidase subunit I (COI) gene and the expansion segment 5 (ES5) of the large subunit rRNA. Of the 34 suspected cases, 27 agreed to be subjected to haematological and serological tests. Immunoblot analysis using crude antigens from T. spiralis muscle larvae revealed anti-Trichinella IgG in 20 of the 26 serum samples (1 serum sample could not be analysed). All infected people were successfully treated with mebendazole; the one patient with severe symptomatology was treated successfully with prednisolone.

Molecular and serological survey on taeniasis and cysticercosis in Kanchanaburi Province, Thailand.

A community-based field survey on taeniasis and cysticercosis was performed in two villages in Thong Pha Phum District, Kanchanaburi Province, central Thailand, where 3 Taenia species, T. solium, T. saginata and T. asiatica, are sympatrically occurring. Four (0.6%) out of 667 stool samples were egg-positive for Taenia sp. by Kato-Katz technique. Three out of those four persons and other three persons who were Taenia egg-negative but having a recent (<1 year) history of discharging worms in stool were treated with niclosamide. One Taenia egg-positive woman was not treated because of severe ascites. After treatment, three persons expelled long strobilae with scolices and two persons expelled strobilae without scolex. One Taenia egg-positive person did not expel any worms post-treatment. Among 5 persons, four expelled a single worm, whereas one expelled multiple worms, may be 6 worms but not confirmed by detection of scolices. One scolex was armed with hooklets, whereas 2 others did not. Multiplex PCR of 10 expelled proglottids (including 6 estimated worms from one patient) revealed that one sample was T. solium, one T. saginata, and 8 T. asiatica. A total of 159 residents agreed to receive a serological test for cysticercosis. By ELISA using partially purified glycoprotein antigen, 9 cases, 5 and 4 from villages A and B respectively, were found to be sero-positive. The five and an additional sample on the border line from village A were evaluated using confirmative immunoblot using recombinant chimeric antigen. Among the six samples, four including the border line sample were confirmed to be cysticercosis by immunoblotting. One of the 4 persons had neurological symptoms with nodular lesions in the brain by computed tomography. These 4 confirmed or suspected cysticercosis cases were free of T. solium worms, but two of them including confirmed NCC case had a past (>1 year) history of expelling proglottids in the stool.

The first workshop towards the control of cestode zoonoses in Asia and Africa.

The first workshop towards the control of cestode zoonoses in Asia and Africa was held in Asahikawa Medical University, Japan on 15 and 16 Feb 2011. This meeting was fully supported by the Asian Science and Technology Strategic Cooperation Promotion Programs sponsored by the Special Coordination Funds for Promoting Science and Technology, the Ministry of Education Japan (MEXT) for 3 years from 2010 to Akira Ito. A total of 24 researchers from 9 countries joined together and discussed the present situation and problems towards the control of cestode zoonoses. As the meeting was simultaneously for the establishment of joint international, either bilateral or multilateral collaboration projects, the main purposes were directed to 1) how to detect taeniasis/cysticercosis infected patients, 2) how to differentiate Taenia solium from two other human Taenia species, T. saginata and T. asiatica, 3) how to evaluate T. asiatica based on the evidence of hybrid and hybrid-derived adult tapeworms from Thailand and China, 4) how to evaluate T. solium and T. hyaenae and other Taenia species from the wild animals in Ethiopia, and 5) how to detect echinococcosis patients and 6) how to differentiate Echinococcus species worldwide. Such important topics are summarized in this meeting report.

Egg laying capacity of Haplorchis taichui (Digenea: Heterophyidae) in humans.

Quantitative fecal egg counts represented as the number of eggs per gram of feces (EPG) are generally a reliable parameter to estimate the worm burden of intestinal and hepatic parasitoses. Although Haplorchis taichui (Digenea: Heterophyidae) is one of the most common minute human intestinal flukes, little is known about the relationship between EPG and the actual worm burden in patients or the severity of the disease. In the present study, fecal samples were collected from 25 villagers in northern Thailand before and after praziquantel treatment. The EPG values of each participant were determined by the modified cellophane thick smear method, and adult worms were collected from the whole stool after the treatment. Eggs per day per worm (EPDPW) of H. taichui were estimated 82 from egg counts and expelled worms. The EPG was not well correlated with the worm burden, and a reverse correlation was observed between the EPDPW and the worm burden.