BackgroundPlasmodium knowlesi, a simian malaria parasite, has been reported in humans in many Southeast Asian countries. In Thailand, most of the limited numbers of cases reported so far were from areas near neighbouring countries, including Myanmar.MethodsBlood samples collected from 171 Thai and 248 Myanmese patients attending a malaria clinic in Ranong province, Thailand, located near the Myanmar border were investigated for P. knowlesi using nested PCR assays. Positive samples were also investigated by PCR for Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae and Plasmodium ovale, and were confirmed by sequencing the gene encoding the circumsporozoite protein (csp).ResultsTwo samples, one obtained from a Thai and the other a Myanmese, were positive for P. knowlesi only. Nucleotide sequences of the csp gene derived from these two patients were identical and phylogenetically indistinguishable from other P. knowlesi sequences derived from monkeys and humans. Both patients worked in Koh Song, located in the Kawthoung district of Myanmar, which borders Thailand.ConclusionThis study indicates that transmission of P. knowlesi is occurring in the Ranong province of Thailand or the Kawthoung district of Myanmar. Further studies are required to assess the incidence of knowlesi malaria and whether macaques in these areas are the source of the infections.

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An increasing production of natural rubber (NR) products has led to major challenges in waste management. In this study, the degradation of rubber latex gloves in a mineral salt medium (MSM) using a bacterial consortium, a mixed culture of the selected bacteria and a pure culture were studied. The highest 18% weight loss of the rubber gloves were detected after incubated with the mixed culture. The increased viable cell counts over incubation time indicated that cells used rubber gloves as sole carbon source leading to the degradation of the polymer. The growth behavior of NR-degrading bacteria on the latex gloves surface was investigated using the scanning electron microscope (SEM). The occurrence of the aldehyde groups in the degradation products was observed by Fourier Transform Infrared Spectroscopy analysis. Rhodococcus pyridinivorans strain F5 gave the highest weight loss of rubber gloves among the isolated strain and posses latex clearing protein encoded by lcp gene. The mixed culture of the selected strains showed the potential in degrading rubber within 30 days and is considered to be used efficiently for rubber product degradation. This is the first report to demonstrate a strong ability to degrade rubber by Rhodococcus pyridinivorans.

Vibrio parahaemolyticus was isolated from shrimp of five farms located in the Pattani and Songkhla provinces of southern Thailand. Using a PCR method targeted to the unique DNA sequences derived from the plasmid (AP2 primers) and the toxin gene (AP3 primers) of V. parahaemolyticus that caused acute hepatopancreatic necrosis disease (AHPND), a total of 33 of 108 isolates were positive. In contrast, all 63 and 66 isolates of clinical and environmental V. parahaemolyticus, respectively, obtained previously from 2008 to 2014 from the same area were negative. This implied that these strains were likely to be the cause of the outbreak of AHPND in this area. Intestinal samples proved to be a better source for the isolation of V. parahaemolyticus AHPND than the hepatopancreas. All isolates were investigated for haemolytic activity, virulence genes, serotypes, genotypes and antibiotic susceptibility. All the AHPND isolates had a unique O antigen, but small variations of the K antigens were detected from different farms. In addition, the DNA profiles of V. parahaemolyticus AHPND isolates were similar, but distinct from those clinical and environmental isolates. It is postulated that the causative agent of AHPND might have originated from one clone and then slightly different serotypes subsequently developed.

Toxoplasmosis is one of the most common opportunistic parasitic diseases in patients living with HIV/AIDS. This study aimed to determine the seroprevalence of Toxoplasma infection in HIV-infected patients and to identify associated risk factors in Toxoplasma seropositive patients. This study was conducted at a regional public hospital in Hat Yai, southern Thailand during October 2009 to June 2010. Blood samples were collected from 300 HIV-infected patients. Each subject also answered a socio-demographic and risk factors associated with Toxoplasma infection. The prevalence of anti-Toxoplasma IgG antibodies in HIV-infected patients was 109 (36.3%), of which 83 (76.2%) had past infection and 26 (23.9%) had recently acquired Toxoplasma infection as indicated by their IgG avidity. Multivariate analysis using logistic regression showed that gender difference (adjusted OR = 1.69, 95% CI = 1.05–2.72) was the only factor associated with Toxoplasma infection. From the results obtained, these HIV-infected patients could be at high risk of developing clinical evidence of severe toxoplasmosis. Therefore, it is necessary to introduce primary behavioral practices to prevent Toxoplasma infection among HIV-infected patients.

Gray oyster mushroom, a common edible mushroom in Thailand, has been used as a source for polysaccharide extraction and purification. In this study, we extracted polysaccharides from the gray oyster mushroom through hot water, ammonium oxalate, and alkaline extraction methods. The extracts were further purified using enzymatic digestion, solvent extraction, and column chromatography. Fourier‐transform infrared spectroscopy reveals that the selected fractions contain β‐(1→3) glucan and mannan. Monosaccharide composition analysis suggests that glucose and mannose are the major constituents of all analyzed fractions. Interestingly, only the gel‐like fraction, namely SG1‐1 could enhance neutrophils’ killing activity on Candida albicans. In addition, the purified fractions stimulated glucose uptake activity in the L6 myotubes in a dose‐dependent manner. Practical applications The ability of those polysaccharides to stimulate glucose uptake in the muscle cells and enhance a neutrophil’s killing activity implicates the antidiabetic and immunostimulatory activities, respectively. Thus, these polysaccharides could be potentially developed into an immunostimulating agent and an alternative medicine for treating diabetes mellitus.

Vibrio alginolyticus is one of the most serious causative agents of diseases in cultured marine fish and shellfish. However, the characteristics of virulence factors in pathogenic V. alginolyticus are poorly known. To gain insight into fish diseases caused by V. alginolyticus, we carried out two-dimensional gel electrophoresis (2-DE) combined with MALDI-TOF mass spectrometry to identify uniquely expressed proteins in the disease-causing V. alginolyticus. V. alginolyticus strains were isolated from marine environments and diseased fish obtained from southern Thailand. We identified seven unique proteins in the disease-causing V. alginolyticus strain. Among those, the outer membrane protein A (OmpA) had the strongest expression. Therefore, the function of this protein was further analysed. To investigate the role of OmpA protein, an in-frame deletion mutant of ompA was constructed using the homologous recombination method. Although the ompA mutant V. alginolyticus strain (ΔompA) grew normally, the mutant exhibited a significant defect in the swarming ability and the biofilm formation. Furthermore, Galleria mellonella larvae injected with the mutant bacteria had a significantly greater survival percentage than those injected with the wild-type strain, demonstrating that OmpA protein is required for the pathogenicity of V. alginolyticus. Together, this study suggests a potential target for vaccine development against pathogenic V. alginolyticus strain. K E Y W O R D SGalleria mellonella, MALDI-TOF mass spectrometry, ompA, two-dimensional gel electrophoresis, Vibrio alginolyticus How to cite this article: Bunpa S, Chaichana N, Teng JLL, et al. Outer membrane protein A (OmpA) is a potential virulence factor of Vibrio alginolyticus strains isolated from diseased fish. J Fish Dis. 2020;43:275-284. https ://doi.

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