Theerakamol Pengsakul

Molecular survey of the head louse Pediculus humanus capitis in Thailand and its potential role for transmitting Acinetobacter spp.

BackgroundHead louse infestation, which is caused by Pediculus humanus capitis, occurs throughout the world. With the advent of molecular techniques, head lice have been classified into three clades. Recent reports have demonstrated that pathogenic organisms could be found in head lice. Head lice and their pathogenic bacteria in Thailand have never been investigated. In this study, we determined the genetic diversity of head lice collected from various areas of Thailand and demonstrated the presence of Acinetobacter spp. in head lice.MethodsTotal DNA was extracted from 275 head louse samples that were collected from several geographic regions of Thailand. PCR was used to amplify the head louse COI gene and for detection of Bartonella spp. and Acinetobacter spp. The amplified PCR amplicons were cloned and sequenced. The DNA sequences were analyzed via the neighbor-joining method using Kimura’s 2-parameter model.ResultsThe phylogenetic tree based on the COI gene revealed that head lice in Thailand are clearly classified into two clades (A and C). Bartonella spp. was not detected in all the samples, whereas Acinetobacter spp. was detected in 10 samples (3.62%), which consisted of A. baumannii (1.45%), A. radioresistens (1.45%), and A. schindleri (0.72%). The relationship of Acinetobacter spp. and the head lice clades showed that Acinetobacter spp. was found in clade A and C.ConclusionsHead lice in Thailand are classified into clade A and B based on the COI gene sequences. Pathogenic Acinetobacter spp. was detected in both clades. The data obtained from the study might assist in the development of effective strategies for head lice control in the future. Detection of pathogenic bacteria in head lice could raise awareness of head lice as a source of nosocomial bacterial infections.

Detection of an Unknown Trypanosoma DNA in a Phlebotomus stantoni (Diptera: Psychodidae) Collected From Southern Thailand and Records of New Sand Flies With Reinstatement of Sergentomyia hivernus Raynal & Gaschen, 1935 (Diptera: Psychodidae).

Abstract Although female sand flies are best known as the vectors of Leishmania parasites and viruses, several previous reports have demonstrated that these insects can also act as vectors for the trypanosomes of bats, lizards, and snakes. In this report, we created an inventory of Phlebotomine sand flies from southern Thailand. A novel trypanosome was found in a specimen of Phlebotomus stantoni, and two sand fly species newly recorded in the country, Sergentomyia khawi and Sergentomyia hivernus, were described. PCR primer pairs specific for the internal transcribed spacer 1 (ITS1) and the small subunit ribosomal DNA (SSU rDNA) gene of trypanosomatids were used to demonstrate the presence of the parasite in the sand fly. In addition, the Cytochrome b (CytB) gene was used to identify the sand fly species. Among the 45 samples of the sand fly that were collected, seven samples were Ph. stantoni sand flies and a single sample was positive for Trypanosoma sp. through PCR analysis. This study represents the first detection of Trypanosoma sp. in a sand fly from Thailand. The ITS1 and SSU rDNA sequences indicated that this specimen is suspected to be a novel Trypanosoma species. Further studies of this suspected new Trypanosoma species, including its vertebrate hosts and pathogenic potential, are therefore necessary.

Biological activities and functional analysis of macrophage migration inhibitory factor in Oncomelania hupensis, the intermediate host of Schistosoma japonicum

ABSTRACT Schistosomiasis is a destructive parasitic zoonosis caused by agents of the genus Schistosoma, which afflicts more than 250 million people worldwide. The freshwater amphibious snail Oncomelania hupensis serves as the obligate intermediate host of Schistosoma japonicum. Macrophage migration inhibitory factor (MIF) has been demonstrated to be a pleiotropic immunoregulatory cytokine and a key signaling molecule involved in adaptive and innate immunity. In the present study, we obtained the full‐length cDNA of OhMIF and analyzed the characteristics of the ORF and the peptide sequence in O. hupensis. Next we have successfully expressed and purified the recombinant OhMIF protein (rOhMIF) together with a site‐directed mutant rOhMIFP2G, in which the N‐terminal Proline (Pro2) was substituted by a Gly. Our results indicated that rOhMIF displayed the conserved D‐dopachrome tautomerase activity which is dependent on Pro2, and this enzymatic activity can be significantly inhibited by the MIF antagonist ISO‐1. Moreover, we also measured and compared the steady state kinetic values for D‐dopachrome tautomerase activity of rOhMIF and rHsMIF, and the results showed that the reaction rate, catalytic efficiency and substrate affinity of rOhMIF are significantly lower than those of rHsMIF. Additionally, we also showed that rOhMIF had the oxidoreductase activity which can utilize DTT as reductant to reduce insulin. Furthermore, the results obtained from the in vitro injection assay demonstrated that rOhMIF and its mutant rOhMIFP2G can also induce the phosphorylation and activation of ERK1/2 pathway in O. hupensis circulating hemocytes, indicating that the tautomerase activity is not required for this biological function. These results are expected to produce a better understanding of the internal immune defense system in O. hupensis, and help to further explore the interaction between O. hupensis and its natural parasite S. japoniucm. HIGHLIGHTSWe have successfully expressed and purified the recombinant OhMIF protein (rOhMIF) from Oncomelania hupensis.rOhMIF displays the conserved D‐dopachrome tautomerase enzymatic activity dependent on the Pro2 residue.We measured and analyzed the steady state kinetic values for the D‐dopachrome tautomerase activity of rOhMIF.rOhMIF has the oxidoreductase activity which can utilize DTT as reductant to reduce insulin.The tautomerase activity of rOhMIF is not required for its biological function on the activation of ERK1/2 pathway.