BackgroundTwo-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.ResultThis 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.ConclusionThis 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.Electronic supplementary materialThe online version of this article (10.1186/s12866-018-1150-7) contains supplementary material, which is available to authorized users.

Human strongyloidiasis is one of the neglected tropical diseases caused by infection with soil-transmitted helminth Strongyloides stercoralis. Conventional stool examination, a method commonly used for diagnosis of S. stercoralis, has low sensitivity, especially in the case of light infections. Herein, we developed the droplet digital polymerase chain reaction (ddPCR) assay to detect S. stercoralis larvae in stool and compared its performance with real-time PCR and stool examination techniques (formalin ethyl-acetate concentration technique [FECT] and agar plate culture [APC]). The ddPCR results showed 98% sensitivity and 90% specificity, and real-time PCR showed 82% sensitivity and 76.7% specificity when compared with the microscopic methods. Moreover, ddPCR could detect a single S. stercoralis larva in feces, and cross-reactions with other parasites were not observed. In conclusion, a novel ddPCR method exhibited high sensitivity and specificity for detection of S. stercoralis in stool samples. This technique may help to improve diagnosis, particularly in cases with light infection. In addition, ddPCR technique might be useful for screening patients before starting immunosuppressive drug therapy, and follow-up after treatment of strongyloidiasis.

Strongyloides stercoralis affects more than half a billion people worldwide, and hyperinfection in immunocompromised patients can be fatal. Elimination of this neglected tropical disease requires field-applicable diagnostic tools. We conducted a laboratory evaluation of a lateral flow rapid dipstick test (SsRapid™) using sera samples from a Strongyloides-endemic area in northeast Thailand. Group 1 was S. stercoralis-positive and larvae- and/or antibody-positive (according to the IgG ELISA) (N = 100). Group 2 had negative fecal examination and IgG ELISA results (N = 25). Group 3 had other parasitic infections and negative IgG ELISA results (N = 25). The results showed good diagnostic sensitivity (82%) and excellent specificity (96%). Suggested improvements in the SsRapid™ test include increased diagnostic sensitivity and conversion to the more robust cassette format. Field studies should be performed as well.

Infection by Opisthorchis viverrini causes significant health problems, including cholangiocarcinoma (CCA); thus control and elimination of this trematode is an important strategy for the reduction of CCA. Currently, urine and copro antigen detection is more sensitive than parasitological examination of the feces for the diagnosis of opisthorchiasis. Given limitations in human studies, we used an animal model to quantify the parasite antigen profiles in urine and feces in O. viverrine–infected hamsters, and postdrug treatment. The positive detections of O. viverrini antigen began from week 1 in urine and week 2 in feces after infection until week 28 of the study. The recoveries of O. viverrini worms were detected starting from week 1 and eggs of O. viverrini were detected in feces from week 3 after infection and remained detectable throughout the study period. There was a significant positive correlation of urine and copro antigen levels with the number of fecal egg counts (P < 0.01) and worm recovery (P < 0.01). In the drug-treatment experiment, treatment of infected hamsters with praziquantel significantly reduced worm burden, fecal egg output, and antigen in urine and feces compared with the untreated controls (P < 0.001). At 4 weeks posttreatment, the egg and worm reduction rates were 100% and 95.5%, respectively. The positive antigen detections in urine and feces corresponded with partial worm clearance from praziquantel treatment. This study demonstrated a direct link of urine and copro antigen tests with worms infecting the liver thereby reaffirming the reliability of urine and copro antigen assay in opisthorchiasis diagnosis.

Detection of IgG in urine is an efficient method comparable to that in serum for diagnosis of strongyloidiasis but effects of daily variation in urine dilution on diagnostic accuracy is not clearly known. This study evaluated effects of urine concentration on detection of parasite-specific IgG by urine enzyme-linked immunosorbent assay (ELISA), particularly in individuals with border-line results or false-negative diagnosis. Optimal concentration conditions were established by comparing Strongyloides -specific IgG antibody levels between unconcentrated and concentrated urine in participants with different infection intensities, namely healthy control (HC), low-negative (LN), high-negative (HN) and low-positive (LP) groups. The optimal condition was selected and validated in a field-trial study. The final urine concentration protocol required centrifugation at 4,000 g at 4°C for 10 mins using the Amicon® concentrator tube. This protocol was validated in groups of participants with varying diagnoses according to urine ELISA and fecal examination (n=148). The concentrated-urine ELISA increased the proportion of positive results in the LN group by 68.2% and by 100% in the HN group. Significantly elevated IgG antibody levels were seen in the LP group. In the group that was false negative by urine ELISA but positive by fecal examination (n=28), concentrated-urine ELISA yielded 100% positive results. Overall, the frequency estimates of S. stercoralis were 23.6% by fecal culture, 27% by standard urine ELISA and 90.5% by concentrated-urine ELISA. Concentration of urine samples prior to analysis by ELISA improved the sensitivity for diagnosis and is potentially useful in diagnosis of strongyloidiasis in immunocompromised individuals or in low-prevalence areas.