Extracellular vesicles from Staphylococcus aureus promote the pathogenicity of Pseudomonas aeruginosa

Co-infections with Staphylococcus aureus and Pseudomonas aeruginosa are common in patients with chronic wounds, but little is known about their synergistic effect mediated by extracellular vesicles (EVs). In this study, we investigated the effect of EVs derived from S. aureus (SaEVs) on the pathogenicity of P. aeruginosa. By using lipophilic dye, we could confirm the fusion between SaEV and P. aeruginosa membranes. However, SaEVs did not alter the growth and antibiotic susceptible pattern of P. aeruginosa. Differential proteomic analysis between SaEV-treated and non-treated P. aeruginosa was performed, and the results revealed that lipopolysaccharide (LPS) biosynthesis protein in P. aeruginosa significantly increased after SaEV-treatment. Regarding this result, we also found that SaEVs promoted LPS production, biofilm formation, and expression of polysaccharide polymerization-related genes in P. aeruginosa. Furthermore, invasion of epithelial cells by SaEV-pretreated P. aeruginosa was enhanced. On the other hand, uptake of P. aeruginosa by RAW 264.7 macrophages was impaired after pretreatment P. aeruginosa with SaEVs. Proteomic analysis SaEVs revealed that SaEVs contain the proteins involving in host cell colonization, inhibition of host immune response, anti-phagocytosis of the macrophages, and protein translocation and iron uptake of S. aureus. In conclusion, SaEVs serve as a mediator that promote P. aeruginosa pathogenicity by enhancing LPS biosynthesis, biofilm formation, epithelial cell invasion, and macrophage uptake impairment.

The new 222-nm far ultraviolet-C lowers bacterial contamination to endoscopists during esophagogastroduodenoscopy

Objectives

This study aimed to clarify the disinfectant efficacy of the 222-nm far ultraviolet-C (UV-C) during esophagogastroduodenoscopy using bacterial cultures.

Methods

The endoscopists performed esophagogastroduodenoscopy wearing a gown with a tryptic soy agar medium plate on their epigastric region and were divided into two groups: 222-nm far UV-C irradiation (UV group) and non-UV irradiation (non-UV group). As a control group, tryptic soy agar medium plates were placed about 110 cm above the floor. The incidence of bacterial contamination was determined by positive bacterial culture. The cultured bacteria were identified by 16S rRNA sequencing. Additionally, the actual UV exposure dose was measured using the UV-indicator card which changed colors upon exposure to 222 nm far UV-C.

Results

The bacterial culture positivity in the UV group (5.03%) was significantly lower than that in the non-UV group (25.76%), p < 0.0001. Most of the bacteria identified in the UV and non-UV groups were normal constituents of the oral flora, including Streptococcus salivarius and Staphylococci. Conversely, pathogenic microbes were found in the control group. The actual exposure doses of 222-nm far UV-C at the endoscopists' face, neck, and epigastric region were 2.09 ± 0.29, 5.89 ± 0.49, and 7.36 ± 0.58 mJ/cm2, respectively.

Conclusions

The 222-nm far UV-C irradiation reduced bacterial contamination for endoscopists. It can be used with conventional physical coverings to provide more effective infection control.

Heat Shock Protein SSA1 Enriched in Hypoxic Secretome of Candida albicans Exerts an Immunomodulatory Effect via Regulating Macrophage Function

Candida albicans is an opportunistic pathogenic yeast that can survive in both normoxic and hypoxic environments. The involvement of C. albicans secretome on host biological processes has been demonstrated. However, the immunoregulatory function of C. albicans secretome released under hypoxic condition remains unclear. This study demonstrated the differences in cytokine responses and protein profiles between secretomes prepared under normoxic and hypoxic conditions. Furthermore, the immunoregulatory effects of heat shock protein SSA1(Ssa1), a protein candidate enriched in the hypoxic secretome, were investigated. Stimulation of mouse bone marrow-derived macrophages (BMMs) with Ssa1 resulted in the significant production of interleukin (IL)-10, IL-6, and tumor necrosis factor (TNF)-α as well as the significant expression of M2b macrophage markers (CD86, CD274 and tumor necrosis factor superfamily member 14), suggesting that C. albicans Ssa1 may promote macrophage polarization towards an M2b-like phenotype. Proteomic analysis of Ssa1-treated BMMs also revealed that Ssa1 reduced inflammation-related factors (IL-18-binding protein, IL-1 receptor antagonist protein, OX-2 membrane glycoprotein and cis-aconitate decarboxylase) and enhanced the proteins involved in anti-inflammatory response (CMRF35-like molecule 3 and macrophage colony-stimulating factor 1 receptor). Based on these results, we investigated the effect of Ssa1 on C. albicans infection and showed that Ssa1 inhibited the uptake of C. albicans by BMMs. Taken together, our results suggest that C. albicans alters its secretome, particularly by promoting the release of Ssa1, to modulate host immune response and survive under hypoxic conditions.

Genetic determinants of Biofilm formation of Helicobacter pylori using whole-genome sequencing

BACKGROUND

Infection with Helicobacter pylori as the cause of gastric cancer is a global public health concern. In addition to protecting germs from antibiotics, biofilms reduce the efficacy of H. pylori eradication therapy. The nucleotide polymorphisms (SNPs) related with the biofilm forming phenotype of Helicobacter pylori were studied.

RESULTS

Fifty-six H. pylori isolate from Bangladeshi patients were included in this cross-sectional study. Crystal violet assay was used to quantify biofilm amount, and the strains were classified into high- and low-biofilm formers As a result, strains were classified as 19.6% high- and 81.4% low-biofilm formers. These phenotypes were not related to specific clades in the phylogenetic analysis. The accessories genes associated with biofilm from whole-genome sequences were extracted and analysed, and SNPs among the previously reported biofilm-related genes were analysed. Biofilm formation was significantly associated with SNPs of alpA, alpB, cagE, cgt, csd4, csd5, futB, gluP, homD, and murF (P < 0.05). Among the SNPs reported in alpB, strains encoding the N156K, G160S, and A223V mutations were high-biofilm formers.

CONCLUSIONS

This study revealed the potential role of SNPs in biofilm formation and proposed a method to detect mutation in biofilm from whole-genome sequences.

Mutations Related to Antibiotics Resistance in Helicobacter pylori Clinical Isolates from Bangladesh

Current management of gastric inflammation involves the eradication of Helicobacter pylori. However, the effectiveness of commonly used antibiotics against H. pylori infection has decreased due to antibiotic resistance. Phenotypic-based diagnostics are laborious and finding the cause of resistance can be difficult. Therefore, early detection and understanding of the underlying mechanism of this resistance are necessary. This study evaluated the mutations in the genes related to the Antimicrobial Resistance (AMR) of the clinical isolates from Bangladeshi subjects. Whole-genome sequencing was performed on 56 isolates and the genes (such as pbp1a, rdxA, ribF, fur, gyrA, gyrB, 23S rRNA, and infB) were extracted. The reads were assembled, and the SNPs were extracted by the latest pipeline for antibiotic mutation analysis, ARIBA. The mutations and the association with the antibiotic phenotypes were evaluated using Fisher's exact test. In this study, the clarithromycin resistance rate was high, 39.3% (22/56), with the median MIC 24 mg/L ranging from 2 to 128 mg/L. The mutation of A2147G was significantly associated with resistance (p = 0.000018) but not in locus A2146G (p = 0.056). Levofloxacin also posed a high resistance. We observed that the mutation of D91N (but not D91Y) (p = 0.002) and N87K (p = 0.002) of gyrA was associated with levofloxacin resistance. Mutations in locus A343V (p = 0.041) of gyrB also showed a significant association. Meanwhile, in the pbp1a gene, several mutations might explain the resistance; they were G594fs (p = 0.036), K306R (p = 0.036), N562Y (p = 0.0006), and V45I (p = 0.018). The prevalence of metronidazole was exceptionally high (96.4%), and numerous mutations occurred in rdxA genes, including the truncation of genes. These results imply that the mutation in genes encoding the target protein of antibiotics remains the critical resistance mechanism in H. pylori.

Bacterial exposure risk to the endoscopist's face while performing endoscopy

Objectives

Gastrointestinal endoscopy increases the risk of bacterial exposure to endoscopists. However, before 2019, most endoscopists did not pay attention to microorganism transmission from patients. This study aimed to investigate the incidence of bacterial exposure to endoscopists' faces during gastrointestinal endoscopic procedures using the bacterial culture method.

Methods

This was a single-centered, retrospective study including endoscopists who performed various gastrointestinal endoscopy procedures at the Division of Endoscopy, Hirosaki University Hospital between August 31 and October 6, 2020. Endoscopists wore surgical masks and affixed pre-sterilized films over them. Following the gastrointestinal endoscopic procedures, attached microbes were collected from the endoscopists' surface films using sterilized swabs. Collected microorganisms were cultured on tryptic soy agar and 5% sheep blood agar, and the incidence of bacterial exposure was determined by bacterial culture positivity. Cultured bacteria were identified by gram staining and 16S rRNA gene sequencing.

Results

Bacterial culture positivity was 12.6%, and it was significantly higher in therapeutic than in diagnostic endoscopy. Notably, therapeutic endoscopy increased bacterial culture positivity in colonoscopy, but not in esophagogastroduodenoscopy. Staphylococci, including Staphylococcus epidermidis and Staphylococcus capitis, were the most commonly found bacteria in samples identified through 16S rRNA gene sequencing.

Conclusions

The risk of bacterial exposure to the endoscopist's face was increased in colonoscopy treatment procedures. Therefore, endoscopists should be aware of the significant risk of microbial infection from scattering fluid that comes from the endoscopy's working channel.

Extracellular vesicles of Pseudomonas aeruginosa downregulate pyruvate fermentation enzymes and inhibit the initial growth of Staphylococcus aureus

Staphylococcus aureus and Pseudomonas aeruginosa are well-known opportunistic pathogens that frequently coexist in chronic wounds and cystic fibrosis. The exoproducts of P. aeruginosa have been shown to affect the growth and pathogenicity of S. aureus, but the detailed mechanisms are not well understood. In this study, we investigated the effect of extracellular vesicles from P. aeruginosa (PaEVs) on the growth of S. aureus. We found that PaEVs inhibited the S. aureus growth independently of iron chelation and showed no bactericidal activity. This growth inhibitory effect was also observed with methicillin-resistant S. aureus but not with Acinetobacter baumannii, Enterococcus faecalis, S. Typhimurium, E. coli, Listeria monocytogenes, or Candida albicans, suggesting that the growth inhibitory effect of PaEVs is highly specific for S. aureus. To better understand the detailed mechanism, the difference in protein production of S. aureus between PaEV-treated and non-treated groups was further analyzed. The results revealed that lactate dehydrogenase 2 and formate acetyltransferase enzymes in the pyruvate fermentation pathway were significantly reduced after PaEV treatment. Likewise, the expression of ldh2 gene for lactate dehydrogenase 2 and pflB gene for formate acetyltransferase in S. aureus was reduced by PaEV treatment. In addition, this inhibitory effect of PaEVs was abolished by supplementation with pyruvate or oxygen. These results suggest that PaEVs inhibit the growth of S. aureus by suppressing the pyruvate fermentation pathway. This study reported a mechanism of PaEVs in inhibiting S. aureus growth which may be important for better management of S. aureus and P. aeruginosa co-infections.

Differential proteomic analysis and pathogenic effects of outer membrane vesicles derived from Acinetobacter baumannii under normoxia and hypoxia

Acinetobacter baumannii is a major causative agent of nosocomial infections and its outer membrane vesicles (AbOMVs) have been shown to be involved in pathogenicity by transporting virulence factors and transferring information for communication between pathogens and host cells. Despite the fact that the infected sites of A. baumannii such as lungs and skin soft tissues are hypoxic, most studies on AbOMV virulence have used AbOMVs prepared under aerobic conditions. The present study aims to elucidate the protein profile and pathogenic impact of AbOMVs released under hypoxic condition. AbOMVs were isolated from A. baumannii under normoxic and hypoxic conditions, and their protein profiles were compared. The different effects of both normoxic and hypoxic AbOMVs in cytokine response from mouse macrophages, cytotoxicity to the human lung epithelial cells, and bacterial invasion were then investigated. Our results showed that A. baumannii under hypoxia released larger amounts of OMVs with different protein profiles. Although the cytotoxic effect of AbOMVs from normoxia and hypoxia were comparable, AbOMVs from normoxia induced higher TNF-α production and invasion of Staphylococcus aureus and Pseudomonas aeruginosa than those from hypoxia. On the other hand, AbOMVs significantly enhanced A. baumannii invasion into lung epithelial cells in a dose-dependent manner. These results clearly demonstrate that AbOMVs released from normoxic and hypoxic have different impacts in pathogenesis. This finding provides new insight into the complex interactions between A. baumannii, coinfecting pathogens and host cells via OMVs, in particular the different pathogenic effects of AbOMVs under normoxic and hypoxic conditions.

Next-Generation Sequencing-Based Study of Helicobacter pylori Isolates from Myanmar and Their Susceptibility to Antibiotics

Evaluation of Helicobacter pylori resistance to antibiotics is crucial for treatment strategy in Myanmar. Moreover, the genetic mechanisms involved remain unknown. We aimed to investigate the prevalence of H. pylori infection, antibiotic resistance, and genetic mechanisms in Myanmar. One hundred fifty patients from two cities, Mawlamyine (n = 99) and Yangon (n = 51), were recruited. The prevalence of H. pylori infection was 43.3% (65/150). The successfully cultured H. pylori isolates (n = 65) were tested for antibiotic susceptibility to metronidazole, levofloxacin, clarithromycin, amoxicillin, and tetracycline by Etest, and the resistance rates were 80%, 33.8%, 7.7%, 4.6%, and 0%, respectively. In the multidrug resistance pattern, the metronidazole–levofloxacin resistance was highest for double-drug resistance (16/19; 84.2%), and all triple-drug resistance (3/3) was clarithromycin–metronidazole–levofloxacin resistance. Twenty-three strains were subjected to next-generation sequencing to study their genetic mechanisms. Interestingly, none of the strains resistant to clarithromycin had well-known mutations in 23S rRNA (e.g., A2142G, A2142C, and A2143G). New type mutation genotypes such as pbp1-A (e.g., V45I, S/R414R), 23S rRNA (e.g., T248C), gyrA (e.g., D210N, K230Q), gyrB (e.g., A584V, N679H), rdxA (e.g., V175I, S91P), and frxA (e.g., L33M) were also detected. In conclusion, the prevalence of H. pylori infection and its antibiotic resistance to metronidazole was high in Myanmar. The H. pylori eradication regimen with classical triple therapy, including amoxicillin and clarithromycin, can be used as the first-line therapy in Myanmar. In addition, next-generation sequencing is a powerful high-throughput method for identifying mutations within antibiotic resistance genes and monitoring the spread of H. pylori antibiotic-resistant strains.

Extracellular vesicles from methicillin resistant Staphylococcus aureus stimulate proinflammatory cytokine production and trigger IgE-mediated hypersensitivity

Extracellular vesicles (EVs) released from bacteria are enclosed particles carrying biological active molecules. They have been shown to play a role in bacterial communications and delivery of virulence factors to the host cells. Staphylococcus aureus is an opportunistic pathogen causing a variety of infections ranging from impetigo to septicaemia. The EVs released from S. aureus have a high potential to be used for vaccine development against S. aureus infections. However, it is important to clearly understand the impact of SaEVs on the host’s immune response. Our study demonstrated that purified EVs from a clinical isolated methicillin-resistant S. aureus (SaEVs) significantly stimulated proinflammatory cytokine production in mouse immune cells and induced host cell death. An impairment of cytokine production in the Toll-like receptor (TLR)-silenced macrophages suggested that SaEVs stimulate proinflammatory response via TLRs 2, 4 and 9. In mouse infection model, the results demonstrated that SaEV immunization did not provide protective effect. In contrast, all SaEV-immunized mice died within Day 1 after methicillin-resistant S. aureus (MRSA) infection. After MRSA infection for 3 h, the production of IL-6, TNF-α and IL-17 in the spleen of SaEV-immunized mice was significantly higher than that of control mice. On Day 5 after the second immunization, total IgE in the serum was significantly enhanced, and a high titre of Th2-related cytokines was remarkably induced after ex vivo stimulation of the spleen cells with SaEVs. These results suggested that MRSA-derived EVs act as an immunostimulant that induces inflammatory response and IgE-mediated hypersensitivity after MRSA infection.

Serum Helicobacter pylori antibody reactivity in seven Asian countries using an automated latex aggregation turbidity assay

BACKGROUND AND AIM

To determine the application range of diagnostic kits utilizing anti-Helicobacter pylori antibody, we tested a newly developed latex aggregation turbidity assay (latex) and a conventional enzyme-linked immunosorbent assay (E-plate), both containing Japanese H. pylori protein lysates as antigens, using sera from seven Asian countries.

METHODS

Serum samples (1797) were obtained, and standard H. pylori infection status and atrophy status were determined by culture and histology (immunohistochemistry) using gastric biopsy samples from the same individuals. The two tests (enzyme-linked immunosorbent assay and latex) were applied, and receiver operating characteristics analysis was performed.

RESULTS

Area under the curve (AUC) from the receiver operating characteristic of E-plate and latex curves were almost the same and the highest in Vietnam. The latex AUC was slightly lower than the E-plate AUC in other countries, and the difference became statistically significant in Myanmar and then Bangladesh as the lowest. To consider past infection cases, atrophy was additionally evaluated. Most of the AUCs decreased using this atrophy-evaluated status; however, the difference between the two kits was not significant in each country, but the latex AUC was better using all samples. Practical cut-off values were 3.0 U/mL in the E-test and 3.5 U/mL in the latex test, to avoid missing gastric cancer patients to the greatest extent possible.

CONCLUSIONS

The kits were applicable in all countries, but new kits using regional H. pylori strains are recommended for Myanmar and Bangladesh. Use of a cut-off value lower than the best cut-off value is essential for screening gastric cancer patients.

Discovery of unique African Helicobacter pylori CagA-multimerization motif in the Dominican Republic

BACKGROUND

Helicobacter pylori (H. pylori) colonizes the human stomach and is a major cause of peptic ulcer disease and gastric cancer. However, although the prevalence of H. pylori is high in Africa, the incidence of gastric cancer is low, and this phenomenon is called to be African enigma. The CagA protein produced by H. pylori is the most studied virulence factor. The carcinogenic potential of CagA is associated with the Glu-Pro-Ile-Tyr-Ala (EPIYA) patterns and CagA-multimerization (CM) motifs.

AIM

To better understand the EPIYA patterns and CM motifs of the cagA gene.

METHODS

Gastric mucosal biopsy specimens were obtained from 258 patients with dyspepsia living in the Dominican Republic, from which 120 H. pylori strains were cultured. After the bacterial DNA extraction, the EPIYA pattern and CM motif genotypes were determined using a polymerase chain reaction-based sequencing. The population structure of the Dominican Republic strains was analyzed using multilocus sequence typing (MLST). Peptic ulcer disease and gastric cancer were identified via endoscopy, and gastric cancer was confirmed by histopathology. Histological scores of the gastric mucosa were evaluated using the updated Sydney system.

RESULTS

All CagA-positive strains carried the Western-type CagA according to the identified EPIYA patterns. Twenty-seven kinds of CM motifs were observed. Although the typical Western CM motif (FPLKRHDKVDDLSKVG) was observed most frequently, the typical East Asian CM motif (FPLRRSAAVNDLSKVG) was not observed. However, “FPLRRSAKVEDLSKVG”, similar to the typical East Asian CM motif, was found in 21 strains. Since this type was significantly more frequent in strains classified as hpAfrica1 using MLST analysis (P = 0.034), we termed it Africa1-CM (Af1-CM). A few hpEurope strains carried the Af1-CM motif, but they had a significantly higher ancestral Africa1 component than that of those without the Af1-CM motif (P = 0.030). In 30 cagA-positive strains, the "GKDKGPE" motif was observed immediately upstream of the EPIYA motif in the EPIYA-A segment, and there was a significant association between strains with the hpAfrica1 population and those containing the “GKDKGPE” motif (P = 0.018). In contrast, there was no significant association between the CM motif patterns and histological scores and clinical outcomes.

CONCLUSION

We found the unique African CM motif in Western-type CagA and termed it Africa1-CM. The less toxicity of this motif could be one reason to explain the African enigma.

Serum pepsinogens as a gastric cancer and gastritis biomarker in South and Southeast Asian populations

Serum pepsinogens have been widely acknowledged as gastric mucosal biomarkers; however, a multicountry report on the benefits of pepsinogens as biomarkers has not yet been published. We analyzed 1,206 sera and gastric mucosal samples collected from Bangladesh, Bhutan, Indonesia, Myanmar, Nepal and Thailand then assessed the association between gastric mucosal changes and Helicobacter pylori infection. The new cutoff values for serum pepsinogen values were evaluated using a receiver operating characteristic analysis. The participants with H. pylori infection had significantly lower pepsinogen I and higher pepsinogen II values, but a lower pepsinogen I/II ratio than participants without the infection (all P < .001). The pepsinogen I and pepsinogen I/II values were significantly higher and lower, respectively, in individuals with atrophic gastritis than in those without (both P < .001). Among uninfected individuals, only the pepsinogen I/II ratio was significantly lower in atrophic individuals. Pepsinogen I/II ratio also were significantly different between disease among H. pylori-positive and H. pylori-negative individuals, suggesting the pepsinogen I/II ratio is a robust biomarker for determining both chronic and atrophic gastritis. The cutoffs for detecting chronic and atrophic gastritis for the pepsinogen I/II ratio were 4.65 and 4.95, respectively. In conclusion, pepsinogen levels are useful biomarker for both chronic gastritis and atrophic gastritis, but they should be used with caution. Population-based validation is necessary to determine the best cutoff values. Among all pepsinogen values, the pepsinogen I/II ratio was the most reliable gastric mucosal-change biomarker.

Comparative study between Helicobacter pylori and host human genetics in the Dominican Republic

Background

Helicobacter pylori, a bacterium that infects the human stomach, has high genetic diversity. Because its evolution is parallel to human, H. pylori is used as a tool to trace human migration. However, there are few studies about the relationship between phylogeography of H. pylori and its host human.

Methods

We examined both H. pylori DNA and the host mitochondrial DNA and Y-chromosome DNA obtained from a total 119 patients in the Dominican Republic, where human demography consists of various ancestries. DNA extracted from cultured H. pylori were analyzed by multi locus sequence typing. Mitochondrial DNA and Y-chromosome DNA were evaluated by haplogroup analyses.

Results

H. pylori strains were divided into 2 populations; 68 strains with African group (hpAfrica1) and 51 strains with European group (hpEurope). In Y-chromosomal haplogroup, European origin was dominant, whereas African origin was dominant both in H. pylori and in mtDNA haplogroup. These results supported the hypothesis that mother-to-child infection is predominant in H. pylori infection. The Amerindian type of mtDNA haplogroup was observed in 11.8% of the patients; however, Amerindian type (hspAmerind) of H. pylori was not observed. Although subpopulation type of most hpAfrica1 strains in Central America and South America were hybrid (hspWAfrica/hpEurope), most Dominican Republic hpAfrica1 strains were similar to those of African continent.

Conclusions

Genetic features of H. pylori, mtDNA, and Y haplogroups reflect the history of colonial migration and slave trade in the Dominican Republic. Discrepancy between H. pylori and the host human genotypes support the hypothesis that adaptability of hspAmerind H. pylori strains are weaker than hpEurope strains. H. pylori strains in the Dominican Republic seem to contain larger proportion of African ancestry compared to other American continent strains.

Western-Type Helicobacter pylori CagA are the Most Frequent Type in Mongolian Patients

Helicobacter pylori infection possessing East-Asian-type CagA is associated with carcinogenesis. Mongolia has the highest mortality rate from gastric cancer. Therefore, we evaluated the CagA status in the Mongolian population. High risk and gastric cancer patients were determined using endoscopy and histological examination. H. pylori strains were isolated from different locations in Mongolia. The CagA subtypes (East-Asian-type or Western-type, based on sequencing of Glu-Pro-Ile-Tyr-Ala (EPIYA) segments) and vacA genotypes (s and m regions) were determined using PCR-based sequencing and PCR, respectively. In total, 368 patients were examined (341 gastritis, 10 peptic ulcer, and 17 gastric cancer). Sixty-two (16.8%) strains were cagA-negative and 306 (83.1%) were cagA-positive (293 Western-type, 12 East-Asian-type, and one hybrid type). All cagA-negative strains were isolated from gastritis patients. In the gastritis group, 78.6% (268/341) had Western-type CagA, 2.9% (10/341) had East-Asian-type, and 18.2% (61/341) were cagA-negative. However, all H. pylori from gastric cancer patients possessed Western-type CagA. Histological analyses showed that East-Asian-type CagA was the most virulent strains, followed by Western-type and cagA-negative strains. This finding agreed with the current consensus. CagA-positive strains were the most virulent type. However, the fact that different CagA types can explain the high incidence of gastric cancer might be inapplicable in Mongolia.

Five alternative Helicobacter pylori antibiotics to counter high levofloxacin and metronidazole resistance in the Dominican Republic

The prevalence of Helicobacter pylori resistance to levofloxacin and metronidazole was high in the Dominican Republic. We used two-fold agar dilution method to determine the minimum inhibitory concentration of five alternative antibiotics in 63 Dominican strains. We also assessed the genetic mutations associated with the antibiotic resistance using next-generation sequencing. We revealed that all 63 strains were sensitive towards sitafloxacin, furazolidone, and rifabutin. In contrast, the prevalence of rifaximin and garenoxacin resistance were high (82.5% and 34.9%, respectively). Patients more than or equal to 60 years old had the highest risk of double-antibiotic resistance (7/9, 77.8%, OR = 31.5, P = 0.009) and garenoxacin resistances (8/9, 88.9%, OR = 45.33, P = 0.002) with an increasing risk simultaneously by age (P = 0.004, r = 0.357). Almost all rifaximin resistant strains possessed multiple mutations with more than three mutations within rpoB including the most frequent novel mutations of S352L, I2726L, and V2465A. There was a significant association between vacA genotype and rifaximin resistance (P = 0.042). Among 23 levofloxacin-resistant strains, 82.6% (19/23, P <0.001) were also resistant to garenoxacin, and 39.1% (9/23) had a high minimal inhibitory concentration ≥8 μg/mL with positive trend correlation (P = <0.001, r = 0.84). Among 19 garenoxacin resistant strains, 16 (84.2%) contained mutations at D91 and N87 of gyrA. In conclusion, sitafloxacin, rifabutin, and furazolidone might be considered as alternative antibiotics to be included in H. pylori eradication regimen in regions with high prevalence of levofloxacin and metronidazole resistance, such as the Dominican Republic.

Effective therapeutic regimens in two South Asian countries with high resistance to major Helicobacter pylori antibiotics

Background

Nepal and Bangladesh have a high prevalence of Helicobacter pylori with high resistance rates to clarithromycin, metronidazole, and levofloxacin. Here, we evaluated the susceptibility and genetic mutations of 5 alternative antibiotics against isolates from both countries to obtain an effective treatment regimen for H. pylori eradication.

Methods

We used the agar dilution method to determine the minimal inhibitory concentration of 5 alternative antibiotics against 42 strains from Nepal and 56 from Bangladesh and performed whole genome mutation analysis.

Results

No resistance to furazolidone or rifabutin and a high susceptibility of sitafloxacin (95.2% in Nepal and 98.2% in Bangladesh) were observed. In contrast, resistance to rifaximin (52.4% in Nepal and 64.3% in Bangladesh) was high. Moreover, resistance to garenoxacin was higher in Bangladesh (51.6%) than in Nepal (28.6%, P = 0.041), most likely due to its correlation with levofloxacin resistance (P = 0.03). Garenoxacin and rifaximin were significantly correlated in Bangladesh (P = 0.014) and occurred together with all sitafloxacin-resistant strains. Mutations of gyrA could play a significant role in garenoxacin resistance, and double mutations of A87 and D91 were associated with sitafloxacin resistance. Analysis of the rpoB gene demonstrated well-known mutations, such as V657I, and several novel mutations, including I2619V, V2592 L, T2537A, and F2538 L.

Conclusions

Rifabutin can be cautiously implemented as therapy for H. pylori infection due to its interaction with the tuberculosis endemic in Bangladesh. The high susceptibility of furazolidone and sitafloxacin suggests their possible future application in Nepal and Bangladesh.

Validation of diagnostic tests and epidemiology of Helicobacter pylori infection in Bangladesh

INTRODUCTION

Helicobacter pylori infection is associated with gastritis, peptic ulcer, and gastric cancer. We conducted a cross-sectional study to compare five diagnostic tests for H. pylori infection and studied the epidemiology of the infection in Bangladesh.

METHODOLOGY

Bangladeshi patients with dyspeptic symptoms referred for endoscopic examination were enrolled in this study. Each patient underwent upper endoscopic examination and four gastric biopsy specimens were taken. We used 5 tests for the diagnosis of H. pylori; culture, histology confirmed by immunohistochemistry, rapid urease test (RUT), urinary and serological test. Demographic and environmental variables were collected.

RESULTS

A total of 133 patients participated in the study, 61 males and mean age 37.3 ± 12.3 years. We used the culture and/or histology results as the gold standard to estimate the sensitivity, specificity, positive and negative predictive values for the studied diagnostic tests. RUT, culture and histology had high sensitivity and specificity with moderate positive and negative likelihood ratio, whereas urine test and serology showed a good sensitivity and specificity but poor likelihood ratio. The overall prevalence of H. pylori among study subjects was 47% with no difference between gender and age groups.

CONCLUSIONS

The invasive tests showed better performance than noninvasive tests among Bangladeshi population. The overall prevalence of H. pylori was less than the previously reported in the region with no difference among all age groups.

Distribution and clinical associations of integrating conjugative elements and cag pathogenicity islands of Helicobacter pylori in Indonesia

The clinical associations and correlations with other virulence factors such as cag pathogenicity island (PAI) of the Integrating Conjugative Elements Helicobacter pylori TFSS (ICEHptfs), a new type IV secretion system (TFSS) in H. pylori has not been described. Among 103 studied strains from Indonesia, almost all strains (99.0%) contained cag PAI with more than half (55.8%) were intact cag PAI. Patients infected with intact cag PAI strains showed significantly higher antral activity, inflammation and atrophy as well as corporal inflammation than those with non-intact cag PAI strains, confirming the virulence of cag PAI. Over half of strains (53.8%) contained ICEHptfs, predominantly consisted of ICEHptfs3-tfs4a (42.8%) and ICEHptfs3 (16.3%). Although patients infected with ICEHptfs-positive strains had lower H. pylori density, those with the complete ICEHptfs4b strains tended to have higher antral activity than the negative one. In combination, patients infected with combination of intact cag PAI-ICEHptfs-positive strains had more severe inflammation than those with non-intact cag PAI-ICEHptfs-negative, suggesting a possibility of a mutual correlation between these TFSS(s).

Characterizing Helicobacter pylori cagA in Myanmar

BACKGROUND/AIMS

Differences in the Helicobacter pylori infection rate are not sufficient to clarify the dissimilarity of gastric cancer incidence between Myanmar and its neighboring countries. To better understand this trend, the H. pylori virulence gene cagA was characterized in Myanmar.

METHODS

Glutamate-proline-isoleucine-tyrosine-alanine (EPIYA) patterns and CagA multimerization (CM) motifs of cagA genotypes were examined by performing polymerase chain reactions and DNA sequencing.

RESULTS

Of 69 tested H. pylori strains, cagA-positive patients had significantly more severe histological scores in their antrum than cagA-negative patients. Sequence analysis revealed that 94.1% of strains had Western-type cagA containing an EPIYA motif (92.6%) or EPIYT motif (6.4%). The intestinal metaplasia scores in the antral of patients infected with the ABC and ABCC types of cagA were significantly higher than those of patients with AB-type cagA. Interestingly, in patients infected with H. pylori, 46.3% of strains with three EPIYA motifs contained two identical Western-typical CM motifs, and these patients showed significantly higher antrum inflammation scores than patients infected with two identical nontypical-CM motif strains (p=0.02).

CONCLUSIONS

In Myanmarese strains, Western-type cagA was predominant. The presence of CM motifs and the proportion of multiple EPIYA-C segments might partially explain the intermediate gastric cancer risk found in Myanmar.

Helicobacter pylori bab characterization in clinical isolates from Bhutan, Myanmar, Nepal and Bangladesh

BACKGROUND

Helicobacter pylori BabA is an important outer membrane protein that involves in the attachment to the gastric mucosa and enhances the virulence property of the bacterium. This study was aimed to characterize the bab genotypes, to evaluate its association with cagA, vacA and clinical diseases as well as degree of gastric inflammation.

METHODS

H. pylori isolates from four countries were subjected for the characterization of bab. The locus specific forward and bab specific reverse primers were used to get the specific products by PCR, which could distinguish the three locus (A, B and C). The histological activities were evaluated according to the Updated Sydney system.

RESULT

In patients from high risk countries (Bhutan and Myanmar) relatively higher frequencies of strains with babA-positivity (91.8% and 90.7%, respectively), babA at locus A (98% and 91.2%, respectively) and with single babA (96.8% and 91.2%, respectively) were found. Strains with two loci occupied were the most prevalent in Bhutan (84.6%), Myanmar (74.7%), Nepal (58.3%) and Bangladesh (56.9%). The genotype babA at locus A/babB at locus B/bab-negative at locus C (babA/babB/-) was the most common genotype isolated from Bhutan (82.7%), Myanmar (58.7%), Nepal (32%) and Bangladesh (31.4%) among all genotypes assessed. This genotype was also associated with the peptic ulcer disease (P = 0.013) when compared to gastritis. babA-positive characteristics and the genotype babA/babB/- exhibited the enhanced histological activities.

CONCLUSIONS

The higher prevalence of virulence associated babA-positive characteristics and enhanced histological activities in Bhutan than in Myanmar, Nepal and Bangladesh might partly explain why the peoples in Bhutan are at higher risk for developing severe gastric complications.

Prevalence, risk factors, and virulence genes of Helicobacter pylori among dyspeptic patients in two different gastric cancer risk regions of Thailand

Gastric cancer risk is varied among different regions of Thailand. We examined the characteristics of Helicobacter pylori infection in two regions of Thailand. The H. pylori status of 273 dyspeptic patients (136 from the South and 137 from the North; a low and high incidence of gastric cancer region, respectively) was evaluated, and virulence genotypes (cagA, vacA, hrgA and jhp0562-positive/β-(1,3)galT) were determined. The overall H. pylori infection rate was 34.1% (93/273). The prevalence was higher in the North than in the South (50.4% vs. 17.6%, P <0.001) and was significantly higher among individuals with the following characteristics: low income, birthplace in the Northeast or North regions, agricultural employment, or consumption of alcohol or unboiling water. Among these socio-demographic determinants, region was an independent risk factor for H. pylori infection (odds ratio = 6.37). Patients including both H. pylori infected and uninfected cases who lived in the North had significantly more severe histological scores than those in the South. In contrast, among H. pylori-positive cases, patients in the South had significantly more severe histological scores than those in the North. Of the 74 strains cultured, 56.8% carried Western-type cagA, with a higher proportion in the South than in the North (76.2% vs. 49.1%, P = 0.05). In disagreement with the current consensus, patients infected with the Western-type cagA strains had more severe inflammation scores in the antrum than those infected with the East Asian-type cagA strains (P = 0.027). Moreover, Western-type cagA strains induced more severe histological scores in patients from the South than those of either genotype from the North. Other virulence genes had no influence on histological scores. The incidence of gastric cancer in Thailand was different among regions and corresponded to differences in the prevalence of H. pylori infection. More careful follow-up for patients in the South will be required, even if they are infected with H. pylori carrying Western-type cagA.

Nepalese Helicobacter pylori Genotypes Reflects a Geographical Diversity than a True Virulence Factor

Background:

The data about the association between Helicobacter pylori putative virulence factors; iceA and jhp0562/β-(1,3)galT with clinical outcomes are still controversial. We identified and analyzed two putative H. pylori virulence factors in Nepalese strains.

Methods:

The iceA and jhp0562/β-(1,3)galT allelic types were determined by polymerase chain reaction amplification. Histological analysis were classified according to the updated Sydney system and the Operative Link on Gastritis Assessment (OLGA) system.

Results:

Among 49 strains, iceA1 negative/iceA2 positive (iceA2-positive) was predominant type (57.1%, 28/49) and 20 (40.8%) were iceA1 positive/iceA2 negative. The remaining one (2.0%) was positive for both iceA1 and iceA2 (iceA1/iceA2-mixed). Patients infected with iceA1-positive strains tended to be higher OLGA score than iceA2-positive strains [1.45 [1] vs. 0.07 [0.5], P = 0.09, respectively). The jhp0562 negative/β-(1,3)galT positive was predominant type (25/51, 49.0%), followed by double positive for jhp0562/β-(1,3)galT (15/51, 29.4%) and jhp0562 positive/β-(1,3)galT negative (11/51, 21.6%). Activity in the corpus was significantly higher in jhp0562 negative/β-(1,3)galT positive than double positive of jhp0562/β-(1,3)galT positive [mean (median); 1.24 (1) vs. 0.73 (1), P = 0.03]. There was association between iceA and subtype of vacA signal region (e.g., s1a, s1b or s1c) and combination subtypes of signal and middle regions (e.g., s1a-m1c) (P = 0.02, r = 0.29; and P = 0.002, r = 0.42, respectively). In addition, jhp0562/β-(1,3)galT genotypes associated with cagA pre-EPIYA type (e.g., 6 bp-, 18 bp-, or no deletion-type) (P = 0.047, r = 0.15).

Conclusion:

The inconsistency results of the association between iceA, jhp0562/β-(1,3)galT and histological scores suggesting that these genes may associate with genetic heterogeneity rather than as a true virulence factor.

Two populations of less-virulent Helicobacter pylori genotypes in Bangladesh

Bangladesh has a population with a low gastric cancer risk but high prevalence of Helicobacter pylori infection. Several studies have examined virulence genes in H. pylori from Bangladesh. We analyzed cagA and vacA subtypes and their association with severe histology phenotypes, and analyzed population types among Bangladeshi strains. We included patients who underwent endoscopy in Dhaka. Sequences of virulence genes and seven housekeeping genes were obtained by next generation sequencing and confirmed by Sanger sequencing. We isolated 56 H. pylori strains from 133 patients, of which 73.2% carried cagA, and all were considered Western-type. Patients infected with cagA-positive strains had more severe histological scores than patients infected with cagA-negative strains. Among vacA s1 and m1 genotypes, the s1a (97.8%, 43/44) and m1c (28/30, 93.3%) genotypes were predominant. All strains containing s1 and m1 (30/56, 53.6%) also had i1, d1, and c1. In contrast, all strains containing the less-virulent genotypes s2 and m2 (12/56, 21.4%) also possessed i2, d2, and c2. Multivariate analysis indicated that subjects infected with vacA m1-genotype strains only had a significantly higher risk of antrum atrophy than patients infected with m2-genotype strains. Of the two main H. pylori populations in this study, hpAsia2 strains were associated with higher activity and inflammation in the antrum compared to hpEurope strains; however, only vacA s1m1i1d1c1 strains, independent of population type, were significantly associated with inflammation in the antrum, unlike the s2m2i2d2c2 genotype. In conclusion, Bangladeshi strains were divided into two main populations of different genotypes. The low incidence of gastric cancer in Bangladesh might be attributable to the high proportion of less-virulent genotypes, which may be a better predictor of gastric cancer risk than the ancestral origin of the H. pylori strains. Finally, the vacA m region may be a better virulence marker than other regions.

Clarithromycin-Based Triple Therapy is Still Useful as an Initial Treatment for Helicobacter pylori Infection in the Dominican Republic

AbstractHelicobacter pylori antibiotic susceptibility in the Dominican Republic has not been monitored. We assessed H. pylori antibiotic susceptibility in the Dominican Republic, and analyzed H. pylori mutations associated with antibiotic resistance. We recruited 158 dyspeptic patients in Santo Domingo and used agar dilution to test susceptibility to five antibiotics. Polymerase chain reaction-based sequencing was used to assess gyrA, gyrB, rdxA, frxA, and 23S rRNA mutations; next-generation sequencing was used to identify other metronidazole resistance-associated genes. Among 64 H. pylori strains isolated, we identified two (3.1%), one (1.6%), and no strains with clarithromycin, amoxicillin, and tetracycline resistance, respectively. Moreover, high frequency of metronidazole resistance (53/64, 82.8%) was observed, whereas levofloxacin resistance is emerging (23/64, 35.9%). We identified many rdxA and frxA mutations in metronidazole-resistant strains, but no synergistic effect was apparent. We revealed novel mutations in dppA, dppB, fdxA, and fdxB, irrespective of rdxA and frxA mutations. Novel mutations at Ser-14 of trx1 and Arg-221 of dapF were associated with different levels of metronidazole resistance. Most levofloxacin-resistant strains had a substitution at Asn-87 of gyrA, including the strain with the highest levofloxacin resistance, whereas only three substitutions were found at Ser-479 of gyrB with no synergistic effect. Besides the 23S rRNA A2142G mutation, we observed another mutation at T1958G in both clarithromycin-resistant strains. We confirmed high metronidazole and levofloxacin resistance associated with genetic mutations in the Dominican Republic. However, prevalence of clarithromycin resistance was low, suggesting that standard clarithromycin-based triple therapy remains useful as initial treatment of H. pylori infection.

High Fluoroquinolone Resistant Strains of Helicobacter pylori in the Golden triangle

Background and aims:

Helicobacter pylori (H. pylori) infections, associated with fatal GI diseases such as gastric cancer and MALT lymphoma, remain a major health problem in ASEAN countries. The Golden triangle has long been known as one of Asia’s main opium-producing areas. There have been no prior studies of H. pylori infection in this area. The major objectives of this project were therefore to establish prevalence, antibiotic resistance patterns and associated predictive in the Golden triangle.

Methods:

We recruited dyspeptic patients in Chiang khong and Chiang saen districts, Chiangrai province of Thailand. All subjects underwent gastroscopy, and 3 antral gastric biopsies were collected for rapid urease tests and H. pylori culture. E-tests were used to evaluate the MICs for metronidazole (MNZ), levofloxacin (LVX), ciprofloxacin (CIP), amoxicillin(AMX), tetracycline (TET) and clarithromycin (CLR).

Results:

Total of 148 patients was included. H. pylori infection was present in 36.3%(37/102) of Chiang khong and 34.8 % (16/46) of Chiang saen subjects and the overall H. pylori infection rate was 35.8% (53/148). Antibiotic resistance was demonstrated in 44%, including 2% for CLR and 26% for MNZ, whereas fluoroquinolone resistance was demonstrated to be as high as 25% in Chiang khong. Multi-drug resistant H. pylori was detected in 4%. There was no AMX and TET resistance in this study. The prevalence of CLR resistance on a background of gastritis was significantly higher than peptic ulcer disease in the golden triangle area (100%vs 0%: P= 0.04).

Conclusions:

H. pylori remains a common infection in the Golden triangle. MNZ resistance appears to be high, whereas fluoroquinolone resistance is prevalent and is becoming a significant problem in this area. Diagnosis of gastritis might be a predictor of CLR resistance in the Golden triangle. H. pylori eradication with an appropriate regimen by using the local antibiotic resistant pattern is a key important tool to reduce H. pylori associated GI diseases in this particular part of the world.

Emerging Helicobacter pylori levofloxacin resistance and novel genetic mutation in Nepal

Background

The prevalence of Helicobacter pylori antibiotic susceptibility in the Nepalese strains is untracked. We determined the antibiotic susceptibility for H. pylori and analyzed the presence of genetic mutations associated with antibiotic resistance in Nepalese strains.

Results

This study included 146 consecutive patients who underwent gastroduodenal endoscopy in Kathmandu, Nepal. Among 42 isolated H. pylori, there was no resistance to amoxicillin and tetracycline. In contrast, similar with typical South Asian patterns; metronidazole resistance rate in Nepalese strains were extremely high (88.1 %, 37/42). Clarithromycin resistance rate in Nepalese strains were modestly high (21.4 %, 9/42). Most of metronidazole resistant strains had highly distributed rdxA and frxA mutations, but were relative coincidence without a synergistic effect to increase the minimum inhibitory concentration (MIC). Among strains with the high MIC, 63.6 % (7/11) were associated with frameshift mutation at position 18 of frxA with or without rdxA involvement. However, based on next generation sequencing data we found that one strain with the highest MIC value had a novel mutation in the form of amino acid substituted at Ala-212, Gln-382, Ile-485 of dppA and Leu-145, Thr-168, Glu-117, Val-121, Arg-221 in dapF aside from missense mutations in full-length rdxA. Mutations at Asn-87 and/or Asp-91 of the gyrA were predominantly in levofloxacin-resistant strains. The gyrB mutation had steady relationship with the gyrA 87–91 mutations. Although three (44.4 %) and two (22.2 %) of clarithromycin resistant strains had point mutation on A2143G and A2146G, we confirmed the involvement of rpl22 and infB in high MIC strains without an 23SrRNA mutation.

Conclusions

The rates of resistance to clarithromycin, metronidazole and levofloxacin were high in Nepalese strains, indicating that these antibiotics-based triple therapies are not useful as first-line treatment in Nepal. Bismuth or non-bismuth-based quadruple regimens, furazolidone-based triple therapy or rifabutin-based triple therapy may become alternative strategy in Nepal.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0873-6) contains supplementary material, which is available to authorized users.

Helicobacter pylori antibiotic susceptibility patterns in Bangladesh: Emerging levofloxacin resistance

INTRODUCTION

The most recent study to report Helicobacter pylori antibiotic resistance rates in Bangladesh was published 15 years ago and did not include levofloxacin. We therefore aimed to determine the current antibiotic susceptibility of H. pylori to amoxicillin, clarithromycin, metronidazole, tetracycline and levofloxacin in Bangladesh.

METHODOLOGY

This study included 133 consecutive patients who underwent endoscopy examination at Dhaka Medical College in November 2014. The serial two-fold agar dilution method was used to determine the minimum inhibitory concentrations of the five antibiotics.

RESULTS

Among 56 cultured strains, H. pylori showed high rates of resistance to clarithromycin and metronidazole (39.3% and 94.6%, respectively). Moreover, levofloxacin showed an emerging antimicrobial resistance pattern (66.1%), which was higher in patients with gastritis than that in those with peptic ulcers (p = 0.02). The resistance rate of levofloxacin was significantly higher in patients living in Dhaka city compared to those living in the village (p = 0.049). However, amoxicillin and tetracycline resistance rates were very low. Resistance to both metronidazole and levofloxacin was most commonly observed.

CONCLUSIONS

The rates of resistance to clarithromycin, metronidazole, and levofloxacin were high in Bangladesh, which suggests that triple therapy based on these drugs may not be useful as first-line therapies in Bangladesh. Alternative strategies such as furazolidone-based triple therapy, bismuth-based quadruple therapies, or sequential therapy may be more effective for patients in in Bangladesh.

Helicobacter pylori virulence genes in the five largest islands of Indonesia

Background

It remains unclear whether the low incidence of gastric cancer in Indonesia is due to low infection rates only or is also related to low Helicobacter pylori pathogenicity. We collected H. pylori strains from the five largest islands in Indonesia and evaluated genetic virulence factors.

Methods

The genotypes of H. pylori virulence factors were determined by polymerase chain reaction (PCR)-based sequencing. Histological severity of the gastric mucosa was classified into 4 grades, according to the updated Sydney system.

Results

A total of 44 strains were analyzed. Forty-three (97.7 %) were cagA-positive: 26 (60.5 %) were East-Asian-type-cagA, 9 (20.9 %) were Western-type-cagA, and 8 (18.6 %) were novel ABB-type, most of which were obtained from Papuan. EPIYT sequences were more prevalent than EPIYA sequences (P = 0.01) in the EPIYA-B motif of all types of cagA. The majority of cagA-positive strains (48.8 %, 21/43) had a 6-bp deletion in the first pre-EPIYA region. Subjects infected with East-Asian-type-cagA strains with a 6-bp deletion had significantly lower inflammation and atrophy scores in the corpus than those infected with Western-type-cagA strains (both P = 0.02). In total, 70.4 % of strains possessed the vacA s1m1 genotype and 29.5 % were m2. All strains from peptic ulcer patients were of the iceA1 genotype, which occurred at a significantly higher proportion in peptic ulcer patients than that in gastritis patients (55.3 %, P = 0.04). The double positive genotype of jhp0562/β-(1,3)galT was predominant (28/44, 63.6 %), and subjects infected with this type had significantly higher inflammation scores in the corpus than those with the jhp0562 negative/β-(1,3)galT positive genotype (mean [median]; 1.43 [1] vs. 0.83 [1], P = 0.04). There were significant differences in cagA and pre-EPIYA cagA type, oipA status, and jhp0562/β-(1,3)galT type among different ethnic groups (P < 0.05).

Conclusions

In addition to a low H. pylori infection rate, the low incidence of gastric cancer in Indonesia might be attributed to less virulent genotypes in predominant strains, which are characterized by the East-Asian-type-cagA with a 6-bp deletion and EPIYT motif, a high proportion of m2, dupA negative or short type dupA, and the jhp0562/β-(1,3)galT double positive genotype.