上海市某三甲医院幽门螺杆菌耐药性和毒力与其生物膜形成能力的相关性研究

为探讨复旦大学附属华东医院(以下简称本院)分离培养的幽门螺杆菌(Helicobacter pylori,H. pylori)的耐药性、毒力和感染特征与其生物膜形成能力的相关性,收集2014年12月-2015年6月于本院消化内镜中心的胃活检组织标本及相应临床病例资料,分离培养获得幽门螺杆菌,分析菌株的耐药性、毒力基因型、临床病例特征。结果显示,从胃活检组织样本中共分离培养28株幽门螺杆菌,对左氧氟沙星(levofloxacin,LEV)、甲硝唑(metronidazole,MTZ)和克拉霉素(clarithromycin,CLA)的耐药率分别为32%、75%和11%,未发现阿莫西林(amoxicillin,AMX)耐药。单一药物耐药17株(17/28,61%),双重耐药10株(10/28,36%)。毒力基因cagA、oipA和vacAs1检出率为100%,未检出vacAs2。基因型vacAs1m1占39%(11/28),vacAs1m2占61%(17/28);iceA1占54%(15/28),iceA2占21%(6/28),iceA1A2占25%(7/28);dupA^＋占36%(10/28)。28株菌株均能形成生物膜,但能力不尽相同。单因素及独立样本t检验分析显示,45～59岁、iceA1^＋dupA^－基因型和甲硝唑敏感菌株形成生物膜的能力较强。结果提示,本院分离的幽门螺杆菌对甲硝唑耐药率最高,双重耐药不容忽视。菌株主要毒力基因型为cagA、oipA、vacAs1m2。幽门螺杆菌的生物膜形成能力与患者年龄有关,45～59岁组较强;携带毒力基因iceA1的菌株生物膜形成能力强;dupA基因型及甲硝唑耐药与菌株生物膜形成呈负相关。     

Prevalence of cagA, vacA, babA2 and iceA genes in H. pylori strains isolated from Colombian patients with functional dyspepsia

The clinical outcome of Helicobacter pylori infection has been particularly associated with virulence genotypes. These genotypes are useful as molecular markers in the identification of patients that are infected and at high risk for developing more severe gastric pathologies. Our main objective was to determine the prevalence of virulence genotypes cagA, vacA, iceA and babA2 of H. pylori, in patients with functional dyspepsia who are infected with the bacteria. H. pylori genotypes babA2 and cagA as well as vacA and iceA allelic variants were identified by PCR in 122 isolates resulting from 79 patients with functional dyspepsia. A high prevalence of genes cagA+ (71%), vacAs1am1 (34%), babA2 (57%) and iceA1 (87%) was found. The most frequent combined genotype found were cagA+/vacAs1am1/babA2+/iceA1 and cagA-/vacAs1am1/babA2+/iceA1, regardless of any family history of gastric cancer or MALT lymphoma. The very virulent genotype cagA+/vacAs1am1/babA2+/iceA1 prevailed in the studied patients with functional dyspepsia. Our results provide information about the prevalence of four of the more important virulent factors and constitute new evidence on the prevalence of the most virulent H. pylori genotype in patients with functional dyspepsia.     

幽门螺杆菌毒力基因型与胃癌的相关性研究

目的:研究中国东部地区幽门螺杆菌(H.pylori)cagA、vacA和iceA1毒力基因型的分布状况及其与胃癌的相关性。方法:从52例病人胃黏膜活检组织(31例慢性浅表性胃炎,21例胃癌)中分离培养H.pylori,用PCR方法扩增分离菌株的cagA、iceA1、vacAs,i,m区毒力基因片段,统计并分析上述毒力因素与胃癌发生的相关性。结果:在52例菌株中,cagA、vacAs1/i1/m1、vacAs1/i1/m2和iceA1的阳性率分别是92.3%(48/52),48.1%(25/52),48.1%(25/52),90.4%(47/52);所有的胃癌分离株中均为cagA(+)vacAs1/i1(+)型,vacAm1、vacAm2和iceA1在胃癌组中的阳性率分别是47.6%(10/21),52.4%(11/21),95.2%(20/21),与胃炎组相比,上述基因型的阳性率差异均无显著统计学意义(P>0.05)。结论:cagA、vacAs1/i1/m1、vacAs1/i1/m2和iceA1是中国东部地区H.pylori的优势基因型;cagA、vacAs1、vacAi1和iceA1毒力基因型的存在与胃癌的发生无相关性。     

HIV protease inhibitors attenuate adherence of Candida albicans to epithelial cells in vitro

The cagA gene is a key marker for the Helicobacter pylori cag pathogenicity island (PAI), which may vary in composition in different strains with insertion sequence mediated interruptions and deletions of genes. While presence of cagA has been associated with increased risk for peptic ulcer disease and gastric cancer, the precise link with virulence is controversial. We investigated H. pylori from dyspeptics in one location in England (mid-Essex) with reference to the prevalence and distribution by age cohort of different cag PAI forms to determine if presence of the insertion element IS605 had a modifying effect on the severity of associated disease. H. pylori isolated from gastric biopsies over a 4-year period were screened by specific PCR assays for the presence of cagA, cagD, cagE and virD4 genes in the cag PAI, and for the presence of IS605 in the PAI and elsewhere in the genome. Most (68%) of the 166 isolates of H. pylori contained a PAI based on detection of cagA whereas 29% had no detectable PAI using multiple loci. The cagA+ genotype frequencies were similar in the peptic ulcer and non-ulcer dyspepsia-gastritis groups (79% vs. 74%) whereas frequencies in the NUD-oesophagitis and normal mucosa groups were lower (58%) but not significantly different (P>0.41). Genomic IS605 inserts were present at an overall frequency of 32% and were widely distributed with respect to patient age and disease severity. The combined cagA+/IS- strain genotype was common but not significantly associated with PUD compared to endoscopically normal mucosa (P> or =0.807). We concluded that presence of the IS605 element, whether in cagA+ or cagA- strains of H. pylori, did not systematically modify the severity of associated disease in the study population.     

Cag pathogenicity island-independent up-regulation of matrix metalloproteinases-9 and -2 secretion and expression in mice by Helicobacter pylori infection

Helicobacter pylori cag pathogenicity island (PAI) is a major determinant of gastric injury via induction of several matrix metalloproteinases (MMPs). In the present study, we examined the influence of the cag PAI on gastric infection and MMP-9 production in mice and in cultured cells. A new mouse colonizing Indian H. pylori strain (AM1) that lacks the cag PAI was used to study the cag PAI importance in inflammation. Groups of C57BL/6 mice were inoculated separately with H. pylori strains AM1 and SS1 (cag+), gastric tissues were histologically examined, and bacterial colonization was scored by quantitative culture. Mice infected with either cag+ or cag- H. pylori strains showed gastric inflammation and elevated MMP-3 production. Significant up-regulation of pro-MMP-9 secretion and gene expression in H. pylori infected gastric tissues indicate dispensability of cag PAI for increased pro-MMP-9 secretion and synthesis in mice. In agreement, cell culture studies revealed that both AM1 and SS1 were equipotent in pro-MMP-9 induction in human gastric epithelial cells. Both strains showed moderate increase in MMP-2 activity in vivo and in vitro. In addition, increased secretion of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 induced pro-MMP-9 secretion and synthesis in AM1 or SS1 strain-infected mice suggesting elicitation of pro-inflammatory cytokines by both cag- and cag+ genotype. Moreover, tissue inhibitors of metalloproteinase-1 expression were decreased with increase in pro-MMP-9 induction. These data show that H. pylori may act through different pathways other than cag PAI-mediated for gastric inflammation and contribute to up-regulation of MMP-9 via pro-inflammatory cytokines.     

Reduced activation of inflammatory responses in host cells by mouse-adapted Helicobacter pylory isolates

Helicobacter pylori strains that harbour the Cag pathogenicity island (Cag PAI) induce interleukin (IL)-8 secretion in gastric epithelial cells, via the activation of NF- kappa B, and are associated with severe inflammation in humans. To investigate the influence of Cag PAI-mediated inflammatory responses on H. pylori adaptation to mice, a selection of H. pylori clinical isolates (n = 12) was cag PAI genotyped and tested in co-culture assays with AGS gastric epithelial cells, and in mouse colonization studies. Six isolates were shown to harbour a complete cag PAI and to induce NF- kappa B activation and IL-8 secretion in AGS cells. Of the eight isolates that spontaneously colonized mice, six had a cag PAI(-) genotype and did not induce pro-inflammatory responses in these cells. Mouse-to-mouse passage of the two cag PAI(+) -colonizing strains yielded host-adapted variants that infected mice with bacterial loads 100-fold higher than those of the respective parental strains (P= 0.001). These mouse-adapted variants were affected in their capacity to induce pro-inflammatory responses in host cells, yet no changes in cag PAI gene content were detected between the strains by DNA microarray analysis. This work provides evidence for in vivo selection of H. pylori bacteria with a reduced capacity to induce inflammatory responses and suggests that such bacteria are better adapted to colonize mice.     

Helicobacter pylori cag pathogenicity island-positive strains induce syndecan-4 expression in gastric epithelial cells

Helicobacter pylori is recognized as the main cause of gastritis and is associated with gastric carcinogenesis. Syndecan-4 represents the major source of heparan sulfate (HS) in the gastric cells. HS proteoglycans expressed on the cell surface constitute targets for H. pylori at the early stage of infection. The aim of this study was to determine whether H. pylori induction of syndecan-4 expression is affected by the virulence characteristics of the infecting strain, namely the cytotoxic-associated gene ( cag ) pathogenicity island (PAI). We observed that individuals infected with highly pathogenic H. pylori strains express syndecan-4 in the foveolar epithelium of the gastric mucosa. The association between the cag PAI status of the infecting strain and syndecan-4 expression was further demonstrated by infection of gastric epithelial cell lines with a panel of cag PAI⁺ and cag PAI⁻ H. pylori strains, showing that expression of syndecan-4 was significantly increased in response to infection with the highly pathogenic strains. Moreover, infection of gastric cells with cag A and cag E mutant strains further confirmed that syndecan-4 induction is dependent on an intact cag PAI. The present study shows that highly pathogenic H. pylori strains induce syndecan-4 expression, both in human gastric mucosa and in gastric cell lines, in a cag PAI-dependent manner.     

Multiple Infection and Microdiversity among Helicobacter pylori Isolates in a Single Host in India

Helicobacter pylori is one of the most diverse bacterial species that chronically infects more than 70% of Indian population. Interestingly, data showing microdiversity of the H. pylori strains within a particular gastric niche remained scarce. To understand the extent of genetic diversity among H. pylori strains within a given host, 30 patients with gastro-duodenal problems were subjected to endoscopy and from each patient 10 single colonies were isolated. Characterization of each of these 10 single colonies by DNA fingerprinting as well as genotyping of several important genetic markers viz. cagA, vacA, iceA, vapD, cag PAI empty site, IS605, RFLP and two other genetic segments within cag PAI revealed that all of the 30 patients were infected with more than one strain and sometimes strains with 5 to 6 types of genetic variants. Analyses of certain genetic loci showed the microdiversity among the colonies from single patient, which may be due to the recombination events during long-term carriage of the pathogen. These results suggest that most of the patients have acquired H. pylori due to repeated exposure to this pathogen with different genetic make-up, which may increase the possibility of super infections. Genetic exchanges between these unrelated H. pylori strains may support certain H. pylori variant to grow better in a given host than the parental strain and thereby increasing the possibility for the severity of the infection.     

No correlation of babA2 with vacA and cagA genotypes of Helicobacter pylori and grading of gastritis from peptic ulcer disease patients in Brazil

BACKGROUND: The babA2 gene, which encodes a blood-group antigen-binding adhesin that mediates attachment of Helicobacter pylori to human Lewis(b) antigens on gastric epithelial cells, has been associated with a higher risk of peptic ulcer and gastric cancer. The purpose of this study was to ascertain the frequency of babA2 genotype in H. pylori strains of patients with peptic ulcer and to correlate with other virulence factors. MATERIALS AND METHODS: vacA, cagA, and babA2 genotypes of H. pylori were determined by using polymerase chain reaction (PCR). DNA was extracted from positive urease test gastric samples of 150 patients with peptic ulcer. Antrum and corpus biopsies were taken for histologic examination according to the updated Sydney system classification. RESULTS: babA2 genotype was present in 104 (69.3%) and cagA in 113 (75.3%) gastric samples. No significant correlation was observed between babA2 and vacAs1 genotype or between babA2 and cagA status. The correlation of vacAs1 genotype with positive cagA was statistically significant ( p < .001). The babA2-positive strain was more frequently found from the gastric samples of men, than of women (p = .01). Strains harboring cagA, vacAs1, and babA2 genotypes had no association to the grading of gastritis, presence of glandular atrophy, or intestinal metaplasia. The simultaneous presence of cagA, vacAs1, and babA2 was found in 32.6% of the H. pylori strains. CONCLUSIONS: babA2 genotype is frequently found in H. pylori strains from peptic ulcer disease in Brazil, although it has no significant correlation to the worsening of the gastritis and to other virulence markers such as vacAs1 and cagA.     

The effect of the cag pathogenicity island on binding of Helicobacter pylori to gastric epithelial cells and the subsequent induction of apoptosis

BACKGROUND: Helicobacter pylori infection leads to gastritis, peptic ulcer, and gastric cancer, in part due to epithelial damage following bacteria binding to the epithelium. Infection with cag pathogenicity island (PAI) bearing strains of H. pylori is associated with increased gastric inflammation and a higher incidence of gastroduodenal diseases. It is now known that various effector molecules are injected into host epithelial cells via a type IV secretion apparatus, resulting in cytoskeletal changes and chemokine secretion. Whether binding of bacteria and subsequent apoptosis of gastric epithelial cells are altered by cag PAI status was examined in this study. METHODS: AGS, Kato III, and N87 human gastric epithelial cell lines were incubated with cag PAI-positive or cag PAI-negative strains of H. pylori in the presence or absence of clarithromycin. Binding was evaluated by flow cytometry and scanning electron microscopy. Apoptosis was assessed by detection of DNA degradation and ELISA detection of exposed histone residues. RESULTS: cag PAI-negative strains bound to gastric epithelial cells to the same extent as cag PAI-positive strains. Both cag PAI-positive and cag PAI-negative strains induced apoptosis. However, cag PAI-positive strains induced higher levels of DNA degradation. Incubation with clarithromycin inactivated H. pylori but did not affect binding. However, pretreatment with clarithromycin decreased infection-induced apoptosis. CONCLUSIONS: cag PAI status did not affect binding of bacteria to gastric epithelial cells but cag PAI-positive H. pylori induced apoptosis more rapidly than cag PAI-negative mutant strains, suggesting that H. pylori binding and subsequent apoptosis are differentially regulated with regard to bacterial properties.     

淮南地区幽门螺杆菌感染个体菌株基因多态性与感染结局的影响

目的:探讨淮南地区幽门螺杆菌感染个体菌株基因多态性及其与感染结局的影响。方法:选取125例幽门螺杆菌(H.pylori,HP)感染的慢性胃炎、消化性溃疡患者,常规获取胃窦、胃体部粘膜,进行HP分离、培养,提取HP基因组DNA,采用随机扩增多态性DNA(RAPD)指纹分析法检测菌株基因多态性;125例患者均给予质子泵抑制、H2受体拮抗剂、铋剂为基础的三联或四联疗法治疗,治疗后4~6周进行14C-尿素呼气试验评估Hp根除情况;获取HP根除失败患者的胃窦、胃体黏膜进行HP分离、培养、鉴定,并采用RAPD指纹分析法检测菌株来源,评估HP基因多态性对治疗结局的影响。结果:cagA、iceA1、iceA2、vacAs1、vacAm1、babA2阳性率分别为92.80%、36.00%、93.60%、93.60%、29.50%、53.50%,cagA、iceA2、vacAs阳性率均高于其他基因类型阳性率(P0.05或P0.01),其他基因类型阳性率比较差异无统计学意义(P0.05)。经治疗后HP根除率为86.4%(107/125),14.4%(18/125)根除失败;18例根除失败患者中,15例患者治疗前后的菌株具有相同的指纹图谱,证实为原菌株复发,其中cagA、iceA1、iceA2、vacAs1、vacAm1、babA2阳性率分别为93.33%、13.33%、86.67%、93.33%、6.67%、20.00%,cagA、iceA2、vacAs阳性率均高于其他基因类型阳性率(P0.05或P0.01)。结论:cagA+、vacAs+、iceA2+为淮南地区HP感染的优势基因型,该基因型易导致HP根除失败;未发现babA2与HP感染结局存在相关性。     

Correlation of the Helicobacter pylori adherence factor BabA with duodenal ulcer disease in four European countries

Helicobacter pylori strains harboring the vacAs1, cagA and babA2 have been associated with ulcer disease (UD). We compared the prevalence of these different genotypes and adhesive properties in H. pylori infected patients with UD in four European countries. Genomic DNA was isolated from 314 H. pylori strains: Germany (GER; n=92), Sweden (SWE, n=74), Portugal (POR, n=91) and Finland (FIN, n=57). The frequencies of babA2 genotype varied from 35% to 60%. Triple-positive strains (vacAs1+, cagA+ and babA2+) were significantly associated with UD in GER and POR and were closely correlated with UD in FIN, but not in SWE. Classification as triple-positive strains had a higher specificity for detection of UD in GER, POR and FIN than type1 or cagA+ strains. In vitro adhesion assays revealed that Swedish strains showed high adhesion properties and were thus correlated with the diagnosis of UD, although PCR detected the babA2 gene at lower frequencies and failed to show a correlation with UD. This finding appears to reflect allelic variations of the babA2 gene in SWE, although adhesive properties of the strains are retained.     

Emergence of recombinant strains of Helicobacter pylori during human infection

Genetic recombination can be important evolutionarily in speeding the adaptation of organisms to new environments and in purging deleterious mutations. Here, we describe polymerase chain reaction (PCR), hybridization and DNA sequence-based evidence of six such exchanges between two strains of Helicobacter pylori during natural mixed infection of a patient in Lithuania. One parent strain contained the 37 kb long, virulence-associated cag pathogenicity island (PAI), and the other strain lacked this PAI. Most H. pylori from the patient had descended from the cag ⁺ parent, but had become cag ⁻ during infection. This had resulted from transfer of DNA containing the 'empty site' allele from the cag ⁻ strain and homologous recombination, not from excision of the cag PAI without DNA transfer. Other cases of recombination involved genes for an outer membrane protein ( omp 5 and omp 29; also called HP0227 and HP1342) and a putative phosphoenolpyruvate synthase ( ppsA  ; HP0121). Replacement of a short patch of DNA sequence (36–124 bp) was also seen. As the chance of forming any given recombinant is small, the abundance of recombinants in this patient suggests selection for particular recombinant genotypes during years of chronic infection. We suggest that genetic exchange among unrelated H. pylori strains, as documented here, is important because of the diversity of this gastric pathogen and its human hosts. Certain H. pylori recombinants may grow better in a given host than either parent. The vigour of growth, in turn, could impact on the severity of disease that infection can elicit.     

幽门螺杆菌cag PAI编码的Ⅳ型分泌系统

幽门螺杆菌(Helicobacter pylori,H.pylori)是定植于人胃部特定的病原菌,感染呈全球分布,感染率高达50%以上。现已证实它是轻度胃炎,消化性溃疡及胃癌的主要病因。Ⅰ型H.pylori菌株含有一个约40kb的特殊基因片段,即cag致病岛(cytotoxin associated gene pathogenicity island,cag PAI),该片段只出现于致病相关菌株,基因呈高密度分布并编码一个分泌转运系统称为Ⅳ型分泌系统(type Ⅳ secretion system,TFSS),通过转运相关毒素而参与H.pylori诱导上皮细胞细胞内的酪氨酸磷酸化、细胞骨架重排、基垫结构形成、活化核转录因子NF-κB、诱导促炎细胞因子白细胞介素-8的表达等,故在H.pylori的致病中起着关键作用。近年来,研究者们致力于研究Ⅳ型分泌系统的功能,但是对于这个装置是如何转运蛋白进入宿主细胞的确切机制还是知之甚少,因此,对Ⅳ型分泌系统的研究将有助于进一步明确H.pylori致病机制,并为临床诊断和治疗提供新的靶点。     

Protein-protein interactions among Helicobacter pylori cag proteins

Many Helicobacter pylori isolates contain a 40-kb region of chromosomal DNA known as the cag pathogenicity island (PAI). The risk for development of gastric cancer or peptic ulcer disease is higher among humans infected with cag PAI-positive H. pylori strains than among those infected with cag PAI-negative strains. The cag PAI encodes a type IV secretion system that translocates CagA into gastric epithelial cells. To identify Cag proteins that are expressed by H. pylori during growth in vitro, we compared the proteomes of a wild-type H. pylori strain and an isogenic cag PAI deletion mutant using two-dimensional difference gel electrophoresis (2D-DIGE) in multiple pH ranges. Seven Cag proteins were identified by this approach. We then used a yeast two-hybrid system to detect potential protein-protein interactions among 14 Cag proteins. One heterotypic interaction (CagY/7 with CagX/8) and two homotypic interactions (involving H. pylori VirB11/ATPase and Cag5) were similar to interactions previously reported to occur among homologous components of the Agrobacterium tumefaciens type IV secretion system. Other interactions involved Cag proteins that do not have known homologues in other bacterial species. Biochemical analysis confirmed selected interactions involving five of the proteins that were identified by 2D-DIGE. Protein-protein interactions among Cag proteins are likely to have an important role in the assembly of the H. pylori type IV secretion apparatus.     

Prevalence of Helicobacter pylori vacA, cagA, cagE, iceA, babA2 genotypes and correlation with clinical outcome in Turkish patients with dyspepsia

BACKGROUND: Distinct virulence factors of Helicobacter pylori have been associated with clinical outcome of the infection; however, considerable variations have been reported from different geographic regions and data on genotypes of Turkish H. pylori isolates are sparse. AIM: To determine the prevalence of specific genotypes of H. pylori in Turkish patients with dyspepsia. MATERIALS AND METHODS: Ninety-three H. pylori-positive patients [30 with non-ulcer dyspepsia (NUD), 30 with duodenal ulcer (DU), and 33 with gastric cancer (GC)] who were admitted to our endoscopy unit due to dyspepsia were enrolled in the study. H. pylori infection was confirmed in all patients by histology and rapid urease test (RUT). The presence of vacA alleles, cagA, cagE, iceA, and babA2 genotypes were determined by polymerase chain reaction (PCR). Chi-squared test and Fisher's exact test were used for statistical comparisons and multivariate regression analysis was performed to find out independent predictors of different clinical outcomes. RESULTS: Turkish strains examined predominantly possessed the vacA s1,m2 (48.4%) and s1,m1 (40.7%) genotypes. The vacA s1a genotype was detected in 66.7, 96.4, and 87.9% of isolates from patients with NUD, DU, and GC, respectively, and its presence was significantly associated with that of DU (p = .004), GC (p = .043), and cagA gene (p = .021). None of the cases was found to harbor the s1c genotype. The frequencies of the cagA and cagE genes among studied isolates were 73.6 and 59.3%, respectively. The cagA gene was significantly associated with the presence of DU (p = .004) and GC (p = .003), and the cagE gene, too, was significantly associated with the presence of DU (p = .002) and GC (p = .000). All H. pylori isolates possessed the iceA gene. In all, 68 isolates (74.7%) were positive for iceA1 and 23 (25.3%) for iceA2. The frequency of icea1 gene was significantly higher in cases with GC (85%) than in cases with NUD (60%) (p = .026). The frequency of babA2 gene was 23.3, 46.4, and 87.9% in isolates of patients with NUD, DU, and GC, respectively. When compared to cases with NUD (p = .000) and DU (p = .000), the presence of babA2 gene was significantly higher in cases with GC. Multivariate regression analysis disclosed cagE (p = .006) and vacA s1a (p = .027) genotypes to be independent predictors of DU and babA2 (p = .000) and cagE (p = .013) genotypes to be independent predictors of GC. CONCLUSIONS: H. pylori vacA s1a, cagA, cagE genotypes have significant relations with the presence of DU and GC, and iceA1, babA2 with GC in Turkish patients with dyspepsia, whereas cagE and vacA s1a genotypes are independent predictors of DU, and babA2 and cagE genotypes are independent predictors of GC.     

Differences in genotypes of Helicobacter pylori from different human populations

DNA motifs at several informative loci in more than 500 strains of Helicobacter pylori from five continents were studied by PCR and sequencing to gain insights into the evolution of this gastric pathogen. Five types of deletion, insertion, and substitution motifs were found at the right end of the H. pylori cag pathogenicity island. Of the three most common motifs, type I predominated in Spaniards, native Peruvians, and Guatemalan Ladinos (mixed Amerindian-European ancestry) and also in native Africans and U.S. residents; type II predominated among Japanese and Chinese; and type III predominated in Indians from Calcutta. Sequences in the cagA gene and in vacAm1 type alleles of the vacuolating cytotoxin gene (vacA) of strains from native Peruvians were also more like those from Spaniards than those from Asians. These indications of relatedness of Latin American and Spanish strains, despite the closer genetic relatedness of Amerindian and Asian people themselves, lead us to suggest that H. pylori may have been brought to the New World by European conquerors and colonists about 500 years ago. This thinking, in turn, suggests that H. pylori infection might have become widespread in people quite recently in human evolution.     

Monocyte and Macrophage Killing of Helicobacter pylori: Relationship to Bacterial Virulence Factors

Background:  Helicobacter pylori infection is an important health problem, as it involves approximately 50% of the world's population, causes chronic inflammatory disease and increases the risk of gastric cancer development. H. pylori infection elicits a vigorous immune response, but this does not usually result in bacterial clearance. We have investigated whether the persistence of H. pylori in the host could be partly due to an inability of macrophages to kill this bacterium.
Materials and Methods:  Monocytes and macrophages isolated from the peripheral blood of normal human controls were infected in vitro with five H. pylori isolates. The isolates were characterized for known H. pylori virulence factors; vacuolating cytotoxin (VacA), the cag pathogenicity island ( cag PAI), urease, and catalase by Western blot and polymerase chain reaction analysis. The ability of primary human monocytes and macrophages to kill each of these H. pylori strains was then defined at various time points after cellular infection.
Results:  The five H. pylori strains showed contrasting patterns of the virulence factors. There were different rates of killing for the bacterial strains. Macrophages had less capacity than monocytes to kill three H. pylori strains. There appeared to be no correlation between the virulence factors studied and differential killing in monocytes.
Conclusions:  Primary human monocytes had a higher capacity to kill certain strains of H. pylori when compared to macrophages. The VacA, cag PAI, urease, and catalase virulence factors were not predictive of the capacity to avoid monocyte and macrophage killing, suggesting that other factors may be important in H. pylori intracellular pathogenicity.