Helicobacter baculiformis sp. nov., isolated from feline stomach mucosa

A Gram-negative, microaerophilic slender rod, measuring approximately 10 mum long and approximately 1 microm wide, isolated from the gastric mucosa of a cat and designated strain M50(T), was subjected to a polyphasic taxonomic study. Despite its apparent lack of helical coils, the organism showed a corkscrew-like motion by means of multiple sheathed flagella located at both ends of the cell and by a periplasmic fibril coiled around the body. Strain M50(T) grew preferably on biphasic culture plates or on very moist agar. Coccoid forms predominated in cultures older than 4 days as well as in growth obtained on dry agar plates. The strain grew at 37 degrees C, but not at 25 or 42 degrees C and exhibited urease, oxidase and catalase activities. On the basis of 16S rRNA gene sequence analysis, the novel isolate was identified as a member of the genus Helicobacter and showed about 98 to 99 % sequence similarity to Helicobacter felis, Helicobacter bizzozeronii, Helicobacter salomonis, Helicobacter cynogastricus and 'Candidatus Helicobacter heilmannii', five highly related species previously detected in the feline or canine gastric mucosa. Protein profiling of strain M50(T) using SDS-PAGE revealed a pattern different from those of other Helicobacter species of mammalian gastric origin. Additionally, the urease and HSP60 gene sequences of strain M50(T) were different from those of H. felis, H. bizzozeronii, H. salomonis, H. cynogastricus and 'Ca. H. heilmannii'. It is thus proposed that strain M50(T) (=LMG 23839(T)=CCUG 53816(T)) represents a novel species within this genus, for which the name Helicobacter baculiformis sp. nov. is proposed.

High prevalence of tetracycline resistance in Enterococcus isolates from broilers carrying the erm(B) gene

A total of 73 isolates of Enterococcus spp. carrying the erm(B) gene were obtained from cloacal swabs of broiler chickens derived from 13 different farms in Belgium. The erm(B) gene encodes resistance to macrolides, lincosamides and streptogramin B antibiotics (MLS(B)). The isolates belonged to eight different species: Enterococcus avium (eight isolates), Enterococcus casseliflavus (11 isolates), Enterococcus cecorum (eight isolates), Enterococcus durans (seven isolates), Enterococcus faecalis (10 isolates), Enterococcus faecium (17 isolates), Enterococcus gallinarum (seven isolates) and Enterococcus hirae (five isolates). Acquired resistance to tetracycline was detected in 68 of the isolates, and in 62 of these it was associated with the presence of the resistance genes tet(L), tet(M), tet(O) or tet(S). In three E. faecium isolates that were phenotypically susceptible to tetracycline, tet(L) or tet(M) was present. The transposon integrase gene (int gene) of the Tn916/Tn1545 transposon family was detected in 18 of the 54 isolates that contained the tet(M) gene. It was concluded that acquired resistance to tetracycline antibiotics is often present in enterococci from poultry carrying the erm(B) gene. The use of tetracyclines in poultry may therefore co-select for resistance to MLS(B) antibiotics, which may be important as alternative therapy for enterococcal infections in humans.

Prevalence of ‘Candidatus Helicobacter suis’ in pigs of different ages

Samples from the antrum and fundus of the stomachs of 457 pigs from 22 different herds were screened for the presence of 'Candidatus Helicobacter suis' by pcr, and samples from the antrum and/or fundus of 222 of the stomachs were tested for urease activity. The prevalence of the infection was very low before weaning, increased rapidly after weaning and reached 90 per cent in the adult boars and sows. The agreement between the results obtained with the pcr test and the urease test was very good for some age groups and sampling sites, but poor for other age groups and sampling sites.

Prevalence and Mechanism of Resistance against Macrolides, Lincosamides, and Streptogramins amongEnterococcus faeciumIsolates from Food-Producing Animals and Hospital Patients in Belgium

The prevalence of acquired resistance to streptogramins, macrolides, and lincosamides and the genetic background of this resistance was investigated in Enterococcus faecium strains isolated from food-producing animals and hospital patients 4-5 years after the ban of streptogramins as growth promoters. The minimum inhibitory concentrations (MICs) of quinupristin/dalfopristin (Q/D), virginiamycin M1 (virgM1), erythromycin (ery), tylosin (tyl), and lincomycin (lin) were determined by the agar dilution method for E. faecium isolates derived from pigs (80), broilers (45), and hospitalized patients (103). Resistance or susceptibility was interpreted using a microbiological criterion and breakpoints recommended by the Clinical Laboratory Standards Institute (CLSI), if available. The isolates were also screened by PCR for erm(B), lnu(A), lnu(B), mef(A/E), vat(D), vat(E), vga(A), vga(B), and vgb(A) genes. Acquired resistance to Q/D, virgM1, ery, tyl, and lin was detected in 34%, 96%, 46%, 46%, and 69% of the porcine strains, respectively. For broiler strains this was 15% (Q/D), 98% (virgM1), 69% (ery), 71% (tyl), and 89% (lin) and for human strains 23% (Q/D), 65% (virgM1), 54% (ery), 52% (tyl), and 60% (lin). Strains showing cross-resistance against macrolides and lincosamides almost always carried the erm(B) gene. This gene was present in 64% of the Q/D-resistant isolates. Only in two human and three broiler Q/D- and virgM1-resistant isolates, a combination of the erm(B) and vat(D) or vat(E) genes was found. The genetic background of resistance could not be determined in the other Q/D- or virgM1-resistant strains. This study demonstrates that streptogramin resistance is frequently present in strains from hospitalized patients and food-producing animals, but the genetic basis hitherto mostly remains obscure.

Yersinia ruckeri infections in salmonid fish

Yersinia ruckeri is the causative agent of yersiniosis or enteric redmouth disease leading to significant economic losses in salmonid aquaculture worldwide. Infection may result in a septicaemic condition with haemorrhages on the body surface and in the internal organs. Despite the significance of the disease, very little information is available on the pathogenesis, hampering the development of preventive measures to efficiently combat this bacterial agent. This review discusses the agent and the disease it causes. The possibility of the presence of similar virulence markers and/or pathogenic mechanisms between the Yersinia species which elicit disease in humans and Y. ruckeri is also examined.

An unusual Actinobacillus equuli strain isolated from a rabbit with Tyzzer's disease

Actinobacillus equuli was isolated in pure culture from the liver and lungs of an adult rabbit with Tyzzer's disease (Clostridium piliforme). Based on the haemolytic features on blood agar plates, a positive reaction in the CAMP-test, hydrolysis of esculin, the inability to ferment l-arabinose, tDNA-PCR and sequencing of the 16S rRNA gene, the isolate was classified as A. equuli subsp. haemolyticus biovar 1. However, the aqxA gene, characteristic for haemolytic A. equuli strains, was not detected by PCR.

Helicobacter equorum sp. nov., a urease-negative Helicobacter species isolated from horse faeces

Gram-negative, curved, motile bacteria (strains EqF1T and EqF2) were isolated from faecal samples from two clinically healthy horses. Both strains possessed a single, monopolar, sheathed flagellum and were urease-negative. The novel strains grew at 37 °C under microaerobic conditions and were positive for oxidase, catalase and alkaline phosphatase activities. The isolates reduced nitrate to nitrite, but γ-glutamyl transpeptidase activity was not detected. The novel isolates did not grow at 42 °C or on media containing 1 % glycine. They were resistant to cephalotin and nalidixic acid and susceptible to metronidazole. Analysis of the 16S and 23S rRNA gene sequences of the two novel strains identified them as representing a single species within the genus Helicobacter. In terms of 16S rRNA gene sequence similarity, Helicobacter pullorum and Helicobacter canadensis were the most closely related species (98 % similarity). 23S rRNA gene sequence analysis also classified strains EqF1T and EqF2 within the enterohepatic division of the genus Helicobacter, but only 94 % similarity was detected with H. pullorum and H. canadensis, which are helicobacters with unsheathed flagella. The most closely related species in terms of 23S rRNA gene sequence similarity was Helicobacter canis (95 %). Numerical analysis of whole-cell protein extracts by SDS-PAGE was performed and the novel isolates were clearly differentiated from H. pullorum, H. canadensis, H. canis and other species of the genus Helicobacter. This finding was also confirmed by sequence analysis of the hsp60 gene. On the basis of these genetic, biochemical and protein data, the isolates are classified as representing a novel species, for which the name Helicobacter equorum sp. nov. is proposed (type strain EqF1T=LMG 23362T=CCUG 52199T).

Interactions of highly and low virulent Mycoplasma hyopneumoniae isolates with the respiratory tract of pigs

Mycoplasma hyopneumoniae is the etiological agent of swine enzootic pneumonia, a chronic nonfatal disease affecting pigs of all ages. To obtain better insight in the mechanisms responsible for differences in virulence between highly and low virulent M. hyopneumoniae isolates, 23 caesarean-derived, colostrum-deprived piglets were randomly assigned to three groups. Groups 1 and 2 consisted of nine animals each, which were intratracheally inoculated at 1 week of age with a highly or a low virulent isolate of M. hyopneumoniae, respectively. The remaining five animals were inoculated with sterile culture medium. Animals were euthanized at 5, 10, 15 and 28 days post-inoculation (DPI). Animals inoculated with the highly virulent isolate had more neutrophils in BAL fluid at 10, 15 and 28DPI compared to the other groups. At 10 and 15DPI, animals in the highly virulent group had significantly higher concentrations of TNF-alpha in BAL fluid. IL-1beta concentration in this group was higher at 5 and 28DPI compared to the other groups. From 10DPI onwards, significantly higher titres of M. hyopneumoniae were detected in the BAL fluid of animals inoculated with the highly virulent isolate compared to animals inoculated with the low virulent isolate. Additionally, the in vitro generation time of the highly virulent M. hyopneumoniae isolate was significantly shorter than that of the low virulent isolate. The present study indicates that the difference in pathogenicity between the highly and low virulent isolates is associated with a faster in vitro growth, a higher capacity to multiply in the lungs and the induction of a more severe inflammation process by the highly virulent isolate.

Detection of tetracycline-resistant and susceptible pasteurellaceae in the nasopharynx of loose group-housed calves

The aim of the present study was to determine which Pasteurella and Mannheimia species are present in the upper respiratory tract of healthy calves with no history of antimicrobial treatment prior to sampling. The presence of subpopulations of tetracycline-resistant Pasteurellaceae was also investigated. Nasal swabs from 61 loose group-housed, clinically healthy calves, 1 to 4 months old, from 16 dairy herds were inoculated aerobically on a selective medium (Columbia agar with 5% ovine blood and 16 mg/L bacitracin) with or without 4 mg/L oxytetracycline (OTC). A total of 43 strains belonging to the family Pasteurellaceae were isolated from 38 calves (62.3%) out of 13 herds (81.3%). The predominant organisms were Pasteurella multocida subsp. multocida (57.4%), Mannheimia varigena (4.9%) and M. haemolytica (3.2%). Growth of Pasteurellaceae on the OTC-containing medium was seen only with samples from two herds (6 animals; 9.8%), and on only one farm this proved to be an OTC-resistant subpopulation. Minimum inhibitory concentration (MIC) determinations by means of agar dilution confirmed a low prevalence of OTC-resistant Pasteurellaceae, with overall MIC(50) and MIC(90) values of 0.25 and 32 mg/L, respectively. These data do not support the hypothesis that the relative high frequency of tetracycline-resistant P. multocida isolates from fatal cases of bovine respiratory disease is related to the presence of minor tetracycline-resistance subpopulations within this species.

Experimental Infection of Pigs with ‘Candidatus Helicobacter suis’

'Candidatus Helicobacter suis' is a spiral-shaped bacterium that colonizes the stomach of more than 60% of slaughter pigs. The role of 'Candidatus Helicobacter suis' in gastric disease of pigs is still unclear. Experimental studies in pigs are lacking because this bacterium is unculturable until now. An inoculation protocol using 'Candidatus Helicobacter suis' infected mouse stomach homogenate was used to reproduce the infection in pigs. Control animals were inoculated using negative mouse stomach homogenate. Pigs were inoculated three times with one-week intervals and euthanized 6 weeks post inoculation. Tissue samples were taken from different mucosal stomach regions to detect 'Candidatus Helicobacter suis' by PCR and urease test. Mucosal inflammation was evaluated on formalin-fixed tissue samples. Lesions in the pars oesophagea were scored macroscopically. Infection was successful in all challenged animals, with the antrum and the fundus being predominantly positive. Infection was associated with infiltration of lymphocytes and plasma cells in the antral mucosa, evolving to follicular gastritis. No apparent inflammation of the fundic stomach region was detected in the infected animals. A clear link between 'Candidatus Helicobacter suis' and pars oesophageal lesions could not be found.

Prevalence of Helicobacter equorum in faecal samples from horses and humans

Recently, a new enterohepatic Helicobacter species, H. equorum, was isolated from faecal samples of two clinically healthy horses. At the onset of this study, nothing was known about the prevalence of this organism in horses, nor was there any information available on the possible zoonotic character of this agent. This study aimed to determine the prevalence of H. equorum in faecal samples from equine and human origin. Therefore, faecal samples of 120 healthy privately owned horses, 227 healthy riding-school horses and 239 hospitalised horses were screened for H. equorum-DNA by means of a PCR amplifying a 1074-bp fragment of the 23S rRNA gene with primers specific for H. equorum. The vast majority of the hospitalised horses were under treatment with an antimicrobial agent at the moment of sampling, while the other horses had not been treated with an antimicrobial agent in the 14 days preceding the sampling. Stool samples of 531 humans suffering from gastro-intestinal disease and 100 clinically healthy humans were likewise examined. H. equorum-DNA was demonstrated in faeces from 0.8% of the privately owned horses, 3.1% of the riding-school horses and 7.9% of the hospitalised horses. The prevalence of H. equorum was significantly higher in hospitalised than in healthy, privately owned horses (P=0.02). H. equorum-DNA was not detected in human samples. These results indicate that the prevalence of H. equorum in horses may be influenced by the health status of the investigated horse population and/or by antimicrobial treatment. We may additionally assume that this micro-organism does not commonly infect humans.

Geno- and phenotypic diversity of avian isolates of Streptococcus gallolyticus subsp. gallolyticus (Streptococcus bovis) and associated diagnostic problems

Recently, strains of Streptococcus bovis were reclassified as Streptococcus gallolyticus. In the present study we describe for the first time an outbreak of S. gallolyticus in a broiler flock. Mortality during the first week was normal (<1%), with a final total mortality at the end of production reaching 4.3%. Specific symptoms were not observed. Postmortem pathology demonstrated enlarged and light spleens and livers accompanied by multifocal irregular necroses surrounded by a hemorrhagic zone. In addition, these birds suffered from arthritis and osteomyelitis. Strains isolated from liver and spleen lesions showed clonality as demonstrated by pulsed-field gel electrophoresis. Compared to strains representing previously derived phylogeny, including the S. bovis-S. equinus complex, the 16S rRNA-derived phylogeny of the strains investigated in this study demonstrated a paraphyletic group (S. gallolyticus) well separated from two monophyletic groups: (i) S. equinus-S. bovis plus S. infantarius and (ii) S. alactolyticus plus S. intestinalis. According to information in GenBank, none of the strains included from the two monophyletic groups have been isolated from birds. Further biochemical analyses, including tannase activity, identified for the first time avian isolates belonging to S. gallolyticus subsp. gallolyticus. However, these investigations also demonstrated a clear heterogeneity with pigeon isolates.

CloacalLactobacillusIsolates from Broilers Often Display Resistance Toward Tetracycline Antibiotics

Lactobacillus crispatus, L. reuteri, L. amylovorus, L. gallinarum, and L. salivarius subsp. salivarius strains isolated from cloacal swabs of broiler chickens derived from 20 different farms in Belgium were tested for susceptibility to tetracycline and minocycline. Acquired resistance percentages to these antibiotics were extremely high for L. crispatus, L. reuteri, L. gallinarum, and L. salivarius subsp. salivarius (75%-100%). L. amylovorus on the contrary, displayed lower resistance percentages (25%) toward minocycline and tetracycline. In several strains, resistance against the tetracycline antibiotics was associated with the presence of the resistance genes tet(K), tet(L), tet(M), tet(W), and tet(Z). To our knowledge, this is the first report of tet(Z) in lactobacilli and tet(K), tet(L), and tet(W) in lactobacilli identified to species level. Our findings strengthen the evidence of intestinal Lactobacillus species acting as a pool of antimicrobial resistance genes urging the need for prudent use of tetracycline antibiotics in poultry production.

Protein variability among Mycoplasma hyopneumoniae isolates

Sodium-dodecyl-sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was used to study the protein variability of Mycoplasma hyopneumoniae isolates. Fifty-six M. hyopneumoniae isolates from 6 different countries and 37 different herds were used. From eight herds, more than one isolate was available. All SDS-PAGE patterns of isolates originating from different herds were clearly divergent. Intra-species protein variability was quantified using the reference strain J and seven field strains all obtained from different herds and classified according to virulence. Between the field strains, a variability of 25% was found, while the culture-adapted strain J was clearly divergent and showed 30% variability with the field strains. No clustering according to virulence was obtained, but a protein band of about 181kDa was present in the two highly virulent isolates whereas this protein band was absent in the moderately and low virulent isolates. Protein patterns of isolates derived from different animals from the same herd, were identical or differed in only a few protein bands. This study clearly indicates that, in agreement with previous studies on genomic diversity of M. hyopneumoniae isolates, proteomic variability within the species is high. Our study did not find clear evidence that more than one M. hyopneumoniae isolate circulates within a herd at a specific time point. The minor differences found between M. hyopneumoniae isolates from the same herd might reflect the organism's ability to alter its proteomic expression profile under field conditions.

The effect of Helicobacter felis and Helicobacter bizzozeronii on the gastric mucosa in Mongolian gerbils: a sequential pathological study

In contrast to Helicobacter(H.) pylori, little is known about the pathogenic mechanisms of gastric non-H. pylori Helicobacter species. Mongolian gerbils were inoculated intragastrically with H. felis or H. bizzozeronii and killed at different timepoints post-inoculation (p.i.), stomach tissue being taken for light and transmission electron microscopy (TEM) and polymerase chain reaction (PCR) analysis. Parietal cells (PCs), apoptosis, cell proliferation and nuclear factor-kappaB (NF-kappaB) activation were "visualized" immunohistochemically. Inflammation consisted of neutrophilic granulocytes, mainly in the antrum, and lymphocytic infiltrates around the limiting ridge and throughout the stomach mucosa and submucosa. From day 11 p.i. onwards, H. felis-inoculated animals showed moderate to severe loss of PCs extending from the limiting ridge into the fundus. Apoptotic cells, spiral bacteria, cell proliferation, and NF-kappaB activation were detected at the transition zone between affected and normal PCs. TEM revealed interaction of H. felis flagella with PCs and chief cells. Moreover, H. felis was seen in proximity to, and inside, necrotic cells. At 10 weeks p.i., some H. felis-infected gerbils showed complete loss of fundic glands, and mucous metaplasia of the epithelium. H. bizzozeronii, which made no flagellar contact with epithelial cells, was associated with only mild PC loss. The mechanism by which H. felis induces PC necrosis and apoptosis remains unclear. The observed flagellar contact and NF-kappaB activation may play an important role in H. felis-associated inflammation.

Helicobacter cynogastricus sp. nov., isolated from the canine gastric mucosa

A Gram-negative, microaerophilic helical rod, isolated from the gastric mucosa of a dog and designated strain JKM4(T), was subjected to a polyphasic taxonomic study. The tightly coiled organism, measuring 10-18 mum long and up to 1 mum wide, was motile by means of multiple sheathed flagella located at both ends of the cell and by a periplasmic fibril running along the external side of the helix. Strain JKM4(T) grew preferably on biphasic culture plates or on very moist agar. Coccoid forms predominated in cultures older than 4 days as well as in growth obtained on dry agar plates. The strain grew at 30 and 37 degrees C, but not at 25 or 42 degrees C and exhibited urease, oxidase and catalase activities. On the basis of 16S rRNA gene sequence analysis, the novel isolate was identified as a member of the genus Helicobacter and showed > 97 % similarity to Helicobacter felis, Helicobacter bizzozeronii and Helicobacter salomonis, three species previously isolated from the canine gastric mucosa. Protein profiling of strain JKM4(T) using SDS-PAGE revealed a pattern different from those of other Helicobacter species of mammalian gastric origin and from Helicobacter canis. Additionally, the urease gene sequence of strain JKM4(T) was different from those of urease genes of H. felis, H. bizzozeronii, H. salomonis and "Candidatus Helicobacter heilmannii". It is thus proposed that strain JKM4(T) (=LMG 23188(T)) represents a novel species within this genus, Helicobacter cynogastricus sp. nov.

Low frequency of Helicobacter species in the stomachs of experimental rabbits

The natural occurrence of established Helicobacter species was investigated in the stomachs of 65 laboratory rabbits, by means of polymerase chain reaction (PCR) (65/65) and histological analysis (51/65). The degree of inflammation in the different regions of the rabbits' stomach was evaluated on haematoxylin and eosin (HE)-stained histological slides. Four rabbits were found positive for Helicobacter species by PCR. Based on 16S ribosomal ribonucleic acid (rRNA) sequences, H. canadensis/H. pullorum organisms were identified in three animals. Bacteria were seen on merely one histological slide from one of these animals. H. felis was identified in one rabbit. Histological examination revealed no inflammation in the stomachs of 40 rabbits, while moderate gastric inflammation was seen in 11 animals, mainly in the antrum. In conclusion, the stomach of the laboratory rabbits included in the study was occasionally found positive for Helicobacter species, which were mostly identified as enterohepatic helicobacters, probably reflecting a mere passage of these bacteria through the stomach.

Acquired antimicrobial resistance in the intestinal microbiota of diverse cat populations

The aim of this study was to investigate the prevalence of acquired antimicrobial resistance in the resident intestinal microbiota of cats and to identify significant differences between various cat populations. Escherichia coli, Enterococcus faecalis, E. faecium and Streptococcus canis were isolated as faecal indicator bacteria from rectal swabs of 47 individually owned cats, 47 cattery cats and 18 hospitalised cats, and submitted through antimicrobial sensitivity tests. The results revealed that bacteria isolated from hospitalised and/or cattery cats were more frequently resistant than those from individually owned cats. E. coli isolates from hospitalised cats were particularly resistant to ampicillin, tetracycline and sulfonamide. Both enterococci and streptococci showed high resistance to tetracycline and in somewhat lesser extent to erythromycin and tylosin. Most E. faecium isolates were resistant to lincomycin and penicillin. One E. faecalis as well as one E. faecium isolate from hospitalised cats showed 'high-level resistance' (MIC > 500 microg/ml) against gentamicin, a commonly used antimicrobial agent in case of human enterococcal infections. The results of this research demonstrate that the extent of acquired antimicrobial resistance in the intestinal microbiota of cats depends on the social environment of the investigated population. It is obvious that the flora of healthy cats may act as a reservoir of resistance genes.

Cloacal Lactobacillus isolates from broilers show high prevalence of resistance towards macrolide and lincosamide antibiotics

Eighty-seven Lactobacillus strains isolated from cloacal swabs of broiler chickens derived from 20 different farms in Belgium were identified to species level and tested for susceptibility to macrolide and lincosamide antibiotics. Five different Lactobacillus species were identified as being predominantly present in the cloacae of broilers: Lactobacillus crispatus, Lactobacillus salivarius subsp. salivarius, Lactobacillus amylovorus, Lactobacillus gallinarum and Lactobacillu sreuteri. Acquired resistance prevalence to macrolides and lincosamides was very high in the investigated lactobacilli: 89% of the strains were resistant to either or both lincosamide and macrolide class antibiotics. The vast majority of these resistant strains (96%) displayed constitutive resistance. More than one-half of the macrolide and/or lincosamide resistant strains carried an erm(B), erm(C), mef(A), lnu(A) gene or a combination of these genes.

Protective immunization against “Candidatus Helicobacter suis” with heterologous antigens of H. pylori and H. felis

"Helicobacter (H.) heilmannii" type 1 colonizes the human stomach. It has been shown to be identical to "Candidatus H. suis", a Helicobacter species colonizing the stomach of more than 60% of slaughter pigs. This bacterium is, until now, not isolated in vitro. The effect of vaccination on "Candidatus H. suis" infection was studied in a mouse model. Mice were vaccinated intranasally or subcutaneously with whole bacterial cell lysate of Helicobacter pylori or Helicobacter felis and subsequently challenge infected with "Candidatus H. suis". Intranasal and subcutaneous immunisation caused a decrease in faecal excretion of "Candidatus H. suis" DNA. Urease tests on stomach tissue samples at 16 weeks after challenge infection were negative in all H. felis intranasally immunized animals and in the majority of the animals of the other immunisation groups. Since PCR on stomach tissue samples at 16 weeks after challenge infection could still detect "Candidatus H. suis DNA" in all immunisation-challenge groups, complete clearance of challenge bacteria was not achieved.

Evaluation of antibiotic treatment against "Candidatus Helicobacter suis" in a mouse model

"Helicobacter heilmannii" (proposed name) type 1 colonizes the human stomach. It has been shown to be identical to "Candidatus Helicobacter suis," a Helicobacter species colonizing the stomachs of >60% of slaughter pigs. This bacterium has not been isolated in vitro until now. Antibiotic susceptibility testing of "Candidatus Helicobacter suis" has not been carried out so far. For the present study, a mouse model was adopted to evaluate the antibiotic susceptibility of this organism. Mice infected with "Candidatus Helicobacter suis" were treated with amoxicillin and omeprazole, a therapy which is used to treat H. heilmannii infections in humans. Two different isolates of "Candidatus Helicobacter suis" were tested. The excretion of bacterial DNA was assessed during treatment, using PCR on fecal samples. At the end of the experiment, 8 days after the cessation of treatment, the presence of infection was evaluated using a urease test and a PCR test on stomach samples. A marked decrease in the excretion of bacterial DNA was observed a few days after the onset of treatment, and the level remained low until the end of the experiment. A difference in susceptibility between the two "Candidatus Helicobacter suis" isolates was pointed out. The in vivo mouse model infected with "Candidatus Helicobacter suis" will be useful for further screening of potential therapeutic regimens.

The inflammatory response in the mouse stomach to Helicobacter bizzozeronii, Helicobacter salomonis and two Helicobacter felis Strains

The inflammatory response in the mouse stomach was evaluated as a means of distinguishing different non-pylori Helicobacter (H.) strains in terms of virulence. Mice of four strains (BALB/c, SJL, C57BL/6 and CFW) were infected intragastrically with four bacterial strains (H. felis ATCC 49179 and CCUG 37471, H. bizzozeronii and H. salomonis). The animals were killed for gastric examination at 3, 9 or 16 weeks post-inoculation. H. salomonis could not be detected by the polymerase chain reaction, but the other three organisms were detected in all stomach samples at all timepoints. SJL mice consistently showed particularly severe gastric inflammation regardless of bacterial strain. Lymphocytes and occasionally neutrophils were seen in submucosa and lamina propria mucosae. BALB/c mice showed the least severe inflammatory changes. H. bizzozeronii differed from the two H. felis strains in producing less striking pathological changes in mice. Of the two H. felis strains, ATCC 49179 produced the more severe inflammatory changes in SJL mice.

Comparison and Transferability of theerm(B) Genes between Human and Farm Animal Streptococci

To obtain better insights into the possible exchange of resistance genes between human and animal streptococci, the sequences of the erm (B) genes of streptococcal isolates from humans, pigs, pork carcasses, chickens, and calves were compared. Identical erm (B) gene sequences were present in strains from humans, pigs, pork carcasses, and calves. During in vitro mating experiments, the erm (B) gene was exchanged between porcine Streptococcus suis and human S. pneumoniae, S. pyogenes, and S. oralis strains. The presence of different tetracycline resistance genes and the int Tn 1545 gene was determined in animal streptococci carrying the erm (B) gene. Although tet(M) and int Tn 1545 genes were detected in 24% of the porcine and pork carcass streptococcal strains, the tet(O) gene was the predominant tetracycline resistance gene in these strains (81%). The latter gene was co-transferred with the erm (B) gene from porcine S. suis strains to human streptococci in the mating experiments. These results show that, identical erm (B) gene sequences were present in animal and human streptococci and that transfer of the erm (B) gene from porcine S. suis to human streptococci and vice versa is possible, but probably occurs at a low frequency.