Annemie Decostere

Gastric Helicobacters in Domestic Animals and Nonhuman Primates and Their Significance for Human Health

SUMMARY Helicobacters other than Helicobacter pylori have been associated with gastritis, gastric ulcers, and gastric mucosa-associated lymphoid tissue lymphoma in humans. These very fastidious microorganisms with a typical large spiral-shaped morphology were provisionally designated “H. heilmannii,” but in fact they comprise at least five different Helicobacter species, all of which are known to colonize the gastric mucosa of animals. H. suis, which has been isolated from the stomachs of pigs, is the most prevalent gastric non-H. pylori Helicobacter species in humans. Other gastric non-H. pylori helicobacters colonizing the human stomach are H. felis, H. salomonis, H. bizzozeronii, and the still-uncultivable “Candidatus Helicobacter heilmannii.” These microorganisms are often detected in the stomachs of dogs and cats. “Candidatus Helicobacter bovis” is highly prevalent in the abomasums of cattle but has only occasionally been detected in the stomachs of humans. There are clear indications that gastric non-H. pylori Helicobacter infections in humans originate from animals, and it is likely that transmission to humans occurs through direct contact. Little is known about the virulence factors of these microorganisms. The recent successes with in vitro isolation of non-H. pylori helicobacters from domestic animals open new perspectives for studying these microorganisms and their interactions with the host.

Identification of Non-Helicobacter pylori Spiral Organisms in Gastric Samples from Humans, Dogs, and Cats

ABSTRACT Tightly coiled bacteria are a rare cause of gastric pathology in humans and represent a mixture of species for which a zoonotic origin is suspected. Similar organisms are common inhabitants of the gastric mucosae of carnivores and pigs. It was the goal of the present study to determine the actual occurrence of each individual Helicobacter species in human, canine, and feline stomachs in order to better understand the possible zoonotic significance. Gastric biopsy samples from humans with histological evidence of non-Helicobacter pylori spiral bacteria (n = 123) and samples from the gastric antrum, corpus, and cardia from dogs (n = 110) and cats (n = 43) were subjected to a multiplex PCR, enabling the identification of Helicobacter felis, Helicobacter bizzozeronii, Helicobacter salomonis, and “Candidatus Helicobacter suis.” A PCR for detecting H. pylori was applied to all human samples. Single infections with “Candidatus Helicobacter suis,” H. felis, H. bizzozeronii, H. salomonis, a hitherto unknown genotype of a non-H. pylori spiral organism (Helicobacter-like organism 135 [HLO135]), and H. pylori were identified in 30.9%, 8.9%, 2.4%, 11.4%, 7.3%, and 8.9% of the human biopsy samples, respectively. Mixed infections (16.3%) with two or even three of these were also found. In the canine stomach, H. bizzozeronii (70.0%) was encountered as the main spiral organism, while H. felis (62.7%) and HLO135 (67.4%) were the predominant Helicobacter species found in the feline gastric mucosa. Although the majority of human non-H. pylori organisms are Helicobacter species naturally occurring in the stomachs of pigs, cats, and dogs, the frequent identification of H. salomonis in human gastric biopsy samples is in contrast to its rare identification in pet carnivore samples, urging us to suspect other sources of infection.

Columnaris disease in fish: a review with emphasis on bacterium-host interactions

Flavobacterium columnare (F. columnare) is the causative agent of columnaris disease. This bacterium affects both cultured and wild freshwater fish including many susceptible commercially important fish species. F. columnare infections may result in skin lesions, fin erosion and gill necrosis, with a high degree of mortality, leading to severe economic losses. Especially in the last decade, various research groups have performed studies aimed at elucidating the pathogenesis of columnaris disease, leading to significant progress in defining the complex interactions between the organism and its host. Despite these efforts, the pathogenesis of columnaris disease hitherto largely remains unclear, compromising the further development of efficient curative and preventive measures to combat this disease. Besides elaborating on the agent and the disease it causes, this review aims to summarize these pathogenesis data emphasizing the areas meriting further investigation.

Susceptibility of Clostridium perfringens strains from broiler chickens to antibiotics and anticoccidials

Clostridium perfringens strains isolated in 2002 from the intestines of broiler chickens from 31 different farms located in Belgium were tested for susceptibility to 12 antibiotics used for therapy, growth promotion or prevention of coccidiosis. All strains were uniformly sensitive to the ionophore antibiotics monensin, lasalocid, salinomycin, maduramycin and narasin. All were sensitive to avilamycin, tylosin and amoxicillin, while flavomycin (bambermycin) showed low or no activity. Chlortetracycline and oxytetracycline were active at very low concentrations, but low-level acquired resistance was detected in 66% of the strains investigated. Fifty percent of these strains carried the tetP(B) resistance gene, while the tet(Q) gene was detected in only one strain. One strain with high-level resistance against tetracyclines carried the tet(M) gene. Sixty-three percent of the strains showed low-level resistance to lincomycin. The lnu(A) and lnu(B) genes were each only found in one strain. Compared with a similar investigation carried out in 1980, an increase was seen in resistance percentages with lincomycin (63% against 49%) and a slight decrease with tetracycline (66% against 74%).

The association of Flavobacterium columnare strains of high and low virulence with gill tissue of black mollies (Poecilia sphenops).

The ability of a high virulence strain (AJS 1) and a low virulence strain (AJS 4) of Flavobacterium columnare (Flexibacter columnaris) to attach to the gills of black mollies (Poecilia sphenops) was investigated. For that purpose, two groups of 25 black mollies each were immersed in a bath containing 10(6) CFU/ml of F. columnare AJS 1 or AJS 4. At regular intervals from 1 to 12 h after the contact infection, fish were sacrificed and gills, skin, spleen and heart were sampled for bacteriology. Samples of the gills were taken for immunohistochemical and electron microscopic examination. Bacteriological examination proved that the number of gill-associated F. columnare was higher for AJS 1 than for AJS 4. Strain AJS 1 was isolated from the heart and spleen of 6 and 1 of the 16 examined animals, respectively. Strain AJS 4 was not isolated from the internal organs of any fish. When examined immunohistochemically, strain AJS 1 was found closely associated with gill epithelium whereas this was not the case for strain AJS 4. The adherence of bacteria to the gill tissue challenged with the virulent strain AJS 1 was also clearly demonstrated using scanning and transmission electron microscopy. These results indicate that adhesion of F. columnare to the gill tissue constitutes an important step in pathogenesis.

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 (MLSB). 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 MLSB antibiotics, which may be important as alternative therapy for enterococcal infections in humans.

Route of entry and tissue distribution of Yersinia ruckeri in experimentally infected rainbow trout Oncorhynchus mykiss

Yersinia ruckeri is the causative agent of enteric redmouth disease, which leads to significant losses in salmonid aquaculture worldwide. Despite the significance of the disease, little information is available on the pathogenesis. In this study, the portal of entry was investigated using a contact-exposure infection method in rainbow trout Oncorhynchus mykiss with 4 different Y. ruckeri strains. Bacteriological and histological examination revealed the presence of high numbers of bacteria in the gills immediately after infection resulting in a rapid spread of Y. ruckeri in the internal organs. However, only a virulent strain was able to survive and multiply in the host, causing septicaemia and death several days after infection. These findings indicate that gills may be an important site of entry and that Y. ruckeri virulence is related to immune evasion.

Antimicrobial susceptibility pattern of Edwardsiella ictaluri isolates from natural outbreaks of bacillary necrosis of Pangasianodon hypophthalmus in Vietnam

The purpose of this study was to assess the in vitro susceptibility of 64 Vietnamese isolates of Edwardsiella ictaluri, the causal agent of the infectious disease Bacillus Necrosis Pangasius in Pangasianodon hypophthalmus, using the agar dilution technique. All isolates originated from different farms and were collected between 2002 and 2005. None of the isolates displayed acquired resistance to amoxicillin, amoxicillin-clavulanic acid, chloramphenicol, florfenicol, gentamicin, kanamycin, neomycin, and nitrofurantoin. Acquired resistance to streptomycin was detected in 83%, to oxytetracycline in 81%, and to trimethoprim in 71% of the isolates, as indicated by a bimodal distribution of the minimal inhibitory concentrations (MICs) of these antimicrobials. The MICs of enrofloxacin displayed a monomodal distribution with tailing toward the higher MIC values, possibly indicating reduced susceptibility of a minority of isolates (3 out of the 64). For the quinolone antimicrobial agents flumequin and oxolinic acid, acquired resistance was encountered in 8% and 6% of the strains, respectively. All strains were intrinsically resistant to the polypeptide antimicrobial agent colistin. Seventy-three percent of the isolates were shown to have acquired resistance to at least three antimicrobial agents. The results of this study emphasize the strict need to control both the prophylactic and curative use of antimicrobial agents in Vietnamese aquaculture.

Prevalence of Helicobacter pullorum among Patients with Gastrointestinal Disease and Clinically Healthy Persons

ABSTRACT Feces from 531 patients with gastroenteritis and from 100 clinically healthy individuals were tested for Helicobacter pullorum by use of PCR. Samples positive by PCR were qualified for isolation. H. pullorum DNA was demonstrated to be present in feces from 4.3% of patients with gastrointestinal disease but also in feces from 4.0% of clinically healthy persons. One strain was isolated from one patient with gastrointestinal disease.

Antibiotic Resistance among Fecal Indicator Bacteria from Healthy Individually Owned and Kennel Dogs

Escherichia coli and Enterococcus faecalis strains isolated from anal swabs of clinically healthy dogs were examined for the presence of acquired antimicrobial resistance. The strains originated from dogs of 92 different owners and from eight breeding kennels. The purpose of the present study was to evaluate the resistance situation in the intestinal flora of the dog to assess the possible role of the dog flora as a reservoir of antimicrobial resistance. Multiple resistance was rarely found in E. coli strains collected from individually owned dogs, in contrast with strains from kennel dogs. Resistance to ampicillin, trimethoprim, and sulfamethoxazole was significantly less prevalent in E. coli from privately owned dogs than in strains from kennel dogs. Resistance rates against tetracycline and macrolides were unexpectedly high in E. faecalis strains. Two and three E. faecalis strains from individually owned dogs and kennel dogs, respectively, were resistant to gentamicin, an antibiotic often used for treating enterococcal infections in humans. This study demonstrates that resistance percentages may fluctuate with the choice of dog population. The observed antimicrobial resistance percentages indicate that the flora of healthy dogs may act as a reservoir of resistance genes.