Abstract
Tightly coiled bacteria are common inhabitants of the gastric mucosae of cats and there is considerable debate whether feline helicobacters are commensal or pathogenic organisms. To determine the prevalence of Helicobacter species and gastric histopathological findings, gastric mucosa samples of 56 stray cats were collected from cardia, fundus, body, antrum and pylorus at necropsy. The samples were examined by urease test, cytology, histopathology and culture. Helicobacter species were detected in 53 cats (94.6%) by at least one detection method. Urease test results were positive in gastric samples from 50 (89.3%) cats. Cytological and histological evaluations revealed Helicobacter species in 52 (92.8%) and 50 (89.2%) cats, respectively. Helicobacter species organisms were not cultured from any cat. Regardless of the presence of gastric bacteria, most of the cats had mild to moderate gastritis. These data reveal a high prevalence of Helicobacter species in stray cats from Niterói, Brazil.
In early reports, large and tightly coiled organisms were considered to be innocuous commensal organisms in cats, but latter studies documented the association of these organisms with chronic gastritis and gastric lymphoma. 1,2 These organisms include mainly Helicobacter felis, Helicobacter bizzozeronii, Helicobacter salomonis and a Helicobacter-like organism (HLO). 3 In humans, they are a rare cause of gastric pathology and represent a mixture of species for which a zoonotic origin is suspected. 1,3 The global prevalence of Helicobacter species infection in cats varies from 40% to 100%, 3,4 and geographic variations may partially account for these differences. Considering the lack of data from cats in Brazil, the aims of this study were to investigate the prevalence of Helicobacter species in cats, if these organisms were culturable, if there were differences in bacterial distribution among the gastric regions and if naturally occurring gastric bacteria were associated with gastritis in cats.
Samples were collected from the stomachs of 56 stray cats (25 male and 31 female and ages ranging from 2 months to 13 years) scheduled to be euthanased by the Municipal Zoonosis Control Center of Niterói City. The samples were collected immediately after euthanasia. At necropsy, stomachs were removed, opened along the greater curvature, and examined. Samples from cardia, fundus, body, antrum and pylorus were removed for urease testing, cytology, histopathology and culture. For the urease test, gastric mucosal specimens were incubated in tubes containing urea broth (10%) and were scored positive if the phenol red indicator turned red within 24 h. The tubes were monitored hourly for 8 h and evaluated for a final time at 24 h to estimate the density of colonisation by Helicobacter species in the different regions of the stomach, by the time the phenol red indicator turned red. 4 Samples for culture were minced in saline and a drop of the material was placed onto Brucella species agar (Difco) containing 7% sheep blood, vancomycin (2.5 mg/ml), amphotericin B (1.25 mg/ml), cefsulodin (1.25 mg/ml) and trimethoprim (1.25 mg/ml) (Oxoid SR 147). The plates were incubated in an anaerobic jar with a microaerophilic gas generating kit (Oxoid BR 056) at 37°C for 7 days. For cytological and histopathological examinations, carbolfuchsin-stained impression smears were viewed in different fields under light microscopy and formalin-fixed gastric mucosal specimens were stained with haematoxylin–eosin (HE) and with Warthin–Starry (WS) stain, respectively. Gastritis was defined as follows: (−) no gastritis, no lymphoid aggregates, <5 leukocytes per high-power field, and normal mucosal epithelium; (+) mild gastritis, fewer than two lymphoid aggregates per low-power field and/or 5–25 leukocytes per high-power field and normal mucosal epithelium; (++) moderate gastritis, more than two lymphoid aggregates per low-power field, and 26–50 or mores leukocytes per high-power field, and/or mild gastric epithelial changes; (+++) severe gastritis, greater than five lymphoid aggregates and/or >50 leukocytes per high-power field and marked epithelial changes. 4 The χ2 analysis was performed on the data to investigate the association between Helicobacter species presence and gastric regions and the detection methods. Results were considered statistically significant at P<0.05. 5
Fifteen cats (26.8%) had gross changes of the gastric mucosa including hyperaemia (n=13), multiple petechiaes in the body and fundus (n=3) and ulcers (1 cm in diameter) in the antrum and fundus (n=2). The urease test was positive for samples from 50/56 cats (89.3%). All the gastric regions from 44 cats (78.5%) were urease positive, while all the gastric regions from six cats (10.7%) were urease negative. Most of fundus (75%), body (73.2%) and antrum (69.6%) samples became positive in less than 2 h, while 19.7% of the pylorus samples were negative by 24 h (Table 1). The area of gastric mucosa most highly colonised by Helicobacter species has variably been reported as the fundus or corpus. 2,6 However, in this study there was no significant difference in colonisation density between the gastric regions evaluated (P>0.05), as also previously reported. 4,6,8
Table 1.
Urease test results (number and %) as a function of the time interval and gastric regions of the 56 investigated cats.
| Gastric regions | Positive samples | Negative samples | ||
|---|---|---|---|---|
| Within 2 h | Within 2 and 8 h | Within 8 and 24 h | By 24 h | |
| Cardia | 30 (53.6) | 19 (33.9) | 1 (1.8) | 6 (10.7) |
| Fundus | 42 (75.0) | 7 (12.5) | 1 (1.8) | 6 (10.7) |
| Body | 41 (73.2) | 9 (16.1) | – | 6 (10.7) |
| Antrum | 39 (69.6) | 9 (16.1) | 2 (3.6) | 6 (10.7) |
| Pylorus | 28 (50.0) | 12 (21.4) | 5 (8.9) | 11 (19.7) |
Cytological and histological evaluation revealed spiral bacteria in 52 (92.8%) and 50 (89.3%) cats, respectively (Table 2). Four cats had negative results for both methods. The organisms were easily identified on slides stained with WS and carbolfuchsin, but visualisation was not so easy when HE was used. The Helicobacter species organisms were located in mucus, gastric pits and glands and within the cytoplasm of parietal cells. The gastric colonisation appeared to be heaviest in the gastric pits and in the lumen of the gastric glands. Helicobacter species were not cultured from any cat. The urease test, cytology and histopathology were equally efficient in detecting Helicobacter species (P>0.05).
Table 2.
Distribution of Helicobacter species positive samples (number and %) as a function of the detection method and gastric regions of the 56 investigated cats.
| Detection methods | Gastric region | ||||
|---|---|---|---|---|---|
| Cardia | Fundus | Body | Antrum | Pylorus | |
| Urease test | 50 (89.3) | 50 (89.3) | 50 (89.3) | 50 (89.3) | 45 (80.3) |
| Cytology | 51 (91.1) | 51 (91.1) | 50 (89.3) | 52 (92.8) | 42 (75.0) |
| Histology | 48 (85.7) | 49 (87.5) | 50 (89.3) | 50 (89.3) | 46 (82.1) |
The gross observations of gastric ulcers were confirmed histologically by the presence of haemorrhage and severe epithelial changes including necrosis and gastric erosions. Histological findings in the present study ranged from ‘normal’ gastric mucosa to severe gastritis, regardless of the presence of gastric bacteria, and were similar to previous studies. 7,8 Most animals (n=42) had mild gastritis and the remaining animals had moderate (n=9) and severe gastritis (n=3). Two animals were free of lesions and of spiral bacteria by cytology and histopathology. Focal or multifocal lymphoplasmacytic infiltrates were observed in 54 cats (96.4%), lymphoid follicles hyperplasia in 32 cats (57%) and fibrosis in 29 cats (51.8%). Polymorphonuclear leukocytes were rarely present and detected mainly in fundus. Histological changes in the lamina propria including mild mononuclear inflammatory infiltration, the presence of lymphoid follicles, fibrosis and glandular degeneration are commonly reported in cats with Helicobacter species infection. However, in this study no correlation was found between gastritis and Helicobacter species infection. Other investigations also have failed to detect any correlation between gastritis and Helicobacter species infection, as both infected and uninfected cats showed the same type and quantity of lesions. 2,6,9,10
The results of this study agree other studies, which frequently suggested the presence of Helicobacter species in cats, with a prevalence higher than 40%. 3,4 In our study, 53/56 cats (94.6%) had gastric spiral bacteria identified by at least one detection method. As the attempts to culture the organisms were unsuccessful, they were classified as Helicobacter species based on morphological type (large and tightly coiled organisms) which normally in cats, include mainly Helicobacter heilmannii, an uncultured Helicobacter species, H felis, H bizzozeronii and H salomonis. 10,11 Another closely related species isolated from a cat has been recently described as Helicobacter baculiformis. 11
Our results show a high percentage of stray cats with gastric lesions harboring Helicobacter species and suggest that cats are frequently colonised. However, no obvious relation between the extent of histopathological changes, colonisation density and the distribution of Helicobacter species among the gastric regions was established.
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