Helicobacter fennelliae Localization to Diffuse Areas of Human Intestine, Japan

The site of enterohepatic Helicobacter colonization/infection in humans is still unknown. We report microbiologically and histopathologically confirmed H. fennelliae localization in the large intestine in an immunocompromised patient in Japan. This case contributes to better understanding of the life cycle of enterohepatic Helicobacter species.

(Figure 1, panels D-F).Gram staining showed gramnegative spiral bacilli in the tissue obtained from the cecum and transverse colon (Figure 2, panel A).Hematoxylin and eosin staining of the biopsied tissues showed only slight inflammation with very mild edema of the mucosa in both cases, preservation of goblet cells, and mild leukocytic infiltration.In contrast, Warthin-Starry silver staining showed bacteria with spiral structures in crypts of the cecum, ascending colon, transverse colon, descending colon, and sigmoid colon but not in the rectal tissues (Figure 2, panels B-D).Culture of the tissue suspension showed bacterial growth in all tissues from the cecum, the ascending, transverse, descending, and sigmoid colon, and the rectum, which we identified as H. fennelliae by MALDI-TOF mass spectrometry, confirming the localization of H. fennelliae.

Conclusions
This study provides evidence for the localization of H. fennelliae in the intestinal tract.This confirmation may lead to better understanding of the life cycle of enterohepatic Helicobacter species.Reports of human infections with H. cinaedi are scarce but are gradually increasing (3)(4)(5), whereas those of H. fennelliae are even scarcer (2).Enterohepatic Helicobacter species cannot be identified based on biochemical characteristics alone.A definitive diagnosis requires identification by PCR, MALDI-TOF mass spectrometry, or both (3,7).Detection from stool and tissue is also difficult by routine culture methods, and many cases might have been overlooked (3).
Some previous reports have focused on disturbance of the intestinal tract by enterohepatic Helicobacter in animal models, but not in humans (8).Experiments conducted on pigtailed macaques given H. cinaedi and H. fennelliae orally showed that diarrhea, bacteremia, and localized inflammation of the colon were seen 3-7 days after exposure and that organisms remained detectable in stools for 3 weeks after diarrhea resolved.Researchers noted no acute inflammatory findings or microbial adherence in the small or large intestine in animals in the H. cinaedi group; however, they did note lymphoid hyperplasia caused by immune stimulation in the Peyer's patches.In contrast, our case of a human patient with recurrent bacteremia showed broad localization of H. fennelliae in the crypts of the colonic mucosa, almost without background inflammation in the intestinal tract or grossly visible disruption of the mucosal barrier.The lack of inflammation and mucosal abnormality may reflect the fact that the patient was immunocompromised with hypogammaglobulinemia and lacked adequate intestinal immunity, which possibly caused bacteremia.Fujiya et al. described a patient with H. fennelliae bacteremia who had been receiving anticancer chemotherapy that included carboplatin, a possible risk factor of mucositis (9).They mentioned the possibility of the damaged intestinal mucosa being the route of entry for the pathogen.However, retrospective Warthin-Starry silver staining of the biopsied erosive mucosal tissue in the cecum from the first colonoscopy in the patient we describe showed no spiral bacillus-like structures in the mucosal lesions.Furthermore, we detected no gross abnormalities in the second colonoscopy.Given the absence of abnormal mucosal findings in our patient, immunoglobulin-associated impairment of intestinal immunity may be more important than damage to the intestinal mucosa in prevention of pathogen entry.This hypothesis would explain the mechanism caused in a previously reported patient with X-linked agammaglobulinemia, who developed recurrent bacteremia with persistent detection of H. cinaedi in stools despite repeated courses of antimicrobial therapy and selective decontamination of the digestive tract (10).
We report the microbiological and histopathological confirmation of H. fennelliae localization in the large intestine in an immunocompromised patient.Only 1 other report, regarding a patient in Japan, had enterohepatic Helicobacter detected pathologically (11).That patient contracted Clostridioides difficile enteritis after treatment for H. cinaedi bacteremia that resulted in bloody stools.Colonoscopy revealed pseudomembranous mucosal tissue in the cecum, where H. cinaedi was detected and confirmed pathologically.The authors stated, however, that it was impossible to determine whether the enteritis found in their patient was caused by C. difficile or H. cinaedi and whether it was localized at the time of the onset of H. cinaedi bacteremia.In our case, H. fennelliae was already present in stool culture at the time of the initial episode of bacteremia.Moreover, when the recurrent bacteremia was detected, persistence of the localized pathogen in the intestinal tract after the resolution of the first episode of bacteremia was confirmed.Both results suggest entry of H. fennelliae via the intestinal tract.We believe that investigating carriage rate or pathogenicity of enterohepatic Helicobacter in humans will help to better establish the disease concept.The colonic mucosa shows mild leukocytic infiltration.C) Histologic findings in a biopsy specimen taken from the transverse colon with Warthin-Starry silver staining (original magnification ×200).Bacteria are aggregated in crypts (arrowheads) D) Morphologic features of bacteria obtained from the transverse colon with Warthin-Starry silver staining (original magnification ×1,000).A cluster of spiral bacilli was observed.

Figure 1 .
Figure 1.Colonoscopy findings from a man in Japan who had recurrent Helicobacter fennelliae bacteremia.A-C) First colonoscopy findings in the transverse colon (A), in the sigmoid colon (B), and in the rectum (C).D-F) Second colonoscopy findingsin the transverse colon (D), in the sigmoid colon (E), and in the rectum (F).Yellow arrows indicate randomly biopsied sites.Colonic vascular permeability was preserved, and there were no significant findings for inflammation.

Figure 2 .
Figure2.Microscopic findings in ileocolonic biopsy specimens (second colonoscopy) in a man in Japan who had recurrent Helicobacter fennelliae bacteremia.A) Morphologic features of the bacteria in a cecal tissue suspension with Gram staining (original magnification ×2,000).Arrow indicates gram-negative spiral bacilli.B) Histologic findings in a biopsy specimen taken from the transverse colon with hematoxylin-eosin staining (original magnification ×200).The colonic mucosa shows mild leukocytic infiltration.C) Histologic findings in a biopsy specimen taken from the transverse colon with Warthin-Starry silver staining (original magnification ×200).Bacteria are aggregated in crypts (arrowheads) D) Morphologic features of bacteria obtained from the transverse colon with Warthin-Starry silver staining (original magnification ×1,000).A cluster of spiral bacilli was observed.