Vol. 17, No. 16
THE JOHNS HOPKINS MICROBIOLOGY NEWSLETTER
Monday, April 20, 1998
A. Provided by Marguerite-Hawkins, Epidemiology and Disease Control Program, Division of Outbreak Investigation, Maryland Department of Health and Mental Hygiene.
From April 9, 1998 through April 15, 1998, 10 outbreaks have been reported to the Maryland Department of Health and Mental Hygiene as follows: Six cases of food-related gastroenteritis, 3 cases of Hepatitis A and one case of confirmed N. meningitidis in an adult.
B. The Johns Hopkins Hospital. Information provided by Dr. Frank Holmes, Dept. of Pathology.
Case Report
A twelve year-old white male with a history of chronic immune thrombocytopenic purpura was seen by the pediatric gastroenterology service for intermittent hematemesis and hematochezia. He underwent colonoscopy to rule out the presence of an underlying inflammatory bowel disease or arteriovenous malformation. The only notable finding was the presence of intestinal spirochetosis. Because of the high incidence of intestinal spirochetosis in male homosexuals, concerns of possible sexual abuse were raised. The patient was evaluated by the adolescent medicine service, but no evidence of sexual abuse or sexually transmitted disease was discovered.
Intestinal Spirochetosis
Although spirochetes have been noted in human feces since the end of the last century, the attachment of spirochetes to the surface of the colonic mucosa was first described in 1967 and referred to as intestinal spirochetosis (IS). Subsequently, there has been considerable controversy regarding the significance of this finding. While some patients with IS have various gastrointestinal complaints, such as diarrhea, rectal bleeding, or abdominal pain, others apparently are totally asymptomatic. In addition, some patients show clinical improvement with antibiotics (metronidazole has been shown to eliminate the spirochetes), but others show no improvement in their symptoms with antibiotic use or improve without antibiotic therapy. The fact that spirochetes have been demonstrated in the stool, colon, and appendix of apparently healthy individuals and in a wide variety of intestinal diseases, including carcinoma of the colon, adenomatous polyps, and inflammatory bowel disease, further suggests that intestinal spirochetes may be non-pathogenic commensals. On the other hand, IS has been noted as a cause of diarrhea in pigs and dogs, and experimental infections of pigs and birds with human isolates of this organism have led to intestinal disease, strongly suggesting that the organisms might in fact have pathogenic potential.
The disease has a worldwide distribution with differing rates of prevalence. Studies of unselected Europeans revealed spirochetes in 2.5 to 9% of rectal biopsy specimens, whereas 64% of individuals from southern India had IS in one study. The prevalence of IS in patients with abdominal symptoms necessitating sigmoidoscopy has been reported to be 1.9 to 6.9%. One interesting finding is that IS is seen much more frequently in noninflamed appendices removed for suspected appendicitis (9.8 to 12.6%), than in appendices removed incidentally (1.9 to 3.7%) or in those with proven acute appendicitis (0.7 to 4.4%), suggesting that IS involving the appendix can mimic acute appendicitis.
A significantly higher prevalence of IS is seen in homosexual males (both HIV-positive and negative) attending sexually transmitted disease clinics, among whom the prevalence reaches 30 to 53.7%. The high frequency of coinfections with other organisms makes it difficult to determine the clinical significance of IS in this group. In particular, infections with Neisseria gonorrhoeae and Entamoeba histolytica have been seen commonly with IS. Furthermore, one study could find no difference in the presence or type of symptoms, gross mucosal appearance at colonoscopy, type of sexual practice, or history of antibiotic use in homosexual men with and without IS.
The association between IS and sexual abuse has not been well studied. The main reason for the connection seems related to the high incidence of IS in homosexual men. However, the exact route of infection in IS remains obscure. Further study is needed to determine if the organism is sexually transmitted or simply a commensal that may become opportunistic in the presence of an altered colonic flora or other factors such as immunosuppression.
Pathologic Findings
The spirochetes have been seen in the colon and appendix, but no other location in the gastrointestinal tract has been reported. Colorectal biopsies in patients with IS reveal a subtle thickening or accentuation of the colonic brush border, which appears deeply stained with hematoxylin. The organisms are found diffusely along the surface of the mucosa with only superficial extension into the depths of the crypts. The organisms tend to spare the goblet cells. In most cases, no inflammatory reaction to the organism is observed. Identification of the spirochetes can be enhanced by the use of the Warthin-Starry stain. Ultrastructural studies show spirochetes aligned in parallel and embedded in the luminal border of the absorptive cells. There is blunting or loss of the normal microvilli. Occasionally, organisms are found within the cytoplasm of the epithelial cell or within macrophages in the lamina propria. Such penetration is not always associated with clinical disease.
Microbiology
Most studies of IS have involved histologic examination of biopsy material without concurrent bacterial culture. However, successful isolation of spirochetes from stool or biopsy specimens in patients with histologically-verified IS has occurred. One early study in 1982 identified the organism as Brachyspira aalborgi. Since then, most studies have isolated a different organism, Serpulina pilosicoli. This organism has recently been described as the agent of porcine IS. Infection of pigs with S. pilosicoli is widespread and is associated with poor growth rates, colitis, and diarrhea. S. pilosicoli also infects dogs and birds and is associated with diarrhea in these animals too.
Organisms are not always culturable from patients with histologically-proven IS. One study isolated spirochetes in only 50% of the cases. This finding suggests that culture alone may underestimate the true prevalence of infection. The spirochetes grow under strictly anaerobic conditions in an atmosphere of 5 to 10% CO2 at 37'C on trypticase soy agar plates with 5 to 10% blood added. Isolates form colonies in 3 to 5 days and generally show weak beta-hemolysis.
References
Padmanabhan V, Dahlstrom J, Maxwell L, et al. Invasive intestinal spirochetosis: A report of three cases. Pathology 1996; 28:283-86.
Teglbjaerg PS. Intestinal Spirochetosis. Current Topics in Pathology 1990; 81:247-56.
Trivett-Moore NL, Gilbert GL, Law CLH, et al. Isolation of Serpulina pilosicoli from rectal biopsy specimens showing evidence of intestinal spirochetosis. J. Clin. Microbiol. 1998; 36:261-65.
Trott DJ, Jensen NS, Girons IS, et al. Identification and characterization of Serpulina pilosicoli isolates recovered from the blood of critically ill patients. J. Clin. Microbiol. 1997; 35:482-85.