Diarrheogenic bacterial enteritis in acquired immune deficiency syndrome: a light and electron microscopy study of 52 cases

Evaluation of the ultrastructure of the small intestine of hiv infected children by transmission and scanning electronic microscopy

OBJECTIVES

To describe HIV children's small intestinal ultrastructural findings.

METHODS

Descriptive, observational study of small intestine biopsies performed between August 1994 and May 1995 at São Paulo, SP, Brazil. This material pertained to 11 HIV infected children and was stored in a laboratory in paraffin blocks. Scanning and transmission electronic microscopy were used to view those intestine samples and ultrastructural findings were described by analyzing digitalized photos of this material. Ethical Committee approval was obtained.

RESULTS

In most samples scanning microscopy showed various degrees of shortening and decreasing number of microvilli and also completes effacements in some areas. Derangement of the enterocytes was seen frequently and sometimes cells well defined borders limits seemed to be loosened. In some areas a mucous-fibrin like membrane with variable thickness and extension appeared to partially or totally coat the epithelial surface. Fat drops were present in the intestinal lumen in various samples and a bacterium morphologically resembling bacilli was seen in two occasions. Scanning microscopy confirmed transmission microscopy microvilli findings and also showed little "tufts" of those structures. In addition, it showed an increased number of vacuoles and multivesicular bodies inside various enterocytes, an increased presence of intraepithelial lymphocytes, mitochondrial vacuolization and basement membrane enlargement in the majority of samples analyzed. However, some samples exhibited normal aspect.

CONCLUSIONS

Our study showed the common occurrence of various important intestinal ultrastructural alterations with variable degrees among HIV infected children, some of them in our knowledge not described before.

Long-term treatment of NZB mice with anti-CD4 results in wasting disease, lymphoid atrophy and chronic diarrhea

In this paper, we have shown that long-term treatment of NZB mice with anti-CD4 antibody results in four major pathological effects: firstly the development of a severe wasting disease; secondly lymphoid atrophy of the thymus, spleen, mesenteric lymph node and Peyers patches (PP); thirdly, severe chronic ulcerative colitis and fourthly a neutrophilia with neutrophil infiltration in the spleen, liver and mesenteric lymph nodes. At the same time, mice subjected to anti-CD4 treatment showed a reduction in the microbial diversity in ileal walls and contents, as well as in colonic contents, together with overgrowth of E. coli in the intestinal lumen and wall. In addition, there was the appearance of large numbers of spiral shaped bacteria on the mucosal surface often associated with colonic ulceration.

Changes of colonic mucosal end-artery in human immunodeficiency virus-positive patients with chronic diarrhea due to nonspecific colitis

AIM: To observe the pathological changes of colonic mucosal end-artery in human immunodeficiency virus-positive [HIV(+)] patients with nonspecific colitis-caused chronic diarrhea.

METHODS: Colonoscopic pictures from 300 HIV-negative patients (3000 pictures in total) and 32 HIV(+) patients (600 pictures in total) with chronic diarrhea due to nonspecific colitis were comparatively analyzed. The pathological sections from the 32 HIV(+) patients were observed for analyses of capillary vessel distributions and mucosal bleedings in lamina propria.

RESULTS: The pictures from 9 HIV(+) patients with nonspecific colitis-caused chronic diarrhea showed ring-like changes of colonic mucosal end-artery with diameters of 1 to 2 mm, which became larger after bleeding. The same changes were not found in the 3000 pictures from the HIV-negative patients. In addition to chronic non-specific inflammation, mucosal bleeding and conglomeration of red blood cells in lamina propria were observed in the pathological sections of mucosal tissue from 13 HIV(+) patients, and mucosal vascular proliferation in lamina propria was found in 27 HIV(+) patients.

CONCLUSION: The ring-like change of colonic mucosal end-artery may be a special sign in HIV(+) patients with chronic diarrhea due to nonspecific colitis.

Light microscopic and electron microscopic diagnosis of gastrointestinal opportunistic infections in HIV-positive patients

The surgical pathologist is expected to recognise gastrointestinal opportunistic infections in biopsies from HIV-positive patients, and patients immunocompromised iatrogenically by cancer therapy, steroid treatment and transplantation immunosuppression regimes. This review article presents the diagnostic features in gastrointestinal biopsies of microsporidia, cyclospora, isospora, cryptosporidia, mycobacteria, adenovirus, enteropathogenic bacteria, cryptococcus and leishmania. All of these infections have been diagnosed at our hospital in Sydney, Australia, since the AIDS epidemic began. A protocol for the examination and assessment of these gastrointestinal biopsies is presented and discussed.

Gastrointestinal infections

Advances in public health have reduced the risk of contracting certain enteric diseases, but many remain, and new pathogens have emerged and/or recently have been discovered. The pathogenic agents are varied and consist of a variety of bacteria and select viruses and parasites. Selected use of microbiologic assays to detect these pathogens is encouraged. When tests are ordered non-judiciously, costs rapidly accrue. The age of the patient, time of year, travel history, and clinical presentation all provide clues to the etiologic agent. Microbiologic assays should be used judiciously to confirm or exclude the likely infectious agents.

The histopathology of 103 consecutive colonoscopy biopsies from 82 symptomatic patients with acquired immunodeficiency syndrome: original and look-back diagnoses

OBJECTIVE

To compare the primary diagnoses assigned by general surgical pathologists on a series of 103 consecutive colon biopsies from individuals infected with human immunodeficiency virus (HIV) with diagnoses rendered by a pathologist with extensive experience in gastrointestinal pathology in HIV/acquired immunodeficiency syndrome.

DESIGN

New sections were cut from paraffin blocks of 103 consecutive colon biopsies taken during colonoscopies of 82 different HIV-infected patients; all new sections were stained with hematoxylin-eosin. These individuals either had negative stool studies or had failed to respond to therapy and had chronic large bowel symptoms, such as frequent small volume-type diarrhea, tenesmus, and/or bright red blood per rectum. Immunohistochemistry for cytomegalovirus (CMV) was performed on 18 of 22 specimens originally diagnosed with CMV colitis.

RESULTS

The initial study yielded 70 (68%) negative or nonspecific diagnoses, 22 (21%) cases of CMV colitis, 5 (5%) Cryptosporidium diagnoses, 2 cases each of adenomatous polyps and Kaposi sarcoma, and 1 case each of spirochetosis and squamous cell carcinoma of the anorectum. Review of the recuts yielded 64 (62%) negative or nonspecific diagnoses, 12 (12%) new adenovirus infections (3 combined with CMV), and 11 (11%) lone CMV infections. Three attaching and effacing bacterial infections were diagnosed, 1 with adenovirus coinfection. A total of 4 spirochetosis cases were found on review. Seven (7%) of the biopsies showed at least 1 coinfection. Nine biopsies had features suggestive of inflammatory bowel disease.

CONCLUSIONS

Colonoscopy with biopsy after negative stool studies or failure to respond to therapy yielded a high proportion of negative or nonspecific diagnoses. Adenovirus and enteropathogenic bacterial infections had been totally overlooked on initial examination. It takes particular experience to evaluate gastrointestinal biopsies from HIV-infected patients.

Identification of enteropathogenic Escherichia coli in simian immunodeficiency virus-infected infant and adult rhesus macaques

Enteropathogenic Escherichia coli (EPEC) was recognized as a common opportunistic pathogen of simian immunodeficiency virus-infected rhesus macaques (Macaca mulatta) with AIDS. Retrospective analysis revealed that 27 of 96 (28.1%) animals with AIDS had features of EPEC infection, and EPEC was the most frequent pathogen of the gastrointestinal tract identified morphologically. In 7.3% of animals dying with AIDS, EPEC represented the sole opportunistic agent of the gastrointestinal tract at death. In 20.8% of cases, it was seen in combination with one or more gastrointestinal pathogens, including Cryptosporidium parvum, Enterocytozoon bieneusi, Mycobacterium avium, Entamoeba histolytica, Balantidium coli, Strongyloides stercoralis, cytomegalovirus, and adenovirus. Clinically, infection was associated with persistent diarrhea and wasting and was more frequent in animals that died at under 1 year of age (P < 0.001, Fisher exact test). The organism was associated with the characteristic attaching and effacing lesion in colonic tissue sections and produced a focal adherence pattern on a HEp-2 assay but was negative for Shiga toxin production as assessed by PCR and a HeLa cell cytotoxicity assay. A 2.6-kb fragment encompassing the intimin gene was amplified and sequenced and revealed 99.2% identity to sequences obtained from human isolates (GenBank AF116899) corresponding to the epsilon intimin subtype. Further investigations with rhesus macaques may offer opportunities to study the impact of EPEC on AIDS pathogenesis and gastrointestinal dysfunction.

Simultaneous intestinal leishmaniasis and mycobacterial involvement in a patient with acquired immune deficiency syndrome

Gastrointestinal involvement is reported in approximately 50% to 93% of patients with human immunodeficiency virus. It is frequently the result of coinfection with several microorganisms. Selective Leishmania intestinal involvement presents with atypical symptoms for visceral leishmaniasis, and may appear as a relapse or as the first manifestation of the disease. The authors present a patient with acquired immune deficiency syndrome who has a history of treated leishmaniasis and gastrointestinal infection by showed Mycobacterium avium intracellulare (MAI). After the new onset of abdominal pain, an intestinal biopsy showed the presence of both MAI and Leishmania in duodenum. Intestinal infection by Leishmania must be included in the differential diagnosis in patients with a previous history of leishmaniasis or travel to an endemic area.

Evaluation of diarrhea in HIV-infected patients

Diarrhea is a major problem for patients infected with HIV: initial studies indicated that 50% of HIV-seropositive patients developed diarrhea, but this may be an underestimate. Diarrhea has an appreciable adverse affect on the quality of life of these patients; also, they use more health care facilities and health care dollars than HIV-positive patients without diarrhea. Individuals who have homosexuality or bisexuality as their HIV risk factor are more likely to have diarrhea and to have an enteric pathogen identified as the cause of diarrhea than are patients who have heterosexuality or intravenous drug use as their risk factor.

Endoscopic evaluation of chronic human immunodeficiency virus-related diarrhea: is colonoscopy superior to flexible sigmoidoscopy?

OBJECTIVES

In patients with chronic human immunodeficiency virus (HIV)-related diarrhea undergoing lower endoscopy, the decision to perform flexible sigmoidoscopy or colonoscopy is controversial. The purpose of this study is twofold: 1) to evaluate the diagnostic yield of colonoscopy in a large group of patients with chronic HIV-related diarrhea and negative stool studies, and 2) to determine whether colonoscopy is superior to flexible sigmoidoscopy in this setting.

METHODS

All HIV-infected patients with chronic diarrhea who were referred for diagnostic colonoscopy at Bellevue Hospital Center between January 1992 and December 1996 were identified. Patient charts, pathology reports, and endoscopy records were reviewed.

RESULTS

During the 5-yr study period, 317 consecutive patients with chronic unexplained diarrhea undergoing colonoscopy were identified. A potential cause of diarrhea was found in 116 patients (36.6%). Cytomegalovirus was the most common pathogen detected (24%). The yield of colonoscopy was significantly higher in patients with a CD4 count of <100 cells/mm3 than in those with higher CD4 counts (44.8% vs 6.4%, p < 0.0001). Thirty percent of pathogens and 75% of lymphomas were identified only on biopsies taken from the proximal colon, well beyond the reach of the flexible sigmoidoscope. Importantly, 94% of the pathogens that were found only in the proximal colon were organisms for which effective therapy is currently available.

CONCLUSIONS

Colonoscopy is superior to flexible sigmoidoscopy in HIV-infected patients with chronic unexplained diarrhea. If flexible sigmoidoscopy had been performed instead of colonoscopy, 30% of pathogens would have been missed and 75% of lymphomas would have escaped detection.

HEp-2 cell adherence patterns, serotyping, and DNA analysis of Escherichia coli isolates from eight patients with AIDS and chronic diarrhea

Three morphologic patterns of interaction between bacteria and enterocytes have been observed in colonic biopsy specimens from AIDS patients with chronic diarrhea in the United States. The DNA encoding virulence factors and the HEp-2 cell adherence patterns of Escherichia coli strains isolated from the stools of eight symptomatic AIDS patients were compared with those of five control strains with known adherence patterns. One clinical isolate from a patient with attaching-and-effacing enteropathy displayed the localized adherence attaching-and-effacing pattern typical of enteropathogenic E. coli on HEp-2 cells, five isolates displayed the "stacked-brick" aggregative adherence pattern typical of enteroaggregative E. coli strains, and one isolate showed the pattern characteristic of diffusely adherent E. coli. One patient's isolate displayed features of all three patterns. No clinical isolate hybridized with standard probes for enteropathogenic, enteroaggregative, diffusely adherent, enterotoxigenic, and enteroinvasive E. coli strains. Thus, isolates from symptomatic AIDS patients in the United States can display the same interactive patterns with HEp-2 cells as the agents of pediatric or traveler's diarrhea, but lack their typical virulence factors.

Pathophysiology of HIV-associated diarrhea

Considerable advances have been made in the evaluation and treatment of diarrhea in HIV-infected individuals, although gaps in knowledge still exist. The availability of newer and more powerful antiretroviral agents should allow a better definition of the effect of local HIV infection on intestinal function. Further attention to the pathophysiology of diarrhea should lead to improvements in diagnosis and treatment.

Gastrointestinal pathology in HIV-infected patients

Specific pathologic processes, particularly oral, esophageal, and intestinal infections, are common in the alimentary tract of AIDS patients. Many of these diseases are adequately assessed only by biopsy with histologic examination. Most are rare or unreported in immunocompetent hosts and are easily missed by those not familiar with them. This article describes the gross or endoscopic and histologic appearances and the diagnostic criteria for enteric pathologic processes seen in HIV-infected individuals.

Diarrheal diseases associated with HIV infection

Diarrhea is a major complication of HIV infection and adversely impacts health care costs, quality of life, and even survival of patients. There is a wide variety of potential causes of diarrhea in HIV-infected patients, and the number of pathogens found continues to increase with time. In addition, there is some controversy concerning the role of some organisms in the pathogenesis of diarrhea and the appropriate diagnostic evaluation of affected patients. This article reviews our current understanding of these pathogens and some of the diagnostic and therapeutic approaches for diarrhea associated with HIV infection.