The microbiome of the appendix differs in patients with and without appendicitis: A prospective cohort study

BACKGROUND

Appendicitis seems to be a disease of infectious origin, but the detailed pathogenesis is unknown. We aimed to investigate the microbiome of the appendix lumen in patients with and without appendicitis, including a comparison of the subgroups of complicated versus uncomplicated appendicitis.

METHODS

This prospective observational cohort study included adult patients undergoing laparoscopic appendectomy for suspected appendicitis. According to histopathologic findings, the investigated groups consisted of patients with and without appendicitis, including subgroups of complicated versus uncomplicated appendicitis based on the surgical report. A swab of the appendix lumen was analyzed for genetic material from bacteria with shotgun metagenomics, and outcomes included analyses of microbiome diversity and differential abundance of bacteria.

RESULTS

A total of 53 swabs from patients with suspected appendicitis were analyzed: 42 with appendicitis (16 complicated) and 11 without appendicitis. When comparing patients with and without appendicitis, they were equally rich in bacteria (alpha diversity), but the microbiome composition was dissimilar between these groups (beta diversity) (P < .01). No consistent bacterial species were detected in all patients with appendicitis, but a least 3 genera (Blautia, Faecalibacterium, and Fusicatenibacter) and 2 species, Blautia faecis and Blautia wexlerae, were more abundant in patients without appendicitis. For the subgroups complicated versus uncomplicated appendicitis, both measures for microbiome diversity were similar.

CONCLUSION

The appendix microbiome composition of genetic material from bacteria in adult patients with and without appendicitis differed, but the microbiome was similar for patients with complicated versus uncomplicated appendicitis. Trial registration NCT03349814.

Beyond a vestigial organ: effects of the appendix on gut microbiome and colorectal cancer

The role of appendectomy in the pathogenesis of colorectal cancer (CRC) is a recent topic of contention. Given that appendectomy remains one of the most commonly performed operations and a first-line management strategy of acute appendicitis, it is inherently crucial to elucidate the association between prior appendectomy and subsequent development of CRC, as there may be long-term health repercussions. In this review, we summarize the data behind the relationship of CRC in post-appendectomy patients, discuss the role of the microbiome in relation to appendectomy and CRC pathogenesis, and provide an appraisal of our current understanding of the function of the appendix. We seek to piece together the current landscape surrounding the microbiome and immunological changes in the colon post-appendectomy and suggest a direction for future research involving molecular, transcriptomic, and immunologic analysis to complement our current understanding of the alterations in gut microbiome.

B cell immune profiles in dysbiotic vermiform appendixes of pancreatic cancer patients

Pancreatic ductal adenocarcinoma (PDAC) remains one of the deadliest solid tumors and is resistant to immunotherapy. B cells play an essential role in PDAC progression and immune responses, both locally and systemically. Moreover, increasing evidence suggests that microbial compositions inside the tumor, as well as in the oral cavity and the gut, are important factors in shaping the PDAC immune landscape. However, the gut-associated lymphoid tissue (GALT) has not previously been explored in PDAC patients. In this study, we analyzed healthy vermiform appendix (VA) from 20 patients with PDAC and 32 patients with colon diseases by gene expression immune profiling, flow cytometry analysis, and microbiome sequencing. We show that the VA GALT of PDAC patients exhibits markers of increased inflammation and cytotoxic cell activity. In contrast, B cell function is decreased in PDAC VA GALT based on gene expression profiling; B cells express significantly fewer MHC class II surface receptors, whereas plasma cells express the immune checkpoint molecule HLA-G. Additionally, the vermiform appendix microbiome of PDAC patients is enriched with Klebsiella pneumoniae, Bifidobacterium animalis, and Adlercreutzia equolifaciens, while certain commensals are depleted. Our findings may suggest impaired B cell function within the GALT of PDAC patients, which could potentially be linked to microbial dysbiosis. Additional investigations are imperative to validate our observations and explore these potential targets of future therapies.

A comprehensive microbial analysis of pediatric patients with acute appendicitis

BACKGROUND

Pathogenesis of pediatric acute appendicitis (AA) is yet to be elucidated. Therefore, we performed a comprehensive microbial analysis of saliva, feces, and appendiceal lumen of AA patients using 16S ribosomal RNA (rRNA) gene amplicon sequencing to elucidate the pathogenesis of pediatric AA.

METHODS

This study included 33 AA patients and 17 healthy controls (HCs) aged <15 y. Among the AA patients, 18 had simple appendicitis, and 15 had complicated appendicitis. Salivary and fecal samples were obtained from both groups. The contents of the appendiceal lumen were collected from the AA group. All samples were analyzed using 16S rRNA gene amplicon sequencing.

RESULTS

The relative abundance of Fusobacterium was significantly higher in the saliva of AA patients as compared to that in HCs (P = 0.011). Bacteroides, Escherichia, Fusobacterium, Coprobacillus, and Flavonifractor were significantly increased in the feces of AA patients, as compared to that in HCs (P = 0.020, 0.010, 0.029, 0.031, and 0.002, respectively). In the appendiceal lumen, Bacteroides, Parvimonas, Fusobacterium, and Alloprevotella were the top bacterial genera with an average relative abundance >5% (16.0%, 9.1%, 7.9%, and 6.0%, respectively).

CONCLUSIONS

The relative abundance of Fusobacterium was high in the appendiceal lumen of pediatric AA patients. Moreover, the relative abundance of Fusobacterium was significantly higher in the saliva and feces of pediatric AA patients than in those of healthy children. These results suggest that ectopic colonization of oral Fusobacterium in the appendix might play an important role in the pathogenesis of pediatric AA.

Acute appendicitis manifests as two microbiome state types with oral pathogens influencing severity

Mounting evidence suggests that acute appendicitis (AA) is not one but two diseases: complicated appendicitis, which is associated with necrosis leading to perforation or periappendicular abscess, and uncomplicated appendicitis, which does not necessarily result in perforation. Even though AA is the most frequent cause of surgery from abdominal pain, little is known about the origins and etiopathogenesis of this disease, much less regarding the different disease types. In this study, we investigated the microbiome (inter-domain amplicon and metagenome sequencing) of samples from the appendix, rectum and peritoneum of 60 children and adolescents with AA to assess the composition and potential function of bacteria, archaea and fungi. The analysis of the appendix microbial community revealed a shift depending on the severity of the AA. This shift was reflected by two major community state types that represented the complicated and uncomplicated cases. We could demonstrate that complicated, but not uncomplicated, appendicitis is associated with a significant local expansion of oral, bacterial pathogens in the appendix, most strongly influenced by necrotizing Fusobacterium spp., Porphyromonas and Parvimonas. Uncomplicated appendicitis, however, was characterized by gut-associated microbiomes. Our findings support the hypothesis that two disease types exist in AA, which cannot be distinguished beyond doubt using standard clinical characterization methods or by analysis of the patient's rectal microbiome. An advanced microbiome diagnosis, however, could improve non-surgical treatment of uncomplicated AA.

The Effects of Deoxynivalenol on the Ultrastructure of the Sacculus Rotundus and Vermiform Appendix, as Well as the Intestinal Microbiota of Weaned Rabbits

Deoxynivalenol (DON) is a mycotoxin found in grains that poses a potential threat to human and animal health, and the gastrointestinal tract is the primary target organ. There are few studies focused on the toxicology of DON to rabbits, especially on the relation among DON, microbiota, and the gut-associated lymphoid tissue. A total of 30 weaned rabbits (35 d) were evenly divided into the control group and DON group (1.5 mg/kg bodyweight (BW)) based on their body weight. After a 24-day trial, the ultrastructures of the sacculus rotundus and vermiform appendix were observed using a scanning electron microscope and transmission electron microscopy. The morphology and microflora in the ileum, caecum, and colon were also examined. The results proved that the ultrastructure of the sacculus rotundus and vermiform appendix, as well as the integrity of the intestinal barrier (especially for the ileum), were impaired after DON was administrated to the rabbits. Compared to the control group, the relative abundance and diversity of the microflora decreased in all three intestinal segments in the DON group, particularly in the ileum and caecum. In conclusion, the toxic effect of DON on weaned rabbits may be performed by destroying the structure of the sacculus rotundus and vermiform appendix, as well as affecting the structure and diversity of the intestinal flora.

Escherichia coli as a carrier of tetracyclines and penicillins resistance in wild pheasant (Phasianus colchicus)

Wild animals like pheasant seem to be a good source of information about human activities. Therefore, the wild pheasants and relative stable appendix microcenosis were selected for antibiotic resistance testing. Penicillin resistance by MALDI-TOF Mass Spectrometry and tetracyclines resistance by genetic methods using specific primers were tested. Differences between tetracycline and penicillin resistance were detected. Results showed high prevalence of resistant Escherichia coli isolated from wild pheasant appendix. E. coli isolated from wild pheasant appendix carried plasmids for penicillins and tetracyclines resistance where they were responsible for enzymatic degradation of penicillin and carried genes for regulating efflux pumps for tetracyclines. Results showed that tetracyclines and penicillins resistance is widespread between wild pheasants with a carrier as Escherichia coli isolated from relative stable microcenosis of appendix.

No appendix necessary: Fecal transplants and antibiotics can resolve Clostridium difficile infection

The appendix has been hypothesized to protect the colon against Clostridium difficile infection (CDI) by providing a continuous source of commensal bacteria that crowd out the potentially unhealthy bacteria and/or by contributing to defensive immune dynamics. Here, a series of deterministic systems comprised of ordinary differential equations, which treat the system as an ecological community of microorganisms, model the dynamics of colon microbiome. The first model includes migration of commensal bacteria from the appendix to the gut, while the second model expands this to also include immune dynamics. Simulations and simple analytic techniques are used to explore dynamics under biologically relevant parameters values. Both models exhibited bistability with steady states of a healthy state and of fulminant CDI. However, we find that the appendix size was much too small for migration to affect the stability of the system. Both models affirm the use of fecal transplants in conjunction with antibiotic use for CDI treatment, while the second model also suggests that anti-inflammatory drugs may protect against CDI. Ultimately, in general neither the appendiceal migration rate of commensal microbiota nor the boost to antibody production could exert an appreciable impact on the stability of the system, thus failing to support the proposed protective role of the appendix against CDI.

[BACTERIOLOGICAL ASPECTS OF AN ACUTE APPENDICITIS]

Peculiarities of microflora in the appendix mucosa and abdominal exudate in different morphological forms of an acute appendicitis (AA) were studied up. In accordance to the bacteriological investigations data, anaerobic, and aerobic microorganisms in AA were revealed in a monoculture and in association, more frequently--obligate anaer- obes (bacteroids) with E. coli--in 82 (80.39%) observations, staphylococcus--in 52 (50.98%), fecal streptococcus--in 19 (18.63%). With progression of inflammatory process and destructive changes in the appendix wall the quantity of bacteroids and enterobacteria have had enhanced, while the quantity of lacto- and bifidumflora-- reduced.

Intestinal stem cells and intestinal homeostasis in health and in inflammation: A review

BACKGROUND

The human intestine is a complex group of organs, highly specialized in processing food and providing nutrients to the body. It is under constant threat from microbials and toxins and has therefore developed a number of protective mechanisms. One important mechanism is the constant shedding of epithelial cells into the lumen; another is the production and maintenance of a double-layered mucous boundary in which there is continuous sampling of the luminal microbiota and a persistent presence of antimicrobial enzymes. However, the gut needs commensal bacteria to effectively break down food into absorbable nutrients, which necessitates constant communication between the luminal bacteria and the intestinal immune cells in homeostasis. Disruption of homeostasis, for whatever reason, will give rise to (chronic) inflammation.

DISCUSSION

Both medical and surgical management of this disruption is discussed.

[DYNAMICS OF INDICES OF A LOCAL IMMUNITY IN AN ACUTE APPENDICITIS]

Abstract The results of investigation on dynamics of a local immunity indices in an acute appendicitis, depending on the pathological process stage as well as on bacteriological investigation of parietal microflora of processus vermicularis, were adduced. The sIgA and lisocymal dynamics have witnessed that while a destructive process progressing their concentration was enhanced, and in a gangrenous acute appendicitis they practically disappeared. Due to affection of a barrier function of the processus vermicularis wall a favorable conditions were created for the microorganisms intramural translocation as well as to abdominal cavity.

Culture-independent evaluation of the appendix and rectum microbiomes in children with and without appendicitis

PURPOSE

The function of the appendix is largely unknown, but its microbiota likely contributes to function. Alterations in microbiota may contribute to appendicitis, but conventional culture studies have not yielded conclusive information. We conducted a pilot, culture-independent 16S rRNA-based microbiota study of paired appendix and rectal samples.

METHODS

We collected appendix and rectal swabs from 21 children undergoing appendectomy, six with normal appendices and fifteen with appendicitis (nine perforated). After DNA extraction, we amplified and sequenced 16S rRNA genes and analyzed sequences using CLoVR. We identified organisms differing in relative abundance using ANOVA (p<0.05) by location (appendix vs. rectum), disease (appendicitis vs. normal), and disease severity (perforated vs. non-perforated).

RESULTS

We identified 290 taxa in the study's samples. Three taxa were significantly increased in normal appendices vs. normal rectal samples: Fusibacter (p = 0.009), Selenomonas (p = 0.026), and Peptostreptococcus (p = 0.049). Five taxa were increased in abundance in normal vs. diseased appendices: Paenibacillaceae (p = 0.005), Acidobacteriaceae GP4 (p = 0.019), Pseudonocardinae (p = 0.019), Bergeyella (p = 0.019) and Rhizobium (p = 0.045). Twelve taxa were increased in the appendices of appendicitis patients vs. normal appendix: Peptostreptococcus (p = 0.0003), Bilophila (p = 0.0004), Bulleidia (p = 0.012), Fusobacterium (p = 0.018), Parvimonas (p = 0.003), Mogibacterium (p = 0.012), Aminobacterium (p = 0.019), Proteus (p = 0.028), Actinomycineae (p = 0.028), Anaerovorax (p = 0.041), Anaerofilum (p = 0.045), Porphyromonas (p = 0.010). Five taxa were increased in appendices in patients with perforated vs. nonperforated appendicitis: Bulleidia (p = 0.004), Fusibacter (p = 0.005), Prevotella (p = 0.021), Porphyromonas (p = 0.030), Dialister (p = 0.035). Three taxa were increased in rectum samples of patients with appendicitis compared to the normal patients: Bulleidia (p = 0.034), Dialister (p = 0.003), and Porphyromonas (p = 0.026).

CONCLUSION

Specific taxa are more abundant in normal appendices compared to the rectum, suggesting that a distinctive appendix microbiota exists. Taxa with altered abundance in diseased and severely diseased (perforated) samples may contribute to appendicitis pathogenesis, and may provide microbial signatures in the rectum useful for guiding both treatment and diagnosis of appendicitis.

Appendectomy and Clostridium difficile colitis: Relationships revealed by clinical observations and immunology

Advances in understanding the interaction between the human immune system and the microbiome have led to an improved understanding of the function of the vermiform appendix as a safe-house for beneficial bacteria in the colon. These advances have been made despite long standing clinical observations that the appendectomy is a safe and effective procedure. However, more recent clinical data show that an appendectomy puts patients at increased risk for recurrent Clostridium difficile (C. difficile)-associated colitis, and probably other diseases associated with an altered microbiome. At the same time, appendectomy does not apparently put patients at risk for an initial onset of C. difficile-associated colitis. These clinical observations point toward the idea that the vermiform appendix might not effectively protect the microbiome in the face of broad spectrum antibiotics, the use of which precedes the initial onset of C. difficile-associated colitis. Further, these observations point to the idea that historically important threats to the microbiome such as infectious gastrointestinal pathogens have been supplanted by other threats, particularly the use of broad spectrum antibiotics.

[Antibacterial therapy in surgery of patients with acute destructive appendicitis]

Character of microflora of exsudate of abdominals and mucosis microflora of vermicular appendix is studied for patients with the destructive forms of appendicitis with the purpose of development of variants of antibacterial therapy at surgical treatment of patients with acute appendicitis. The patients with the destructive forms of appendicitis, which were on treatment in a municipal clinical hospital N 4 Kyiv for period 2004-2010. An Inflammatory-destructive process in an appendix is conditioned by both aerobic (Escherichia coli - 46,6 %, Enterobacter - 4,2 %, Citrobacter - 4,2 %, Klebsiella - 3,3 %, Pseudomonas aeruginosa - 5,8 %, Staphylococcus - 4,2 %) and anaerobic microorganisms (Bacteroides - 100 %) and increase Candida - 17,5 %. Antibacterial therapy is effective at 46,7 % patients with acute appendicitis. At 49,6 % patients acute appendicitis develops on a background dysbiotic intestinal disturbances. Clinically the effective charts of empiric antibacterial monotherapy 6 days it is been: Moxifloxacini intravenously 400 mgs one time in twenty-four hours during, Ertapenemi for a 1 g one time in twenty-four hours intravenously and combined - Aztreonami for a 1 g twice in twenty-four hours and of Clindamycini for 600 mgs twice in twenty-four hours, intramuscular during; Cefepimumi for a 1 g twice in twenty-four hours and of Clindamycini for 600 mgs twice in twenty-four hours, intramuscular.

Splenic rupture in a patient with pelvic abscess and sepsis

A 49-year-old man underwent appendicectomy through a Lanz incision for necrotic appendicitis. He subsequently developed pelvic abscess in the postoperative period, which was drained under computed tomography (CT) guidance. The bacteriology of pus swabs taken during appendicectomy and abscess drainage revealed coliforms. Six days after appendicectomy, the patient had an acute collapse due to rupture of the spleen, which was treated by splenectomy. CT of the abdomen at the time of abscess drainage had confirmed a normal spleen. Histopathological examination of the spleen revealed nonspecific acute splenitis--red pulp congested and infiltrated with neutrophils complicated by rupture. We postulate the abdominal source of sepsis and associated inflammatory response as the cause for the splenic pathology and rupture.

Isolation of Aggregatibacter aphrophilus from a patient with acute appendicitis

OBJECTIVES

Acute appendicitis is a common surgical emergency. The etiology and pathophysiology of appendicitis have been well investigated. Aggregatibacter aphrophilus is a fastidious gram-negative coccobacilli. Detection of this organism in clinical samples and its differentiation from Haemophilus aphrophilus or from Aggregatibacter actinomycetemcomitans in routine microbiology settings could be difficult.

METHODS

In this rare case, we report the isolation of Aggregatibacter aphrophilus from the appendix of a 14-year-old boy presented with acute appendicitis. The genotypic method using 16S rRNA sequencing was used for identification of the organism at species level.

CONCLUSION

This case highlights the importance of detecting fastidious and rare microorganisms such as Aggregatibacter aphrophilus that could be associated with acute appendicitis.

Tuberculous appendix: a review of clinical presentations and outcomes

INTRODUCTION

Tuberculous appendix is surprisingly rare, even in countries where this infection is common. We report our experience with tuberculous appendix over a 15-year period.

METHODS

A search for cases of tuberculous appendix was conducted from January 1995 to December 2009 on the databases of the National Tuberculosis Centre and the Departments of Pathology and Surgery of Raja Isteri Pengiran Anak Saleha Hospital.

RESULTS

There were five cases of tuberculous appendix, giving a cumulative incidence of 0.08 percent of all appendectomies (n is 6,593), 0.2 percent of tuberculosis (TB) cases (n is 2,876) and 8.6 percent of abdominal TB (n is 58). Three patients were male and two were female, with a median age of 27 (range 25-48) years. Four patients presented with symptoms of acute appendicitis and one with an appendiceal mass following treatment for acute gastroenteritis. Only one patient had constitutional symptoms. Four patients had appendectomies (one laparoscopic and three open) within the same admission and one had interval appendectomy. Operative findings included perforated appendix (n is 1), appendiceal mass (n is 1) and acute appendicitis (n is 3). In all cases, the diagnoses were made only after review of the histology. None of the patients had pulmonary TB. Delay in initiating anti-TB treatment in one patient resulted in the development of an ileocutaneous fistula following appendectomy. This was resolved by excision, followed by anti-TB treatment.

CONCLUSION

Tuberculous appendix can present as acute appendicitis, and the diagnosis is often made after surgery. Any delay in treatment can lead to significant complications.

Isolated appendicular tuberculosis (TB) presented as peritonitis

Tuberculosis is very common entity in both developing and under developed countries. Each year 3 million people worldwide died of the disease. Among extra pulmonary TB, alimentary system accounts for about 3.0% cases. The Commonest presentation of alimentary tuberculosis is Ileo-caecal disease, but isolated appendicular involvement is very rarely seen. Although some cases have been reported from our neighboring countries, there is still no such report from Bangladesh. We are here for the first time reporting a case of isolated appendicular tuberculosis which presented to us with peritonitis.

Efficacy of antimicrobial coating suture coated polyglactin 910 with tricosan (Vicryl plus) compared with polyglactin 910 (Vicryl) in reduced surgical site infection of appendicitis, double blind randomized control trial, preliminary safety report

OBJECTIVE

To evaluate the efficacy and safety of new antibacterial suture (Vicryl Plus) compared with a traditional braided suture (Vicryl) in a clinical study. The primary goal was to study effectiveness on reduced surgical site infection in an appendectomy operation. The authors' secondary goal was to analyze the safety and physical properties of Vicryl plus.

MATERIAL AND METHOD

This was a prospective, randomized, controlled, double blind, comparative, single-center study. After appendectomy was done, the patients were randomized in two groups: Vicryl Plus and Vicryl to selected suture for suturing the abdominal sheath. The surgical site infection was evaluated for 30 days, 6 months, and 1 year. The surgeons and attending doctor were blind to the type of suture. This is the primary report of the first 100 patients.

RESULTS

There was no difference in demographic and preoperative clinical in both groups. Although there was no statistical difference in the surgical site infection of Vicryl and Vicryl Plus (8 and 10%, p = 0.05), one case of deep surgical site infection was detected in the Vicryl group. No complications and no difference in related suture materials were detected.

CONCLUSION

Coated polyglactin 910 with tricosan (Vicryl Plus) is safe and satisfactory in surgical practice. Surgical site infection of appendectomy seemed too to be comparable between coated polyglactin 910 with tricosan (Vicryl Plus) and traditional polyglactin 910 (Vicryl) group.

[A case of isolated tuberculosis of the appendix at the University Hospital Center in Brazzaville, Congo]

Since the outbreak of human immunodeficiency virus (HIV) infection, extrapulmonary tuberculosis has become increasingly frequent in developing countries. The purpose of this report is to describe a case of isolated tuberculosis of the appendix diagnosed following generalized peritonitis in a 53-year-old man. The appendix is the least frequent gastrointestinal location of isolated tuberculosis. Diagnosis was achieved by histopathological examination of the appendix immersed in formalin 10% after appendectomy. Paraffin-embedded histological sections stained with hematoxylin-eosin (HE) displayed caseofollicular lesions characteristic of infection by Koch bacillus. Outcome was favourable with a 9-month regimen of antituberculosis treatment according to the protocol of the World Health Organization (WHO).

Microbial induction of B and T cell areas in rabbit appendix

Gut-associated lymphoid tissue (GALT) development requires interaction with the intestinal microbiota. Because murine secondary lymphoid tissue development is driven by positive feedback interactions between B cells and stromal cells, we used in situ hybridization to determine whether intestinal commensals influence such interactions during rabbit appendix development. The features of positive feedback interactions we examined (CXCL13 mRNA expression, B cell accumulation and FDC differentiation) increased during early follicle development, but stalled in the absence of intestinal commensals. These features were reinitiated by commensals that stimulated follicle development and intrafollicular B cell proliferation. Our results suggest that rabbit appendix follicles develop in two phases: an initial phase of B cell recruitment to nascent follicles, possibly through positive feedback interactions, and a subsequent phase of intrafollicular B cell proliferation stimulated by intestinal commensals. In addition, we found that intestinal commensals stimulate appendix CCL21 mRNA expression and T cell area formation.

Comparative study of the intestinal mucus barrier in normal and inflamed colon

AIM

To study the role of mucus in the spatial separation of intestinal bacteria from mucosa.

PATIENTS AND METHODS

Mucus barrier characteristics were evaluated using histological material obtained by biopsy from purged colon, colon prepared with enema and material from untreated appendices fixed with non-aqueous Carnoy solution. Bacteria were evaluated using fluorescence in situ hybridization, with bacterial 16S RNA probes and related to the periodic acid Schiff alcian blue stain. Biopsies from controls (n = 20), patients with self-limiting colitis (SLC; n = 20), ulcerative colitis (n = 20) and 60 randomly selected appendices were investigated.

RESULTS

The mucosal surface beneath the mucus layer was free of bacteria in > or =80% of the normal appendices and biopsies from controls. The thickness of the mucus layer and its spread decreased with increasing severity of the inflammation; the epithelial surface showed bacterial adherence, epithelial tissue defects and deep mucosal infiltration with bacteria and leucocytes. Bacteria and leucocytes were found within mucus in all biopsy specimens from patients with ulcerative colitis, SLC, and acute appendicitis. The concentration of bacteria within mucus was inversely correlated to the numbers of leucocytes.

CONCLUSIONS

The large bowel mucus layer effectively prevents contact between the highly concentrated luminal bacteria and the epithelial cells in all parts of the normal colon. Colonic inflammation is always accompanied by breaks in the mucus barrier. Although the inflammatory response gradually reduces the number of bacteria in mucus and faeces, the inflammation itself is not capable of preventing bacterial migration, adherence to and invasion of the mucosa.

Primary Aortoappendicular Fistula Arising from an Infected, Chronic, Contained, Ruptured Abdominal Aortic Aneurysm

Gastrointestinal bleeding can be caused by a variety of pathologies. Primary aortoappendicular fistula is rare and, in our case, arose in addition to a chronic contained rupture sac of an abdominal aortic aneurysm. Clinical diagnosis is difficult. Aortic aneurysmorrhaphy along with extensive debridement and emphasis on antibiotic therapy is curative.

[Pneumatosis cystoides intestini caeci--a pseudotumor presented at autopsy]

A large focus of cystic intestinal pneumatosis appeared as an accidental finding in a 59-year-old man suffering from obstructive lung disease, with cor pulmonale as the cause of death. The gas pseudocysts were found in the submucosa, muscularis propria and in the subserosal space. The pseudocysts were lined by flattened cells of connective tissue origin with presence of occasional macrophages. We believe that the lesion started by focal damage of the mucosal membrane, which was followed by penetration of stool particles with microbes into the submucosa. E. coli and Morganella morgani are the probable producers of the gas bullets.