Cecal Pathology Research Articles

The Hha-TomB toxin-antitoxin module in Salmonella enterica serovar Typhimurium limits its intracellular survival profile and regulates host immune response.

The key to bacterial virulence relies on an exquisite balance of signals between microbe and hosts. Bacterial toxin-antitoxin (TA) system is known to play a vital role in response to stress adaptation, drug resistance, biofilm formation, intracellular survival, persistence as well as pathogenesis. In the present study, we investigated the role of Hha-TomB TA system in regulating virulence of Salmonella enterica serovar Typhimurium (S. Typhimurium) in a host model system, where we showed that deletion of hha and tomB genes displayed impaired cell adhesion, invasion, and uptake. The isogenic hha and tomB mutant strain was also found to be deficient in intracellular replication in vitro, with a highly repressed Salmonella Pathogenicity Island-2 (SPI-2) genes and downregulation of Salmonella Pathogenicity Island-1 (SPI-1) genes. In addition, the Δhha and ΔtomB did not show acute colitis in C57BL/6 mice and displayed less dissemination to systemic organs followed by their cecal pathology. The TA mutants also showed reduction in serum cytokine and nitric oxide levels both in vitro and in vivo. However, the inflammation phenotype was restored on complementing strain of TA gene to its mutant strain. In silico studies depicted firm interaction of Hha-TomB complex and the regulatory proteins, namely, SsrA, SsrB, PhoP, and PhoQ. Overall, we demonstrate that this study of Hha-TomB TA system is one of the prime regulating networks essential for S. Typhimurium pathogenesis. 1. Role of Hha-TomB toxin-antitoxin (TA) system in Salmonella pathogenesis was examined. 2. The TA mutants resulted in impaired invasion and intracellular replication in vitro. 3. The TA mutants displayed alteration in SPI-1 and SPI-2 regulatory genes inside host cells. 4. Mutation in TA genes also limited systemic colonization and inflammatory response in vivo.

S2364 Endoscopic Removal of an Inverted Appendix

INTRODUCTION: IA occurs when the appendix is turned inside out and contained within the lumen of the cecum. This could occur spontaneously or can be the result of a surgical intervention. It is an exceedingly infrequent finding on colonoscopy, appearing as a cecal intraluminal projection that could mimic a polyp or neoplasm. CASE DESCRIPTION/METHODS: A 51-year-old female with PMH of acute appendicitis and resultant appendectomy at 5 years of age underwent screening colonoscopy. Endoscopic report described a 10 mm polyp originating from the appendiceal orifice with pathology describing mild neutrophilic infiltration of the lamina propria with no evidence of granulomas or dysplasia. Endoscopic images revealed a smooth, non-adenomatous vermiform lesion, suspicious for an IA (Figure 1). Repeat colonoscopy confirmed the suspicion of a persistent, inverted, non-inflamed appendix, which measured 40 mm in length. A PolyLoop was applied to the base of the lesion, which was then removed using a hot snare (Figures 2 and 3). Subsequently, a Padlock OTSC was deployed below the level of the ligature to ensure a durable full-thickness closure. Pathology of the specimen confirmed that it was an IA with prominent submucosal edema and vascular congestion. Our patient underwent endoscopic removal of her inverted appendix, with no immediate or delayed post-procedural sequelae at a 12 month follow up. DISCUSSION: IA, an exceedingly rare finding, can be congenital, spontaneous, provoked or maybe the result of surgical intervention. Provoked IA can be benign or may occur due to underlying appendiceal pathologically. IA can be entirely asymptomatic or may present with abdominal pain, vomiting or blood per rectum. Expanses in endoscopic equipment and the emergence of a subspecialized group of Interventional Endoscopists has facilitated expertise in partial as well as full-thickness endoscopic resections. One of the proposed areas of continued expansion of endoscopic techniques is endoscopic appendectomy. Early feasibility case reports, as well as proof of concept and non-inferiority case series have been published with enthusiasm. This case highlights the importance of endoscopic identification of appendiceal pathology and serves to promote awareness for physicians to keep appendiceal inversion in the differential diagnosis of cecal projections; among more common cecal pathology such as polyps, lipomas, and neoplasm. Successful completion of this case is a testament to the potential for successful endoscopic appendectomy.Figure 1.: Endoscopic view of the inverted appendix.Figure 2.: Inverted appendix following application of PolyLoop.Figure 3.: Inverted appendix following hot scare resection.

An organized approach to imaging of benign cecal pathologies.

Unique problems in cecal embryogenesis and cecal pathology can result in characteristic imaging findings. Familiarity with these findings and utilization of an organized approach help to define the cecum’s role in acute abdominal symptoms. Clinical symptoms associated with cecal diseases can be diverse and misleading. This pictorial essay should provide a framework for an understanding of anatomical, infectious, and inflammatory cecal diseases. Knowledge of a broad spectrum of cecal pathologies contributing to these disorders and their corresponding imaging findings can help a radiologist define the diagnosis and guide proper management.

Mutagenicity of Helicobacter hepaticus infection in the lower bowel mucosa of 129/SvEv Rag2-/- Il10-/- gpt delta mice is influenced by sex.

Inflammatory bowel disease and colonic tumors induced by Helicobacter hepaticus (Hh) infection in susceptible mouse strains are utilized to dissect the mechanisms underlying similar human diseases. In our study, infection with genotoxic cytolethal distending toxin-producing Hh in 129/SvEv Rag2-/- Il10-/- gpt delta (RagIl10gpt) mice of both sexes for 21 weeks induced significantly more severe cecal and colonic pathology compared to uninfected controls. The mutation frequencies in the infected RagIl10gpt males were 2.1-fold higher for the cecum and 1.7-fold higher for the colon than male RagIl10gpt controls. In addition, there was a 12.5-fold increase of G:C-to-T:A transversions in the colon of Hh-infected males compared to controls. In contrast, there was no statistical significance in mutation frequencies between infected female Rag2Il10gpt mice and controls. Moreover, Hh infection in RagIl10gpt males significantly up-regulated transcription of Tnfα and iNos, and decreased mRNA levels of cecal Atm compared to the infected females; there was no significant difference in mRNA levels of Il-22, Il-17A, Ifnγ and Atr between the infected males and females. Significantly higher levels of cecal and colonic iNos expression and γH2AX-positive epithelial cells (a biomarker for double-strand DNA breaks [DSB]) in Hh-infected Rag2Il10gpt males vs. Hh-infected females were noted. Finally, Hh infection and associated inflammation increased levels of intestinal mucosa-associated genotoxic colibactin-producing pks+ Escherichia coli. Elevated Tnfα and iNos responses and bacterial genotoxins, in concert with suppression of the DSB repair responses, may have promoted mutagenesis in the lower bowel mucosa of Hh-infected male RagIl10gpt mice.

Double-Balloon Endoscopy after Incomplete Colonoscopy and Its Comparison with Computed Tomography Colonography.

Background/AimsBecause of the national screening program for colorectal carcinoma in The Netherlands, the number of colonoscopies has increased. In case of incomplete colonoscopy, computed tomography colonography (CTC) and double-balloon colonoscopy (DBc) are alternative options. This study evaluated cecal intubation rate and pathology detection rate in the previously unexplored part of the colon, complication rate of DBc, and CTC results after incomplete colonoscopy.MethodsRetrospective observational study in a tertiary referral hospital regarding DBc and CTC reports from cases with incomplete colonoscopy.ResultsSixty-three DBcs were performed after incomplete colonoscopy. Cecal intubation rate was 95%. Detection rate was 58% (5% carcinoma and 3% high-grade dysplastic adenoma). CTC preceded 54% of DBcs and 62% of CTC findings were confirmed. In 16%, a biopsy was taken, and in 60%, an intervention (mostly polypectomy) was performed. One major complication (1.5%) occurred, i.e., arterial bleeding due to polypectomy necessitating right hemicolectomy. CTC (n=213) showed a possible lesion in 35%, and could be confirmed by follow-up endoscopy or surgery in 65%.ConclusionsDBc is effective and safe for completion of colon inspection in incomplete colonoscopy. In patients with a high likelihood of pathology, DBc is preferred over CTC.

Primary cecal pathologies presenting as acute abdomen and critical appraisal of their current management strategies in emergency settings with review of literature

Background:The importance of cecal pathologies lie in the fact that being the first part of the large intestine, any disease involving the cecum affects the overall functioning of the large bowel. Primary cecal pathologies presenting as acute abdomen have not been described in any previous study in terms of presentation, management, and outcome.Objectives:The objective of this study was to identify the reported causes of primary cecal pathologies presenting as acute abdomen and the various causes presenting in our setting, the to discuss morbidity and mortality associated with cecal pathologies, and to critically analyze the various management modalities employed in an emergency setting.Materials and Methods:This is a retrospective analysis of a prospectively collected data of all adult patients admitted to our unit in the last 10 years for acute abdomen, in whom cecal pathology was identified as the primary offending agent.Results:Our analysis of 43 patients revealed cecal perforation secondary to amebic colitis along with the simultaneous presence of liver abscess to be the most common primary cecal entity met in practice as acute abdomen. Other pathologies that were encountered included volvulus, diverticulitis, and idiopathic typhlitis. Primary acute cecal pathologies are associated with high mortality rates (≈42%). Delay in diagnosis seems to be the most important factor contributing to high mortality as these conditions are commonly misdiagnosed as appendicular pathology. Most of our patients were managed by conservative colonic resection with proximal diversion. This seems to be a more plausible option in current practice in an emergency setting (mortality rate ≈ 36%) as hemicolectomy is associated with proportionately higher mortality rates (67%).Conclusion:A high index of suspicion, timely and adequate pre-operative workup, optimal resuscitation, and surgical conservatism with proximal diversion might help in early accurate identification of these conditions and possibly improved outcome.

Helicobacter hepaticus cytolethal distending toxin promotes intestinal carcinogenesis in 129Rag2-deficient mice.

Multiple pathogenic Gram-negative bacteria produce the cytolethal distending toxin (CDT) with activity of DNase I; CDT can induce DNA double-strand breaks (DSBs), G2/M cell cycle arrest, and apoptosis in cultured mammalian cells. However, the link of CDT to in vivo tumorigenesis is not fully understood. In this study, 129/SvEv Rag2-/- mice were gavaged with wild-type Helicobacter hepatics 3B1(Hh) and its isogenic cdtB mutant HhcdtBm7, followed by infection for 10 and 20weeks (WPI). HhCDT deficiency did not affect cecal colonization levels of HhcdtBm7, but attenuated severity of cecal pathology in HhcdtBm7-infected mice. Of importance, preneoplasic dysplasia was progressed to cancer from 10 to 20WPI in the Hh-infected mice but not in the HhcdtBm7-infected mice. In addition, the loss of HhCDT significantly dampened transcriptional upregulation of cecal Tnfα and Il-6, but elevated Il-10 mRNA levels when compared to Hh at 10WPI. Furthermore, the presence of HhCDT increased numbers of lower bowel intestinal γH2AX-positive epithelial cells (a marker of DSBs) at both 10 and 20WPI and augmented phospho-Stat3 foci+ intestinal crypts (activation of Stat3) at 20WPI. Our findings suggest that CDT promoted Hh carcinogenesis by enhancing DSBs and activation of the Tnfα/Il-6-Stat3 signaling pathway.

NADPH oxidase-1 deficiency offers little protection in Salmonella typhimurium-induced typhlitis in mice.

AIMTo test whether Nox1 plays a role in typhlitis induced by Salmonella enterica serovar Typhimurium (S. Tm) in a mouse model.METHODSEight-week-old male wild-type (WT) and Nox1 knockout (KO) C57BL6/J (B6) mice were administered metronidazole water for 4 d to make them susceptible to S. Tm infection by the oral route. The mice were given plain water and administered with 4 different doses of S. Tm by oral gavage. The mice were followed for another 4 d. From the time of the metronidazole application, the mice were observed twice daily and weighed daily. The ileum, cecum and colon were removed for sampling at the fourth day post-inoculation. Portions of all three tissues were fixed for histology and placed in RNAlater for mRNA/cDNA preparation and quantitative real-time PCR. The contents of the cecum were recovered for estimation of S. Tm CFU.RESULTSWe found Nox1-knockout (Nox1-KO) mice were not more sensitive to S. Tm colonization and infection than WT B6 mice. This conclusion is based on the following observations: (1) S. Tm-infection induced similar weight loss in Nox1-KO mice compared to WT mice; (2) the same S. Tm CFU was recovered from the cecal content of Nox1-KO and WT mice regardless of the inoculation dose, except the lowest inoculation dose (2 × 106 CFU) for which the Nox1-KO had one-log lower CFU than WT mice; (3) there is no difference in cecal pathology between WT and Nox1-KO groups; and (4) there are no S. Tm infection-induced changes in gene expression levels (IL-1b, TNF-α, and Duox2) between WT and Nox1-KO groups. The Alpi gene expression was more suppressed by S. Tm treatment in WT than the Nox1-KO cecum.CONCLUSIONNox1 does not protect mice from S. Tm colonization. Nox1-KO provides a very minor protective effect against S. Tm infection. Using NOX1-specific inhibitors for colitis therapy should not increase risks in bacterial infection.

Protective immunity against Eimeria tenella infection in chickens induced by immunization with a recombinant C-terminal derivative of EtIMP1

Immune mapped protein-1 (IMP1) is a new protective protein in apicomplexan parasites, and exits in Eimeria tenella. Cloning and sequence analysis has predicted the antigen to be a novel membrane protein of apicomplexan parasites. In order to assess the immunogenicity of EtIMP1, a C-terminal derivative of EtIMP1 was expressed in a bacterial host system and was used to immunize chickens. The protective efficacy against a homologous challenge was evaluated by body weight gains, lesion scores and fecal oocyst shedding. The results showed that the subunit vaccine can improve weight gains, reduced cecal pathology and lower oocyst fecal shedding compared with non immunized controls. The results suggested that the C-terminal derivative of EtIMP1 might be considered as a candidate in the development of subunit vaccines against Eimeria infection.

Host defense peptide resistance contributes to colonization and maximal intestinal pathology by Crohn's disease-associated adherent-invasive Escherichia coli.

Host defense peptides secreted by colonocytes and Paneth cells play a key role in innate host defenses in the gut. In Crohn's disease, the burden of tissue-associated Escherichia coli commonly increases at epithelial surfaces where host defense peptides concentrate, suggesting that this bacterial population might actively resist this mechanism of bacterial killing. Adherent-invasive E. coli (AIEC) is associated with Crohn's disease; however, the colonization determinants of AIEC in the inflamed gut are undefined. Here, we establish that host defense peptide resistance contributes to host colonization by Crohn's-associated AIEC. We identified a plasmid-encoded genomic island (called PI-6) in AIEC strain NRG857c that confers high-level resistance to α-helical cationic peptides and α- and β-defensins. Deletion of PI-6 sensitized strain NRG857c to these host defense molecules, reduced its competitive fitness in a mouse model of infection, and attenuated its ability to induce cecal pathology. This phenotype is due to two genes in PI-6, arlA, which encodes a Mig-14 family protein implicated in defensin resistance, and arlC, an OmpT family outer membrane protease. Implicit in these findings are new bacterial targets whose inhibition might limit AIEC burden and disease in the gut.

Display of Eimeria tenella EtMic2 protein on the surface of Saccharomyces cerevisiae as a potential oral vaccine against chicken coccidiosis

S. cerevisiae is generally regarded as safe and benign organism and its surface display system may be used as a unique eukaryotic expression system that is suitable for expressing eukaryotic antigen. In addition to the convenience of vaccine delivery, the yeast cell wall has been shown to enhance the innate immunity when immunized with the yeast live oral vaccine. In the present study, we expressed the chicken coccidian E. tenella EtMic2, a microneme protein, on the surface of the S. cerevisiae and evaluated it as a potential oral vaccine for chicken against E. tenella challenge. The protective efficacy against a homologous challenge was evaluated by body weight gains, lesion scores and fecal oocyst shedding. The results showed that the live oral vaccine can improve weight gains, reduced cecal pathology and lower oocyst fecal shedding compared with non immunized controls. In addition, the yeast oral vaccine could stimulate humoral as well as cell mediate immune responses. These results suggested that EtMic2 displayed on the cell surface of S. cerevisiae could be used as potential live vaccine against chicken coccidiosis.

MDCT of acute cecal conditions

The cecum comprises a relatively short segment of the gastrointestinal tract, but it can be affected by numerous acute conditions. Acute conditions may arise from processes primary to the cecum, such as volvulus, bascule, neoplasm, and trauma. Alternatively, acute conditions can be due to secondary to systemic or nearby pathology, such as infection, inflammatory processes, ischemia, and infarction. While it is common to suspect appendicitis as the etiology of acute right lower quadrant abdominal pain, the cecum should also be considered as a potential cause of pain, especially in the setting of an abnormal or absent appendix. Multi-detector computed tomography (MDCT) has evolved to become the best imaging modality to evaluate patients presenting with right lower quadrant abdominal pain or suspected acute cecal pathology. Strengths of MDCT include rapid acquisition of images, high spatial resolution, and ability to create multi-planar reconstructed images. In this pictorial review, we illustrate and describe key MDCT findings for various acute cecal conditions with which the emergency radiologist should be familiar.

Early MyD88-Dependent Induction of Interleukin-17A Expression during Salmonella Colitis

The development of T helper 17 (T(H)17) cells is a well-established adaptive mechanism for the production of interleukin-17A (IL-17A), a cytokine involved in neutrophil recruitment. However, pathways contributing to mucosal expression of IL-17A during the initial phase of a bacterial infection have received less attention. Here we used the mouse colitis model of Salmonella enterica serotype Typhimurium infection to investigate the contribution of myeloid differentiation primary response protein 88 (MyD88) to inflammation and mucosal IL-17A expression. Expression of IL-23 in the cecal mucosa during S. Typhimurium colitis was dependent on the presence of MyD88. Furthermore, initial expression of IL-17A at 24 h after S. Typhimurium infection was dependent on MyD88 and the receptor for IL-1β. IL-23 and IL-1β synergized in inducing expression of IL-17A in splenic T cells in vitro. In the intestinal mucosa, IL-17A was produced by three distinct T cell populations, including δγ T cells, T(H)17 cells, and CD4(-)CD8(-) T cells. The absence of IL-1β signaling or IL-17 signaling reduced CXC chemokine expression but did not alter the overall severity of pathological lesions in the cecal mucosa. In contrast, cecal pathology and neutrophil recruitment were markedly reduced in Myd88-deficient mice during the initial phases of S. Typhimurium infection. Collectively, these data demonstrate that MyD88-dependent mechanisms, including an initial expression of IL-17A, are important for orchestrating early inflammatory responses during S. Typhimurium colitis.

Water as contrast medium for computed tomography study of colonic wall lesions

A tap water enema combined with intravenous iodine contrast medium was used for computed tomographic (CT) study of the entire clean colon in 35 patients. Thirty of them showed a high suspicion of rectal, colon, or cecal pathology at either clinical examination, barium enema study, or endoscopy. The remaining five patients were examined for suspected local recurrence of carcinoma. This CT technique detected the wall abnormality in all but one case with two small adenomatous polyps. This procedure, which is simple, inexpensive, and has a good acceptance and tolerance, can accurately detect mural wall abnormalities.

The freckle sign—An endoscopic feature of the cecum

Mucosal spots, or "freckles," surrounding the appendiceal orifice are an endoscopic feature of the cecum. These are clusters of 1 to 2 mm round or oval slightly raised spots, each with a pale center and an erythematous border. They correlate microscopically with subepithelial and submucosal lymphoid follicles. The freckling pattern, identified in about one third of colonoscopies, was seen best with the videoendoscope and was identified more commonly in patients with systemic illness. Recognition of mucosal freckling around the appendiceal orifice helps identify the cecum and may be useful in the evaluation of cecal and appendiceal pathology.

Effect of Dietary Antibiotics on Chickens Infected with Eimeria tenella

Two experiments were performed to study the effect of dietary antibiotics on percent daily weight change, mortality and gross cecal pathology in chickens during the critical phase of Eimeria tenella infection. In the first experiment, chickens were continuously fed ration containing thiopeptin, 2 mg./kg.; bacitracin, 20 mg./kg.; penicillin, 12 mg./kg.; or chlortetracycline, 22 mg./kg. One day after antibiotic feed was given, each bird received an oral inoculation of 30,000 sporulated oocysts. In the second experiment, chickens were consecutively fed ration containing amprolium plus ethopabate, 125 plus 8 mg./kg., and a combination of the coccidiostat and one of 4 antibiotics; thiopeptin, bacitracin, penicillin, or chlortetracycline. One day after medicated feed was given, birds were each given an oral inoculation of 30,000 amprolium plus ethopabate-resistant E. tenella oocysts. The experiments were terminated 7 days after coccidia exposure. In both experiments, E. tenella infection resulted in depression in all birds of infected groups. Average percent weight change of infected birds was significantly lower than that of uninfected unmedicated control between 4 and 5 days after infection. Significantly greater number of birds died of cecal coccidiosis in group fed dietary bacitracin than that of other infected groups. Dietary antibiotics did not reduce gross cecal lesions.

Eimeria tenella in Gnotobiotic Chickens: Hematocrit, Weight Change, Cecal Pathology, and Mortality

On days 5 to 8 after oral inoculation with 200,000 Eimeria tenella oocysts, the mean hematocrits of bacteria-free, Bacillus cereus-monoflora and conventional chickens were equally reduced below control values. Weight loss was first observed in bacteria-free and monoflora fowl between days 4 and 5 after E. tenella inoculation, whereas conventional fowl initially displayed weight loss between days 3 and 4. Gross cecal lesion scores and total mortality of 4 experiments were not significantly different for the 2 gnotobiotic (bacteria-free and monoflora) groups, but these values for both groups were significantly less than those of infected conventional control animals. Since hematocrits were equally depressed in gnotobiotic and conventional animals, and survival was significantly greater in the former, it is suggested that factors in addition to blood loss cause mortality during E. tenella infections. The correlations between the severity of cecal lesions and per cent mortality suggests that these phenomena may be closely related. The present experiments with gnotobiotic fowl indicate that the normal flora is involved in the cecal pathology and mortality caused by cecal coccidiosis in conventional animals.

Eimeria tenella Infection in Testosterone-Injected Chicks

During the hemorrhagic stages of Eimeria tenella infection, the mean hematocrits of testosterone-injected male and female birds were significantly lower than those of uninfected testosteronetreated chicks but remained significantly greater than those of infected, oil-injected animals. In each of 3 experiments, testosterone-injected young male and female chicks showed significantly elevated mean hematocrits compared with oil-injected control fowl. Testosterone-treated chicks also showed somewhat reduced growth rates when compared to controls. By 9 days after E. tenella infection, the hematocrits of 19 oil-injected and 21 testosterone-injected chicks were not significantly different from those of uninfected, oil-injected controls. During the course of E. tenella infection in testosterone-injected and oil-injected chicks, there were no consistently significant differences in cecal lesion score, growth indexes, or mortality between these groups. The results of these experiments indicate that, although testosterone injection caused a significant increase in the hematocrit of young chicks, it offered no protection against the cecal pathology, weight loss, and mortality which occurred during cecal coccidiosis. Eimeria tenella (Railliet and Lucet, 1891) Fantham, 1909, infections in chickens are manifest by the characteristic symptoms of muscular weakness, loss of appetite, lowered body temperature, and bloody droppings. Cecal hemorrhage begins about 90 hr after infection and forms a major part of the cecal coccidiosis syndrome. Lowered hematocrit can first be detected 5 days after E. tenella infection and hematocrit determinations are a sensitive and convenient indicator of the severity of the disease (Natt and Herrick, 1955; Joyner and Davies, 1960). Both cecal coccidiosis and artificial bleeding of chickens by heart puncture produce similar packed red cell volume decreases (Natt and Herrick, 1955) and adrenal ascorbic acid depletions (Challey, 1960). Cecal hemorrhage has therefore been suggested as the most likely cause of mortality. However, Joyner and Davies (1960) found that, in light infections, significant hematocrit decrease occurs without mortality, and others have suggested that toxins produced by the coccidium may be the cause of death (Burns, 1959; Rikimaru, Galysh, and Shumard, 1961). Yet most mortality occurs during the period of acute hemorrhage, and dietary vitamin K significantly reduces this mortality (Joyner, 1963). If hemorrhage and its resultant adverse Received for publication 3 October 1972. * This study was supported by a Brown-Hazen Grant from Research Corporation and by the Foundation of the University of North Carolina at Charlotte. physiological effects (anemia, hemodilution, anoxia, hematopoietic stimulation) are the most important consequences of E. tenella infection, treatments to counteract these effects should be useful in protecting chickens from the cecal coccidiosis syndrome. Gorshein and Gardner (1970) suggest that steroid metabolites which have erythropoietic activity might prove clinically useful in treating anemia in man. Testosterone has been shown to stimulate erythropoiesis in the chicken, and packed red cell volume increased significantly 2 days after testosterone propionate injection (Glick, 1969). The present study was undertaken to determine if testosterone injections could protect chicks from the lethal consequences of E. tenella infections. The severity of the cecal coccidiosis syndrome was assessed by mortality, hematocrit, weight gain, and cecal lesion score. MATERIALS AND METHODS One-day-old White Rock chicks were obtained from a local hatchery (Holly Farms, Indian Trail, North Carolina). They were housed in electrically heated battery brooders, maintained on continuous artificial illumination, and fed an all-mash, unmedicated ration (CFR LAYER 17; Security Mills Inc., Knoxville, Tennessee). The sex of the chicks was determined at necropsy. The E. tenella oocysts were obtained from a pure strain maintained for many years in the laboratory of Dr. W. C. Burns, Department of Zoology, University of Wisconsin, and were kindly donated for this study. They were routinely harvested in this laboratory from donor birds 7 days after oral inoculation, sporulated, separated from host tissue and cecal debris by the method of Wagenbach, Challey, and Burns (1966), and

Eimeria tenella in Monoflora and Diflora Chicks

Eimeria tenella in Monoflora and Diflora Chicks

Eimeria tenella in Bacteria-Free and Conventionalized Chicks

Isolator-reared, uninfected, bacteria-free chicks appeared active and healthy and grew slightly faster than uninfected conventional controls in commercial brooders. Differences between the 2 groups were observed in cecal histology and color and consistency of the cecal contents. Fourteen- day-old and 40-day-old bacteria-free chicks were more resistant than conventional controls to cecal coccidiosis as assessed by the development of clinical signs and cecal pathology and the extent of weight loss and mortality. This indicates that the presence of the flora is involved in the manifestation of clini- cal coccidiosis. The same results were obtained with 2 different diets and a total of 139 of 229 conven- tionals died of coccidiosis whereas none of 89 bacteria-free chicks succumbed. Increasing the oocyst dose increased the severity of the clinical signs in bacteria-free chicks and demonstrated that the flora was not alone responsible for the manifestation of ceoal coccidiosis. Histological observations, oocyst production determinations, and oocyst viability tests showed that the presence of the intestinal flora was not essential for the development of E. tenella. Since fewer first- and second-generation schizonts were observed in bacteria-free fowl, it appears that the presence of the flora favorably affected the early stages of the parasite. Oocyst production, however, was similar in both bacteria-free and con- ventional chicks. Bacteria-free chicks infected with E. tenella produced serum lysins against second- generation merozoites and resisted challenge after conventionalization (placement of bacteria-free chicks into conventional animal housing facilities) as well as conventional controls. Experiments with con- ventionalized chicks indicate that mortality, cecal pathology, and clinical signs, but probably not oocyst production, were related to the presence of the flora during E. tenella infection. The earlier in infection the flora was established in bacteria-free fowl the more similar to the conventional syndrome the disease became.