Histomorphology of experimental listeriosis

Isolation and Molecular Characterization of Corynebacterium pseudotuberculosis: Association with Proinflammatory Cytokines in Caseous Lymphadenitis Pyogranulomas

Corynebacterium pseudotuberculosis (C. pseudotuberculosis) is a causative agent of numerous chronic diseases, including caseous lymphadenitis (CLA) in sheep and goats, which has a zoonotic potential in humans in addition to a poor therapeutic response. In this study, out of 120 collected samples, only 12 (10%) were positive for C. pseudotuberculosis by PCR and by intraperitoneal injection of male Guinea pigs and then characterized for antimicrobial susceptibility and its genetic-relatedness by enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR), which showed 2-4 bands ranging from 100 to 3000 bp that can be clustered into four clusters (C1-C4). Despite the serotype biovar 1 only infecting sheep and goats, ERIC-PCR reveals intra-subtyping variation. Examination of affected LNs and organs revealed marked enlargement with either thick creamy green pus or multiple abscesses of variable sizes with a central caseated core surrounded by dense fibrous capsule. A histopathological examination revealed a central necrotic core surrounded by a peripheral mantle of mononuclear cells and a fibrous capsule. Positive immune expression of nuclear factor kappa B (NF-κB/p65) and interleukin-1β (IL-1β) and negative expression of tumor necrosis factor (TNF) in CLA is the first report to our knowledge. Conclusion: In CLA pyogranulomas, IL1β is a more crucial proinflammatory cytokine than TNF in the regulation of C. pseudotuberculosis infection, which is accompanied by marked NF-κB immunoexpression. Therefore, the NF-κB/p65 signaling pathway is involved in the activation of IL1β, and additional immunohistochemical studies are required to determine the various roles of NF-κB/p65 in the inflammatory response within CLA pyogranulomas to control this pathogen.

Pathogenicity, genotyping and antibacterial susceptibility of the Listeria spp. recovered from stray dogs

The present study aimed to determine the prevalence of Listeria spp. in stray dogs in the Kayseri province of Turkey. In addition, serotyping, genotyping and virulence gene analysis of the isolated Listeria spp. were performed and their pathogenicity and antibacterial susceptibility were investigated. The study included 80 rectal swaps taken from 80 stray dogs of different ages and gender that were sheltered in the Kayseri Municipal Dog Shelter. Listeria selective broth and Listeria selective agar were used for the isolation of Listeria spp. and the isolates were identified using a Microbact 12L (Oxoid, England) identification test kit. 16S rDNA sequencing and species-specific polymerase chain reaction (PCR) were performed for molecular identification of the isolates, multiplex PCR and a serological test were performed for serotyping, and PCR was used for virulence gene analysis. For determining the pathogenicity of L. monocytogenes and L. innocua isolates, a total of 100 mice (50 pregnant and 50 non-pregnant) were used. The mice were infected intraperitoneally; the inoculation dose was 1 × 10⁹ CFU/mL and 0.2 mL was used for each animal. Tissue samples obtained from infected mice were processed for the re-isolation of the Listeria spp. and then stained with hematoxylin eosin and Brown-Brenn Gram stain. The antibiotic susceptibilities of the isolates were determined by the disk diffusion method. Listeria spp. were isolated from 5 (6.25%) of the 80 fecal samples. While 1 of the isolates was identified as L. monocytogenes, 4 of them were identified as L. innocua. Serotyping by serological and molecular methods revealed the isolate of L. monocytogenes to be serotype 1/2a. According to the phylogenetic trees, L. innocua and L. monocytogenes strains were clustered in different groups. The L. monocytogenes isolate was positive for all virulence genes tested. All L. innocua isolates were positive for the plcB gene. While all L. innocua isolates were negative for the lin1068 gene, 3 L. innocua isolates were found to be positive for the lin0558 gene. In mice infected with L. monocytogenes, pathological findings were observed in the uterus, intestines, pancreas, and heart. In mice infected with L. innocua, pathological findings were observed in the stomach, intestines and spleen. L. monocytogenes- or L. innocua-related infections or other inflammatory reactions were not observed in the brains of infected animals. On histopathological examination with Gram stain, an abundance of Listeria spp. was observed in the lesions of the liver, spleen, uterus, and kidney. Moreover, while abortion was observed in all animals infected with L. monocytogenes, it was not observed in any of the animals infected with L. innocua. Antibiotic susceptibility testing revealed that all 5 isolates were sensitive to ampicillin, amoxicillin/clavulanic acid, erythromycin, gentamicin, penicillin G, and trimethoprim-sulfamethoxazole and were resistant to nalidixic acid, streptomycin, and cefuroxime sodium. Considering also the pathogenicity of the isolated microorganisms, it can be suggested that stray dogs as carriers of Listeria spp. are a significant risk to public health. As L. innocua isolates, which are considered apathogenic, led to the occurrence of lesions similar to those caused by L. monocytogenes, detailed studies on the pathogenesis of L. innocua infections caused by L. innocua isolates recovered from various sources are required.

A herd level analysis of a Corynebacterium pseudotuberculosis outbreak in a dairy cattle herd

Corynebacterium pseudotuberculosis infection in an Israeli dairy cattle herd is described. The disease was characterized by ulcerative granulomatous lesions, which occurred in an epidemic form. Thirty-two cows and two heifers were affected, the ratio of the number affected to number at risk being 17.5 : 1 and 9.5 : 1, respectively. The culling rate was 50% of the affected animals. Most of the affected animals were cows (91.2%), with one first-calving cow (2.9%) and two heifers (5.9%) also affected. The infection occurred during the summer to autumn months (August-December), and lasted 118 days. The incubation period is about 2 months. The disease appeared in two clinical forms - cutaneous and mastitic - or as a mixed form. C. pseudotuberculosis organisms that were isolated from the ulcerative granulomatous lesions and from milk samples failed to reduce nitrate. A decrease in milk production (4%) and an increase in the bulk-milk somatic cell count from a herd mean of 240 x 10(3) mL(-1) to 460 x 10(3) mL(-1) were noted during the morbidity period. The organism was isolated from milk samples of eight animals (25%). Clinical, epizootiological and microbiological aspects of the infection are described.

Listeria pathogenesis and molecular virulence determinants

The gram-positive bacterium Listeria monocytogenes is the causative agent of listeriosis, a highly fatal opportunistic foodborne infection. Pregnant women, neonates, the elderly, and debilitated or immunocompromised patients in general are predominantly affected, although the disease can also develop in normal individuals. Clinical manifestations of invasive listeriosis are usually severe and include abortion, sepsis, and meningoencephalitis. Listeriosis can also manifest as a febrile gastroenteritis syndrome. In addition to humans, L. monocytogenes affects many vertebrate species, including birds. Listeria ivanovii, a second pathogenic species of the genus, is specific for ruminants. Our current view of the pathophysiology of listeriosis derives largely from studies with the mouse infection model. Pathogenic listeriae enter the host primarily through the intestine. The liver is thought to be their first target organ after intestinal translocation. In the liver, listeriae actively multiply until the infection is controlled by a cell-mediated immune response. This initial, subclinical step of listeriosis is thought to be common due to the frequent presence of pathogenic L. monocytogenes in food. In normal individuals, the continual exposure to listerial antigens probably contributes to the maintenance of anti-Listeria memory T cells. However, in debilitated and immunocompromised patients, the unrestricted proliferation of listeriae in the liver may result in prolonged low-level bacteremia, leading to invasion of the preferred secondary target organs (the brain and the gravid uterus) and to overt clinical disease. L. monocytogenes and L. ivanovii are facultative intracellular parasites able to survive in macrophages and to invade a variety of normally nonphagocytic cells, such as epithelial cells, hepatocytes, and endothelial cells. In all these cell types, pathogenic listeriae go through an intracellular life cycle involving early escape from the phagocytic vacuole, rapid intracytoplasmic multiplication, bacterially induced actin-based motility, and direct spread to neighboring cells, in which they reinitiate the cycle. In this way, listeriae disseminate in host tissues sheltered from the humoral arm of the immune system. Over the last 15 years, a number of virulence factors involved in key steps of this intracellular life cycle have been identified. This review describes in detail the molecular determinants of Listeria virulence and their mechanism of action and summarizes the current knowledge on the pathophysiology of listeriosis and the cell biology and host cell responses to Listeria infection. This article provides an updated perspective of the development of our understanding of Listeria pathogenesis from the first molecular genetic analyses of virulence mechanisms reported in 1985 until the start of the genomic era of Listeria research.

Detection of Listeria monocytogenes by polymerase chain reaction in intestinal mucosal biopsies from patients with inflammatory bowel disease and controls

BACKGROUND AND AIMS

Components of the intestinal microflora are believed to play an important role in the pathogenesis of inflammatory bowel disease (IBD) in genetically susceptible hosts acting either as a non-specific antigenic stimulus or as a specific pathogen. Listeria monocytogenes has been suggested as an organism with the potential to cause IBD. The objective of the present study was to investigate the prevalence of L. monocytogenes DNA in intestinal biopsies from patients with IBD and from non-IBD controls by using nested polymerase chain reaction (PCR).

METHODS

The DNA was extracted from 274 colonoscopic biopsies, which were obtained from 23 patients with Crohn's disease (CD), 28 with ulcerative colitis (UC) and 39 non-IBD control patients. Nested PCR amplification was used to detect the presence of the L. monocytogenes listeriolysin O (hly) gene. The sequences of positive PCR products were determined and compared with databases.

RESULTS

The sensitivity of our nested PCR was 10 fg L. monocytogenes DNA. Overall, L. monocytogenes DNA was detected in 13.0% patients with CD, 17.9% patients with UC and 25.6% non-IBD control patients or in 29 of 274 (10.6%) endoscopic biopsies. Among them, L. monocytogenes DNA was detected in four of 67 (6%) biopsies from patients with CD, five of 94 (5.3%) biopsies from patients with UC and 20 of 113 biopsies (17.7%) from non-IBD control patients. Sequence analysis of positive PCR products demonstrated more than 95% similarity to the hly gene sequence of L. monocytogenes, confirming the authenticity of our PCR products.

CONCLUSION

Listeria monocytogenes DNA was detected in the intestine of both patients with IBD and in non-IBD control patients, probably reflecting the widespread presence of this organism in the environment. The low yield of positive biopsies in our IBD patients (5-6%) and the fact that the detection rate of L. monocytogenes DNA was similar in endoscopic biopsies from IBD patients and non-IBD controls does not support a direct role for L. monocytogenes in the pathogenesis of IBD, at least in New Zealand patients.

Cell wall-deficient forms (L-forms) of Listeria monocytogenes in experimentally infected rats

Experimental infections were induced with different bacterial forms of Listeria monocytogenes: parental (S-forms), protoplastic (L-forms) and combined inoculum of both forms by i.p. injection of rats. The parental bacterial forms (S-forms) were isolated up to 7 days after challenge from the peritoneal cavity and the liver, while the L-forms were isolated up to 60 days from the peritoneal cavity. Continuous adhesion of L-forms on the peritoneal macrophage surface was found by scanning-electron microscopy. Erythrocyte and leucocyte count as well as some clinical chemistry parameters were measured during infections. They showed different dynamics in the three experimental groups. Histomorphological changes in the liver (microabscesses and mononuclear cellular granulomas) of infected animals were observed. They were less intensive and appeared later in rats infected with L-forms. The experiments demonstrated that infections caused by parental bacterial forms and by combined inoculum took an acute course, while the infection caused by L-forms could be distinguished as a prolonged and persistent one.

Corynebacterium pseudotuberculosis infection in Israeli cattle: clinical and epidemiological studies

Morbidity due to Corynebacterium pseudotuberculosis infection occurred in 29 dairy herds in Israel during 1989 to 1995. The disease occurred sporadically in 17 of the herds with a morbidity of up to 5 per cent, and was epidemic in 12, with a morbidity of 5 to 35 per cent. Cutaneous abscesses were diagnosed in 609 animals. Young cattle appeared to be less susceptible to the disease than older cows. Beef cattle herds were not affected. The disease appeared in the cutaneous form in 92.5 per cent of cases, the cutaneous and mastitic form in 5.9 per cent and the cutaneous and visceral form in 1.6 per cent. The cutaneous form appeared as deep subcutaneous abscesses on various parts of the body, with granulating ulcers exuding pus and blood. In 10 of the herds, C pseudotuberculosis was isolated from 33 mastitic cows which also had cutaneous lesions. The visceral form of the disease was detected when severely affected animals were slaughtered. In 23 of the herds, the disease occurred during the spring and summer dry season, from March to October; the highest prevalence was in the semi-arid Negev region. In 25 herds, the infection lasted for up to five months. The skin lesions on individual cows healed on average in 23.4 days, after either local or parenteral treatment. No significant difference was observed between the effect of systemic antibiotic treatment and local antiseptic treatment. One hundred and two (16.7 per cent) severely affected animals were culled. There was a decrease in milk production and large increases in somatic cell counts in the 12 herds in which the disease was epidemic. None of the strains of isolated C pseudotuberculosis reduced nitrate.

Immunocytochemical evidence of Listeria, Escherichia coli, and Streptococcus antigens in Crohn's disease

BACKGROUND/AIMS

Infectious agents have long been suspected of playing a role in the initiation of Crohn's disease. The objective of this study was to search for likely microbial agents in diseased tissues using immunocytochemical techniques.

METHODS

Intestines and mesenteric lymph node specimens of 21 patients from two French families with a high frequency of Crohn's disease and from Connecticut were studied. The microbial agents searched for included Bacteroides vulgatus, Borrelia burgdorferi, Escherichia coli, Listeria monocytogenes, Streptococcus spp., bovine viral diarrhea virus, influenza A virus, measles virus, parainfluenza virus, and respiratory syncytial virus.

RESULTS

Seventy-five percent of the patients with Crohn's disease (12 of 16) were positively labeled with the antibody to Listeria. Macrophages and giant cells immunolabeled for this antigen were distributed underneath ulcers, along fissures, around abscesses, within the lamina propria, in granulomas, and in the germinal centers of mesenteric lymph nodes. In addition, 57% (12 of 21) of the cases contained the E. coli antigen, and 44% (7 of 16) contained the streptococcal antigen. The immunolabeling for the latter two agents also occurred within macrophages and giant cells, distributed in a pattern similar to that of Listeria antigen.

CONCLUSIONS

The results suggest that Listeria spp., E. coli, and streptococci, but not measles virus, play a role in the pathogenesis of Crohn's disease.

Morphologic evaluation of the pathogenesis of bacterial enteric infections

Current advances in the understanding of the pathogenicity of the agents of diarrheal infections, Vibrio cholerae, diarrheagenic E. coli, Shigella, Salmonella, and enteropathogenic Yersinia, have, to a great extent, become possible due to morphological studies of host-pathogen interactions in natural and experimental infections. Despite a multigenic nature and a diversity of pathogenic features in the bacterial species and even in serogroups of the same species, it is now possible to delineate four major patterns of interaction of enteric pathogens with their cellular targets, the enterocytes, and with the immune apparatus of the gut. These patterns, epicellular cytotonic, epicellular restructuring cytotonic, invasive intraepithelial cytotonic and cytotoxic, and invasive transcellular cytotonic and cytotoxic bacteremic, underlie early pathogenesis and clinical manifestations in the respective diarrheal diseases. In this review, the results of the morphological analyses of these patterns over the last 3 decades as well as some methodological problems encountered in the interpretation of morphological observations are discussed.

Experimental Yersinia enterocolitica infection in euthymic and T-cell-deficient athymic nude C57BL/6 mice: comparison of time course, histomorphology, and immune response

To elucidate the role of T lymphocytes in primary infection with Yersinia enterocolitica, we investigated the elimination rate of this pathogen, the histomorphology of tissue lesions, and the immune responses of athymic T-cell-deficient C57BL/6 nude mice and their euthymic littermates after parenteral infection with Y. enterocolitica of serotype O:8. While a low inoculum of 3 x 10(2) Y. enterocolitica cells (about 0.01 times the median lethal dose for normal C57BL/6 mice) was cleared by normal C57BL/6 mice within 7 to 10 days, athymic nude C57BL/6 mice developed progressive infections after this inoculum, leading to death on days 20 to 25 postinfection (p.i.). While normal C57BL/6 mice experienced short-term transient infections, nude mice exhibited a biphasic, progressive infectious process. Thus, in the early phase (days 1 to 7 p.i.), a rapid influx of CD11b/18-positive cells (Mac-1 antigen) and natural killer cells was evident in the spleens and livers of the nude mice. The late phase (from day 8 p.i. onward) was characterized by a rapid progression of the infection and a further influx of CD11b/18-positive cells into the liver accompanied by an increase in bacterial counts and development of tissue lesions particularly in the liver and spleen. In normal mice, granuloma-like lesions composed of CD11b/18-, CD4-, and CD8-positive cells could be observed. However, granulomata were not found in nude mice. Yersinia-specific immunoglobulin G antibodies appeared on day 15 p.i. in the sera of normal mice, while nude mice failed to develop significant antibody titers. Adoptive transfer of Yersinia-specific T cells into athymic nude mice mediated resistance to Y. enterocolitica infection and restored both the ability of granuloma formation and the production of specific antibodies. In summary, the data presented herein strongly suggest that T lymphocytes play an essential role in the defense of C57BL/6 mice against Y. enterocolitica.

Failure of FK 506 to suppress the T cell-mediated immunity of mice to Listeria monocytogenes

Listeria monocytogenes belongs to the group of intracellular bacteria, which means that they reside and multiply within host cells. The protective immunity against such an infection is mediated by cellular immune mechanisms. Whereas the CD8+ T cell population plays a major role therein, the CD4+ T cells are held to be of minor importance in this defence system. Consequently, one can understand that immune suppression with FK 506 which acts primarily on this latter T cell subset, does not interfere with protective immunity of mice infected with L. monocytogenes. We have demonstrated that the drug blocks neither curing of primary infection, nor formation of granulomas, nor induction of cell populations capable of mediating adoptive transfer of immunity, nor expression of pre-existing immunity.

Immunohistological characterization of the cellular immune response against Yersinia enterocolitica in mice: evidence for the involvement of T lymphocytes

Previous work from this laboratory has demonstrated that cloned T lymphocytes from spleens of Yersinia-infected mice can transfer immunity against Y. enterocolitica into naive animals. In this study, we investigated the cellular immune response to parenteral infection of Yersinia-resistant C57 BL/6 mice with the highly virulent Y. enterocolitica strain WA of serotype O:8 employing immunohistological methods. In the course of the infection the spleen and the liver were the organs most extensively affected. Histologically, three different patterns of inflammatory reactions could be observed: (i) small non-pyogenic granuloma-like lesions (in the liver only), (ii) microabscesses lacking a sharp outline, and (iii) larger abscesses disclosing a distinct cellular border (spleen and liver). Immunohistologically, Y. enterocolitica was detectable within abscesses but not in the small granuloma-like lesions present in the liver. CD11b/18 positive cells (= Mac-1-antigen expressed on macrophages, monocytes, granulocytes and NK-cells) could be shown in Yersinia-induced lesions. The number of these cells correlated with the extent of tissue alterations induced by Y. enterocolitica. More strikingly, we were able to demonstrate for the first time that both CD4 (helper) and CD8 (cytotoxic) T lymphocytes are present in Yersinia-induced lesions. In summary, we could demonstrate for the first time that granuloma-like lesions can be induced by Y. enterocolitica. Moreover, we supported our recent study suggesting that T lymphocytes are probably involved in the immune response against Y. enterocolitica in mice.

Histopathology of the early phase during experimental Corynebacterium pseudotuberculosis infection in lambs

Histological responses during experimental Corynebacterium pseudotuberculosis infection in lambs were investigated in parotid lymph nodes for ten days following inoculation. Lambs were infected by the subcutaneous route into the right eyelid with a virulent strain of C. pseudotuberculosis. Multiple microscopic acute abscesses, predominantly infiltrated with polymorphonuclear (PMN) leucocytes, were seen in the right parotid lymph node on the 1st day post-inoculation (PI). This massive PMN infiltration coincided with a peripheral blood granulocytosis. On day 3 PI, an influx of histiocytes was observed, while the microabscesses became confluent. From day 3 to day 10 PI, these lesions became enlarged and transformed into typical pyogranulomas with a central necrosis and a peripheral mantle of mononuclear cells composed of macrophages, epithelioid cells and lymphocytes; these histological changes were associated with a bacterial dissemination limited to the superficial lymph nodes. A lymphoid hyperplasia with prominent germinal centers was observed in the draining lymph nodes from day 3 PI. These results illustrate the dual role of granulomatous lesions in chronic bacterial infections: although they limit bacterial dissemination, the granulomas do not impair the persistence of infectious organisms in the host, leading to focal tissue damage.

Therapeutic activities of antibiotics in listeriosis

In vitro practically all common antibiotics except cephalosporins are active against nearly all natural isolates of Listeria monocytogenes; the therapeutic efficacy of antibiotic treatment is, however, rather limited, since up to 30% listeriosis patients will succumb to this infection. At least one reason for this low in vivo efficiency is the intracellular habitat of L. monocytogenes. In animal experiments ampicillin or amoxicillin, respectively, are still the most active drugs. In addition, rifampicin also has pronounced protective activity. Coumermycin, which unfortunately cannot be given to humans, is the most reliable drug in animals.