Kinetics of interferon-gamma production and its comparison with anti-listeriolysin O detection in experimental bovine listeriosis

Evaluation of Indirect and Avidin–Biotin Enzyme Linked Immunosorbent Assays for Detection of Anti-Listeriolysin O Antibodies in Bovine Milk Samples

Listeria monocytogenes is a foodborne pathogen that causes a wide spectrum of diseases in humans and animals. Enzyme linked immunosorbent assays (ELISA) [indirect and avidin-biotin (A-B)] for detecting L. monocytogenes antibodies in bovine milk samples (n = 2060) were standardized and evaluated by comparison with bacteriological examination. The tests were standardized by checker board titration. Highly purified listeriolysin O (LLO) was used as an antigen. Receiver operating characteristic (ROC) analysis was performed to decide the cut-off values. The ROC analysis revealed the sensitivities of indirect and A-B ELISA as 100% and specificities as 97.1 and 99.9% respectively. Listeria monocytogenes was isolated from 105 (5.1%) milk samples collected from 52 farms. Anti-LLO IgG antibodies were detected from 137 and 112 milk samples when tested by indirect and A-B ELISA respectively. Of the 52 farms screened, 28 (53.8%) yielded one or more isolates of L. monocytogenes and 33 (63.5%) of the farms had one or more animals simultaneously positive by one or both the assays for anti-LLO antibodies.

Listeria monocytogenesin Multiple Habitats and Host Populations: Review of Available Data for Mathematical Modeling

Listeria monocytogenes has the ability to survive and multiply in diverse habitats and to cause infection in a variety of animal species and humans. We evaluated the literature on survival and multiplication within and transmission among multiple host populations and habitats, including man, sewage, general environment (soil, water, and vegetation), silage (fermented plant material), animals (including wild and domestic animals), and food processing plants. The available knowledge on L. monocytogenes transmission dynamics was translated into the key process nodes of interrelated host- and habitat-specific mathematical models, providing a starting framework for future modeling work and the ultimate development of a system-wide model for evaluation of its transmission, and strategies to reduce human exposure. Because of the ability of L. monocytogenes to survive and multiply in many habitats and hosts, and the number of possible transmission routes, it is highly unlikely that it could be eradicated from any habitat or host, including man. However, L. monocytogenes load within and transmission among habitats and host populations could probably be reduced. Based on the published information, we hypothesize that three recent anthropogenic practices increase the load within and transmission among reviewed habitats and host populations: extended refrigerated storage of ready-to-eat foods allowing L. monocytogenes growth in foods that are contaminated during production or subsequent handling; feeding domestic ruminants with silage often contaminated with L. monocytogenes; and dispersal of contaminated products of sewage treatment to agricultural fields and waters. Future mathematical modeling work could test how much the reduction of L. monocytogenes load and transmission in hosts and habitats associated with these anthropogenic practices would reduce human exposure and consequently human listeriosis.

Isolation of pathogenic Listeria monocytogenes and detection of antibodies against phosphatidylinositol-specific phospholipase C in buffaloes

The isolation of pathogenic Listeria spp. in bacteriological samples, and anti-phosphatidylinositol-specific phospholipase C (anti-PIPLC) antibodies in sera of buffaloes were studied. Isolation of the pathogen was attempted from the samples by selective enrichment in University of Vermont Medium and plating onto Dominguez-Rodriguez isolation agar. Pathogenicity of the isolates was tested by Christie, Atkins, Munch Petersen test and mice incoulation test. Listeria spp. and L. monocytogenes were isolated from 8.8 and 2.4%, and 4.8 and 1.6% of 125 each meat and blood samples, respectively. Out of the 125 samples each of feacal, nasal and vaginal swabs from buffaloes 8 and 4%, 13.6 and 2.4%, and 6.4 and 2.4% were positive for Listeria spp. and L. monocytogenes, respectively. L. ivanovii was confirmed from 0.8% vaginal sample. A total of 125 serum samples were tested by phosphatidylinositol-specific phospholipase C (PIPLC) based indirect ELISA of which 4.0% turned out to be seropositive.

Use of listeriolysin O and internalin A in a seroepidemiological study of listeriosis in Swiss dairy cows

Recombinant listeriolysin O and internalin A were used as antigens in an enzyme-linked immunosorbent assay (ELISA) for the specific detection of anti-Listeria monocytogenes antibodies in cattle. The results showed sensitivities and specificities of 82 and 92%, respectively, for the listeriolysin O ELISA, and 100 and 90%, respectively, for the internalin A ELISA, respectively. The test may be useful for the confirmation of listeria-related abortions and mastitis but does not seem to be indicated for use in the diagnosis of listeria-related encephalitis in cattle. A representative sample of 1,652 serum samples from the healthy dairy cattle population in Switzerland was tested by both ELISAs. The results showed that 11% of the healthy dairy cows in Switzerland simultaneously presented antibodies toward listeriolysin O and internalin A, and 48% of the farms had one or several animals simultaneously positive by assays with both antigens. Multivariable analysis at the farm level confirmed that feeding of silage represents a significant risk factor for a positive listeria serology. Detailed analysis identified corn silage but not grass silage as the major factor in this association. Cattle breed and hygiene on the farm were also identified as significant factors associated with the serological status of farms. In conclusion, the results of the study show that internalin A is a promising new antigen for use in listeria serology and that specific anti-L. monocytogenes antibodies are found in a significant proportion of healthy dairy cows in Switzerland.

Listeric infections in humans and animals in the Indian subcontinent: a review

Listeriosis is an important bacterial zoonosis caused by the intracellular pathogen Listeria monocytogenes. The disease has been reported in animals from the Indian subcontinent, usually in the form of sporadic cases but occasionally as outbreaks. Cases of listeriosis arise mainly from the ingestion of contaminated food. Listeriosis has been reported to cause encephalitis, abortion, mastitis, repeat breeding and endometriosis in animals. Listeric infections occur in children and women with a poor obstetric history. The epidemiological aspects and pathogenesis of listeriosis in animals and humans are not yet fully understood. This review offers comprehensive information on experimental studies and field cases in animals and on cases of human listeriosis. There are also sections on isolation from foods, diagnosis and treatment in humans and animals.

The occurrence of pathogenic Listeria monocytogenes and antibodies against listeriolysin-O in buffaloes

The occurrence of Listeria monocytogenes in meat and milk samples, and antilisteriolysin O (ALLO) antibodies in sera of buffaloes were studied. Isolation of the pathogen was attempted from the samples by selective enrichment in University of Vermont Medium and plating onto Dominguez-Rodriguez isolation agar. The pathogenicity of the isolates was tested by Christie, Atkins, Munch Petersen test and mouse inoculation test. Of 167 meat samples 2.4 and 10.17% were positive for L. monocytogenes and Listeria sp., respectively. Of the 64 milk samples 6.25 and 26.13% were positive for L. monocytogenes and Listeria sp., respectively. A total of 284 serum samples were tested by listeriolysin O (LLO)-based indirect enzyme-linked immunosorbent assay of which 25.35% were found to be seropositive. The culture positivity for L. monocytogenes and detection of ALLO did not show any agreement (kappa = 0.035). The prevalence of pathogenic L. monocytogenes in milk and meat and the occurrence of anti-LLO antibodies is of concern from the public health point of view.

BOVIGAM: an in vitro cellular diagnostic test for bovine tuberculosis

BOVIGAM which is based on the detection of gamma interferon (IFN- gamma) is a rapid, laboratory assay of a cell mediated immune response that may be used for the detection of tuberculosis (TB) infection in animals. Whole blood is first incubated overnight with bovine PPD, avian PPD or negative control antigens, and IFN- gamma in the supernatant plasma is then measured by EIA. TB infection is indicated by a predominant IFN- gamma response to bovine PPD. Since 1988, BOVIGAM has been extensively trialed on more than 200 000 cattle in Australia, Brazil, Ireland, Northern Ireland, Italy, New Zealand, Romania, Spain and the USA. Sensitivity has varied between 81.8% and 100% for culture-confirmed bovine TB and specificity between 94% and 100%. The IFN- gamma assay detects M. bovis infection earlier than the skin test and in New Zealand is applied to detect skin-test negative cattle with TB, where after slaughter a significant number of IFN- gamma reactors have TB. BOVIGAM is also approved in New Zealand for serial testing skin test positive cattle when non-specificity is suspected. Cattle are tested 7-30 days after a positive caudal fold test. The boosting effect of the skin test on T-cell activity allows blood to be cultured with PPD up to 30 h after collection without effecting accuracy. The BOVIGAM results are not affected by poor nutritional condition and are only mildly and briefly affected by dexamethasone treatment and parturition. IFN- gamma responses of cattle vaccinated with BCG are dose-dependent and short-lived. The BOVIGAM kit is now used routinely in many countries for the detection of M. bovis infected cattle, buffalo and goats.

Interferon gamma and prostaglandin in BSE-infected cattle

Suspect field cases of BSE infection (displaying clinical signs) were examined for possible alterations of cytokine/autacoid plasma levels and were compared to control cases (not displaying clinical signs of BSE infection). Interferon gamma (IFN-gamma) plasma levels were demonstrated as being elevated in all suspected field cases of BSE infection (irrespective of BSE status; determined via postmortem histopathological examination). We demonstrated that plasma IFN-gamma levels were significantly (P<0.005) higher in suspect cases of BSE infection than in control cases. BSE-positive prostaglandin-E(2), (PGE(2)) plasma levels were demonstrated as being elevated 1.25-fold above BSE-negative cases and 2.22-fold above control cases. No significant (P>0.5) increase in PGE(2)plasma levels was recorded between BSE-positive and -negative. IFN-gamma and PGE(2)plasma levels were examined using commercially available ELISA assay. The results presented in this publication are the first demonstration of alteration in immune state in animals with BSE.