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

Molecular detection of bacterial zoonotic abortive agents from ruminants in Turkey

Abortions in cattle and sheep are one of the major causes of economic losses worldwide. Brucella spp. are the most common infectious agent associated with these abortions. However, abortions caused by bacteria such as Listeria spp., Leptospira spp., Campylobacter spp. and Mycoplasma spp. are usually overlooked due to their sporadic nature and their status as non-priority abortion agents. In our study, we investigated the bacteria associated with abortion cases in cattle and sheep using PCR. For this purpose, we collected vaginal swab samples (n: 110) of aborted cattle and sheep, as well as stomach content samples (n: 69) of aborted calves and lambs from various cities in Turkey. The samples were analysed by bacteria-specific PCR to detect Campylobacter fetus, Leptospira spp., Listeria spp., Mycoplasma spp., and Yersinia spp. PCR analyses revealed that the investigated bacterial agents were present in 18.85% and 19.3% of the cattle and sheep samples, respectively, with an overall percentage of 18.99%. While the overall positivity rate for C. fetus, Leptospira spp., and Mycoplasma spp. was 2.79%, 10.06%, and 4.47%, respectively, the positivity rate for co-infection with Leptospira spp. and C. fetus was 1.68%. All samples were found to be negative for Yersinia spp. and Listeria spp. The high C. fetus positivity rate detected in sheep and in the stomach contents was statistically significant (p < 0.05). However, the difference in positivity rates between the cities, hosts, co-infections and causative agents was statistically insignificant (p > 0.05). This study provides preliminary data on the significant involvement of C. fetus, Leptospira spp. and Mycoplasma spp. in cattle and sheep abortions in Turkey indicating that they should not be overlooked in diagnosis. In addition, further research is needed to investigate the zoonotic potential of these pathogens for public health in Turkey.

Ecology of Listeria monocytogenes and Listeria species in India: the occurrence, resistance to biocides, genomic landscape and biocontrol

Listeria monocytogenes, the causative agent of listeriosis, has been implicated in increasing foodborne outbreaks worldwide. The disease is manifested in various forms ranging from severe sepsis in immune-compromised individuals, febrile gastroenteritis, still birth, abortions and meningoencephalitis. In India, data from studies on the detection and molecular epidemiological analysis of L. monocytogenes are only recently emerging. The presence of Listeria in different ecological niches has been recorded from India, including foods, soil, vegetables, mangrove swamps, seafood, freshwater fishes, clinical cases, and also insects. The organism has also been isolated from women with spontaneous abortions, miscarriage or recurrent obstetric history, aborted foetuses, animal clinical cases and wildlife samples. A novel species of Listeria has also been characterized. Listeria monocytogenes strains isolated from clinical, environmental, and foods showed biofilm-forming abilities. Listeria monocytogenes serotype 4b isolates of ST328, a predominant and unique ST observed in India, was repeatedly isolated from different sources, times, and geographical locations. Here, we reviewed the occurrence of Listeria in different sources in India, its resistance to biocides, and provide epidemiological analysis on its genomic landscape.

The prevalence of Listeria species in different food items of animal and plant origin in Ethiopia: a systematic review and meta-analysis

Background

Listeriosis is one of the important emerging zoonotic disease affecting human health following the consumption of contaminated food of animal origin. It results in serious clinical complications in humans with a high case facility rate. Therefore, this systematic review and meta-analysis aimed to estimate the pooled prevalence of Listeria species in Ethiopia.

Methods

A systematic search was conducted on PubMed, Web of Science, EMBASE, Google Scholar and the Cochrane Library. All identified observational studies reporting the prevalence of Listeria species in different food items of animal and plant origin in Ethiopia were included. Three authors independently extracted data and analyzed them using STATA Version 13 statistical software. A random effects model was computed to estimate the pooled prevalence of Listeria species in Ethiopia.

Results

After reviewing 122 studies, five studies fulfilled the inclusion criteria were included in the meta-analysis. The findings from the five studies revealed that the pooled prevalence of Listeria species in different food items of animal and plant origin in Ethiopia was 27% (95% CI 25, 29). The highest prevalence of Listeria species was reported in beef meat followed by ice cream with prevalence rates of 62% (95% CI 50, 75) and 43% (95% CI 33, 53), respectively.

Conclusion

The presence of Listeria species in different food items of animal and plant origin in Ethiopia is an indicator of the presence of public health hazards to the consumer, particularly to the high-risk groups. Hence, awareness creation on food safety and implementation of regulations is strongly recommended.

Journey towards National Institute of One Health in India

Background & objectives

Issues such as emerging and re-emerging infectious diseases, antimicrobial resistance, food security, biosafety and biosecurity are associated with changes in land use, population growth, urbanization, global travel and trade and climate change. As a result, a trans-disciplinary approach among human, animal and environmental health disciplines gained support. The Indian Council of Medical Research (ICMR) and Indian Council of Agricultural Research (ICAR) decided to establish a National Institute of One Health at Nagpur, Maharashtra, India. In this context, two collaborative research projects, funded by the ICAR and ICMR were initiated to conduct the epidemiological surveillance of selected zoonotic diseases in Central India.

Methods

Disease surveillance and molecular detection employing standard techniques like enzyme linked immunosorbent assay (ELISA), immuno-fluroscent assay (IFA), standard tube agglutination test (STAT) , Rose Bengal plate test (RBPT) and polymerase chain reaction (PCR) were undertaken based on the disease to be screened.

Results

In animals, the seropositivities for listeriosis (7.66%) and brucellosis (11.69%) were recorded. The occurrence of tuberculosis (3.8%) and leptospirosis (6.33%) was detected by PCR. Through cross-sectional studies from suspected human population with associated risk factors for zoonotic diseases, the seropositivity of brucellosis (1.83-11%), listeriosis (1.01-10.18 %), leptospirosis (8.14-12.67%) and scrub typhus (1.78-20.34%) was recorded. The investigations on scrub typhus indicated bimodal pattern during the months of pre-monsoon and post-monsoon season with a peak in post-monsoon in human cases. Ornithonyssus bacoti mites were identified from the rodents as a vector harbouring Orientia tsutsugamushi. The bovine tuberculosis was detected in 1.43 per cent human cases employing molecular assay.

Interpretation & conclusions

The data indicated the occurrence of important zoonotic diseases adversely affecting the livestock health and human wellbeing. The scientific collaboration between veterinary and medical faculties has set an example for effective implementation of One Health (OH) programme for the establishment of National Institute of OH.

The first report on Listeria monocytogenes producing siderophores and responds positively to N-acyl homoserine lactone (AHL) molecules by enhanced biofilm formation

Listeria monocytogenes are Gram-positive well-known emerging food-borne pathogens causing listeriosis in humans. In the present study, we have isolated biofilm-forming Listeria sp. from utensils used by a local milk collection dairy society at Usgao Goa, which collects milk for Goa dairy. Through biochemical tests and 16S rRNA sequence analysis, the bacterium was confirmed to be L. monocytogenes and designated as strain BN3, having GenBank accession number MF095110. We report for the first time Gram-positive L. monocytogenes strain BN3 producing iron-chelating siderophores by chrome azurol S (CAS) agar test. Also, this is a first report which reveals that L. monocytogenes strain BN3 responds to N-hexanoyl-homoserine lactone molecule (C₆-HSL) by gradual increase in their biofilm-forming potential with a gradual increase in AHL (C₆-HSL) concentration (250, 500 nM-1 μM) as compared to control revealed by crystal violet assay (CV) in microtiter plate. These results were further confirmed by scanning electron microscopy (SEM). A significant decrease in biofilm formation was observed when L. monocytogenes strain BN3 was treated with 10 µg/ml (R)-2-(2-hydroxynaphthalen-1-yl)thiazolidine-4-carboxylic acid, but when 250 and 500 nM AHL molecules were added, biofilm formation in strain BN3 was found to be enhanced as compared to control even in the presence of antibacterial compound, (R)-2-(2-hydroxynaphthalen-1-yl)thiazolidine-4-carboxylic acid. These results revealed that AHL molecules nullify the effect of antimicrobial compound and promote biofilm formation in L. monocytogenes strain BN3.

Characteristics and distribution of Listeria spp., including Listeria species newly described since 2009

The genus Listeria is currently comprised of 17 species, including 9 Listeria species newly described since 2009. Genomic and phenotypic data clearly define a distinct group of six species (Listeria sensu strictu) that share common phenotypic characteristics (e.g., ability to grow at low temperature, flagellar motility); this group includes the pathogen Listeria monocytogenes. The other 11 species (Listeria sensu lato) represent three distinct monophyletic groups, which may warrant recognition as separate genera. These three proposed genera do not contain pathogens, are non-motile (except for Listeria grayi), are able to reduce nitrate (except for Listeria floridensis), and are negative for the Voges-Proskauer test (except for L. grayi). Unlike all other Listeria species, species in the proposed new genus Mesolisteria are not able to grow below 7 °C. While most new Listeria species have only been identified in a few countries, the availability of molecular tools for rapid characterization of putative Listeria isolates will likely lead to future identification of isolates representing these new species from different sources. Identification of Listeria sensu lato isolates has not only allowed for a better understanding of the evolution of Listeria and virulence characteristics in Listeria but also has practical implications as detection of Listeria species is often used by the food industry as a marker to detect conditions that allow for presence, growth, and persistence of L. monocytogenes. This review will provide a comprehensive critical summary of our current understanding of the characteristics and distribution of the new Listeria species with a focus on Listeria sensu lato.

Listeriosis in animals, its public health significance (food-borne zoonosis) and advances in diagnosis and control: a comprehensive review

Listeriosis is an infectious and fatal disease of animals, birds, fish, crustaceans and humans. It is an important food-borne zoonosis caused by Listeria monocytogenes, an intracellular pathogen with unique potential to spread from cell to cell, thereby crossing blood-brain, intestinal and placental barriers. The organism possesses a pile of virulence factors that help to infect the host and evade from host immune machinery. Though disease occurrence is sporadic throughout the world, it can result in severe damage during an outbreak. Listeriosis is characterized by septicaemia, encephalitis, meningitis, meningoencephalitis, abortion, stillbirth, perinatal infections and gastroenteritis with the incubation period varying with the form of infection. L. monocytogenes has been isolated worldwide from humans, animals, poultry, environmental sources like soil, river, decaying plants, and food sources like milk, meat and their products, seafood and vegetables. Since appropriate vaccines are not available and infection is mainly transmitted through foods in humans and animals, hygienic practices can prevent its spread. The present review describes etiology, epidemiology, transmission, clinical signs, post-mortem lesions, pathogenesis, public health significance, and advances in diagnosis, vaccines and treatment of this disease. Special attention has been given to novel as well as prospective emerging therapies that include bacteriophage and cytokine therapy, avian egg yolk antibodies and herbal therapy. Various vaccines, including advances in recombinant and DNA vaccines and their modes of eliciting immune response, are also discussed. Due focus has also been given regarding appropriate prevention and control strategies to be adapted for better management of this zoonotic disease.

Genotypic characterization of Listeria monocytogenes isolated from humans in India

Listeria monocytogenes is a foodborne pathogen associated with severe diseases in humans and animals. The genotypic analysis of 17 L. monocytogenes isolates recovered from humans in India during 2006-2009 using multiplex serotyping PCR allowing serovar predictions, conventional serology and by pulsed field gel electrophoresis (PFGE) is presented. The isolates were recovered from patients exhibiting various clinical conditions. A multiplex-PCR based serotyping assay revealed 88·24% (15/17) of the strains belonging to the serovar group 4b, 4d, 4e and 11·76% (2/17) to the serovar group 1/2b, 3b. Conventional serology indicated that 13 (76·47%) L. monocytogenes isolates to be of serotype 4b, 2 (11·76%) serotype 4d, and 2 (11·76%) serotype 1/2b. Ten ApaI and nine AscI pulsotypes were recognized among the 17 human isolates. PFGE analysis allowed discrimination among isolates of the same serotype and among isolates from the same sampling areas or those isolated from different areas. Thus, PFGE together with multiplex-PCR serotyping allows rapid discrimination of L. monocytogenes strains. In addition, the predominance of L. monocytogenes serotype 4b is of concern, as this serotype has been most frequently associated with human listeriosis outbreaks.

Epidemiology and risk management of listeriosis in India

Listeria monocytogenes is a foodborne pathogen that can cause serious invasive illness, mainly in certain well-defined high-risk groups, including elderly and immunocompromised patients, pregnant women, newborns and infants. In India, this pathogen has been isolated from humans, animals and foods. The incidence of Listeria is generally comparable to those reported elsewhere in the world. In humans, maternal/neonatal listeriosis is the most common clinical form reported. Among animal populations, spontaneous abortions, subclinical mastitis, meningoencephalitis and endometritis were the commonest forms reported. The disease largely remains undiagnosed and under reported. From reported analyses of a variety of foods for Listeria, milk and milk products, meat and meat products, seafood and vegetables have been reported to be contaminated in India. The legal framework for microbiological safety of foods against microbes including L. monocytogenes is summarised. The epidemiological studies would help in understanding of the sources of infection and persistence and their risk assessment, routes of transmission, clinical forms and allow for better management of the infection.

Risk factors for Brucella spp. infection in smallholder household herds

Risk factors for Brucella infection, the association and impact of Brucella seropositivity on abortions were investigated in cattle (n=1291) reared in smallholder household herds (n=203) from six geographical areas of Zimbabwe between September 2004 and 2005. Data on management, abortion and herd structure were collected. Sera were tested for Brucella antibodies using the Rose Bengal test and a competitive enzyme-linked immunosorbent assay. Data were analysed by generalized estimating equation and logistic regression models. Brucella antibodies were estimated at 5·5% and 22·9% for individual cattle and herds, respectively. Abortions were reported in 3·2% of cows and 22·0% herds. The age of cows and Brucella seropositivity predicted abortion. For herds, Brucella seropositivity, geographical area, purchase of cattle and large herd size were independently associated with increased odds of abortion. Exposure to Brucella had a significant impact on abortion. These results highlight the important risk factors for Brucella spp. infection in smallholder herds. Thus, brucellosis control programmes which take these factors into consideration will be beneficial.