Human Listeriosis

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that can cause severe invasive infections upon ingestion with contaminated food. Clinically, listerial disease, or listeriosis, most often presents as bacteremia, meningitis or meningoencephalitis, and pregnancy-associated infections manifesting as miscarriage or neonatal sepsis. Invasive listeriosis is life-threatening and a main cause of foodborne illness leading to hospital admissions in Western countries. Sources of contamination can be identified through international surveillance systems for foodborne bacteria and strains' genetic data sharing. Large-scale whole genome studies have increased our knowledge on the diversity and evolution of L. monocytogenes, while recent pathophysiological investigations have improved our mechanistic understanding of listeriosis. In this article, we present an overview of human listeriosis with particular focus on relevant features of the causative bacterium, epidemiology, risk groups, pathogenesis, clinical manifestations, and treatment and prevention.

Impact of the COVID-19 Pandemic on the Reported Incidence of Select Bacterial Enteric Diseases in Canada, 2020

The aim of this study was to describe the impact of the COVID-19 pandemic on reported cases and clusters of select enteric diseases in Canada, for the period of March 2020 to December 2020. Weekly counts of laboratory confirmed cases of Salmonella, Shigella, Shiga toxin-producing Escherichia coli (STEC), and Listeria monocytogenes were obtained from laboratory surveillance data. These data were supplemented with epidemiological information on the suspected source of illness, collected for cases identified within whole genome sequencing clusters. Incidence rate ratios were calculated for each pathogen. All data were compared with a prepandemic reference period. Decreases in the number of reported cases in 2020 compared with the previous 5-year period were noted for Salmonella, Shigella, Escherichia coli O157, and non-O157 STEC. Reported number of cases for L. monocytogenes in 2020 remained similar to those of the previous 5-year period. There was a considerable decline (59.9%) in the number of cases associated with international travel compared with a 10% decline in the number of domestic cases. Comparison of reported incidence rates of clustered versus sporadic cases for each pathogen showed little variation. This study represents the first formal assessment of the impact of COVID-19 on reported enteric diseases in Canada. Reported case counts across several pathogens saw notable declines in 2020 compared with prepandemic levels, with restrictions on international travel playing a key role. Additional research is needed to understand how limitations on social gatherings, lock downs, and other public health measures have impacted enteric diseases.

Isolation, discrimination, and molecular detection of Listeria species from slaughtered cattle in Namwala District, Zambia

BACKGROUND

The food industry is increasingly becoming more scrutinized, given the frequency and intensity with which zoonotic diseases are being reported. Pathogen tracking has become more applicable with regards food safety. It is in this regard that the present study was formulated to track Listeria species. in freshly slaughtered cattle carcasses by utilizing standard and molecular biological techniques.

METHODS

A cross-sectional study design was conducted from March to December 2020 with 200 samples being equally collected in the rainy and dry seasons. A total of 180 and 20 swabs were aseptically collected from carcasses and the environment respectively. Samples were first subjected to pre-enrichment in half-strength Fraser broth followed by enrichment in full strength Fraser broth and subsequent plating on Listeria agar. Listeria growth characteristics were identified up to species level based on their morphological and biochemical characteristics. Further, molecular detection and phylogenetic analysis was conducted. Quantitative proportionate survey data were analyzed using Stata Version 15 software to estimate crude prevalence taking into account complex design at abattoir level. Factors associated with contamination were characterized using logistic regression. Sequences were analyzed using, Genetyyx version 12 and phylogenetic Mega.

RESULTS

Of the 200 samples, 19 were positive for Listeria species identified as L.innocua 14/19 (73.7%) and L. monocytogenes 5/19 (26.3%). All isolates were from freshly slaughtered carcasses, and none from environment. Siginificant differences in contamination levels were observed based on season: rainy season yielded 14 (73.6%) whilst the dry season 5 (26.3%). The L. monocytogenes strains showed a high degree of homogeneity on phylogenetic analysis and clustered based on abattoir. Seasonality was identified as a major determinant influencing contamination based on the final logistic regression model.

CONCLUSION

This study found evidence of L. monocytogenes contamination on traditionally raised beef carcasses across various abattoirs surveyed. The failure to find Listeria contamination on the abattoir environment may to a greater extent intimate cattle carccases as primary sources of contamination. However, a more comprerehnsive study incorporating different geographical regions is needed to conclusively ascertain these present findings.

Maternal-neonatal listeriosis

Listeriosis is a rare and severe foodborne infection caused by Listeria monocytogenes. It manifests as septicemia, neurolisteriosis, and maternal-fetal infection. In pregnancy, it may cause maternal fever, premature delivery, fetal loss, neonatal systemic and central nervous system infections. Maternal listeriosis is mostly reported during the 2nd and 3rd trimester of pregnancy, as sporadic cases or in the context of outbreaks. Strains belonging to clonal complexes 1, 4 and 6, referred to as hypervirulent, are the most associated to maternal-neonatal infections. Here we review the clinical, pathophysiological, and microbiological features of maternal-neonatal listeriosis.

Outbreak of Listeriosis in South Africa Associated with Processed Meat

BACKGROUND

An outbreak of listeriosis was identified in South Africa in 2017. The source was unknown.

METHODS

We conducted epidemiologic, trace-back, and environmental investigations and used whole-genome sequencing to type Listeria monocytogenes isolates. A case was defined as laboratory-confirmed L. monocytogenes infection during the period from June 11, 2017, to April 7, 2018.

RESULTS

A total of 937 cases were identified, of which 465 (50%) were associated with pregnancy; 406 of the pregnancy-associated cases (87%) occurred in neonates. Of the 937 cases, 229 (24%) occurred in patients 15 to 49 years of age (excluding those who were pregnant). Among the patients in whom human immunodeficiency virus (HIV) status was known, 38% of those with pregnancy-associated cases (77 of 204) and 46% of the remaining patients (97 of 211) were infected with HIV. Among 728 patients with a known outcome, 193 (27%) died. Clinical isolates from 609 patients were sequenced, and 567 (93%) were identified as sequence type 6 (ST6). In a case-control analysis, patients with ST6 infections were more likely to have eaten polony (a ready-to-eat processed meat) than those with non-ST6 infections (odds ratio, 8.55; 95% confidence interval, 1.66 to 43.35). Polony and environmental samples also yielded ST6 isolates, which, together with the isolates from the patients, belonged to the same core-genome multilocus sequence typing cluster with no more than 4 allelic differences; these findings showed that polony produced at a single facility was the outbreak source. A recall of ready-to-eat processed meat products from this facility was associated with a rapid decline in the incidence of L. monocytogenes ST6 infections.

CONCLUSIONS

This investigation showed that in a middle-income country with a high prevalence of HIV infection, L. monocytogenes caused disproportionate illness among pregnant girls and women and HIV-infected persons. Whole-genome sequencing facilitated the detection of the outbreak and guided the trace-back investigations that led to the identification of the source.

Listeriosis in Spain based on hospitalisation records, 1997 to 2015: need for greater awareness

IntroductionListeriosis is a food-borne disease of public health importance that has recently been involved in prolonged outbreaks. Despite its relevance, listeriosis is under-reported in many European countries.AimWe aimed to describe listeriosis epidemiology in Spain from 1997-2015.MethodsWe performed a retrospective study using the Spanish hospitalisation database. We calculated the mean number of hospitalisations per year and region. Pregnancy and neonatal-related listeriosis rates were computed. Relation between death and the presence of underlying health conditions was explored.ResultsBetween 1997-2015, 5,696 listeriosis hospitalisations occurred, showing a constantly increasing trend. Higher hospitalisation rates were located in the north of the country compared to southern regions. The age group ≥ 65 years old was the most represented (50%). Pregnant women and newborns accounted for 7% and 4% of hospitalisations, respectively. An underlying immunocompromising condition was present in 56.4% of patients: cancer (22.8%), diabetes mellitus (16.6%) and chronic liver disease (13.1%). Death occurred in 17% of patients, more frequently among those ≥ 65 years old (67.5%), with sepsis (39.9%) or with meningoencephalitis (19.2%).ConclusionListeriosis is an emergent public health problem in Spain that calls for targeted action. Further prevention strategies are urgently needed, including food safety education and messaging for all at-risk groups.

Characteristics of Listeria Monocytogenes Strains Persisting in a Meat Processing Facility over a 4-Year Period

Listeria monocytogenes can persist in food production facilities, resulting in serious threats to consumers due to the high mortality associated with listeriosis, especially in the very young, old and pregnant. We subtyped 124 strains of L. monocytogenes isolated from a meat processing facility in Switzerland by serotyping, multi locus sequence typing (MLST) typing and whole genome sequencing. We then analyzed their ability to form biofilms and their resistance to the disinfectants benzalkonium chloride (BC) and peracetic acid (PAA). The genotyping results of the strains showed that several clonal populations of L. monocytogenes belonging to CC9, CC204 and CC121 had persisted in this meat processing facility for at least four years. All of the strains showed biofilm forming capacity comparable to a known high biofilm forming strain. Known efflux pumps for BC were present in CC204, CC9 (brcABC) and CC121 (qacH) strains, while strains from other CC showed very low minimal inhibitory concentrations (MICs) for BC. For PAA, minimal bactericidal concentrations of 1.2–1.6% for 20 min and minimal inhibitory concentrations between 0.1 and 0.2% were observed. These values were close to or above the recommended concentration for use (0.5–1%), suggesting that PAA might be ineffective at controlling L. monocytogenes in this and potentially other meat processing facilities.

Growth potential of Listeria monocytogenes in twelve different types of RTE salads: Impact of food matrix, storage temperature and storage time

Listeriosis is a food borne disease associated with high hospitalization and fatality rates; in 2014, EU member states reported 2194 cases with 98.9% hospitalization rates and 210 fatalities. Proper risk analysis and the development of effective food safety strategies critically depend on the knowledge of the growth characteristics of L. monocytogenes on the product in question. Ready-to-eat (RTE) salads present a challenge in this context due to the absence of a heat treatment step before consumption. This study provides challenge-test based data of the growth characteristics of L. monocytogenes on twelve RTE salads. The food matrix, storage time and storage temperature were factors with a significant impact on the growth of L. monocytogenes. While most tested salads permitted a significant increase of L. monocytogenes in at least one of the tested conditions, no growth was observed on celeriac, carrot and corn salad products. There was a considerable increase in growth at 8 °C compared to 5 °C. Our data indicate that the reduction of the storage temperature at retail level to 5 °C and product shelf life could help mitigate the risk of L. monocytogenes in RTE salads.

The Impact of Chitosan-Divergicin Film on Growth of Listeria monocytogenes in Cold-Smoked Salmon

The aim of this study was to evaluate the impact of chitosan film, with bacteriocin divergicin 35 incorporate, on growth of Listeria monocytogenes in Cold smoked salmon. The simples of Cold-smoked wild salmon were inoculated with L. monocytogenes and treated with chitosan (100 kDa, 94.7% de-acetylated) and divergicin M35 was stored for 3 weeks at 4-8°C. The compounds were applied to the fish flesh in the form of solution or dried film. The film reduced L. monocytogenes to below the detection limit (<50 cfu/g) and kept total counts below 104 cfu per g compared to 109 cfu per g in control samples while the effectiveness of the solution was very limited. The inhibitory activity of the film lasted for 3 weeks, while the solution had no effect on L. monocytogenes counts measured on day 14. The film provided a better preservation of fish color (redness) and firmness than others treatments, while the solution had little impact on these parameters. It kept the volatile basic nitrogen (17.5 mg N/100 g) below the control value 29.9 mg N/100 g. Divergicin-loaded chitosan film thus may represent an interesting alternative for the bio-preservation of cold-smoked fish.

Challenging management of chorioamnionitis with placental listeriosis: lessons from 2 cases

Listeriosis is a rare foodborne infection caused by Listeria monocytogenes. It is 12–20 times more prevalent in pregnant women compared to the general population, with a 20–40% mortality rate in neonates. Early treatment with appropriate antimicrobial agents is critical for pregnancy outcomes; however, the infection is difficult to control because the nonspecific clinical manifestations and rarity of the disease often preclude early diagnosis. We encountered 2 cases of pregnancy-associated listeriosis that occurred at 29 and 37 weeks of gestation. Both neonates were delivered by emergent cesarean section due to fetal condition, and one of the preterm infants died immediately after birth. Pregnancy-associated listeriosis should be considered in the management of unexplained fever or inflammatory conditions in pregnant women.

Whole-Genome Sequences of Six Listeria monocytogenes Strains Isolated from Food

Here, we report the whole-genome sequences of six Listeria monocytogenes strains isolated from meat and milk products in Switzerland. All of these strains carry premature stop codons or amino acid deletions in inlA.

Comparative Phenotypic and Genotypic Analysis of Swiss and Finnish Listeria monocytogenes Isolates with Respect to Benzalkonium Chloride Resistance

Reduced susceptibility of Listeria monocytogenes to benzalkonium chloride (BC), a quaternary ammonium compound widely used in food processing and hospital environments, is a growing public health and food safety concern. The minimal inhibitory concentration of BC on 392 L. monocytogenes strains from Switzerland (CH) and Finland (FIN) was determined. Within this strain collection, benzalkonium chloride resistance was observed in 12.3% (24/195) of Swiss and 10.6% (21/197) of Finnish strains. In both countries, the highest prevalence of BC-resistant strains (CH: 29.4%; FIN: 38.9%) was detected among serotype 1/2c strains. Based on PCR analysis, genes coding for the qacH efflux pump system were detected for most of the BC-resistant strains (CH: 62.5%; FIN: 52.4%). Some Swiss BC-resistant strains harbored genes coding for the bcrABC (16.7%) efflux pump system, while one Finnish BC-resistant strain harbored the emrE gene previously only described among BC-resistant L. monocytogenes strains from Canada. Interestingly, a subset of BC-resistant strains (CH: 5/24, 20.8%; FIN: 9/21, 42.8%) lacked genes for efflux pumps currently known to confer BC resistance in L. monocytogenes. BC resistance analysis in presence of reserpine showed that the resistance was completely or partially efflux pump dependent in 10 out of the 14 strains lacking the known BC resistance genes. Sequence types 155 and ST403 were over-representated among these strains suggesting that these strains might share similar but yet unknown mechanisms of BC resistance.

Stochastic and Differential Activation of σB and PrfA in Listeria monocytogenes at the Single Cell Level under Different Environmental Stress Conditions

During host infection, the foodborne pathogen Listeria monocytogenes must sense and respond to rapidly changing environmental conditions. Two transcriptional regulators, the alternative sigma factor B (σ^B) and the Positive Regulatory Factor A (PrfA), are key contributors to the transcriptomic responses that enable bacterial survival in the host gastrointestinal tract and invasion of host duodenal cells. Increases in temperature and osmolarity induce activity of these proteins; such conditions may be encountered in food matrices as well as within the host gastrointestinal tract. Differences in PrfA and σ^B activity between individual cells might affect the fate of a cell during host invasion, therefore, we hypothesized that PrfA and σ^B activities differ among individual cells under heat and salt stress. We used fluorescent reporter fusions to determine the relative proportions of cells with active σ^B or PrfA following exposure to 45°C heat or 4% NaCl. Activities of both PrfA and σ^B were induced stochastically, with fluorescence levels ranging from below detection to high among individual cells. The proportion of cells with active PrfA was significantly higher than the proportion with active σ^B under all tested conditions; under some conditions, nearly all cells had active PrfA. Our findings further support the growing body of evidence illustrating the stochastic nature of bacterial gene expression under conditions that are relevant for host invasion via food-borne, oral infection.

Structural characterisation of the fatty acid biosynthesis enzyme FabF from the pathogen Listeria monocytogenes

Development of new antimicrobial agents is required against the causative agent for listeriosis, Listeria monocytogenes, as the number of drug resistant strains continues to increase. A promising target is the β-ketoacyl-acyl carrier protein synthase FabF, which participates in the catalysis of fatty acid synthesis and elongation, and is required for the production of phospholipid membranes, lipoproteins, and lipopolysaccharides. In this study, we report the 1.35 Å crystal structure of FabF from L. monocytogenes, providing an excellent platform for the rational design of novel inhibitors. By comparing the structure of L. monocytogenes FabF with other published bacterial FabF structures in complex with known inhibitors and substrates, we highlight conformational changes within the active site, which will need to be accounted for during drug design and virtual screening studies. This high-resolution structure of FabF represents an important step in the development of new classes of antimicrobial agents targeting FabF for the treatment of listeriosis.

Diversity of Listeria monocytogenes Strains of Clinical and Food Chain Origins in Belgium between 1985 and 2014

Listeriosis is a rare but severe disease, mainly caused by Listeria monocytogenes. This study shows the results of the laboratory-based surveillance of Listeriosis in Belgium over the period 1985-2014. Besides the incidence and some demographic data we present also more detailed microbiological and molecular characteristics of human strains isolated since 2000. The strains from the latter period were compared to food and animal strains from the same period. Our study shows that different food matrices were commonly contaminated with L. monocytogenes presenting the same PFGE profile as in patient's isolates. Since 1985, we observed a significant decrease in incidence of the Materno-Neonatal cases (from 0.15 to 0.04 cases /100,000 inhabitants-year), which is probably to be attributed to active prevention campaigns targeting pregnant women. Despite the strengthening of different control measures by the food industry, the incidence of non-Materno-Neonatal listeriosis increased in Belgium (from 0.3 to 0.7 cases /100,000 inhabitants-year), probably due to the rise of highly susceptible patients in an aging population. This significant increase found in non-Materno-Neonatal cases (slope coefficient 7.42%/year, P<0.0001) can be attributed to significant increase in incidence of isolates belonging to serovars 1/2a (n = 393, slope coefficient 6.62%/year, P<0.0001). Although resistance to antimicrobials is rare among L. monocytogenes isolates, a trend to increasing MIC values is evident with chloramphenicol, amoxicillin, tetracycline and ciprofloxacin. We show that fluoroquinolone resistance is not linked to chromosomal mutations, but caused by a variety of efflux pumps. Our study also shows that huge majority of known underlying pathologies (426 out of 785 cases) were cancers (185/426, 43.1%) and haematological malignancies (75/185, 40.5%). Moreover the risk population is susceptible to low levels of contamination in food stressing the need of prevention campaigns specifically targeting these persons.

Two-Component-System Histidine Kinases Involved in Growth of Listeria monocytogenes EGD-e at Low Temperatures

Two-component systems (TCSs) aid bacteria in adapting to a wide variety of stress conditions. While the role of TCS response regulators in the cold tolerance of the psychrotrophic foodborne pathogen Listeria monocytogenes has been demonstrated previously, no comprehensive studies showing the role of TCS histidine kinases of L. monocytogenes at low temperature have been performed. We compared the expression levels of each histidine kinase-encoding gene of L. monocytogenes EGD-e in logarithmic growth phase at 3°C and 37°C, as well as the expression levels 30 min, 3 h, and 7 h after cold shock at 5°C and preceding cold shock (at 37°C). We constructed a deletion mutation in each TCS histidine kinase gene, monitored the growth of the EGD-e wild-type and mutant strains at 3°C and 37°C, and measured the minimum growth temperature of each strain. Two genes, yycG and lisK, proved significant in regard to induced relative expression levels under cold conditions and cold-sensitive mutant phenotypes. Moreover, the ΔresE mutant showed a lower growth rate than that of wild-type EGD-e at 3°C. Eleven other genes showed upregulated gene expression but revealed no cold-sensitive phenotypes. The results show that the histidine kinases encoded by yycG and lisK are important for the growth and adaptation of L. monocytogenes EGD-e at low temperature.

Genetic and phenotypic characterization of Listeria monocytogenes from human clinical cases that occurred in Portugal between 2008 and 2012

Listeria monocytogenes infection (listeriosis) is an uncommon but severe foodborne illness that affects mainly individuals with recognized underlying conditions: the elderly, immunocompromised individuals, and pregnant women and their fetuses. The aim of this study was to obtain epidemiological data on cases of listeriosis occurring in Portugal from 2008 through 2012, collected in hospitals on a voluntary basis. L. monocytogenes isolates were characterized by genoserotyping by multiplex polymerase chain reaction, DNA macrorestriction pulsed-field gel electrophoresis (PFGE), and determination of minimal inhibitory concentration (MIC, μg/mL) for 12 antibiotics. During this period, 203 cases of listeriosis were detected. The annual incidence rate observed ranged from 0.2 to 0.7 cases per 100,000 inhabitants. Nineteen cases (9.5%) corresponded to maternal/neonatal (MN) infections. The mean age of the nonmaternal/neonatal (non-MN) cases with documented age was 59 years, and 46.4% occurred in patients aged over 65 years. The majority of listeriosis cases were caused by genoserogroup IVb isolates, and PFGE analysis revealed a high molecular diversity, suggesting that most were sporadic. Nevertheless, several clusters of isolates presenting different geographic and time distributions were detected. The incidence of antibiotic-resistant isolates of L. monocytogenes was low but significantly higher than in previous years (2003-2007). The implementation of a national surveillance system monitoring the incidence of listeriosis and antimicrobial resistance of strains would be most valuable, allowing identification of sporadic and outbreak cases, to detect general trends in antibiotic susceptibilities, and potentially identify food sources of clinical strains.

[Listeriosis and pregnancy]

Listeria monocytogenes is a ubiquitous Gram-positive bacillus widespread in nature. It is responsible for febrile abortion and encephalitis in cattle. It survives and multiplies at 4°C and does not alter the taste of food. Listeria monocytogenes is able to cross 3 host barriers: the intestinal, blood-brain and placental barriers. Maternal infection is rare but still severe in France, with 30 to 50 annual cases. Maternal infection is frequently asymptomatic, or manifests as isolated fever, whereas fetal and neonatal infection is severe and have a poor prognosis, with up to 25-35 % fetal/neonatal mortality. Amoxicillin is the reference antibiotic for listeriosis treatment and should be administered to every pregnant patient with unexplained fever, particularly in case of consumption of at risk food. Prevention in pregnant women relies on adherence to strict diet recommendations such as reheating of leftovers until steaming and avoidance of unpasteurized dairy products, cold delicatessen, meat spreads and pâtés. Listeriosis is a notifiable disease in France.

Listeria: an Australian perspective (2001-2010)

Despite having a low occurrence rate, Listeria monocytogenes is one of the most prominent foodborne pathogens in Australia. The organism is responsible for severe outbreaks with high case fatality and substantial economic losses due to food recalls. In this study, we analyze the incidence trends of listeriosis in Australia during 2001-2010, discuss the relevance of food recalls, and investigate the pathogen's role in foodborne outbreaks. A significant epidemiological finding was a consistently high national age-specific rate recorded for individuals aged 60 years and over. Analysis of Australian Listeria outbreak and food recall data suggests deficiencies in food safety programs of food manufacturing businesses implicated in Listeria outbreaks and revealed that ready-to-eat foods are high-risk vehicles for transmitting listeriosis. Highlighted is Australia's highly efficient Listeria management and surveillance systems bolstered by the introduction of Listeria molecular subtyping in 2010 coupled with a nationally standardized questionnaire by the "Australian foodborne disease surveillance network (OzFoodNet)." The detection of clusters and therefore outbreaks was now possible, allowing cases to be linked across multiple jurisdictions and enabling timely public health action. Considering current changes in food production and consumption patterns, continuous monitoring and improvement of surveillance systems will provide ongoing public health benefits and be crucial to future development of food safety policy for Australia.

Development and validation of qualitative SYBR®Green real-time PCR for detection and discrimination of Listeria spp. and Listeria monocytogenes

A combination of four qualitative SYBR®Green qPCR screening assays targeting two levels of discrimination: Listeria genus (except Listeria grayi) and Listeria monocytogenes, is presented. These assays have been developed to be run simultaneously using the same polymerase chain reaction (PCR) programme. The paper also proposes a new validation procedure to specifically validate qPCR assays applied to food microbiology according to two guidelines: the ISO 22118 norm and the "Definition of minimum performance requirements for analytical methods of GMO testing". The developed assays target the iap, prs and hlyA genes that belong to or neighbour the virulence cluster of Listeria spp. The selected primers were designed to amplify short fragments (60 to 103 bp) in order to obtain optimal PCR efficiency (between 97 and 107 % efficiency). The limit of detection of the SYBR®Green qPCR assays is two to five copies of target genes per qPCR reaction. These assays are highly accurate (98.08 and 100 % accuracy for the Listeria spp. and L. monocytogenes assays, respectively).

Enhanced surveillance of invasive listeriosis in the Lombardy region, Italy, in the years 2006-2010 reveals major clones and an increase in serotype 1/2a

BACKGROUND

Invasive listeriosis is a rare, life-threatening foodborne disease. Lombardy, an Italian region accounting for 16% of the total population, reported 55% of all listeriosis cases in the years 2006-2010. The aim of our study was to provide a snapshot of listeriosis epidemiology in this region after the implementation of a voluntary laboratory-based surveillance system.

METHODS

We characterized by serotyping, pulsed-field gel electrophoresis, multilocus sequence typing and detection of epidemic clone markers, 134 isolates from 132 listeriosis cases, including 15 pregnancy-related cases, occurring in the years 2006-2010 in Lombardy. Demographic and clinical characteristics of cases have also been described.

RESULTS

The mean age of non pregnancy-associated cases was 64.7 years, with 55.9% of cases being older than 65 years. Cases having no underlying medical conditions accounted for 11.6%. The all-cause fatality rate of 83 cases with a known survival outcome was 25.3%.Serotypes 1/2a and 4b comprised 52.2% and 38.8% of isolates, respectively. Seventy-three AscI pulsotypes and 25 sequence types assigned to 23 clonal complexes were recognized. Moreover, 53 (39.5%) isolates tested positive for the epidemic clone markers. Twelve molecular subtype clusters including at least three isolates were detected, with cluster 11 (1/2a/ST38) including 31 isolates identified during the entire study period. No outbreaks were notified to public health authorities during this period.

CONCLUSIONS

The findings of our study proved that epidemiology of listeriosis in Lombardy is characterized by a high prevalence of major clones and the increasing role of serotype 1/2a. Molecular subtyping is an essential tool in the epidemiology and surveillance of listeriosis. Rapid molecular cluster detection could alert about putative outbreaks, thus increasing the chance of detecting and inactivating routes of transmission.

Application of anti-listerial bacteriocins: monitoring enterocin expression by multiplex relative reverse transcription–PCR

Listeriosis is a deadly food-borne disease, and its incidence may be limited through the biotechnological exploitation of a number of anti-listerial biocontrol agents. The most widely used of these agents are bacteriocins and the Class II enterocins are characterized by their activity against Listeria. Enterocins are primarily produced by enterococci, particularly Enterococcus faecium and many strains have been described, often encoding multiple bacteriocins. The use of these strains in food will require that they are free of virulence functions and that they exhibit a high level expression of anti-listerial enterocins in fermentation conditions. Multiplex relative RT (reverse transcription)–PCR is a technique that is useful in the discovery of advantageous expression characteristics among enterocin-producing strains. It allows the levels of individual enterocin gene expression to be monitored and determination of how expression is altered under different growth conditions.

Listeriosis in pregnancy: case report and retrospective study

BACKGROUND

Listeria monocytogenes usually causes mild maternal illness, but can be devastating to the fetus.

CASE

Listeriosis in a pregnant patient successfully treated with empiric antibiotic therapy is described. After induced delivery, despite severe placental infection, a healthy infant was born. Additionally, archived placental specimens with similar pathological manifestation were evaluated for evidence of L. monocytogenes.

CONCLUSION

It is important to emphasize the value of associating maternal data and clinical and laboratory findings of the newborn with the pathologic placental findings to get better results in the etiologic diagnosis of the listeriosis.

Roles of four putative DEAD-box RNA helicase genes in growth of Listeria monocytogenes EGD-e under heat, pH, osmotic, ethanol, and oxidative stress conditions

To examine the role of the four putative DEAD-box RNA helicase genes of Listeria monocytogenes EGD-e in stress tolerance, the growth of the Δlmo0866, Δlmo1246, Δlmo1450, and Δlmo1722 deletion mutant strains at 42.5°C, at pH 5.6 or pH 9.4, in 6% NaCl, in 3.5% ethanol, and in 5 mM H(2)O(2) was studied. Restricted growth of the Δlmo0866 deletion mutant strain in 3.5% ethanol suggests that Lmo0866 contributes to ethanol stress tolerance of L. monocytogenes EGD-e. The Δlmo1450 mutant strain showed negligible growth at 42.5°C, at pH 9.4, and in 5 mM H(2)O(2) and a lower maximum growth temperature than the wild-type EGD-e, suggesting that Lmo1450 is involved in the tolerance of L. monocytogenes EGD-e to heat, alkali, and oxidative stresses. The altered stress tolerance of the Δlmo0866 and Δlmo1450 deletion mutant strains did not correlate with changes in relative expression levels of lmo0866 and lmo1450 genes under corresponding stresses, suggesting that Lmo0866- and Lmo1450-dependent tolerance to heat, alkali, ethanol, or oxidative stress is not regulated at the transcriptional level. Growth of the Δlmo1246 and Δlmo1722 deletion mutant strains did not differ from that of the wild-type EGD-e under any of the conditions tested, suggesting that Lmo1246 and Lmo1722 have no roles in the growth of L. monocytogenes EGD-e under heat, pH, osmotic, ethanol, or oxidative stress. This study shows that the putative DEAD-box RNA helicase genes lmo0866 and lmo1450 play important roles in tolerance of L. monocytogenes EGD-e to ethanol, heat, alkali, and oxidative stresses.

Prevalence and distribution of Listeria monocytogenes serotypes and pulsotypes in sows and fattening pigs in farrow-to-finish farms (France, 2008)

This study was undertaken to acquire new data on the prevalence of Listeria monocytogenes in sows and fattening pigs in farrow-to-finish pig farms, and to analyze distribution of serotypes and genotypes of the bacterium within farms. Detection of L. monocytogenes was carried out on 730 pooled feces samples from sows in 73 pig farms and on 172 pooled feces samples from fattening pigs in 43 of these farms. Isolates were serotyped and typed by pulsed-field gel electrophoresis. For sows, 46% of the farms and 11% of the samples were positive for L. monocytogenes. A total of 124 isolates were collected and distributed in four serotypes: 1/2a (41%), 1/2b (36%), 4b (21%), and 1/2c (2%). Positive farms harbored one to three serotypes. The genetic diversity was high; 51 genetic profiles were obtained with 25, 16, 9, and 1 for the serotypes 1/2a, 1/2b, 4b, and 1/2c, respectively. Positive farms harbored 1 to 6 genetic profiles. Isolates showing similar genotypes occurred in several farms. For fattening pigs, 25% of the farms and 14.5% of the samples were positive for L. monocytogenes. The 34 isolates belonged to four serotypes: 1/2a (32%), 1/2b (41%), 4b (24%), and 1/2c (3%). They were distributed in 20 genotypes: 6 for 1/2a; 8 for 1/2b, 5 for 4b, and 1 for 1/2c. Similar serotypes and pulsotypes were recovered in sows and fattening pigs from the same farms, suggesting common sources of contamination.

Genes encoding putative DEAD-box RNA helicases in Listeria monocytogenes EGD-e are needed for growth and motility at 3°C

Quantitative RT-PCR revealed that transcripts of all four putative DEAD-box RNA helicase genes of the psychrotrophic pathogen Listeria monocytogenes EGD-e are found at higher levels in organisms grown at 3°C than at 37°C. At 3°C, growth of the three corresponding gene deletion mutants Δlmo0866, Δlmo1450 and Δlmo1722 was clearly restricted. The minimum growth temperatures of the three mutants were also higher than that of the wild-type EGD-e. In addition to inability to grow at 3°C, growth of Δlmo0866 and Δlmo1722 was reduced at 25°C, suggesting special roles of Lmo0866 and Lmo1722 in growth at suboptimal temperatures. Growth of Δlmo1450 was restricted not only at 3°C and 25°C, but also at 37°C, suggesting that Lmo1450 plays a universal role in growth of L. monocytogenes EGD-e. Moreover, cold-sensitive Δlmo0866, Δlmo1450 and Δlmo1722 were impaired in motility. The Δlmo0866 and Δlmo1450 strains were non-motile, while Δlmo1722 showed reduced motility. This study shows that the putative DEAD-box RNA helicase genes lmo0866, lmo1450 and lmo1722 are necessary for cold tolerance and motility of L. monocytogenes EGD-e.

[Microbiological characterisation of Listeria monocytogenes isolates from human cases in Andalusia]

OBJECTIVE

The aim of this study was to perform a retrospective study by genotyping 154 isolates from human listeriosis cases occurred in the region of Andalusia (southern Spain) in the period 2005-2009.

MATERIAL AND METHODS

Serotyping was performed for 1 and 4 somatic antigens using commercial Listeria antisera, and by multiplex-PCR serogrouping according to the method described by Doumith et al. (2004). The antimicrobial susceptibility was performed by Epsilon test and interpreted by CLSI criteria. PFGE was performed according to the PulseNet protocol with the ApaI enzyme. The similarity of PFGE profiles was evaluated using the Bionumerics software. The multiplex PCR protocol described by Chen and Knabel (2007) was used for the identification of isolates belonging to L. monocytogenes ECI, ECII, and ECIII epidemic clones.

RESULTS

The 154 isolates were grouped into four serotypes: 4b [94 (61%)] strains, 1/2b [30 (19%)] strains, 1/2a [27 (18%)] strains, and 1/2c [3 (2%)] strains, with 100% of susceptibility to ampicillin and cotrimoxazole. A further sixty-two ApaI distinct pulsotypes were recognized. Thirty-seven isolates (24%) showed unique ApaI pulsotypes, and the remaining 117 strains (76%) were assigned to 25 ApaI clusters (60% in clusters of more than two isolates). The EC markers were found in 62 (40.3%) of the L. monocytogenes isolates tested. The ECI marker was present in 43 (46.2%) 4b serotype isolates, ECII in 10 (10.7%) 4b serotype isolates, and ECIII in 9 (33,3%) 1/2a serotype isolates.

DISCUSSION

A large proportion of the human listeriosis cases under investigation could be grouped into molecular subtype clusters, and our cases could be related to international food-borne outbreaks.

Antimicrobial treatment of invasive non-perinatal human listeriosis and the impact of the underlying disease on prognosis

Listeriosis is a resurgent foodborne disease in European countries. Benefits of combined β-lactam-aminoglycoside treatment remain controversial and the impact of the underlying disease on prognosis has not been fully assessed. We conducted a retrospective review of cases of sporadic listeriosis in adults from 1995 to 2008 at two university-affiliated hospitals serving a population of 600,000 people in Madrid, Spain. The primary end-point was the associated in-hospital mortality. Sixty-four patients were studied. Estimated incidence of listeriosis was 0.76/100.000 persons/year. Seventy-four per cent had chronic underlying diseases; cirrhosis of the liver and haematological and solid neoplasias were the most common comorbidities. Primary bacteraemia (58%) and meningitis (42%) were the most frequent manifestations. Focal infections were seen in ten cases. In-hospital mortality was 31%. Patients treated with ampicillin or with an ampicillin-gentamicin combination did not differ in age, severity of underlying disease or type of presentation. Differences in mortality were not seen between patients treated with monotherapy and those given combined treatment (28% vs 35%; p 0.634). Ten patients were treated with trimethoprim-sulfamethozaxole alone and only one died. All patients without comorbidities survived infection but mortality of patients with cirrhosis of the liver was 21% and that of patients with haematological or solid neoplasias was 66%. Only haematological neoplasia (OR 6.67; 95% CI 1.71-26.04; p 0.006) was significantly associated with an increased risk of mortality (R(2) (Cox-Snell) = 0.262). Mortality of listeriosis mainly depended on the severity of the underlying disease. Combined ampicillin-gentamicin therapy did not improved survival. Trimethoprim-sulfamethozaxole may be an effective alternative therapy for listerial infections.

Serving high-risk foods in a high-risk setting: survey of hospital food service practices after an outbreak of listeriosis in a hospital

BACKGROUND AND OBJECTIVES

Prepared ready-to-eat salads and ready-to-eat delicatessen-style meats present a high risk for Listeria contamination. Because no foodborne illness risk management guidelines exist specifically for US hospitals, a survey of New York City (NYC) hospitals was conducted to characterize policies and practices after a listeriosis outbreak occurred in a NYC hospital.

METHODS

From August through October 2008, a listeriosis outbreak in a NYC hospital was investigated. From February through April 2009, NYC's 61 acute-care hospitals were asked to participate in a telephone survey regarding food safety practices and policies, specifically service of high-risk foods to patients at increased risk for listeriosis.

RESULTS

Five patients with medical conditions that put them at high risk for listeriosis had laboratory-confirmed Listeria monocytogenes infection. The Listeria outbreak strain was isolated from tuna salad prepared in the hospital. Fifty-four (89%) of 61 hospitals responded to the survey. Overall, 81% of respondents reported serving ready-to-eat deli meats to patients, and 100% reported serving prepared ready-to-eat salads. Pregnant women, patients receiving immunosuppressive drugs, and patients undergoing chemotherapy were served ready-to-eat deli meats at 77%, 59%, and 49% of hospitals, respectively, and were served prepared ready-to-eat salads at 94%, 89%, and 73% of hospitals, respectively. Only 4 (25%) of 16 respondents reported having a policy that ready-to-eat deli meats must be heated until steaming hot before serving.

CONCLUSIONS

Despite the potential for severe outcomes of Listeria infection among hospitalized patients, the majority of NYC hospitals had no food preparation policies to minimize risk. Hospitals should implement policies to avoid serving high-risk foods to patients at risk for listeriosis.

Outbreak of listeriosis caused by infected beef meat from a meals-on-wheels delivery in Denmark 2009

An outbreak of listeriosis in Denmark occurred in May 2009. Multilocus variable number of tandem repeats analysis typing, later confirmed by pulsed-field gel electrophoresis typing, showed that isolates from eight patients had identical patterns and were distinguishable from Listeria monocytogenes isolates from other Danish patients. Seven out of eight patients had received a meal with beef from the same meals-on-wheels delivery catering company 3 weeks prior to onset of disease. Two patients died of their infection. Large-scale delivery of precooked meals to a vulnerable population represents a threat if proper measures against listeriosis are not taken.

Prolonged hospital and community-based listeriosis outbreak caused by ready-to-eat scalded sausages

Listeria monocytogenes is a foodborne bacterial pathogen. Immunocompromised patients are at higher risk of developing invasive listeriosis with high fatality rates. After notification of two patients with Listeria that had stayed in the same hospital (hospital A) before the onset of infection, we began an investigation to ascertain the extent of the outbreak, identify its source and prevent further infections. We conducted active case finding by contacting hospital A, reviewing medical records and retrospectively investigating listeriosis notifications from the German surveillance system (SurvNet). The kitchen (hospital A) and its meat supplier (company X) were inspected and environmental and food samples were taken for microbiological testing. All isolates of L. monocytogenes, together with patient and food-related isolates from Baden-Württemberg 2006 to 2008, were characterised by pulsed-field gel electrophoresis (PFGE). Altogether, 16 cases of listeriosis were identified. Serotype 4b with the indistinguishable PFGE patterns (AscI 17a/ApaI 10) was detected from nine patients, five environmental and three ready-to-eat scalded sausage samples from company X, and two food samples from hospital A. All 11 patient cases linked to hospital A were immunosuppressed and were regularly served food during their hospital stay. Ten of these patients received corticosteroids and proton pump inhibitors (PPIs). Five cases were fatal. Our investigations indicate that ready-to-eat scalded sausages from company X caused this outbreak of listeriosis. Hospital food suppliers should guarantee the absence of L. monocytogenes in ready-to-eat meat products, controlled through optimised quality assurance.

Neuropathogenesis of naturally occurring encephalitis caused by Listeria monocytogenes in ruminants

Listeriosis is a serious food-borne disease with increasing frequency in humans and ruminants. Despite the facts that in both hosts, listeriosis can occur as rhombencephalitis and ruminants are a reservoir of Listeria monocytogenes (LM) strains pathogenic for humans, little work has been done on the pathogenesis in ruminants. This study investigates the neuropathogenesis of listeric encephalitis in over 200 natural cases in cattle, sheep and goats by analyzing anatomical distribution, severity, bacterial load and temporal evolution of the lesions. Our results suggest that LM gains access to the brainstem of all three species via axonal migration not only along the trigeminal nerve, but also along other nerves. The ensuing encephalitis does not remain restricted to the brainstem. Rather, LM spreads further from the brainstem into rostral brain regions likely by intracerebral axonal migration. Significant differences in severity of the lesions and bacterial load were found between cattle and small ruminants, which may be caused by species-specific properties of antibacterial immune responses. As histopathological lesions of human rhombencephalitis caused by LM strongly resemble those of ruminants, the disease likely has a similar pathogenesis in both hosts.