Reduction in the incidence of human listeriosis in the United States. Effectiveness of prevention efforts? The Listeriosis Study Group

Clinical Findings of Listeria monocytogenes Infections with a Special Focus on Bone Localizations

Listeria monocytogenes is a Gram-positive pathogenic bacterium which can be found in soil or water. Infection with the microorganism can occur after ingestion of contaminated food products. Small and large outbreaks of listeriosis have been described in the past. L. monocytogenes can cause a number of different clinical syndromes, most frequently sepsis, meningitis, and rhombencephalitis, particularly in immunocompromised hosts. L. monocytogenes systemic infections can develop following tissue penetration across the gastrointestinal tract or to hematogenous spread to sterile sites, possibly evolving towards bacteremia. L. monocytogenes only rarely causes bone or joint infections, usually in the context of prosthetic material that can provide a site for bacterial seeding. We describe here the clinical findings of invasive listeriosis, mainly focusing on the diagnosis, clinical management, and treatment of bone and vertebral infections occurring in the context of invasive listeriosis.

Population dynamics of Listeria spp., Salmonella spp., and Escherichia coli on fresh produce: A scoping review

Collation of the current scope of literature related to population dynamics (i.e., growth, die-off, survival) of foodborne pathogens on fresh produce can aid in informing future research directions and help stakeholders identify relevant research literature. A scoping review was conducted to gather and synthesize literature that investigates population dynamics of pathogenic and non-pathogenic Listeria spp., Salmonella spp., and Escherichia coli on whole unprocessed fresh produce (defined as produce not having undergone chopping, cutting, homogenization, irradiation, or pasteurization). Literature sources were identified using an exhaustive search of research and industry reports published prior to September 23, 2021, followed by screening for relevance based on strict, a priori eligibility criteria. A total of 277 studies that met all eligibility criteria were subjected to an in-depth qualitative review of various factors (e.g., produce commodities, study settings, inoculation methodologies) that affect population dynamics. Included studies represent investigations of population dynamics on produce before (i.e., pre-harvest; n = 143) and after (i.e., post-harvest; n = 144) harvest. Several knowledge gaps were identified, including the limited representation of (i) pre-harvest studies that investigated population dynamics of Listeria spp. on produce (n = 13, 9% of pre-harvest studies), (ii) pre-harvest studies that were carried out on non-sprouts produce types grown using hydroponic cultivation practices (n = 7, 5% of pre-harvest studies), and (iii) post-harvest studies that reported the relative humidity conditions under which experiments were carried out (n = 56, 39% of post-harvest studies). These and other knowledge gaps summarized in this scoping review represent areas of research that can be investigated in future studies.

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.

Emergence and global spread of Listeria monocytogenes main clinical clonal complex

The bacterial foodborne pathogen Listeria monocytogenes clonal complex 1 (Lm-CC1) is the most prevalent clonal group associated with human listeriosis and is strongly associated with cattle and dairy products. Here, we analyze 2021 isolates collected from 40 countries, covering Lm-CC1 first isolation to present days, to define its evolutionary history and population dynamics. We show that Lm-CC1 spread worldwide from North America following the Industrial Revolution through two waves of expansion, coinciding with the transatlantic livestock trade in the second half of the 19th century and the rapid growth of cattle farming and food industrialization in the 20th century. In sharp contrast to its global spread over the past century, transmission chains are now mostly local, with limited inter- and intra-country spread. This study provides an unprecedented insight into L. monocytogenes phylogeography and population dynamics and highlights the importance of genome analyses for a better control of pathogen transmission.

An Update Review on Listeria Infection in Pregnancy

Listeria monocytogenes (LM) is an intracellular, aerobic and facultative anaerobic, Gram-positive bacterium, which is primarily transmitted to humans orally via food. LM could occur in asymptomatic pregnant women; however, fetal infection is a serious condition, entailing premature birth, abortion, sepsis, central nervous system (CNS) involvement, or even death. If a pregnant woman exhibits symptoms, the performance is almost like influenza, such as fever, headache, diarrhea, myalgia, or other digestive-related symptoms. This review collected clinical and empirical results regarding the mechanism, clinical manifestations, obstetrical outcome, diagnosis, treatment, vertical transmission, neonatal infection, and prevention of listeriosi according to articles published in PubMed from January 1, 1980, to March 20, 2021. The early detection and diagnosis of pregnancy-associated listeriosis are significant since sensitive antibiotics are effective at enhancing the prognosis of newborns. Listeriosis can be diagnosed using positive cultures from maternal or neonatal blood, neonatal cerebrospinal fluid (CSF), amniotic fluid, intrauterine mucosa, or the placenta. Two weeks of high-dose intravenous amoxicillin (more than 6 g/day) is recommended for LM pregnant women without allergy. Terminating the pregnancy to save the mother’s life should be considered if maternal and fetal conditions aggravate. Neonatal Listeria infection is primarily transmitted through the placenta, which is a critical illness associated with a high mortality rate. The necessary dietary guidance for pregnant women can reduce the incidence rate of pregnancy-related listeriosis.

Serotype Assignment by Sero-agglutination, ELISA, and PCR

For assessing isolates of Listeria monocytogenes, serotype designation is the first subtyping method used. Methodologies used to assign serotype are currently evolving and will eventually be replaced with whole genome sequencing. Traditionally, serotyping has been done with agglutination reactions; however, alternative methods utilizing enzyme linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) are common. Described here are the three non-genomic methods and the advantages and disadvantages of each.

A fluorescence immunoassay for a rapid detection of Listeria monocytogenes on working surfaces

Listeria monocytogenes is a foodborne pathogen responsible for human listeriosis. The increasing incidence of listeriosis induced governments and food manufacturing enterprises to act to diminish the problem. Several methods for the detection of Listeria monocytogenes in food industries were developed. However, they are time-consuming and require the use of specialized equipment. To reduce the detection time of Listeria monocytogenes in food, in this work we developed a fluorescence sandwich immunoassay based on the use of an innovative chitosan-cellulose nanocrystal (CNC) membrane that improves the antigen capture during bacterial growth. The combined use of CNC film for the capture of p60 protein-specific antigen together with the use of fluorescence detection reduced the time of analysis from 24 to 12 h with a limit of detection (LOD) of the assay of 10² CFU/mL (2 Log). In addition, the use of monoclonal anti-PepD covalently immobilized to a CNC membrane assured a high specificity of the assay. Interestingly, the obtained results show no cross-reactivity with the five most diffused pathogen bacteria strains tested.

Serotyping and antibiotic resistance of Listeria monocytogenes isolated from raw water buffalo milk and milk products

This study was aimed to investigate the presence of Listeria monocytogenes in raw water buffalo milk and milk products, besides determining its serotype and the extent of its resistance against various antibiotics. A total of 188 samples of raw water buffalo milk and milk products were collected from Samsun Province, Turkey between November 2012 and May 2013. The classical culture technique was used to isolate and identify L. monocytogenes, as described in EN ISO 11290-1. The isolates were confirmed as L. monocytogenes by using PCR with (hylA) primers specific for the hemolysin gene. The antimicrobial susceptibility test was achieved by using the VITEK 2 compact system and VITEK 2 AST-P640 card. L. monocytogenes was found in 7 (3.7%) of the 188 samples. Four of them were obtained from cheese and three from milk samples. Whereas, L. monocytogenes was not detected in any of the clotted cream samples. A total of 13 isolates were confirmed by PCR as L. monocytogenes. Among these isolates, one was 1/2c (or 3c) (7.6%), three were 4b (or 4d, 4e) (23%), four were 1/2b (or 3b) (30.7%), and the other five isolates were serotype 1/2a (or 3a) (38.4%). The highest antimicrobial resistance was recorded against fosfomycine (100%) followed by oxacillin (92%), penicillin (84%), and erythromycin (69%). However, no resistance was determined against ciprofloxacin, gentamicin, and tigecycline. PRACTICAL APPLICATION: This study showed that some samples of raw buffalo milk and the milk products were contaminated with Listeria monocytogenes. The serotype with the highest prevalence was determined as L. monocytogenes 1/2a. This study also demonstrated that most of the L. monocytogenes isolates had developed multiresistance to many frequently used medical antimicrobial agents.

Listeria monocytogenes in Export-approved Beef from Mato Grosso, Brazil: Prevalence, Molecular Characterization and Resistance to Antibiotics and Disinfectants

The Brazilian state of Mato Grosso is the largest producer and exporter of beef in the country, but few studies of relevance have been conducted to evaluate the microbiological safety of its products. This study aimed to estimate the prevalence of Listeria monocytogenes (LM) in export-approved beef from Mato Grosso and to characterize the isolates in terms of molecular properties and antimicrobial resistance. From a total of 50 samples analyzed, Listeria sp. was isolated in 18 (36% prevalence). Listeria monocytogenes was confirmed in 6 (12% prevalence). Among the serotype groups assessed by multiplex PCR, serotype 4 (4b, 4d or 4e) was the most prevalent. Although antibiotic resistance was not an issue, two strains isolated from different plants showed high resistance to sodium hypochlorite. Overall, this scenario causes concern because it puts at risk not only the Brazilian customer, but also the population of countries that import beef from Mato Grosso.

Sequelae of Fetal Infection in a Non-human Primate Model of Listeriosis

Listeria monocytogenes (Lm) is a common environmental bacterium that thrives on vegetation and soil matter, but can infect humans if contaminated food products are ingested, resulting in severe disease in immunosuppressed populations, including pregnant women and newborns. To better understand how the unique immunological milieu of pregnancy increases susceptibility to infection, we study listeriosis in cynomolgus macaques, a non-human primate that closely resembles humans in placentation and in the physiology, and immunology of pregnancy. Non-human primates are naturally susceptible to Lm infection, and spontaneous abortions due to listeriosis are known to occur in outdoor macaque colonies, making them ideal models to understand the disease pathogenesis and host-pathogen relationship of listeriosis. We have previously shown that Lm infection in the first trimester has a high rate of miscarriage. This study expands on our previous findings by assessing how the quantity of Lm as well as stage of pregnancy at the time of exposure may influence disease susceptibility. In the current study we inoculated a cohort of macaques with a lower dose of Lm than our previous study and although this did not result in fetal demise, there was evidence of in utero inflammation and fetal distress. Animals that were reinfected with an equivalent or higher dose of the same strain of Lm resulted in approximately half of cases continuing to term and half ending in fetal demise. These cases had inconsistent bacterial colonization of the fetal compartment, suggesting that Lm does not need to directly infect the placenta to cause adverse pregnancy outcomes. Timed surgical collection of tissues following inoculation demonstrated that transmission from mother to fetus can occur as soon as 5 days post-inoculation. Lastly, third trimester inoculation resulted in pregnancy loss in 3 out of 4 macaques, accompanied by characteristic pathology and Lm colonization. Collectively, our studies demonstrate that common laboratory culture tests may not always recover Lm despite known maternal ingestion. Notably, we also find it is possible for maternal infection to resolve in some cases with no discernible adverse outcome; however, such cases had evidence of a sterile intrauterine inflammatory response, with unknown consequences for fetal development.

Nutrition and listeriosis during pregnancy: a systematic review

Listeriosis is a rare but severe foodborne illness which is more common in populations such as pregnant women, and can result in serious complications including miscarriage, prematurity, maternal and neonatal sepsis, and death in the newborn. Population recommendations exist for specific foods and food preparation practices to reduce listeriosis risk during pregnancy. The aim of the present systematic review was to assess the association between listeriosis and these practices during pregnancy to confirm appropriateness of these recommendations. We searched MEDLINE, Embase, CINAHL Plus, Web of Science Core Collection, included articles' references, and contacted clinical experts. All databases were searched until July 2017. Case-control and cohort studies were included which assessed pregnant women or their newborn offspring with known listeriosis status and a nutritional exposure consistent with international population recommendations for minimising listeriosis. Outcomes included listeriosis with or without pregnancy outcomes. Risk of bias was assessed through the Newcastle-Ottawa Scale. Results were described narratively due to clinical heterogeneity in differences in nutritional exposures. Eleven articles comprising case-control or cross-sectional studies met the inclusion criteria. Cases of maternal, fetal or neonate listeriosis were more likely to have consumed high-risk dairy products, meat products or some fruits during pregnancy in comparison with women without listeriosis. Cases of listeriosis were more likely to have consumed foods that are highlighted in population guidelines to avoid to minimise listeriosis in comparison with those without listeriosis during pregnancy. Further research is warranted assessing means of improving the reach, uptake and generalisability of population guidelines for reducing listeriosis during pregnancy.

Increasing Incidence of Listeriosis and Infection-associated Clinical Outcomes

BACKGROUND

Listeriosis caused by Listeria monocytogenes has a high case-fatality rate (CFR) of approximately 20% to 30%. An increasing incidence of listeriosis has been reported in many countries recently. We investigated the annual incidence, clinical characteristics, and outcomes of listeriosis at three different hospitals in Korea and evaluated the effects of appropriate empiric antimicrobial treatments on patient outcomes.

METHODS

We retrospectively collected the data of all culture-positive cases of human listeriosis from three hospitals of different sizes in Korea during 2006-2016 and calculated the annual number of cases and incidence per 100,000 admissions.

RESULTS

A total of 58 patients with L. monocytogenes were included in this study. The incidence of listeriosis was significantly higher in 2013-2016 than in 2006-2012 (RR 3.1; 95% CI 1.79-5.36; P<0.001), mainly because of an increase in patients over 60 years of age (RR 3.69; 95% CI 1.70-8.02; P<0.001). Multivariate analysis showed that healthcare-associated infection (adjusted OR, 12.15; 95% CI, 2.56-86.01; P=0.004) and empirical treatment with first-line antimicrobial agents (adjusted OR, 0.08; 95% CI, 0.00-0.63; P=0.044) were associated with CFR.

CONCLUSIONS

Healthcare-associated infections caused by L. monocytogenes are associated with high CFR. Adequate initial empirical treatments could reduce CFR, suggesting that careful consideration of an empirical antimicrobial regimen is warranted for elderly or immunocompromised patients admitted to the hospital.

Molecular detection ofserotype groups of Listeria monocytogenes isolated from gallbladder of cattle and sheep in Iraq

Aim

This study was designed to investigate the occurrence of serotypes of Listeria monocytogenes, an important food-borne pathogen, in gallbladder samples from cattle and sheep.

Materials and Methods

Three hundred samples were collected and screened for the presence of L. monocytogenes. The identification of the isolates was confirmed by API-Listeria system and by the presence of hemolysin (hyl) gene. The isolates were subjected to polymerase chain reaction-based serotype identification with d1 (division 1), d2 (division 2), glt, mama (mismatch amplification mutation assay), and flaA (flagellin protein) genes.

Results

A total of 8 (2.7%) L. monocytogenes were recovered from 6 (4.0%) samples of sheep and 2 (1.3%) samples of cattle. All isolates showed positive results with Hly primers. Four isolates carried d1 gene, did not possess glt gene and harbored mama gene. The serotypes of these isolates were identified as 4a or 4c. The other 4 isolates carried d2 gene, 3 of them were positive with the FlaA primers, and hence, determined to be a 1/2a or 3a serotype, and 1 isolate was determined to be 1/2c or 3c serotype.

Conclusion

This study concluded that the presence of 1/2a serotype in gallbladder samples indicates public health risk through cross-contamination of meat at slaughterhouses.

Small molecules targeting LapB protein prevent Listeria attachment to catfish muscle

Listeria monocytogenes is a Gram-positive foodborne pathogen and the causative agent of listeriosis. L. monocytogenes lapB gene encodes a cell wall surface anchor protein, and mutation of this gene causes Listeria attenuation in mice. In this work, the potential role of Listeria LapB protein in catfish fillet attachment was investigated. To achieve this, boron-based small molecules designed to interfere with the active site of the L. monocytogenes LapB protein were developed, and their ability to prevent L. monocytogenes attachment to fish fillet was tested. Results indicated that seven out of nine different small molecules were effective in reducing the Listeria attachment to catfish fillets. Of these, three small molecules (SM3, SM5, and SM7) were highly effective in blocking Listeria attachment to catfish fillets. This study suggests an alternative strategy for reduction of L. monocytogenes contamination in fresh and frozen fish products.

Estimating the real incidence of invasive listeriosis through an integrated surveillance model in use in Lombardy (Italy, 2006–2014)

The annual incidence of listeriosis in Italy is lower (0·19–0·27 per 100 000 inhabitants per year) than in Europe (0·34–0·52 per 100 000 inhabitants per year). Since the observed incidence of listeriosis may be biased downward for underdiagnosis or under-reporting, this work aims to estimate the real incidence of listeriosis during a 9-year period in the Lombardy region, Italy. Data on listeriosis cases were collected from national mandatory notification system (MAINF) and Laboratory-based Surveillance System (LabSS). The two sources were cross-matched and capture–recapture method was applied to estimate the number of undetected cases and the real incidence of invasive listeriosis. Five hundred and eighty invasive listeriosis cases were detected by the two sources between 2006 and 2014: 50·2% were identified only via MAINF, 16·7% were recorded only via LabSS, overlaps occurred in 192 cases (33·1%). The mean annual incidence detected only by MAINF was 0·56 per 100 000 inhabitants, which rose to 0·67 per 100 000 considering also the cases detected by LabSS. The capture–recapture method allowed to estimate an incidence of 0·84 per 100 000. The high incidence of listeriosis may be due to improved sensitivity of the surveillance system, but also reflect a real increase, associated with an increased population at risk.

Of the Phrensy: an update on the epidemiology and pathogenesis of bacterial meningitis in the pediatric population

In the past century, advances in antibiotics and vaccination have dramatically altered the incidence and clinical outcomes of bacterial meningitis. We review the shifting epidemiology of meningitis in children, including after the implementation of vaccines that target common meningitic pathogens and the introduction of intrapartum antibiotic prophylaxis offered to mothers colonized with Streptococcus agalactiae. We also discuss what is currently known about the pathogenesis of meningitis. Recent studies of the human microbiome have illustrated dynamic relationships of bacterial and viral populations with the host, which may potentiate the risk of bacterial meningitis.

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.

Trends in US Hospital Stays for Listeriosis in Infants

BACKGROUND AND OBJECTIVES

Although listeriosis is rare in infants, it is common for young infants with suspected serious bacterial infection to be treated empirically with agents selected, in part, for their activity against Listeria monocytogenes. Our objectives were to describe the recent epidemiology of hospital discharges for listeriosis among infants in the United States and to precisely estimate the incidence of listeriosis according to infant age and meningitis status.

METHODS

We generated national estimates for listeriosis discharges in each of the 6 years for which samples were available in the Kids' Inpatient Database during the period 1997-2012. We used random-effects models to pool descriptive information and population rates across study years.

RESULTS

The cumulative number of US hospital discharges for listeriosis in infants was 344 (95% confidence interval [CI]: 290-397) over the 6 study years. The pooled annual incidence rate in infants (per 100,000 births) was 1.41 (95% CI: 1.01-1.80) after accounting for marked fluctuation in annual rates (range: 0.66-1.86; I2=79.3%). Discharges for listeriosis without meningitis were particularly rare after the first week of life. Our models predicted only 2.7 (95% CI: 1.1-4.2) and 1.8 (95% CI: 0.0-3.6) such discharges per year in infants admitted at ages 7 to 28 days and 29 to 364 days, respectively.

CONCLUSIONS

From the perspective of providing coverage against listeriosis, the routine practice of including ampicillin in the empirical treatment of febrile infants should be reevaluated for those older than 1 week without clinical evidence of meningitis.

Bacteremia in Early Infancy: Etiology and Management

We reviewed the literature regarding bacteremia in early infancy (age ≤ 90 days). Bacteremia remains a major cause of morbidity and mortality in young infants. However, recent epidemiologic data suggest that the incidence of bacteremia is decreasing and the pathogens responsible for invasive disease are changing. These changes will impact the evaluation and management of young infants. We review the current epidemiology of community-acquired bacteremia in early infancy with particular emphasis on the causative agents, diagnostic evaluation, and empiric and definitive antimicrobial treatment.

Rapid Identification and Classification of Listeria spp. and Serotype Assignment of Listeria monocytogenes Using Fourier Transform-Infrared Spectroscopy and Artificial Neural Network Analysis

The use of Fourier Transform-Infrared Spectroscopy (FT-IR) in conjunction with Artificial Neural Network software NeuroDeveloper™ was examined for the rapid identification and classification of Listeria species and serotyping of Listeria monocytogenes. A spectral library was created for 245 strains of Listeria spp. to give a biochemical fingerprint from which identification of unknown samples were made. This technology was able to accurately distinguish the Listeria species with 99.03% accuracy. Eleven serotypes of Listeria monocytogenes including 1/2a, 1/2b, and 4b were identified with 96.58% accuracy. In addition, motile and non-motile forms of Listeria were used to create a more robust model for identification. FT-IR coupled with NeuroDeveloper™ appear to be a more accurate and economic choice for rapid identification of pathogenic Listeria spp. than current methods.

Empiric Antibiotics for Serious Bacterial Infection in Young Infants: Opportunities for Stewardship

OBJECTIVES

To evaluate the causative agents of serious bacterial infection (SBI) in young infants and the optimal approach to empiric antibiotic therapy for infants with SBI.

METHODS

From May 1, 2011, to December 1, 2013, pertinent clinical data were collected on previously well infants 60 days or younger with SBI as defined by a positive bacterial culture from a sterile site. Infants were identified by prospective surveillance of admissions and daily review of microbiology records.

RESULTS

Two hundred sixty-five infants with SBI were identified. Mean age was 32 days (SD ±16.6 days). Twenty-nine infants had meningitis, 66 had bacteremia (37 with concomitant urinary tract infection), and 170 had urinary tract infection alone. No methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus sp., or penicillin-resistant Streptococcus pneumoniae were identified. Four extended-spectrum β-lactamase-producing gram-negative bacilli were seen. Empiric therapy was ampicillin and gentamicin (n = 116, 44%) or third-generation cephalosporin based (n = 149, 56%). Ampicillin and gentamicin, with third-generation cephalosporins reserved for cases where meningitis is suspected, would have provided effective coverage for 98.5% of infants and unnecessarily broad therapy for 4.3%. Third-generation cephalosporins with ampicillin would have been effective for 98.5% of infants and unnecessarily broad for 83.8%. Third-generation cephalosporin monotherapy was less effective than either combination (P < 0.001). Fifty-seven percent of broad spectrum empiric therapy was continued despite culture results allowing de-escalation.

CONCLUSIONS

Ampicillin/gentamicin remains an effective empiric regimen for infants 60 days or younger with suspected SBI. Use of a third-generation cephalosporin for suspected meningitis is appropriate, but cerebrospinal fluid must be obtained promptly to guide appropriate therapy.

Fournier's gangrene caused by Listeria monocytogenes as the primary organism

Fournier’s gangrene is a necrotizing infection of the scrotal region, and is typically caused by Exterobacteriaceae and anaerobic bacteria. This report describes a case involving a 70-year-old man of Japanese descent who developed Fournier’s gangrene that was found to be caused by Listeria monocytogenes. The patient’s unique risk factors are discussed.

A 70-year-old man with a history of tongue cancer presented with Fournier’s gangrene caused by Listeria monocytogenes serotype 4b. Surgical debridement revealed undiagnosed rectal adenocarcinoma. The patient did not have an apparent dietary or travel history but reported daily consumption of sashimi (raw fish).

Old age and immunodeficiency due to rectal adenocarcinoma may have supported the direct invasion of L monocytogenes from the tumour. The present article describes the first reported case of Fournier’s gangrene caused by L monocytogenes. The authors suggest that raw ready-to-eat seafood consumption be recognized as a risk factor for listeriosis, especially in cases of skin and soft tissue infection.

Pregnancy-related listeriosis in France, 1984 to 2011, with a focus on 606 cases from 1999 to 2011

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Acute oral safety study of sodium caseinate glycosylated via maillard reaction with galactose in rats

In order to potentially use sodium caseinate (SC) glycated with galactose (Gal) in the food industry as a new functional ingredient with proved technological and biological properties, an evaluation of oral acute toxicity has been carried out. An acute safety study with SC-Gal glycoconjugates in the Wistar rat with a single oral gavage dose of 2,000 mg/kg of body weight was conducted. The SC-Gal glycoconjugates were well tolerated; no adverse effects or mortality was observed during the 2-week observation period. No abnormal signs, behavioral changes, body weight changes, or alterations in food and water consumption occurred. After this period, no changes in hematological and serum chemistry parameters, organ weights, or gross pathology or histopathology were detected. It was concluded that SC-Gal glycoconjugates obtained via the Maillard reaction were well tolerated in rats at an acute oral dose of 2,000 mg/kg of body weight. The SC-Gal glycoconjugates have a low order of acute toxicity, and the oral 50 % lethal dose for male and female rats is in excess of 2,000 mg/kg of body weight.

Behavioral risk factors associated with listeriosis in the home: a review of consumer food safety studies

Listeria monocytogenes causes human listeriosis, which is associated with the highest hospitalization and mortality rates of all foodborne illnesses. In recent years, the incidence of listeriosis has doubled in Europe, almost exclusively among older adults (≥ 60 years of age). Food safety factors associated with increased risk of listeriosis include lack of adherence to "use by" dates and ineffective refrigerated storage of foods. Consequently, older adult consumers' implementation of safe food practices should be evaluated. This article is a review of consumer food safety cognitive and behavioral data relating to risk factors associated with listeriosis in the home as reported in 165 consumer food safety studies. Overall, only 41% of studies included assessment of consumer cognitive or behavioral data associated with listeriosis; of these studies 59% included data on safe refrigeration, 54% included data on storage time for opened ready-to-eat foods, and 49% included data on adherence to use-by dates. In most (83%) of the studies, survey-based data collection methods (questionnaires/interviews) were used; thus, the majority of findings were based on self-report (74%) and knowledge (44%). Observation (31%) and focus groups (12%) were less commonly used, resulting in a lack of actual behaviors and attitudinal data relating to listeriosis risk factors. Only 7% of studies included food safety data for older adults. Although older adults may fail to implement recommended practices, this review reveals a need for in-depth research to determine food safety attitudes and actual behaviors of older adults in conjunction with knowledge and selfreport of practices linked to increased risks of listeriosis. Such data combined with review findings would inform targeted food safety education to reduce risks associated with listeriosis in the home.

Serotype assignment by sero-agglutination, ELISA, and PCR

For assessing isolates of Listeria monocytogenes serotype designation is the foremost subtyping method used. Traditionally, serotyping has been done with agglutination reactions. In the last decade, alternative serotyping methods were described using enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). Herein are described the three methods, and the advantages and disadvantages of each.

Outbreak of Listeria monocytogenes in an urban poultry flock

Background

Listeria monocytogenes infection is most commonly recognized in ruminants, including cattle, sheep, and goats; but it is rarely diagnosed in poultry. This report describes an outbreak of L. monocytogenes in a backyard poultry flock. Also, it points out the importance of collaboration between veterinarians and public health departments and the possible implications of zoonotic diseases.

Case presentation

Depression, lack of appetite, labored breathing, and increased mortality were noted for 5 months in several affected birds within the flock. The pathologic changes in the internal organs of infected birds included severe myocarditis, pericarditis, pneumonia, hepatitis, and splenitis. No lesions were noted in the brain. Gram-positive organisms were seen in histologic sections of the heart and spleen. Listeria monocytogenes was detected by real time PCR from formalin fixed heart and spleen, and was isolated from fresh lung, spleen, and liver. This isolate was identified as L. monocytogenes serotype 4b by 16S rDNA sequencing and by PCR-based serotyping assay.

Conclusions

This is the first report describing outbreak of L. monocytogenes in backyard poultry flock in Washington State and use of molecular methods to confirm L. monocytogenes infection from formalin fixed tissues.

Pathogenesis of listeriosis during pregnancy

Listeria monocytogenes causes several clinical manifestations in humans and domestic animals. This bacterium is a saprophyte in soil and ensiled feeds, which are sources of infection for food producing animals (i.e. ruminants). The most common route of infection for people is via ingestion of contaminated ready-to-eat food products such as produce, soft cheeses and deli meats. In the United States, L. monocytogenes causes relatively few cases of clinical disease compared to other food-borne pathogens. However, clinical listeriosis is associated with high mortality, especially in immunocompromised patients, pregnant women, neonates, and the elderly. Listeria is an intracellular pathogen, which has been widely used in basic research to elucidate mechanisms of molecular pathogenesis and protective cell-mediated immunity. Despite the sizeable knowledge on L. monocytogenes pathogenesis, key points regarding listeriosis during pregnancy and the perinatal period remain unknown. This review summarizes listeriosis in humans and domestic animals during pregnancy, and animal models used to study the pathogenesis and immune response to L. monocytogenes infection during these periods.

Invasive listeriosis in the Foodborne Diseases Active Surveillance Network (FoodNet), 2004-2009: further targeted prevention needed for higher-risk groups

BACKGROUND

Listeriosis can cause severe disease, especially in fetuses, neonates, older adults, and persons with certain immunocompromising and chronic conditions. We summarize US population-based surveillance data for invasive listeriosis from 2004 through 2009.

METHODS

We analyzed Foodborne Diseases Active Surveillance Network (FoodNet) data for patients with Listeria monocytogenes isolated from normally sterile sites. We describe the epidemiology of listeriosis, estimate overall and specific incidence rates, and compare pregnancy-associated and nonpregnancy-associated listeriosis by age and ethnicity.

RESULTS

A total of 762 listeriosis cases were identified during the 6-year reporting period, including 126 pregnancy-associated cases (17%), 234 nonpregnancy-associated cases(31%) in patients aged <65 years, and 400 nonpregnancy-associated cases (53%) in patients aged ≥ 65 years. Eighteen percent of all cases were fatal. Meningitis was diagnosed in 44% of neonates. For 2004-2009, the overall annual incidence of listeriosis varied from 0.25 to 0.32 cases per 100,000 population. Among Hispanic women, the crude incidence of pregnancy-associated listeriosis increased from 5.09 to 12.37 cases per 100,000 for the periods of 2004-2006 and 2007-2009, respectively; among non-Hispanic women, pregnancy-associated listeriosis increased from 1.74 to 2.80 cases per 100,000 for the same periods. Incidence rates of nonpregnancy-associated listeriosis in patients aged ≥ 65 years were 4-5 times greater than overall rates annually.

CONCLUSIONS

Overall listeriosis incidence did not change significantly from 2004 through 2009. Further targeted prevention is needed, including food safety education and messaging (eg, avoiding Mexican-style cheese during pregnancy). Effective prevention among pregnant women, especially Hispanics, and older adults would substantially affect overall rates.

Targeting of the central nervous system by Listeria monocytogenes

Among bacteria that reach the central nervous system (CNS), Listeria monocytogenes (Lm) is one of deadliest, in human and ruminant. This facultative intracellular bacterium has the particularity to induce meningitis, meningoencephalitis and rhombencephalitis. Mechanisms by which Lm accesses the CNS remain poorly understood, but two major routes of infection have been proposed, based on clinical, in vitro and in vivo observations. A retrograde neural route is likely to occur in ruminants upon crossing of the oral epithelium, and this probably accounts for the observation that Lm induces almost exclusively rhombencephalitis in these animals. In contrast, the hematogenous route is likely the most frequent in human, in whom bacteria circulating in the blood, either free or associated with leukocytes are thought to breach the blood-brain barrier. New animal models that faithfully reproduce the hallmarks of human neurolisterisosis will allow addressing the molecular mechanisms underlying Lm ability to induce CNS disease, and improve our understanding of the pathophysiology of this deadly infection.

The occurrence and prevention of foodborne disease in vulnerable people

In developed countries, such as the United Kingdom and the United States, between 15% and 20% of the population show greater susceptibility than the general population to foodborne disease. This proportion includes people with primary immunodeficiency, patients treated with radiation or with immunosuppressive drugs for cancer and diseases of the immune system, those with acquired immune-deficiency syndrome and diabetics, people suffering from liver or kidney disease or with excessive iron in the blood, pregnant women, infants, and the elderly. Malnutrition and use of antacids, particularly proton-pump inhibitors, also increase susceptibility. We review the occurrence of infection by foodborne pathogens in these groups of people and measures to prevent infection. The nature and use of low microbial diets to reduce the risk of foodborne disease in immunocompromised patients are very variable. Diets for vulnerable people in care should exclude higher-risk foods, and vulnerable people in the community should receive clear advice about food safety, in particular avoidance of higher-risk foods and substitution of safer, nutritious foods.

Listeriosis in human pregnancy: a systematic review

Listeria is commonly found in processed and prepared foods and listeriosis is associated with high morbidity and mortality. Preventative measures are well prescribed and monitoring and voluntary recall of contaminated products has resulted in a 44% reduction in the prevalence of perinatal listeriosis in the USA. Pregnant women are at high risk for listeriosis, but symptoms are non-specific and diagnosis is difficult. The intracellular life-cycle of Listeria protects the bacterium from host innate and adaptive immune responses. Antibiotic treatment requires agents able to penetrate, distribute, and remain stable within host cells. Prolonged use of high-dose ampicillin can significantly improve neonatal outcome.

Prevalence of Salmonella enterica, Listeria monocytogenes, and Escherichia coli virulence factors in bulk tank milk and in-line filters from U.S. dairies

The zoonotic bacteria Salmonella enterica, Listeria monocytogenes, and Escherichia coli are known to infect dairy cows while not always causing clinical signs of disease. These pathogens are sometimes found in raw milk, and human disease outbreaks due to these organisms have been associated with the consumption of raw milk or raw milk products. Bulk tank milk (BTM) samples (536) and in-line milk filters (519) collected from dairy farms across the United States during the National Animal Health Monitoring System's Dairy 2007 study were analyzed by real-time PCR for the presence of S. enterica and pathogenic forms of E. coli and by culture techniques for the presence of L. monocytogenes. S. enterica was detected in samples from 28.1% of the dairy operations, primarily in milk filters. Salmonella was isolated from 36 of 75 PCR-positive BTM samples and 105 of 174 PCR-positive filter samples, and the isolates were serotyped. Cerro, Kentucky, Muenster, Anatum, and Newport were the most common serotypes. L. monocytogenes was isolated from 7.1% of the dairy operations, and the 1/2a complex was the most common serotype, followed by 1/2b and 4b (lineage 1). Shiga toxin genes were detected in enrichments from 15.2% of the BTM samples and from 51.0% of the filters by real-time PCR. In most cases, the cycle threshold values for the PCR indicated that toxigenic strains were not a major part of the enrichment populations. These data confirm those from earlier studies showing significant contamination of BTM by zoonotic bacterial pathogens and that the consumption of raw milk and raw milk products presents a health risk.

Observation of a new pattern in serogroup-related PCR typing of Listeria monocytogenes 4b isolates

Molecular serogroup-related PCR typing has made the determination of serotypes of Listeria monocytogenes isolates easy and rapid. Amplification of selected lineage- and serotype-related genes can produce serotype patterns reflecting the four major serotypes, 1/2a, 1/2b, 1/2c, and 4b. We found that four isolates in our routine testing had a pattern with the four bands lmo0737, ORF2110, ORF2819, and prs positive, a pattern which has not been previously reported in the literature. After testing with a lineage-specific PCR, hybridization, and conventional agglutination serotyping, the isolates with the new pattern were considered to be serotype 4b.

Central nervous system infection with Listeria monocytogenes

The foodborne pathogen Listeria monocytogenes has a particular tropism for the central nervous system and can produce infection in the meninges and brain substance. Well-recognized clinical syndromes include meningitis, brain abscess, rhombencephalitis, and spinal cord abscess; simultaneous infection of the meninges and brain is common. Although it is an uncommon cause of infection in the population at large, L. monocytogenes is an important cause of central nervous system infection in those with impaired cell-mediated immunity, whether due to underlying disease or treatment with immunosuppressive therapeutic agents; it is the etiology in 20% of bacterial meningitis cases in neonates and in 20% of cases in those older than 50 years. Ampicillin is considered the treatment of choice, and trimethoprim-sulfamethoxazole is recommended for those allergic to penicillin. At-risk patients should be advised to avoid unpasteurized milk and soft cheeses along with deli-style, ready-to-eat prepared meats, particularly poultry products.

Risk of Listeria monocytogenes contamination of raw ready-to-eat seafood products available at retail outlets in Japan

Examination of Listeria monocytogenes prevalence among ready-to-eat foods in Japan revealed frequent (5.7 to 12.1%) contamination of minced tuna and fish roe products, and the isolates had the same virulence levels as clinical isolates in terms of invasion efficiency and infectivity in cell cultures and a murine infection model, respectively. Premature stop codons in inlA were infrequent (1 out of 39 isolates). Cell numbers of L. monocytogenes in minced tuna and salmon roe increased rapidly under inappropriate storage temperatures (from a most probable number [MPN] of 10(0) to 10(1)/g to an MPN of 10(3) to 10(4)/g over the course of 2 days at 10 degrees C). Thus, regulatory guidelines are needed for acceptable levels of L. monocytogenes in these foods.