Pregnancy-associated listeriosis

Christie, Atkins, Munch-Peterson (CAMP) Negative Listeria monocytogenes Meningitis in Neonates: Report of Two Cases

Listeria monocytogenes, a gram-positive bacillus and an intracellular pathogen, is an uncommon cause of illness in the general population. During pregnancy, a perinatal infection can lead to serious complications such as abortion, stillbirth, neonatal sepsis, and meningitis. We present two cases of neonatal meningitis caused by Christie, Atkins, Munch-Peterson (CAMP)-negative Listeria monocytogenes. In the first case, a seven-day-old female term neonate delivered vaginally, presented with high-grade fever and refusal to feed. In view of the suspected late-onset sepsis, a septic workup, including cerebrospinal fluid analysis, was conducted. CSF culture reports obtained showed a growth consistent with Listeria monocytogenes, which was CAMP test negative and susceptible to the penicillin group of drugs, cotrimoxazole, erythromycin, and meropenem. The isolate was identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and confirmed by 16S rRNA sequencing. The blood culture was sterile. At 48 hours of admission, the neonate clinically deteriorated with fluctuation in oxygen saturation below 95% at room air. Thus, she was electively intubated and connected to the mechanical ventilator with appropriate settings. The antibiotics were upgraded to meropenem from the empirical antibiotic therapy. The neonate showed clinical improvement within the next 24 hours of initiating antibiotics according to culture susceptibility and was gradually weaned from the mechanical ventilator to continuous positive airway pressure (CPAP). After 24 hours, she was able to maintain normal saturation at room air. In the second case, an 11-day-old low birth weight neonate, small for gestational age, was presented to the NICU with complaints of loose stools, fever, and refusal to feed for the past two days. In view of the suspected sepsis, relevant investigations were carried out while initiating empirical antibiotics IV piperacillin-tazobactam and IV amikacin for the neonate. Meanwhile, there was a dip in oxygen saturation noted on room air for the neonate and he/she was mechanically ventilated. The CSF culture grew Listeria monocytogenes,which was identified using MALDI-TOF MS and confirmed by 16S rRNA sequencing. The isolate tested negative for the CAMP test and was susceptible to ampicillin, penicillin, cotrimoxazole, erythromycin, and meropenem. The blood culture was sterile. The antibiotics were upgraded to meropenem from the empirical antibiotic therapy, the patient's condition improved, and the baby was eventually discharged.

La listeriosi neonatale e materno-fetale

Listeriosis is a foodborne condition associated with the ingestion of food contaminated by Listeria monocytogenes that can cause serious health consequences in neonates and pregnant women. In these groups the incidence of the disease is higher due to the relative immunocompromised state and the particular Listeria monocytogenes tropism for the placenta. The paediatrician and the neonatologist must therefore be able to recognize the signs and symptoms of the disease promptly so as to set up an adequate treatment according to the most recent international guidelines. This article provides epidemiological data and describes the pathophysiology and clinical manifestations of maternal-foetal and neonatal listeriosis, as well as the therapeutic indications according to very recent recommendations.

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.

Maternal and obstetric outcomes of listeria pregnancy: insights from a national cohort

OBJECTIVE

We sought to evaluate and describe the maternal and obstetric morbidity associated with Listeria infection in pregnancy.

METHODS

Retrospective cohort of pregnant women using the 2007-2018 National Inpatient Sample. Pregnant women with discharge diagnosis codes consistent with Listeria infection were identified. Outcomes of deliveries complicated by Listeria infection were compared to those of delivery without this infection. The primary outcome was a composite of severe maternal morbidity. Secondary outcomes included components of the composite, maternal length of stay, mode of delivery, stillbirth, and preterm delivery.

RESULTS

We identified 134 maternity associated hospitalizations for Listeria (weighted national estimate 666), of which 72 (weighted national estimate of 358) were delivery admissions. Delivery admissions complicated by Listeria resulted in higher rates of severe maternal morbidity than those without, (30.9% vs. 1.6%, p<.001). In adjusted analyses, women with Listeria had 21.2-fold higher risk of severe maternal morbidity (95% CI: 14.0, 31.9) when compared to those without Listeria. Specifically, Listeria delivery admissions had higher rates of acute respiratory distress syndrome (2.8% vs. 0.1%, p<.001), mechanical ventilation (1.4% vs. 0.0%, p<.001), sepsis (28.1% vs. 0.1%, p<.001), and shock (1.4% vs. 0.0%, p<.001). Listeria delivery admissions also had higher rates of preterm birth (61.3% vs. 7.7%, p < 0.001) and stillbirth (13.5% vs. 0.7%, p<.001). Women hospitalized or delivered with Listeria infection were also more likely to have a cesarean delivery (57.9% vs. 32.9, p<.001) and the average length of stay for women with Listeria was also longer (4.0 days vs. 2.3 days, p<.001).

CONCLUSIONS

Women with Listeria infection in pregnancy have higher rates of severe maternal morbidity, specifically increased risk of sepsis, septic shock, and acute respiratory distress syndrome. Among delivery hospitalizations, these women also have higher rates of preterm birth and stillbirth.

Complications Associated with Foodborne Listeriosis: A Scoping Review

Listeria monocytogenes is a relatively rare but highly pathogenic bacterium that can cause foodborne infections. In the United States there are ∼1600 cases per year, 94% of which result in hospitalizations and 20% in deaths. Per-case burden is high because the disease also causes serious complications, including sepsis, encephalitis, meningitis, miscarriage, and stillbirth. The disease burden of L. monocytogenes is underestimated because some of these acute complications can also result in long-term outcomes. In this article, we conducted a scoping review of L. monocytogenes complications and longer term outcomes from articles published between 2000 and 2018. Search terms were developed for four major databases (PubMed, Scopus, Web of Science, and Embase) as well as gray literature and hand searches of review articles. We follow standard scoping review methodology and assessment. Out of 10,618 unique articles originally identified, 115 articles were included, representing 49 unique outcomes. The majority of studies were cohort designs (n = 67) and conducted in the United States or Europe (n = 98). Four major outcome groupings were death, neurological disorders, sepsis, and congenital infection. This study identifies substantial research on the common acute complications of L. monocytogenes and few long-term consequences of L. monocytogenes. We identify the need for additional studies to determine the longer term impacts of these acute complications.

A Whole Genome Sequencing-Based Epidemiological Investigation of a Pregnancy-Related Invasive Listeriosis Case in Central Italy

Listeriosis is currently the fifth most common foodborne disease in Europe. Most cases are sporadic; however, outbreaks have also been reported. Compared to other foodborne infections, listeriosis has a modest incidence but can cause life-threatening complications, especially in elderly or immunocompromised people and pregnant women. In the latter case, the pathology can be the cause of premature birth or spontaneous abortion, especially if the fetus is affected during the first months of gestation. The causative agent of listeriosis, Listeria monocytogenes, is characterized by the innate ability to survive in the environment and in food, even in adverse conditions and for long periods. Ready-to-eat food represents the category most at risk for contracting listeriosis. This study presents the result of an investigation carried out on a case of maternal-fetal transmission of listeriosis which occurred in 2020 in central Italy and which was linked, with a retrospective approach, to other cases residing in the same city of the pregnant woman. Thanks to the use of next-generation sequencing methodologies, it was possible to identify an outbreak of infection, linked to the consumption of ready-to-eat sliced products sold in a supermarket in the investigated city.

Pharmacological inhibition of Kv1.3 channel impairs TLR3/4 activation and type I IFN response and confers protection against Listeria monocytogenes infection

Emerging data have demonstrated the critical roles of potassium efflux in the innate immune system. However, the role of potassium efflux in TLR3/4 activation and type I interferon (IFN) responses are not well elucidated. In the present study, we found potassium efflux is essential for TLR3/4 signaling, which mediates the expression of IFN and its inducible gene Cxcl10 and proinflammatory cytokine gene TNF-α. Furthermore, pharmacological inhibition of Kv1.3 channel (PAP-1), but not Kir2.1, KCa3.1 or TWIK2, attenuated TLR3/4 receptor activation in macrophages. Mechanistically, PAP-1 suppressed LPS-induced inflammatory function through marked suppressing the activation of JNK mitogen-activated protein kinase (MAPK) and p65 subunit of nuclear factor-kB (NF-kB). Notably, PAP-1 effectively protected mice against Listeria monocytogenes induced infection. Our findings reveal that potassium efflux mediated by the Kv1.3 channel is essential for TLR3/4 activation and suggest that pharmacological inhibition of Kv1.3 may help to treat type I IFN related autoimmune diseases and bacterial infections.

Listeriosis in infants: Prospective surveillance studies in Canada and Switzerland

Objectives

International data on listeriosis during infancy from large populations are essential to guide evidence-based empiric antibiotic guidelines for sepsis in infancy. We aimed to determine the incidence, clinical manifestations, and outcome of listeriosis in infants <6 months of age in Canada and Switzerland.

Methods

Prospective, active surveillance of listeriosis in infants <6 months of age was conducted through the Canadian Paediatric Surveillance Program (May 2015 to April 2017) and the Swiss Paediatric Surveillance Unit (April 2017 to March 2018). Confirmed and probable cases were included.

Results

In Canada, eight sporadic listeriosis cases were reported (incidence, 1.1/100,000 live births/year). In Switzerland, four cases were reported (incidence, 4.5/100,000 live births/year) of which three were part of a confirmed outbreak with an unclear source. In the two countries, eight of the 12 cases (66.6%) presented as early-onset disease (within the first 7 days of life) and none presented after 28 days life.

Conclusions

Neonatal listeriosis is rare. Infants presenting with sepsis, especially after 4 weeks of life, may not routinely require empiric antibiotic coverage for listeriosis. Outbreak-related cases still occur. Continued surveillance is important.

Septicemia Due to Listeria monocytogenes Infection: A Systematic Review and Meta-Analysis

Listeriosis is a rare bacterial infection associated with foodborne illness that can result in septicemia, a serious acute outcome. Sepsis is responsible for one in three deaths during hospitalization. The objective of this study was to conduct a systematic review and meta-analysis to estimate the proportion of Listeria monocytogenes infections resulting in septicemia. PubMed, Embase, Scopus, and Web of Science were searched from January 1, 2000, to April 1, 2018, for epidemiological studies that assessed studies focusing on L. monocytogenes infections with the outcome of septicemia. Articles in English, Spanish, and Portuguese using case-control, cohort, or outbreak studies reporting measures of association between L. monocytogenes and septicemia were included. Bias and heterogeneity were assessed using univariate meta-regression for region, sample size, study design, and report method. Nineteen articles were eligible for inclusion post-screening, the majority of which were conducted in Europe (n = 15); utilized a retrospective cohort design (n = 16); and collected data via routine or laboratory surveillance methods (n = 10). Prevalence of sepsis ranged from 4.2% to 100% among study populations of 6 to 1374 individuals. Overall, the proportion of listeriosis cases that developed sepsis was 46% (95% confidence interval [CI] 31.0-61.0%); for neonatal cases, 21.3% (95% CI 11.0-31.6%); and for maternal and neonatal cases, 18.8% (95% CI 10.7-26.8%). The heterogeneity was high for overall and group meta-analyses, but it could not be explained by the subanalyses for the overall proportion, whereas for neonatal, and neonatal and maternal cases combined, China had a significantly lower proportion than Europe and the United States. Septicemia following L. monocytogenes infection is a severe acute complication with 31-61% rate found overall; however, greater delineation of demographic data is needed to determine important risk factors. Future research should aim to address the gaps in knowledge in the long-term outcomes of sepsis from L. monocytogenes infection, and whether these outcomes differ from those due to other infections.

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.

Systemic Lupus Erythematosus Complicated with Listeria Monocytogenes Infection in a Pregnant Woman

A 41-year-old woman with systemic lupus erythematosus (SLE) was admitted to our hospital due to a fever at 35 weeks of pregnancy. Laboratory testing revealed a low platelet count and elevated liver enzymes. Emergency Caesarean section was performed due to the risk of SLE exacerbation or hemolytic anemia, elevated liver enzyme, and low platelet count syndrome. Based on the blood culture results, the patient was diagnosed with Listeria monocytogenes bacteremia. She was treated with ampicillin and eventually recovered, and the neonate did not have any complications. Pregnant women with SLE are at risk of complications. Listeriosis should be monitored for and, if found, managed appropriately.

Neonatal listeriosis presentation and outcome: a prospective study of 189 cases

CONTEXT

Listeriosis is caused by the foodborne pathogen Listeria monocytogenes. It can present as a maternal-neonatal infection. We implemented the nationwide prospective cohort MONALISA and analyzed the features of neonatal listeriosis.

METHODS

We studied all neonates born alive from mothers with microbiologically-proven maternal-neonatal listeriosis enrolled from November 2009 to December 2017. We analyzed presentation, neonatal outcome at discharge and predictors of severe presentation and outcome. The study is registered at clinicaltrials.gov (NCT01520597).

RESULTS

We studied 189 infants. 133/189 (70%) had abnormal clinical status at birth, including acute respiratory distress in 106/189 (56%). 132/189 (70%) infants developed early-onset listeriosis and 12/189 (6%) late onset listeriosis who all presented with acute meningitis. 17/189 (9%) had major adverse outcomes: 3% death (5/189), 6% (12/189) severe brain injury, 2% (3/189) severe bronchopulmonary dysplasia, 15/17 in infants born < 34 weeks of gestation (p < 0.0001 versus infants born ≥ 34 weeks of gestation). Maternal antimicrobial treatment ≥ 1 day before delivery was associated with a significant decrease of infants' severity (resulting in significantly less inotropic drugs, fluid resuscitation, or mechanical ventilation requirement), OR 0.23 [95% confidence interval CI 0.09-0.51], p < 0.0001).

CONCLUSION

Antenatal maternal antimicrobial treatment is associated with reduced neonatal listeriosis severity, justifying the prescription of preemptive maternal antimicrobial therapy when maternal-fetal listeriosis is suspected. Neonatal outcome is better than reported earlier, and its major determinant is gestational age at birth.

Maternal Microbiome and Infections in Pregnancy

Pregnancy induces unique changes in maternal immune responses and metabolism. Drastic physiologic adaptations, in an intricately coordinated fashion, allow the maternal body to support the healthy growth of the fetus. The gut microbiome plays a central role in the regulation of the immune system, metabolism, and resistance to infections. Studies have reported changes in the maternal microbiome in the gut, vagina, and oral cavity during pregnancy; it remains unclear whether/how these changes might be related to maternal immune responses, metabolism, and susceptibility to infections during pregnancy. Our understanding of the concerted adaption of these different aspects of the human physiology to promote a successful pregnant remains limited. Here, we provide a comprehensive documentation and discussion of changes in the maternal microbiome in the gut, oral cavity, and vagina during pregnancy, metabolic changes and complications in the mother and newborn that may be, in part, driven by maternal gut dysbiosis, and, lastly, common infections in pregnancy. This review aims to shed light on how dysregulation of the maternal microbiome may underlie obstetrical metabolic complications and infections.

Maternal Immunological Adaptation During Normal Pregnancy

The risk and severity of specific infections are increased during pregnancy due to a combination of physiological and immunological changes. Characterizing the maternal immune system during pregnancy is important to understand how the maternal immune system maintains tolerance towards the allogeneic fetus. This may also inform strategies to prevent maternal fatalities due to infections and optimize maternal vaccination to best protect the mother-fetus dyad and the infant after birth. In this review, we describe what is known about the immunological changes that occur during a normal pregnancy.

A population model for the 2017/18 listeriosis outbreak in South Africa

We introduce a compartmental model of ordinary differential equations for the population dynamics of listeriosis, and we derive a model for analysing a listeriosis outbreak. The model explicitly accommodates neonatal infections. Similarly as is common in cholera modeling, we include a compartment to represent the reservoir of bacteria. We also include a compartment to represent the incubation phase. For the 2017/18 listeriosis outbreak that happened in South Africa, we calculate the time pattern and intensity of the force of infection, and we determine numerical values for some of the parameters in the model. The model is calibrated using South African data, together with existing data in the open literature not necessarily from South Africa. We make projections on the future outlook of the epidemiology of the disease and the possibility of eradication.

The epidemiology of listeriosis in pregnant women and children in New Zealand from 1997 to 2016: an observational study

Background

Listeria monocytogenes causes the foodborne infection listeriosis. Pregnant women, infants and immunocompromised children are at increased risk for infection. The aim of this study was to describe the trends in the epidemiology of disease notifications and hospital admissions due to listeriosis in pregnant women aged 15 to 45 years and children aged less than 15 years in New Zealand (NZ) from 1997 to 2016.

Methods

In this population-based descriptive study, listeriosis notification and hospitalization rates from 1997 to 2016 were analyzed. Notification data were extracted from the Institute of Environmental Science and Research (ESR) Notifiable Diseases Database (EpiSurv) and hospitalization data were extracted from the National Minimum Dataset (NMDS). Pregnant women aged 15 to 45 years and children less than 15 years of age were included. Subgroup analysis was conducted for age and ethnicity. Outcomes of infection were described.

Results

In the 20-year period considered, there were 147 pregnancy-associated cases of listeriosis either notified to ESR (n = 106) and/or coded in the NMDS (n = 99), giving a crude incidence rate of 12.3 (95% CI 10.4, 14.4) per 100,000 births. In addition, there were 22 cases in children aged 28 days to < 15 years (incidence =0.12, 95% CI 0.08 to 0.19 per 100,000). There were no trends observed over time in the incidence of pregnancy-associated listeriosis. Incidence rates of pregnancy-associated and childhood listeriosis were highest in people of Pacific and Asian ethnicity.

Conclusions

NZ has a low incidence of listeriosis in pregnant women and children, however, the consequences of infection are frequently severe. Those of Pacific and Asian ethnicity have the highest rates of disease and future messaging around food safety should target these groups. This study provides important insights into the epidemiology of listeriosis in pregnant women and children in NZ.

Attribution of Listeria monocytogenes human infections to food and animal sources in Northern Italy

Listeriosis is a foodborne illness characterized by a relatively low morbidity, but a large disease burden due to the severity of clinical manifestations and the high case fatality rate. Increased listeriosis notifications have been observed in Europe since the 2000s. However, the reasons for this increase are largely unknown, with the sources of sporadic human listerioris often remaining elusive. Here we inferred the relative contributions of several putative sources of Listeria monocytogenes strains from listerioris patients in Northern Italy (Piedmont and Lombardy regions), using two established source attribution models (i.e. 'Dutch' and 'STRUCTURE') in comparative fashion. We compared the Multi-Locus Sequence Typing and Multi-Virulence-Locus Sequence Typing profiles of strains collected from beef, dairy, fish, game, mixed foods, mixed meat, pork, and poultry. Overall, 634 L. monocytogenes isolates were collected from 2005 to 2016. In total, 40 clonal complexes and 51 virulence types were identified, with 36% of the isolates belonging to possible epidemic clones (i.e. genetically related strains from unrelated outbreaks). Source attribution analysis showed that 50% of human listerioris cases (95% Confidence Interval 44-55%) could be attributed to dairy products, followed by poultry and pork (15% each), and mixed foods (15%). Since the contamination of dairy, poultry and pork products are closely linked to primary production, expanding actions currently limited to ready-to-eat products to the reservoir level may help reducing the risk of cross-contamination at the consumer level.

Non-thermal inactivation of Listeria spp. in a typical dry-fermented sausage: "Bergamasco" salami

Aim of the present study was the evaluation of the growth potential of Listeria spp. inoculated in the typical North Italian dry fermented sausage "Bergamasco" salami during its production. As it was necessary to carry out the challenge test in the production line of the industry, according to the guidelines of the European Reference Laboratory for Listeria monocytogenes, a non-pathogenic "surrogate" microorganism was used: for the inoculum, two strains of Listeria innocua (1 ATCC, 1 strain isolated from a similar substrate) were used. The inoculation of the samples occurred during grinding and mixing of the sausage mass, before the filling. To avoid cross-contamination, the control samples were produced before the contaminated ones. After the dripping, salamis were subjected to the normal production process (drying and maturation in five steps at specific temperatures and humidity rates). The inoculated products were subjected to the enumeration of Listeria spp. at T0 (day of inoculation) and at T4 (post-drying), and every 10 days during curing (T10, T20, T30, T40, T50, T60, T70, T80 and T90), as this salami is generally sold as whole piece with varying levels of curing (from T20 to T90). Since the product may be cut in half and vacuumpacked, at each of the times starting from T20, half salami was vacuum-packed and stored for 30 days at 12°C, at the end of the which Listeria spp. enumeration was performed again. At all times and for each type of samples of each of the three batches, the enumeration of the natural microflora (Total Viable Count, lactic acid bacteria, Pseudomonas spp., Enterobacteriaceae) and the determination of water activity and pH were performed on control samples. The product was characterized by a high concentration of microflora (8-8.5 Log UFC/g), consisting mainly of lactic acid bacteria, added to the mixture at the beginning of the production process. The pH showed a decrease over time, expected for this type of products, due to the development of lactic acid bacteria (final pH: 5.42-5.55). The water activity reached values able to inhibit the development of Listeria spp. (final aw: 0.826-0.863). Listeria counts in the tested batches of "Bergamasco" salami showed the absence of significant growth in the product with a reduction of loads if compared to T0, between -0.59 and -1.04 Log CFU/g. Even in the samples subjected to vacuum packaging and storage at 12°C, the absence of significant increase of lactic acid bacteria in the product was highlighted with further decrease of bacterial loads (-0.70/-0.79 Log CFU/g if compared to T20). Considering the worst case scenario (thus the batch with the highest growth potential), in the products stored in the curing room at 14-16°C, at humidity of 80% and in the samples stored at 12°C and vacuum packaged, the threshold indicated by the EURL Lm guidelines (+0.5 Log CFU/g) for the growth of Listeria spp. was not reached, allowing to classify "Bergamasco" salami in the category 1.3 of the EC Reg. 2073/2005 as "Ready-to-eat food unable to support the growth of Listeria monocytogenes".

N-Glycosylation Plays an Essential and Species-Specific Role in Anti-Infection Function of Milk Proteins Using Listeria monocytogenes as Model Pathogen

The released milk N-glycome has been found to possess antipathogenic activity. Natively, they are covalently linked onto proteins. Whether the conjugated N-glycans still have antipathogenic properties and how the glycosylation influences the antipathogenic activity of proteins remain unclear. Herein, we compared the quantitative differences of milk protein N-glycosylation and the antilisterial differences of native milk proteins, released N-glycan pools, and deglycosylated proteins between human and bovine milk. N-glycosylation exhibited to be quantitatively species-specific. The entire growth inhibitory activity and the majority of the antiadhesive activity against Listeria monocytogenes of milk whey proteins, although not as high as the released N-glycans, are attributed to N-glycosylation. Moreover, all N-glycan-bearing samples from human milk showed better growth inhibitory activities than those from bovine milk. Generally, N-glycosylation significantly contributes to the antilisterial function of milk proteins and to the functional differences between species. This gives novel insights into the role of these glycoconjugates in nature.

Structure-Activity Relationships of the Bacteriocin Bactofencin A and Its Interaction with the Bacterial Membrane

The antimicrobial peptide bactofencin A is an unmodified non-pediocin-like bacteriocin that inhibits several clinically relevant pathogens, including Listeria monocytogenes and Staphylococcus aureus. Here we report the synthesis and structure-activity relationship studies of bactofencin A and novel analogues thereof. Synthetic bactofencin A was a potent inhibitor of L. monocytogenes (MIC = 8.0 μM) and S. aureus (MIC = 4.0 μM), similar to the bacteriocin produced naturally by Lactobacillus salivarius. Of particular interest is the fact that linear analogues lacking the disulfide bond found in bactofencin A were as potent and also active against several strains of methicillin-resistant S. aureus (MRSA) and one strain of vancomycin-resistant S. aureus (VRSA). Supported by the structure-activity relationship study, investigation of the interaction of bactofencin A with bacterial membrane by molecular dynamics simulations showed the importance of the positively charged N-terminal tail for peptide-membrane interaction. These results suggest that the C-terminal macrocycle is involved in target protein binding and bacterial growth inhibition.

Pregnancy-related listeriosis: frequency and genotypic characteristics of L. monocytogenes from human specimens in Kerman, Iran

Listeria monocytogenes is a foodborne pathogen that can pose serious complications during pregnancy and neonatal infection. This study aimed to determine the frequency of L. monocytogenes infection, prevalent serotypes, and virulence genes among pregnant women and those experiencing miscarriages in Kerman, Iran. Out of 200 vaginal swabs, 4.5 and 29.5% of specimens were positive for L. monocytogenes infection as identified by culture and molecular methods, respectively. The majority of isolates from positive cultures (89%) of pregnant women resulted in stillbirth, death, and blindness. The most prevalent virulence determinants were inl B, prf A, and act A. The majority of isolates were non-typable. A history of miscarriage and gestational age are known to be significantly associated with the presence of infection. This study emphasizes the importance of initial screening for L. monocytogenes in pregnant women in Iran. Molecular methods may be useful in this process. Increasing the awareness of pregnant women could be effective in reducing pregnancy-related listeriosis.

Emergence of Antibiotic Resistance in Listeria monocytogenes Isolated from Food Products: A Comprehensive Review

Listeria monocytogenes is an opportunistic pathogen that has been involved in several deadly illness outbreaks. Future outbreaks may be more difficult to manage because of the emergence of antibiotic resistance among L. monocytogenes strains isolated from food products. The present review summarizes the available evidence on the emergence of antibiotic resistance among L. monocytogenes strains isolated from food products and the possible ways this resistance has developed. Furthermore, the resistance of food L. monocytogenes isolates to antibiotics currently used in the treatment of human listeriosis such as penicillin, ampicillin, tetracycline, and gentamicin, has been documented. Acquisition of movable genetic elements is considered the major mechanism of antibiotic resistance development in L. monocytogenes. Efflux pumps have also been linked with resistance of L. monocytogenes to some antibiotics including fluoroquinolones. Some L. monocytogenes strains isolated from food products are intrinsically resistant to several antibiotics. However, factors in food processing chains and environments (from farm to table) including extensive or sub-inhibitory antibiotics use, horizontal gene transfer, exposure to environmental stresses, biofilm formation, and presence of persister cells play crucial roles in the development of antibiotic resistance by L. monocytogenes.

Listeriosis in Pregnancy: Practitioners' Food Safety Counselling Practices to Pregnant Women

OBJECTIVE

The relative risk of invasive listeriosis in pregnant women is approximately 20 times greater than the general population, and listeriosis during pregnancy can have negative consequences for pregnant women, their fetuses, and their newborns. Health care providers are valuable sources of information, but published data suggest that most providers are unaware of the risk factors for listeriosis or its propensity for pregnant women, and they do not counsel their pregnant patients about risks. The objective of this study was to determine knowledge and practices of Canadian perinatal care providers on food safety counselling to pregnant women.

METHODS

An anonymous bilingual online questionnaire that sought information about awareness, knowledge of risk factors, practices for counselling pregnant women, and practitioners' learning needs with regard to listeriosis was sent to 3199 nurses, midwives, family physicians, and obstetrician/gynaecologists in Canada, with a response rate of 24.4%.

RESULTS

Most respondents had heard of listeriosis, provided prenatal care, and attended deliveries. Rates of awareness of listeriosis were the same among professions and were independent of years in practice, whether practice was urban or rural, and province. One third of the respondents (35.7%) were aware that listeriosis was more common in pregnant women; a minority (18.7%) correctly identified the incubation period for listeriosis and the stage in pregnancy in which women are at highest risk (30.4%). Those respondents who did not counsel women about the risks of listeriosis during pregnancy reported a lack of information or knowledge as the main reason.

CONCLUSION

Advising pregnant women about behaviours and lifestyle habits to prevent infectious diseases remains important, and information about preventive practices needs to be complete and adequate. The health care providers who participated in this study did express a clear need for information related to food safety during pregnancy and listeriosis, as supported by their lack of knowledge in some areas. If that lack is remedied, the knowledge gained could improve counselling practices.

A Multi-well Format Polyacrylamide-based Assay for Studying the Effect of Extracellular Matrix Stiffness on the Bacterial Infection of Adherent Cells

Extracellular matrix stiffness comprises one of the multiple environmental mechanical stimuli that are well known to influence cellular behavior, function, and fate in general. Although increasingly more adherent cell types' responses to matrix stiffness have been characterized, how adherent cells' susceptibility to bacterial infection depends on matrix stiffness is largely unknown, as is the effect of bacterial infection on the biomechanics of host cells. We hypothesize that the susceptibility of host endothelial cells to a bacterial infection depends on the stiffness of the matrix on which these cells reside, and that the infection of the host cells with bacteria will change their biomechanics. To test these two hypotheses, endothelial cells were used as model hosts and Listeria monocytogenes as a model pathogen. By developing a novel multi-well format assay, we show that the effect of matrix stiffness on infection of endothelial cells by L. monocytogenes can be quantitatively assessed through flow cytometry and immunostaining followed by microscopy. In addition, using traction force microscopy, the effect of L. monocytogenes infection on host endothelial cell biomechanics can be studied. The proposed method allows for the analysis of the effect of tissue-relevant mechanics on bacterial infection of adherent cells, which is a critical step towards understanding the biomechanical interactions between cells, their extracellular matrix, and pathogenic bacteria. This method is also applicable to a wide variety of other types of studies on cell biomechanics and response to substrate stiffness where it is important to be able to perform many replicates in parallel in each experiment.

Synthesis, antimicrobial activity and conformational analysis of the class IIa bacteriocin pediocin PA-1 and analogs thereof

The antimicrobial peptide pediocin PA-1 is a class IIa bacteriocin that inhibits several clinically relevant pathogens including Listeria spp. Here we report the synthesis and characterization of whole pediocin PA-1 and novel analogs thereof using a combination of solid- and solution-phase strategies to overcome difficulties due to instability and undesired reactions. Pediocin PA-1 thus synthesized was a potent inhibitor of Listeria monocytogenes (MIC = 6.8 nM), similar to the bacteriocin produced naturally by Pediococcus acidilactici. Of particular interest is that linear analogs lacking both of the disulfide bridges characterizing pediocin PA-1 were as potent. One linear analog was also a strong inhibitor of Clostridium perfringens, another important food-borne pathogen. These results are discussed in light of conformational information derived from circular dichroism, solution NMR spectroscopy and structure-activity relationship studies.

Pregnancy-related listeriosis

About one in seven cases of listeriosis occurs in pregnant women, and, although listeriosis is rare, it is the third leading cause of death from food-borne infections. Pregnancy-related listeriosis increases the risk for fetal and neonatal mortality by approximately 21%. During pregnancy, infections are more likely to occur in the third trimester (66%) than the first trimester (3%). However, fetal and neonatal adverse effects are less common as gestational age increases or with older gestational age at birth. Pregnant women seem highly susceptible in some listeriosis outbreaks making up a large percentage of cases, whereas others contain very few. Whether this results from differences in strains of L. monocytogenes, exposures, or other factors remains to be determined. Food and Agriculture Organization of United Nations/World Health Organization (FAO/WHO) estimates the human lethal dose for 50% (LD₅₀ ) for fetal/neonatal loss is 1.9 × 10⁶ colony forming units (CFUs) L. monocytogenes. Animal models have been developed for pregnancy-related listeriosis showing similar susceptibility and clinical outcomes as in humans. Nonhuman primate and guinea pig animal models have similar (LD₅₀ ) values to the estimated human LD₅₀ . Additional animal studies are needed to understand the pathways leading to fetal and neonatal listeriosis in humans. More information is needed to understand dose response, to model risk for listeriosis at lower concentrations, and to determine why some pregnant women may be more susceptible than others. To better treat listeriosis during pregnancy, biomarkers for early diagnosis of listeriosis are also needed. Last, pregnant women need to be educated about avoiding high-risk foods, like Mexican-style cheese and ready-to-eat meats. Birth Defects Research 109:324-335, 2017.© 2017 Wiley Periodicals, Inc.

Matrix stiffness modulates infection of endothelial cells by Listeria monocytogenes via expression of cell surface vimentin

Extracellular matrix stiffness (ECM) is one of the many mechanical forces acting on mammalian adherent cells and an important determinant of cellular function. While the effect of ECM stiffness on many aspects of cellular behavior has been studied previously, how ECM stiffness might mediate susceptibility of host cells to infection by bacterial pathogens is hitherto unexplored. To address this open question, we manufactured hydrogels of varying physiologically relevant stiffness and seeded human microvascular endothelial cells (HMEC-1) on them. We then infected HMEC-1 with the bacterial pathogen Listeria monocytogenes (Lm) and found that adhesion of Lm to host cells increases monotonically with increasing matrix stiffness, an effect that requires the activity of focal adhesion kinase (FAK). We identified cell surface vimentin as a candidate surface receptor mediating stiffness-dependent adhesion of Lm to HMEC-1 and found that bacterial infection of these host cells is decreased when the amount of surface vimentin is reduced. Our results provide the first evidence that ECM stiffness can mediate the susceptibility of mammalian host cells to infection by a bacterial pathogen.

Food Safety Instruction Improves Knowledge and Behavior Risk and Protection Factors for Foodborne Illnesses in Pregnant Populations

Objective This study compared knowledge and food-handling behavior after pathogen-specific (experimental treatment) versus basic food safety instruction (active control) presented during nutrition education classes for low-income English- and Spanish-language pregnant women. Methods Subjects (n = 550) were randomly assigned to treatment groups in two different locations in the United States. Food safety instruction was part of an 8-lesson curriculum. Food safety knowledge and behavior were measured pre/post intervention. Descriptive data were analyzed by Chi-Square or ANOVA; changes after intervention were analyzed by regression analysis. Results Knowledge improved after intervention in the pathogen-specific treatment group compared to active control, especially among Spanish-language women. Behavior change after intervention for the pathogen-specific treatment group improved for thermometer usage, refrigeration and consumption of foods at high risk for safety; however, all other improvements in behavior were accounted for by intervention regardless of treatment group. As expected, higher pre-instruction behavioral competency limited potential gain in behavior post-instruction due to a ceiling effect. This effect was more dominant among English-language women. Improvements were also linked to formal education completed, a partner at home, and other children in the home. Conclusions for Practice This study demonstrated that pathogen-specific food safety instruction leads to enhance knowledge and food handling behaviors that may improve the public health of pregnant women and their unborn children, especially among Spanish-language women. More importantly, food safety instruction, even at the most basic level, benefited pregnant women's food safety knowledge and food-handling behavior after intervention.

Infections in Pregnancy

Infections during pregnancy may affect a developing fetus. If left untreated, these infections can lead to the death of the mother, fetus, or neonate and other adverse sequelae. There are many factors that impact infection during pregnancy, such as the immune system changes during pregnancy, hormonal flux, stress, and the microbiome. We review some of the outcomes of infection during pregnancy, such as preterm birth, chorioamnionitis, meningitis, hydrocephaly, developmental delays, microcephaly, and sepsis. Transmission routes are discussed regarding how a pregnant woman may pass her infection to her fetus. This is followed by examples of infection during pregnancy: bacterial, viral, parasitic, and fungal infections. There are many known organisms that are capable of producing similar congenital defects during pregnancy; however, whether these infections share common mechanisms of action is yet to be determined. To protect the health of pregnant women and their offspring, additional research is needed to understand how these intrauterine infections adversely affect pregnancies and/or neonates in order to develop prevention strategies and treatments.

Identification of potential antimicrobials against Salmonella typhimurium and Listeria monocytogenes using Quantitative Structure-Activity Relation modeling

The shelf-life of fresh carcasses and produce depends on the chemical and physical properties of antimicrobials currently used for treatment. For many years the gold standard of these antimicrobials has been Cetylpyridinium Chloride (CPC) a quaternary ammonium compound (QAC). CPC is very effective at removing bacterial pathogens from the surface of chicken but has not been approved for other products due to a toxic residue left behind after treatment. Currently there is also a rising trend in QAC resistant bacteria. In order to find new compounds that can combat both antimicrobial resistance and the toxic residue we have developed two Quantitative Structure-Activity Relationship (QSAR) models for Salmonella typhimurium and Listeria monocytogenes. These models have been shown to be accurate and reliable through multiple internal and external validation techniques. In processing these models we have also identified important descriptors and structures that may be key in producing a viable compound. With these models, development and testing of new compounds should be greatly simplified.

Progesterone impairs antigen-non-specific immune protection by CD8 T memory cells via interferon-γ gene hypermethylation

Pregnant women and animals have increased susceptibility to a variety of intracellular pathogens including Listeria monocytogenes (LM), which has been associated with significantly increased level of sex hormones such as progesterone. CD8 T memory(Tm) cell-mediated antigen-non-specific IFN-γ responses are critically required in the host defense against LM. However, whether and how increased progesterone during pregnancy modulates CD8 Tm cell-mediated antigen-non-specific IFN-γ production and immune protection against LM remain poorly understood. Here we show in pregnant women that increased serum progesterone levels are associated with DNA hypermethylation of IFN-γ gene promoter region and decreased IFN-γ production in CD8 Tm cells upon antigen-non-specific stimulation ex vivo. Moreover, IFN-γ gene hypermethylation and significantly reduced IFN-γ production post LM infection in antigen-non-specific CD8 Tm cells are also observed in pregnant mice or progesterone treated non-pregnant female mice, which is a reversible phenotype following demethylation treatment. Importantly, antigen-non-specific CD8 Tm cells from progesterone treated mice have impaired anti-LM protection when adoptive transferred in either pregnant wild type mice or IFN-γ-deficient mice, and demethylation treatment rescues the adoptive protection of such CD8 Tm cells. These data demonstrate that increased progesterone impairs immune protective functions of antigen-non-specific CD8 Tm cells via inducing IFN-γ gene hypermethylation. Our findings thus provide insights into a new mechanism through which increased female sex hormone regulate CD8 Tm cell functions during pregnancy.

Increased female sex hormones during pregnancy generate a temporary immune suppression status in the pregnant that protect the developing fetus from maternal rejection but renders the pregnant highly susceptible to various pathogens. However, molecular mechanisms underlying such an increased maternal susceptibility to pathogens during pregnancy remain to be further understood. Here we show in pregnant women that increased progesterone levels are associated with IFN-γ gene hypermethylation and reduced IFN-γ production in peripheral CD8 Tm cells. By using murine models of LM infection, for the first time we show a causal relationship between increased level of progesterone, a characteristic female sex hormone of pregnancy, and increased susceptibility to Listeria monocytogenes, an intracellular bacterium that endangers both the pregnant and the fetus. Such an impact on anti-listeria host defense is mediated through progesterone-induced IFN-γ gene hypermethylation in CD8 Tm cells, resulting in impaired IFN-γ production and reduced immune protection by antigen-non-specific CD8 Tm cells. This study provides new insights into molecular mechanisms underlying the increased susceptibility to intracellular pathogens during pregnancy.

Summary of Notifiable Infectious Diseases and Conditions - United States, 2015

The Summary of Notifiable Infectious Diseases and Conditions - United States, 2015 (hereafter referred to as the summary) contains the official statistics, in tabular and graphical form, for the reported occurrence of nationally notifiable infectious diseases and conditions in the United States for 2015. Unless otherwise noted, data are final totals for 2015 reported as of June 30, 2016. These statistics are collected and compiled from reports sent by U.S. state and territories, New York City, and District of Columbia health departments to the National Notifiable Diseases Surveillance System (NNDSS), which is operated by CDC in collaboration with the Council of State and Territorial Epidemiologists (CSTE). This summary is available at https://www.cdc.gov/MMWR/MMWR_nd/index.html. This site also includes summary publications from previous years.

Curcumin Promotes the Clearance of Listeria monocytogenes both In Vitro and In Vivo by Reducing Listeriolysin O Oligomers

The pore-forming toxin listeriolysin O (LLO), an essential virulence factor that is secreted by Listeria monocytogenes (L. monocytogenes), is responsible for bacterial breaching at the phagosomal membranes and subsequent release into the cytoplasm; it cannot be recognized by the host immune system. The vital role that LLO plays in bacterial pathogenicity and evading host immune clearance makes this virulence a promising target for addressing L. monocytogenes infection. In this study, we hypothesized that curcumin, a polyphenol derived from turmeric that could effectively inhibit LLO pore-forming activity, might be useful in the prevention or treatment of L. monocytogenes infection. Thus, the in vitro protective effects of curcumin against L. monocytogenes infection by targeting LLO were assessed via hemolytic activity assays, cytotoxicity tests, intracellular growth assays, and confocal microscopy. Our results revealed that treating infected macrophages with curcumin can lead to a decrease in LLO-mediated bacteria phagosomal escape and limit the intracellular growth of L. monocytogenes. Moreover, results from animal experiments show that this natural compound effectively increases protection against bacterial infection and helps the host to clear the invading pathogen completely from an animal model, establishing it as a potent antagonist of L. monocytogenes. The results from our molecular modeling and mutational analysis demonstrated that curcumin directly engages with domains 2 and 4 of LLO, thereby decreasing the hemolytic activity of LLO by influencing its oligomerization. Taken together, these results suggest that, as an antitoxin agent, curcumin can be further developed into a novel therapy against L. monocytogenes infections by targeting LLO.

Epidemiology and Molecular Typing of Pregnancy-Associated Listeriosis Cases in Lombardy, Italy, over a 10-Year Period (2005-2014)

In developed countries, pregnancy-related listeriosis accounts for 20–43% of total invasive listeriosis. This work describes the first pregnancy-related listeriosis survey in Italy based on two data sources, that is, mandatory notification system and regional laboratory-based network. Out of 610 listeriosis cases reported over a 10-year period, 40 were pregnancy-related (6.6%). Among these, 29 pregnancy-related isolates were available and have been analysed with serotyping, Pulsed-Field Gel Electrophoresis, and Multi-Virulence-Locus Sequence Typing. No maternal fatality was recorded, but 11 (29.7%) pregnancies resulted in a foetal death, a miscarriage, or a birth of a foetus dying immediately after birth. The average incidence of pregnancy-related listeriosis was 4.3 cases per 100000 births, and the proportion of pregnancy-associated listeriosis among ethnic minorities was significantly higher compared to the general population (30.0% versus 3.5%, P < 0.01). L. monocytogenes isolates belonged to serotypes 1/2a, 1/2b, and 4b, with the latter significantly more prevalent among pregnancy-related isolates. Twenty different pulsotypes were distinguished and 16 out of the 29 isolates were classified into seven clusters. A total of 16 virulence types (VTs) were identified. Five VTs accounted for 45% of the total cases and coincided with those of previously described Epidemic Clones (ECs) of L. monocytogenes.

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.

Attenuating Listeria monocytogenes Virulence by Targeting the Regulatory Protein PrfA

The transcriptional activator PrfA, a member of the Crp/Fnr family, controls the expression of some key virulence factors necessary for infection by the human bacterial pathogen Listeria monocytogenes. Phenotypic screening identified ring-fused 2-pyridone molecules that at low micromolar concentrations attenuate L. monocytogenes cellular uptake by reducing the expression of virulence genes. These inhibitors bind the transcriptional regulator PrfA and decrease its affinity for the consensus DNA-binding site. Structural characterization of this interaction revealed that one of the ring-fused 2-pyridones, compound 1, binds at two separate sites on the protein: one within a hydrophobic pocket or tunnel, located between the C- and N-terminal domains of PrfA, and the second in the vicinity of the DNA-binding helix-turn-helix motif. At both sites the compound interacts with residues important for PrfA activation and helix-turn-helix formation. Ring-fused 2-pyridones represent a new class of chemical probes for studying virulence in L. monocytogenes.

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Inhibitors of L. monocytogenes infectivity reduce virulence gene expression

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Binding of inhibitor to the PrfA regulator reduces affinity for its DNA motif

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First crystal structure of a Crp family regulator with an inhibitor

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Provides rationale for screening with Crp family transcriptional regulators

Structural basis for glutathione-mediated activation of the virulence regulatory protein PrfA in Listeria

Infection by the human bacterial pathogen Listeria monocytogenes is mainly controlled by the positive regulatory factor A (PrfA), a member of the Crp/Fnr family of transcriptional activators. Published data suggest that PrfA requires the binding of a cofactor for full activity, and it was recently proposed that glutathione (GSH) could fulfill this function. Here we report the crystal structures of PrfA in complex with GSH and in complex with GSH and its cognate DNA, the hly operator PrfA box motif. These structures reveal the structural basis for a GSH-mediated allosteric mode of activation of PrfA in the cytosol of the host cell. The crystal structure of PrfA_WT in complex only with DNA confirms that PrfA_WT can adopt a DNA binding-compatible structure without binding the GSH activator molecule. By binding to PrfA in the cytosol of the host cell, GSH induces the correct fold of the HTH motifs, thus priming the PrfA protein for DNA interaction.

Neonatal listeriosis in the UK 2004-2014

OBJECTIVE

To define the clinical features and outcomes of neonatal listeriosis, and identify the maternal risk factors to seek scope for improvement.

METHODS

Neonatal listeriosis was identified prospectively from a United Kingdom neonatal infection surveillance network (neonIN) between 2004 and 2014. The participating neonatal units completed a study-specific proforma.

RESULTS

The incidence of neonatal listeriosis was 3.4 per 100,000 live births. Of the 21 cases identified, 19 were confirmed with a median gestational age of 33 weeks and a median birth weight of 1960 g. The majority had clinical features (95%, 18/19), presented within the first 24 h (95%, 18/19), and received penicillin empirically (94%, 18/19). The neonatal case-fatality rate was 21% (24% if probable cases were included). A proportion of mothers were investigated (60%, 12/18) and diagnosed with listeriosis (58%, 7/12); 32% (6/19) were treated with antibiotics but only 33% (6/12) included penicillin.

DISCUSSION

Despite its rarity and the prompt and appropriate use of antibiotics neonatal listeriosis has a high case-fatality rate. There is room for improvement in the adherence to the empiric antibiotic choice for puerperal sepsis, according to the national guidelines as this, would target listeriosis. Strategies should be in place to prevent pregnancy-associated listeriosis in higher risk population.

Induced systemic listeriosis in Alectoris chukar chicks: clinical, histopathological and microbiological findings

1. Systemic listeriosis was induced in 14-d-old Chukar partridge chicks, Alectoris chukar, by intravenous injection of a suspension containing 10(6) cfu/ml of viable Listeria monocytogenes organisms to study the course of infection. 2. Septicaemic and encephalitic forms of listeriosis were observed in all birds. Infection resulted in a fever response 8-h post-inoculation. Disease rapidly developed over a 24-h period with decreased activity, lethargy, ruffled feathers, huddling, listlessness, inability to stand, wing droop, decreased feed and water consumption, growth depression, neural disturbances and finally death. Gross and histopathological changes were observed in the myocardium, proventriculus, gizzard, intestine, pancreas, kidney, liver, spleen, lung, meninges and joints. 3. The diversity of these clinical signs and lesions suggests a high susceptibility of Chukar partridge chicks to systemic listeriosis.

A Look inside the Listeria monocytogenes Biofilms Extracellular Matrix

Listeria monocytogenes is a foodborne pathogen able to persist in food industry and is responsible for a severe illness called listeriosis. The ability of L. monocytogenes to persist in environments is due to its capacity to form biofilms that are a sessile community of microorganisms embedded in a self-produced matrix of extracellular polymeric substances (EPS's). In this review, we summarized recent efforts performed in order to better characterize the polymeric substances that compose the extracellular matrix (ECM) of L. monocytogenes biofilms. EPS extraction and analysis led to the identification of polysaccharides, proteins, extracellular DNA, and other molecules within the listerial ECM. All this knowledge will be useful for increasing food protection, suggesting effective strategies for the minimization of persistence of L. monocytogenes in food industry environments.

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.

Pregnancy - associated human listeriosis: Virulence and genotypic analysis of Listeria monocytogenes from clinical samples

Listeria monocytogenes, a life-threatening pathogen, poses severe risk during pregnancy, may cause abortion, fetal death or neonatal morbidity in terms of septicemia and meningitis. The present study aimed at characterizing L. monocytogenes isolated from pregnant women based on serotyping, antibiotic susceptibility, virulence genes, in vivo pathogenicity test and ERIC- and REP-PCR fingerprint analyses. The results revealed that out of 3700 human clinical samples, a total of 30 (0.81%) isolates [12 (0.80%) from placental bit (1500), 18 (0.81%) from vaginal swab (2200)] were positive for L. monocytogenes. All the isolates belonged to serogroup 4b, and were + ve for virulence genes tested i.e. inlA, inlC, inlJ, plcA, prfA, actA, hlyA, and iap. Based on the mice inoculation tests, 20 isolates showed 100% and 4 isolates 60% relative virulence while 6 isolates were non-pathogenic. Moreover, 2 and 10 isolates were resistant to ciprofloxacin and cefoxitin, respectively, while the rest susceptible to other antibiotics used in this study. ERIC- and REP-PCR collectively depicted that the isolates from placental bit and vaginal swab had distinct PCR fingerprints except a few isolates with identical patterns. This study demonstrates prevalence of pathogenic strains mostly resistant to cefoxitin and/or ciprofloxacin. The results indicate the importance of isolating and characterizing the pathogen from human clinical samples as the pre-requisite for accurate epidemiological investigations.

Estimating the attack rate of pregnancy-associated listeriosis during a large outbreak

Background. In 2011, a multistate outbreak of listeriosis linked to contaminated cantaloupes raised concerns that many pregnant women might have been exposed to Listeria monocytogenes. Listeriosis during pregnancy can cause fetal death, premature delivery, and neonatal sepsis and meningitis. Little information is available to guide healthcare providers who care for asymptomatic pregnant women with suspected L. monocytogenes exposure. Methods. We tracked pregnancy-associated listeriosis cases using reportable diseases surveillance and enhanced surveillance for fetal death using vital records and inpatient fetal deaths data in Colorado. We surveyed 1,060 pregnant women about symptoms and exposures. We developed three methods to estimate how many pregnant women in Colorado ate the implicated cantaloupes, and we calculated attack rates. Results. One laboratory-confirmed case of listeriosis was associated with pregnancy. The fetal death rate did not increase significantly compared to preoutbreak periods. Approximately 6,500–12,000 pregnant women in Colorado might have eaten the contaminated cantaloupes, an attack rate of ~1 per 10,000 exposed pregnant women. Conclusions. Despite many exposures, the risk of pregnancy-associated listeriosis was low. Our methods for estimating attack rates may help during future outbreaks and product recalls. Our findings offer relevant considerations for management of asymptomatic pregnant women with possible L. monocytogenes exposure.