Listeriosis in Iceland, 1978-2000: a description of cases and molecular epidemiology

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.

Epidemiology and clinical characteristics of Listeria monocytogenes bacteremia in a Taiwanese medical center

BACKGROUND/PURPOSE

There have been many reported cases of Listeria monocytogenes bacteremia in Europe and the United States, but only a few from Taiwan. The present study was undertaken to analyze the clinical characteristics of patients with L. monocytogenes bacteremia in Taiwan.

METHODS

Patients with culture-confirmed L. monocytogenes bacteremia were identified at Chang Gung Memorial Hospital between January 2001 and December 2008. The clinical features and outcomes of the patients and the antimicrobial susceptibilities of the clinical isolates were analyzed.

RESULTS

Forty-three patients, including two newborn babies (4.7%) and 41 adults (95.3%), with at least one episode of Listeria bacteremia were identified. Forty-two (97.7%) of these patients had underlying diseases. Thirty-three patients (76.7%) had fever, 14 (32.6%) had experienced respiratory distress, and 11 (25.6%) had reported changes in consciousness. Twelve patients died within 14 days of infection, corresponding to a case-fatality rate of 27.9%. All the clinical isolates tested were susceptible to ampicillin, penicillin and vancomycin.

CONCLUSION

Most cases of L. monocytogenes infection occurred in adults with underlying diseases, especially malignancy, and only two cases of neonatal L. monocytogenes bacteremia were identified over the 8-year period. Penicillin, ampicillin and vancomycin could be used for the treatment of L. monocytogenes bacteremia, with the case-fatality rate lower for patients who received appropriate treatment.

Surveillance for Listeria monocytogenes and listeriosis, 1995-2004

Canadian cases and outbreaks of illness caused by Listeria monocytogenes between 1995 and 2004 were assessed. Isolates (722 total) were characterized by serotyping, and pulsed-field gel electrophoresis (PFGE) was performed to provide a means of detecting case clusters. Rates of listeriosis remained fairly consistent during the period of study, and patient characteristics were similar to those seen in studies of other populations. Most isolates were obtained from blood and cerebrospinal fluid, although during some outbreak investigations isolates were also obtained from stools. Serotype 1/2a predominated in isolates from patients in Canada, followed by serotypes 4b and 1/2b. Outbreaks caused by L. monocytogenes that occurred during the period of study were caused by isolates with serotypes 1/2a and 4b. A retrospective analysis of PFGE data uncovered several clusters that might have represented undetected outbreaks, suggesting that comprehensive prospective PFGE analysis coupled with prompt epidemiological investigations might lead to improved outbreak detection and control.

Listeriosis in Norway 1977–2003

In Europe, the incidence of invasive listeriosis has increased substantially during the last decades. We here present data from 289 listeriosis cases reported in Norway during the period 1977-2003, of which 12 cases were associated with 2 outbreaks and 39 cases were pregnancy-related. Medical records were obtained from 209 cases with listeriosis reported in 1977-2000. While the incidence of pregnancy-related listeriosis has remained stable at an average rate of 34 per million pregnant women per y during the period, the incidence of sporadic, non-pregnancy-related cases has increased from 1.1 to 3.7 per million per y. The present Norwegian incidence of reported cases is lower than in Denmark, but the case fatality rate is higher, indicating a possible under-reporting of mild listeriosis cases in Norway. We discuss how preventive measures, case identification and surveillance may have influenced listeriosis incidence in Norway.

Impact of -2 degrees C superchilling before refrigerated storage (4 and 8 degrees C) on the microbiological and sensory qualities of cold-smoked salmon

Detection and enumeration of Listeria monocytogenes and total spoilage bacteria in 40 batches of cold-smoked salmon (one batch = 42 products from the same day of manufacture) straight from the factory were carried out. If L. monocytogenes was detected in at least one of the nine samples analyzed on receipt at the laboratory, 9 products of the same batch were stored for 10 days at 4 degrees C, which was followed by 18 days at 8 degrees C (control), 12 products were superchilled for 14 days at -2 degrees C, and 12 other products were superchilled for 28 days at -2 degrees C and then stored under the same conditions as the control was stored. L. monocytogenes was detected in 7% of the 40 batches analyzed immediately after receipt at the laboratory. L. monocytogenes prevalence was similar (approximately 25%) throughout the storage at 4 and 8 degrees C, both in control and super-chilled products at -2 degrees C for 14 days. After superchilling for 28 days at -2 degrees C, L. monocytogenes was found in 9% of products, and in 39% at the end of the storage above 0 degree C. Moreover, the L. monocytogenes count was higher after 3 and 4 weeks of storage at 4 and 8 degrees C in products superchilled 28 days at -2 degrees C than in control products or in products superchilled for 14 days. Serotype 1/2a-3a and nine genetic groups were identified and found throughout the storage scenario. At the end of shelf life, sensory characteristics of products superchilled for 28 days at -2 degrees C were slightly modified. A decrease in firmness associated with increased tearing of salmon slices was observed as well as a slight amine odor.

A survey of laboratory-confirmed isolates of invasive listeriosis in Israel, 1997–2007

During the 11-year period from 1997 to 2007, 321 isolates ofListeria monocytogenesfrom sporadic cases of invasive listeriosis were reported to the national reference laboratory in Israel. Of these isolates, 113 (35%) were identified from perinatal cases, and 208 (65%) from non-perinatal cases. The prevalent serovars were 4b, 1/2b, 1/2a and 4c. Serovar 4b was identified in 80·5% of the perinatal isolates (P=0·0162), while the number of 1/2b and 1/2a strains increased in the ⩾60 years old group (P=0·0285). Resistance to tetracycline was found in eight 4b isolates. The seasonal distribution showed that 206 isolates (64·2%) were submitted during the hot season (May–October). The estimated morbidity for the study period was 4·4 per million. The incidence of invasive listeriosis was higher in the perinatal group (5·6/100 000), than in individuals aged ⩾60 years (1·5/100 000).

Connatal listeriosis--a case report and the possibilities of microbiological diagnosis

The third most frequent agent of perinatal bacterial meningitis is Listeria monocytogenes, in Hungary, its occurrence is, however, uncommon. This raises the possibility of diagnostical mistakes. A connatal listeriosis case validated microbiologically referred to in this report calls attention to Listeria, as a rare but relevant pathogen of neonatal infections. If clinical background suggests infection, the pathogenic role of L. monocytogenes should be taken into consideration. The etiological significance of the agent has to be verified by a competent clinical microbiology laboratory, since maternal listeriosis should be treated and the serious connatal manifestations should be prevented. Epidemiology of perinatal infection by L. monocytogenes, and its diagnostic tools especially the use of selective media are discussed.

Antimicrobial susceptibility of Listeria monocytogenes from food products

This study was conducted to determine the susceptibility of Listeria monocytogenes isolated from food products to antimicrobial agents commonly used for treatment of infections with gram-positive bacteria, and to disinfectants. A total of 114 L. monocytogenes retail isolates were tested for susceptibility to ceftiofur, chloramphenicol, ciprofloxacin, erythromycin, florfenicol, penicillin, spectinomycin, streptomycin, tetracycline, tiamulin, trimethoprim, and co-trimoxazole, and the disinfectants benzalkonium chloride and triclosan, by determination of minimum inhibitory concentrations (MICs). All isolates were resistant to ceftiofur, but susceptible to the other antibiotics. A single isolate had a MIC of 4 mg/L for ciprofloxacin. For tiamulin. the MIC values were around the breakpoint used. Most isolates had MICs for triclosan at 16 mg/L. The MICs for benzalkonium chloride formed a bimodal distribution, with 105 isolates having a MIC of 4 mg/L and 9 isolates MICs of 16 and 32 mg/L. This study showed that Danish isolates of L. monocytogenes have not developed or acquired resistance to antimicrobial agents used for treatment or disinfection, except for benzalkonium chloride. The MICs for triclosan was high compared to other gram-positive bacteria, suggesting that triclosan might not be useful against L. monocytogenes if incorporated in materials in the food industry.

Virulence of Listeria monocytogenes isolates from humans and smoked salmon, peeled shrimp, and their processing environments

The virulence of 82 Listeria monocytogenes isolates from human cases and cold-smoked salmon, cooked peeled shrimp, and their production environments was assessed using the plaque-forming assay and a subcutaneous inoculation test in mice. These isolates were previously typed using serotyping and pulsed-field gel electrophoresis. The isolates from food-production environments were collected in several surveys over the period of 5 years. Sixty-eight (99.8%) of 69 isolates tested from food and food-processing environments were considered virulent while only one was avirulent. All clinical isolates (13) were highly virulent. The isolates were from raw materials, final products, and the production environment. This stresses the importance of hygiene in the processing environment as well as among personnel to avoid contamination of the final product.

[Molecular epidemiology of Listeria monocytogenes infections in a health district of Madrid in a 3-year period (2001-2003)]

INTRODUCTION

During 2003, an increase in the number of cases of listeriosis was observed in a tertiary hospital in Madrid. The objectives of this study were to review the clinical characteristics of the cases diagnosed from 2001 to 2003 and to investigate clonal relationships among the clinical isolates of Listeria monocytogenes.

METHODS

A retrospective analysis was performed of all cases of listeriosis diagnosed in Hospital 12 de Octubre (Madrid) during 2001-2003. Clinical records for each patient were reviewed and all clinical isolates were compared using serotyping and pulsed-field gel electrophoresis (PFGE) with the AscI and SmaI restriction enzymes.

RESULTS

A total of 18 patients were diagnosed: 4 in 2001, 2 in 2002, and 12 in 2003. The estimated incidence rates were 7.3 cases per 1,000,000 inhabitants in 2001, 3.6 in 2002 and 21.8 in 2003. The most frequent serotype during the study period was 4b (66.7%), and this serotype represented 83.3% of the cases diagnosed in 2003. PFGE yielded 12 different genotypes; one of them (PFGE type G) was common to 5 cases diagnosed in 2003.

CONCLUSION

The expansion of a single clone of L. monocytogenes during 2003 partially contributed to increasing the incidence of listeriosis that year. Molecular epidemiology techniques are useful for detecting outbreaks of a possible foodborne origin and their results should promote epidemiological studies to investigate the food products involved.

Methods for the isolation and identification of Listeria spp. and Listeria monocytogenes: a review

Listeria monocytogenes is an important food-borne pathogen and is widely tested for in food, environmental and clinical samples. Identification traditionally involved culture methods based on selective enrichment and plating followed by the characterization of Listeria spp. based on colony morphology, sugar fermentation and haemolytic properties. These methods are the gold standard; but they are lengthy and may not be suitable for testing of foods with short shelf lives. As a result more rapid tests were developed based on antibodies (ELISA) or molecular techniques (PCR or DNA hybridization). While these tests possess equal sensitivity, they are rapid and allow testing to be completed within 48 h. More recently, molecular methods were developed that target RNA rather than DNA, such as RT-PCR, real time PCR or nucleic acid based sequence amplification (NASBA). These tests not only provide a measure of cell viability but they can also be used for quantitative analysis. In addition, a variety of tests are available for sub-species characterization, which are particularly useful in epidemiological investigations. Early typing methods differentiated isolates based on phenotypic markers, such as multilocus enzyme electrophoresis, phage typing and serotyping. These phenotypic typing methods are being replaced by molecular tests, which reflect genetic relationships between isolates and are more accurate. These new methods are currently mainly used in research but their considerable potential for routine testing in the future cannot be overlooked.