Listeriosis is a serious disease for humans; the overt form of the disease has a
case-fatality rate of around 20–30%. The two main clinical manifestations are
sepsis and
meningitis. Meningitis is often complicated by
encephalitis, when it is known as
meningoencephalitis, a pathology that is unusual for bacterial infections. L. ivanovii is a pathogen of
mammals, specifically
ruminants, and has rarely caused listeriosis in humans.[5] The incubation period can vary from three to 70 days.[6]
Background
In the late 1920s, two groups of researchers independently identified L. monocytogenes from animal outbreaks, naming it Bacterium monocytogenes.[7][8] They proposed the genus Listerella in honour of surgeon and early antiseptic advocate Joseph Lister, but that name was already in use for a
slime mould and a
protozoan. Eventually, the genus Listeria was proposed and accepted. The genus Listeria was classified in the family Corynebacteriaceae through the seventh edition (1957) of Bergey's Manual of Systematic Bacteriology.
16S rRNA cataloging studies demonstrated that L. monocytogenes is a distinct taxon within the Lactobacillus-
Bacillus branch of the bacterial phylogeny[9] constructed by Woese. In 2004 the genus was placed in the newly created family
Listeriaceae, of which the only other genus in the family is Brochothrix.[10][11] The first documented human case of listeriosis was in 1929, described by the Danish physician Aage Nyfeldt.[12]
The genus Listeria as of 2024[update] is known to contain 28 species, classified into two groups: sensu stricto and sensu lato.[13][3]Listeria sensu strictu contains L. monocytogenes alongside nine other closely related species: L. cossartiae,[14]L. farberi, L. immobilis,[14]L. innocua, L. ivanovii,[15]L. marthii,[16]L. seeligeri, L. swaminathanii[17] and L. welshimeri. Listeria sensu lato contains the remaining 18 species: L. aquatica,[18]L. booriae,[19]L. cornellensis,[18]L. costaricensis,[20]L. fleischmannii,[21]L. floridensis,[18]L. goaensis,[22]L. grandensis,[18]L. grayi, L. ilorinensis,[23]L. newyorkensis,[19]L. portnoyi,[14]L. riparia,[18]L. rocourtiae,[24]L. rustica,[14]L. thailandensis,[25]L. valentina[26] and L. weihenstephanensis.[27]Listeria dinitrificans, previously thought to be part of the genus Listeria, was reclassified into the new genus Jonesia.[28]
All species within the genus Listeria are
Gram-positive,
catalase-positive
rods and do not produce
endospores. Under the microscope, Listeria species appear as small rods, which are sometimes arranged in short chains. In direct smears, they may be
coccoid, and can be mistaken for
streptococci. Longer cells may resemble
corynebacteria.
Flagella are produced at room temperature, but not at 37 °C. Hemolytic activity on blood agar has been used as a marker to distinguish L. monocytogenes from other Listeria species, but it is not an absolutely definitive criterion. Further biochemical characterization may be necessary to distinguish between the different species of Listeria.[citation needed]
Listeria can be found in soil, which can lead to vegetable contamination. Animals can be carriers. Listeria has been found in uncooked meats, uncooked vegetables, fruits including
cantaloupe[29] and apples,[30] pasteurized or
unpasteurized milk, foods made from milk, and processed foods. Pasteurization and sufficient cooking kill Listeria; however, contamination may occur after cooking and before packaging. For example, meat-processing plants producing ready-to-eat foods, such as hot dogs and deli meats, must follow extensive sanitation policies and procedures to prevent Listeria contamination.[31]Listeria monocytogenes is commonly found in soil, stream water, sewage, plants, and food.[32]Listeria is responsible for listeriosis, a rare but potentially lethal
foodborne illness. The case fatality rate for those with a severe form of infection may approach 25%.[33] (Salmonellosis, in comparison, has a mortality rate estimated at less than 1%.[34]) Although L. monocytogenes has low infectivity, it is hardy and can grow in temperatures from 4 °C (39.2 °F) (the temperature of a refrigerator) to 37 °C (98.6 °F), (the body's internal temperature).[32] Listeriosis is a serious illness, and the disease may manifest as meningitis, or affect newborns due to its ability to penetrate the endothelial layer of the
placenta.[33]
Listeria uses the cellular machinery to move around inside the host cell. It induces directed polymerization of
actin by the
ActAtransmembrane protein, thus pushing the bacterial cell around.[35]
Listeria monocytogenes, for example, encodes virulence genes that are
thermoregulated. The expression of virulence factor is optimal at 39 °C, and is controlled by a transcriptional activator, PrfA, whose expression is thermoregulated by the
PrfA thermoregulator UTR element. At low temperatures, the PrfA transcript is not translated due to
structural elements near the ribosome binding site. As the bacteria infect the host, the temperature of the host denatures the structure and allows translation initiation for the virulent genes.[citation needed]
The majority of Listeria bacteria are attacked by the
immune system before they are able to cause
infection. Those that escape the immune system's initial response, however, spread through intracellular mechanisms, which protects them from circulating immune factors (AMI).[33]
To invade, Listeria induces macrophage
phagocytic uptake by displaying D-galactose in their
teichoic acids that are then bound by the
macrophage's
polysaccharides. Other important adhesins are the
internalins.[34]Listeria uses internalin A and B to bind to cellular receptors. Internalin A binds to E-cadherin, while internalin B binds to the cell's Met receptors. If both of these receptors have a high enough affinity to Listeria's internalin A and B, then it will be able to invade the cell via an indirect zipper mechanism.[citation needed] Once phagocytosed, the bacterium is encapsulated by the host cell's acidic
phagolysosome organelle.[32]Listeria, however, escapes the phagolysosome by lysing the vacuole's entire membrane with secreted
hemolysin,[36] now characterized as the exotoxin
listeriolysin O.[32] The bacteria then replicate inside the host cell's cytoplasm.[33]
Listeria must then navigate to the cell's periphery to spread the infection to other cells. Outside the body, Listeria has
flagellar-driven motility, sometimes described as a "tumbling motility". However, at 37 °C, flagella cease to develop and the bacterium instead usurps the host cell's
cytoskeleton to move.[33]Listeria, inventively, polymerizes an actin tail or "comet",[36] from actin monomers in the host's cytoplasm[37] with the promotion of virulence factor ActA.[33] The comet forms in a polar manner[38] and aids the bacterial migration to the host cell's outer membrane. Gelsolin, an actin filament severing protein, localizes at the tail of Listeria and accelerates the bacterium's motility.[38] Once at the cell surface, the actin-propelled Listeria pushes against the cell's membrane to form protrusions called
filopods[32] or "rockets". The protrusions are guided by the cell's leading edge[39] to contact adjacent cells, which then engulf the Listeria rocket and the process is repeated, perpetuating the infection.[33] Once phagocytosed, the bacterium is never again extracellular: it is an
intracellular parasite[36] like S. flexneri,Rickettsia spp., and
C. trachomatis.[33]
Epidemiology
The
Center for Science in the Public Interest has published a list of foods that have sometimes caused outbreaks of Listeria: hot dogs, deli meats, milk (even if
pasteurized), cheeses (particularly soft-ripened cheeses such as feta, Brie, Camembert, blue-veined, or Mexican-style queso blanco), raw and cooked poultry, raw meats, ice cream, raw fruit,[40] vegetables, and smoked fish.[41] Cold-cut meats were implicated in an
outbreak in Canada in 2008; improperly handled cantaloupe was implicated in both the
outbreak of listeriosis from Jensen Farms in Colorado in 2011,[42] and a similar listeriosis outbreak across eastern Australia in early 2018.[43][44] 35 people died across these two outbreaks.[42][45] The Australian company GMI Food Wholesalers was fined
A$236,000 for providing L. monocytogenes-contaminated
chicken wraps to the airline
Virgin Blue in 2011.[46] Caramel apples have also been cited as a source of listerial infections which hospitalized 26 people, of whom five died.[47][48] In 2019, the
United Kingdom experienced nine cases of the disease, of which six[49] were fatal, in an outbreak caused by contaminated meat (produced by North Country Cooked Meats) in hospital sandwiches.[50] In 2019, two people in Australia died after probably eating smoked salmon and a third fell ill but survived the disease.[51] In September 2019, three deaths and a miscarriage were reported in the Netherlands after the consumption of listeria-infected deli meats produced by Offerman.[52]
Prevention
Preventing listeriosis as a
foodborne illness requires effective sanitation of food contact surfaces.[53]Ethanol is an effective topical sanitizer against Listeria.
Quaternary ammonium can be used in conjunction with alcohol as a food-contact safe sanitizer with increased duration of the sanitizing action.
Keeping foods in the home refrigerated below 4 °C (39 °F) discourages bacterial growth. Unpasteurized dairy products may pose a risk.[54] Cooking all meats (including beef, pork, poultry, and seafood) to a safe internal temperature, typically 73 °C (165 °F), will kill the food-borne pathogen.[55]
Treatment
Non-invasive listeriosis: bacteria are retained within the digestive tract. Symptoms are mild, lasting only a few days and requiring only supportive care. Muscle pain and fever can be treated with over-the-counter pain relievers; diarrhea and gastroenteritis can be treated with over-the-counter medications.[55]
Invasive listeriosis: bacteria have spread to the bloodstream and central nervous system. Treatment includes intravenous delivery of high-dose
antibiotics and hospital in-patient care of (probably) not less than two weeks stay, depending on the extent of the infection.[55]Ampicillin,
penicillin, or
amoxicillin are typically administered for invasive listeriosis;
gentamicin may be added in cases of patients with compromised immune systems.[56] In cases of allergy to penicillin,
trimethoprim-sulfamethoxazole,
vancomycin, and
fluoroquinolones may be used.[56] For effective treatment the antibiotic must penetrate the host cell and bind to
penicillin-binding protein 3 (PBP3).
Cephalosporins are not effective for treating listeriosis.[56]
In cases of pregnancy, prompt treatment is critical to prevent bacteria from infecting the
fetus; antibiotics may be given to pregnant women even in non-invasive listeriosis.[57] Mirena Nikolova, et al., states that applying antibiotics is crucial during the third trimester because cell-mediated immunity is reduced during this time. Pfaff and Tillet say that listeriosis can cause long-term consequences—including meningitis, preterm labor, newborn sepsis, stillbirths—when contracted during pregnancy. Oral therapies in less severe cases may include amoxicillin or
erythromycin.[56] Higher doses may be given to pregnant women to ensure penetration of the
umbilical cord and
placenta.[58] Infected pregnant women may receive
ultrasound scans to monitor the health of the fetus.
Asymptomatic patients who have been exposed to Listeria typically are not treated, but are informed of the signs and symptoms of the disease and advised to return for treatment if any develop.[55]
Research
Some Listeria species are opportunistic pathogens: L. monocytogenes is most prevalent in the elderly, pregnant mothers, and patients infected with HIV. With improved healthcare leading to a growing elderly population and extended life expectancies for HIV infected patients, physicians are more likely to encounter this otherwise-rare infection (only seven per 1,000,000 healthy people are infected with virulent Listeria each year).[32] Better understanding the cell biology of Listeria infections, including relevant virulence factors, may lead to better treatments for listeriosis and other intracytoplasmic parasite infections.
In oncology, researchers are investigating the use of Listeria as a cancer vaccine, taking advantage of its "ability to induce potent innate and adaptive immunity" by activating
gamma delta T cells. [37][59]
^Jones, D. 1992. Current classification of the genus Listeria. In: Listeria 1992. Abstracts of ISOPOL XI, Copenhagen, Denmark). p. 7-8. ocourt, J., P. Boerlin, F.Grimont, C. Jacquet, and J-C. Piffaretti. 1992. Assignment of Listeria grayi and Listeria murrayi to a single species, Listeria grayi, with a revised description of Listeria grayi. Int. J. Syst. Bacteriol. 42:171-174.
^Boerlin et al. 1992. L. ivanovii subsp. londoniensis subsp. novi. Int. J. Syst. Bacteriol. 42:69-73. Jones, D., and H.P.R. Seeliger. 1986. International committee on systematic bacteriology. Subcommittee the taxonomy of Listeria. Int. J. Syst. Bacteriol. 36:117-118.
^
abcdefSouthwick, F. S.; D. L. Purich.
"More About Listeria". University of Florida Medical School. Archived from
the original on 22 February 2001. Retrieved 7 March 2007. [No longer accessible. Archived version available
here.]
Bredholt S.; Maukonen J.; Kujanpaa K.; Alanko T.; Olofson U.; Husmark U.; Sjoberg A. M.; Wirtanen G. (1999). "Microbial methods for assessment of cleaning and disinfection of food-processing surfaces cleaned in a low-pressure system". European Food Research and Technology. 209 (2): 145–152.
doi:
10.1007/s002170050474.
S2CID96177510.
Foschino R.; Picozzi C.; Civardi A.; Bandini M.; Faroldi P. (2003). "Comparison of surface sampling methods and cleanability assessment of stainless steel surfaces subjected or not to shot peening". Journal of Food Engineering. 60 (4): 375–381.
doi:
10.1016/S0260-8774(03)00060-8.
Frank, J. F. 2001. "Microbial attachment to food and food contact surfaces". In: Advances in Food and Nutrition Research, Vol. 43. ed. Taylor, S. L. San Diego, CA. Academic Press., Inc. 320–370.
Kusumaningrum H. D.; Riboldi G.; Hazeleger W. C.; Beumer R. R. (2003). "Survival of foodborne pathogens on stainless steel surfaces and cross-contamination to foods". International Journal of Food Microbiology. 85 (3): 227–236.
doi:
10.1016/S0168-1605(02)00540-8.
PMID12878381.
Nikolova, M., Todorova, T. T., Tsankova, G., & Ermenlieva, N. (2016). А possible case of а newborn premature baby with Listeria monocytogenes infection. Scripta Scientifica Medica, 48(2).
Maxcy R. B. (1975). "Fate of bacteria exposed to washing and drying on stainless steel". Journal of Milk and Food Technology. 38 (4): 192–194.
doi:
10.4315/0022-2747-38.4.192.
McInnes C.; Engel D.; Martin R. W. (1993). "Fimbriae damage and removal of adherent bacteria after exposure to acoustic energy". Oral Microbiology and Immunology. 8 (5): 277–282.
doi:
10.1111/j.1399-302X.1993.tb00574.x.
PMID7903443.
McLauchlin J. (1996). "The relationship between Listeria and listeriosis". Food Control. 7 (45): 187–193.
doi:
10.1016/S0956-7135(96)00038-2.
Moore G.; Griffith C.; Fielding L. (2001). "A comparison of traditional and recently developed methods for monitoring surface hygiene within the food industry: a laboratory study". Dairy, Food, and Environmental Sanitation. 21: 478–488.
Moore G.; Griffith C. (2002a). "Factors influencing recovery of microorganisms from surfaces by use of traditional hygiene swabbing". Dairy, Food, and Environmental Sanitation. 22: 410–421.
Pfaff, N. F., & Tillett, J. (2016). Listeriosis and Toxoplasmosis in Pregnancy: Essentials for Healthcare Providers. The Journal of perinatal & neonatal nursing, 30(2), 131.
Seymour I. J.; Burfoot D.; Smith R. L.; Cox L. A.; Lockwood A. (2002). "Ultrasound decontamination of minimally processed fruits and vegetables". International Journal of Food Science and Technology. 37 (5): 547–557.
doi:
10.1046/j.1365-2621.2002.00613.x.
Stanford C. M.; Srikantha R.; Wu C. D. (1997). "Efficacy of the Sonicare toothbrush fluid dynamic action on removal of supragingival plaque". Journal of Clinical Dentistry. 8 (1): 10–14.
Whyte W.; Carson W.; Hambraeus A. (1989). "Methods for calculating the efficiency of bacterial surface sampling techniques". Journal of Hospital Infection. 13 (1): 33–41.
doi:
10.1016/0195-6701(89)90093-5.
PMID2564016.
Wu-Yuan C. D.; Anderson R. D. (1994). "Ability of the SonicareÆ electronic toothbrush to generate dynamic fluid activity that removes bacteria". The Journal of Clinical Dentistry. 5 (3): 89–93.
Zottola E. A., Sasahara K. C.; Sasahara (1994). "Microbial biofilms in the food processing industry ñ should they be a concern?". International Journal of Food Microbiology. 23 (2): 125–148.
doi:
10.1016/0168-1605(94)90047-7.
PMID7848776.