Digestion, General, Women's Health, Infant and Children | January 21, 2015 | Author: The Super Pharmacist
Listeriosis is a bacterial infection that usually develops after eating food contaminated by Listeria monocytogenes (commonly known as listeria). In the majority of people who catch the infection, listeriosis is relatively mild and results in fever, vomiting and diarrhoea that will usually last for around 72 hours and will pass without treatment. However, in some cases, listeriosis can spread to other parts of the body and manifest clinically as meningitis and sepsis.
The most recent global estimate of listeria incidence was undertaken by the World Health Organization, using data from 2010, and published in The Lancet medical journal. Acknowledging the shortfall in accurate information globally on infection rates as a result of inadequate surveillance structures, a systematic review of all available studies suggested that listeriosis resulted in 23,150 illnesses, resulting in 5463 deaths worldwide (1). The study suggested true incidence could be significantly higher than the given estimate, particularly in developing countries. It also highlighted that as listeriosis is not a notifiable disease, underreporting may also be an issue even in countries that have advanced surveillance.
Most cases of listeria are caused by eating food contaminated with the bacteria. The listeria bacteria has been identified in a range of ‘ready-to-eat’ foods including butter, soft cheeses, soft blue cheese, cooked slice meats and smoked salmon.
Several high profile outbreaks of listeria have taken place as a result of contaminated food being served to large numbers of people: badly handled cantaloupe was responsible for a mass listeria outbreak in the USA (2), as were listeria-contaminated chicken wraps that were provided to an airline in Australia (3). A batch of contaminated caramel apples caused listeria related complications in 28 individuals in 26 states across the USA, eventually resulting in the death of five people (4).
Good food hygiene reduces the risk of listeria being spread.
Other known causes include humans passing stools contaminated with listeria and passing the disease on through poor hygiene and failing to wash their hands. Vegetables grown in soil contaminated with listeria can also carry the disease, so it is important that they are washed and prepared properly. Meat and dairy products can become contaminated if they are taken from animals that are infected with the bacteria. Most listeria can be removed through cooking food thoroughly, or the process of pasteurisation.
Some people are at increased risk of developing listeriosis:
People who fall into these categories are at heightened risk of sepsis and meningitis related complications and should exercise caution when dealing with foods or substances that are known to carry listeria (5). The WHO global incidence report highlighted that 20% of all reported cases of listeria infection were in pregnant women.
For less severe cases of listeriosis (also known as non-invasive listeriosis), bacteria will often remain solely in the digestive tract.
Over the counter medications such as paracetamol and ibuprofen will be sufficient to treat any feverish symptoms. It is important for individuals who have severe diarrhoea as a result of listeriosis to also make sure they are fully rehydrated.
Where the bacterium has spread to the bloodstream and central nervous system (invasive listeriosis), high dose antimicrobial treatment must be administered intravenously in a hospital environment (6).
Penicillin, amoxicillin or ampicillin is most commonly given, with the addition of gentamicin for individuals who have compromised immune systems (7). For individuals with an allergy to penicillin, there are alternative treatment options including vancomycin, fluroquinolone and sulfamethoxazole (8). The requirements of antibiotics used to treat listeriosis are slightly different than normal as they must penetrate host cells, distribute within the cells and remain stable within the intracellular environment (9).
The first-line treatment option of choice is usually ampicillin. It has been shown to be particularly efficacious when used to treat pregnant women, significantly improving neonatal outcomes (9). Because the penicillin group of medicines are bacteriostatic (they inhibit the growth or multiplication of bacteria but do not necessarily eradicate them), combination therapies are also increasingly common to bring bacterium under control.
The combined use of ampicillin and gentamicin has been evidenced to be clinically effective in a range of patients, particularly those over the age of 50 (10). L. monocytogenes have also been shown to have a low resistance to the recommended second line treatments of vancomycin, fluroquinolone and sulfamethoxazole (11).
Cephalosporins – drugs that kill bacteria directly – are no longer used as the listeria bacterium has been evidenced to not respond to this family of drugs (12).
Clinical guidelines tend to suggest that treatment should continue for two weeks in the case of invasive listeriosis, and up to six weeks for more severe forms of the disease. This is in response to a number of studies that suggest recurrences of infection after treatment in a number of immunocompromised patients (13).
Although clinical guidelines tend to be of the opinion that there is very little difference between the available antimicrobial treatment options, there is a gap in the literature that compares the number of different medicines and treatment options for listeriosis. As such, this assertion is more likely to be based on expert opinion and clinical experience than a formal evidence base.
The common denominator in all available evidence is that prompt, timely treatment of the disease is crucial to patient recovery and improves the chance of a positive clinical outcome. This is because of the severity of the disease and the high associated mortality if left untreated for any significant period of time (14).
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