Leukemia patients at greatest risk of listeriosis
By Kerry Grens | Reuters
NEW YORK (Reuters Health) - People with certain conditions, including leukemia, other cancers and pregnancy, are at the greatest risk of getting sick from the food-borne bacterium Listeria, French researchers report in a new study.
Doctors and public health officials have known that these conditions make people more vulnerable to listeriosis, but this study is the first to rank the size of the risk for people with each condition.
The results "will help focus risk communication for the medical community," said Ramon Guevara, an epidemiologist for the County of Los Angeles Department of Public Health, who was not involved in the study.
"If you do have an outbreak you want to say who are the high-risk people," he added.
Earlier this year, 30 people died in the Unites States in an outbreak of listeriosis, spread by contaminated cantaloupe.
Deli meat, raw cheese, produce and smoked seafood are also thought to potentially harbor Listeria, but it's uncommon that people actually get sick from it.
The study looked at nearly 2,000 cases of listeriosis in France -- affecting 39 out of every 10 million people -- from 2001 to 2008.
Despite its rarity, listeriosis is still considered an important public health concern because it's relatively deadly compared to other food-borne illnesses, lead author Dr. Véronique Goulet at the Institut de Veille Sanitaire in Saint-Maurice wrote in an email to Reuters Health.
More than 400 of the 2,000 people who developed listeriosis died.
None of the cases involved an outbreak.
About one in six of the listeriosis cases in France affected pregnant women.
Among the remaining cases, 65 percent of the people involved had an underlying health condition, and 41 percent were undergoing treatment that suppressed their immune systems.
Goulet and her team determined that people with chronic lymphocytic leukemia were at the greatest risk of developing listeriosis -- more than 1,000 times higher than the general French population.
Fifty-five out of every 100,000 people with this leukemia developed listeriosis.
People with other cancers, such as myeloma, lymphoma, and esophageal and liver cancers, were also at a much higher risk of getting sick from Listeria, as were people undergoing dialysis.
Anywhere from 13 to 17 out of every 100,000 people with one of these conditions fell ill with listeriosis, according to findings published in Clinical Infectious Diseases.
Goulet pointed out that even though diabetics and the elderly also have a greater chance of developing listeriosis than the general population, the number of cases among these groups is very small.
"I would like to target recommendations for prevention to persons with hematological malignancy (blood, bone marrow and lymph cancers), especially those undergoing immunosuppressive treatment," Goulet said.
The Centers for Disease Control and Prevention advise people to wash produce before eating, including scrubbing the outside of firm fruits and vegetables such as melons and cucumbers.
In addition, keep the refrigerator colder than 40 degrees Fahrenheit, thoroughly cook meat and toss freshly-sliced deli meats after three to five days.
Depending on the level of risk, Goulet said, some people should avoid eating certain foods, but it's not necessary for everyone.
"For example, as the incidence is very low in the elderly population with no concomitant underlying disease, it is perhaps not advisable to make general recommendations such as to avoid eating deli-meat or cheeses such as feta or camembert, or smoked fish," Goulet wrote.
The cantaloupe outbreak earlier this year, which was one of the most deadly food-borne outbreaks in the United States, was traced back to unsanitary conditions at a packing plant in Colorado.
Clinical Infectious Diseases, online December 9, 2011
Listeria monocytogenes (單核球增生性李斯特菌)
l A Gram-positive coccobacillus。可引起listeriosis。
l 可在冷藏溫度(refrigeration temperatures)生長。
l 在各種動物﹑鳥類身上及土壤中。經未煮熟食物、乳酪、牛奶、coleslaw,等食物傳染。
l 潛伏期﹕3-70天﹐一般約三週
l 母子在尿液及陰道分泌液中排出細菌7-10天﹐但被感染者可能在糞便中排放細菌久達七﹑八個月。
病變﹕
l 感染孕婦及嬰兒 (經intrauterine infection=胎兒子宮內感染，或paranatal infection=經產道時感染)、或免疫不全病人(immunocompromised patient)。
l 在新生兒及成人常呈現meningoencephalitis(腦膜腦炎) and/or septicemia(敗血症)﹑在孕婦造成abortion(流產)。可能有endocarditis﹑肝臟及其他器官之granulomatous lesions(肉芽腫)或abscesses(膿瘍)﹐也可能有皮膚膿疹丘疹。正常人常只有輕微發燒。
l 母親可能無症狀﹐但新生兒可能會死產（still birth）﹑生下就有septicemia﹑或發生腦膜炎。
l 新生兒死亡率達30-50%﹐一般成人為35%﹐60歲以上者可達63%。
l 在一次由污染的牛奶引起的群突發中，經口食入大量(1011 CFU)細菌，引起腹瀉(79%)、發燒(72%)、畏寒(65%)、頭痛(65%)、肌痛(59%)、腹絞痛(55%)、噁心(47%)、嘔吐(26%)等症狀。潛伏期為20 (9~32)小時。得病率高達75%。腹瀉在天內自癒。Antibody to listeriolysin會昇高。60名受感染者中有三名得septicemia or brain abscess。
診斷﹕
l 靠血液及脊髓液之sheep blood agar細菌培養。有小的溶血圈。如先在4°C維持數日再加在培養劑則陽性率增加。
防治﹕
l 注意飲食安全衛生。動物來源之食物要經pasteurization(巴斯德低溫消毒) (dairy products=牛奶製品)﹑輻射線處理(cheese=乳酪)﹑適當地煮熟。
l 處理死亡或生病之動物要小心﹐尤其是腦炎死亡之羊。
l 病患要胃腸道隔離(enteric precautions)。
l Ampicillin (50 mg/kg, iv q6h)加 aminoglycoside﹔TMP/SMZ(TMP 5.0 mg/kg, q6h, iv)﹔high dose penicillin。可在第一劑抗生素之前開始用dexamethasone (0.4 mg/kg, q12h, 2 天)。
（採自2002年許清曉著『傳染病防治手冊』，最有用的中英文索引Index佔全書三分之一，可在藝軒圖書公司購得。以上是有關此病原的基本常識。最新資料還是要從網路或圖書館醫學雜誌取得。）
