Melioidosis is an infectious disease caused by Gram-negative bacteria, Burkholderia pseudomallei , found in soil and water. This is a public health interest in endemic areas, especially in northeastern Thailand, Vietnam, and northern Australia. It exists in both acute and chronic forms. Signs and symptoms may include pain in the chest, bones, or joints; cough; skin infections, pulmonary nodules, and pneumonia.
B. pseudomallei was previously classified as part of the genus Pseudomonas ; until 1992, it was known as Pseudomonas pseudomallei . This is phylogenetically closely related to Burkholderia mallei which causes glands, especially infection in horses, donkeys, and donkeys. The name melioidosis comes from the Greek melis (?????) which means "a distemper from a donkey" with a reversed ending which means "similar to" and -ose meaning "a condition", which is, a condition similar to a gland.
Video Melioidosis
Signs and symptoms
Acute melioidosis
In the subgroup of patients where inoculation events were recorded, the average incubation period of acute melioidosis was 9 days (range 1-21 days). Patients with latent melioidosis may be symptom-free for decades; the longest period between expected exposure and clinical presentation was 62 years. The prolonged incubation potential is recognized in US troops involved in the Vietnam War, and is referred to as the "Vietnamese time bomb". Extensive severity exists; in chronic presentation, symptoms may last for months, but fulminant infections, especially those associated with nearly drowning, may present with severe symptoms for hours.
Symptoms usually appear 2 to 4 weeks after exposure. There are four common types of infections including localized, lung, blood-borne, or disseminated throughout the body. The type and location of the infection usually determines which symptoms first appear as well as which of the more prominent symptoms.
Patients with melioidosis usually come with fever. Pain or other symptoms may lead to a clinical focus, which is found in approximately 75% of patients. These symptoms include a pleuritic cough or pleuritic chest pain suggestive of pneumonia, bone or joint pain suggestive of osteomyelitis or septic arthritis, or cellulitis. Intra-abdominal infections (including liver and/or spleen abscess, or prostate abscess) are usually not accompanied by focusing pain, and imaging of these organs using ultrasound or computed tomography should be done routinely. In one series of 214 patients, 27.6% had abscesses in the liver or spleen (95% confidence interval, 22.0% to 33.9%). B. pseudomallei abscesses may have typical "honeycomb" or "swiss cheese" architecture (hypoechoic, multiseptate, multiloculate) in CT.
Regional variation in disease presentation is apparent: a typical parotid abscess occurs in Thai children, but this presentation has been described only once in Australia. In contrast, prostate abscesses are present in up to 20% of Australian men, but are rarely described elsewhere. Encephalomyelitis syndrome is recognized in northern Australia.
Patients with melioidosis typically have risk factors for the disease, such as diabetes, thalassemia, harmful alcohol use, or kidney disease, and often provide a history of occupational or recreational exposure to mud or surface water flows. However, healthy patients, including children, may also have melioidosis.
In up to 25% of patients, no focus of infection is found and the diagnosis is usually performed on blood cultures or throat swabs. Melioidosis is said to affect any organ in the body except the heart valve (endocarditis). Although meningitis has been described secondary to a ruptured brain abscess, primary meningitis has not been described. Less common manifestations include intravascular infections, lymph node abscesses (1.2-2.2%), pyopericardium and myocarditis, mediastinal infections, and thyroid and scrotal abscesses and ocular infections.
Chronic melioidosis
Chronic melioidosis is usually defined by the duration of symptoms over two months and occurs in about 10% of patients. Clinical presentation of chronic melioidosis is a protean and includes presentations such as chronic skin infections, chronic lung nodules, and pneumonia. In particular, chronic melioidosis is very similar to tuberculosis, and is sometimes called "Vietnamese tuberculosis".
Maps Melioidosis
Diagnosis
The exact diagnosis is made by breeding the organism from a clinical sample, because the organism has never been part of a normal human flora.
The history of contact with land is definitely not obtainable, because melioidosis can be a dormant for many years before it manifests. Attention should be given to the history of travel to endemic areas in returning tourists. Some authors recommend considering the possibility of melioidosis in any febrile patient with a history of traveling to and/or living in endemic areas.
The complete screen (blood cultures, sputum cultures, urine culture, throat swabs, and culture of aspiration pussy) should be performed on all patients suspected of melioidosis (culture on blood agar and Ashdown medium). A definitive diagnosis is made by growing B. pseudomallei from any site. Throat swab is not sensitive, but 100% specific if positive, and compared with sputum culture. The sensitivity of urine culture increases if the centrifuged specimens are cultured, and any bacterial growth should be reported (not just growth above 10 4 organism/ml which is the usual cutoff). Occasionally, bone marrow culture may be positive in patients with a negative blood culture for B. pseudomallei , but this is not usually recommended. A common mistake made by a physician who is unfamiliar with melioidosis is to send the specimen from only the affected site (which is the usual procedure for most other infections) rather than sending the full screen.
Ashdown Medium, a selective medium containing gentamicin, may be necessary for cultures taken from non-sterile sites. Intermediate Burkholderia cepacia may be an alternative alternative medium useful in non-endemic areas, where Ashdown is not available. The new medium derived from Ashdown, known as the Francis medium, can help distinguish B. pseudomallei from B. cepacia and may help in the early diagnosis of melioidosis, but has not been clinically validated extensively.
Many commercial kits to identify bacteria can misidentify B. pseudomallei see Burkholderia pseudomallei for a more detailed discussion of this topic).
Serological tests for melioidosis (indirect hemagglutination) are available, but not commercially in most countries. High titer backgrounds can reduce the positive predictive value of serological tests in endemic countries. Direct immunofluorescence tests and latex agglutination, based on monoclonal antibodies, are widely used in Thailand, but are not available elsewhere. Cross reactivity with B. thailandensis is almost complete. The commercial ELISA kit for melioidosis seems to be performing well. but no ELISA test has been clinically validated as a diagnostic tool.
It is not possible to make a diagnosis only on imaging studies (X-rays and scans), but imaging is routinely done to assess the full extent of the disease. Abdominal imaging using CT scan or ultrasound is recommended routinely, because the abscess may not be clinically visible and may co-exist with the disease elsewhere. The Australian authorities recommend prostate imaging in particular because of the high incidence of prostate abscesses in northern Australian patients. Chest X-ray is also considered routine, with other clinically indicated examinations. The presence of honeycomb abscess in the liver is considered characteristic, but not diagnostic.
The differential diagnosis is broad; melioidosis can mimic many other infections, including tuberculosis.
Prevention
Person to person transmission is extraordinary; and patients with melioidosis should not be considered infectious. Laboratory workers should handle B. pseudomallei under BSL-3 isolation conditions, as laboratory-acquired melioidosis has been described.
In endemic areas, communities (paddy-rice farmers in particular) are warned to avoid contact with soil, mud and surface water if possible. Case groups have been described after floods and cyclones and may be related to exposure. Clusters of other cases are related to contamination of drinking water supplies. Risk populations include patients with diabetes mellitus, chronic renal failure, chronic lung disease, or any immune deficiency. The effectiveness of measures to reduce exposure to causative organisms has not been established. Vaccine is not yet available.
Post-exposure prophylaxis
After exposure to B. pseudomallei (especially after laboratory accidents) combined treatment with co-trimoxazole and doxycycline is recommended. Trovafloxacin and grepafloxacin have been shown to be effective in animal models.
Vaccinations
Vaccines are in the process of development, but not yet licensed. There is a fear that when the vaccine is licensed, financial constraints will make vaccination an unrealistic factor for many countries suffering from high levels of melioidosis.
Treatment
Current care
The treatment of melioidosis is divided into two stages, intravenous phase of high intensity and eradication phase to prevent recurrence.
- Intensive intravenous phase
- Intravenous Ceftazidime is the drug of choice today for the treatment of acute melioidosis and should be given 10 to 14 days after infection. Meropenem, imipenem and combinations of cefoperazone-sulbactam (Sulperazone) are also active. Amoxicillin-clavulanate intravenously (co-amoxiclav) can be used if none of the above four drugs are available, but yields lower yields. Intravenous antibiotics are administered for at least 10 to 14 days, and usually do not stop until the patient's temperature returns to normal for more than 48 hours. Even with appropriate antibiotic therapy, fever often persists for weeks or months, and patients can continue to develop new lesions even during appropriate treatment. The median fever clearance time in melioidosis is 10 days: and failure of fever to clear is not a reason to change treatment. Not infrequently patients require parenteral treatment continuously for a month or more.
- Intravenous meropenem is routinely used in Australia; the results look good and meropenem is currently being tested with ceftazidime in a Thai clinical trial.
- Theoretical reasons given for believing death may be lower in patients treated with imipenem: first, less endotoxin is released by bacteria dying during imipenem treatment, and the minimum inhibitory concentration (MIC) for imipenem is more lower than ceftazidime. However, no clinically relevant differences were found in mortality between imipenem and ceftazidime treatments. MIC meropenem is higher for B. pseudomallei than many other organisms, and haemofiltered patients will require more frequent or higher doses.
- Moxifloxacin, cefepime, tigecycline, and ertapenem appear to be ineffective in vitro . Piperacillin-sulbactam, doripenem and biapenem appear to be effective in vitro, but there is no clinical experience to recommend their use.
- Adjuvant treatment with granulocyte colony-stimulating factor or cotrimoxazole was not associated with a reduction in the death rate in trials in Thailand.
- Eradication stage
- After the treatment of acute illness, eradication (or maintenance) treatment with cotrimoxazole and doxycycline is recommended for use for 12 to 20 weeks to reduce recurrence rates. Chloramphenicol is no longer routinely recommended for this purpose. Co-amoxiclav is an alternative for patients who can not use cotrimoxazole and doxycycline (for example, pregnant women and children under the age of 12), but are not effective. Treatment of a single agent with fluoroquinolone (eg, Ciprofloxacin) or doxycycline for the oral maintenance phase is ineffective.
- In Australia, cotrimoxazole is used alone for eradication therapy, with a relapse rate that is lower than seen in Thailand; in vitro evidence also suggests cotrimoxazole and doxycycline are antagonistic, and cotrimoxazole itself may be preferred. Results from a randomized controlled trial (MERTH) support the use of cotrimoxazole alone. The study reinforces the need for adequate follow-up and good adherence to the phase of treatment eradication. The dose for cotrimoxazole is based on weight: (& lt; 40 kg: 160/800 mg every 12 hours; 40-60 kg: 240/1200 mg every 12 hours; & gt; 60 kg: 320/1600 mg every 12 hours).
Surgical treatment
Surgical drainage is usually indicated for prostate abscess and septic arthritis, may be indicated for parotid abscess, and is usually not indicated for hepatosplenic abscess. In melatonism of bacteremia that is unresponsive to intravenous antibiotic therapy, splenectomy has been tried, but only anecdotal evidence supports this practice.
Historical care
Prior to 1989, standard treatment for acute melioidosis was a combination of three drugs from chloramphenicol, cotrimoxazole and doxycycline; this regimen is associated with an 80% mortality rate and is no longer used unless no other alternative is available. All three drugs are bacteriostatic (they stop bacteria from growing, but do not kill them) and the action of cotrimoxazole causes the antagonization of chloramphenicol and doxycycline.
Prognosis
Without access to appropriate antibiotics (especially ceftazidime or meropenem), the form of sepsis from melioidosis exceeds 90% in mortality. With appropriate antibiotics, mortality rates are about 10% for uncomplicated cases but up to 80% for cases of bacteremia or severe sepsis. It seems certain that access to intensive care facilities is also important, and may at least partially explain why total deaths are 20% in Northern Australia but 40% in Northeast Thailand. The response to appropriate antibiotic treatment is slow, with the average duration of fever after treatment is 5 to 9 days.
Recurrences occur in 10 to 20% of patients, but with cotrimoxazole eradication therapy, this can be reduced by 4%. While molecular studies have determined most of the recurrence is caused by the original infecting strains, a significant proportion of recurrences (possibly up to a quarter) in endemic areas may be caused by reinfection, especially after two years. Risk factors including disease severity (patients with positive blood cultures or multifocal disease have a higher risk of recurrence), antibiotic options for eradication therapy (doxycycline monotherapy and ineffective fluoroquinolone therapy), poor adherence to eradication therapy and duration of treatment eradication less than 8 Sunday.
Potential of biological war
Interest in melioidosis has been stated because it has the potential to be developed as a biological weapon. This is classified by the US Centers for Disease Control (CDC) as a category agency B. B. pseudomallei , such as B. mallei causing the disorder, studied by the US as potential biological war agents, but never matured. The Soviet Union reportedly also experimented with B. pseudomallei as a biological war agent.
Epidemiology
Melioidosis is endemic in parts of Southeast Asia (including Thailand, Laos, Singapore, Brunei, Malaysia, Burma and Vietnam), China, Taiwan and northern Australia. Floods can increase its reach, including flooding in central Australia. Several cases have also been described in Hong Kong and Brunei India, and sporadic cases in Central and South America, the Middle East, the Pacific, and some African countries. Although only one case of melioidosis has ever been reported in Bangladesh, at least five cases have been imported into the UK from that country. The latest news report shows B. pseudomallei has been isolated from the ground in Bangladesh, but this remains to be scientifically verified. This suggests that melioidosis is endemic in Bangladesh and that underdiagnosis or lack of reporting is there. most likely due to lack of adequate laboratory facilities in affected rural areas. High isolation rates (percentage of positive soil samples) were found in eastern Saravan in Lao PDR villages away from the Mekong River, considered by researchers as the highest geometric mean concentration in the world (about 464 (25-10,850 CFU/g).
The statistical model shows that the incidence will be 165,000 cases per year by 2016 (95% confidence interval, 68,000 to 412,000), with 138,000 of which occur in East and South Asia and the Pacific. In about half of those cases, people will die. Northeast Thailand has the highest recorded incidence of melioidosis in the world (an average incidence of 12.7 cases per 100,000 people per year). In northeastern Thailand, 80% of children were positive for antibodies against B. pseudomallei at 4 years of age; The numbers are lower in other parts of the world.
Melioidosis is a disease known in animals, including cats, goats, sheep, and horses. Cattle, water buffalo, and crocodiles are considered relatively resistant to melioidosis even though they are constantly exposed to mud. The plague at the Paris Zoo in the 1970s (" L'affaire du jardin des plantes ") allegedly came from imported pandas.
B. pseudomallei is usually found in soil and surface water; a history of contact with soil or surface water, therefore, is almost unchanged in patients with melioidosis; which says, the majority of patients who have contact with the infected soil do not suffer from adverse effects. Even within an area, the distribution of pseudomallei in the soil can be very patchy, and competition with other Burkholderia species has been suggested as a possible reason. Contaminated groundwater is involved in a plague in northern Australia. Also involved are bad weather events such as tsunami floods and typhoons.
Based on genome sequencing intact, humans can play a role in moving B. pseudomallei from one place to another.
The most important risk factors for developing melioidosis are diabetes mellitus, followed by the use of harmful alcohol, chronic kidney disease, and chronic lung disease. Other risk factors include thalassemia, occupation (rice farmers), and cystic fibrosis. The mode of infection is believed to be through a break in the skin, or inhalation of the pseudomallei cell aerosol. The person-to-person spread has been described, but it is very unusual. HIV infection does not affect melioidosis.
The disease is clearly associated with increased rainfall, with the number (and severity) of cases increasing after rainfall increases.
History
Pathologist Alfred Whitmore and assistant Krishnaswami first reported the disease among beggars and morphine addicts at an autopsy in Rangoon, Myanmar today, in a report published in 1912. They differentiate it from glands, human and animal diseases similar in presentation, but caused by different micro-organisms. B. pseudomallei , also known as Whitmore's bacillus, was identified in 1917 in Kuala Lumpur. Arthur Conan Doyle may have read the 1912 report before writing a short story involving a fictitious tropical illness "tapanuli fever" in the advent of Sherlock Holmes.
Synonyms
- Pseudoglander
- Whitmore's disease (after Captain Alfred Whitmore, who first described the disease)
- Nightcliff disease gardener (Nightcliff is a suburb of Darwin, Australia where melioidosis is endemic)
- Rice disease
- Septicemia injector morphine
References
External links
- Resource Center for melioidosis
- CDC Disease Info melioidosis
- Burkholderia pseudomallei genome and related information at PATRIC, Bioinformatics Resource Center funded by NIAID
Source of the article : Wikipedia
0 Comments