Melioidosis is a bacterial infection caused by Whitmore’s bacillus and occurs with the formation of multiple septic-necrotic foci in internal organs and tissues. The clinical course is characterized by fever with chills, cough with purulent sputum, chest pain, lymphadenitis, vomiting, diarrhea. Typically, the development of purulent-inflammatory processes in various organs (lung abscesses, pleural empyema, arthritis, pyelonephritis, osteomyelitis, etc.). Bacteriological examination of blood, urine, sputum, pus, serological methods allows to confirm the diagnosis of melioidosis. For etiotropic therapy, antibiotics of the tetracycline series, levomycetin, sulfonamides are used.
General information
Melioidosis (false sap, pneumoenteritis, pseudocholera, Whitmore’s disease) is an infectious disease from the group of sapronoses characterized by acute or chronic septicopiemia. Disease is recorded in Southeast Asia, Indonesia, Australia, West and East Africa, Central and South America. Imported cases occur in Europe and the USA. In endemic regions, antibodies to the causative agent of melioidosis are found in 7-10% of the local population, which indicates a wide spread of infection. Melioidosis can occur in latent, septic, pulmonary and recurrent forms. Without timely etiotropic treatment, the mortality from the disease is close to 100%.
Causes
The infection is caused by the gram-negative bacillus Burkholderia pseudomallei (Pseudomonas pseudomallei, Whitmore’s bacillus), which in its morphological and cultural properties is close to the causative agent of sap. The bacterium is a facultative aerobic; mobile due to the presence of a flagellar apparatus; has a length of 2-6 microns and a width of 0.5-1 microns. In the external environment (water, moist soil, rotting materials), the causative agent of melioidosis is able to maintain its pathogenicity for a long time, but it quickly dies when heated and exposed to disinfectants.
The main natural reservoirs of melioidosis bacillus are water and soil contaminated with secretions of infected animals. In natural conditions, carriers of the bacillus are domestic and wild animals (cats, dogs, pigs, cows, horses, goats, sheep, rats, kangaroos, rabbits), among which sporadic cases of melioidosis infection are also noted. A person can become infected with melioidosis by alimentary means when using infected water and food; by aerogenic (air-dust) by inhaling bacilli with dust particles; by contact in case of contact with contaminated material on damaged skin. There are individual cases of sexual transmission of the pathogen from a patient with melioidosis prostatitis, as well as nosocomial infection of medical staff when caring for patients with melioidosis. The maximum increase in morbidity is recorded in agricultural areas during the rainy season, as well as during periods of wars and natural disasters. Melioidosis usually occurs in the form of group outbreaks and sporadic cases. 98% of the cases are men.
Having overcome the entrance gate, the causative agent of melioidosis multiplies in the regional lymph nodes. The septic form of infection is accompanied by the release of bacteria into the blood and hematogenic spread throughout the body with the formation of multiple granulomas with caseous necrosis and abscesses. In most cases, purulent foci occur in the lungs; in severe cases – in almost all organs and tissues (skin, subcutaneous tissue, lymph nodes, bones, liver, kidneys, spleen, brain and meninges). Septic variant of melioidosis develops in weakened patients, patients with chronic hepatitis, diabetes mellitus, tuberculosis, alcoholism, drug addicts (the outdated name of the disease is “septicemia of morphinists”). Individuals with good immune reactivity usually have a pulmonary form of melioidosis, which is characterized only by lung abscesses. Cases of latent infection are described. Postinfectious immunity is long-lasting, possibly lifelong.
Symptoms
The duration of the incubation period in melioidosis can range from 2 to 12-24 days (sometimes up to several months). There are latent, septic (lightning-fast, acute, subacute, chronic), pulmonary (infiltrative, abscessing) and recurrent forms of melioidosis. With a latent course, there are no obvious symptoms of the disease; the infection is detected retrospectively, during a serological examination of the local population or persons who have returned from endemic regions. In case of activation of latent infection, recurrent melioidosis may develop, proceeding according to the septic or pulmonary variant.
The septic form of melioidosis can have a lightning-fast, acute, subacute and chronic course. With the lightning-fast variant, the symptoms develop rapidly: in a matter of hours, the temperature progresses to 41 ° C, vomiting, profuse diarrhea, exicosis occurs. Shortness of breath, cardiovascular insufficiency increases; hepatosplenomegaly and jaundice develop. Against the background of severe intoxication, meningeal symptoms, impaired consciousness, arousal or, conversely, central nervous system depression, delirium may occur. The death of the patient from infectious and toxic shock occurs on the second day. The course of the lightning-fast form resembles a cholera clinic or a septic form of plague.
Acute melioidosis manifests with high fever and tremendous chills. Against this background, severe headaches, joint and muscle pain, vomiting, diarrheal syndrome are bothering. At the same time, there is a cough with mucopurulent sputum, chest pain, hemoptysis, cervical and axillary lymphadenitis, pneumonia often occurs. On the 5th-6th day, erythema, pustules or hemorrhagic vesicles appear on the skin. In general, the clinical picture of acute melioidosis corresponds to a severe course of sepsis; the duration of the acute phase is 10-15 days.
The subacute course of melioidosis is characterized by a picture of septicopyemia with the formation of abscesses in the lungs, the development of pleural empyema, purulent pericarditis, purulent arthritis, osteomyelitis, peritonitis, pyelonephritis, cystitis, meningoencephalitis. Intoxication and febrile syndromes are moderately pronounced. Without etiotropic therapy, patients with a subacute form of melioidosis die within a month. Chronic melioidosis can last for several years with periodic exacerbations and remissions. This form is characterized by normal or subfebrile temperature, abscesses in subcutaneous tissue with long-term non-healing fistula passages, abscesses of internal organs. The death of patients occurs from cachexia, amyloidosis, secondary bacterial infection.
The pulmonary form of melioidosis occurs in the form of abscessing pneumonia or purulent pleurisy. At the same time, intermittent fever with chills and sweats, cough with thick greenish yellow sputum, chest pain, weight loss are noted. On the lung x-ray, large cavities in the upper lobes are found, resembling a picture of pulmonary tuberculosis.
Diagnosis and treatment
Outside of epidemic foci, the diagnosis of melioidosis is difficult. This is due to the polymorphism of clinical manifestations, low alertness of specialists (infectious disease specialists, pulmonologists, surgeons, etc.) regarding possible imported cases of melioidosis. Therefore, patients with unclear fever and septicopyemia should always find out information about staying in areas endemic for melioidosis. Laboratory confirmation of the diagnosis is carried out by bacteriological seeding of blood, urine, sputum, exudates, abscess contents, etc. on nutrient media. Luminescent microscopy is used for rapid diagnostics and rapid identification of the pathogen. Of the serological methods, RSC and RNGA have the greatest value. It is possible to conduct a biological test – in this case, the pathogens of melioidosis are found in the peritoneal exudate in infected laboratory animals. As part of the differential diagnostic search, glanders, plague, cholera, smallpox, typhoid fever, sepsis, tertiary syphilis, tuberculosis, systemic mycoses, dysentery, liver abscesses are excluded.
Complex treatment of melioidosis consists of etiotropic antibacterial therapy, pathogenetic and symptomatic treatment and surgical drainage of abscesses. Antibiotic therapy is carried out for a long time (1-2 months or longer). The greatest specific antimicrobial activity was shown by chloramphenicol, tetracyclines, cephalosporins, sulfonamides of prolonged action, etc. In the septic form of melioidosis, several antibacterial drugs are prescribed simultaneously; antibiotics are administered parenterally, in large doses (3-4 g per day). If necessary, drainage of the pleural cavity, opening of soft tissue abscesses, percutaneous or open drainage of abscesses of internal organs is carried out.
Prognosis and prevention
Without treatment, mortality in melioidosis is 95-100%. With full-fledged antibiotic therapy, the disease is curable, but in about 20% of cases, distant relapses occur. Prevention of melioidosis consists in ensuring the protection of water supply sources and food from rodents, carrying out deratization measures, treating or slaughtering infected pets, increasing the general hygienic culture of the population in areas unfavorable for melioidosis. When melioidosis is detected, patients are isolated, all their secretions are subject to disinfection; convalescents are monitored for a long time. Specific prevention of melioidosis has not been developed at the moment.