Mycoplasma Diseases (PDF)

MYCOPLASMA Class Family Genus Mycoplasma Mycoplasmataceae Ureaplasma Mollicutes Acholeplasmataceae Acholeplasma Anaeroplasma Anaeroplasmatacea...

MYCOPLASMA Class Family Genus Mycoplasma Mycoplasmataceae Ureaplasma Mollicutes Acholeplasmataceae Acholeplasma Anaeroplasma Anaeroplasmataceae Asteroplasma  General characteristics ´ Smallest free-living prokaryotic microorganisms (0.3 to 0.9 μm in diameter) ´ Possess triple-layered limiting membranes but lack cell walls ´ Do not stain by the Gram method ´ Highly pleomorphic. Susceptible to desiccation and disinfectants ´ Microcolonies have a ‘fried-egg’ appearance ´ Most are facultative anaerobes and grow optimally in an atmosphere of 5 to 10% CO2. ´ Most are host-specific ´ Mycoplasma and Ureaplasma contain species of veterinary importance  Usual habitat ´Mycoplasmas are found on mucosal surfaces of the conjunctiva, nasal cavity, oropharynx and intestinal and genital tracts of animals and humans. Mycoplasma species of Veterinary significance and disease conditions Mycoplasma species Hosts Disease conditions M. mycoides subsp. mycoides Cattle Contagious bovine (small colony type) pleuropneumonia (CBPP) M. bovis Cattle Mastitis, pneumonia, arthritis M. agalactiae Sheep, goats Contagious agalactia M. capricolum subsp. Goats Contagious caprine capripneumoniae pleuropneumonia (CCPP) M. capricolum subsp. Sheep, Goats Septicaemia, mastitis, polyarthritis, capricolum pneumonia M. mycoides subsp. capri Sheep, goats Septicaemia, mastitis, arthritis, includes strains previously pleuropneumonia classified as M. mycoides subsp. mycoides (large colony type) M. hyopneumoniae Pigs Enzootic pneumonia M. hyorhinis Pigs Polyserositis M. gallisepticum Chickens Chronic respiratory disease Turkeys Infectious sinusitis M. synoviae Chickens, turkeys Infectious synovitis M. meleagridis Turkeys Airsacculitis, bone deformities, reduced hatchability  Contagious bovine pleuropneumonia Contagious bovine pleuropneumonia (CBPP) is a severe contagious disease of cattle. It is caused by M. mycoides subsp. mycoides (small colony type), a member of the ‘mycoides cluster’. Contagious bovine pleuropneumonia is endemic in central Africa, the Middle East and Asia. Sporadic outbreaks, usually of a less severe form of the disease, have recently occurred in Portugal, France, Italy and Spain. The main method of transmission is by aerosols. Transmission of the disease requires close contact with clinically affected animals or asymptomatic carriers.  Clinical signs and pathology Clinical signs in the acute form of CBPP include sudden onset of high fever, anorexia, depression, drop in milk yield, accelerated respiration and coughing. Animals adopt a characteristic stance with the head and neck extended and elbows abducted. Expiratory grunting and mucopurulent nasal discharge may be present. Death can occur 1 to 3 weeks after the onset of clinical signs. Arthritis, synovitis and endocarditis may be present in affected calves. At post-mortem, the pneumonic lungs have a marbled appearance. Grey and red consolidated lobules alternate irregularly with pink emphysematous lobules and the interlobular septa are distended and oedematous. There may be abundant serofibrinous exudate in the pleural cavity. In chronic cases, fibrous encapsulation of necrotic foci is commonly found.  Contagious agalactia of sheep and goats This severe febrile disease of sheep and goats, caused by M. agalactiae, is prevalent in parts of Europe, northern Africa and parts of Asia. It usually becomes evident immediately after parturition and is characterized by mastitis, arthritis and conjunctivitis. Pregnant animals may abort and the disease can be fatal in young animals due to pneumonic complications. The organism is shed in milk and may remain localized in the supramammary lymph nodes between lactations.  Contagious caprine pleuropneumonia Contagious caprine pleuropneumonia (CCPP), caused by M. capricolum subsp. capripneumoniae (formerly Mycoplasma strain F38), is present in northern and eastern Africa and in Turkey. The disease is characterized by pneumonia, fibrinous pleurisy, profuse pleural exudate and a marbled appearance on the cut surface of affected lungs. Although similar in many respects to contagious bovine pleuropneumonia (CBPP), well developed necrotic areas in the lungs in chronic CCPP are rare. The disease is highly contagious and is transmitted by aerosols. Nomadic herds often carry infection to regions free of the disease. Pleuropneumonia in goats can occasionally be caused by M. mycoides subspecies capri.  Enzootic pneumonia of pigs This economically important disease, caused by M. hyopneumoniae, occurs worldwide in intensively reared pigs. Poor ventilation, overcrowding and temperature fluctuations may precipitate an outbreak. Pigs of all ages are susceptible and the condition is characterized by coughing, poor growth rates and, in some cases, respiratory distress. At post-mortem, pulmonary consolidation is confined to the cranial and middle lobes with clear demarcation from normal lung tissue.  Mycoplasmal diseases of poultry Mycoplasma gallisepticum causes chronic respiratory disease in chickens and infectious sinusitis in turkeys. The organism is transmitted through infection of the embryo in the egg or by aerosols. Clinical signs are consistent with upper respiratory tract involvement in chickens. In turkeys, there is swelling of the paranasal sinuses. Reduced egg production may be evident. Diagnosis is based on isolation and identification of the pathogen and on flock testing using the serum plate agglutination test. Several PCR-based methods for the detection of the organism in clinical samples ´ Mycoplasma meleagridis may be egg-transmitted and may be present in turkey semen. Aerosol transmission is less important with this pathogen than with M. gallisepticum. The clinical features of the infection include reduced egg hatchability, airsacculitis in young poults and joint and bone deformities in growers. Confirmation requires isolation and identification of the pathogen.  Diagnostic procedures ´ Specimens for laboratory examination, ideally collected early in the course of a disease, should be kept refrigerated and delivered to a laboratory within 48 hours. Suitable samples include mucosal scrapings, tracheal exudates, aspirates, pneumonic tissue, mastitic milk and fluids from joints or body cavities. Swabs from lesions or suspect material should be placed in mycoplasmal transport media for transfer to the laboratory. ´ Inoculated mycoplasmal medium is incubated aerobically or in 5 to 10% CO2, in a humid atmosphere at 37°C for up to 14 days. Fluid samples can be inoculated directly on to agar or into broth media. Tissue specimens such as lung should be freshly sampled and a cut surface moved across the surface of a solid medium. Alternatively, the tissue can be homogenized in broth and samples of the suspension used for inoculation of liquid or solid media. q Mycoplasma species and Ureaplasma species require enriched media containing animal protein, a sterol component and a source of DNA or adenine dinucleotide. Commercially available mycoplasma agar or broth media (often heart infusions) are supplemented with 20% horse serum and yeast extract providing amino acids and vitamins. In addition, penicillin is used to inhibit Gram-positive bacteria, and thallous acetate is incorporated to inhibit Gram-negative bacteria and fungi. Media are buffered at pH 7.3 to 7.8 for Mycoplasma species and at pH 6.0 to 6.5 for Ureaplasma species. For culturing ureaplasmas, urea is added to the medium and thallous acetate, which is toxic for these organisms, is omitted. Acholeplasma species occasionally grow as contaminants on mycoplasma media. ´ Colonial morphology: – When examined microscopically at low magnification, unstained microcolonies of Mycoplasma species are 0.1 to 0.6 mm in diameter and have a ‘fried-egg’ appearance. Some species produce colonies up to 1.5 mm in diameter which can be seen without magnification. – Colonies of Ureaplasma species are usually 0.02 to 0.06 mm in diameter and often lack a typical peripheral zone. Because their colonies are tiny, these organisms were formerly referred to as T- mycoplasmas. – Dienes stain facilitates recognition of microcolonies by staining the central zone dark blue and the peripheral zone a lighter blue. ´Identification criteria for isolates: – ‘Fried-egg’ microcolonies – Microcolony size – Cholesterol requirement for growth (digitonin sensitivity test) – Biochemical profile including urease production ´Fluorescent antibody technique on microcolonies ´Serological tests: - Complement fixation tests - ELISA, Rapid plate agglutination tests, Haemagglutination- inhibition tests