Actinomyces

Members of the genus Actinomyces are facultative anerobic, gram-positive, non acid-fast, non-spore forming, nonhaemolytic rods. All Actinomyces require rich media containing blood or serum. No growth occurs on Sabouraud’s agar at room temperature. Actinomycosis is a chronic, granulomatous, suppurative and sporadic infection of human, cattle, horse, pig, sheep, buffalo, deer and other animals. A. bovis causes Actinomycosis or lumpy jaw in cattle. The organism has not been recovered from the environmental sources and is thought to be located endogenously in the gum, teeth, tonsillar crypts, throat and gastrointestinal tract of apparently healthy animals and human. However, laceration and ulceration of the mucous membranes of mouth by sharp pieces of feed or thorns may often provide an opportunity to the organism to become potentially pathogenic. The infection is more common in young calves during the eruption of teeth and is manifested by oesteomyelitis of the bones of head, particularly the mandible and maxilla. The disease usually affects young persons 20-29 years old and shows high incidence in male agricultural workers. About 65% of the cases are of cervico-facial region and 20% of abdominal. Rarely, actinomycosis of lung, liver, heart, brain, spleen, kidney, testis and skin may occur because of blood- borne metastatic lesions. Sometimes, pyogenic bacteria may produce secondary infection and thus complicate the case. The pathogens invade the tissue and grow in the form of colonies which are white and semi-transparent in the beginning and later turn to dark brown or yellow or to sulphur granule. The granules when examined under microscope reveal gram-positive central mass with surrounding gram-negative clubs. The clubs are more commonly observed in animal actinomycosis than human.

Symptoms: Actinomyces bovis causes lumpy jaw of cattle. The affected animals show one or more painless, hard and immovable swellings on the maxilla and mandible. Later the swelling becomes painful and breaks through the skin discharging sticky honey-like fluid which shows hard, whitish yellow granules. Due to excessive swelling, animal feels difficulty in respiration as well as mastication. Sometimes the alimentary tract is involved with the interference in ruminal movement and ingestion as a result of which the animal exhibits chronic tympany and diarrhoea. Very occasionally the haematogenous spread may occur from the primary lesion involving lung, brain and  testis. Actinomycosis of skin and udder is sometimes observed in pigs. Mastitis in sows is sometimes associated with Actinomyces. Poll evil and fistulous withers in horses contain Actinomyces.

Diagnosis: Clinically, the disease resembles abscesses on cheek and throat region, with foreign bodies in the mouth and feed jammed between teeth and cheek. Needle puncture reveals the presence and type of pus. The demonstration of typical “sulphur granules”-yellowish particles in tissues or pus is sufficient for diagnosis. Smears made from sulphur granules should be examined for the presence of Gram-positive thin filaments and Gram-negative club like structures (composed of mineral and the detritus of inflammatory and immune response) called rosettes. The granules after washing with sterile distilled water should be cultured on brain heart infusion (BHI) agar or thiogylocate broth to isolate the aetiological agent.

Treatment and prevention: A. bovis is sensitive to penicillin, streptomycin, tetracyclines, cephalosporins, lincomycin and sulfonamides. Local lesions may be treated with the iodine ointment. Lugol‘s iodine or streptomycin (5 g dissolved in 1 ml of distilled water) may be infiltrated into the hard swelling. If the swelling still persists as hard, the same may be removed by surgery. The wound should be dressed daily with tincture of iodine. Potassium iodide 6-10 g orally/ day for 5-7 days, and sodium iodide 2.2 g/ 30 kg body weight as 10 % solution intravenously in 2 doses, with 15 days interval may be useful both in osteomyelitis and systemic actinomycosis. Treatment with sulphanilamide, sulphapyridine, sulphathiazole 2.2 g/ 15 kg body weight or penicillin 0.3-0.5 million IU/ animal intramuscularly for 4-7 days is effective in animals and human. Since the infection occurs by endogenous route, predisposing environmental factors which cause oral laceration should be eliminated.