Aeromonas associated zoonotic disease

Aeromonas causes gastrointestinal infections and extra intestinal infections such as cellulitis, wound infectiopn, peritonitis, endocarditis, osteomyelitis, menigitis in man. It also causes opportunistic systemic disease in immunocompromised patients. Gastroenteritis typically occurs after the ingestion of contaminated water or food, whereas wound infections result from exposure to the contaminated water.

Epidemiology: There are more than 96 distinct serogroups of Aeromonas based on the presence of unique somatic antigens. In developing countries, potentially pathogenic Aeromonas sp. is very common in drinking water and in different types of foods, particularly seafood. Several food-borne and water-borne outbreaks as well nosocomial outbreaks associated with aeromonads have been reported. Motile aeromonads that are mesophilic in nature cause diseases in man. Aeromonas infection is more during summer. People with compromised immune systems and individuals suffering from leukemia, carcinoma, diabetes, hepatitis and cirrhosis or those being treated with immunosuppressive drugs or who are undergoing cancer chemotherapy may be susceptible to systemic infections caused by Aeromonas.

Clinical features: The primary clinical diseases are gastroenteritis and septicemia. Aeromonas-related gastroenteritis is generally a self-limiting watery diarrhea lasting a few days to a few weeks. Symptoms include non-bloody rice-watery diarrhoea with some patients dehydrated in severe cases. Some patients may develop fever, abdominal pain, bloody diarrhoea and vomiting. Diarrhoeic children with Aeromonas infection may have up to ten episodes of stool passages per day and diarrhoea may last from 2-10 days. Diarrhoea may also be chronic, lasting for months, particularly in the immunocompromised state.Soft tissue infections following water-related injuries are also common. Aeromonas appears to be a major pathogen for septicaemia in patients with hepatic cirrhosis and result in fatal outcome. The main clinical manifestations include fever, chills, abdominal  pain, diarrhoea and shock. Meningitis is a rare clinical entity.

Diagnosis: Isolation and identification of bacteria from stool samples, body sites, water and foods samples help in the diagnosis of the diseases. Testing for mannose- resistant hemagglutination (MRHA) may be used as one of the virulence markers for distinguishing diarrhoeic or environmental isolates. The enterotoxic potential of Aeromonas sp can also be assessed by performing a CAMP-haemolysin assay.PCR based detection of Aeromonas is done based on detection of 16S rRNA gene. Multiplex PCR has been used for detection of various virulent genes such as lip (lipase gene), ser (serine protease gene), aer (aerolysin gene), nuc (nuclease gene), dns (DNase gene), hlyA (hemolysin gene), laf (lateral flagella).

Control and prevention: Many of the Aeromonas infections are water- and food- borne. Necessary steps should be taken to prevent the transmission from water and food to human and animal. Drinking of untreated water should be avoided to prevent Aeromonas infection.