NAME: Aeromonas hydrophila
SYNONYM OR CROSS REFERENCE: Septicemia, Gastroenteritis Footnote 1.
CHARACTERISTICS: A. hydrophila are Gram-negative, rod-shaped facultative anaerobes Footnote 2, ranging in size from 0.3-1.0 µm wide by 1.0-3.5 µm long Footnote 1. They are motile by a single polar flagellum Footnote 1. The bacteria can produce heat-labile enterotoxins, which can be associated with haemolysin and cytotoxin production Footnote 3.
PATHOGENICITY/TOXICITY: Infection with Aeromonas hydrophila can result in gastrointestinal or non-gastrointestinal complications. Symptoms of gastrointestinal infection range from watery diarrhea to dysenteric or bloody diarrhea. Chronic infection is also possible Footnote 1. Non-gastrointestinal complications that may arise subsequent to A. hydrophila infection include hemolytic syndrome and kidney disease, cellulitis, wound and soft-tissue infection, meningitis, bacteremia and septicemia Footnote 4, Footnote 5, ocular infections, pneumonia and respiratory tract infections Footnote 6, urinary tract infection in neonates Footnote 7, osteomyelitis, peritonitis and acute cholecystitis. Severe infection can result from non resolved intermittent diarrhea, which can occur months after the initial infection Footnote 1, Footnote 2, Footnote 8. A. hydrophila can cause disease in aquatic animals, such as red leg disease in frogs which is caused by endotoxin and haemolysin produced by the bacteria and can be fatal Footnote 8, Footnote 9.
EPIDEMIOLOGY: Worldwide – Aeromonas spp. are inhabitants of aquatic ecosystems and are found in most parts of the world Footnote 1. Although the role of Aeromonas hydrophila as a causative agent of human disease is controversial, some estimated that they may cause 13 % of gastroenteritis cases in United States Footnote 10. Some jurisdictions may not identify these organisms as pathogens.
Aeromonas spp. are commonly found in ground water; drinking water at treatment plants, distribution systems, and reservoirs; and in clean and polluted lakes and rivers Footnote 1. The bacteria are found in about 1% - 27 % of drinking water Footnote 11. Aeromonas hydrophila can be found in fresh produce, meat, and dairy products. The risk of infection from oral ingestion of Aeromonas spp. is 7.3/billion for low exposure. Aeromonas spp. can also be found in soil.
INFECTIOUS DOSE: The infectious dose for humans and animals is greater than 10 10 organisms Footnote 11.
MODE OF TRANSMISSION: Infection is spread via fecal-oral transmission during direct ingestion or drinking of contaminated water or foods Footnote 1, Footnote 11, Footnote 14. Infection can also be transmitted by eating contaminated meat, dairy, shrimp, or fish Footnote 1.
INCUBATION PERIOD: The reported incubation period for Aeromonas-associated diarrhea is 1 to 2 days Footnote 15. Aeromonas’ infections contracted via recreational sporting activities, such as swimming occur as early as 24h post exposure Footnote 15. Cellulitis is the most frequent soft tissue infection and is usually accompanied by systemic signs developing within 8 to 48 h Footnote 17. The length of time from initial A. hydrophila infection to bacteremia ranges from 1 to 38 days Footnote 16.
COMMUNICABILITY: It can be transferred from human-to-human by contact with infected wounds, feces or blood Footnote 18. The pathogen can also be transferred during sports; especially when played in muddy environments involving transfer of infected soil.
RESERVOIR: Free living, water is the main reservoir Footnote 1. It can also be found in mud, water, fresh produce, meat (beef, poultry, pork, fish, shellfish, and shrimp) and dairy products Footnote 18.
DRUG SUSCEPTIBILTIY: Sensitivity has been confirmed for fluoroquinolones (ciproflaxin) Footnote 19, aminoglycosides (except streptomycin), tetracycline Footnote 20, chloramphenicol Footnote 21, carbapenems Footnote 22, polymyxin, streptomycin, gentamicin Footnote 23, and trimethoprim-sulfamethoxazole.
SUSCEPTIBILITY TO DISINFECTANTS: Susceptibility has been shown for 1% sodium hypochlorite, 2% glutaraldehyde, 70% ethanol, iodines, phenolics, and formaldehyde Footnote 24. It is also sensitive to silver in water Footnote 25 and free chlorine Footnote 26.
PHYSCIAL INACTIVATION: Exposure to temperatures of 62 oC or greater for more that a few minutes is lethal to A. hydrophila. The bacteria can be inactivated by moist heat (121°C for 15 min - 30 min) and dry heat (160-170°C for 1-2 hours) Footnote 27-Footnote 29. The bacteria can also be inactivated by ultrasonic waves delivered under high pressure (200 KPa) and elevated temperatures (40 °C) Footnote 29. Simultaneous sonication at temperature higher than 70°C and 0.5 MPa is also effective Footnote 30.
SURVIVAL OUTSIDE HOST: Aeromonas hydrophila can survive in large volumes of open water, ground water, soil, as well as polluted lakes and rivers Footnote 1.
SURVEILLANCE: Monitor for symptoms. The bacteria can be detected by PCR Footnote 10. Aeromonas spp. samples can be isolated and confirmed on ampicillin dextrin agar forming yellow colour colonies Footnote 31. Confirmation by laboratory tests can be performed by oxidase test (positive), triple sugar iron agar (glucose fermenting), or Biolog detection methods Footnote 1, Footnote 31.
FIRST AID TREATMENT: Administration of antibiotics such as ciprofloxacin, co-trimoxazole, Gentamicin, or Amikacin Footnote 1. Intravenous fluid replacement in combination with oral antibiotics is effective in lessening infection symptoms Footnote 32.
LABORATORY-ACQUIRED INFECTIONS: None reported to date.
SOURCES/SPECIMENS: The bacteria have been isolated from feces, sputum, urine, bile, pus, surgical wounds, medicinal leeches, normal flora, spleen, pleural fluid, placenta, skin lesion, throat, gall bladder, hospital water supplies, dialysis fluids, and blood plasma products Footnote 14, Footnote 33, Footnote 34.
RISK GROUP CLASSIFICATION: Risk Group 2 Footnote 35.
CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures Footnote 36.
PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes Footnote 36.
OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC). The use of needles, syringes, and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activities Footnote 36.
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply an appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up Footnote 36.
DISPOSAL: Decontaminate all wastes that contain or have come in contact with the infectious organism before disposing by autoclave, chemical disinfection, gamma irradiation, or incineration Footnote 36.
STORAGE: The infectious agent should be stored in leak-proof containers that are appropriately labeled Footnote 36.
REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: December 2011
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Public Health Agency of Canada, 2011