Aeromonas hydrophila. Coloured transmission electron micrograph of thin-sectioned cells of Aeromonas hydrophila bacteria. It is a Gram- negative, rod-shaped bacillus. Aeromonas hydrophila is associated with septicaemia, pneumonia and gastroenteritis in humans. In particular it causes opportunistic infections in patients with lowered immunity, such as in cancer and liver disease. Aeromonas hydrophila has been isolated from urine, sputum, faeces and bile. It is resistant to many types of antibiotic including penicillin, but can be controlled with tetracyclins and gentamicin. Magnification: x28,800 at 6x4.5cm size.