Enterobacter cloacae. Coloured Scanning Electron Micrograph (SEM) of a cluster of the bacteria Enterobacter cloacae. These are rod-shaped Gram- negative bacilli bacteria. Members of the genus Enterobacter exist in water, soil, sewage and the intestinal and urinary tracts of humans and animals. Enterobacter cloacae may be the cause of urinary tract and respiratory tract infections in hospital patients with lowered immunity; the bacteria may also infect wounds on the skin. Usually treated with penicillin, these bacteria often show a resistance to multiple antibiotics. Magnification: x4600 at 6x6cm size.