Drug-resistant bacteria. Coloured scanning electron micrograph (SEM) of drug-resistant bacteria (green) of the Enterococcus genus. This particular Enterococcus strain is resistant to vancomycin, a drug normally used to target drug- resistant bacteria. As such, these bacteria can cause fatal infections. Such 'superbugs' are often found thriving in hospitals, and are a major problem. Some Enterococcus bacteria are found as part of the normal bacterial population in human intestines. They can be pathogenic, and cause food poisoning and also post-surgical skin infections. They are spherical bacteria (cocci).