Oxytetracycline is also used to treat acne, due to its activity against the bacteria on the skin that influence the development of acne ("Cutibacterium acnes"). It is used to treat flare-ups of chronic bronchitis, due to its activity against the bacteria usually responsible, "Haemophilus influenzae". Oxytetracycline may also be used to treat other rarer infections, such as those caused by a group of micro-organisms called rickettsiae ("e.g.", Rocky Mountain spotted fever). To make sure the bacteria causing an infection are susceptible to it, a tissue sample is usually taken, for example a swab from the infected area, or a urine or blood sample.