Epidemiology of anaerobic infections.
The clinical importance of the anaerobic organisms, especially the toxicogenic Clostridia and some of the nonsporulating anaerobes, has been recognized for some time. Only within the last 20 years, however, owing to improved methodology, have gram-negative anaerobic bacilli, anaerobic cocci, and streptococci been commonly recognized and encountered in clinical infections. Today, anaerobic organisms are common isolates from infections involving intra-abdominal sites, the female genital tract, soft tissue, and oral areas and from major infections involving the lung, brain, and head and neck. Most of these infections are polymicrobial--involving both anaerobic and facultative or aerobic organisms. In some instances, it is difficult to ascertain what role is played by what organisms. No doubt, synergism is present in many cases. Because anaerobes are prevalent normal flora of the body, almost all anaerobic infections are of endogenous origin. Many of these anaerobes are opportunists; given the appropriate set of conditions, they will penetrate tissue and cause infection. Many have been associated with wound infection subsequent to bowel surgery or trauma, tubo-ovarian abscess, perirectal abscess, subphrenic abscess, postabortal sepsis, appendicitis, and many other infectious conditions. This article reviews the distribution of anaerobes in infected hospitalized patients and their relation to infection over a 5-year period.