The Soil Is the Usual Source of the Clostridia in Exogenous Infection
Exogenous Infection Wounds in which anoxic conditions prevail as a result of ischemia or crushed muscle. Battle wounds of World Wars I and II supplied plentiful case material for study; gas gangrene occurred in approximately 10 percent of World War I wounds and in 1 percent of those that occurred in World War II. In civilian practice the rate of gas gangrene among 188,e00 major open wounds have been estimated to be 1.8 percent. The rate of contamination or local infection of open wounds, on the other hand, amounts to 30 to 80 percent. The soil is the usual source of the clostridia in exogenous infection, the intestine or biliary tract in autogenous infection. Pathogenesis.
The factors that predispose to the invasion of muscle by the bacilli with the subsequent elaboration of exotoxins are related to lack of oxygen and lowering of the oxidation-reduction potential of the tissues. These factors are
(1) impaired local vascular supply owing to vessel trauma or pressure from foreign bodies, casts, or tourniquets;
(2) presence of metallic bodies, clothing, or dirt in the wound;
(3) presence of necrotic tissue or hemorrhage; and
(4) growth of aerobic micro-organisms in the wound.
Under these circumstances, the bacilli can multiply anaerobically and elaborate toxins, which diffuse out and damage the surrounding muscle, which in turn becomes colonized with the bacilli. Thus, the disease spreads rapidly to surrounding muscles arid gains momentum. The severe generalized toxemia remains poorly explained. Alpha toxin is not found in the blood, and it is postulated that a toxic factor that acts on certain vital centers or enzymes is produced by the interaction of clostridial toxin with infected muscle. Clinical Manifestations. The clinical picture of gas gangrene is dominated by rapidly progressive toxemia and shock. After a relatively short incubation period of one to four days, the patient suddenly exhibits restlessness and anxiety; the temperature and pulse rate begins to rise and the blood pressure to fall. He is noted to be pale and sweating.
The wound becomes painful and markedly swollen. Some hours later, after the progression of the signs and symptoms, a thin brownish exudate begins to ooze from the wound, and a small amount of crepitus may be noted in the surrounding tissues. A bronze discoloration starts at the edge of the wound and progresses outward. Blebs filled with purplish fluid may appear. An odor characterized as “mousy” or “sickly sweet” is described by many observers. By this time the patient may be anuric and in irreversible vascular collapse.
When the muscle is exposed by incision, it appears to be “cooked” or dead — it does not bleed when cut or retract when pinched. Smears from involved muscle show many large gram-positive rods and no other organisms, but very few pus-cells. Smears and cultures from the wound exudate at the surface may reveal other organisms in addition to the clostridia, especially in grossly contaminated wounds. Roentgenograms reveal the presence of gas in and around muscle bundles in the form of fern-like, lacy patterns. Untreated,
Fully developed clostridial myonecrosis is almost always fatal. Myonecrosis must be differentiated from clostridial and nonclostridial crepitant cellulitis, from anaerobic streptococcal myonecrosis, and physical and chemical causes of gas in the tissues. Clostridial cellulitis (anaerobic cellulitis, local gas gangrene, Epifascial gas gangrene, or gas-forming fasciitis) is a gas-forming infection of connective tissue mainly localized to subcutaneous areas with the spread in fascial planes, but healthy muscle is not involved. It arises as a result of clostridial infection of tissue already necrotic from ischemia or trauma.
The onset is gradual; and toxemia, pain, and swelling are less than in gas gangrene. A large amount of gas is distributed in the form of large bubbles along the fascial planes, but not in the muscle. The incision will show that the muscle is viable, and smears from muscle tissue away from the open wound will not reveal organisms. Nonclostridial crepitant cellulitis is similar to clostridial cellulitis, except that the infection is associated with other organisms usually in a mixed flora consisting of, two or more of the following: atherogenic coliforms (E. coli, Klebsiella, Enterobacter), anaerobic streptococci, Bacteroides. and gamma streptococci.
Exogenous Infection In many cases this mixed bacterial flora in gas-forming cellulitis includes clostridia; these cases do not appear to differ in prognosis from those in which clostridia are ab-sent. Anaerobic streptococcal myonecrosis was de-scribed by MacLennan in infected war wounds from the Middle East in 1948, but there have been few reports since then. Other organisms, especially group A streptococci and Staph. aureus was always found with the primary agent, and 3 of 19 patients had anaerobic streptococcal bacteremia. Simple contamination of wounds with clostridia is not uncommon.
The organisms, usually in association with a mixed flora, exist as saprophytes on necrotic tissue and debris and do not invade further. Clostridia may also be found in localized collections of purulent material in wounds, or a collection of foul-smelling brownish fluid known as a “gas abscess” or a “Welch abscess.” Drainage will usually suffice to bring these conditions under control. There is not always a clear-cut distinction among the various pathologic states described above, nor is it clear how often one can recognize an orderly progression in the severity of clostridial invasion from simple contamination to full-blown myonecrosis. Diagnosis.
The diagnosis of gas gangrene is essentially a clinical one. Upon the first suspicion of the disease, dressings and casts must be removed and the wound or suspected area thoroughly inspected. Roentgenograms may help to show the fine bubbles of gas distributed in and around muscle bundles. The incision should be made into the muscle so that the characteristic appearance may be appreciated. At the same time, a specimen of muscle may be examined by Gram stain and by anaerobic cultural techniques. Slides may also be made for staining by the fluorescent antibody