Fernandez, R.A., and Ciccarelli, A.S.
Cát. Microbiología, FCMédicas, UNCuyo, CC33, 5500 Mendoza, Argentina.

Although food botulism (FB) in Argentina is quoted by 1911, the first documented outbreak was recorded in 1922. Up to 1950, its diagnosis was made only on clinical grounds. In 1957, for the first time, type A botulinal toxin was recognized in samples of the suspected food and a strain of Clostridium botulinum type A was isolated from the feces of one of the patients. Infant botulism (IB) was recognized in 1976 and has been mostly recorded in USA. The first case in Argentina was described in 1982 and more than 145 cases have been reported so far. It is possible that many cases are still occurring unnoticed. Pediatricians having more experience with IB and improved access to diagnosis laboratories may lead to better identification of future cases. Wound botulism (WB) is a rare disease. Between 1943, when the syndrome was first recognized, and 1990, only 47 cases were reported in USA. Although in Argentina is quoted in 1992, only in 1995 the first and unique strain was isolated from a wound of a fatal case. The serologic types identified in FB were: A, B, E, F and Af, and A in IB and WB.

Serum, wound, fecal and food specimens should be tested for botulinal toxin, and the fecal, wound and food samples are also cultured for toxigenic organism for the laboratory diagnosis. In IB, the toxin was found in the serum of 28/46 (60,9%) cases of Mendoza. This is interesting in view of the negative results usually reported in USA.

Reliable typing of botulinal neurotoxins (BoNT) in foods, clinical samples or in mixed cultures, can only be achieved when BoNT belongs to the known serotype and the toxin titer is preferably above 4000 LD₅₀/ml. On the contrary, the isolation of the bacterium, its purification and high toxin yield cultures are required. The routine neutralization test (NT) running a nonquantitative one-dose NT (10 to 20 LD₅₀ versus 1 IU of antitoxin) can be the source of errors when establishing the identity of a given BoNT and should be considered, at best, as a preliminary typing only. NT must be performed at not less than three 10-fold separated doses of toxin (e.g. 20, 200, and 2000 LD₅₀). It is required because of (1) the existence of subtypes (one of the serotype may be present in 1 to 10%), (2) the sharing of epitopes between some serotypes, and (3) the occurrence of serologycal variants. Moreover the three basic properties of working antitoxins (specificity, potency and avidity) must be known. The efficiency index, that expresses the avidity of antitoxins, is of utmost importance for recognizing the antigenic identity of a given BoNT.