Antimicrobial Susceptibility of 260 Clostridium botulinum Type A, B, Ba, and Bf Strains and a Neurotoxigenic Clostridium baratii Type F Strain Isolated from California Infant Botulism Patients.

Infant botulism is an infectious intestinal toxemia that results from colonization of the infant large bowel by Clostridium botulinum (or rarely, by neurotoxigenic Clostridium baratii or Clostridium butyricum), with subsequent intraintestinal production and absorption of botulinum neurotoxin that then produces flaccid paralysis. The disease is often initially misdiagnosed as suspected sepsis or meningitis, diagnoses that require prompt empirical antimicrobial therapy. Antibiotics may also be needed to treat infectious complications of infant botulism, such as pneumonia or urinary tract infection. Clinical evidence suggests (see case report below) that broad-spectrum antibiotics that are eliminated by biliary excretion may cause progression of the patient's paralysis by lysing C. botulinum vegetative cells in the large bowel lumen, thereby increasing the amount of botulinum neurotoxin available for absorption. The purpose of this antimicrobial susceptibility study was to identify an antimicrobial agent with little or no activity against C. botulinum that could be used to treat infant botulism patients initially diagnosed with suspected sepsis or meningitis, or who acquired secondary infections, without lysing C. botulinum Testing of 12 antimicrobial agents indicated that almost all California infant botulism patient isolates are susceptible to most clinically utilized antibiotics and are also susceptible to newer antibiotics not previously tested against large numbers of C. botulinum patient isolates. No antibiotic with little or no activity against C. botulinum was identified. These findings reinforce the importance of promptly treating infant botulism patients with human botulism immune globulin (BIG-IV [BabyBIG]).