Synergistic effect of human lysozyme plus ampicillin or beta-lysin on the killing of Listeria monocytogenes

J Infect Dis. 1991 Mar;163(3):574-8. doi: 10.1093/infdis/163.3.574.


Although ampicillin is often only bacteriostatic for Listeria monocytogenes in vitro, serum from ampicillin-treated patients was bactericidal. The bactericidal effect of serum was partly removed by bentonite, Seitz-filtration, and addition of FeCl3, suggesting it is mediated by lysozyme and beta-lysin. Partly purified human beta-lysin plus purified human lysozyme or either protein plus ampicillin were bactericidal for L. monocytogenes. Hen egg white lysozyme was not active. Lysozyme and beta-lysin were not synergistic with tetracycline, trimethoprim/sulfamethoxazole, or chloramphenicol. Thus, lysozyme and beta-lysin may play a role in the natural resistance to L. monocytogenes, and these serum proteins could contribute to the effectiveness of ampicillin in vivo.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Ampicillin / pharmacology*
  • Antimicrobial Cationic Peptides*
  • Blood Proteins
  • Drug Synergism
  • Listeria monocytogenes / drug effects*
  • Microbial Sensitivity Tests
  • Muramidase / pharmacology*
  • Proteins / isolation & purification
  • Proteins / pharmacology*


  • Antimicrobial Cationic Peptides
  • Blood Proteins
  • Proteins
  • beta lysin, human
  • Ampicillin
  • Muramidase