The myth of Brucella L-forms and possible involvement of Brucella penicillin binding proteins (PBPs) in pathogenicity.
Brucella spp. L-forms have been proposed to be stationary phase organisms in the evolution of new variants and enduring entities in the host in complicated cases of brucellosis and during latent brucellosis. In vitro formation of Brucella L-forms has been achieved by treating the cells with sub-lethal doses of penicillin. Interestingly, Brucella spp. have classified during the evolution into two groups, penicillin susceptible or penicillin resistant, yet both types grow on 20 microg/ml of methicillin. Strains proven susceptible to penicillin grew in the presence of methicillin as L-forms as demonstrated by light and electron microscopy. In addition, the B. melitensis vaccine strain Rev.1, a penicillin susceptible organism, responded to sheep serum by development of L-form-like structures unlike wild type, strain 16M. The two strains grew normally in sheep macrophages. We propose, for the first time, a model that associates Brucella pathogenicity with the structure and activity of two of their penicillin binding proteins (PBPs). According to the model, PBP1 has evolved as the major cell wall synthesizing enzyme of the genus, capable of responding to host serum growth factor(s) necessary for Brucella survival in the host. This property is associated with high avidity to beta-lactam antibiotics. PBP2 complements the activity of PBP1. New beta-lactam antibiotics and improved vaccines might be developed based on this property.
Banai
M
M
Department of Bacteriology, Kimron Veterinary Institute, PO Box 12, Bet Dagan 50250, Israel. mbana_vs@netvision.net.il
Adams
L G
LG
Frey
M
M
Pugh
R
R
Ficht
T A
TA
D000818:Animals; D001426:Bacterial Proteins; D002002:Brucella / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D017347:Brucella melitensis / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity / Q000648:ultrastructure; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D014644:Genetic Variation; D006602:Hexosyltransferases; D008264:Macrophages / Q000382:microbiology; D008712:Methicillin / Q000494:pharmacology; D002267:Muramoylpentapeptide Carboxypeptidase / Q000235:genetics / Q000378:metabolism*; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D012756:Sheep
D001426:Bacterial Proteins; D002352:Carrier Proteins; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D008712:Methicillin