title: Qualitative study of paradoxical zone phenomenon of penicillins against 17 bacterial species of clinical importance.
abstract: Using a triple agar layer technique and enzymatic inactivation of penicillin, the occurrence of a paradoxical zone phenomenon (illustrated by a typical 'target' image around the reservoir of antibiotic) was determined for several bacterial species specially chosen with regards to their taxonomic position, clinical importance and penicillin susceptibility. Among gram-positive bacteria, a paradoxical zone was obtained for approximately 43% of the strains studied here (all 10 strains of Staphylococcus aureus, all 10 strains of Streptococcus faecalis, 7 of 10 strains of group B beta-hemolytic streptococci, 1 of 10 group A strains, 3 of 10 strains of alpha-hemolytic streptococci, 3 of 10 strains of Clostridium perfringens but for none of 10 strains each of Streptococcus pneumoniae, and Listeria monocytogenes). Among gram-negative bacteria, a target image was regularly obtained with Haemophilus influenzae (all 10 strains tested) and Proteus species (9 of 10 strains) but with none of the following species: Escherichia coli, Salmonella, Shigella, Pseudomonas aeruginosa, Neisseria gonorrhoeae, Neisseria meningitidis and Bacteroides fragilis. Therapeutic implications of these observations are difficult to assess, and need further investigation.
mesh_terms: D001419:Bacteria / Q000187:drug effects*; D001431:Bacteriological Techniques; D001439:Bacteroides / Q000187:drug effects; D003013:Clostridium / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects; D006190:Haemophilus / Q000187:drug effects; D008087:Listeria / Q000187:drug effects; D009343:Neisseria / Q000187:drug effects; D010406:Penicillins / Q000494:pharmacology*; D011511:Proteus / Q000187:drug effects; D011549:Pseudomonas / Q000187:drug effects; D012475:Salmonella / Q000187:drug effects; D012760:Shigella / Q000187:drug effects; D013210:Staphylococcus / Q000187:drug effects; D013291:Streptococcus / Q000187:drug effects
chemical_list: D010406:Penicillins