TY - JOUR
T1 - Ampicillin resistance in Hemophilus parainfluenzae
AU - Walker, C. N.
AU - Smith, P. W.
PY - 1980
Y1 - 1980
N2 - Ampicillin resistance among strains of Hemophilus is usually due to production of beta-lactamase. This paper reports the isolation of a strain of H. parainfluenzae resistant to ampicillin with no detectable beta-lactamase or amidase activity. The organism, isolated from the blood of a patient who had aortic valve endocarditis, gave a zone diameter consistent with ampicillin sensitivity when tested by disc diffusion in Mueller-Hinton agar supplemented with 1% IsoVitaleX and 1% hemoglobin. Broth dilution testing in Levinthal medium, however, revealed the following minimal inhibitory concentrations: ampicillin, 32 μg/ml; penicillin, 256 μg/ml; methicillin, 128 μg/ml; carbenicillin, 128 μg/ml; and cephalothin and chloramphenicol, 1.0 μg/ml. The results of acidimetric, iodometric, and chromogenic cephalosporin methods for detection of beta-lactamase were negative. Beta-lactamase activity could not be demonstrated in cell sonicates or induced by growth of the cells in antibiotic-containing medium. In addition, no extracellular degradation of either ampicillin or penicillin could be demonstrated.
AB - Ampicillin resistance among strains of Hemophilus is usually due to production of beta-lactamase. This paper reports the isolation of a strain of H. parainfluenzae resistant to ampicillin with no detectable beta-lactamase or amidase activity. The organism, isolated from the blood of a patient who had aortic valve endocarditis, gave a zone diameter consistent with ampicillin sensitivity when tested by disc diffusion in Mueller-Hinton agar supplemented with 1% IsoVitaleX and 1% hemoglobin. Broth dilution testing in Levinthal medium, however, revealed the following minimal inhibitory concentrations: ampicillin, 32 μg/ml; penicillin, 256 μg/ml; methicillin, 128 μg/ml; carbenicillin, 128 μg/ml; and cephalothin and chloramphenicol, 1.0 μg/ml. The results of acidimetric, iodometric, and chromogenic cephalosporin methods for detection of beta-lactamase were negative. Beta-lactamase activity could not be demonstrated in cell sonicates or induced by growth of the cells in antibiotic-containing medium. In addition, no extracellular degradation of either ampicillin or penicillin could be demonstrated.
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U2 - 10.1093/ajcp/74.2.229
DO - 10.1093/ajcp/74.2.229
M3 - Article
C2 - 6967694
AN - SCOPUS:0019303877
SN - 0002-9173
VL - 74
SP - 229
EP - 232
JO - American journal of clinical pathology
JF - American journal of clinical pathology
IS - 2
ER -