Influence of the β-lactam resistance phenotype on the cefuroxime versus cefditoren susceptibility of Streptococcus pneumoniae and Haemophilus influenzae recovered from children with acute otitis media

Abstract

Susceptibility to sentinel beta-lactams cannot predict activity of other members of the group. The addition of clavulanic acid to amoxicillin does not guarantee 100% coverage of H. influenzae, regardless of beta-lactamase production.

Influence of TEM-1 β-Lactamase on the Pharmacodynamic Activity of Simulated Total versus Free-Drug Serum Concentrations of Cefditoren (400 Milligrams) versus Amoxicillin-Clavulanic Acid (2,000/125 Milligrams) against Haemophilus influenzae Strains Exhibiting an N526K Mutation in the ftsI Gene

“…The experimental bactericidal activity of cefditoren is maintained over the dosing interval regardless of the presence of mutation in the ftsI gene or ␤-lactamase production. Although cefditoren exhibits high protein binding, free concentrations were enough to be active against H. influenzae that, as in the present study, exhibit low cefditoren MICs regardless of the resistance phenotype (10,12). …”

“…A portion (60 ml) of this inoculum was introduced into the peripheral compartment. Samples (0.5 ml) from the peripheral compartment were collected at 0, 1, 2, 3, 4,6,8,10,12,24,25,26,27,28,30,32,34,36, and 48 h and serially diluted in 0.9% of cold sodium chloride. At least four dilutions of each sample were spread onto chocolate agar, followed by incubation at 37°C, and colonies were counted after 24 h. The limit of detection was 50 CFU/ml.…”

“…For the measurement of simulated antimicrobial concentrations, additional aliquots (0.5 ml) were drawn from the peripheral compartment at 0, 1, 2, 3, 4,6,8,10,12,24,25,26,27,28,30,32,34,36, and 48 h and at the time corresponding to the target T max of each antimicrobial in simulations with ␤-lactamase-positive and -negative strains. All samples were stored at Ϫ50°C until use.…”

Evolution of Clonal and Susceptibility Profiles of Serotype 19A Streptococcus pneumoniae among Invasive Isolates from Children in Spain, 1990 to 2008

“…MIC determination was performed by agar dilution using Mueller-Hinton agar (Difco Laboratories, Detroit, MI) supplemented with 5% sheep blood (Biomedics, Madrid, Spain) as the culture medium and incubation under a 5% CO 2 atmosphere, as previously described (11). S. pneumoniae ATCC 6303 and S. pneumoniae ATCC 49619 plus five clinical strains were used as quality controls, as in all determinations in the SRLP (11).…”

“…S. pneumoniae ATCC 6303 and S. pneumoniae ATCC 49619 plus five clinical strains were used as quality controls, as in all determinations in the SRLP (11). CLSI breakpoints (7) were used for interpretation (susceptibility/resistance [g/ml]): penicillin orally, Յ0.06/Ն2; penicillin parenterally, Յ2/Ն8; amoxicillin, Յ 2/Ն8; cefotaxime (nonmeningitis), Յ1/Ն4; and erythromycin, Յ0.25/Ն1.…”