Selection of resistant Streptococcus pneumoniae during penicillin treatment in vitro and in three animal models

2.50
Hdl Handle:
http://hdl.handle.net/2336/14667
Title:
Selection of resistant Streptococcus pneumoniae during penicillin treatment in vitro and in three animal models
Authors:
Knudsen, Jenny Dahl; Odenholt, Inga; Erlendsdottir, Helga; Gottfredsson, Magnus; Cars, Otto; Frimodt-Møller, Niels; Espersen, Frank; Kristinsson, Karl G; Gudmundsson, Sigurdur
Citation:
Antimicrob. Agents Chemother. 2003, 47(8):2499-506
Issue Date:
1-Aug-2003
Abstract:
Pharmacokinetic (PK) and pharmacodynamic (PD) properties for the selection of resistant pneumococci were studied by using three strains of the same serotype (6B) for mixed-culture infection in time-kill experiments in vitro and in three different animal models, the mouse peritonitis, the mouse thigh, and the rabbit tissue cage models. Treatment regimens with penicillin were designed to give a wide range of T(>MIC)s, the amounts of time for which the drug concentrations in serum were above the MIC. The mixed culture of the three pneumococcal strains, 10(7) CFU of strain A (MIC of penicillin, 0.016 micro g/ml; erythromycin resistant)/ml, 10(6) CFU of strain B (MIC of penicillin, 0.25 micro g/ml)/ml, and 10(5) CFU of strain C (MIC of penicillin, 4 micro g/ml)/ml, was used in the two mouse models, and a mixture of 10(5) CFU of strain A/ml, 10(4) CFU of strain B/ml, and 10(3) CFU of strain C/ml was used in the rabbit tissue cage model. During the different treatment regimens, the differences in numbers of CFU between treated and control animals were calculated to measure the efficacies of the regimens. Selective media with erythromycin or different penicillin concentrations were used to quantify the strains separately. The efficacies of penicillin in vitro were similar when individual strains or mixed cultures were studied. The eradication of the bacteria, independent of the susceptibility of the strain or strains or the presence of the strains in a mixture or on their own, followed the well-known PK and PD rules for treatment with beta-lactams: a maximum efficacy was seen when the T(>MIC) was >40 to 50% of the observation time and the ratio of the maximum concentration of the drug in serum to the MIC was >10. It was possible in all three models to select for the less-susceptible strains by using insufficient treatments. In the rabbit tissue cage model, a regrowth of pneumococci was observed; in the mouse thigh model, the ratio between the different strains changed in favor of the less-susceptible strains; and in the mouse peritonitis model, the susceptible strain disappeared and was overgrown by the less-susceptible strains. These findings with the experimental infection models confirm the importance of eradicating all the bacteria taking part in the infectious process in order to avoid selection of resistant clones.
Description:
To access publisher full text version of this article. Please click on the hyperlink in Additional Links field
Additional Links:
http://aac.asm.org/cgi/content/abstract/47/8/2499

Full metadata record

DC FieldValue Language
dc.contributor.authorKnudsen, Jenny Dahl-
dc.contributor.authorOdenholt, Inga-
dc.contributor.authorErlendsdottir, Helga-
dc.contributor.authorGottfredsson, Magnus-
dc.contributor.authorCars, Otto-
dc.contributor.authorFrimodt-Møller, Niels-
dc.contributor.authorEspersen, Frank-
dc.contributor.authorKristinsson, Karl G-
dc.contributor.authorGudmundsson, Sigurdur-
dc.date.accessioned2007-11-22T09:40:32Z-
dc.date.available2007-11-22T09:40:32Z-
dc.date.issued2003-08-01-
dc.date.submitted2007-11-22-
dc.identifier.citationAntimicrob. Agents Chemother. 2003, 47(8):2499-506en
dc.identifier.issn0066-4804-
dc.identifier.pmid12878511-
dc.identifier.urihttp://hdl.handle.net/2336/14667-
dc.descriptionTo access publisher full text version of this article. Please click on the hyperlink in Additional Links fielden
dc.description.abstractPharmacokinetic (PK) and pharmacodynamic (PD) properties for the selection of resistant pneumococci were studied by using three strains of the same serotype (6B) for mixed-culture infection in time-kill experiments in vitro and in three different animal models, the mouse peritonitis, the mouse thigh, and the rabbit tissue cage models. Treatment regimens with penicillin were designed to give a wide range of T(>MIC)s, the amounts of time for which the drug concentrations in serum were above the MIC. The mixed culture of the three pneumococcal strains, 10(7) CFU of strain A (MIC of penicillin, 0.016 micro g/ml; erythromycin resistant)/ml, 10(6) CFU of strain B (MIC of penicillin, 0.25 micro g/ml)/ml, and 10(5) CFU of strain C (MIC of penicillin, 4 micro g/ml)/ml, was used in the two mouse models, and a mixture of 10(5) CFU of strain A/ml, 10(4) CFU of strain B/ml, and 10(3) CFU of strain C/ml was used in the rabbit tissue cage model. During the different treatment regimens, the differences in numbers of CFU between treated and control animals were calculated to measure the efficacies of the regimens. Selective media with erythromycin or different penicillin concentrations were used to quantify the strains separately. The efficacies of penicillin in vitro were similar when individual strains or mixed cultures were studied. The eradication of the bacteria, independent of the susceptibility of the strain or strains or the presence of the strains in a mixture or on their own, followed the well-known PK and PD rules for treatment with beta-lactams: a maximum efficacy was seen when the T(>MIC) was >40 to 50% of the observation time and the ratio of the maximum concentration of the drug in serum to the MIC was >10. It was possible in all three models to select for the less-susceptible strains by using insufficient treatments. In the rabbit tissue cage model, a regrowth of pneumococci was observed; in the mouse thigh model, the ratio between the different strains changed in favor of the less-susceptible strains; and in the mouse peritonitis model, the susceptible strain disappeared and was overgrown by the less-susceptible strains. These findings with the experimental infection models confirm the importance of eradicating all the bacteria taking part in the infectious process in order to avoid selection of resistant clones.en
dc.language.isoenen
dc.publisherAmerican Society for Microbiologyen
dc.relation.urlhttp://aac.asm.org/cgi/content/abstract/47/8/2499en
dc.subject.meshColony-Forming Units Assayen
dc.subject.meshMicrobial Sensitivity Testsen
dc.subject.meshPenicillin Resistanceen
dc.subject.meshPenicillinsen
dc.subject.meshPeritonitisen
dc.subject.meshPneumonia, Pneumococcalen
dc.subject.meshStreptococcus pneumoniaeen
dc.titleSelection of resistant Streptococcus pneumoniae during penicillin treatment in vitro and in three animal modelsen
dc.typeArticleen
dc.identifier.journalAntimicrobial agents and chemotherapyen
dc.format.digYES-

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