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dc.contributor.authorAnderl, Jeff N.
dc.contributor.authorFranklin, Michael J.
dc.contributor.authorStewart, Philip S.
dc.date.accessioned2017-06-21T15:35:00Z
dc.date.available2017-06-21T15:35:00Z
dc.date.issued2000
dc.identifier.citationAnderl, J. N., M. J. Franklin, and P. S. Stewart. “Role of Antibiotic Penetration Limitation in Klebsiella Pneumoniae Biofilm Resistance to Ampicillin and Ciprofloxacin.” Antimicrobial Agents and Chemotherapy 44, no. 7 (July 1, 2000): 1818–1824. doi:10.1128/aac.44.7.1818-1824.2000.en_US
dc.identifier.issn0066-4804
dc.identifier.urihttps://scholarworks.montana.edu/xmlui/handle/1/13125
dc.description.abstractThe penetration of two antibiotics—ampicillin and ciprofloxacin—through biofilms developed in an in vitro model system was investigated. The susceptibilities of biofilms and corresponding freely suspended bacteria, to killing by the antibiotics were also measured. Biofilms of Klebsiella pneumoniae were developed on microporous membranes resting on agar nutrient medium. The susceptibilities of planktonic cultures and biofilms to 10 times the MIC were determined. Antibiotic penetration through biofilms was measured by assaying the concentration of antibiotic that diffused through the biofilm to an overlying filter disk. Parallel experiments were performed with a mutant K. pneumoniae strain in which B-lactamase activity was eliminated. For wild-type K. pneumoniae grown in suspension culture, ampicillin and ciprofloxacin MICs were 500 and 0.18 ug/ml, respectively. The log reductions in the number of CFU of planktonic wild-type bacteria after 4 h of treatment at 10 times the MIC were 4.43 + 0.33 and 4.14 + 0.33 for ampicillin and ciprofloxacin, respectively. Biofilms of the same strain were much less susceptible, yielding log reductions in the number of CFU of – 0.06 + 0.06 and 1.02 + 0.04 for ampicillin and ciprofloxacin, respectively, for the same treatment. The number of CFU in the biofilms after 24 h of antibiotic exposure was not statistically different from the number after 4 h of treatment. Ampicillin did not penetrate wild-type K. pneumoniae biofilms, whereas ciprofloxacin and a nonreactive tracer (chloride ion) penetrated the biofilms quickly. The concentration of ciprofloxacin reached the MIC throughout the biofilm within 20 min. Ampicillin penetrated biofilms formed by a B-lactamase-deficient mutant. However, the biofilms formed by this mutant were resistant to ampicillin treatment, exhibiting a 0.18 + 0.07 log reduction in the number of CFU after 4 h of exposure and a 1.64 + 0.33 log reduction in the number of CFU after 24 h of exposure. Poor penetration contributed to wild-type biofilm resistance to ampicillin but not to ciprofloxacin. The increased resistance of the wild-type strain to ciprofloxacin and the mutant strain to ampicillin and ciprofloxacin could not be accounted for by antibiotic inactivation or slow diffusion since these antibiotics fully penetrated the biofilms. These results suggest that some other resistance mechanism is involved for both agents.en_US
dc.titleRole of antibiotic penetration limitation in Klebsiella pneumoniae biofilm resistance to ampicillin and ciprofloxacinen_US
dc.typeArticleen_US
mus.citation.extentfirstpage1818en_US
mus.citation.extentlastpage1824en_US
mus.citation.issue7en_US
mus.citation.journaltitleAntimicrobial Agents and Chemotherapyen_US
mus.citation.volume44en_US
mus.identifier.categoryEngineering & Computer Scienceen_US
mus.identifier.doi10.1128/aac.44.7.1818-1824.2000en_US
mus.relation.collegeCollege of Engineeringen_US
mus.relation.departmentCenter for Biofilm Engineering.en_US
mus.relation.departmentChemical & Biological Engineering.en_US
mus.relation.departmentChemical Engineering.en_US
mus.relation.departmentMicrobiology & Immunology.en_US
mus.relation.universityMontana State University - Bozemanen_US
mus.relation.researchgroupCenter for Biofilm Engineering.en_US
mus.data.thumbpage4en_US


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