Reassessment of the cefaclor breakpoint for Streptococcus pneumoniae

Mackenzie, Fiona; Milne, K.; Gould, Ian M.

doi:10.1016/j.ijantimicag.2003.09.019

Cited by 3 publications

(3 citation statements)

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“…(3) Cefaclor reduced gold nanoparticles used after 5 days of synthesis showed 100% antibacterial activity, although pure cefaclor has a half-life of ca. 9 h with 11% activity in solution, 88 indicating gold nanoparticles enhance the half-life and the activity of cefaclor. (4) Cefaclor and gold nanoparticles alone have low antibacterial effects compared to cefaclor reduced gold nanoparticles.…”

Section: Resultsmentioning

confidence: 99%

Antibiotic mediated synthesis of gold nanoparticles with potent antimicrobial activity and their application in antimicrobial coatings

2010

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We report a one-pot synthesis of spherical gold nanoparticles (52-22 nm) and their capping with cefaclor, a second-generation antibiotic, without use of other chemicals. The differently sized gold nanoparticles were fabricated by controlling the rate of reduction of gold ions in aqueous solution by varying the reaction temperature (20-70 C). The primary amine group of cefaclor acted as both the reducing and capping agent for the synthesis of gold nanoparticles leaving the b-lactam ring of cefaclor available for activity against microbes. Antimicrobial testing showed that cefaclor reduced gold nanoparticles have potent antimicrobial activity against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria as compared to cefaclor or gold nanoparticles alone. The minimum inhibition concentrations (MICs) of cefaclor reduced gold nanoparticles were 10 mg mL À1and 100 mg mL À1 for S. aureus and E. coli respectively. The cefaclor reduced gold nanoparticles were further coated onto poly(ethyleneimine) (PEI) modified glass surfaces to obtain antimicrobial coatings suitable for biomedical applications and were tested against E. coli as an exemplar of activity. The antimicrobial coatings were very robust under adverse conditions (pH 3 and 10), inhibited the growth of E. coli on their surfaces, and could be used many times with retained activity. Results from a combined spectroscopic (FTIR) and microscopic study (AFM) suggest that the action of these novel particles is through the combined action of cefaclor inhibiting the synthesis of the peptidoglycan layer and gold nanoparticles generating ''holes'' in bacterial cell walls thereby increasing the permeability of the cell wall, resulting in the leakage of cell contents and eventually cell death.

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Section: Resultsmentioning

confidence: 99%

Antibiotic mediated synthesis of gold nanoparticles with potent antimicrobial activity and their application in antimicrobial coatings

2010

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“…Previously, we carried out studies which demonstrated the instability of cefaclor in vitro, relative to the more stable compound cefuroxime 1 . Bioassays showed that cefuroxime had a half-life of >24 hours and lost 34% activity over 24 hours, whereas cefaclor had a half-life of approximately 9 hours and lost 88% activity over 24 hours 1 .…”

Section: Introductionmentioning

confidence: 99%

“…Bioassays showed that cefuroxime had a half-life of >24 hours and lost 34% activity over 24 hours, whereas cefaclor had a half-life of approximately 9 hours and lost 88% activity over 24 hours 1 . We also showed how this instability led to the determination of falsely high pneumococcal minimum inhibitory concentrations (MICs) by standard NCCLS methodology.…”

Section: Introductionmentioning

confidence: 99%

Reassessment of Cefaclor Breakpoints forHaemophilus influenzae

Mackenzie

Milne²,

Gould³

2004

Journal of Chemotherapy

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We previously reported that standard methods overestimate cefaclor minimum inhibitory concentrations (MICs) for Streptococcus pneumoniae due to in vitro chemical instability. This study aimed to ascertain if standard methods accurately measure cefaclor MICs to Haemophilus influenzae. Cefuroxime was used as a comparator. Standard NCCLS broth microdilution and E-Test MICs were determined for eight isolates of H. influenzae. Kill curves determined the "bacteriostatic" MIC, defined as the concentration showing no significant growth or kill over six hours taking into account cefaclor instability. On average, cefaclor and cefuroxime bacteriostatic MICs were 0.2 x MIC and 0.6 x MIC determined by NCCLS methodology respectively. The mean MIC determined by NCCLS methodology was 3.0 mg/L for cefaclor and 0.8 mg/L for cefuroxime. Cefaclor MICs by NCCLS methodology were overestimated due to chemical instability over 18-24 hours. The bacteriostatic MICs by kill curve were not significantly different from those of cefuroxime.

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