호중구감소 생쥐 감염모델로 평가한 황색포도알균 접종량 차이에 따른 Vancomycin의 효능 (Efficacy of Vancomycin against Staphylococcus aureus according to Inoculum Size in a Neutropenic Mouse Infection Model)

서지정보

· 발행기관 : 대한감염학회
· 수록지 정보 : Infection and Chemotherapy / 43권 / 3호 / 251 ~ 257페이지
· 저자명 : 신현호, 한승훈, 임동석, 이동건, 박철민, 김시현, 권재철, 홍경욱, 박선희, 최수미, 최정현, 유진홍

초록

with treatment failure, which could be attributable to an inoculum effect (IE). Using a neutropenic mouse thigh infection model, we tried to evaluate the in vivo IE of vancomycin against S. aureus.Background: Staphylococcus aureus is one of the most important gram-positive pathogens in many clinical situations. Use of vancomycin against methicillin resistant S. aureus (MRSA) has been anecdotally associatedMaterials and Methods: Twenty strains of S. aureus were used. Minimum inhibitory concentrations (MICs) were determined by the Clinical and Laboratory Standards Institute guideline. Six-week-old specific-pathogen-free, female CD-1 mice weighing 23-27 grams were used. The neutropenic mice received inoculations of 5.02-5.74 log10 CFU/thigh in one thigh (low inoculum, LI), and 7.22-7.73 log10 CFU/thigh in the other thigh (high inoculum, HI) before therapy. The mice were treated with 6 hourly subcutaneous doses of vancomycin (3.125-100 mg/kg) for 24 h. Single-dose serum pharmacokinetics of vancomycin was determined. Dose-response data were analyzed by an Emax model using non-linear regression. Static doses and area under the curve (AUC)/MIC for bacteriostatic effect at each inoculum were calculated and compared. The ratio of static dose and AUC/MIC between HI and LI (IE index) provided the magnitude of IE for each organism.
Results: Five methicillin-susceptible S. aureus (MSSA) strains and 15 MRSA strains were used. Vancomycin MICs of the 20 strains varied by 4-fold (0.5-2 mg/L). The AUC/MIC ratio was the major parameter determining the efficacy of vancomycin against S. aureus . Mean (range) static dose on LI and HI was 20.7 (11.8-35.1) and 136.7 (32.1-314), respectively. The mean IE index of static dose between them was 7.39. Mean (range) of AUC/MIC on LI and HI was 27.0 (6.61-66.6) and 152.3 (46.2-344), respectively, which produced a mean IE index of AUC/MIC of 7.47. The IE indices of the MSSA strains were significantly higher than those of the MRSA strains (11.3 vs. 6.1 on static dose [P=0.018], 11.4 vs. 6.2 on AUC/MIC [P=0.034]).
Conclusions: With a 100-fold inoculum increment of S. aureus , at least a 7-fold dose of vancomycin would be required to show the same bacteriostatic effect. Thus, IE as well as MICs is an important parameter in selecting and adjusting a dose and dosage interval along with the resistance profile in the treatment of S. aureus infections. IE to vancomycin observed in the in vivo neutropenic mouse model was more evident for MSSA strains than for MRSA strains.

영어초록

with treatment failure, which could be attributable to an inoculum effect (IE). Using a neutropenic mouse thigh infection model, we tried to evaluate the in vivo IE of vancomycin against S. aureus.Background: Staphylococcus aureus is one of the most important gram-positive pathogens in many clinical situations. Use of vancomycin against methicillin resistant S. aureus (MRSA) has been anecdotally associatedMaterials and Methods: Twenty strains of S. aureus were used. Minimum inhibitory concentrations (MICs) were determined by the Clinical and Laboratory Standards Institute guideline. Six-week-old specific-pathogen-free, female CD-1 mice weighing 23-27 grams were used. The neutropenic mice received inoculations of 5.02-5.74 log10 CFU/thigh in one thigh (low inoculum, LI), and 7.22-7.73 log10 CFU/thigh in the other thigh (high inoculum, HI) before therapy. The mice were treated with 6 hourly subcutaneous doses of vancomycin (3.125-100 mg/kg) for 24 h. Single-dose serum pharmacokinetics of vancomycin was determined. Dose-response data were analyzed by an Emax model using non-linear regression. Static doses and area under the curve (AUC)/MIC for bacteriostatic effect at each inoculum were calculated and compared. The ratio of static dose and AUC/MIC between HI and LI (IE index) provided the magnitude of IE for each organism.
Results: Five methicillin-susceptible S. aureus (MSSA) strains and 15 MRSA strains were used. Vancomycin MICs of the 20 strains varied by 4-fold (0.5-2 mg/L). The AUC/MIC ratio was the major parameter determining the efficacy of vancomycin against S. aureus . Mean (range) static dose on LI and HI was 20.7 (11.8-35.1) and 136.7 (32.1-314), respectively. The mean IE index of static dose between them was 7.39. Mean (range) of AUC/MIC on LI and HI was 27.0 (6.61-66.6) and 152.3 (46.2-344), respectively, which produced a mean IE index of AUC/MIC of 7.47. The IE indices of the MSSA strains were significantly higher than those of the MRSA strains (11.3 vs. 6.1 on static dose [P=0.018], 11.4 vs. 6.2 on AUC/MIC [P=0.034]).
Conclusions: With a 100-fold inoculum increment of S. aureus , at least a 7-fold dose of vancomycin would be required to show the same bacteriostatic effect. Thus, IE as well as MICs is an important parameter in selecting and adjusting a dose and dosage interval along with the resistance profile in the treatment of S. aureus infections. IE to vancomycin observed in the in vivo neutropenic mouse model was more evident for MSSA strains than for MRSA strains.

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