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Diagn Microbiol Infect Dis. 2015 Nov;83(3):286-91. doi: 10.1016/j.diagmicrobio.2015.07.011. Epub 2015 Jul 18.

The cefazolin inoculum effect in methicillin-susceptible Staphylococcus aureus blood isolates: their association with dysfunctional accessory gene regulator (agr).

Author information

1
Division of Infectious Diseases, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Republic of Korea; Department of Medicine, The Graduate School of Yonsei University, Seoul, Republic of Korea.
2
Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea.
3
Division of Infectious Diseases, Inje University Busan Paik Hospital, Busan, Republic of Korea.
4
Division of Infectious Diseases, Keimyung University Dongsan Medical Center, Daegu, Republic of Korea.
5
Division of Infectious Diseases, Dong-A University, Busan, Republic of Korea.
6
Division of Infectious Diseases, Konkuk University Hospital, Seoul, Republic of Korea.
7
Division of Infectious Diseases, Kyung Hee University Hospital at Gangdong, Seoul, Republic of Korea.
8
Division of Infectious Diseases, Kangdong Sacred Heart Hospital, Hallym University School of Medicine, Seoul, Republic of Korea.
9
Division of Infectious Diseases, Daegu Fatima Hospital, Daegu, Republic of Korea.
10
Department of Medicine, The Graduate School of Yonsei University, Seoul, Republic of Korea.
11
Division of Infectious Diseases, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
12
Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Republic of Korea. Electronic address: ksko@skku.edu.
13
Division of Infectious Diseases, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. Electronic address: iddrchung@gmail.com.

Abstract

We evaluated the clinical significance of the cefazolin inoculum effect (CIE) in methicillin-susceptible Staphylococcus aureus (MSSA) isolates. In total, 146 isolates were recovered from patients with MSSA bacteremia at 9 hospitals in Korea. The CIE was observed in 16 MSSA isolates, and while type A was the only detected β-lactamase in MSSA isolates exhibiting the CIE, no strains expressing type B, C, or D β-lactamases exhibited this effect. The CIE was only observed in agr group III and I isolates and was significantly more common in isolates with agr dysfunction than in those with functional agr (P<0.001). Even among isolates producing type A β-lactamase, the CIE was also prevalent in isolates with dysfunctional agr than in isolates with functional agr (P=0.025). This study demonstrates an association between the CIE of MSSA isolates and agr dysfunction, in addition to those between the CIE and type A β-lactamase.

KEYWORDS:

Accessory gene regulator; Cefazolin; Inoculum effect; Methicillin-susceptible S. aureus

[Indexed for MEDLINE]

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