Antimicrobial susceptibility of Streptococcus pneumoniae at a university hospital in Taiwan, 2000-07: impact of modified non-meningeal penicillin breakpoints in CLSI M100-S18.
OBJECTIVE
In 2008, a new set of penicillin breakpoints was published in the CLSI revised guideline, M100-S18, to define the susceptibility of non-meningeal isolates of Streptococcus pneumoniae. The impact of the change is studied and discussed.


METHODS
Laboratory data on pneumococcal isolates collected from Chang Gung Memorial Hospital during 2000-07 were analysed using the original and modified penicillin CLSI breakpoints.


RESULTS
A total of 3729 non-duplicate isolates were identifed, including 43 (1.2%) meningeal isolates showing high rates of penicillin (79.1%) and ceftriaxone (34.9%) resistance. For non-meningeal isolates, penicillin non-susceptibility was reduced significantly from 75.1% (72.4% in 2000-03 increasing to 77.4% in 2004-07) to 16% (28.6% in 2000 decreasing to 2.4% in 2007) if the modified breakpoints were applied. However, isolates for which penicillin MICs were 1-2 mg/L increased significantly from 34.2% in 2000 to 59.8% in 2007. Ceftriaxone non-susceptibility also increased significantly from 2.8% before 2005 to 18.4% thereafter. A quarter (25.7%) of the pneumococcal isolates were recovered from patients <10 years old. Higher resistance to penicillin (89.8% versus 70.4%; or 19.1% versus 13.2% by the modified breakpoints) or ceftriaxone (11.1% versus 5.8%) was found among these isolates, compared with those from older patients.


CONCLUSIONS
With the implementation of the new breakpoints, clinicians may continue to use penicillin for the treatment of non-meningeal pneumococcal infections in preference to other drug classes. However, as isolates with borderline penicillin MICs are increasing, continued surveillance of pneumococcal susceptibility to penicillin will be needed.
Su
Lin-Hui
LH
Department of Laboratory Medicine, Chang Gung Memorial Hospital, 5 Fu-Hsin Street, Kweishan, Taoyuan 333, Taiwan.
Wu
Tsu-Lan
TL
Kuo
An-Jing
AJ
Chia
Ju-Hsin
JH
Chiu
Cheng-Hsun
CH
D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D024881:Drug Resistance, Bacterial; D006785:Hospitals, University; D006801:Humans; D007223:Infant; D008826:Microbial Sensitivity Tests / Q000379:methods; D011008:Pneumococcal Infections / Q000382:microbiology*; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D013624:Taiwan; D016896:Treatment Outcome; D047090:beta-Lactams / Q000494:pharmacology* / Q000627:therapeutic use
D000900:Anti-Bacterial Agents; D047090:beta-Lactams