875. Optimal Strategy to Identify KPC-Possessing Enterobacteriaceae Using the Updated CLSI Breakpoints
Session: Oral Abstract Session: Antimicrobial Resistance and Susceptibility
Saturday, October 22, 2011: 11:30 AM
Room: 151AB
Background: Detection of Enterobacteriaceae with the carbapenemase KPC has been problematic, and ertapenem has been recommended as the class agent for carbapenem susceptibility testing.  In 2010, CLSI lowered the breakpoints for susceptibility for several carbapenems and cephalosporins. The optimal strategy for detection of organisms with KPC using these updated guidelines needs to be defined.

Methods: Single patient isolates of E. coli, K. pneumoniae, and Enterobacter sp. were gathered during surveillance studies conducted in New York City in 2006 and 2009. Susceptibility testing was performed by CLSI standards, and all cephalosporin resistant isolates were screened by PCR for the presence of blaKPC. The sensitivity, specificity, and positive predictive value of the updated breakpoints in identifying KPC-possessing pathogens were calculated.

Results: A total of 7057 isolates were collected, including 4466 isolates of E. coli (14 with KPC), 2173 isolates of K. pneumoniae (721 with KPC), and 418 isolates of Enterobacter sp (23 with KPC).  Using the updated CLSI breakpoints, the sensitivity, specificity, and positive predictive value of nonsusceptibility to carbapenems for detecting KPC possessing isolates are listed in the Table.

 

Sensitivity

Specificity

Positive Predictive Value

E. coli

 Ertapenem

100

99.8

60.9

 Imipenem

71.4

99.9

76.9

 Meropenem

100

100

87.5

K. pneumoniae

 Ertapenem

100

96.8

93.9

 Imipenem

91.5

99

97.8

 Meropenem

97.8

97.8

95.6

Enterobacter sp.

 Ertapenem

90.9

85.6

26.3

 Imipenem

81.8

97.7

66.7

 Meropenem

95.5

100

100

Conclusion: Using the updated CLSI breakpoints, all three carbapenems tested could accurately identify KPC-possessing K. pneumoniae. However, the positive predictive value of ertapenem nonsusceptibility was inferior in identifying KPC-possessing E. coli and Enterobacter sp. In an area endemic for KPC-possessing bacteria, when the updated CLSI breakpoints are implemented, meropenem should be used as the class agent for carbapenem testing of Enterobacteriaceae.

 


Subject Category: A. Antimicrobial agents and Resistance

Manisha Singh, MBBS, Julius Salamera, MD, David Landman, MD and John Quale, MD, SUNY Downstate Medical Center, Brooklyn, NY

Disclosures:

M. Singh, None

J. Salamera, None

D. Landman, None

J. Quale, None

<< Previous Abstract | Next Abstract

Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.