Evaluation of phenotypic tests for detection of Amp C beta-lactamases in clinical isolates from a tertiary care hospital of Rawalpindi, Pakistan

Nadia Saad, Tehmina Munir, Maliha Ansari, Mehreen Gilani, Mahwish Latif, Amira Haroon
JPMA. the Journal of the Pakistan Medical Association 2016, 66 (6): 658-61

OBJECTIVE: To evaluate sensitivity and specificity of disc approximation test compared to three-dimensional extract test as a phenotypic gold standard test for detection of AmpC beta-lactamase producing Escherichia coli and Klebsiella pneumoniae.

METHODS: The cross-sectional validation study was conducted from November 2014 to April 2015 at Army Medical College, Rawalpindi, Pakistan. Extended spectrum beta lactamases (ESBLs) were isolated from various clinical specimens. Screening for AmpC beta-lactamases was done by using cefoxitin disc (30µg) showing inhibition zone diameter of <18mm. Screen-positive isolates were subjected to disc approximation test (DAT) and three-dimensional extract test(3-DET).SPSS 20 was used for statistical analysis.

RESULTS: A total of 120 ESBL producing Gram negative rods were included in the study. Out of these 120, 82(68.33%) were found to be AmpC beta-lactamase producing on screening with cefoxitin disc. Amongst these 82 isolates, Escherichia coli were identified in 57(69.51%) and Klebsiella pneumoniae in 25 (30.48%). Phenotypic confirmation by disc approximation test (DAT) identified 43(52.43%). AmpC beta-lactamase producing isolates, whereas gold standard 3-DET showed 38(46.34%) of AmpC beta-lactamase producing isolates. Hence, sensitivity of disc approximation test (DAT) was found to be 88%, specificity was 92%, positive predictive value was 92.68%, negative predictive value was 87.80% and diagnostic accuracy was 90.24%.

CONCLUSIONS: Implementation of disc approximation test in the laboratories can help in identifying AmpC beta-lactamase harbouring organisms.

Full Text Links

Find Full Text Links for this Article


You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Remove bar
Read by QxMD icon Read

Save your favorite articles in one place with a free QxMD account.


Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"