title: Comparison of disc diffusion methods for the detection of extended-spectrum Beta lactamase-producing enterobacteriaceae.
abstract: BACKGROUND
  Resistance to broad-spectrum β lactams, mediated by extended-spectrum β lactamases (ESBLs), is an increasing problem world wide. This resistance poses problems for in vitro testing and reporting. Increased prevalence of ESBLs among Enterobacteriaceae creates a great need for laboratory testing methods that will accurately identify their presence.
  
  
  METHODS
  During the study, the Enterobacteriaceae isolated were tested for the presence of ESBL by the National Committee for Clinical Laboratory Standards (NCCLS) screening test, Jarlier double disc synergy (approximation) test (DDST) and NCCLS phenotypic confirmatory test (PCT), and compared their efficiency in detection.
  
  
  RESULTS
  A total of 313 Enterobacteriaceae were isolated and tested for the presence of ESBL. NCCLS PCT identified 200 (63.89%) as ESBL producers and DDST identified 176 (56.23%), with a P-value of <0.001. Among the screening agents, ceftazidime had a better sensitivity (89.49%) and specificity (95.74%).
  
  
  CONCLUSIONS
  Close monitoring of the susceptibility pattern of isolates and careful spacing with specific discs can identify many ESBL producers. Ceftazidime has a better sensitivity and specificity as a screening agent. A combination of different tests can be useful for accurate identification.
authors.affiliation: Department of Microbiology, PES Institute of Medical Sciences and Research, Kuppam, Andhra Pradesh, India.
authors.forename: Ravi S
authors.initials: RS
authors.lastname: Giriyapur
authors.forename: Namratha W
authors.initials: NW
authors.lastname: Nandihal
authors.forename: B V S
authors.initials: BV
authors.lastname: Krishna
authors.forename: Asha B
authors.initials: AB
authors.lastname: Patil
authors.forename: M R
authors.initials: MR
authors.lastname: Chandrasekhar