Comparison of Automated System Vitek-2 with Conventional Methods, for Identification and Antibiotic Sensitivity in Gram Negative Organisms

Background: Rapid bacterial identification and susceptibility testing improves patient therapy and outcome and decreases emergence of resistance. There is a need to provide rapid, efficient and accurate system for identification and antimicrobial susceptibility testing of pathogens. In this regard the automated identification/AST systems aid in rapid diagnosis/treatment of bacterial pathogens.

Aim: Comparison of automated system Vitek-2 with conventional methods, for identification and antibiotic sensitivity in Gram negative organisms.

Settings and Design: This was a prospective study conducted in the Department of Microbiology at SKIMS, Srinagar, for eight months.

Materials and Methods: A total of 135 non duplicate isolates of gram negative bacteria were included. Organisms were processed on the Vitek-2 system and by manual methods (ID/AST) for comparison.

Statistical Analysis Use: Descriptive statistics (frequency and percentage) was used.

Results and Conclusions: Vitek-2 misidentified 6 isolates of S. typhi as E. coli, K. oxytoca (3 isolates) misidentified as K. pneumoniae, Citrobacter braakii (1 isolate) falsely reported as Citrobacter freundii, Acinetobacter baumannii (2 isolates) misidentified as Acinetobacter lwofii. No minor error (mE), major error (ME) or very major error (VME); with 100% categorical agreement (CA) was seen with ampicillin+sulbactam, piperacillin+tazobactam, ceftriaxone, cefepime, gentamicin, amikacin, levofloxacin, meropenem, colistin, co-trimoxazole, tetracycline, carbenicillin and tobramycin for various Gram negative organisms tested.however errors were seen with E. coli for ampicillin and imipenem. Likewise with K. pneumoniae, errors were seen for a ME for ciprofloxacin and imipenem. Also with P. aeruginosa, errors were seen for ceftazidime, ciprofloxacin and imipenem. No VME was seen for these antibiotics.