Performance comparison of screening methods for bacterial heteroresistance

Background Rapid and accurate detection of antibiotic heteroresistance (HR) causing clinical bacterial infections opens up a chance for prompt and effective treatment. However, current detection methods vary across laboratories. Methods Our study compared the two initial screening methods, a modified E-test and microtitration population analysis profiling (MPAP), and evaluated the capacity of MPAP for initial screening from HR. Results 56 strains of Carbapenem-resistant Escherichia coli (CREC) were collected from three hospital centers. Among them, 25.0% (14/56), 39.3% (22/56) and 37.5% (21/56) were heteroresistant to tigecycline (TGC) by the modified E-test, MPAP and population analysis profiling (PAP), respectively. Compared with the reference method PAP, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of the modified E-test and MPAP were 66.7% versus 100% (χ ²  = 0.224, P <  0.01), 100% versus 97.1% (χ ²  = 8.223, P  > 0.05), 100% versus 95.5% (χ ²  = 5.88, P  > 0.05), 83.3% versus 100% (χ ²  = 63.224, P  < 0.05), and 87.5% versus 98.2% (χ ²  = 3.24, P  > 0.05), respectively. A total of 305 isolates of methicillin-resistant Staphylococcus aureus (MRSA) were detected by the modified E-test, MPAP and PAP. 24.1% (76/305), 37.4% (114/305) and 34.1% (104/305) were heteroresistant to vancomycin (VAN) and 27.9% (85/305), 54.4% (166/305) and 53.8% (163/305) were heteroresistant to teicoplanin (TEC). When detecting heteroresistance to VAN, compared with the reference method PAP, the sensitivity, specificity, PPV, NPV and accuracy of the modified E-test and MPAP were 70.2% versus 100% (χ ²  = 36.429, P <  0.01), 98.5% versus 95.0% (χ ²  = 3.895, P  < 0.05), 96.0% versus 91.2% (χ ²  = 141.204, P <  0.01), 86.4% versus 100% (χ ²  = 727.916, P  < 0.01), and 88.9% versus 96.7% (χ ²  = 727.916, P  < 0.01), respectively. When detecting heteroresistance to TEC, compared with PAP, the sensitivity, specificity, PPV, NPV and accuracy of the modified E-test and MPAP were 48.8% versus 99.4% (χ ²  = 109.397, P <  0.01), 96.5% versus 97.9% (χ ²  = 209.425, P <  0.01), 94.2% versus 98.2% (χ ²  = 3.025, P  > 0.05), 61.8% versus 99.3% (χ ²  = 66.154, P <  0.01), and 70.8% versus 98.7% (χ ²  = 14.789, P <  0.01), respectively. Conclusions Our results indicated that HR had a high detection rate. It is necessary for laboratories to screen for HR. In terms of detection capacity, MPAP appears to be a better choice for initial screening .