TABLE 1.
Sensitivity and specificity of AST-based definitions for identifying carbapenemase-producing carbapenem-resistant P. aeruginosa isolates among CRPA isolates, United States, 2017 to 2019
| No. | Definition | No. of isolates with AST dataa | No. (%) of confirmed CP-CRPA isolates | No. ofb: |
% |
||||
|---|---|---|---|---|---|---|---|---|---|
| True positives | False positives | False negatives | True negatives | Sensitivity | Specificity | ||||
| 1 | R to imipenem and meropenem | 5,394 | 177 (3) | 169 | 3,338 | 8 | 1,879 | 96 | 36 |
| R to imipenem or meropenem AND: | |||||||||
| 2 | R to cefepime | 6,159 | 195 (3) | 128 | 1,459 | 67 | 4,505 | 66 | 76 |
| 3 | NS to cefepime | 6,159 | 195 (3) | 161 | 2,778 | 34 | 3,186 | 83 | 53 |
| 4 | R to ceftazidime | 5,299 | 147 (3) | 106 | 1,528 | 41 | 3,624 | 72 | 70 |
| 5 | NS to ceftazidime | 5,299 | 147 (3) | 139 | 2,021 | 9 | 3,131 | 94 | 61 |
| 6 | NS to cefepime or ceftazidime | 6,192 | 195 (3) | 178 | 2,979 | 17 | 3,018 | 91 | 50 |
| 7 | R to aztreonam | 6,095 | 184 (3) | 97 | 2,926 | 87 | 2,985 | 53 | 51 |
| 8 | NS to aztreonam | 6,095 | 184 (3) | 120 | 4,098 | 64 | 1,813 | 65 | 31 |
| 9 | R to piperacillin-tazobactam | 1,989c | 159 (8) | 75 | 684 | 84 | 1,146 | 47 | 57 |
| 10 | NS to piperacillin-tazobactam | 1,989c | 159 (8) | 129 | 1,013 | 30 | 817 | 81 | 41 |
| 11 | NS to ceftazidime-avibactam | 903d | 223 (25) | 169 | 123 | 54 | 557 | 76 | 82 |
| 12 | R to ceftolozane-tazobactam | 903d | 223 (25) | 211 | 56 | 12 | 624 | 95 | 92 |
| 13 | NS to ceftolozane-tazobactam | 903d | 223 (25) | 223 | 94 | 0 | 586 | 100 | 86 |
Number of isolates with AST data available for antimicrobial drugs evaluated in the definition. CLSI interpretative criteria were applied to designate isolates as susceptible (S), intermediate (I), or resistant (R); isolates classified as not susceptible (NS) include isolates designated I and R.
True positives met the definition and had a CP gene present; false positives met the definition but had no CP gene; false negatives did not meet the definition but had a CP gene present; true negatives did not meet the definition and had no CP gene.
Analysis was limited to CRPA isolates tested at New York and Texas public health laboratories (PHLs) during 2017 to 2019; these were the only state PHLs in which a majority of isolates had susceptibility data for piperacillin-tazobactam. Isolates tested during 2018 and 2019 are also included in the analysis of definitions 1 to 8.
Analysis was limited to CRPA isolates submitted to CDC during 2018 and 2019 through the AR Lab Network and EIP. AST for ceftazidime-avibactam and ceftolozane-tazobactam was routinely performed at CDC but not at PHLs.