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Volume 32, Supplement –Summer 2026
SUPPLEMENT ISSUE
Supplement
Evaluation of Detection Methods for Wastewater Surveillance of Antimicrobial-Resistant Bacteria from Healthcare Facilities
Table 3
Limits of detection for isolates diluted in wastewater and detected by qPCR and culture-based methods and for qPCR-positive controls diluted in 1X PBS in study of detection methods for wastewater surveillance of antimicrobial-resistant bacteria from healthcare facilities*
| Antimicrobial-resistant gene | Observed GC/mL wastewater, mean +SD | Extrapolated culture detection limit, CFU/mL wastewater |
Observed qPCR positive control detection limit, GC/μL qPCR reaction§ | |
|---|---|---|---|---|
| Independent estimate, mean +SD† | Combined estimate, limit (95% CI)‡ | |||
| blaKPC | Not estimable | Not estimable | 32 | |
| blaOXA-48-like | Not estimable | Not estimable | 34 | |
| blaVIM | 146 +92¶ | 38 +41 | 26 (2.9–865) | 241 |
| blaNDM | 284 +154 | 25 +24 | 17 (2.2–1,592) | 390 |
| blaIMP | 5,486 +3,137 | 337 +341 | 216 (4.2–1,5437) | 2200 |
*Not estimable indicates wastewater contained blaKPC and blaOXA-48-like genes. GC, gene copies; PBS, phosphate-buffered saline; qPCR, quantitative PCR. †The culture detection limit for each of 3 trials was estimated independently based on linear regressions and a cycle threshold (Ct) cutoff of 35; then, the mean and SD of those detection limits was estimated. ‡The detection limit for all 3 trials combined was estimated from the linear regression. §Estimated from qPCR standard curves. ¶Analysis of variance or analysis of variance on ranks was used to determine for each trial the mean Ct value for the lowest dilution that was above a Ct of 35 and at a significantly different concentration than the next lowest dilution. The qPCR standard curve calculation was then used for this Ct to estimate the GC/mL. Mean and SD GC/mL for the 3 trials was then estimated.