Optimization of Loop-Mediated Isothermal Amplification (LAMP) for the Rapid Detection of Nosocomial Pathogens on Environmental Surfaces

Contamination of environmental surfaces by nosocomial pathogens like Pseudomonas aeruginosa (P. aeruginosa), Staphylococcus aureus (S. aureus), and Enterococcus spp. poses significant health risks worldwide. However, gold-standard detection methods are too time-consuming and labor-intensive. This study aimed to optimize loop-mediated isothermal amplification (LAMP) as a rapid, innovative, and cost-effective approach, comparing its effectiveness with the gold-standard cultural method. Sterile surfaces (24 cm2) were contaminated in duplicate with different concentrations of P. aeruginosa, S. aureus, and Enterococcus faecalis (E. faecalis) reference stains. For each pair of contaminated surfaces, one was analyzed using the agar contact plate method (UNI EN 17141:2021), while the other was analyzed using LAMP, following three different pre-incubation times (three, six, and nine hours). The sensitivity and accuracy of LAMP for P. aeruginosa improved with longer incubation times, reaching a value of 1.00 at nine hours, while the specificity and positive predictive value (PPV) remained at 1.00 regardless of the incubation time. For S. aureus, LAMP achieved a sensitivity, specificity, accuracy, PPV, and negative predictive value (NPV) of 1.00 across all incubation times. Finally, for E. faecalis, sensitivity increased from 0.57 at three hours to 1.00 at six and nine hours, with a high specificity, accuracy, PPV, and NPV from six hours onwards. These findings showed that LAMP can be used as a rapid and reliable alternative to gold-standard methods for detecting pathogens on surfaces. The high sensitivity and specificity achieved, especially at six and nine hours of pre-incubation, suggested its use for real-time monitoring in healthcare settings. Further research in real-world environments is needed to confirm these findings.