Evaluating ATP Bioluminescence Testing for Microbial Surveillance of Materials and Solutions Used in the Routine Cleaning of Cranial Implant Chambers in Rhesus Macaques (Macaca mulatta)
Nonhuman primates with long-term cranial implant chambers require regular chamber cleaning with antiseptic solutions. The purpose of this study was to determine if ATP bioluminescence testing can be used to identify microbial contamination of fomites and environmental samples in the context of cranial implant chamber cleaning procedures. ATP bioluminescent swab samples were compared with traditional bacterial culture swab samples from the same sources collected during the scheduled chamber maintenance procedures for Rhesus macaques (Macaca mulatta) that are part of studies related to the modulation of brain circuits in parkinsonism. Over the course of 17 d, samples were collected from the chamber rims, forceps (pre- and postcleaning), povidone-iodine bottle, quaternary ammonium and alcohol-based disinfectant solution containers, and cotton ball jar (ATP swab: n = 10 per environmental source; bacterial culture swab: n = 6 per environmental source). Chamber rims yielded the highest ATP relative light unit values compared with the other environmental sample groups and heavy growth on bacterial culture. A total of 16/36 (44%) swab samples from environmental sources yielded growth on bacterial culture, and clinically relevant bacterial species were identified in samples from the chamber rims, cotton ball jar, povidone-iodine bottle, and forceps. Although high ATP RLU levels and positive bacterial growth were identified for these environmental samples, there was a poor correlation between the ATP RLU values with the semiquantitative bacterial culture scores. Based on the results of this study, a high ATP RLU cutoff threshold would be needed to maximize the accuracy of using this method instead of bacterial culture to identify potential sources of microbial contamination. This study represents the first published microbial surveillance investigation of environmental samples from materials and solutions used in cranial implant chamber maintenance.
Instruments and solutions required for cranial implant chamber maintenance. (1) Glass bead sterilizer. (2) Separate forceps dedicated to the left and right chambers. (3) Cotton ball jar. (4) 0.9% NaCl solution. (5) Containers of QAC-IPA, each dedicated to the left and right chambers. (6) Chlorhexidine gluconate solution. (7) Hydrogen peroxide. (8) PVP-I bottle.
Box and whisker plot of ATP RLU value by environmental group. Transformed ATP RLU values used for graphical representation and analyses (ATP RLU +1). Environmental samples from both animals were pooled together. For each group n = 10, for a total of 70 samples. For each box, the line inside indicates the median, the top and bottom of the boxes represent the 75th and 25th percentiles respectively, and the whiskers extend from the 10th to the 90th percentile. ×, P < 0.0005; §, P < 0.0001.
Bacterial culture results. (A) Percentage of samples yielding bacterial growth per environmental group, samples for both animals were pooled together. (B–F) Semiquantitative culture scores depicted for each sample by environmental group and animal; n = 36.
Scatterplot of ATP RLU by semiquantitative culture scores for environmental samples. Red points indicate values obtained from chamber rim samples. Black points represent all other environmental groups. Transformed ATP RLU values used for graphical representation and analyses (ATP RLU +1). For all environmental samples (n = 36), Spearman ρ = 0.3553; 95% CI = 0.02016 to 0.6186 (P < 0.05). Excluding the chamber rim samples (n = 30), Spearman ρ = 0.03965; 95% CI = −0.3352 to 0.4037 (P = 0.8352).
Receiver operator characteristic (ROC) curve using ATP RLU to predict growth on bacterial culture. Points on the scatterplot correspond to the sensitivity and 1-specificity for different ATP RLU cutoff thresholds. The area under the ROC curve is depicted by the shaded portion (AUC = 0.6594; 95% CI = 0.4744 to 0.8443; P = 0.1045). The red line denotes the 0.5 AUC, corresponding to the 50/50 chance for a sample yielding a positive or negative result. Since the 95% CI extends below 0.5, the use of ATP RLU as a test to predict bacterial culture growth is not significantly significant.
Contributor Notes
This article contains supplemental materials online.