Performance of CHROMagarStaph aureusand CHROMagar MRSA for Detection of Airborne Methicillin-Resistant and Methicillin-SensitiveStaphylococcus aureus

Abstract

In recent decades, the rise of methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) has become one of the most significant problems in public health. The CHROMagar medium, which allows for direct color-based identification of target pathogens, could potentially be used to rapidly monitor airborne S. aureus and MRSA. In this study, the recovery efficiency of CHROMagar Staph aureus (CSA) for collecting airborne MSSA was evaluated in a chamber study. Subsequently, the colony identification performance of bioaerosol samplers combined with CSA and CHROMagar MRSA (C-MRSA) was evaluated in a hospital setting. Our results demonstrated that the agar medium, the type of bioaerosol sampler used, and the relative humidity all affected the recovery of the collected MSSA sample. The sampling stress that influenced the recovery of MSSA on CSA did not differ from that used when measuring its recovery on the commonly used tryptic soy agar. The average sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the colony identification were 24%, 90%, 13%, and 95%, respectively, for CSA and 71%, 65%, 16%, and 96%, respectively, for C-MRSA. Both CSA and C-MRSA had low PPV and high NPV, suggesting that a nonmauve-colored colony that is recovered on CSA or C-MRSA by air sampling can be reported as negative; however, any mauve-colored colonies should be subjected to further identification processes. On the basis of these findings, and depending upon the methods used, using CHROMagar to detect airborne MSSA or MRSA may shorten the detection time from 24 to 48 h.

Optimization of Propidium Monoazide Quantitative PCR for Evaluating Performances of Bioaerosol Samplers for Sampling AirborneStaphylococcus aureus

“…The mean concentrations of culturable S. aureus that we found in the ICU (180 CFU/m 3 ) and the GYM (476 CFU/m 3 ) were higher than those reported in hospital outpatient halls (10 CFU/m 3 ; Hsiao et al 2012) and residential environments in Texas (15 CFU/m 3 ; Gandara et al 2006). However, the culturable concentrations were similar to those from residential environments in Philadelphia (141 CFU/m 3 ), as were the mean percentages of culturable S. aureus within the total culturable bacterial concentrations (51% vs. 69%) (Perez et al 2011).…”

“…Among these studies, active sampling has been the most common method used for surveying airborne S. aureus, and the detection of MRSA in air samples suggests that the risk of infection through inhalation may be increasing Schulz et al 2012;Creamer et al 2014). However, few studies have been performed to characterize the collection efficiency and sampling stress (via impaction or impingement) on airborne S. aureus (Hsiao et al 2012;Chang and Wang 2014).…”

“…In the field study, we only used TSA agar to compare the concentrations of total bacterial aerosols, not to identify the S. aureus colonies that recovered on TSA agar. To rapidly identify S. aureus colonies in the field, another medium, CHROMagar TM Staph aureus (CSA) agar medium (CHROMagar Microbiology, Paris, France), was used in conjunction with the BioSampler to identify culturable S. aureus in the air according to methods we have described previously (Hsiao et al 2012). The CSA agar allows for direct color-based identification and can be used to target pathogens with high specificity.…”

“…In addition, the presence of airborne MRSA has been found to be significantly related to the presence of MRSA-infected or -colonized patients (Wilson et al 2004;Gehanno et al 2009). In recent years, several studies have investigated airborne MRSA using different samplers, including the Andersen 1-STG impactor (Hsiao et al 2012;Chang and Wang 2014), SAS 100 impactor (Agnoletti et al 2014), AES air sampler (Creamer et al 2014), and AGI-30 impinger . Among these studies, active sampling has been the most common method used for surveying airborne S. aureus, and the detection of MRSA in air samples suggests that the risk of infection through inhalation may be increasing Schulz et al 2012;Creamer et al 2014).…”

“…The purpose of this study was to optimize PMA-qPCR for quantifying viable S. aureus and to subsequently evaluate the effects of three bioaerosol sampling methods (the AGI-30 impinger, BioSampler, and Nuclepore filter sampler) on S. aureus recovery using culture, qPCR, and PMA-qPCR. Based on our experience, relative humidity (RH) may affect the biological efficiency of the samplers when collecting Gram-positive bacteria (Hsiao et al 2012. Therefore, samples were taken at three levels of RH (35%, 55%, and 85%).…”