Prospective Two-Center Comparison of Three Chromogenic Agars for Methicillin-Resistant Staphylococcus aureus Screening in Hospitalized Patients

Abstract

bThree chromogenic media, chromID MRSA SMART (SMART), chromID MRSA first generation (chromID), and Brilliance MRSA (OX2), were evaluated for methicillin-resistant Staphylococcus aureus (MRSA) screening using 1,220 samples. The sensitivity at 24 h was significantly better with the SMART agar (66.4%) than that with chromID agar (50.5%). Enrichment and incubation until 48 h are still needed for an optimal yield. M ethicillin-resistant Staphylococcus aureus (MRSA) is a major cause of nosocomial infections (1, 2). Asymptomatic carriers in the nose, throat, or on the skin represent the major reservoirs for MRSA transmission in hospitals (3, 4). Rapid identification of MRSA colonization is of utmost importance to identify carriers in order to implement infection control procedures and reduce patient-to-patient transmission (5-7). Several chromogenic agars have been specifically developed for MRSA screening. These media show superior sensitivity and specificity compared to those of conventional selective plates (8-10). The purpose of this study was to compare the performance of the new bioMérieux chromID MRSA SMART (SMART) agar with bioMérieux chromID MRSA first generation (chromID) and Oxoid Brilliance MRSA version 2 agar (OX2) with and without enrichment broth (EB).This prospective study was conducted between January and May 2014 at Hôpital Erasme, Brussels, Belgium, and Amphia Hospital, Breda, The Netherlands. Screening samples were collected from patients admitted to both hospitals using ESwab transport medium (Copan Diagnostics). The swabs were inoculated into EB supplemented with 6.5% NaCl (bioMérieux) and directly on the SMART, chromID, and OX2 agars, and a Colombia agar plate with 5% sheep blood (SBA) (growth control) at 35 to 37°C. EB was subcultured after 24 h onto secondary selective plates. Primary plates were examined at 24 h and 48 h, and secondary plates were examined after 24 h. The assessments included comparative amounts of growth of presumptive MRSA/sample and the amount of background flora able to grow on the three media. All suspected MRSA colonies were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and methicillin susceptibility was determined by the cefoxitin disk method, as recommended by EUCAST (11).Each new MRSA isolate per patient and discrepant results between the three media were tested for the presence of the mecA gene by in-house PCR (Erasme) (12) or GeneXpert (Xpert SA nasal G3 kit version 4; Cepheid) (Amphia). Discrepant results (typical MRSA colonies and mecA negative) were further analyzed for the presence of the mecC gene, and the MICs to cefoxitin and oxacillin were determined (11, 13). The presence of MRSA recovered from at least one of the media (primary chromogenic agar or after enrichment) was considered the gold standard. True-positive results were defined as MRSA isolates showing characteristic colonies (color and morphology) confirmed by PCR, false-positive results as isolates with typical colonies not confirmed by PC...

Corynebacterium accolens Has Antimicrobial Activity against Staphylococcus aureus and Methicillin-Resistant S. aureus Pathogens Isolated from the Sinonasal Niche of Chronic Rhinosinusitis Patients

“…S. aureus clinical isolates were identified from nasal swabs of CRS patients by culturing on mannitol salt agar (Oxoid, Basingstoke, UK) at 37 °C overnight followed by species-level identification using API 20 Staph test system (bioMerieux, Australia) according to the manufacturer’s instructions. All isolates were then screened for MRSA using a super sensitive and specific chromogenic MRSA selective agar (CHROMID ® MRSA SMART, bioMerieux, Australia) as described previously [ 32 ].…”

The Effect of Universal Decolonization With Screening in Critical Care to Reduce MRSA Across an Entire Hospital

“…MRSA screening is not completely effective at detecting all patients with MRSA carriage; in some cases, sensitivity has been reported as low as 50.5%. 20 Universal MRSA decolonization of patients in the ICU could be masking ineffective screening; thus, patients who are not known to be MRSA positive would be receiving decolonization therapy. In turn, this could reduce the spread of MRSA within the ICU setting and across the UHB.…”

“…Another reason for the reduced number of MRSA cases and acquisition rates could be due to the masking of poor MRSA screening within UHB. MRSA screening is not completely effective at detecting all patients with MRSA carriage; in some cases, sensitivity has been reported as low as 50.5% 20 . Universal MRSA decolonization of patients in the ICU could be masking ineffective screening; thus, patients who are not known to be MRSA positive would be receiving decolonization therapy.…”

Epidemiological Study on Case Definition of Methicillin-Resistant Staphylococcus aureus Enteritis

“…7 In addition, while the efficacy of screening for MRSA using chromogenic media has been reported, its diagnostic utility remains uncertain. 8 This is due to the lack of a firm definition of MRSA enteritis, which is caused by a lack of definition of diarrheal symptoms and frequency, inadequate studies on the number of MRSA detected, lack of routine examination of virulence factors and lack of pathological studies. 9 In contrast, Clostridioides difficile infection (CDI) is often observed in healthcare facilities, 10 and appropriate diagnostic criteria have been established.…”