Epidemiology and microbiological characterization of clinical isolates of Staphylococcus aureus in a single healthcare region of the UK, 2015

Abstract

We investigated the epidemiology and characterization of isolates of Staphylococcus aureus within the Yorkshire and Humber (YH) region in the UK. In July 2015, each laboratory within YH (n = 14) was assigned two consecutive days during which all clinical isolates of S. aureus were collected. Isolates were tested for antibiotic susceptibilities and the presence of genes encoding methicillin resistance (mecA and mecC), Panton-Valentine leukocidin (PVL) (lukS-PV), and efflux-mediated chlorhexidine resistance (qacA); isolates were also characterized by spa-types. Minimum inhibitory concentrations (MICs) to chlorhexidine were determined by the broth dilution method. Of 520 isolates collected, 6·2% were methicillin-resistant S. aureus (MRSA, all mecA-positive) and mupirocin resistance was low [0·8%, 95% confidence interval (CI) 0·3-2·0] and only found in MRSA. Carriage of the qacA gene was identified in 1·7% (95% CI 0·8-3·3) of isolates and 3·5% (95% CI 2·2-5·4) had a chlorhexidine MIC of 4 mg/l. The PVL gene was infrequent (3·7%, 95% CI 2·4-5·6). Genotyping identified 234 spa-types that mapped to 22 clonal complexes. Comparison of these current data with previous work suggest that the widespread use of staphylococcal decolonization regimens over the past decade or more has not had an adverse impact on resistance rates, PVL carriage or the prevalence of specific S. aureus lineages.

Human mecC-Carrying MRSA: Clinical Implications and Risk Factors

“…Since then, several retrospective and prospective studies using human S. aureus isolates/samples were carried out in order to search for mecC -MRSA isolates ( Table 1 and Table 2 ) [ 16 , 18 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 ,…”

“…In any case, the mecC -MRSA human prevalence detected in most of the studies was very low. Several studies did not identify any mecC -positive S. aureus among included human isolates/samples ( Table 2 ) [ 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 ]. In studies in which this gene was detected ( Table 1 ), the prevalence identified, considering the total number of isolates/samples included, was < 1% in most of the cases [ 24 , 27 , 28 , 29 , 32 , 33 , 37 , 40 , 41 , 42 , 43 ], similar to that identified in the first study in which mecC was discovered (approximately 0.04%) [ 16 ].…”

Methicillin-Resistant Staphylococcus aureus Harboring mecC Still Eludes Us in East London, United Kingdom

“…The number of isolates needed to determine the prevalence of mecC in our S. aureus population was calculated using the equation described by Jones et al, using a 95% confidence level, a 5% precision level, and an expected proportion of 6.2% based on the recently reported mecA prevalence (10,12). Based on this equation, at least 89 isolates would need to be tested.…”

Clinical Value of Screening Peritoneal Dialysis Patients for Bacterial Colonization or Contamination

“…It is against this backdrop that we note the recent results of a screening program in Yorkshire and the Humber Region of the UK (19). In total, 520 isolates of S. aureus were identified from clinical samples, and the prevalence of mupirocin resistance was low at 0.8%.…”