Rapid differentiation of Staphylococcus aureus, Staphylococcus epidermidis and other coagulase-negative staphylococci and meticillin susceptibility testing directly from growth-positive blood cultures by multiplex real-time PCR.
This study evaluated a multiplex real-time PCR method specific for the mecA, femA-SA and femA-SE genes for rapid identification of Staphylococcus aureus, Staphylococcus epidermidis and non-S. epidermidis coagulase-negative staphylococci (CoNS), and meticillin susceptibility testing directly in positive blood cultures that grew Gram-positive cocci in clusters. A total of 100 positive blood cultures produced: 39 S. aureus [12 meticillin-resistant S. aureus (MRSA), 31% of all the S. aureus]; 30 S. epidermidis (56.6% of the CoNS), 8 Staphylococcus capitis (15.1%), 3 Staphylococcus saprophyticus (5.7%), 4 Staphylococcus hominis (7.5%), 3 Staphylococcus haemolyticus (5.7%), 2 Staphylococcus warneri (3.8%), 1 Staphylococcus cohnii (1.9%) and 2 unidentified Staphylococcus spp. (3.8%); and 1 Micrococcus luteus in pure culture. Two blood cultures had no growth on subculture and five blood cultures grew mixed CoNS. For the 95 blood cultures with pure growth or no growth on subculture, there was very good agreement between real-time PCR and the BD Phoenix identification system for staphylococcal species categorization in S. aureus, S. epidermidis and non-S. epidermidis CoNS and meticillin-resistance determination (Cohen's unweighted kappa coefficient κ=0.882). All MRSA and meticillin-susceptible S. aureus were correctly identified by mecA amplification. PCR amplification of mecA was more sensitive for direct detection of meticillin-resistant CoNS in positive blood cultures than testing with the BD Phoenix system. There were no major errors when identifying staphylococcal isolates and their meticillin susceptibility within 2.5 h. Further studies are needed to evaluate the clinical benefit of using such a rapid test on the consumption of glycopeptide antibiotics and the alteration of empiric therapy in the situation of positive blood cultures growing staphylococci, and the respective clinical outcomes.
Jukes
Leanne
L
Public Health Wales Microbiology ABM Swansea, Singleton Hospital, Abertawe-Bro Morgannwg University Health Board, Swansea, UK.
Mikhail
Jane
J
Medical Microbiology and Infectious Diseases, Institute of Life Science, School of Medicine, Swansea University, Swansea, UK.
Bome-Mannathoko
Naledi
N
Medical Microbiology and Infectious Diseases, Institute of Life Science, School of Medicine, Swansea University, Swansea, UK.
Hadfield
Stephen J
SJ
Public Health Wales Microbiology ABM Swansea, Singleton Hospital, Abertawe-Bro Morgannwg University Health Board, Swansea, UK.
Harris
Llinos G
LG
Medical Microbiology and Infectious Diseases, Institute of Life Science, School of Medicine, Swansea University, Swansea, UK.
El-Bouri
Khalid
K
Public Health Wales Microbiology ABM Swansea, Singleton Hospital, Abertawe-Bro Morgannwg University Health Board, Swansea, UK.
Davies
Angharad P
AP
Medical Microbiology and Infectious Diseases, Institute of Life Science, School of Medicine, Swansea University, Swansea, UK.|Public Health Wales Microbiology ABM Swansea, Singleton Hospital, Abertawe-Bro Morgannwg University Health Board, Swansea, UK.
Mack
Dietrich
D
Medical Microbiology and Infectious Diseases, Institute of Life Science, School of Medicine, Swansea University, Swansea, UK.|Public Health Wales Microbiology ABM Swansea, Singleton Hospital, Abertawe-Bro Morgannwg University Health Board, Swansea, UK.
D004269:DNA, Bacterial / Q000145:classification / Q000235:genetics; D006801:Humans; D016106:Methicillin Resistance; D016133:Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification* / Q000235:genetics; D013212:Staphylococcus epidermidis / Q000145:classification* / Q000235:genetics; D013997:Time Factors
D004269:DNA, Bacterial