Efficacy of a novel PCR- and microarray-based method in diagnosis of a prosthetic joint infection

Figures & data

Table 1. Demographic data on 61 patients with suspected prosthetic joint infection and 20 negative controls, and on the number of samples analyzed

	Study group	Control group	p-value
Samples, n	102	40
Patients	61	20
Male	30	12	0.5
Female	31	8	0.5
Mean (SD) age, years	68 (12.8)	69 (8.5)
Hips (%)	22 (36%)	12 (60%)	0.07
Knees (%)	39 (64%)	8 (40%)	0.07
No. of operations	29	20
Mean (range) no. of
PCR-based samples/operation	2.1 (1–4)	2.0
culture samples/operation	5.6 (3–11)	4.3 (2–6)
needle aspirations/patient	0.65 (0–2)	0
No. of needle aspirations	40	0

Table 2. The results of PCR and microarray assay in 61 patients with suspected prosthetic joint infection

Bacteria	No. of patients
Prosthetic joint infection fulfilling MSIS criteria (n = 38)
Staphylococcus aureus	8
Staphylococcus aureus, mecA	1
Staphylococcus epidermidis, mecA	4
MecA	3
Coagulase-negative staphylococci	2
Staphylococcus epidermidis	1
Streptococcus agalactiae	2
Streptococcus dysgalactiae subspecies equisimilis	2
Streptococcus pneumoniae	1
Serratia marcescens	1
Escherichia coli	1
Enterobacter cloacae	1
Staphylococcus aureus, coagulase-negative staphylococci, mecA	1
Staphylococcus epidermidis, mecA, Enterococcus faecalis	1
Coagulase-negative staphylococci, Enterococcus faecium	1
Staphylococcus epidermidis, mecA, Enterococcus faecalis, Enterobacter cloacae	1
Negative	7
No prosthetic joint infection according to MSIS criteria (n = 23)
Enterobacteriaceae	3
Klebsiella pneumoniae and Enterococcus casseliflavus	1
Acinetobacter baumannii, Klebsiella pneumoniae, and Staphylococcus epidermidis	1
Staphylococcus epidermidis and mecA	1
Negative	17

MSIS: the Musculosceletal Infection Society;

mecA: the methicillin-resistance gene.

Table 3. Culture results in 61 patients with suspected prosthetic joint infection

Bacteria	No. of patients
Prosthetic joint infection fulfilling MSIS criteria (n = 38)
Staphylococcus aureus	8
Staphylococcus epidermidis	6
Staphylococcus lugdunensis	3
Coagulase-negative staphylococci	1
Streptococcus agalactiae	2
Group G betahemolytic streptococci ^a	2
Serratia marcescens	1
Escherichia coli	1
Staphylococcus epidermidis and Enterococcus faecalis	1
Staphylococcus epidermidis and Streptococcus viridans ^b	1
Staphylococcus aureus and Staphylococcus epidermidis	1
Enterobacter cloacae, Enterococcus faecalis, Citrobacter	1
Negative	10
No prosthetic joint infection according to MSIS criteria (n = 23)
Staphylococcus epidermidis	1
Negative	22

^a Group G betahemolytic streptococci includes Streptococcus dysgalactiae subspecies equisimilis detected by PCR.

^b Streptococcus viridans was not included in the pathogen panel of the PCR assay.

MSIS: The Musculosceletal Infection Society.

Table 4. Results of PCR and microarray assay and of culture compared against the diagnosis of prosthetic joint infection according to the Musculoskeletal Infection Society (MSIS) criteria, from 61 patients with suspected prosthetic joint infections

	PCR +	PCR –	Total
MSIS criteria +	31	7	38
Culture +	26	2
Culture –	5	5
MSIS criteria –	6	17	23
Culture +	1	0
Culture –	5	17
Total	37	24	61

Table 5. Comparison of the effect of previous antimicrobial treatment and its length with culture results and PCR and microarray assay results from 15 prosthetic joint infections fulfilling the Musculoskeletal Infection Society criteria

Length of antimicrobial treatment	PCR		Culture
	+	–	+	–
Up to 3 days	5	1	6	0
4 days or more	6	3	2	7
Total	11	4	8	7