[Show abstract][Hide abstract] ABSTRACT: The etiological diagnosis of prosthetic joint infection (PJI) requires the isolation of microorganisms from periprosthetic samples. Microbiological cultures often yield false-positive and false-negative results. 16S rRNA gene PCR combined with sequencing (16SPCR) has proven useful for diagnosing various infections. We performed a prospective study to compare the utility of this approach with that of culture to diagnose PJI using intraoperative periprosthetic samples. We analyzed 176 samples from 40 patients with PJI and 321 samples from 82 noninfected patients using conventional culture and 16SPCR. Three statistical studies were undertaken following a previously validated mathematical model: sample-to-sample analysis, calculation of the number of samples to be studied, and calculation of the number of positive samples necessary to diagnose PJI. When only the number of positive samples is taken into consideration, a 16SPCR-positive result in one sample has good specificity and positive predictive value for PJI (specificity, 96.3%; positive predictive value, 91.7%; and likelihood ratio [LR], 22), while 3 positive cultures with the same microorganism are necessary to achieve similar specificity. The best combination of results for 16SPCR was observed when 5 samples were studied and the same microorganism was detected in 2 of them (sensitivity, 94%; specificity, 100%; and LR, 69.62). The results for 5 samples with 2 positive cultures were 96% and 82%, respectively, and the likelihood ratio was 1.06. 16SPCR is more specific and has a better positive predictive value than culture for diagnosis of PJI. A positive 16SPCR result is largely suggestive of PJI, even when few samples are analyzed; however, culture is generally more sensitive.
[Show abstract][Hide abstract] ABSTRACT: Ventilator-associated pneumonia is the most frequently observed nosocomial infection in intensive care units, and it is associated with high morbidity and mortality. Early microbiological diagnosis and the initial administration of appropriate antimicrobial therapy are associated with decreased mortality and potentially reduced costs. Our study evaluates the clinical and financial impact of performing rapid antimicrobial susceptibility tests directly on samples obtained from the lower respiratory tract.
A prospective, randomized study was performed over a 2-year period. Patients who had a lower respiratory tract infection that was acquired during mechanical ventilation and for whom samples obtained from the respiratory tract were sent for culture were randomized to 1 of 2 groups. Samples were cultured for the control group, and results were reported using standard procedures. Samples were also cultured for the test subject group using standard procedures, but in addition, a rapid antibiogram was immediately performed by placing E-test antibiotic strips (AB Biodisk) directly on respiratory tract samples. Patients in the E-test group received a preliminary laboratory report when it became available. The 2 patient groups were compared according to the following variables: type and severity of underlying conditions, total days of antimicrobial use, number of defined daily doses, cost of acquisition of the antimicrobial agent per episode, days of fever, days receiving mechanical ventilation, days in the intensive care unit, incidence of Clostridium difficile-associated diarrhea, and mortality.
Reporting a rapid E-test was associated with fewer days of fever, fewer days of antibiotic administration until resolution of the episode of ventilator-associated pneumonia, decreased antibiotic consumption, less C. difficile-associated diarrhea, lower costs of antimicrobial agents, and fewer days receiving mechanical ventilation.
A rapid E-test of respiratory tract samples improves antimicrobial use in cases of ventilator-associated pneumonia.
[Show abstract][Hide abstract] ABSTRACT: Background: Orthopaedic infection related to joint prosthesis deserves special efforts from a multidisciplinary team. Despite effective culture methods, some cases with low-grade or “nonculturable” infections still present a challenge. We investigate the value of a polymerase chain reaction (PCR) test in the diagnosis of patients with prosthetic joint infections (PJI).
Methods: From July 2004 through April 2005, a total of 34 cases which had undergone prosthetic joint surgery were investigated. There were 10 cases of PJI, defined by standard methods (clinical, histological and microbiological). Intra-operative biopsy samples obtained from the neocapsule and the interface membrane were examined by means of routine culture methods and by universal PCR for detection of the 16S ribosomal RNA gene. Control subjects included 24 cases (18 undergoing primary joint surgery and 6 undergoing a revision arthroplasty). We also evaluated age, sex, co-morbidity factors, timing and site of infection, etiology, and treatment. The follow-up period was between 3-9 months.
Results: The case group consisted of 8 women and 2 men, mean age 70.9 years (range 40-81). There were 7 early PJI and 3 late PJI. The hip was involved in 8 cases and the knee in 2 cases. The control group included 11 women and 13 men, mean age 65.8 years (range 38-91). PCR was positive in 7 out of 10 infected cases detected by routine cultures. There was complete agreement between the 7 positive results obtained by both methods (3 MSSA; 1 E. faecalis; 1 S. viridans; 1 Morganella sp.; 1 MRSA+E.faecalis). The 3 missing infections were 1 monomicrobial infection caused by SBGA and 2 polymicrobial. PCR showed no microorganisms in the control group (in both primary and revision arthroplasty) but culture was positive in 8 cases of the control group (SCN). Thus, globally, PCR had a sensitivity of 70%; specificity of 100%; a positive predictive value of 100% and a negative predictive value of 88.8%.
Conclusion: Our preliminary experience shows us that PCR is a useful tool in the differential diagnosis of prosthetic joint infections, despite a lower sensitivity than expected. The study is ongoing for a new analysis after a follow-up of 15 months.
Infectious Diseases Society of America 2005 Annual Meeting; 10/2005