High Coxiella burnetii DNA load in serum during acute Q fever is associated with progression to a serologic profile indicative of chronic Q fever.

PCR is very effective in diagnosing acute Q fever in the early stages of infection, when bacterial DNA is present in the bloodstream but antibodies have not yet developed. The objective of this study was to further analyze the diagnostic value of semiquantitative real-time PCR (qPCR) in diagnosing acute Q fever in an outbreak situation. At the Jeroen Bosch Hospital, in 2009, qPCR testing for Coxiella burnetii DNA was performed for 2,715 patients suspected of having acute Q fever (positive, n = 385; negative, n = 2,330). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the qPCR assay were calculated for patients with negative qPCR results with a follow-up sample obtained within 14 days (n = 305) and qPCR-positive patients with at least one follow-up sample (n = 369). The correctness of the qPCR result was based on immunofluorescence assay results for samples submitted for qPCR and follow-up testing. The sensitivity of the Q fever qPCR assay was 92.2%, specificity 98.9%, PPV 99.2%, and NPV 89.8%. Patients who later developed serologic profiles indicative of chronic Q fever infection had significantly higher C. burnetii DNA loads during the acute phase than did patients who did not (P < 0.001). qPCR testing is a valuable tool for the diagnosis of acute Q fever and should be used in outbreak situations when the onset of symptoms is <15 days earlier. Special attention is needed in the follow-up monitoring of patients with high C. burnetii DNA loads during the acute phase, as this might be an indicator for the development of a serologic profile indicative of chronic infection.

Real-time PCR to distinguish livestock-associated (ST398) from non-livestock-associated (methicillin-resistant) Staphylococcus aureus.

BACKGROUND: The Netherlands is one of the most densely populated countries in the world, with extensive livestock of pigs. In 2005, the emergence of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) was a fact, with a relatively high MRSA colonisation among pig farmers. These MRSA isolates mostly belonged to sequence type 398 (ST398). Compared to hospital-associated MRSA (HA-MRSA), severe infections due to LA-MRSA and transmission between individuals are still relatively rare. Therefore, LA-MRSA may warrant less stringent containment measures than HA-MRSA in hospital settings. RESULTS: The aim of this study was to develop a rapid diagnostic tool to distinguish LA-MRSA from non-LA-MRSA in aid of infection control. Here, we show that ST398 strains can be readily detected with real-time polymerase chain reaction (PCR). Analysis of a large panel of related and unrelated microorganisms confirmed that the real-time ST398 PCR (ST398-qPCR) assay does not cross-react with other microorganisms or with non-LA-S. aureus strains. ST398-qPCR analysis of MRSA isolates collected in 2010, 2011 and 2012 at the Jeroen Bosch Hospital (n = 275) showed that an average of 78 % of MRSA belonged to sequence type ST398. CONCLUSION: We conclude that the ST398 real-time PCR is a reliable assay to detect LA-S. aureus and anticipate that the use of this assay can prevent the unnecessary closing of hospital wards, which may lead to substantial savings for the health care system.

Legionella pneumophila DNA in serum samples during Legionnaires' disease in relation to C-reactive protein levels.

Legionella pneumophila DNA can be detected in serum from patients with Legionnaires' disease (LD). We explored this observation studying the kinetics of L. pneumophila DNA in serum samples in relation to C-reactive protein (CRP). Eleven hospitalized patients with LD were studied. Diagnosis was made by Legionella urinary antigen test in 8 patients and seroconversion in 3 patients. A macrophage infectivity potentiator (MIP) real-time PCR was performed on 31 serum samples, including 20 follow-up serum samples. Serum samples obtained on the day of admission were MIP PCR-positive in 7 (64%) and MIP PCR-negative in 4 (36%) patients. Three (75%) of the 4 patients with a MIP PCR-negative serum sample on the day of admission became positive during follow-up. Overall, L. pneumophila DNA was detected in serum samples from 10 of the 11 patients (91%). CRP levels in the 7 patients with a positive MIP PCR serum sample on day of admission (499 +/- 144 mg/l; median +/- SD) were significantly higher than those in the 4 patients with a negative MIP PCR serum sample on the day of admission (244 +/- 97 mg/l). No difference in the severity of the disease on the day of admission was found between these patients. The presence of L. pneumophila DNA in serum is a common phenomenon in hospitalized patients with LD, although in some cases it is not yet present on the day of admission. L. pneumophila DNA in serum on the day of admission correlates with high CRP levels, but not with the severity of the disease.