Michiel A. van Agtmael

New developments in the diagnosis of bloodstream infections

New techniques have emerged for the detection of bacteria in blood, because the blood culture as gold standard is slow and insufficiently sensitive when the patient has previously received antibiotics or in the presence of fastidious organisms. DNA-based techniques, hybridisation probes, and PCR-based detection or protein-based detection by mass spectroscopy are aimed at rapid identification of bacteria and provide results within 2 h after the first signal of growth in conventional blood cultures. Also, detection of microorganisms directly in blood by pathogen-specific or broad-range PCR assays (eubacterial or panfungal) shows promising results. Interpretation is complex, however, because of detection of DNA rather than living pathogens, the risk of interfering contamination, the presence of background DNA in blood, and the lack of a gold standard. As these techniques are emerging, clinical value and cost-effectiveness have to be assessed. Nevertheless, molecular assays are expected eventually to replace the current conventional microbiological techniques for detection of bloodstream infections.

Artemisinin drugs in the treatment of malaria: from medicinal herb to registered medication

Registration in Europe of several artemisinin drugs for the treatment of malaria can soon be expected. Artemisinin is isolated from the herb Artemisia annua, in use in China more than 2000 years as a herbal tea against fever. Artemisinin drugs are being used extensively in South-East Asia and increasingly in Africa. Active derivatives have been synthesized - artemether, arteether and artesunate - which are used for oral, intramuscular, rectal and intravenous administration. The origin, mechanism of action, efficacy and safety in patients, the pharmacokinetics and the position of this group of compounds among existing antimalarials are discussed in this review.

Increase in HCV incidence among men who have sex with men in Amsterdam most likely caused by sexual transmission

We retrospectively screened 1836 men who have sex with men (MSM) participating in the Amsterdam Cohort Studies (1984-2003) for hepatitis C virus (HCV) antibodies. HCV incidence was 0.18/100 person-years (PY) in human immunodeficiency virus (HIV)-positive MSM (8/4408 PY [95% confidence interval {CI}, 0.08-0.36]) but was 0/100 PY in MSM without HIV (0/7807 PY [95% CI, 0.00-0.05]). After 2000, HCV incidence among HIV-positive men increased 10-fold to 0.87/100 PY (5/572 PY [95% CI, 0.28-2.03]). Additional hospital cases (n=34) showed that MSM in Amsterdam who acquired HCV infection after 2000 reported high rates of ulcerative sexually transmitted infections (59%) and rough sexual techniques (56%), denied injection drug use, and were infected mainly with the difficult-to-treat HCV genotypes 1 (56%) and 4 (36%). Phylogenetic analysis showed 3 monophyletic clusters of MSM-specific HCV strains. The emergence of an MSM-specific transmission network suggests that HIV-positive MSM with high-risk sexual behaviors are at risk for sexually acquired HCV. Targeted prevention and routine HCV screening among HIV-positive MSM is needed to deter the spread of HCV.

HIV monotherapy with ritonavir-boosted protease inhibitors: a systematic review

Objective:To assess the efficacy of ritonavir-boosted protease inhibitor monotherapy. Design and methods:Systematic review of all protease inhibitor-monotherapy studies published in peer-reviewed journals or presented at conferences to date. Data of randomized controlled trials were pooled to yield common odds ratios. Results:Twenty-two protease inhibitor-monotherapy studies were identified. In the intent-to-treat analysis, 395 out of 582 (67.9%) patients had undetectable HIV-RNA at the end of follow-up. In the six randomized controlled trials (all lopinavir/ritonavir monotherapy), the risk of therapy failure was greater on monotherapy: 121 out of 364 (33.2%) patients on monotherapy against 64 out of 280 (22.9%) patients on HAART [pooled odds ratio 1.48 (95% confidence interval 1.02–2.13, P = 0.037)]. Regarding patients with successfully resuppressed HIV-RNA upon (re-)introducing nucleoside reverse transcriptase inhibitors (NRTIs) as nonfailures, the risk of therapy failure was comparable: 98 out of 364 (26.9%) against 64 out of 280 (22.9%) patients [odds ratio 1.05 (95% confidence interval 0.72–1.53, P = 0.81)]. Conclusion:The overall efficacy of ritonavir-boosted protease inhibitor monotherapy is inferior to HAART. The efficacy improves in patients started on monotherapy after suppressed HIV-RNA for at least 6 months. Ten percent of patients have viral rebound with HIV-RNA levels between 50 and 500 copies/ml. Possible explanations are lack of HIV suppression in particular cells or compartments, alternative resistance mechanisms, and nonadherence. Once proven that reintroduction of NRTIs, in patients with loss of viral suppression, is safe and effective, a broader use of simplification of HAART to protease inhibitor monotherapy might be justified. This review supports that the majority of patients with prolonged viral suppression on HAART can successfully be treated with protease inhibitor monotherapy. Arguments for this strategy are NRTI/NNRTI side effects, NRTI/NNRTI resistance, and costs.

First line zidovudine/lamivudine/lopinavir/ritonavir leads to greater bone loss compared to nevirapine/lopinavir/ritonavir.

Objective:We studied changes in bone mineral density (BMD) and bone turnover after initiation of combination antiretroviral therapy (cART) and the contribution of zidovudine/lamivudine (ZDV/3TC) in particular. Design:Randomized clinical trial comparing lopinavir/ritonavir(LPV/r) + ZDV/3TC with LPV/r + nevirapine (NVP) in 50 cART-naive men. Methods:Dual energy X-ray absorptiometry (DXA) and quantitative computed tomography scans (QCT) were performed at baseline and 3, 12, and 24 months after cART initiation. Serum 25-hydroxy-vitamin D3, parathyroid hormone (PTH), osteocalcin, and urine deoxypyridinoline (DPD)/creatinine ratio were measured. Results:BMD decreased rapidly in both femoral neck and lumbar spine after cART initiation. BMD loss during 24 months measured by DXA, but not by QCT, was greater in the ZDV/3TC/LPV/r group compared to the NVP/LPV/r group [femoral neck: −6.3% ± 1.0% (P < 0.0001) compared to −2.3% ± 0.9% (P = 0.01), between-group P = 0.0006); lumbar spine: −5.1% ± 0.8% (P < 0.0001) compared to −2.6% ± 0.7% (P = 0.0006), between-group P = 0.07]. Osteocalcin [+1.60 ± 0.32 (P < 0.0001) and +1.81 ± 0.29 (P < 0.0001) nmol/l] and the urine DPD/creatinine ratio [+1.35 ± 0.44 (P = 0.0029) and +1.19 ± 0.38 nmol/mmol (P = 0.0024)] increased in both groups over 24 months, with no significant difference between groups. PTH increased to a greater degree in the NVP/LPV/r group [+2.0 ± 0.31 pmol/l (P < 0.0001)] compared to [+0.81 ± 0.33 pmol/l (P = 0.021) in the ZDV/3TC/LPV/r group]. Conclusion:BMD in both femoral neck and lumbar spine decreased rapidly after initiation of cART, in parallel to an increase in bone turnover. The greater bone loss in the ZDV/3TC/LPV/r group compared to the NVP/LPV/r group suggests that ZDV/3TC contributes to this process. The PTH increase does not explain this greater bone loss.

Faster Identification of Pathogens in Positive Blood Cultures by Fluorescence In Situ Hybridization in Routine Practice

ABSTRACT Rapid identification of microorganisms in blood cultures is required to optimize empirical treatment at an early stage. Fluorescence in situ hybridization (FISH) can reduce the time to identification of microorganisms in growth-positive blood cultures. In this study, we evaluated the performance, time to identification, and potential clinical benefits of FISH compared to those of conventional culture methods in routine practice. After Gram staining, blood culture fluids were simultaneously further identified with FISH and with conventional culture methods. Results and points in time of FISH and culture identification (provisional and final identifications) were collected and compared. For 91% of microorganisms, the genus or family name was identified, and for 79%, the species name could be attributed. The sensitivity and specificity of the individual probes exceeded 95%, except for the Enterobacteriaceae probe (sensitivity, 89%). Cross-hybridization was obtained with the Klebsiella pneumoniae probe for Klebsiella oxytoca. The time gains of FISH and final culture identification were more than 18 h for bacteria and 42 h for yeasts. With FISH, Staphylococcus aureus was differentiated from coagulase-negative staphylococci 1.4 h faster than by provisional identification (P < 0.001). In conclusion, FISH allows rapid and reliable identification of the majority of microorganisms in growth-positive blood cultures. The substantial time gain of identification with FISH may allow same-day adjustment of antimicrobial therapy, and FISH is especially useful if no provisional identification is obtained. With further extension of the number of probes and a reduction in turnaround time, FISH will become a very useful diagnostic tool in the diagnosis of bloodstream infections.

Carotid intima-media thickness and arterial stiffness in HIV-infected patients: the role of HIV, antiretroviral therapy, and lipodystrophy

Objectives:HIV-infected patients using combination antiretroviral therapy (ART) have an increased cardiovascular risk. We aimed to identify the effects of HIV, ART, and lipodystrophy (LD) on carotid artery intima-media thickness (C-IMT), a surrogate measure of atherosclerosis, and arterial stiffness, a marker of cardiovascular risk. Design:Case-control study of 77 HIV-infected men (55 exposed to ART, 22 ART naive, and 23 with LD) and 52 controls. Methods:C-IMT was measured ultrasonically, and arterial stiffness was estimated by distensibility (DC) and compliance (CC) coefficients of the carotid, femoral, and brachial arteries, by the carotid Young elastic modulus and pulse wave velocity. Results:After adjustment for cardiovascular risk factors, HIV-infected patients had a 0.067 mm (10.8%) greater C-IMT than controls, 13.6% and 29.5% lower DC, and 14.1% and 31% lower CC of the carotid and femoral arteries, respectively, but similar Young elastic modulus and pulse wave velocity. Patients exposed to ART had similar C-IMT compared with ART-naive patients but 25.9% lower DC and 21.7% lower CC of the femoral artery. Arterial properties did not differ between patients with and without LD. Conclusions:HIV infection is independently associated with C-IMT and generally increased arterial stiffness. ART use is associated with increased stiffness of the femoral artery.

Zidovudine/lamivudine contributes to insulin resistance within 3 months of starting combination antiretroviral therapy

Background:Patients with antiretroviral therapy (ART)-associated lipodystrophy frequently have disturbances in glucose metabolism associated with insulin resistance. It is not known whether changes in body composition are necessary for the development of these disturbances in ART-naive patients starting treatment with different combination ART regimens. Methods:Glucose metabolism and body composition were assessed before and after 3 months of ART in a prospective randomized clinical trial of HIV-1-positive ART-naive men taking lopinavir/ritonavir within either a nucleoside reverse transcriptase inhibitor (NRTI)-containing regimen (zidovudine/lamivudine; n = 11) or a NRTI-sparing regimen (nevirapine; n = 9). Glucose disposal, glucose production and lipolysis were measured after an overnight fast and during a hyperinsulinaemic–euglycaemic clamp using stable isotopes. Body composition was assessed by computed tomography and dual-energy X-ray absorptiometry. Results:In the NRTI-containing group, body composition did not change significantly in 3 months; insulin-mediated glucose disposal decreased significantly (25%; P < 0.001); and fasting glycerol turnover increased (22%; P < 0.005). Hyperinsulinaemia suppressed glycerol turnover equally before and after treatment. The disturbances in glucose metabolism were not accompanied by changes in adiponectin or other glucoregulatory hormones. In contrast, glucose metabolism did not change in the NRTI-sparing arm. Glucose disposal significantly differed over time between the arms (P < 0.01). Conclusions:Treatment for 3 months with a NRTI-containing, but not a NRTI-sparing, regimen resulted in a 25% decrease in insulin-mediated glucose disposal and a 22% increase in fasting lipolysis. In the absence of discernable changes in body composition, NRTI may directly affect glucose metabolism, the mechanism by which remains to be elucidated.

Streptococcus pneumoniae DNA Load in Blood as a Marker of Infection in Patients with Community-Acquired Pneumonia

ABSTRACT Direct detection of Streptococcus pneumoniae DNA in blood adds to culture results in the etiological diagnosis of patients with community-acquired pneumonia (CAP). Quantification of the amount of DNA, the bacterial DNA load (BDL), provides a measurement of DNAemia that may increase the understanding of the clinical relevance of S. pneumoniae DNA in blood. We evaluated the S. pneumoniae BDL as a diagnostic tool in adult patients with CAP. The BDL was determined in whole-blood samples collected simultaneously with blood for culture from 45 adult patients with CAP. After DNA extraction, S. pneumoniae DNA was detected with specific real-time PCR amplification, and the BDL was calculated with a standard curve. PCR and microbiological results were compared, and the BDL was related to clinical and laboratory parameters. S. pneumoniae DNA was detected in 10/13 patients with positive blood cultures and in 67% of patients with microbiologically confirmed pneumococcal pneumonia. The positive predictive values of the receiver operating characteristic curves for the BDLs for pneumococcal infection (100%) and pneumococcal bacteremia (69%) were higher than those for the level of C-reactive protein (CRP; 43% and 23%, respectively) and the white blood cell count (WBC; 42% and 35%, respectively); the negative predictive values of these three parameters were in the same range (±90 and ±97%, respectively). The BDL was higher in patients presenting with systemic inflammatory response syndrome and in patients with bacteremia. Positive correlations were observed for the BDL with WBC, CRP level, and length of stay. We conclude that the BDL supports the diagnosis of S. pneumoniae infection in patients with CAP and provides a putative marker of the severity of disease.

Quantitative Detection of Staphylococcus aureus and Enterococcus faecalis DNA in Blood To Diagnose Bacteremia in Patients in the Intensive Care Unit

ABSTRACT Direct detection of bacterial DNA in blood offers a fast alternative to blood culture and is presumably unaffected by the prior use of antibiotics. We evaluated the performance of two real-time PCR assays for the quantitative detection of Staphylococcus aureus bacteremia and for Enterococcus faecalis bacteremia directly in blood samples, without prior cultivation. Whole-blood samples for PCR were obtained simultaneously with blood cultures from patients admitted to the intensive care unit of our hospital. After the extraction of DNA from 200 μl of blood, real-time PCR was performed for the specific detection and quantification of S. aureus and E. faecalis DNA. The sensitivity for bacteremia of the S. aureus PCR was 75% and that of the E. faecalis PCR was 73%, and both tests had high specificity values (93 and 96%, respectively). PCR amplification reactions were positive for S. aureus for 10 (7%) blood samples with negative blood cultures, and 7 (4%) PCR reactions were positive for E. faecalis. The majority of these PCR results were likely (50%) or possibly (42%) related to infection with the specific microorganism, based on clinical data and radiological and microbiological investigations. PCR results were concordant for 95% of paired whole-blood samples, and blood culture results were concordant for 97% of the paired samples. We conclude that the detection of S. aureus and E. faecalis DNA in blood by real-time PCR enables a rapid diagnosis of bacteremia and that a positive DNAemia is related to proven or possible infection with the specific microorganism in the majority of patients with negative blood cultures.