Transmission of HIV Drug Resistance and the Predicted Effect on Current First-line Regimens in Europe

Transmitted human immunodeficiency virus drug resistance in Europe is stable at around 8%. The impact of baseline mutation patterns on susceptibility to antiretroviral drugs should be addressed using clinical guidelines. The impact on baseline susceptibility is largest for nonnucleoside reverse transcriptase inhibitors.

Background. Numerous studies have shown that baseline drug resistance patterns may influence the outcome of antiretroviral therapy. Therefore, guidelines recommend drug resistance testing to guide the choice of initial regimen. In addition to optimizing individual patient management, these baseline resistance data enable transmitted drug resistance (TDR) to be surveyed for public health purposes. The SPREAD program systematically collects data to gain insight into TDR occurring in Europe since 2001.

Methods. Demographic, clinical, and virological data from 4140 antiretroviral-naive human immunodeficiency virus (HIV)–infected individuals from 26 countries who were newly diagnosed between 2008 and 2010 were analyzed. Evidence of TDR was defined using the WHO list for surveillance of drug resistance mutations. Prevalence of TDR was assessed over time by comparing the results to SPREAD data from 2002 to 2007. Baseline susceptibility to antiretroviral drugs was predicted using the Stanford HIVdb program version 7.0.

Results. The overall prevalence of TDR did not change significantly over time and was 8.3% (95% confidence interval, 7.2%–9.5%) in 2008–2010. The most frequent indicators of TDR were nucleoside reverse transcriptase inhibitor (NRTI) mutations (4.5%), followed by nonnucleoside reverse transcriptase inhibitor (NNRTI) mutations (2.9%) and protease inhibitor mutations (2.0%). Baseline mutations were most predictive of reduced susceptibility to initial NNRTI-based regimens: 4.5% and 6.5% of patient isolates were predicted to have resistance to regimens containing efavirenz or rilpivirine, respectively, independent of current NRTI backbones.

Conclusions. Although TDR was highest for NRTIs, the impact of baseline drug resistance patterns on susceptibility was largest for NNRTIs. The prevalence of TDR assessed by epidemiological surveys does not clearly indicate to what degree susceptibility to different drug classes is affected.

Evaluation of seven different enzyme-linked immunosorbent assays for serodiagnosis of Staphylococcus aureus bacteremia

OBJECTIVE

Serologic assays for Staphylococcus aureus antibodies were evaluated regarding their ability to differentiate between uncomplicated and complicated S. aureus bacteremia, between S. aureus and non-S. aureus bacteremia, and between S. aureus and non-S. aureus endocarditis.

METHODS

Enzyme-linked immunosorbent assays (ELISAs) were performed to measure Ig G antibodies against seven S. aureus antigens (peptidoglycan, teichoic acid, S. aureus ultrasonicate, whole S. aureus cells, alpha-toxin, lipase and capsular polysaccharide) in 129 patients with S. aureus bacteremia (including 51 with endocarditis), 78 patients with non-S. aureus bacteremia (including 27 with endocarditis) and 100 febrile non-bacteremic controls.

RESULTS

Whole-cell ELISA was the most sensitive assay. The specificity of all assays was low. Two different combinations of ELISAs for whole cells, teichoic acid,alpha-toxin, lipase and capsular polysaccharide did distinguish between S. aureus and non-S. aureus endocarditis, but not between uncomplicated and complicated S. aureus bacteremia.

Expression of collagen-binding protein and types 5 and 8 capsular polysaccharide in clinical isolates of Staphylococcus aureus

In vitro collagen binding of 216 Staphylococcus aureus isolates from patients with various diagnoses was studied. Polymerase chain reaction was used to examine these isolates regarding the existence of the corresponding cna gene. Distribution of capsular polysaccharide (CP) types was examined. Fifty-six (57%) of 99 S. aureus isolates from patients with endocarditis or bacteremic bone or joint infection were cna-positive compared with 65 (56%) of 117 isolates from bacteremic patients without signs of bone or joint infection (P = .99). There was a good correlation between in vitro collagen binding and presence of the cna gene. These data suggest that collagen binding is not a prerequisite for the development of endocarditis, osteomyelitis, or septic arthritis. There was no significant difference in the distribution of CP types among various patient groups, although there was a strong association between CP type 8 and the existence of the cna gene.

Antibody response to Staphylococcus aureus collagen binding protein in patients with S. aureus septicaemia and collagen binding properties of corresponding strains

An ELISA was developed for the detection of IgG antibodies to Staphylococcus aureus collagen binding protein (CnBP) in 95 patients with S. aureus endocarditis, complicated septicaemia with bone and joint involvement or uncomplicated septicaemia and in 95 control patients. Sixty percent of S. aureus-infected patients showed a positive peak anti-CnBP antibody level or a significant rise in titre, or both, during infection, but patients with S. aureus endocarditis or complicated septicaemia could not be differentiated from those with uncomplicated S. aureus septicaemia. The collagen binding capacity of S. aureus strains from 82 of the 95 patients was investigated in a particle agglutination assay and a 125I-labelled assay. All strains bound collagen in the particle agglutination assay as did 68% in the 125I-labelled assay, but there was no correlation between collagen binding of the patient strain and endocarditis, joint or skeletal involvement. An anti-CnBP antibody response was seen in 16 patients infected with a S. aureus strain negative for collagen binding in vitro, indicating in-vivo expression of CnBP.

Antibody response to Staphylococcus aureus whole cell, lipase and staphylolysin in patients with S. aureus infections

Three assays to measure antibodies against Staphylococcus aureus whole cells, lipase and staphylolysin were used to try to discriminate between complicated and uncomplicated S. aureus septicaemia. Sera were examined from 8 patients with S. aureus endocarditis, 23 patients with complicated S. aureus septicaemia, 12 patients with uncomplicated S. aureus septicaemia and 93 febrile non-septicaemic controls. No single assay could distinguish between complicated and uncomplicated S. aureus septicaemia. If the criterion for a positive result is defined as positive antibody level in the anti-lipase ELISA as well as in at least 1 of the other 2 assays, 10/31 patients with S. aureus endocarditis or complicated septicaemia were positive compared to 0/93 non-septicaemic patients and 0/12 patients with uncomplicated S. aureus septicaemia. Therefore, the combined use of serological assays in the diagnosis of complicated S. aureus septicaemia, one of which is the anti-lipase ELISA, is recommended.

Diagnosing Staphylococcus aureus endocarditis by detecting antibodies against S. aureus capsular polysaccharide types 5 and 8

Consecutive serum samples from patients with Staphylococcus aureus endocarditis or septicemia or non-S. aureus endocarditis and febrile nonsepticemic controls were tested for antibodies against S. aureus capsular polysaccharide (CP) types 5 and 8 by ELISA. The upper normal antibody levels were defined as the upper 99.5% confidence limits of the values from the febrile controls. All available patient isolates were tested for the presence of CP type 5 or 8 (85% of the isolates expressed either serotype), and all five patients with S. aureus endocarditis had positive antibody levels against the corresponding serotype within the first 10 days of infection. Three other endocarditis patients lacked isolates for CP testing but two of these were positive. Positive antibody levels were found in 0 of 28 septicemia patients, in 1 of 12 non-S. aureus endocarditis patients, and in 3 of 37 febrile controls. Thus, testing for anti-CP 5 or 8 antibodies, especially together with CP serotyping of the patient's isolate, seems to provide important information in the differential diagnosis of endocarditis in patients with S. aureus septicemia.