Daptomycin is a novel bactericidal agent active against Gram-positive pathogens including meticillin-resistant Staphylococcus aureus (MRSA). Our case is unique in the description of an MRSA USA 300 isolate that developed decreased susceptibility to daptomycin during daptomycin and vancomycin therapy. Directed sequencing detected a previously reported mutation in mprF, resulting in a T345A substitution, associated with non-susceptibility to daptomycin. Case reportA 40-year-old white male with a previous history of intravenous drug abuse and hepatitis C was admitted to a local hospital for fever and shortness of breath. He was empirically treated with intravenous vancomycin (1 g i.v. q.12 h) starting 11/11/2006 (dates in American format throughout). The first set of blood cultures drawn on the day of admission turned positive after 12 h incubation. A subsequent transoesophageal echocardiogram showed native aortic valve endocarditis.The first set of blood cultures grew meticillin-resistant Staphylococcus aureus (MRSA) with a vancomycin MIC of ¡2 mg ml 21 (Microscan; Dode-Behring). The patient had repeat blood cultures on 11/17/2006, which were persistently positive for MRSA (with blood cultures turning positive after 20 h incubation), after 5 days of vancomycin therapy. No serum vancomycin levels were available from the local hospital.Vancomycin was discontinued and intravenous daptomycin 6 mg kg 21 per day was started on 11/17/2006 at the local hospital. No baseline serum creatine phosphokinase level results were available. A computed tomography scan of the head to evaluate agitation revealed right temporal lesions, which were thought to be embolic in nature. The third set of repeat blood cultures dated 11/21/2006 also turned positive for MRSA after 12 h incubation.The patient was transferred to our facility on 11/24/2006 with persistent MRSA bacteraemia, aortic valve endocarditis and intracranial haemorrhagic septic emboli. On examination, he was found to be tachypnoeic and in moderate respiratory distress with a respiratory rate of 44 min 21 , pulse 131 beats min 21 , blood pressure 135/ 83 mmHg, temperature 37 u C and weight of 176 lbs. Laboratory results showed a white blood cell count of 2200 cells ml 21 , with 86 % polymorphonuclear leukocytes; a platelet count of 73 000 cells ml 21 ; blood urea nitrogen level of 52 mg dl 21 ; creatinine level of 2.2 mg dl 21 (baseline creatinine 1.4); and bicarbonate level of 14 mg dl 21 . His estimated creatinine clearance was 47.5 ml min 21 at the time of transfer.Chest X-ray showed a mild cardiomegaly with bilateral oedema and basilar opacities. The patient was later intubated for respiratory distress and airway protection. Review of the blood culture and susceptibility testing results (11/11, 11/17, 11/21) from the local hospital revealed that the MRSA isolates were susceptible to vancomycin with an MIC of ¡2 mg ml 21 . Daptomycin therapy was discontinued on the day of transfer, and vancomycin (15 mg kg 21 i.v. q.12 h) and gentamicin (1 mg kg 21 i.v. q.24 h) were initia...

g Hepatitis C virus (HCV) causes chronic hepatitis, cirrhosis, and liver cancer. cis-acting RNA elements of the HCV genome are critical for translation initiation and replication of the viral genome. We hypothesized that the coding regions of nonstructural proteins harbor enhancer and essential cis-acting replication elements (CRE). In order to experimentally identify new cis RNA elements, we utilized an unbiased approach to introduce synonymous substitutions. The HCV genome coding for nonstructural proteins (nucleotide positions 3872 to 9097) was divided into 17 contiguous segments. The wobble nucleotide positions of each codon were replaced, resulting in 33% to 41% nucleotide changes. The HCV genome containing one of each of 17 mutant segments (S1 to S17) was tested for genome replication and infectivity. We observed that silent mutations in segment 13 (S13) (nucleotides [nt] 7457 to 7786), S14 (nt 7787 to 8113), S15 (nt 8114 to 8440), S16 (nt 8441 to 8767), and S17 (nt 8768 to 9097) resulted in impaired genome replication, suggesting CRE structures are enriched in the NS5B region. Subsequent high-resolution mutational analysis of NS5B (nt 7787 to 9289) using approximately 51-nucleotide contiguous subsegment mutant viruses having synonymous mutations revealed that subsegments SS8195-8245, SS8654-8704, and SS9011-9061 were required for efficient viral growth, suggesting that these regions act as enhancer elements. Covariant nucleotide substitution analysis of a stem-loop, JFH-SL9098, revealed the formation of an extended stem structure, which we designated JFH-SL9074. We have identified new enhancer RNA elements and an extended stem-loop in the NS5B coding region. Genetic modification of enhancer RNA elements can be utilized for designing attenuated HCV vaccine candidates.

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Newly developed assays that measure the production of cellular interferon gamma are useful diagnostic tools for the diagnosis of tuberculosis and may potentially replace or complement the tuberculin skin test in some circumstances. Importantly, interferon gamma release assays are more specific than tuberculin skin tests. Unfortunately the tests do not differentiate between active or latent infection. In addi