Immunocompromised people who are infected by B. microti are at risk of persistent relapsing illness. Such patients generally require antibabesial treatment for >or=6 weeks to achieve cure, including 2 weeks after parasites are no longer detected on blood smear.

BackgroundAt a time when the molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) was changing, we sought to characterize several genotypic markers and glycopeptide susceptibility features of clinical isolates from patients with bacteraemia.MethodsOne hundred and sixty-eight MRSA bloodstream isolates obtained from three multicentre clinical trials were microbiologically and genotypically characterized.ResultsAll isolates were susceptible to vancomycin (MIC ≤ 2 mg/L); 38% belonged to accessory gene regulator (agr) group I, 52% belonged to group II and 10% belonged to group III. Typing of the staphylococcal cassette chromosome mec (SCCmec) showed that 67% were type II and 33% were type IV. The agr group II polymorphism was associated with SCCmec II (P < 0.001). Fifty-three percent of SCCmec II and 27% of SCCmec IV isolates had vancomycin MICs ≥1 mg/L (P = 0.001). One hundred percent of agr II strains were predicted to be members of clonal complex 5. SCCmec II was the genetic marker most predictive of vancomycin MICs of ≥1 mg/L. SCCmec IV isolates were more likely to have vancomycin MICs ≤0.5 mg/L.ConclusionsGiven that SCCmec IV is a marker for a community-based organism for which less prior vancomycin exposure is predicted, we conclude that prior antibiotic exposure in agr group II organisms may account for their increased vancomycin MICs.

In a recent landmark trial of bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA) isolates, vancomycin MICs were >1 g/ml for only 16% of the isolates, and accessory gene regulator (agr) function as measured by delta-hemolysin activity was absent or reduced in only 28.1% of the isolates. This clinical study did not capture a population of MRSA isolates predictive of vancomycin treatment failure.Methicillin-resistant Staphylococcus aureus (MRSA) isolates with higher vancomycin MICs (Ͼ1 g/ml), reduced vancomycin bactericidal activity in vitro (5, 13), and attenuated agr function (1) have been associated with reduced vancomycin efficacy in bacteremia. Clinical studies targeting bacteremia caused by MRSA with these properties would be important to define the practical role of newer antimicrobials. We evaluated the properties of MRSA isolates from a recent study demonstrating the noninferiority of daptomycin compared to standard therapy in cases of S. aureus bacteremia and endocarditis (2).Eighty-nine baseline MRSA isolates from the previously published study comparing standard therapy (vancomycin plus low-dose gentamicin for the first 4 days) to daptomycin in MRSA bacteremia and endocarditis were analyzed (87 of 89 isolates were analyzed genotypically) (2).Vancomycin susceptibility testing was confirmed by CLSI broth microdilution methods. Susceptibility to other antimicrobials was performed by Cubist Pharmaceuticals as part of the prior study (2). agr function was determined semiquantitatively using delta-hemolysin activity as previously described (12). The genotype and staphylococcal cassette chromosome mec (SCCmec) type was determined by previously published PCR methods (3, 6, 11). spa X-repeat polymorphisms were determined by nucleotide sequencing as described previously (7,11). spa types were compared with results from previous studies (11) and with the Ridom spa server (4) to provisionally assign isolates to multilocus sequence typing-defined clonal complexes (CCs). Clonal complex 1 (CC1) equaled spa types 131 and 950; CC5 equaled spa types 2, 12, 23, 47, 65, 203, 302, 385, 402, and 437; CC8 equaled spa types 1, 4, 7, 363, and 954; CC30 equaled spa types 16 and 19; CC45 equaled spa types 15, 756, 951, and 953; CC59 spa equaled types 17 and 206. Note that four new spa types are included above as follows: spa types 950 (UJJJFFKBPE), 951 (XE3BMBKB), 953 (XE3BBKB), and 954 (YHGCO).

We describe the case of a 46-year-old resident of New York City with a one-year history of frequent urination and 3 weeks of undulating fevers. He also had liver and bone marrow abnormalities where a non-culturable Gram-negative rod was identified. Q fever was suspected and confirmed based on highly elevated phase I and II serum IgM/IgG antibodies against Coxiella burnetii.