INTRODUCTION:Imipenem‐resistant Pseudomonas aeruginosa resulting from metallo‐β‐lactamases has been reported to be an important cause of nosocomial infection and is a critical therapeutic problem worldwide, especially in the case of bacteremia.OBJECTIVES:To determine the frequency of metallo‐β‐lactamases among imipenem‐resistant Pseudomonas aeruginosa isolates and to compare methods of phenotypic and molecular detection.METHODS:During 2006, 69 imipenem‐resistant Pseudomonas aeruginosa samples were isolated from blood and tested for metallo‐β‐lactamase production using phenotypic methods. Minimal Inhibitory Concentratrions (MIC) (µg/mL) was determined with commercial microdilution panels. Pulsed Field Gel Electrophoresis (PFGE) was performed among metallo‐β‐lactamase producers.RESULTS:Of all the blood isolates, 34.5% were found to be imipenem‐resistant Pseudomonas aeruginosa. Positive phenotypic tests for metallo‐β‐lactamases ranged from 28%‐77%, and Polymerase Chain Reaction (PCR) were positive in 30% (of note, 81% of those samples were blaSPM‐1 and 19% were blaVIM‐2). Ethylenediamine tetracetic acid (EDTA) combinations for the detected enzymes had low kappa values; thus, care should be taken when use it as a phenotypic indicator of MBL. Despite a very resistant antibiogram, four isolates demonstrated the worrisome finding of a colistin MIC in the resistant range. PFGE showed a clonal pattern.CONCLUSION:Metallo‐β‐lactamases among imipenem‐resistant Pseudomonas aeruginosa were detected in 30.4% of imipenem‐resistant Pseudomonas aeruginosa isolates. This number might have been higher if other genes were included. SPM‐1 was the predominant enzyme found. Phenotypic tests with low kappa values could be misleading when testing for metallo‐β‐lactamases. Polymerase Chain Reaction detection remains the gold standard.

In KTx recipients, the occurrence of KPC-Kp-HAI was related to invasive devices and type of transplant; these infections had a high rate of recurrence and reduced survival after KTx.

This study evaluated Trypanosoma cruzi parasitemia in persons with chronic Chagas disease, compared the parasitemia in human immunodeficiency virus (HIV)-positive and -negative subjects, and, for HIV-positive subjects, analyzed the association between parasitemia and occurrence of acquired immunodeficiency syndrome-defining illnesses, CD4 cell counts, HIV loads, and antiretroviral therapy. In total, 110 adults with chronic Chagas disease (29 HIV positive, 81 HIV negative) were studied. T. cruzi parasitemia was evaluated by xenodiagnosis, blood culture, and direct microscopic examination of blood. T. cruzi parasitemia was detected significantly more frequently in HIV-positive than in HIV-negative subjects (odds ratio, 12.3; 95% confidence interval, 3.7-41.2). HIV-positive patients also had higher levels of parasitemia. No statistically significant association was seen between parasitemia and the variables of interest among the HIV-positive subjects.

BackgroundHIV-infected individuals have deficient responses to Yellow Fever vaccine (YFV) and may be at higher risk for adverse events (AE). Chronic immune activation–characterized by low CD4/CD8 ratio or high indoleamine 2,3-dioxygenase-1 (IDO) activity—may influence vaccine response in this population.MethodsWe prospectively assessed AE, viremia by the YFV virus and YF-specific neutralizing antibodies (NAb) in HIV-infected (CD4>350) and -uninfected adults through 1 year after vaccination. The effect of HIV status on initial antibody response to YFV was measured during the first 3 months following vaccination, while the effect on persistence of antibody response was measured one year following vaccination. We explored CD4/CD8 ratio, IDO activity (plasma kynurenine/tryptophan [KT] ratio) and viremia by Human Pegivirus as potential predictors of NAb response to YFV among HIV-infected participants with linear mixed models.Results12 HIV-infected and 45-uninfected participants were included in the final analysis. HIV was not significantly associated with AE, YFV viremia or NAb titers through the first 3 months following vaccination. However, HIV–infected participants had 0.32 times the NAb titers observed for HIV-uninfected participants at 1 year following YFV (95% CI 0.13 to 0.83, p = 0.021), independent of sex, age and prior vaccination. In HIV-infected participants, each 10% increase in CD4/CD8 ratio predicted a mean 21% higher post-baseline YFV Nab titer (p = 0.024). Similarly, each 10% increase in KT ratio predicted a mean 21% lower post-baseline YFV Nab titer (p = 0.009). Viremia by Human Pegivirus was not significantly associated with NAb titers.ConclusionsHIV infection appears to decrease the durability of NAb responses to YFV, an effect that may be predicted by lower CD4/CD8 ratio or higher KT ratio.

Abstract. Chronic Trypanosoma cruzi infection can reactivate in patients with immunosuppression related to human immunodeficiency virus (HIV) infection, resulting in severe meningoencephalitis or myocarditis and high parasitemia.

We evaluated the performance of several methods for the detection of methicillin resistance in Staphylococcus aureus using 101 clinical S. aureus isolates from pediatric patients in a tertiary hospital in Brazil; 50 isolates were mecA-positive and 51 were mecA-negative. The Etest and oxacillin agar screening plates were 100% sensitive and specific for mecA presence. Oxacillin and cefoxitin disks gave sensitivities of 96 and 92%, respectively, and 98% specificity. Alterations of CLSI cefoxitin breakpoints increased sensitivity to 98%, without decreasing specificity. Our results highlight the importance of a continuing evaluation of the recommended microbiological methods by different laboratories and in different settings. If necessary, laboratories should use a second test before reporting a strain as susceptible, especially when testing strains isolated from invasive or serious infections. With the new (2007) CLSI breakpoints, the cefoxitin-disk test appears to be a good option for the detection of methicillin resistance in S. aureus.

ART-treated HIV-infected individuals seem to have impaired and/or less durable responses to YFV than HIV-uninfected individuals, which were associated with lower CD4(+)/CD8(+) ratio, but not with CD4(+) T-cell count. These results supports the notion that low CD4(+)/CD8(+) ratio, a marker linked to persistent immune activation, is a better indicator of functional immune disturbance than CD4(+) T-cell count in patients with successful ART.

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