A novel colorimetric assay was developed and validated for accurate quantitation of human immunodeficiency virus (HIV) DNA in peripheral blood mononuclear cells (PBMCs). We tested 318 sequential samples from 56 subjects, 53 of whom were undergoing dual or triple therapy. Patients were considered responders when viremia levels were below 5,000 HIV RNA copies/ml. The mean DNA copy numbers for untreated and responder subjects were similar (72 and 75, respectively), while it was 4.54-fold higher for nonresponders (339). This report provides strong evidence that HIV DNA levels in PBMCs correlate with therapeutic efficacy and suggests that DNA quantitation is a useful tool to monitor the decay of the HIV reservoir toward disease remission, especially when viremia is undetectable.

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Covert human immunodeficiency virus (HIV) replication was ongoing during the first 3 years of aviremia in 22 patients, as determined by detection of DNA containing two long terminal repeats (2LTR DNA). Although total HIV DNA was detected in 60 2LTR DNA-negative samples, the absence of 2LTR DNA in 90% of patients following 7 to 8 years of highly active antiretroviral therapy suggests suppression of cryptic viral replication.

The detection of HIV-1 proviral DNA in children born to seropositive mothers was studied using the polymerase chain reaction with either a radioactive electrophoretic method or a noval procedure that employs colorimetric microwell visualization. Peripheral blood mononuclear cell lysates from 18 HIV-1 infected children and 28 uninfected subjects were assayed for a 142 bp fragment of DNA from the gag region of HIV-1 using the primer pair SK145-431. Detection of amplified DNA was carried out by hybridization with a radiolabeled SK102 probe, or with a tagged SK102 probe permitting colorimetric detection. The radioactive detection procedure demonstrated 100% specificity and correlated with the serological results. The assay was more sensitive than the p24 antigen test, but two false negative results were obtained. One was from a sample taken at 2 weeks, an age at which undetectable provirus levels were reported in almost all HIV-1 infected newborns. The second was probably due to a low copy number of proviral DNA, as positive results were obtained in all other (6) samples from this child. Comparative analysis in a limited number of specimens of radioactive and colorimetric detection following PCR revealed 100% specificity and comparable sensitivity with 4 discordant results. The results show that PCR is the best method for early diagnosis of HIV-1 infection in pediatric subjects. The study also demonstrated the value of a colorimetric detection method for PCR products. This colorimetric microwell plate procedure may prove a useful technique in routine diagnosis of HIV-1 infection in children.

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a leading pathogen causing nosocomial infections. Many studies have shown that the restricted use of antibacterials is associated with a decline in resistance. To establish whether an intervention protocol designed to limit the use of cephalosporins can lower mRSA infection rates and impact on Gram-negative bacteria susceptibility in an intensive Care Unit (ICU), we conducted a prospective, non-randomized, before-after intervention study in an 18-bed ICU in Genoa, Italy. The intervention was a hospital antibiotic control policy and the observation was routine monitoring for nosocomial infections and antibiotic use, recording periodically the incidence density and MRSA prevalence. The intervention included a new antibiotic guideline that restricted the use of cephalosporins for all ICU inpatients. The analysis showed that the intervention determined a significant reduction in cephalosporin usage (-70.3%), while fluoroquinolones, mainly ciprofloxacin, increased after introduction of the antibiotic policy (+46.5%). A significant reduction in the percentage of MRSA infections (-30%) and heterogeneous susceptibility patterns in Klebsiella pneumoniae and Pseudomonas aeruginosa were noted.