Use of real-time PCR and fluorimetry for rapid detection of rifampin and isoniazid resistance-associated mutations in Mycobacterium tuberculosis

Very fast amplification of DNA in small volumes can be continuously monitored with a rapid cycler that incorporates fluorimetric detection. Primers were designed to amplify a 157-bp fragment of the rpoB gene spanning codons 526 and 531 and a 209-bp fragment of the katG gene spanning codon 315 of Mycobacterium tuberculosis. Most mutations associated with resistance to rifampin (RMP) and isoniazid (INH) in clinical isolates occur in these codons. Two pairs of hybridization probes were synthesized; one in each pair was 3' labeled with fluorescein and hybridized upstream of the codon with the mutation; the other two probes were 5' labeled with LightCycler-Red 640. Each pair of probes recognized adjacent sequences in the amplicon. After DNA amplification was finished by using a LightCycler, the temperature at which the Red 640 probe melted from the product was determined in a 3-min melt program. Twenty M. tuberculosis clinical isolates susceptible to streptomycin, INH, RMP, and ethambutol and 36 antibiotic-resistant clinical M. tuberculosis isolates (16 resistant to RMP, 16 to INH, and 4 to both antimicrobial agents) were amplified, and the presence of mutations was determined using single-strand conformation polymorphism analysis, the LiQor automated sequencer, and the LightCycler system. Concordant results were obtained in all cases. Within 30 min, the LightCycler method correctly genotyped all the strains without the need of any post-PCR sample manipulation. Overall, this pilot study demonstrated that real-time PCR coupled to fluorescence detection is the fastest available method for the detection of RMP and INH resistance-associated mutations in M. tuberculosis clinical isolates.

Fast urinary screening for paracetamol using on-line microwave assisted hydrolysis and spectrophotometric detection

A fully automated urinary screening system for paracetamol and its metabolites is proposed. The method comprises on-line acid microwave assisted hydrolysis of the drug to p-aminophenol followed by reaction with o-cresol in alkaline medium. The indophenol blue dye formed can be continuously monitored at 620 nm. The detection limit achieved, 0.1 microgram ml-1, allows a high dilution of the samples, thus reducing potential interferences from the sample matrix (mainly protein degradation during urine hydrolysis). The proposed screening system also possesses an adequate selectivity, as the major interferent, epinephrine, is tolerated at concentrations higher than those that could be found in the positive urine samples. The reproducibility, expressed as relative standard deviation, was 3.0% and the sample frequency 20 h-1. The reliability of the method was established at five concentrations (between 0.5 and 4 times the detection limit). Finally, it was applied to the screening of several human urine samples. The results obtained were compared with those provided by batch acid hydrolysis, and were similar in all instances.

Warm ischemic time tolerance after ventilated non-heart-beating lung donation in piglets

OBJECTIVE

The availability of lungs for transplantation could be ameliorated with the use of organs retrieved from ventilated non-heart-beating donors (VNHBD). The aim of this work is to determine the limit to tolerable in situ warm ischemia time (WIT) for lung grafts after circulation is stopped.

METHODS

Twenty piglets underwent left lung allotransplantation. Animals were randomly allocated based on the donor's status before lung harvesting into the following study groups: Sham (n = 5), Heart-beating donors-non-warm ischemia; I-30 (n = 5), I-60 (n = 5) and I-90 (n = 5), VNHBD-WIT of 30, 60 and 90 min, respectively. Right pulmonary artery and bronchus were permanently occluded one hour after transplantation. Assessment of pulmonary function was monitored hourly by hemodynamic, oxygenation and pulmonary mechanic measurements during a period of 6 h after reperfusion. Lung grafts were weighed pre- and post-transplantation.

RESULTS

Cold ischemic time was similar for all groups, and averaged 80.1+/-2.7 min. Final mean lung weight was significantly greater in VNHBD (92.5+/-3.1 g vs. Sham values 75.6+/-2.4 g, P < 0.01). After right lung exclusion, hemodynamic changes consisted of a sustained increase in pulmonary vascular resistance and a reduction in cardiac output. Lung mechanics also modified, with a rise in airway resistance and a fall in compliance.

CONCLUSIONS

Post-transplantation lung graft function from VNHBD with up to 90 min of WIT, is equivalent to those achieved by grafts harvested after heart-beating donation. This method may be a promising strategy of increasing the pulmonary donor pool.

[Predictive factors of inotropic support in myocardial revascularization surgery]

OBJECTIVES

The use of perioperative inotropics in myocardial revascularization surgery can be considered a marker of ventricular dysfunction, the etiology of which involves a variety of pre- and intraoperative factors. Knowledge of the risk factors and their relative importance can allow them to be modified for improved outcome. This study aims to determine the incidence of and factors that predict the need for inotropic support in order to finalize extracorporeal circulation and in the first 6 hours after myocardial revascularization.

PATIENTS AND METHODS

Two hundred forty-two patients who underwent myocardial revascularization were studied retrospectively. The parameters collected were age, sex, NYHA classification, left ventricular telediastolic pressure at baseline and after contrast, ejection fraction, collateral circulation, number of distal anastomoses, time of clamping, time of extracorporeal circulation, need for inotropic support to end extracorporeal circulation and during the first 6 hours after surgery.

RESULTS

Inotropics were used in 27.6% of the sample. The need for inotropic support was related to female sex (odds ratio [OR] 3.85 with 95% confidence interval [CI], 1.56-9.49); NYHA class III (OR 2.13 with 95% CI, 1.05-4.32) or IV (OR 10.16 with 95% CI, 3.22-32.13); low injection fraction (OR 2.41 with 95% CI, 1.22-4.76); and prolonged extracorporeal circulation (OR 2.97 with 95% CI, 1.54-5.76).

CONCLUSIONS

The independent variables associated with the need for inotropic support during the perioperative period in myocardial revascularization are NYHA functional class III and IV, female sex, low injection fraction and prolonged extracorporeal circulation. New techniques for myocardial protection during extracorporeal circulation, plus adequate peroperative stabilization of patients and shorter time of extracorporeal circulation will probably diminish short term morbidity in revascularization surgery.

[Latex allergy in anesthesiology]

Allergy to latex, described 15 years ago, is increasing. It affects mainly certain risk groups, such as health-care workers and patients with spina bifida or genitourinary malformations. Symptoms vary in intensity from mild to life-threatening and can present during any medical procedure involving skin or mucosal contact, or inhalation, of the allergen in a previously sensitized patient. The most serious cases reported have generally involved patients undergoing surgery. Prevention is based mainly on tentative diagnosis made when the patient's history is taken, followed by laboratory tests and consultation with an allergist. Because prophylactic drug protocols have proven ineffective, the patient must be offered a latex-free environment in keeping with standard recommendations.

[Electromyographic response to precurarization with vecuronium bromide]

OBJECTIVE

To analyze electromyographic response and clinical effects after precurarization with vecuronium bromide (0.01 mg/Kg), also noting intubation conditions and the presence or not of fasciculations after administration of succinylcholine (1.5 mg/Kg).

PATIENTS AND METHODS

A single precurarization dose of vecuronium was administered to 20 patients 5 minutes before anesthetic induction for general surgery. During this period we monitored neuromuscular transmission of the cubital nerve in the wrist by electromyography with a series of 4 stimuli, expressing each as the percentage of the first response and of the ratio T4/T1. We also recorded clinical repercussions. General anesthesia was then induced; after administration of succinylcholine, the presence or not of fasciculations was noted and intubation conditions were evaluated.

RESULTS

The electromyographic response after precurarization was highly variable, as 4 different responses were recorded. We found potentiation phenomena in 20% of our patients, diminished response in 60%, fatigue phenomena in 15% and no change in 5%. Clinical signs noted were blurred vision and heavy eyelids. Fasciculations disappeared in 95% of the patients and intubation conditions were excellent.

CONCLUSIONS

Vecuronium at a precurarization dose produces highly varied but well-tolerated electromyographic responses. The drug is effective in eliminating fasciculations produced by succinylcholine and does not affect intubation conditions.