Alejandro E. Macías

Experimental demonstration of human weight homeostasis: implications for understanding obesity

The existence of a set-point for homeostatic control of human body weight is uncertain. To investigate its existence, technically difficult determinations of energy expenditure must be performed: this has resulted in contradictory reports. The present study was performed with new methods in two stages (77 and 133 d respectively). Two healthy male subjects with rigorously controlled physical activity ingested three standardized diets of processed foods from the same manufacturer. Hypo-, iso- and hyperenergetic diets containing 6255 kJ (1494 kcal), 10 073 kJ (2406 kcal) and 13 791 kJ (3294 kcal) respectively were ingested during alternate periods; changes in body weight were measured. A new index of energy expenditure was calculated as the amount of weight lost in an 8 h overnight period (WL8H). A digital scale was used in stage 1 and a mechanical scale in stage 2. The change in body weight in response to the isoenergetic diet differed according to the circumstances. In basal conditions, it was associated with weight stability. After weight loss from energy restriction, the isoenergetic diet led to weight gain. After weight gain from overeating, it led to weight loss. Diets of higher energy content were associated with greater WL8H (F>20; P<0.0001 for both subjects). Measurement variability was lower using a mechanical scale. The present study demonstrates the existence of a homeostatic control of human weight and describes a new index of energy expenditure measured in weight units. It also demonstrates that strict dietary supervision for months is possible. Investigation of the human body weight set-point is vital in understanding obesity.

Chlorhexidine is a better antiseptic than povidone iodine and sodium hypochlorite because of its substantive effect

BACKGROUNDnThe present study compared both the antiseptic efficacy of sodium hypochlorite against that of chlorhexidine gluconate in isopropyl alcohol and the substantive effect of chlorhexidine, povidone iodine, and sodium hypochlorite.nnnMETHODSnThis was a 2-step study that included volunteers. In step 1, 4 skin areas were tested for bacteria in colony-forming units (CFU): 2 were controls to determine baseline bacteria or the effect of scrubbing, and 2 were treated with 10% hypochlorite or 2% chlorhexidine in isopropyl alcohol. Every subject was tested 4 times. The second step tested the substantive effect of 10% povidone-iodine and the aforementioned antiseptics.nnnRESULTSnFor the first step, 30 volunteers were studied, resulting in 120 determinations for each control and antiseptic. No differences between chlorhexidine gluconate (median 115 CFU/cm(2)) and sodium hypochlorite (median 115 CFU/cm(2)) were found. Both antiseptics were significantly different from rubbing control (317 CFU/cm(2)) and basal control (606 CFU/cm(2)). Only chlorhexidine showed a substantive effect.nnnCONCLUSIONnWe consider that chlorhexidine gluconate in isopropyl alcohol, sodium hypochlorite, and povidone-iodine is equally effective for procedures that do not require a long action. However, chlorhexidine is desirable for procedures such as catheter insertion, skin preparation for surgery, or handwashing prior to surgery.

Contamination of intravenous fluids: A continuing cause of hospital bacteremia

BACKGROUNDnNosocomial bacteremia caused by the contamination of intravenous (IV) infusates is considered rare. Unfortunately, this problem has been underestimated because its identification requires culturing infusates, a procedure not performed routinely.nnnMETHODSnThis study was conducted in a referral hospital where IV infusates are admixed in nursing areas. The aim was to determine the prevalence of infusate contamination in adult patients with gram-negative rod (GNR) bacteremia. Over a period of 32 months, a specimen of infusate was drawn for culture from each patient recruited after the laboratory reported a GNR in the blood.nnnRESULTSnA total of 384 infusates were cultured from 384 patients who had been diagnosed with GNR bacteremia. Seven infusates grew a GNR in culture, for a contamination rate of 2% (7/384; 95% confidence interval [CI] = 1% to 3%). In all cases, the infectious organism was the same as the organism isolated from the blood. Infusate contamination was responsible for 7% (7/108; 95% CI = 2% to 11%) of all primary bloodstream infections and 11% (7/62; 95% CI = 2% to 22%) of all primary bloodstream infections not associated with central venous catheter infection.nnnCONCLUSIONSnFor patients in hospitals where IV drugs are admixed in nursing units, we recommend instituting infusate culture as routine practice following the diagnosis of a GNR in the blood.

Nosocomial bacteremia in neonates related to poor standards of care.

Background: In developing countries, intravenous liquids are mixed and administered by nurses, sometimes under suboptimal infection control conditions. We hypothesized that outbreaks of infusate-associated neonatal bacteremias are common, and we evaluated whether they can be detected by vigilant microbiologic surveillance of infusates. Methods: We studied intravenous infusates administered to neonates in a Mexican hospital where mixtures of infusates were prepared in hospital wards. The study was performed in 3 stages: stage 1, initial culturing of in-use infusates under basal conditions; stage 2, prospective culturing during a cluster of clinical sepsis; and stage 3, final culturing once the outbreak was controlled. Results: In stage 1, 68 infusates were sterile, and 1 was contaminated with Staphylococcus aureus (1.45%), from 23 patients. In stage 2, of 182 infusates from 39 patients, 51 infusates (28%) were contaminated with Gram-negative rods. On the first day of stage 2, 11 of 15 infusates were contaminated with the same strain of Klebsiella pneumoniae, which continued to appear for 26 days. Another 4 strains of Gram-negative rods were also isolated during stage 2. The association between contaminated infusate and death was significant (odds ratio, 9.4; 95% confidence interval, 2–44.3; P < 0.001). Mixtures made by nurses were more likely contaminated than commercial preparations (odds ratio, 3.1; 95% confidence interval, 1.1–8.5; P = 0.037). In stage 3, there were 42 sterile infusates from 22 patients. Conclusions: Our study suggests that poor standards of care common in hospitals from developing countries sometimes result in outbreaks of sepsis and death for newborn patients.

Endemic infusate contamination and related bacteremia.

BACKGROUNDnRecent reports suggest that in-use contamination of intravenous infusates is uncommon in hospitals with good standards of care.nnnMETHODSnWe conducted a survey in a referral hospital in Mexico with good standards of care but no pharmacists to prepare intravenous infusates; we tested the a priori hypothesis that the contamination rate is zero. Using a sterile syringe, we took an initial infusate specimen at the time of recruitment, specimen 1, for culture. We took a second specimen, specimen 2, from administration sets that were maintained for 72 hours. Blood cultures were obtained at the discretion of the physicians caring for the patients.nnnRESULTSnWe cultured 1093 infusate specimens from 621 administration sets comprising 421 patients. We obtained a specimen 1 from each of the enrolled sets and a specimen 2 from 472 sets (76%). We analyzed 10 significant cultures and obtained a global infusate contamination rate of 0.9% (10/1093; 95% CI: 0.5%-1.7%). Two cases of infusate-related bacteremia occurred, establishing a global rate of 0.003/72 infusion hours.nnnCONCLUSIONSnEven in institutions with good nursing standards, endemic in-use infusate contamination may be a present danger. We must avoid the use of intravenous therapy whenever possible.

Stethoscopes as potential intrahospital carriers of pathogenic microorganisms

Stethoscopes can take part in the transmission of health care-associated infections. We cultured 112 stethoscopes by direct imprint on blood agar to estimate the prevalence of potentially pathogenic microorganisms. Forty-eight (47%) produced 50 potentially pathogenic microorganisms; from these, 43 (86%) were Staphylococcus aureus, of which 18 (42%) were methicillin-resistant S. aureus. We concluded that stethoscopes should be considered as potential fomites and must be disinfected routinely before and after each patient contact.

Nosocomial pediatric bacteremia: the role of intravenous set contamination in developing countries.

OBJECTIVEnTo assess the rate of bacterial contamination of intravenous administration sets at their rubber injection ports and matching infusates.nnnDESIGNnCultures of injection ports and infusate during 26 visits to 4 hospitals.nnnSETTINGnFour public general pediatric hospitals in Mexico City with substandard care practices.nnnPATIENTSnHospitalized pediatric patients receiving intravenous solutions.nnnRESULTSnOverall, 176 of 251 injection ports were contaminated (70.1%; 95% confidence interval [CI95], 64.5% to 75.8%), 35 (13.9%; CI95, 9.7% to 18.2%) with gram-negative rods, primarily of the tribe Klebsielleae. Cultures of infusates were positive in 17 cases (6.8%, CI95, 3.7% to 9.9%), 5 of which grew gram-negative rods (2%; CI95, 0.6% to 4.6%). In 3 cases (1.2%), the same species with gram-negative rods was found in the infusates and on the injection ports. During one visit, 8 clustered cases of injection port contamination with a clonal Enterobacter cloacae were found; this agent was also found in the blood culture, intravenous fluid, and parenteral nutrition of one patient. Inadequate chlorination of tap water, a potential risk factor, was recorded during 22 visits (84.6%).nnnCONCLUSIONnThese data suggest that external contamination of the intravenous administration set could play a role in infusate contamination.

Surveillance of Candida spp bloodstream infections: epidemiological trends and risk factors of death in two Mexican tertiary care hospitals.

Introduction Larger populations at risk, broader use of antibiotics and longer hospital stays have impacted on the incidence of Candida sp. bloodstream infections (CBSI). Objective To determine clinical and epidemiologic characteristics of patients with CBSI in two tertiary care reference medical institutions in Mexico City. Design Prospective and observational laboratory-based surveillance study conducted from 07/2008 to 06/2010. Methods All patients with CBSI were included. Identification and antifungal susceptibility were performed using CLSI M27-A3 standard procedures. Frequencies, Mann-Whitney U test or T test were used as needed. Risk factors were determined with multivariable analysis and binary logistic regression analysis. Results CBSI represented 3.8% of nosocomial bloodstream infections. Cumulative incidence was 2.8 per 1000 discharges (incidence rate: 0.38 per 1000 patient-days). C. albicans was the predominant species (46%), followed by C. tropicalis (26%). C. glabrata was isolated from patients with diabetes (50%), and elderly patients. Sixty-four patients (86%) received antifungals. Amphotericin-B deoxycholate (AmBD) was the most commonly used agent (66%). Overall mortality rate reached 46%, and risk factors for death were APACHE II score ≥16 (ORu200a=u200a6.94, CI95%u200a=u200a2.34–20.58, p<0.0001), and liver disease (ORu200a=u200a186.11, CI95%u200a=u200a7.61–4550.20, pu200a=u200a0.001). Full susceptibility to fluconazole, AmBD and echinocandins among C. albicans, C. tropicalis, and C. parapsilosis was observed. Conclusions The cumulative incidence rate in these centers was higher than other reports from tertiary care hospitals from Latin America. Knowledge of local epidemiologic patterns permits the design of more specific strategies for prevention and preemptive therapy of CBSI.

Intravenous ciprofloxacin and ceftazidime in serious infections: A prospective, controlled clinical trial with third-party blinding

Oral ciprofloxacin has been shown to be effective in the treatment of infections due to gram-positive cocci and gram-negative rods. The efficacy and safety of intravenous ciprofloxacin was compared with that of intravenous ceftazidime in the treatment of 59 patients with well-documented serious infections in a prospective, controlled, randomized study with a third-party blinding. Thirty-three patients were treated with intravenous ciprofloxacin (200 mg every 12 hours, plus a daily extra placebo dose); 26 patients were treated with ceftazidime (1 g every eight hours). The severity of the infections, underlying diseases, and demographic features were comparable in both groups, although there were more men in the ciprofloxacin group. For ciprofloxacin/ceftazidime treatments, respectively, the evaluated infections were: pyelonephritis (16 patients/nine patients), pneumonia (three/five), soft-tissue infections (four/zero), spontaneous peritonitis (five/two), primary bacteremia (three/eight), and other (two/two). Isolated pathogens included: Escherichia coli (22/12), Klebsiella sp. (five/four), Pseudomonas aeruginosa (two/three), Haemophilus influenzae (one/one), Proteus mirabilis (two/zero), Proteus vulgaris (one/zero), Salmonella sp. (zero/two), Plesiomonas shigelloides (one/zero), and others (one/four). The clinical responses were cure or improvement in 31 ciprofloxacin cases/21 ceftazidime cases; failure, zero/four; and indeterminate, two/one. The bacteriologic responses were eradication in 28 ciprofloxacin cases/22 ceftazidime cases; persistence, one/three; and indeterminate, four/one. Mild intolerance occurred in three ciprofloxacin cases and two ceftazidime cases. A mild increase in serum hepatic enzymes was observed in two patients in each group. Superinfections occurred in five patients: enterococcal septicemia (zero/two) and urinary tract infections (one/two). The results presented suggest that intravenous ciprofloxacin is an effective and safe antimicrobial agent for the treatment of serious infections, with an efficacy comparable with that of ceftazidime, a broad-spectrum cephalosporin. An additional advantage seems to be a lower rate of superinfections.

H1N1 influenza pandemic of 2009 compared with other influenza pandemics: epidemiology, diagnosis, management, pulmonary complications, and outcomes.

Influenza pandemics are complex events that have occurred frequently throughout human history, three during the past century alone. Now the world is facing the first 21st century pandemic, and the comparison among them is essential to identify common epidemiologic patterns, clinical characteristics, and outcomes. The evolution of medicine, including diagnostic and treatment options, the critical care advances, and global responses are new interventions that could modify the general outcome of the pandemic. Learning from past and current events could lead to a plan for prompt and efficient response in future pandemics and may be help us to predict the unpredictable.