Friday, March 30, 2007
Diagnosis and treatment of impetigo
Am Fam Physician. 2007 Mar 15;
University of Virginia School of Medicine, Charlottesville, Virginia, USA.
Impetigo is a highly contagious, superficial skin infection that most commonly affects children two to five years of age. The two types of impetigo are nonbullous impetigo (i.e., impetigo contagiosa) and bullous impetigo. The diagnosis usually is made clinically, but rarely a culture may be useful. Although impetigo usually heals spontaneously within two weeks without scarring, treatment helps relieve the discomfort, improve cosmetic appearance, and prevent the spread of an organism that may cause other illnesses (e.g., glomerulonephritis). There is no standard treatment for impetigo, and many options are available. The topical antibiotics mupirocin and fusidic acid are effective and may be superior to oral antibiotics. Oral antibiotics should be considered for patients with extensive disease. Oral penicillin V is seldom effective; otherwise there is no clear preference among antistaphylococcal penicillins, amoxicillin/clavulanate, cephalosporins, and macrolides, although resistance rates to erythromycin are rising. Topical disinfectants are not useful in the treatment of impetigo.
PMID: 17390597 [PubMed - in process]
Thursday, March 22, 2007
Bacterial Bait and Switch: Germs Tricked into Absorbing Wrong Element
March 19 2007
Bacterial Bait and Switch: Germs Tricked into Absorbing Wrong Element
Antibiotics, the wonder drugs of the mid-20th century, are starting to run out steam. The Food and Drug Administration (FDA) estimates that 70 percent of bacteria responsible for infections contracted in-hospital have become immune to the antibiotics once able to kill them. The worry is that these treatments will eventually become impotent against powerful new bacterial superstrains that are emerging. As a result, scientists have been trying to find potential new drugs to replace weakening ones.
Now researchers have come up with a possible substitute that utilizes the metal gallium to mimic iron needed by bacteria need to survive. Rather than a drug designed to attack the bacteria itself, gallium boosts of the body's own natural defenses by fooling bacteria into thinking they are well-nourished.
"This approach might intensify a stress already imposed on a bacteria by host defenses," says study co-author Pradeep Singh, assistant professor of medicine and microbiology at the University of Washington School of Medicine. "The immune system has got the bacteria in an armlock and the belly's exposed, and we try to give it a sucker punch in the kidney."
The new approach, described in the April 2 issue of the Journal of Clinical Investigation, takes advantage of bacteria's dependence on iron, which is a constituent of many of their essential enzymes. Iron is also necessary for bacteria to form biofilms, clusters of cells that adhere to surrounding tissue. Once the body detects a bacterial invader, the immune system gobbles up free iron and locks up any stores of the element.
That is where gallium comes in. Despite the element's position five spots from iron on the periodic table, many biological systems are unable to distinguish it from an iron ion. Singh, using methodology co-developed with study co-author Bradley Britigan of the University of Cincinnati, tested bacterial suspensions both in vitro and in mouse models to see if iron-starved bacteria would feel sated in the presence of the beguilingly similar element.
The team observed that small concentrations of gallium—mixed with nitric acid to become gallium nitrate in test tubes—could inhibit the growth of Pseudomonas aeruginosa, an antibiotic-resistant pathogen that commonly infects the impaired lungs of patients with cystic fibrosis (an incurable disease in which there is a mucus buildup in the lungs and pancreas; over half of the disorder's sufferers do not make it to age 18). Higher concentrations of the metal destroyed the bacteria at dosages less potent than those approved by the FDA to intravenously reduce excess calcium in the blood. When subject mice inhaled a gallium solution, the element countered acute, typically fatal amounts of P. aeruginosa. To mimic this Trojan horse's effectiveness against chronic exposure to the bacteria, the metal was pitted against a biofilm (which over time allows the bacteria to acquire a resistance 1,000 times stronger than as free-flowing cells, according to Singh) in the mouse's lungs. The new treatment reduced bacterial counts 1,000-fold.
Singh and his colleagues analyzed the genes in the bacterial cell to determine which ones were vulnerable to the gallium solution. The gallium apparently causes "everything to go haywire in the iron sensing of the bacteria," Singh says, noting that the genetic profile seemed to indicate a particular cell was simultaneously iron-starved and iron-replete.
Despite the resounding success of both the test tube and mouse studies, however, Singh stressed that gallium has yet to go through human clinical trials. But he says that he is optimistic about the gallium's potential, especially as a treatment for cystic fibrosis, which currently has no cure. The goal, he says, is "to have patients inhale gallium and achieve higher concentrations in the lungs and lower concentrations in the rest of the body," because gallium nitrate has been found to impair kidney function.
Unfortunately, he says it is iffy whether gallium could prevent bacteria from mutating into forms that would resist it. "Like any antimicrobial agent," he concedes, "there is the probability that resistance would grow over time."
Wednesday, March 21, 2007
Increased incidence of head and neck abscesses in children
Otolaryngol Head Neck Surg. 2007 Feb
Department of Surgery, Alfred I. duPont Hospital for Children, Nemours Children's Clinic, Wilmington, DE 19899, USA.
OBJECTIVE: To describe increasing incidence and changing microbiology of head and neck abscesses in children admitted to the hospital during the first quarters of 2000 through 2003.
STUDY DESIGN AND SETTING: Retrospective data warehouse review identified 89 children less than 19 years of age admitted to a tertiary care pediatric hospital during the first quarters of 2000 through 2003 for suspicion of head and neck abscess involving the neck, face, and peritonsillar, retropharyngeal, and parapharyngeal spaces; and for orbital and intracranial complications of acute sinusitis.
OUTCOME MEASURES: Outcome measures included the incidence of infection admissions and description of infection location and microbiology, calculated by chi2 technique.
RESULTS: The incidence of infections increased in 2003. The greatest increase was in neck abscesses and complications of acute sinusitis.
CONCLUSIONS: The increase in group A strep infections may be related to its biologic properties.
SIGNIFICANCE: Group A strep remains a significant cause of head and neck infections in children.
Monday, March 19, 2007
Sinusitis: viral, bacterial, or fungal and what is the role of Staph?
Department of Internal Medicine/Allergy and Immunology, St. Louis University School of Medicine, 1402 South Grand Avenue, Room R209, St. Louis, MO 63104, USA. firstname.lastname@example.org
Recently, it has been recognized that inflammation is the major cause of chronic rhinosinusitis (CRS) rather than bacterial infection. Fungi have emerged as a possible pathogenic agent that drives CRS. One clear-cut group of fungal sinusitis can be divided into invasive and noninvasive.
The condition that the allergist is most likely to see is allergic fungal sinusitis. Generally, it appears in atopic, immunocompetent, adolescents and young adults and is marked by the presence of nasal polyps and allergic mucin, which includes eosinophils, Charcot-Leyden crystals, and fungal hyphae. Computer tomographic imaging shows sinus opacification with hyperdense areas.
Treatment has been successful with definitive nasosinus surgery and long-term oral prednisone. There is some evidence that fungi also may account for a large percentage of the remaining CRS patients. In this instance, the immune response to common airborne fungi appears to be IgG mediated rather than IgE mediated.
Promising therapeutic results have been seen with intranasal antifungal agents but larger multicenter double-blinded placebo-controlled studies are needed. Another unanswered question includes the possible role of staphylococcus-derived enterotoxins in the pathogenesis of CRS.
Tuesday, March 13, 2007
Veteran's affairs hospital discharge databases coded serious bacterial infections accurately
Schneeweiss S, Robicsek A, Scranton R, Zuckerman D, Solomon DH. Division of Pharmacoepidemiology and Pharmacoeconomics, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
OBJECTIVES: We sought to test the ability of large health care utilization databases to accurately identify serious bacterial infections and opportunistic infections leading to hospital admission.
STUDY DESIGN AND SETTING: We conducted a cross-sectional validation study using patients admitted to hospitals in the administrative database of the Department of Veterans Affairs, VISN 1, between 2001 and 2004. Detailed hospital chart abstraction protocols were developed to define a gold-standard diagnosis of serious bacterial infections and opportunistic infections. Hospital acquired infections were not considered.
RESULTS: A total of 158 patients who were hospitalized for selected bacterial infections and 69 patients for opportunistic infections were identified using ICD-9 discharge diagnoses. The positive predictive values (PPV) of identifying specific bacterial infections that lead to hospital admissions varied between 100% and 66%. All conditions combined yielded a PPV of 80%. Once the gold-standard definition of bacterial conditions was broadened to hospital admissions due to any acute infectious condition, the PPV increased to 90%. Excluding systemic candidiasis, the average PPV for the selected opportunistic infections was 76%.
CONCLUSION: Our findings suggest that ICD-9 codes of selected serious infections from hospital discharge files can be used as substitutes for chart-based diagnoses.
Tuesday, March 06, 2007
Antibacterial Prophylaxis in Patients with Neutropenia.
J Natl Compr Canc Netw. 2007 Feb
Division of Infectious Diseases, Roswell Park Cancer Institute, Buffalo, New York, and bImmunocompromised Host Infectious Diseases Program, University of Nebraska Medical Center, Omaha, Nebraska; Correspondence: Brahm H. Segal, MD, Division of Infectious Diseases, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263. E-mail: email@example.com.
Patients with cancer and chemotherapy-induced neutropenia are at risk for severe bacterial infections. This risk is not uniform among all cancer patients but is dependent primarily on the depth and duration of neutropenia and the type of underlying disease. Accordingly, the decision whether to use antibacterial prophylaxis to prevent serious infections in these patients requires a balance between expected benefit and the risks for infection, adverse drug-related events, and emergence of antibiotic resistance.
Although antibacterial prophylaxis has the potential to benefit all patients with chemotherapy-induced neutropenia, the benefit regarding reduction in documented infections has been firmly established only in patients with neutropenia expected to exceed 7 days. A recent meta-analysis showed enhanced survival in patients receiving antibacterial prophylaxis during neutropenia; most patients enrolled in the analyzed trials had a hematologic malignancy. Among patients with neutropenia at lower risk for infectious complications (a category that includes most patients with solid tumor malignancies), the main benefit of antibacterial prophylaxis relates to a reduction in fever rather than documented infections.
The authors advise quinolone prophylaxis (levofloxacin is preferred), in patients with an expected duration of neutropenia (absolute neutrophil count
However, if such patients develop fever during neutropenia, they should be considered for outpatient empiric therapy with an oral quinolone-containing regimen if they meet criteria for low risk for complications.
PMID: 17335692 [PubMed - as supplied by publisher]