Buoyant plumes from solute gradients generated by non-motile Escherichia coli.

The effect of hydrodynamic mixing in bacterial populations due to bacterial chemotaxis is a well-described phenomenon known as bioconvection. Here we report the observation of buoyant plumes that result in hydrodynamic mixing, but in contrast to bioconvection the plumes form in the absence of bacterial motility. We propose that the buoyant flow originates from solute gradients created by bacterial metabolism, similar to solute-induced buoyant flow around growing protein crystals. In our experiments, metabolically-active non-motile Escherichia coli were layered along the bottom of flat-bottomed containers. The E. coli consumed glucose in the medium creating a lighter fluid beneath a heavier fluid. The situation is an example of Rayleigh-Taylor instability, in which a lighter fluid pushes on a heavier one. We developed a numerical model to study the effect of E. coli nutrient consumption and by-product excretion on extracellular solute gradients. The model solutions showed reduced-density fluid along the bottom of the fluid domain leading to buoyant plumes, which were qualitatively similar to the experimental plumes. We also used scaling analyses to study the dependence of plume formation on container size and cell size, and to investigate the effect of reduced gravity, such as the microgravity conditions encountered during spaceflight.

Purulent otitis media in adults.

While the bacterial origin of otitis media has been studied extensively in children, there are few data regarding adults with this disease. We undertook this study to identify the incidence, prevalence, and bacteriologic origin of purulent otitis media in adults. This was accomplished through a review of the English-language literature on adult otitis media and a retrospective review of adult patients with this disease who were hospitalized at our institution. Results of literature review indicate that Streptococcus pneumoniae and Haemophilus influenzae are the most common causes of otitis media in ambulatory adults, but this illness is uncommon, with an incidence of only 0.25%. Hospitalized patients in whom this diagnosis was established suffered a variety of serious suppurative complications such as mastoiditis, meningitis, or brain abscess. Otalgia and fever were the most common symptoms noted in this patient population. Further studies of adult otitis media need to be performed to determine bacteriologic, symptomatic, and high-risk patient groups.

Outpatient treatment of community-acquired pneumonia in adults.

Most adults with community-acquired pneumonia are treated as outpatients. Despite this, the majority of studies regarding community-acquired pneumonia have been in hospitalized patients only and may not be applicable to an ambulatory population. This review critically examines the literature regarding the diagnosis, cause, appropriate patient selection, and treatment of nonhospitalized adults with community-acquired pneumonia, including human immunodeficiency virus-infected individuals. English-language articles on oral antibiotic trials for community-acquired pneumonia, obtained from a MEDLINE search from 1966 to the present, are reviewed. Etiologic diagnosis is helpful in determining appropriate outpatient treatment for community-acquired pneumonia, and usually requires only sputum Gram's stain analysis. Viral, mycoplasmal, and chlamydial agents are among the most common pathogens encountered in individuals treated as outpatients, although much variability exists. Many oral antibiotic trials for community-acquired pneumonia have been published, but shortcomings in study design limit their clinical applicability. A treatment algorithm is offered, using the best available data.

Enhanced bleeding with cefoxitin or moxalactam. Statistical analysis within a defined population of 1493 patients.

Most cases of beta-lactam-associated coagulopathy occur in patients with other risk factors. This study analyzed temporally related clinical bleeding events in 1493 patients who received one antibiotic for at least three days. Univariate and multivariate analyses controlled for condition variables (nutritional status, renal, hepatic, or hematologic dysfunction, intensive care unit stay) and treatment variables (use of antiplatelet agents, anticoagulants, vitamin K, antitumor chemotherapy or antiulcer therapy, steroids) that could have been associated with bleeding independently. Rates of bleeding ranged from 0% (chloramphenicol sodium succinate, vancomycin hydrochloride, erythromycin lactobionate) to 8.2% (cefoxitin) to 22.2% (moxalactam disodium). Multiple logistic regression analyses revealed that only moxalactam (odds ratio, 9.9) and cefoxitin (odds ratio, 2.1) exhibited significantly higher likelihoods of bleeding than other agents. This study statistically confirms increased risk of bleeding with moxalactam, heretofore reported only anecdotally. Cefoxitin may carry risks greater than previously believed.

Hereditary ataxia with sensory neuronopathy: Biemond's ataxia.

We report the case of a man with late-onset hereditary ataxia and sensory loss. Three of his sisters were affected by a similar disorder; to date no other members of his family have developed symptoms. The clinical features of this family are similar to a rare form of autosomal dominant hereditary ataxia, recently classified as SCA4. Postmortem findings indicate that this syndrome is marked by degeneration of cerebellar Purkinje cells, dorsal root sensory ganglion neurons, and the ascending posterior columns. Similar clinical and pathologic findings were reported by Biemond in 1954.

Infections in a coronary care unit.

All infections in patients in an active coronary care unit (CCU) over a 3-year period were analyzed to ascertain rates, outcomes, pathogens and sites of infections. Standard surveillance methods and definitions of the Center for Disease Control were used. A total of 236 infections were documented in 200 infected patients. Infection rates were 5 and 2% for total and CCU-acquired infections, respectively. CCU infections accounted for 11% of nosocomial infections that occurred within all critical care areas surveyed. Of all documented infections, 131 (56%) were community-acquired and 90 (38%) were acquired within the CCU. Lower respiratory and urinary tract infections were most frequently noted, with E. coli, S. aureus, and klebsiella-enterobacter-serratia most usually implicated. Mortality among patients with infections was 31%, compared with 8 to 12% in those who were not infected. Those with lower respiratory infections or primary bacteremias had a higher mortality rate than those with infections at other sites (p less than 0.001). Infections are seen in close to 5% of CCU patients and may adversely affect the survival rate. The mortality rate in infected patients may be 3 times higher than that in the general CCU population. This study also provides data against which other similar institutions can gauge their CCU infection rates.

The drug-resistant pneumococcus: clinical relevance, therapy, and prevention.

Streptococcus pneumoniae has been known for > 100 years as the most important bacterial pathogen of the respiratory tract in adults and children. In recent years, the pneumococcus has begun to exhibit increasing resistance to antimicrobial agents. Because of the huge number of infections caused by this organism, the development of resistance has changed the approach to many infectious disease problems, particularly with regard to empiric antibiotic therapy and prophylaxis. In our review of the antibiotic-resistant pneumococcus, we review the microbiologic basis for resistance, risk factors for and clinical relevance of infection by a resistant organism, and infection control measures.

Community-acquired pneumonia caused by mixed aerobic bacteria.

Mixed bacterial pneumonia caused by organisms other than anaerobes has been infrequently reported. We describe six cases and review the literature. Two patients had co-infection with S pneumoniae and L pneumophila. Two were infected with S pneumoniae and K pneumoniae and the others simultaneously harbored M tuberculosis and N asteroides. The first two sets of patients had bacteria isolated from usually sterile sites (blood and lung), while the latter harbored repeatedly isolated organisms not usually felt to be part of the normal respiratory flora. Mixed infection may help explain the substantial mortality still seen from pneumonia. This is especially true if Legionella, mycobacteria, or Nocardia species are encountered where routine smears and cultures may not aid in the diagnosis. Poor clinical response to specific antibacterial therapy in pneumonia should trigger further investigation for other potential pathogens.

Comparison of a hand-held nebulizer with a metered dose inhaler-spacer combination in acute obstructive pulmonary disease.

This study compared the effect of "standard" dose metaproterenol delivered by hand-held nebulizer (HHN) with two puffs of metaproterenol delivered by a metered dose inhaler (MDI) via a spacer (InspirEase) (MDI-spacer). Seventeen patients with an acute exacerbation of obstructive pulmonary disease were studied. Each patient received both MDI-spacer and HHN. Alternate patients were randomized to either MDI-spacer or HHN as initial treatment. Each subject was tested four different times: before and 30 minutes after the initial aerosol delivery technique, and before and 30 minutes after the alternate aerosol delivery technique. Testing consisted of spirometry, lung auscultation, and measurement of vital signs. The interval between treatments for all subjects was 2.96 +/- 0.27 hours (mean +/- SEM) and was not different for subjects who received therapy via MDI-spacer first or HHN first. The patient population studied demonstrated severe airways obstruction (baseline FEV1 33.3 percent predicted +/- 4.9 percent). There was a statistically significant improvement in FVC and FEV1 after metaproterenol delivered by HHN, but not after MDI-spacer. Metaproterenol treatment with HHN resulted in a greater improvement in FEV1 (p less than .05) than MDI-spacer when the data were reported as absolute improvement (0.19 +/- 0.05 L for HHN) vs (0.06 +/- 0.03 L for MDI-spacer) or reported as percent change (23.2 +/- 6.6 percent for HHN) vs (9.5 +/- 3.4 percent for MDI-spacer). Asthmatic patients exhibited a significantly greater (p less than 0.05) improvement in FEV1 after HHN (23.4 +/- 4.7 percent change) than after MDI-spacer (6.6 +/- 4.5 percent change). Patients with chronic obstructive pulmonary disease (COPD) exhibited a greater improvement in FVC (p less than 0.05) after HHN (25.2 +/- 6.7 percent change) than after MDI-spacer (5.8 +/- 4.7 percent change). We conclude that the "standard" dosage of metaproterenol delivered by HHN results in greater spirometric improvement in patients with acute obstructive pulmonary disease than the conventional dosage of metaproterenol delivered by MDI-spacer. It is likely that this reflects the fact that the recommended dose of metaproterenol delivered by MDI is too low and should be increased.

Localized pleural microdeposition of type A amyloid in a patient with rheumatoid pleuritis. Histologic distinction from pleural involvement in systemic amyloidosis.

Decorticated pleural tissue from a 74-year-old man with rheumatoid arthritis, an exudative pleural effusion, and normal left ventricular function contained microscopic deposits of amyloid A protein, localized to the interface between a deep layer of dense fibrocollagen and a layer of granulation tissue beneath a surface fibrin exudate. Previously reported instances of pleural amyloid deposition have occurred in patients with presumed systemic amyloidosis, and most such effusions are the result of congestive heart failure. This patient had no evidence of systemic amyloidosis, and this case appeared to be an example of an unusual form of localized amyloidosis, so-called periinflammatory amyloidosis A. These observations suggest that amyloid in a pleural biopsy should not be construed per se to be diagnostic of systemic amyloidosis.

Community-acquired bacteremias from tunneled central intravenous lines: results from studies of a single vendor.

Tunneled central intravenous catheters are a common method for rendering prolonged outpatient intravenous therapy. Their safety, however, has not been well studied. We conducted a retrospective evaluation of bacteremias associated with tunneled central intravenous catheters managed by a single home health care vendor during a 1-year period. All catheters were inserted in the operating room under sterile conditions. To calculate total line days, the dates of catheter insertion and removal were obtained from either the hospital operating room or the home health care agency. Catheter care was conducted according to written protocols. Total line days were calculated. Community-acquired bacteremia (defined as bacteremia occurring more than 6 days after the patients' discharge from the hospital) was determined from records available in the infection control department. Sixty-eight patients received intravenous therapy from the vendor during the 1-year study period. Total line days were 5548 (median 52 days/patient). Eleven episodes of bacteremia occurred in five patients, providing an incidence density rate of 2.0 infections/1000 catheter days. The most frequent bacteria encountered were Staphylococcus epidermidis (five), Klebsiella pneumoniae (two), and Acinetobacter calcoaceticus var anitratus (two). Median time to bacteremia was 103 days. Two patients, both younger than 4 years, accounted for seven of the infections; both had short-bowel syndrome. On the basis of historical comparisons, outpatient intravenous therapy appears to be associated with a lower risk of bacteremia than in-hospital therapy. These data can provide quality improvement information and may be a means for comparing home infusion therapy vendors.

Outbreak of nosocomial Flavobacterium meningosepticum respiratory infections associated with use of aerosolized polymyxin B.

Flavobacterium meningosepticum is an uncommon cause of adult nosocomial infection. On a medical/surgical intensive care unit we recently encountered an adult outbreak of respiratory colonization and infection caused by this organism, which was associated with the prophylactic use of aerosolized polymyxin B that had been used in an attempt to abort an outbreak of infection caused by highly resistant strains of Pseudomonas aeruginosa. Twenty isolates (95% from respiratory secretions) of F. meningosepticum from nine persons were identified during a 2 1/2-month period. No environmental source has been identified to date. Pneumonia developed in five patients, and two deaths associated with this organism occurred. All isolates were sensitive to ciprofloxacin; none were sensitive to other antibiotics tested, including third-generation cephalosporins, aminoglycosides, erythromycin, trimethoprim-sulfamethoxazole, antipseudomonal penicillins, aztreonam, and imipenem/cilastatin. Two patients with nosocomial pneumonia were successfully treated with oral ciprofloxacin. F. meningosepticum may emerge as an important pathogen if prophylactic use of polymyxin B becomes more widespread. Ciprofloxacin may become the agent of choice for treatment of this organism.

Surgical wound infections documented after hospital discharge.

Shorter lengths of hospitalization may result in more surgical wound infections being documented after hospital discharge. The current investigation analyzed 1644 surgical procedures performed over a 3-month period, and documented surgical wound infections both before and for 1 month after hospital discharge. Physician and patient questionnaires were used. One hundred eight infections were noted, of which 50 (46%) were seen after hospital discharge by either the patient or the surgeon. Rates of infection were 5.2%, 7.5%, and 7.5% for clean, clean-contaminated, and contaminated-dirty categories, respectively. Had postdischarge surveillance not been used, rates would have appeared to be 2.5%, 6.5%, and 6.8% for the same surgical classes. Infections following clean and clean-contaminated procedures were more likely to be noticed after hospital discharge. Excluding those that were patient-documented, wound infection rates would have been 4.2% (clean), 6.3% (clean-contaminated) and 6.8% (contaminated-dirty). Postdischarge surveillance is imperative to meaningfully document true rates of surgical wound infection, inasmuch as increasing numbers are likely to occur only after patients leave the hospital.

Outpatient parenteral antibiotic therapy in the management of community-acquired lower respiratory infections.

Within the past several years, the decision to employ outpatient parenteral antibiotic therapy (OPAT) is driven by adequacy of insurance, availability of appropriate resources within the community, and the clinical stability of the patient. Current dogma is that virtually any diagnosed disease can be treated outside the hospital, provided the former criteria are met. The decision to utilize OPAT is complex and involves a number of decision points that relate to the patient, the disease and pathogen, the antibiotic, and the facilities available in the community. This article discusses the decision-making process to utilize OPAT or hospitalization for community-acquired lower respiratory infections.

Bronchovascular mucormycosis in the diabetic: an urgent surgical problem.

This report reviews the successful surgical experience with a diabetic patient with bronchial obstruction due to Mucorales infection. A review of the reported medical and surgical experience is included. The danger of a lethal pulmonary hemorrhage makes early surgical intervention mandatory.

Endobronchial tuberculosis simulating bronchogenic carcinoma in a patient with the acquired immunodeficiency syndrome.

A patient with the acquired immunodeficiency syndrome (AIDS) had tuberculosis present as an endobronchial mass simulating bronchogenic carcinoma. Endobronchial tuberculosis may be another unusual manifestation of tuberculosis in patients with AIDS. This manifestation of tuberculosis may be missed unless there is a high degree of suspicion. Proper cultures and biopsy specimens should be taken from sites where endobronchial abnormalities are noted in patients at risk for AIDS.

Use of peptide probes to study brain regulation of glucose metabolism.

Neuropeptides may be used to stimulate or inhibit neurocircuitry involved in regulation of visceral organ function, including glucose metabolism. Through the use of different peptides with different specificities, it may be possible to characterize the neuroendocrine and autonomic pathways involved in the physiologic regulation of glucose homeostasis.

Splenic abscess following nonoperative management of splenic rupture.

A recent case of posttraumatic splenic abscess in a young man following nonoperative management of his splenic rupture is reported. With the recent trend toward nonoperative management of hemodynamically stable splenic rupture, the potential complications of splenic abscess may become more common. In view of the high mortality associated with unrecognized splenic abscess, it is important for the clinician to be aware of this entity.

A novel electrochemical heparin sensor.

Heparin is one of the most important clinical drugs, and is employed universally during surgical procedures and extra-corporeal therapies to prevent blood from clotting. Its clinical use, however, is often associated with serious hemorrhagic complications. Because of this life threatening bleeding risk, there is a need for a simple sensing device that can rapidly and directly monitor heparin levels during extra-corporeal therapies to provide a safeguard during these procedures. Current heparin assays are all based on the measurement of blood clotting time, and none of them are suitable for direct and rapid determination of heparin. We describe applying conventional ion selective electrode (ISE) polymer membrane technology and using a specifically formulated membrane doped with tridodecylmethylammonium chloride (TDMAC) as the heparin complexing agent, to devise the first electrochemical sensor for heparin measurement. The sensor is capable of detecting directly and rather selectively the free heparin concentrations in both physiologic saline and undiluted plasma samples. In addition, the clinical utility of the sensor has been demonstrated by monitoring the levels of heparin in undiluted whole blood specimens obtained from patients undergoing open heart operations. It is envisioned that the sensor could be configured as an in-line device within extracorporeal blood loops to monitor current extracorporeal therapy, or as a convenient single use disposable device for rapid bedside or laboratory measurements of heparin in small discrete samples of undiluted whole blood. Preliminary studies concerning the feasibility of designing a mass fabricated, solid state, disposable heparin sensor also have been conducted.

Nosocomial infections in an obstetric and gynecologic hospital.

A prospective study was undertaken at Wesson Women's Unit of Baystate Medical Center to characterize and evaluate nosocomial infections. Using Center for Disease Control criteria, 59 of 1,297 patients undergoing obstetric or gynecologic procedures over a two-month period manifested nosocomial infections. The infected patients were proportionately divided between the obstetric and gynecologic services. However, within each group, certain procedures were associated with a greater incidence of postoperative hospital-acquired infection. Patients who underwent primary cesarean sections and vaginal hysterectomies were most at risk of developing nosocomial infections (22% and 19%, respectively). Nosocomial infection is still a major problem to the obstetrician-gynecologist. However, careful study can delineate patients at high risk, allowing appropriate intervention, including the use of prophylactic antibiotics. This may lead to a significant reduction in the incidence of nosocomial infections.