Biomedical subjects
F M LaForce
Publications and source records attributed to F M LaForce.
Effect of aerosolized Escherichia coli and Staphylococcus aureus on iron and iron-binding proteins in lung lavage fluid.
Iron-binding proteins have antibacterial activity; they have been identified in lung secretions, but their role in pulmonary antibacterial defenses is unclear. Murine lactoferrin and murine transferrin were used to generate polyclonal antiserum to lactoferrin and to transferrin, and the specificity of both antisera was shown by western blot. Mice were exposed to either aerosolized Escherichia coli or Staphylococcus aureus; they were killed 1, 4, 24, or 48 hr later; and their lungs were lavaged. We measured the levels of transferrin, lactoferrin, and albumin and did a cell count for the lavage fluid. The predominant iron-binding protein in resting animals was transferrin. Aerosolized E. coli caused a brisk PMNL response in the lungs that was associated with a major increase in the levels of lactoferrin. Challenge with S. aureus was associated with a moderate increase in the number of macrophages and a moderate decrease in the levels of transferrin and iron but no change in the levels of lactoferrin. The levels of iron-binding protein can vary according to the type of inflammatory response.
Pneumococcal vaccine: the evidence mounts.
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Isolation of an antibacterial peptide from human lung lavage fluid.
The contribution of extracellular secretions to the antibacterial defenses of the lungs remains poorly defined. Recent studies have demonstrated that mouse and rabbit bronchoalveolar washings contain a low-molecular-weight peptide that has antibacterial activity against Escherichia coli. In this study we investigated whether a similar peptide could be identified in human secretions. Bronchoalveolar lavage fluid was obtained from normal volunteers and patients with interstitial lung disease or pulmonary alveolar proteinosis. Cellular material and surfactant lipids were removed from the fluid by sequential centrifugations, and the supernatant was fractionated by exclusion filtration to isolate peptides with a molecular weight less than 10,000. Gel filtration chromatography separated the ultrafiltrate into several peaks, the first of which had antibacterial activity against E. coli. This material was further separated into several hydrophilic peaks by reverse-phase high-pressure liquid chromatography (RPHPLC). All samples had similar RPHPLC graphs. Material from the third RPHPLC peak produced an antibacterial effect similar to that produced by the rabbit and mouse peptide.
Pulmonary cavitation following pulmonary infarction.
Cavitation following bland pulmonary infarction is not commonly considered in the differential diagnosis of cavitary lung disease. In a 4-year period we have found 10 cases of cavitating pulmonary infarction (CPI) by reviewing serial chest radiographs from autopsies with pulmonary infarction and in all cases with positive ventilation-perfusion lung scans. We have compared these cases to 31 previously reported cases in the English literature that met our criteria for CPI. In our 10 patients, there were 12 radiographic cavities; 5 in the upper lobes, 5 in the lower lobes and 2 in the middle lobe. This distribution was consistent with a relative upper-lobe predominance in the literature review. In nine patients the cavitation appeared rapidly (mean, 5 days) and was associated with fever, purulent sputum, and leukocytosis. Sputum cultures were obtained in eight patients, revealing Pseudomonas aeruginosa and Escherichia coli in three each and Proteus species in two. In four patients, pulmonary infarction was not considered and the diagnosis was made at autopsy, a situation also common in previously reported cases. We have seen a high incidence of CPI in a retrospective review of patients with pulmonary infarction, and we believe that it is important to consider this diagnosis when evaluating cavitary lesions.
Killing of fabric-associated bacteria in hospital laundry by low-temperature washing.
Hospitals using 71.1 C water for laundering consume vast amounts of energy. We studied whether washing at 22 C would result in fabric-associated bacterial counts significantly different from those remaining after the high-temperature wash procedure in general use. Using a standard method to enumerate fabric-associated bacteria, we found that soiled sheets and terry cloth items were contaminated, respectively, with 10(6) and 10(8) cfu/100 cm2 of fabric area, predominantly gram-negative rods (especially Enterobacteriaceae and Pseudomonadaceae). Staphylococcus species were the most common gram-positive organisms. A standard low-temperature washing cycle without laundry chemicals removed 3 log10 of bacteria by agitation, dilution, and drainage. When low-temperature laundry chemicals were used, 3 log10 of bacteria were killed after the bleach was added, and sheets and terry cloth items had postwash colony counts of 10(1)-10(2) cfu/100 cm2. Drying removed an additional 1-2 log10 organisms. Bacterial counts and species from low- and high-temperature washed fabrics were comparable. Low-temperature washing is therefore as effective as high-temperature washing for eliminating pathogenic bacteria from hospital laundry.
Comparison of methods for recovery of Escherichia coli and Staphylococcus aureus from seeded laundry fabrics.
To assess the effect of laundry procedures on fabric-associated bacteria, a standard method of enumeration is needed. We evaluated six methods for enumeration of Escherichia coli and Staphylococcus aureus seeded (10(2) and 10(5) CFU/100 cm2 of fabric area) onto sterilized hospital sheets and terry . Two methods involved maceration of seeded swatches in broth followed by passage of the broth through a 0.45-micron-pore-size, 47-mm-diameter filter membrane. Three methods involved agitation of seeded swatches in broth with a paint shaker and membrane filtration of the broth to recover eluted bacterial cells, and the final method involved direct enumeration of cells on fabrics by overlaying seeded swatches with agar containing triphenyltetrazolium chloride as an indicator. The most convenient recovery method employed a 90-s agitation followed by serial dilution of broths and membrane filtration. This method provided 44/57% (low seed/high seed) recovery of E. coli from sheets and 133/31% from terry and 34/74% recovery of S. aureus from sheets and 58/57% from terry . Although maceration provided similar recovery of E. coli and S. aureus, it is a less-practical method. The direct enumeration method was ineffective for enumerating gram-positive bacteria. We conclude that either the agitation or maceration method used enumerated the seeded bacteria to within 1 log10 of their expected number and can be used to assess the bactericidal effectiveness of various steps in the laundering process.
Effect of zinc and phosphate on an antibacterial peptide isolated from lung lavage.
Incubation of Escherichia coli (10(4) organisms per ml) in cell-free rabbit lung lavage for 30 min at 37 degrees C resulted in a 70% reduction in colony counts on deoxycholate agar. A low-molecular-weight peptide (about 3,400 daltons), with zinc as a cofactor, was responsible for this activity. The peptide was isolated by Sephadex G-15 separation of lyophilized rabbit lung lavage which had been centrifuged to remove macrophages and suspended phospholipids and passed through a 10,000-dalton (pore size) membrane filter. Peptide activity against E. coli was inhibited by phosphate buffer but not by borate, Tris, or barbital buffer. Bacteria incubated in phosphate buffer and then washed in saline were resistant to peptide activity. Antibacterial activity was also inhibited when peptide-exposed bacteria were incubated in phosphate buffer before deoxycholate treatment. 32P-radiolabeled E. coli cells lost about 20% of their radiolabel after 15 min of incubation with peptide.
Effect of atropine on oral clearance of a radiolabeled sulfur colloid.
Physical clearance is an important oral defense mechanism against gram-negative rods. We describe a simple technique that uses commercially available technetium-99m sulfur colloid to measure oral clearance. Technetium-99m sulfur colloid was sprayed into the mouth, and clearance was measured as the percent decrease in radiolabel counts over 2 hours using a radioisotope camera. Results using this technique compared favorably with clearance data using Tc-99m radiolabeled Escherichia coli. Atropine significantly decreased oral clearance rates of the colloid. Decreased clearance may be an important risk factor in the development of gram-negative rod colonization in hospitalized patients.
Attitudes of house officers toward a hospice on a medical service.
A hospice program (HP) was established on the medical service at the Denver Veterans Administration Medical Center (DVAMC) for the care of the terminally ill cancer patients and to integrate such care into house staff training. A two-bed inpatient unit was managed by an intern, a resident, and the attending physician with the aid of a multidisciplinary team. During the program's first year, 29 patients were cared for with an average inpatient stay of 26 days. Twenty-nine out of a possible 33 house officers returned questionnaires evaluating their hospice experience. Twenty-eight respondents felt that the hospice program was appropriate in a teaching hospital. Over half indicated improved awareness of the psychological problems of their patients and families. Two-thirds of the house staff members felt that the HP changed their approach to pain control and made them more comfortable in dealing with terminally ill patients. From this study, it can be concluded that a hospice program can be successfully integrated into an active medical teaching service.
Comparison of cefadroxil and cephalexin in the treatment of community-acquired pneumonia.
Thirty-four patients with community-acquired acute pneumonias were treated in a prospective, randomized trial with either cefadroxil, 500 mg twice daily, or cephalexin, 250 mg four times daily. In both groups of patients, the presence of chronic illnesses predisposing to pneumonia was common. Streptococcus pneumoniae was isolated from 65% of the initial sputum specimens, and most illnesses were of mild to moderate severity. All 19 cases treated with cefadroxil and all 15 cases treated with cephalexin were clinically cured, and adverse reactions to the medications were minimal. The success of these regimens suggests that outpatient use of oral cephalosporin therapy may be an appropriate treatment of patients with mild or moderate community-acquired pneumonia.
A mobile internal medicine clinic.
The Denver Veterans Administration Medical Center (DVAMC) established a mobile internal medicine clinic (MediVAn) to provide access to primary care for veterans living more than fifty miles from the center and to study the costs of such an outreach program. A fully equipped van staffed by an internist visited four Colorado cities weekly for scheduled appointments. In the first two years of operation there were 4,655 visits by 766 veterans with a mean age of 56 years, with 3.9 diagnoses, and receiving 3.0 medicines. The cost per MediVAn visit was $68, compared with $67 per outpatient visit at DVAMC. We conclude that a mobile medical clinic is a convenient method of delivering primary care over distances and is comparable in cost to outpatient hospital visits.
Beeper use on a medical service.
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Respiratory infections: major advances.
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Iatrogenic disease in hospitalized elderly veterans.
To help determine whether or not the elderly are at unusually high risk for hospital-related complications, a study was made of consecutive admissions involving 48 patients less than 65 years old (mean 50.3 years) and 174 patients more than 65 years old (mean 73.1 years). They were prospectively followed during their hospital stays, and were monitored daily. According to admission data, they were classified as : Group 1, likely to die soon after admission; Group II, likely to die within a year; Group III, likely to live longer than a year. Complications were listed under the causal factors: trauma, infection, hospital procedures, drugs, and miscellaneous. About 90 per cent of all 222 patients in both age categories were in Group III. The overall complication rates were 29 per cent for patients under 65, and 45 per cent for those over 65 (P less than 0.05). For the under-65 Group III patients, the rates were 17 per cent and 42 per cent for medical and surgical patients, respectively; for the over-65 patients, the rates were 40 per cent (medical) and 43 per cent (surgical). This indicated a major increase in complications among medical patients more than 65 years old. Procedure-related problems were most common among surgical patients under 65. For over-65 patients, the complication rates for procedure-related, trauma, miscellaneous, infection, and drug toxicity categories were fairly evenly distributed within the range of 16.8-12.8 per cent, in that order. Major psychiatric deterioration was observed in 10.7 per cent of patients over 65, but in none of the younger subjects. Drug toxicity and traumatic complications were also more common in the older patients. These data confirm the disproportionately high incidence of iatrogenic diseases in hospital patients over the age of 65. Several of these complications are amenable to control.
Hospital-acquired gram-negative rod pneumonias: an overview.
Because of a high incidence and case fatality rate, nosocomial infections of the lower respiratory tract due to aerobic gram-negative rods are important, particularly in patients bedded in intensive care units. Risk factors include severity of illness, antimicrobial therapy and respiratory tract instrumentation. Respiratory tract colonization, which invariably precedes infection, seems to be a general characteristic of patients with severe illness, whereas normal oral defenses clear gram-negative bacteria very efficiently. Pneumonia follows after failure of pulmonary antibacterial defenses to cope with aspirated inoculums. Attempts to block colonization with local antimicrobials result not only in a transient decrease in colonization and pneumonia but also in the appearance of resistant organisms. Attempts to enhance human lung antibacterial defenses by bacterial interference or immunization have not been well studied. Despite some progress, the general outlook for immediate control of these infections is not encouraging.
Campylobacter enteritis.
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Reservoirs for human campylobacteriosis.
The epidemiology of human enteric infection due to Campylobacter fetus subspecies jejuni is not well understood. To determine whether an endogenous human reservoir is present, the rate of isolation of C. fetus subspecies jejuni from several populations of diarrheal and asymptomatic adults and children were compared. C. fetus subspecies jejuni was recovered from 4.1% of patients with diarrhea and 66.7% of household contacts of the index patients who themselves had diarrhea. Carriage of organisms in most untreated patients lasted less than three weeks from onset of symptoms. C. fetus subspecies jejuni was rarely recovered from the feces of asymptomatic individuals and not at all from the vaginal flora of 272 women. Domestic animals, especially puppies with diarrhea, were frequently infected with Campylobacter and may represent a significant reservoir for human infection.