Biomedical subjects
Publications and source records attributed to J S Tan.
Clinical manifestations and radiographic findings are unreliable guides to the selection of antimicrobial therapy for lower respiratory infections. Laboratory evaluation is necessary to identify the etiologic agent. Multiple oral antibiotics are available for outpatient treatment of bronchitis or pneumonia suspected to be of bacterial origin.
Bacterial skin infections occur commonly and range in severity from mild to life threatening. The severity of skin infections, and their management and prognosis, can depend on the mechanism of infection, the skin structures involved and the infecting organism or organisms. Primary skin infections result from invasion of microorganisms through tiny breaks in the epidermis or from the spread of microorganisms through the bloodstream. Secondary infections arise from pre-existing trauma, burns or surgical wounds; infections involving the soft tissues underlying the skin are also discussed. These also frequently occur in areas of trauma, operation or ischemia. The cause, bacteriologic factors and management of skin infections were studied, with special attention to pyodermas, infections of the foot in diabetic patients and necrotizing soft tissue infections. Choice of appropriate antibiotic agents depends in large part on the infecting organism and patterns of antibiotic susceptibility. In necrotizing soft tissue infections, survival or limb salvage may depend on prompt surgical intervention. In these instances and in some of advanced primary skin infections in which bacteremia is involved, parenteral antibiotics are required. The available options are discussed and a report on the data with the combination agent ticarcillin disodium and clavulanate potassium is presented.
Polymethylmethacrylate bone cement, containing either no added antibiotic, 0.5 g of Vancomycin, 1.0 g of Vancomycin, or 1.0 g of Tobramycin, was mixed either in air or a vacuum chamber. Following storage in a water bath at 37 degrees C for 48 h, the specimens were tested in four-point bending. The porosity of the specimens was assessed radiographically, and their antibacterial activity was monitored for 21 days. The bending strength of the vacuum mixed specimens containing no antibiotic was 40% greater than that of similar air-mixed specimens. However, there were no significant differences in the bending strength of either the air- or vacuum-mixed specimens when any of the antibiotic dosages were added. The bending modulus of the vacuum-mixed specimens, containing no antibiotic, was significantly greater than the moduli of all the other specimen groups which did not differ from each other. Vacuum mixing reduced the apparent porosity of the specimens fivefold, and while the addition of antibiotic did not effect porosity of the air-mixed specimens, that of the vacuum-mixed specimens was doubled. Although initial rapid decreases were seen, leaching of antibiotic from the cement and antibacterial activity continued through the 21-day monitoring period.
Escherichia coli is still the most common bacterial pathogen associated with urinary tract infections in women. Because of increasing resistance, ampicillin or a sulfonamide alone is no longer recommended for the empiric treatment of those infections. Antimicrobial therapy that contains a beta-lactamase inhibitor or that is resistant to the action of beta-lactamase is preferred. For the treatment of acute, uncomplicated lower urinary tract infection in a young woman, a short course of therapy (single dose) may be adequate. For an upper tract or complicated infection a longer course of therapy is advised. Asymptomatic bacteriuria in pregnancy should be treated; a short course of therapy with a beta-lactam antibiotic may be tried only if posttherapy follow-up cultures are planned. When bacteriuria persists or recurs, a longer course of therapy should follow, with consideration given to a urologic workup after delivery.
Corynebacterium group D2 is a gram-positive bacillus easily identified in clinical microbiology laboratories. However, this organism is often disregarded as a skin and mucous contaminant. The Spanish literature has recently described Corynebacterium group D2 as a urinary pathogen in a specific patient population. We report a case of Corynebacterium group D2 infection to illustrate the potential pathogenicity and clinical presentation of infection due to this organism in the United States.
Cefmetazole is a cephamycin antibiotic which is resistant to hydrolysis by various beta-lactamases. This study evaluated the pharmacokinetics of cefmetazole, including its intravascular and interstitial fluid distribution, by using the skin window (SW) technique. A 2-g dose of cefmetazole was given intravenously over 30 min to each of 12 healthy adult male volunteers every 6 h for nine doses. Plasma levels were assayed at predetermined intervals after doses 1, 5, and 9. Interstitial fluid levels were determined by the SW technique. Antibiotic levels were assayed by the agar well bioassay technique. A concentration-versus-time plot indicates that cefmetazole is rapidly distributed, with mean peak levels in plasma equal to 126 micrograms/ml at the end of the half-hour infusion. The mean plasma half-life was 1.1 h. Plasma and tissue distribution constants permitted calculation of theoretical levels in tissue. Parallel elimination slopes for SW and theoretical tissue level showed that the SW model distribution kinetics are closely related. The area under the curve for the SW was 73.9 mg.h/liter. This was comparable to the theoretical level in tissue, which was 96 mg.h/liter. Furthermore, the area under the curve of theoretical tissue level/plasma was 0.6 and that of SW/plasma was 0.47. These results demonstrate that the SW technique yielded a result quite close to the theoretical tissue level. Ultrafiltration analysis indicated that as cefmetazole levels in plasma increased from 10 to 250 micrograms/ml, plasma protein binding of the antibiotic dropped from 85 to 65%. Finally, 60 to 70% of the drug was recovered from the urine as biologically active drug over 6 h postinfusion.
Staphylococcus is, by far, the most commonly seen organism in podiatric infections. Although common, staphylococcal infections are difficult to understand and treat. These bacteria have undergone significant changes in their pathogenicity and antibiotic susceptibility over the last few years. Methicillin-resistant strains, once relatively rare, are becoming a major therapeutic dilemma in some centers.
Eighty-four rats were exposed intratracheally to 25 mg of locally produced Xinkang short-fiber chrysotile asbestos (98% of the fibers are less than 5 microns in length). In 1 to 3 d after instillation, the pathological changes in rat lungs demonstrated that the affection was mainly acute bronchio-alveolitis characterized by acute inflammatory exudation and injuries of the small airways and alveolar structural units. The four main manifestations of alveolitis induced by the chrysotile asbestos were of the neutrophilic, serous, alveolar macrophages and granulomatous varieties. Three types of pulmonary fibrosis developed gradually from 7 to 90 d following the exposure to the asbestos, i.e. the intraluminal, murally incorporated, and interstitial fibrosis. Findings showed the complete process from the acute inflammatory exudation and the damage to lung tissue, with the following repair and proliferation of injuried lung tissue and organization of exudate, to the final fibrosis and destruction of the lung. The results suggested that the persistent and irreversible damage to the epithelial cells of respiratory bronchioles and pneumocytes, and denudation and destruction of the basement membrane played an important role in the development of pulmonary fibrosis by forming a channel for the inflammatory exudates and fibroblasts migrating into the bronchioalveolar spaces. Therefore, the experimental results have proved that Xinkang chrysotile asbestos fibers less than 5 microns in length certainly have a fibrogenic effect.
Tuberculosis remains a significant clinical and public health problem in the United States. To determine if a significant proportion of hospitalized patients diagnosed as having pulmonary tuberculosis were not suspected of the disease following initial patient assessment, we retrospectively reviewed the microbiology records of a 515-bed community teaching hospital and identified all patients with culture-proven Mycobacterium tuberculosis infection hospitalized between January 1983 and December 1987. Pulmonary tuberculosis was not suspected in 13 (42%) of 31 patients with active disease. These patients were elderly (92% aged 65 years or older vs 8% aged less than 65 years), had a delay in respiratory isolation (6 vs 1 days) and diagnosis (8 vs 3 days), in addition to a longer hospitalization (16 vs 11 days) with increased mortality (46% vs 11%). Inadequate diagnosis may contribute to the persistence of morbidity and mortality from tuberculosis in this country.
Urinary tract infection (UTI) is common in the elderly, with a prevalence of approximately 20% in women over 65 years of age. The elderly are predisposed to UTI by anatomic changes in the genitourinary system, by underlying disease, by instrumentation, and by residing in long-term care settings. Indwelling urinary catheters are a frequent cause of UTI, and catheter-associated sepsis is the most common cause of gram-negative sepsis in hospitals. Resistant organisms, prevalent in long-term care settings and hospitals, are increasingly responsible for UTI. Empiric antibiotic therapy has changed with the availability of new agents that cover resistant organisms. Oral antibiotics are appropriate for most UTIs; however, more serious infections require parenteral therapy. Length of antibiotic therapy is generally increased for UTI in the elderly.
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A blood culture was performed by adding a vented Septi-Chek bottle (Roche Diagnostics, Div. Hoffmann-LaRoche Inc., Nutley, N.J.) to a standard BACTEC system (Johnston Laboratories, Inc., Towson, Md.) blood culture. The yield of bacteremic patients, the clinical significance of organisms detected, and the cost of the combination system were compared with those of the standard BACTEC system alone. Each culture included 20 ml of blood divided among a BACTEC 6B aerobic bottle (5 ml), a BACTEC 7D anaerobic bottle (5 ml), and a Septi-Chek bottle equipped with a slide subculture attachment (10 ml). Significant isolates grew in 9.6% of the 2,269 cultures evaluated. The combination BACTEC plus Septi-Chek system detected 25% more bacteremic patients than the BACTEC system alone, 129 patients versus 103. The 26 bacteremic patients detected by only the added Septi-Chek bottle included 7 whose organism was isolated from blood alone and 19 whose organism was in mixed or pure culture from a second source. Detection of the organism resulted in alteration of antimicrobial therapy in 17 of these 26 patients. The combination system, which cultured a 20-ml blood volume, cost $11,000 more during the study period than the BACTEC system alone, which cultured a 10-ml volume. Reimbursement under the diagnosis-related group system was increased by $23,000 as a result of documentation of sepsis in these 26 patients. Blood volume and, possibly, the use of multiple blood culture systems are important factors when selecting a blood culture procedure for routine use.
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Parenteral therapy is recommended for empiric treatment of serious urinary tract infections. The approach to antimicrobial selection is reviewed with consideration given to newly available agents.
The antimicrobial susceptibility of clinical isolates of the Bacteroides fragilis group was determined at six community hospitals (one large, greater than 600 beds; and five smaller, 96-325 beds). Imipenem was the most active beta-lactam with 100% of isolates being sensitive at 4 micrograms/ml. The percentage of isolates inhibited at 16 micrograms/ml (and 32 micrograms/ml) for the 7-alpha-methoxy antibiotics was: cefoxitin 66 (90); moxalactam 73 (85); cefotetan 68 (72); cefmetazole 40 (61). Metronidazole, chloramphenicol, and clindamycin were active against 100%, 100%, and 89% at breakpoints of 8 micrograms/ml, 8 micrograms/ml, and 4 micrograms/ml, respectively. The activity of several beta-lactams in our report differed slightly from that reported from university teaching hospitals. There were differences at many of the breakpoints for activity of some of the beta-lactam antibiotics for isolates from the large community hospital as compared with the combined isolates from the smaller community hospitals. Interestingly, the pattern was one of more resistance at the smaller community hospitals.