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Biomedical subjects

P E Schoch

Publications and source records attributed to P E Schoch.

At least 19 recordsLinked to original sources

Appropriateness of empiric gentamicin and vancomycin therapy for bacteremias in chronic dialysis outpatient units in the era of antibiotic resistance.

Bacteremias in inpatient chronic HD units have been described, but there is little information on bacteremias in ambulatory HD units. To determine the frequency of bacteremia and pathogen distribution in ambulatory chronic HD units, we retrospectively reviewed our experience with 107 bacteremias in 5 chronic ambulatory HD units over a 3 year period. The object of the study was twofold. The first objective was to determine if bacteremias in ambulatory HD setting were substantially different in frequency or type than in the inpatient HD setting. Secondly, febrile patients suspected of having bacteremia in chronic HD patients are often empirically treated with vancomycin and gentamicin. Chronic HD patients require repeated and frequent venous access for HD. Bacteremias are common in chronic HD patients and may be primary or secondary and are often related to venous access site infections. The distributions of bacteremia pathogens in chronic HD patients are predominantly reflective of skin flora, i.e., staphylococci and to lesser extent aerobic Gram-negative bacilli. After S. aureus (MSRA/MSSA) and coagulase-negative staphylococcus (CoNS), enterococci are the next most important Gram-positive pathogens in bacteremic HD patients. Most strains of E. faecalis are sensitive to vancomycin and for practical purposes should be considered as vancomycin sensitive enterococci (VSE). In contrast, most strains of E. faecium are resistant to vancomycin and should be considered as vancomycin resistant enterococci (VRE). We retrospectively reviewed 107 patients on chronic ambulatory HD to determine the adequacy of empiric vancomycin and gentamicin prophylaxis. We found amikacin is preferred to gentamicin and that meropenem is an effective alternate substitution for gentamicin and vancomycin combination therapy.

Antibiotic Prophylaxis↗

Activities of bismuth thiols against staphylococci and staphylococcal biofilms.

Indwelling medical devices are associated with infectious complications. Incorporating antimicrobials into indwelling materials may reduce bacterial colonization. Bismuth thiols are antibiofilm agents with up to 1,000-fold-greater antibacterial activity than other bismuth salts. Staphylococci are particularly sensitive, as determined by agar diffusion and broth dilution susceptibility testing. Bismuth-ethanedithiol inhibited 10 methicillin-resistant Staphylococcus epidermidis strains at 0.9 to 1.8, Staphylococcus aureus ATCC 25923 at 2.4, and S. epidermidis ATCC 12228 at 0.1 microM Bi(3+). Antiseptic-resistant S. aureus was sensitive to bismuth-2-3-dimercaptopropanol (BisBAL) at < or = 7 microM Bi(3+). Hydrogel-coated polyurethane rods soaked in BisBAL inhibited S. epidermidis for 39 days (inhibitory zone diameter in agar, > or = 30 mm for > 25 days). Slime from 16 slime-producing S. epidermidis strains was inhibited significantly by bismuth-3,4-dimercaptotoluene (BisTOL), but not by AgNO3, at subinhibitory concentrations. In conclusion, bismuth-thiols are bacteriostatic and bactericidal against staphylococci, including resistant organisms, but are also inhibitors of slime at subinhibitory concentrations. At subinhibitory concentrations, BisTOL may be useful in preventing the colonization and infection of indwelling intravascular lines, since staphylococci are important pathogens in this setting.

Anti-Bacterial Agents↗

Enhancement of bismuth antibacterial activity with lipophilic thiol chelators.

The antibacterial properties of bismuth are greatly enhanced when bismuth is combined with certain lipophilic thiol compounds. Antibacterial activity was enhanced from 25- to 300-fold by the following seven different thiols, in order of decreasing synergy: 1,3-propanedithiol, dimercaprol (BAL), dithiothreitol, 3-mercapto-2-butanol, beta-mercaptoethanol, 1-monothioglycerol, and mercaptoethylamine. The dithiols produced the greatest synergy with bismuth at optimum bismuth-thiol molar ratios of from 3:1 to 1:1. The monothiols were generally not as synergistic and required molar ratios of from 1:1 to 1:4 for optimum antibacterial activity. The most-active mono- or dithiols were also the most soluble in butanol. The intensity of the yellow formed by bismuth-thiol complexes reflected the degree of chelation and correlated with antibacterial potency at high molar ratios. The bismuth-BAL compound (BisBAL) was active against most bacteria, as assessed by broth dilution, agar diffusion, and agar dilution analyses. Staphylococci (MIC, 5 to 7 microM Bi3+) and Helicobacter pylori (MIC, 2.2 microM) were among the most sensitive bacteria. Gram-negative bacteria were sensitive (MIC, < 17 microM). Enterococci were relatively resistant (MIC, 63 microM Bi3+). The MIC range for anaerobes was 15 to 100 microM Bi3+, except for Clostridium difficile (MIC, 7.5 microM). Bactericidal activity averaged 29% above the MIC. Bactericidal activity increased with increasing pH and/or increasing temperature. Bismuth-thiol solubility, stability, and antibacterial activity depended on pH and the bismuth-thiol molar ratio. BisBAL was stable but ineffective against Escherichia coli at pH 4. Activity and instability (reactivity) increased with increasing alkalinity. BisBAL was acid soluble at a molar ratio of greater than 3:2 and alkaline soluble at a molar ratio of less than 2:3. In conclusion, certain lipophilic thiol compounds enhanced bismuth antibacterial activity against a broad spectrum of bacteria. The activity, solubility, and stability of BisBAL were strongly dependent on the pH, temperature, and molar ratio. Chelation of bismuth with certain thiol agents enhanced the solubility and lipophilicity of this cationic heavy metal, thereby significantly enhancing its potency and versatility as an antibacterial agent.

Antacids↗

Bacteremia and chorioamnionitis due to cryptic genospecies of Haemophilus Influenzae biotype I.

Nontypable strains of Haemophilus influenzae are well-known causes of maternal and neonatal infections. Using DNA-DNA hybridization techniques, some of these strains have been shown to belong to a cryptic genospecies of Haemophilus, which is distantly related to Haemophilus influenzae and Haemophilus hemolyticus. This report describes the first case of sepsis and chorioamnionitis due to Haemophilus influenzae biotype I, which was identified using the RapIDNH system and then confirmed by multilocus enzyme electrophoresis to belong to this cryptic genospecies of Haemophilus. The electromorph type 92 of the isolate was consistent with that of biotype I of the cryptic genospecies.

Adult↗

Rhodococcus.

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Acquired Immunodeficiency Syndrome↗

Flavimonas oryzihabitans (CDC group Ve-2) bacteraemia associated with Hickman catheters.

Flavimonas oryzihabitans is a potential pathogen that may infect patients who have major medical illnesses, especially those who are undergoing surgery or have indwelling venous catheters in situ. Flavimonas oryzihabitans has been isolated from a wide range of body sites, and the portals of entry are major wounds or implanted foreign materials. We report two cases of F. oryzihabitans bacteraemia associated with the use of Hickman catheters for administration of the patients' chemotherapeutic agents. However, a common source for these infections could not be demonstrated.

Bacteremia↗

Rapid plasmid DNA isolation from mucoid gram-negative bacteria.

Exopolysaccharides interfere with the isolation and characterization of plasmid DNA from gram-negative bacteria. To repress capsular polysaccharide production, bacteria were cultured in medium containing bismuth nitrate and sodium salicylate. Rapid removal of other contaminating bacterial surface components was achieved by mild acidic zwitterionic detergent extraction. After treatment, bacterial cells were more readily lysed in alkaline detergents. The resulting plasmid preparations contained virtually no capsular polysaccharide and relatively small quantities of lipopolysaccharide and protein, yet they produced yields of nucleic acids similar to those of conventional plasmid preparations. Conventional preparations from encapsulated organisms were largely insoluble and appeared as smears following agarose gel electrophoresis, with indefinite plasmid banding. Plasmids prepared by the new method were highly soluble in conventional buffers and exhibited high-resolution plasmid banding patterns in agarose gels. Plasmids as large as 180 kbp could be isolated and visualized, without apparent nicking, and were readily digested by restriction endonuclease enzymes. The method proved effective with encapsulated or mucoid strains of Klebsiella pneumoniae, Escherichia coli, Acinetobacter anitratus, Salmonella typhimurium, and Enterobacter species. The complete method for plasmid isolation was not suitable for Pseudomonas aeruginosa because of the inhibitory effects of bismuth. Thus, removal of contaminating bacterial surface structures enabled the rapid isolation and characterization of plasmids from mucoid clinical isolates, without the use of organic solvents, CsCl gradients, or expensive, disposable columns.

Bacterial Typing Techniques↗