Biomedical subjects

C R Libertin

Publications and source records attributed to C R Libertin.

33 records · Page 2Linked to original sources

PubMed1989

A double-blinded comparative evaluation of three media for chromophore testing with viridans and nutritionally variant (deficient) streptococci.

A double-blinded prospective comparison of chromophore testing among 109 clinical isolates of alpha-hemolytic gram-positive cocci and 48 strains of nutritionally variant (deficient) streptococci (NVS) for its sensitivity, specificity, and predictive value under stimulated clinical laboratory conditions was performed after growth in three different media--Todd-Hewitt broth supplemented with 10 micrograms/mL of pyridoxal (THBP), THBP with 0.8% (w/v) yeast-extract (THBP + YE), and a semisynthetic chemically defined medium with Todd-Hewitt dialyzate (CDMT). The chromophore detection rates of Streptococcus mitis were 60.7, 67.9, and 78.6% after growth in THBP, THBP + YE, and CDMT, respectively. After growth in THBP there was significantly lower chromophore detection than either THBP + YE or CDMT for NVS (P less than 0.001), with a trend toward significantly less detection for S. mitis (0.15 greater than P). For Streptococcus sanguis II the detection rates were 45.7, 57.1, and 54.3%, respectively, for each medium. There was no significant difference between the detection rates after growth in THBP + YE or CDMT. One NVS was persistently chromophore negative, the first so described. There was a similar number of presumably false positive chromophore S. sanguis I strains (3 of 12) detected after growth in THBP + YE or CDMT. The sensitivity of chromophore detection for NVS (pooling results in THBP + YE and CDMT) was 95.8% and specificity was 59.6%. For a nonvariant streptococcus, the sensitivity was 61.9% and specificity was 93.5% for an isolate to be either S. mitis or S. sanguis II.

Chromogenic Compounds↗

PubMed1989

Molecular analysis of viridans and nutritionally deficient (variant) streptococci causing sequential episodes of endocarditis in a patient.

Clinical blood isolates from sequential episodes of endocarditis occurring over a six-month period of time in an addict were investigated. The pathogens were Streptococcus sanguis II, Streptococcus mitis, and a nutritionally deficient (variant) streptococcus. The authors determined the DNA relatedness of these isolates by antibiograms, plasmid profiles, chromosomal endonuclease restriction digestions, and dot blot DNA-DNA hybridization analyses. The S. sanguis II and nutritionally deficient streptococcal strain had similar antibiograms being resistant to penicillin; neither produced beta-lactamase. No plasmids were found. The restriction endonuclease chromosomal digestion patterns of these isolates were unique and epidemiologically unrelated to each other. Dot blot DNA-DNA hybridizations, using the nutritionally deficient streptococcal DNA as the probe, showed homology to the preceding clinical isolates, S. sanguis II and S. mitis, at 15.4% and 45.1% hybridization levels, respectively. The nutritionally deficient streptococcus was only 4.2% homologous to a S. mitis ATCC strain and another nutritionally deficient streptococci isolate. Therefore, this patient had endocarditis with three distinct streptococcal strains.

Adult↗

PubMed1989

Enzymatic extraction and spectral analysis of the chromophore from cell walls of nutritionally deficient streptococci.

We demonstrated by spectral analysis a method to enzymatically cleave the chromophore precursor from nutritionally deficient streptococcal cell walls by treatment with lysozyme. The peak absorbances without and with lysozyme pretreatment were 511.4 +/- 2.02 nm and 513.1 +/- 0.69 nm, respectively. Extraction yields varied among strains and were found to be growth phase dependent. A secondary peak of absorbance (mean of 477 nm) was found in only five of eight strains. The chromophore at a neutral pH undergoes a reaction with phenol consistent with that of a furan, indicating its carbohydrate composition.

Cell Wall↗

PubMed1989

Removal of cephalosporins by continuous arteriovenous ultrafiltration (CAVU) and hemofiltration (CAVH).

Cephalosporins are used with increasing frequency for sepsis treatment in patients receiving CAVU and CAVH. The different cephalosporins share the same basic molecular structure, yet they exhibit varied extent of plasma protein binding. Different amounts of the antibiotics may be removed by the ultrafiltration procedure because of these variations of physicochemical properties. We evaluated the sieving of eight new cephalosporins across the hemofilter membrane using an in vitro model. Bovine blood was perfused through polysulfone membranes at blood and ultrafiltrate flow rates of 100 and 20 ml/min respectively. Arterial plasma, venous plasma and ultrafiltrate drug concentrations were used to determine sieving coefficients. The sieving coefficients correlated well with the ultrafiltrate-arterial plasma drug concentration ratio (r = 0.679-0.972) but poorly with the extent of protein binding. Factors other than protein binding may therefore affect the drug sieving. Based on the findings, it was predicted that 0.2-21.9% of the daily cephalosporin dose may be removed by the CAVU and CAVH treatment. The need to alter drug dosages depends on the techniques of the ultrafiltration and hemofiltration procedure, the kinetics of the cephalosporins in patients, the sensitivity of the pathogen and the nature of the infection.

Animals↗

PubMed1988

Time kill curve analysis of vancomycin and rifampin alone and in combination against nine strains of nutritionally deficient streptococci.

Endocarditis caused by nutritionally deficient streptococci has a high bacteriologic and clinical failure rate, despite appropriate antimicrobial therapy. We investigated by time kill curve methodology nine clinical endocarditis isolates of nutritionally deficient streptococci to determine the in vitro efficacies of vancomycin and rifampin alone and in combination. The combination of vancomycin and rifampin demonstrated synergy and bactericidal activity in five of the strains. In one strain, this combination inhibited growth by greater than 2 log10 CFU/ml when compared to the growth control or either antibiotic alone, but it failed to be bactericidal. Indifference, defined as less than or equal to 2 log10 CFU per milliliter increase in killing of the combination compared to the next most active single agent, was demonstrated with the remaining three isolates. Changing the antibiotic concentrations in the time kill curve studies for these latter strains failed to demonstrate synergistic activity of the antibiotic combination. The vancomycin and rifampin combination may be a promising therapeutic modality for which in vivo correlation is indicated.

Drug Synergism↗

PubMed1988

Group G Streptococci: susceptibility patterns and the effect of the inoculum size and growth phase on the bactericidal activity of penicillin.

Twenty-seven independent group G streptococcal isolates were studied by in vitro susceptibility testing against 22 different antimicrobial agents. Penicillin with a MIC90 of 0.03 micrograms/ml and ampicillin with a MIC90 of less than or equal to 0.015 micrograms/ml remain the agents of first choice for treatment of group G streptococcal infections. Tolerance was not demonstrated using the macrobroth dilution method in four media, Todd-Hewitt, Mueller-Hinton, Mueller-Hinton (cation-supplemented), and Tryptose Phosphate broths. Multiple regression analyses of time-kill curves of group G streptococci showed that the rate of cell death with penicillin at 0.04 micrograms/ml (five times greater than each organism's MIC) for both logarithmic- and stationary-phase cells with low-inocula were the same, but were five to six times greater in rate of death compared to the high-inocula cultures. Increasing the concentration to 1 microgram/ml of penicillin (125 times greater than each organism's MIC) did not significantly affect the rate of cell death for low-inocula cultures of either phase. Therefore, the size of the inoculum was found to be more significant than the phase of bacterial growth. These findings may explain the therapeutic discrepancy of relapses or prolonged group G streptococcal infections despite the organism being susceptible to the given antibiotic.

Aminoglycosides↗

PubMed1985

Candida lusitaniae--an opportunistic pathogen.

Candida lusitaniae is a newly recognized opportunistic pathogen amongst immunocompromised patients. The epidemiology and pathology remain largely unknown. This case report describes a 27-year-old female with vasculitis who acquired a fatal C. lusitaniae fungemia.

Adult↗

PubMed1984

Analysis of Pneumocystis carinii cysts with a fluorescence-activated cell sorter.

Human sera from Pneumocystis carinii-infected patients and specific rabbit antisera have antibodies against the cyst form of the organism. Lung tissue concentrations from cortisone-treated C3H/HeN mice and six open lung biopsy-positive patients were centrifuged and suspended, and immunofluorescent staining was done. We utilized the fluorescence-activated cell sorter to analyze and sort P. carinii cysts from lung homogenates into a morphologically distinct population. A quantitative basis was used for the definition of the cyst population by displaying the frequency of cells as a function of parameter (fluorescence intensity and light scatter) expression. In 14 of 15 histogram analyses, P. carinii-infected homogenates were differentiated from normal- and bacterial-control homogenates. The parameter range of light scatter (size) was 2 to 8 micron, and the fluorescence intensity was greater than a threshold based on the histogram profile.

Animals↗

PubMed1983

Effects of trimethoprim-sulfamethoxazole and incubation atmosphere on isolation of group A streptococci.

The effects of selective media and incubation atmosphere on the isolation of group A beta-hemolytic streptococci were evaluated. A higher percentage of group A streptococci was isolated on sheep blood agar incubated in air than in CO2 or anaerobic atmospheric conditions. Fewer non-group A beta-hemolytic streptococci were isolated on sheep blood agar incubated in air than in CO2 or anaerobically. Group A streptococcal isolation was not significantly affected by different incubation atmospheres on sheep blood agar containing trimethoprim-sulfamethoxazole, but detection time was longer than on sheep blood agar alone. No significant difference was found between isolation of group A streptococci on sheep blood agar incubated in air and that on sheep blood agar containing trimethoprim-sulfamethoxazole and incubated in 5 to 10% CO2; however, more group A streptococci were isolated on sheep blood agar in air within 24 h. Sheep blood agar incubated at 35 degrees C in air is, therefore, recommended for the isolation of group A streptococci from throat swabs.

Air↗

PubMed1983

Invasive disease caused by Trichosporon beigelii.

An immunocompromised patient had cellulitis that was unresponsive to conventional antimicrobial therapy. Skin biopsy specimens and fungal blood cultures revealed the offending organism as Trichosporon beigelii. Recognition of this opportunistic pathogen in immunocompromised patients is important.

Humans↗

PubMed1982

Hemosiderosis in a dialysis patient: treatment with hemofiltration and deferoxamine chelation therapy.

Although the highly permeable membranes utilized in hemofiltration are theoretically more permeable to deferoxamine-chelated iron than the standard cuprophan membranes used in conventional hemodialysis, no clinical data support this contention. Ours are the first published results of a preliminary short-term trial of combined therapy with deferoxamine and hemofiltration in a dialysis patient with hemosiderosis. An average of 15.3 mg of iron was mobilized with a 19.5-liter exchange over only 4 1/2 hours of postdilution hemofiltration. This compares favorable with previous reports in which 8 to 12 hours of dialysis were performed with Kiil dialyzers, and also with the 24-hour urinary excretion of chelated iron in iron-overloaded patients with normal renal function. We conclude that combined therapy with deferoxamine and hemofiltration offers promises as an effective means of iron mobilization in dialysis patients with hemosiderosis.

Aged↗

PubMedDate not supplied

Osteomyelitis caused by Rhodococcus equi in a renal transplant recipient.

We report the first case of osteomyelitis due to Rhodococcus equi, which occurred in a renal transplant patient. Infection with this organism is rare and usually causes a distinct clinical syndrome resembling pulmonary tuberculosis. We investigated by time-kill curve analysis various antimicrobial combinations for in vitro efficacy. The literature is briefly reviewed, and aspects of diagnosis and therapy are discussed.

Actinomycetales Infections↗

PubMedDate not supplied

Genetic heterogeneity among nutritionally deficient streptococci.

The nutritionally deficient (variant) streptococci (NDS) share the auxotrophic characteristic of requiring pyridoxal or thiol group supplementation for growth. The deoxyribonucleic acid relatedness of these organisms among themselves is unknown. Improved speciation of NDS would lead to a better knowledge of their pathogenesis and possible insight into improved clinical management. Therefore, DNA-DNA hybridization and biotyping of 23 nutritionally deficient streptococci were performed. Biochemical testing using the API Rapid Strept Identification method revealed that the organisms in this study were characterized among three broad biotype groups. Only one strain was nontypeable. DNA-DNA hybridization among the nutritionally deficient streptococci that we compared revealed genetic heterogeneity. Only four (17%) of 23 isolates were highly homologous; all were of biotypes 2 and 3. Reference viridans streptococcal strains had minimal homology to the NDS strains. The data indicate that the NDS are genetically heterogeneous.

Bacterial Typing Techniques↗

PubMedDate not supplied

Beta-hemolytic group F streptococcal bacteremia: a study and review of the literature.

Group F streptococci are part of the oropharyngeal, bowel, and perineal flora. Abscess formation by these organisms most commonly involves the cutaneous system: the next most common sites, in descending order, are the cervicofacial, dental, and intraabdominal areas. Among our population of patients with abscesses, serious infection rarely occurred in otherwise healthy individuals in the absence of trauma. Group F streptococci represented 2% of beta-hemolytic streptococcal isolates from all patients with bacteremia who were hospitalized at Mayo Clinic-affiliated hospitals from 1970 to 1980. In five of seven bacteremic patients, some manipulation, perforation, or underlying pathology associated with the gastrointestinal tract existed. Polymicrobial bacteremia was common. All isolates of group F streptococci were susceptible to less than or equal to 0.1 microgram of penicillin/ml.

Abscess↗

PubMedDate not supplied

MR spectroscopy in neurocysticercosis.

MR spectroscopy findings in a case of neurocysticercosis are presented. A combination of elevated lactate, alanine, succinate, and choline levels and reduced levels of N -acetylaspartate and creatine in a cystic intraaxial lesion in the brain helped in characterizing the lesion. To our knowledge, the short echo point resolved spectroscopic sequence (PRESS) spectrum of neurocysticercosis, as described in our case, has not been reported before.

Adult↗