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Biomedical subjects

V Lorian

Publications and source records attributed to V Lorian.

At least 55 records · Page 3Linked to original sources
PubMed1985

Antibacterial activity in blood cultures.

A total of 2,010 blood samples inoculated into tryptic soy broth were examined for antibacterial activity by means of a bioassay plate seeded with Bacillus subtilis spores. The size of the zone of inhibition on this plate was indicative of the degree of antibacterial activity. Current antibiotic therapy was confirmed by examination of chart records. Of the 2,010 blood cultures tested, 147 (7.3%) contained detectable levels of antibiotics; of these 147, 14 (9.5%) yielded growth of bacteria, and 133 (90.5%) remained negative. When the Antibiotic Removal Device (Marion Scientific, Div. Marion Laboratories, Inc., Kansas City, Mo.) was used, it eliminated the antibacterial activity but did not improve the recovery of bacteria from these cultures. Only bacteria resistant to the respective antibiotic were recovered from blood cultures that showed high levels of antibacterial activity (beta-lactam antibiotics, greater than 0.60 micrograms/ml; aminoglycosides, greater than 2 micrograms/ml; and tetracycline, greater than 4 micrograms/ml). Blood cultures showing low levels of antibacterial activity yielded both resistant and susceptible bacteria.

Anti-Bacterial Agents↗
PubMed1985

Ultrastructure of staphylococci in respiratory infections treated with nafcillin.

A patient with a pleural effusion containing Staphylococcus aureus was treated with nafcillin. Another patient with bilateral upper lobe infiltrates which grew S. aureus from a catheter inserted through a fiberoptic bronchoscope into the lesion was also treated with nafcillin. Electron microscopy of organisms grown while the patients were receiving nafcillin showed staphylococci which were twice as large as normal and contained multiple cross-walls and normal peripheral cell walls. Such abnormal staphylococci result from exposure to subminimum inhibitory concentrations of beta-lactam antibiotics.

Adult↗
PubMed1985

Effect of pH on the morphology of Staphylococcus aureus.

Nineteen strains of Staphylococcus aureus (10 sensitive and 9 resistant to oxacillin) were grown for four hours on membranes placed on trypticase soy agar at pH 5, 5.5, 6, 6.5, 7.1, 7.5, 7.8 and 8.3. The morphology was observed by interference phase contrast and by electron microscopy. All strains grown at pH 6 to 7.5 produced cocci of normal size. When grown at pH 5, 5.5, 7.8 and 8.3, however, seven of the oxacillin-resistant strains and seven of the oxacillin-sensitive strains produced bacterial cells 1.5 to 2 micron in diameter. These cells consist of a cluster of staphylococci held together by multiple thick cross walls. Their structure is similar to that of staphylococci grown in the presence of subminimum inhibitory concentrations of beta-lactam antibiotics, which inhibit autolysis of cross walls. It appears that autolysis of cross walls of S. aureus is also inhibited by a low or a high pH.

Autolysis↗
PubMed1985

Bacterial resistance to antibiotics in American hospitals.

A total of 5,825,243 strains of bacteria were isolated in 242 American hospitals during a period of twelve years (1971 to 1982). The susceptibility to antibiotics of Escherichia coli, Staphylococcus aureus, Klebsiella sp. Proteus mirabilis, Haemophilus sp. and Pseudomonas sp. did not change significantly during this period of time. The susceptibility to tetracycline for E. coli and S. aureus increased. Streptococcus faecalis and Staphylococcus epidermidis showed a decrease in susceptibility.

Anti-Bacterial Agents↗
PubMed1984

Bactericidal effect of polymorphonuclear neutrophils on antibiotic-induced filaments of gram-negative bacilli.

Exposure of strains of Escherichia coli to ampicillin and mezlocillin and of strains of Pseudomonas aeruginosa to azlocillin and cefsulodin caused the bacilli to elongate into filaments. The bacilli and their filaments were incubated with fresh human polymorphonuclear neutrophils (PMNs), and the phagocytic process was recorded by means of phase-contrast microscopy. The bactericidal effect of PMNs on both filaments and bacilli was quantitated by counts of colony-forming units. A single PMN phagocytized one or more filaments, some of which were as long as 90 micron and contained as many as 20 genomes. Two predominant patterns of phagocytosis of filaments were observed. When the ratio of bacteria to PMNs was low (0.2-1.8), the rate of killing was 62%-81%. When the ratio was higher (5-12), the rate of killing of both filaments and bacilli was lower. As an alternative to colony-forming units, cell mass was used as a gauge of phagocytic activity. The relative mass of killed filaments was considerably greater than that of killed bacilli; this finding indicated that filaments were much more susceptible than were bacilli to the bactericidal activity of PMNs.

Ampicillin↗
PubMed1984

Staphylococcal endocarditis in rabbits treated with a low dose of cloxacillin.

Rabbits with established staphylococcal endocarditis, injected twice at an interval of 2 h with either 0.5 mg of cloxacillin per kg or saline, were sacrificed 2.5 h after the second injection. Vegetations were excised, weighed, and cultured, and ultrathin sections were prepared and examined by light microscopy, transmission electron microscopy, and scanning electron microscopy. Several affected valves were examined histologically. Concentrations of cloxacillin in serum were determined 1 and 3 h after dosage. Staphylococci grown on membranes placed on agar containing 0.09 micrograms of cloxacillin per ml and in broth at the same cloxacillin concentration (one-third of the MIC) were examined by transmission electron microscopy. The mean numbers of CFU per gram of vegetations from control and treated rabbits were 2.28 X 10(10) and 1.31 X 10(10), respectively. Vegetations of treated rabbits contained staphylococci of normal size and form as well as organisms two to six times larger than normal with multiple cross walls. Larger bacterial cells were usually located in areas close to blood; cells of normal size were usually embedded in fibrin. The structures of these staphylococci and those grown on membranes in the presence of 0.09 micrograms of cloxacillin per ml were comparable but were different from those grown in broth containing this concentration of cloxacillin. Concentrations of cloxacillin in serum were 0.166 micrograms/ml at 1 h and 0.286 micrograms/ml at 3 h after dosage. The similarities in ultrastructure between staphylococci in vegetations of treated rabbits and staphylococci grown on membranes suggest that the vegetations contained approximately 0.09 micrograms of cloxacillin per g. Thus, antibiotic penetration from blood into vegetations and diffusion into fibrin were limited.

Animals↗
PubMed1984

Antimicrobial agent susceptibility patterns of bacteria in hospitals from 1971 to 1982.

Bacterial susceptibility to 16 commonly used antibiotics was analyzed for a 12-year period (from 1971 to 1982, inclusive). Susceptibilities of 5,828,243 strains isolated from a mean of 242 hospitals nationwide and of 194,575 strains isolated at the Massachusetts General Hospital, Boston, Mass., and the Bronx Lebanon Hospital Center, New York, N.Y., were compared. Strains of Escherichia coli, Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa showed virtually the same susceptibilities to antibiotics throughout the 12-year period, whereas Streptococcus faecalis and Staphylococcus epidermidis showed significant increases in resistance to most antibiotics. The close similarity between antibiotic susceptibilities shown at both the 242 hospitals and the 2 individual hospitals suggests that this analysis accurately reflects trends of bacterial resistance to antibiotics in U.S. hospitals. Since most of the species analyzed produce serious disease and high mortality, their susceptibility to antibiotics is relevant both to physicians treating infectious diseases and to epidemiologists.

Anti-Bacterial Agents↗
PubMed1983

Phagocytosis of filaments of Escherichia coli produced with mezlocillin.

The phagocytosis of filaments of Escherichia coli produced with mezlocillin differs from the phagocytosis of normal bacilli in that pseudopods are employed for bacilli, but the entire body of the polymorphonuclear cell (PMN) participates in the engulfment of a filament. A single PMN was observed phagocytizing one or more filaments 20-50 micron long. The mass of a filament is about ten times larger than the mass of a bacillus. When equal bacterial mass, one filament or 10 bacilli, is exposed to PMNs comparable bacterial killing results after 2-3 h of incubation.

Blood Bactericidal Activity↗
PubMed1982

Effects of ten milligrams of ampicillin per day on urinary tract infections.

A total of 20 patients with symptomatic urinary tract infections (greater than 10(5) colony-forming units of Escherichia coli per ml of urine in addition to pyuria) received 10 mg of ampicillin and 2 liters of fluid daily for 3 days. After 2 days, 16 patients had culture-negative urine without pyuria. A total of 18 similar patients received only 2 liters of fluid for 3 days. On day 4, all had greater than 10(5) colony-forming units of E. coli per ml of urine and greater than 10(4) leukocytes per mm3 of urine.

Adolescent↗
PubMed1982

Determination of the range of antibacterial activity by use of viable counts.

The activity of three aminoglycosides and six beta-lactam antibiotics on strains of Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Staphylococcus aureus, and enterococci was studied. The minimal inhibitory concentrations (MICs), the minimal bactericidal concentrations (MBCs), and the minimal antibiotic concentrations (MACs) were determined after 5 h of incubation in broth cultures by colony-forming-unit counts. The MICs were also determined by agar dilution after 24 h of incubation. The MICs on agar after 24 h of incubation were higher than those in broth after 5 h of incubation. The differences ranged from 1.1- to 14.2-fold, but in most cases were only three- to fivefold (P less than 0.05 to less than 0.001). The MBCs at 5 and 24 h were comparable in 71% of tests. For current practice, the MBC of enterococci can be determined after 5 h of incubation with antibiotics. The aminoglycosides showed MBCs which were closer to the MICs than were those of the beta-lactam antibiotics, which required a higher multiple of the MIC to show a bactericidal effect. The MBCs of oxacillin and cefamandole for S. aureus after 5 h of incubation were greater than 128 times the respective MICs. The MACs ranged from 1/1.5 to 1/7 of the 5-h MICs. The three endpoints, MIC, MBC, and MAC, indicate the antibacterial range of an antibiotic in terms of inhibition of growth and bacterial survival. The data suggest that the antibacterial range of an antibiotic is similar for most strains of a given species and is, to some extent, a characteristic of similar antibiotics.

Aminoglycosides↗
PubMed1982

Abnormal morphology of bacteria in the sputa of patients treated with antibiotics.

Filaments of Klebsiella pneumoniae were observed by Gram stain in the sputum of a patient with a respiratory infection who was treated with half the usual dose of cefazolin. Identical filaments were observed in vitro when this strain was incubated with subminimum inhibitory concentrations of cefazolin. Large gram-positive cocci containing multiple cross walls were observed by electron microscopy in the sputum of a patient with a respiratory infection who was treated with ampicillin and gentamicin. Antibiotic administration was suspended the night before the sputum was obtained. The ultrastructure of these cocci was very similar to the ultrastructure of Staphylococcus aureus incubated with subminimum inhibitory concentrations of cephaloridine or oxacillin. It was suspected that the low dose of cefazolin and the intermittent therapy with ampicillin resulted in a subminimum inhibitory concentration of antibiotic in the respiratory tract which induced the the abnormal morphology of the bacteria observed in the sputum of both patients. The presence of abnormal forms of bacteria in the specimen of a patient, rather than in the culture of a specimen, has clinical significance.

Aged↗
PubMed1980

Killing of oxacillin-exposed staphylococci in human polymorphonuclear leukocytes.

Twelve strains of Staphylococcus aureus isolated from patients and two collection strains were grown on membranes placed on agar containing subminimal inhibitory concentrations of oxacillin. Clusters of staphylococci held together by thick cross walls resulted. These organisms, as well as the same strains grown in the same way on drug-free medium (control), were eluted from the membranes and were incubated with human polymorphonuclear leukocytes (PMNs) from various donors. Phagocytosis was comparable for both staphylococci exposed to oxacillin and control staphylococci, but the killing effect was different. The staphylococci grown on membranes in the presence of oxacillin were less susceptible to killing than the control staphylococci, but the killing effect was different. The staphylococci grown on membranes in the presence of oxacillin were less susceptible to killing than the control staphylococci. After 0.5 and 1 h of incubation with PMNs, the killing rates for oxacillin-grown versus control staphylococci were 52 and 70% and 65 and 85%, respectively (P < 0.01). After 2 and 3 h of incubation, the killing was similar. Most clusters of staphylococci contain a few individual cells that are located in the center of the cluster and are surrounded by other staphylococci; therefore, they are protected from adverse agents in the environment. This could explain why the phagocytized clusters are less susceptible than control staphylococci to the killing effect of PMNs during the first hour of incubation. Oxacillin does not penetrate into PMNs and in the absence of the drug the cross walls lyse, liberating the constituent staphylococci. This coincides with the increase in the percentage of cluster killing by PMNs after 2 and 3 h of incubation.

Adult↗
PubMed1980

Discrepancies between results obtained by agar and broth techniques in testing of drug combinations.

One hundred strains of Staphylococcus epidermidis were tested by the double-disk agar diffusion method for their susceptibility to cephalothin, to sulfamethoxazole-trimethoprim, and to combinations of these drugs. Forty-five strains showed a bridging inhibition zone between the two disks, suggesting a synergistic effect of the combination of cephalothin plus sulfamethoxozole-trimethoprim against these strains. Ten of these strains were retested against the individual drugs and their combination by the twofold broth dilution method. No strain showed higher susceptibility to any combination as compared with cephalothin alone.

Cephalothin↗
PubMed1979

Minimal antibiotic concentrations of aminoglycosides and beta-lactam antibiotics for some gram-negative bacilli and gram-positive cocci.

The minimal antibiotic concentration (MAC) is the lowest concentration of an antibacterial agent that produces a decrease of 1 log in the number of organisms/ml as compared with a control culture in drug-free medium. Various gram-negative bacilli and gram-positive cocci were grown in the presence of amikacin, gentamicin, tobramycin, ampicillin, amoxicillin, oxacillin, carbenicillin, ticarcillin, and cefamandole at concentrations varying from eight times the minimal inhibitory concentration (MIC) to 1/128 of the MIC. Colony forming units (cfu) were counted, the MIC was determined, and the MIC:MAC ratio, which indicates the magnitude of the effective range, was calculated. The MIC:MAC ratio appears to be characteristic for a given species and antibiotic. There is no relation between the MICs and the MIC:MAC ratios. The highest ratios were given by Proteus mirabilis with aminoglycosides (MIC:MAC mean, 29.2 with tobramycin), and the lowest ratios were given with beta-lactam antibiotics by Pseudomonas aeruginosa and Streptococcus faecalis (MIC:MAC means, 2.1 with carbenicillin and cefamandole, respectively).

Aminoglycosides↗
PubMed1979

A five-hour system for identification of bacteria.

A five-hour protocol was compared with routine methods for identification and antibiotic susceptibility determination of bacteria from clinical specimens. A total of 9551 urine, wound, sputum, and throat cultures were processed using both procedures. The identifications reported less than 24 hours after the laboratory received the specimen were comparable to those obtained by routine methods for 87 to 95 percent of the Enterobacteriaceae, 90 percent of the staphylococci and enterococci, but less than 50 percent of the unusual species such as Providencia, P. maltophilia, or Acinetobacter. Susceptibility test results were reported after five hours' incubation for 97 percent of all stains examined except for P. aeruginosa where early results were obtained for only 71 percent of the strains. This protocol allows bacteriologic identification and antibiotic susceptibility determination within 24 hours of specimen receipt; therefore, appropriate antibacterial therapy for the patient's immediate needs can be started in a shortened period.

Bacteriological Techniques↗