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Biomedical subjects

D Barba

Publications and source records attributed to D Barba.

At least 37 records · Page 2Linked to original sources
PubMed1987

Microbiological properties of sulbactam combined with ampicillin.

Several in vitro parameters of sulbactam combined with ampicillin (Sbt/Amp) were studied in order to evaluate and compare its microbiological properties with those of beta-lactamase stable beta-lactams (ceftriaxone, cefamandole, cefoxitin). The intrinsic activity of Sbt/Amp was satisfactory and comparable to that of other beta-lactams and no significant difference was observed against beta-lactamase producing or non-producing bacteria. Besides, it was determined that sulbactam, when combined with ampicillin at different ratios (1:2, 5:1), with and without preincubation (60 min) reduces the hydrolysis of ampicillin determined by ten different standard beta-lactamases. The hydrolysis rates of ampicillin become as low as those of cefoxitin, cefamandole and ceftriaxone, which are beta-lactamase stable cephalosporins. In fact, all the antibiotics under examination were slightly hydrolyzed by several beta-lactamases, but such slight hydrolysis did not affect the antibacterial activity against beta-lactamase producing bacteria. About 50% of non-beta-lactamase producing bacteria (18 strains of different bacterial species) produced an inducible beta-lactamase after ten daily subcultures with sub-inhibitory concentrations of each antibiotic, but minimum inhibitory concentrations (MICs) of Sbt/Amp never increased after stimulation in contrast with other drugs whose MICs were much higher in consequence of this procedure. Finally, no spontaneous resistant mutant to Sbt/Amp was detected, but several mutants appeared in response to the other drugs. Sulbactam makes ampicillin as effective as beta-lactamase stable cephalosporins and its use does not determine an increase of resistance or selection of resistant mutants.

Ampicillin↗
PubMed1987

Intestinal microflora changes induced by ciprofloxacin and treatment of portal-systemic encephalopathy (PSE).

The modifications of colon microflora in 14 patients under oral ciprofloxacin therapy for intercurrent UTIs or RTIs, at the dose of 250 mg b.i.d. or 500 mg o.d. were examined. All patients were affected by liver cirrhosis. A marked decrease in enterobacteria with both doses was noticed in the first few days, with a complete disappearance from days 3-6 of therapy and a return to normal within 2 weeks after interruption of treatment. Gram-positive and Gram-negative aerobic and anaerobic flora were not affected significantly. As a consequence of these results, the treatment of six patients affected by PSE (grade 2-3) was studied, testing the colon microflora changes, the presence of circulating endotoxins and blood ammonium levels before, during and after 12 days of therapy. A marked reduction or suppression of enterobacteria was observed, and a prompt normalization of blood ammonium levels, the disappearance of circulating endotoxins and a clear clinical improvement in 5 out of 6 patients.

Aged↗
PubMed1987

Ciprofloxacin concentrations in human fluids and tissues following a single oral dose.

Ciprofloxacin is a new quinolone carboxylic acid derivative which exerts its antibacterial activity at very low concentrations against a wide spectrum of microorganisms. Ciprofloxacin serum and urine concentrations were studied in 10 healthy volunteers after a single 250 and 500 mg oral dose. The concentration in ascitic fluid was determined in four male patients undergoing paracentesis after a single oral 250 mg dose (two patients) and 500 mg dose (two other patients). The penetration of ciprofloxacin into the human tonsils and turbinate bones was also determined in eight patients undergoing tonsillectomy or turbinectomy 3 h after a single oral 250 mg administration. Ciprofloxacin concentrations were determined by an agar diffusion test utilizing E. coli as reference strain. Ciprofloxacin is rapidly absorbed after oral administration (Ka = 2.67 and 1.93 mcg/ml) and its serum concentration does not vary significantly with sex and dosage (Cmax = 2.61 and 1.99 mcg/ml after a single 500 mg and 250 mg oral dose). Urinary concentrations of ciprofloxacin are twice higher after a single 500 mg dose than after a 250 mg one and are still high after 24 h (37.2 and 25.3 mcg/ml). The concentrations of ciprofloxacin in ascites, tonsils and turbinate bones are several times higher than its MICs against the majority of Gram+ and Gram- aerobic bacteria. The in vitro activity of ciprofloxacin and its human pharmacology suggest a twice daily 250 of 500 mg dosing for infections caused by multiple antibiotic-resistant bacteria, and a once a day dose in the treatment of urinary tract infections.

Administration, Oral↗
PubMed1986

Supratentorial ependymomas. Neuroimaging and clinicopathological correlation.

In 10 patients with supratentorial ependymomas, the tumors exhibited hyperdensity on computerized tomography (CT) scanning prior to contrast infusion and, with one exception, all tumors were mixed lesions with the low densities suggesting cystic or necrotic portions. Eighty percent of the tumors contained small calcifications. Characteristically, the tumors were well demarcated and demonstrated moderate to marked enhancement after the intravenous administration of contrast material. Angiograms obtained in some patients showed mild hypervascular tumor staining and absence of large feeding arteries. The degree of contrast enhancement, angiographic vascularity, and tumor stain was compared to the pathological anaplasia of the tumors. No correlation was observed. Of four patients who were still alive during a follow-up period of 4 years or longer, three had recurrences with inoperable tumors; the remaining patient is without recurrence after craniospinal radiation. This same patient belonged to a group of five patients with a diagnosis of high-grade ependymoma, four of whom had recurrence. Follow-up CT accurately recorded the clinical course of each patient. Annual routine follow-up examinations are proposed for patients with low-grade ependymomas, and for those with high-grade ependymomas follow-up CT should be performed every 6 months. The characteristic appearance and behavior of these tumors include several distinctive features on angiographic and CT images.

Adolescent↗
PubMed1986

In vitro microbiological properties of mezlocillin compared with four cephalosporins.

The intrinsic activity, antibacterial spectrum and beta-lactamase stability of mezlocillin were determined and compared with that of four other beta-lactams: ceftriaxone, ceftizoxime, cefotaxime, cefuroxime. These parameters were studied by determining the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) against 397 gram-negative bacteria including Pseudomonas sp. and 124 gram-positive cocci, utilizing 10(5) and 10(7) CFU/ml bacterial concentrations. The sensitivity to ten different standard beta-lactamases was determined by a spectrophotometric method that utilizes the velocity of cytochrome c reduction. Mezlocillin was hydrolyzed, at different degrees, by all the beta-lactamases under examination (TEM 1, TEM 2, OXA1, OXA2, OXA3, S + A, P99, STH4, SHV1, K1) but such hydrolysis did not affect its bactericidal activity which was similar to that of the other beta-lactamase-stable beta-lactams. In addition MBC/MIC ratios were very low and the differences of MIC values at different bacterial inocula were not significant. We also studied the stimulation of inducible beta-lactamases by subinhibitory doses of antibiotics, the eventual changes of antibiotic susceptibility after these stimulations and, finally, the frequency of spontaneous resistant mutants. Mezlocillin stimulated the production of inducible beta-lactamases in 50% of the bacteria examined, but in contrast with the other drugs tested, no increase of MICs occurred nor did mezlocillin select resistant mutants.

Bacteria↗
PubMed1986

Inhibitory and bactericidal activity of cefmetazole and seven other beta-lactams against different bacterial inocula.

The determination of the minimal inhibitory concentrations (MICs) at different bacterial inocula represents an important factor in determining the potential effectiveness of new antibiotics. MICs at different inocula (10(5) and 10(7) CFU/ml) and minimal bactericidal concentrations (MBC) of cefmetazole and seven other new cephalosporins (ceftazidime, ceftizoxime, cefamandole, ceftriaxone, cefotaxime, cefuroxime, cefoxitin) were determined by a miniaturized dilution broth method against a wide range of gram-positive, gram-negative and non-fermentative bacteria. The results of the present investigation confirm that all the beta-lactams under examination including cefmetazole exert a good or satisfactory antibacterial activity against gram-positive and gram-negative bacteria; and that only ceftazidime possesses antipseudomonas activity. MBCs and MICs at heavy inoculum are two times higher than MICs at light inoculum. These results could explain the spread by different mechanisms of bacteria resistant to beta-lactam antibiotics.

Bacteria↗
PubMed1986

Correlation of beta-lactamase stability and antibacterial activity of beta-lactams in beta-lactamase-producing bacteria and respective transconjugants.

A total of 343 Gram-negative bacteria were isolated and identified from urine specimens of patients with urinary tract infections. All the bacteria were investigated for their production of beta-lactamases by the nitrocefin test. beta-lactamase-producing strains were tested by the Datta method to detect any transfer of beta-lactamase production to a receiving E. coli K12 RN-strain. MICs of six beta-lactamase-stable compounds (ceftazidime, ceftriaxone, cefamandole, cefoxitin, cefotaxime, cefuroxime) were determined against all the beta-lactamase transferring bacteria and their respective transconjugants by a miniaturized dilution broth method. beta-lactamases produced by donors and transconjugants were purified and identified by determination of the isoelectric point by focusing; their hydrolytic activity was assessed by a spectrophotometric method using cytochrome c reduction. A total of 129 bacteria out of 343 produced beta-lactamases and 27 of these transferred the beta-lactamase production by conjugation. The beta-lactamases isolated from donors and transconjugants had the same pl and the same substrate profile. Ceftazidime was more stable to all the beta-lactamases isolated and more active against all the bacteria examined than the other compounds.

Anti-Bacterial Agents↗
PubMed1986

Ciprofloxacin in the treatment of urinary and respiratory tract infections in patients with chronic liver disease.

The clinical efficacy and tolerability of ciprofloxacin (Bay o 9867), a new quinolone compound with broad antibacterial spectrum, was evaluated in 28 patients hospitalized in the first Clinic of Infectious Diseases, University of Naples, Italy, for chronic liver disease and affected by respiratory (RTI) or urinary tract infections (UTI). Ciprofloxacin was administered at the dosage of 500 mg twice a day after the isolation of the organism responsible for the infection and after the determination of its sensitivity in vitro to ciprofloxacin. The therapy was carried on for 5-10 days depending upon the severity of infection and clinical evaluation. Bacteriological cultures and hematochemical analysis were always performed during and after the therapy. Ciprofloxacin was very effective in all the treatments of UTI and RTI under examination, both for the disappearance or improvement of clinical signs and for eradication of the responsible microorganisms. No significant side effects or change in the hematochemical tests were observed.

Adult↗
PubMed1986

Antibacterial activity of six beta-lactams and six quinolones against urinary gram negative bacteria.

Three hundred eighty seven gram negative bacterial strains were isolated from urine specimens of as many patients affected by urinary tract infections. Susceptibility of bacteria to six quinolones (ciprofloxacin, norfloxacin, oxolinic, nalidixic, pipemidic acid and cinoxacin) and six beta-lactams (ceftazidime, ceftizoxime, ceftriaxone, cefamandole, cefoxitin and cefotaxime) was studied determining the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) of each compound by a miniaturized dilution broth method. Ciprofloxacin, a quinoline carboxylic acid compound structurally related to nalidixic acid, and ceftazidime a new beta-lactamase stable beta-lactam showed a much higher antibacterial activity against all the bacterial strains including Pseudomonas. The best antibacterial activity of ciprofloxacin and ceftazidime was expressed either by the lower MICs and lower MBCs with respect to those of the other compounds or by a low MBC/MIC ratio, which represent an important clinical advantage in clinical practice.

Anti-Bacterial Agents↗
PubMed1985

Comparative in vitro activity of ciprofloxacin and five other quinoline derivatives against gram-negative isolates.

A total of 375 Gram-negative bacterial strains were isolated from midstream urine specimens of the same number of patients affected by urinary tract infections. All bacteria were identified by standard bacteriological methods and their susceptibility to six quinoline derivatives (ciprofloxacin, cinoxacin, norfloxacin, oxolinic acid, pipemidic acid, nalidixic acid) was studied by determining the MICs and MBCs for each compound using a miniaturized dilution broth method in microtitre plates and twofold dilutions of each drug from 256 to 0.12 mcg/ml. Ciprofloxacin, a new quinoline carboxylic acid compound structurally related to nalidixic acid, showed a much higher antibacterial activity against all bacterial strains under examination, including Pseudomonas, than the other compounds, except for norfloxacin. The MIC90 and MBC90 of ciprofloxacin never exceeded 1 mcg/ml with any of the bacterial species; and MBC/MIC ratios were very low, which represents an important clinical advantage. Only norfloxacin showed comparable effectiveness. No bacterial strain showed resistance to the drug and the MIC90 and MBC90 never exceeded 8 mcg/ml.

Bacteriuria↗
PubMed1985

Cross resistance of quinolone derivatives in gram-negative bacteria.

A total of 127 Gram-negative bacteria resistant to nalidixic acid were isolated from as many patients affected by urinary tract infections and hospitalized in the first Clinic of Infectious Diseases, University of Naples. Enterobacteria were identified by Enterotube system (Roche) and API 20 system (Ayerst). Non-fermentative bacteria were identified by OXI/FERM system (Roche). The following bacteria were collected: Escherichia coli 50, Proteus spp. 35, Enterobacter agglomerans 12, Serratia sp. 5, Pseudomonas aeruginosa 25. The in vitro antibacterial activity of nalidixic acid and three other quinoline derivatives (pipemidic acid, oxolinic acid and ciprofloxacin) were studied by determining the MICs by a miniaturized dilution broth method. The MICs were compared to evaluate the eventual cross resistance to the drugs under examination within each bacterial species. The results showed that 23% of bacteria were resistant to nalidixic acid, pipemidic acid and oxolinic acid; 49.6% to nalidixic and pipemidic acid and 0.7% to nalidixic acid and oxolinic acid. On the other hand none of the bacteria were resistant to ciprofloxacin. The last showed very low MICs against all the bacteria under examination, including Pseudomonas and Serratia. The high antibacterial activity of ciprofloxacin even against bacteria highly resistant to the other quinolines could be due to a greater affinity of the target sites or to the better permeability of resistant strains to the newer drug or because it is unaffected until now by mutations of genes responsible for cross resistance.

Ciprofloxacin↗
PubMed1985

Occurrence of gram negative bacteria in midstream bladder urine and their sensitivity to quinoline derivatives.

326 gram negative bacteria have been isolated and quantitative bacteria counts performed from midstream urine of as many patients affected with symptomatic and non symptomatic urinary tract infections. Susceptibility of bacteria to four quinoline derivatives (Norfloxacin, Oxolinic acid, Pipemidic acid and Nalidixic acid) was studied determining the minimal inhibitory concentrations (MICs) of each drug by a miniaturized dilution broth method. The frequency of bacterial species isolated, the frequency of symptoms and the frequency of bacterial counts were studied to establish a possible relationship between these data. It has been observed that patients affected with pyuria without any other subjective symptoms demonstrate a colony count ranging between less than 10(4) and greater than 10(5) bacterial/ml of urine and these bacteriuria were determined by several different bacterial species. E. coli was much more frequently responsible for low or high count bacterial infections of the urinary tract than other species. In fact E. coli was detected in 64.4% of patients, P. mirabilis in 15.9%, E. agglomerans in 5.2%, P. aeruginosa in 4.9. Other species were detected in much lower percentages. Norfloxacin proved to be the most effective drug in vitro, out of those under examination. Its MIC50 never exceeded 8 mcg/ml even against Pseudomonas and Serratia strains, which were resistant to all the other antimicrobial agents.

Adolescent↗
PubMed1985

Comparative activity of ceftizoxime and four other cephalosporins against gram negative bacteria and their sensitivity to beta-lactamases.

The in vitro activity of ceftizoxime compared with other beta-lactamase stable compounds was assessed against recent urinary gram negative isolates. 343 bacterial strains were isolated from patients affected by UTI, identified by standard bacteriological methods and investigated for their production of beta-lactamases by Nitrocefin test. MICs and MBCs of ceftizoxime, ceftriaxone, cefamandole, cefoxitin and cefotaxime were determined by a miniaturized dilution broth method against all beta-lactamase producing bacteria (129 out of 343). Sensitivity of antibiotics to beta-lactamases isolated and semi-purified by ultrasonic disruption and high speed centrifugation was assessed by a spectrophotometric method. In vitro antibacterial activity of each antibiotics was correlated to their sensitivity to isolated beta-lactamases. Ceftizoxime showed lower MIC and MBC values and lower MBC/MIC ratio than the other compounds against all the bacteria including Pseudomonas. Ceftizoxime was not hydrolized by any isolated beta-lactamase.

Cefotaxime↗
PubMed1984

The occipital transtentorial approach to the posterior fossa in the pediatric patient.

The occipital transtentorial approach to the high posterior fossa has been previously described for the adult neurosurgical patient. In this presentation 5 pediatric patients with differing pathology in the posterior fossa are reported following successful occipital transtentorial operations. The advantages of this approach over the suboccipital route for microneurosurgery are discussed.

Astrocytoma↗
PubMed1984

Success of microvascular decompression with and without prior surgical therapy for trigeminal neuralgia.

Clinical records and patient interviews in 37 cases of trigeminal neuralgia treated by microvascular decompression by a single surgeon were studied retrospectively. Outcomes were determined with an average follow-up period of 43 months. Abnormalities in the region of the trigeminal nerve were identified in each case. Patients undergoing microvascular decompression as a primary procedure were cured (total pain relief without further therapy) at a rate of 91%, versus 43% in patients treated with destructive procedures (rhizotomies) prior to microvascular decompression (p less than 0.005). Analysis also suggests that trigeminal neuralgia of greater than 9 years' duration was cured at a rate of only 42%, versus 88% in cases of less lengthy duration (p less than 0.005). Sex and age at time of surgery were not significant predictors of outcome. There were no deaths in this group of patients aged from 32 to 90 years. A horizontal surgical approach is described.

Adult↗
PubMed1984

Comparative in vitro activity of norfloxacin and four other chemotherapeutics against urinary gram-negative isolates.

Three hundred seventy-five Gram-negative bacterial strains were isolated from urine specimens of as many patients affected by symptomatic or asymptomatic urinary tract infections. Susceptibility of bacteria to five chemotherapeutics (norfloxacin, oxolinic acid, pipemidic acid, nalidixic acid and nitrofurantoin) was studied determining minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of each compound by a miniaturized dilution broth method. Norfloxacin, a quinoline carboxylic acid compound structurally related to nalidixic acid, showed a much higher antibacterial activity against all bacterial strains under examination including Pseudomonas sp. The best activity of norfloxacin was expressed either by lower MICs and lower MBCs with respect to those of the other compounds, or by a low MBC/MIC ratio, which represents an important advantage in clinical practice.

Anti-Infective Agents, Urinary↗