Citations

This study evaluated weekly urine cultures of patients with neurogenic bladder disease who underwent intermittent urinary catheterization for bladder retraining. One group of 53 patients in 1974 received regular instillations of 0.1% neomycin after each catheterization. A similar group of 55 patients in 1975 did not receive neomycin and constituted a control group. Distribution of age, sex, diagnosis, and duration of bladder retraining was comparable in both groups. Quantitative bacterial colony counts of 10 4 to 10 5 or greater per ml of urine were considered significant. There was no difference in the incidence of bacteriuria between the neomycin-treated group and the control group (53 versus 49%, respectively), and most patients in each group had colony counts >10 5 /ml. Escherichia coli was seen less frequently in neomycin-treated patients (43.4 versus 62.5%), but a greater percentage of infections due to Pseudomonas aeruginosa , group D streptococci, and yeasts was noted in the neomycin-treated group than in the control group (41.5 versus 22.5%).

Fifty-one clinical isolates of ticarcillin-resistant, gram-negative bacilli were tested for susceptibility to combinations of ticarcillin and clavulanic acid (BRL 14151), a potent beta-lactamase inhibitor. Minimal inhibitory concentrations (MICs) were measured by a microdilution method, and minimal bactericidal concentrations for selected strains were measured by the broth dilution method. Ticarcillin MICs were ≥128 μg/ml for all and ≥512 μg/ml for 38 (75%) of the strains. Thirty-nine strains of Enterobacteriaceae tested included Escherichia coli (14), Klebsiella pneumoniae (16), Citrobacter sp. (3), Enterobacter sp. (3), Salmonella enteritidis (1), Serratia marcescens (1), and Proteus mirabilis (1). Ticarcillin MICs for 34 strains (88%) were lowered at least threefold by the addition of 1.0 μg of clavulanic acid per ml. Against 33 strains (85%), the MICs were 64 μg or less per ml in the presence of 5 μg of clavulanic acid per ml. In contrast, the MICs for seven of eight strains of Pseudomonas aeruginosa were unaffected by the addition of up to 10 μg of clavulanic acid per ml. Ticarcillin with 5 μg of clavulanic acid per ml was bactericidal against ticarcillin-resistant (MIC ≥ 2,048 μg/ml) E. coli, K. pneumoniae, Enterobacter , and P. mirabilis .

The activities of Sch 21420 and amikacin were compared in vitro against 448 clinical bacterial isolates and against 82 gentamicin-resistant isolates of gram-negative bacilli. At 1 μg/ml, Sch 21420 was more active than amikacin against most Enterobacteriaceae but less active against Pseudomonas aeruginosa . Activity of these antibiotics against gentamicin-resistant organisms varied according to the species examined.

The in vitro inhibitory activity of spectinomycin was tested against various anaerobic bacteria. Different results were obtained with different media and with different initial pH's of the media. The highest minimum inhibitory concentrations for Bacteroides fragilis ([Formula: see text] 128 μg/ml) were obtained with the use of Wilkins-Chalgren agar (pH 7.2) and Brucella blood agar (pH 7.0). Brucella blood agar at higher pH's (7.4 and 8.0) and Mueller-Hinton and Diagnostic Sensitivity Test agars produced lower minimum inhibitory concentrations (32 and 64 μg/ml). This same relationship between spectinomycin activity and pH of the medium was, in general, observed with these media and other anaerobes, including isolates of B. melaninogenicus, Fusobacterium , gram-positive cocci, Clostridium perfringens , and C. ramosum . The variable results observed in this study and in two others make it difficult to predict the clinical usefulness of spectinomycin in the treatment of anaerobic infections. It is probably most appropriate to be guided by results obtained with Wilkins-Chalgren agar and the method proposed as a reference to the National Committee for Clinical Laboratory Standards. These results indicate that spectinomycin is not a potent inhibitor of B. fragilis or other clinically significant anaerobes.

A modified procedure for the gas-chromatographic determination of 5-fluorocytosine in serum is described. A more volatile solvent mixture for extraction is used to reduce sample preparation time before chromatography. Comparison of values from assay of 12 serum samples by our method and the reference method gave a correlation coefficient of 0.99.

A procedure is described that uses high-pressure liquid chromatography for assay of gentamicin in serum. The technique involves extraction of gentamicin from serum by using a CM-Sephadex column and analysis by reverse-phase, ion-pair chromatography. Continuous-flow, post-column derivatization with o -phthaladehyde is used to form fluorescent products for detection. The possible scope of this method for analysis of other aminoglycoside antibiotics is illustrated by application to sisomicin and netilmicin.

The minimum inhibitory concentrations (MIC) of penicillin and six other antimicrobials were determined for 50 clinical isolates of Bacteroides melaninogenicus . Agar dilution susceptibilities were performed using supplemented brucella blood agar and the proposed National Committee for Clinical Laboratory Standards standard method for anaerobes; results with the two methods were comparable. A penicillin concentration ≥0.8 μg/ml was needed to inhibit 56% of the isolates, whereas 100% were susceptible to 0.1 μg of clindamycin per ml. All isolates with penicillin MIC values ≥0.8 μg/ml produced β-lactamase using a slide method. A micro-iodometric assay was used to quantitate β-lactamase production in six isolates. The β-lactamase activity of B. melaninogenicus was comparable to that of a Staphylococcus aureus isolate but was not inducible, and the specific amount produced correlated only partially with penicillin MIC values. A clinical review of patients from whom the β-lactamase-producing strains of B. melaninogenicus were isolated did not suggest any increased virulence in these strains or an unexpectedly poor clinical response to appropriate therapy.

Inhibitory activity of cephalexin, cephradine, and cefaclor was compared by the WHO-ICS agar dilution technique. Cefaclor was substantially more active against staphylococci, streptococci, gonococci, meningococci, Haemophilus, Escherichia coli, Klebsiella pneumoniae, Citrobacter diversus, Proteus mirabilis , salmonellae, and shigellae than was cephalexin, which in turn was more active than cephradine. Cefaclor appeared to be less resistant to staphylococcal penicillinase than did the other two agents. None of these cephalosporins was active against Enterobacter, Serratia , indole-positive Proteeae, Pseudomonas , or Bacteroides fragilis .

In an effort to determine the feasibility and accuracy of performing direct susceptibility tests from positive blood cultures, minimal inhibitory concentrations (MICs), determined by the agar dilution method, of direct and standardized tests with seven antibiotics were compared. Results were analyzed as to the number of very major (change in MIC from susceptible in preliminary direct testing to resistant in final standardized testing), major (change in MIC from resistant to susceptible), and minor (change in MIC without change in interpretation) discrepancies. The results for gram-positive cocci and for gram-negative bacilli were 5, 6, and 82 of 162 strains tested and 3, 12, and 79 of 90 strains tested, respectively. Of the total number of susceptibility tests compared, major and very major discrepancies occurred in only 1 and 2.4% of instances with gram-positive and -negative isolates, respectively. The majority of discrepancies were noted with Staphylococcus epidermidis (four very major, five major), Klebsiella (two very major, four major), and Alcaligenes (five major). The antibiotics most often exhibiting discrepancies were penicillin, ampicillin, and cephalothin. The results indicate that preliminary susceptibility testing directly from positive blood culture bottles is generally both feasible and accurate.

The minimal inhibitory concentrations of 601 clinical isolates of anaerobic bacteria to 10 different antimicrobial agents were determined by an agar-dilution technique. Nearly all strains were resistant to kanamycin and gentamicin, although moderate activity to both drugs was noted with Fusobacterium sp., anaerobic cocci, some strains of Bacteroides melaninogenicus , and nonsporeforming gram-positive bacilli. Chloramphenicol at 12.5 μg/ml inhibited all but three of the strains tested. Tetracycline at 6.25 μg/ml had high activity against all groups tested, with the exception that only 39% of strains of Bacteroides fragilis were inhibited at this concentration. Excluding certain species of Bacteroides , the majority of anaerobes were inhibited by penicillin at 3.1 μg/ml or less and by cephalothin at 12.5 μg/ml or less. Lincomycin at 6.2 μg/ml or less was active against nearly all strains. Erythromycin at a concentration of 3.1 μg/ml was active against B. fragilis ; however, erythromycin was less active against the other groups. Most of the minimal inhibitory concentrations of lincomycin exceeded those of clindamycin by fourfold. Rifampin inhibited virtually all strains at 3.1 μg/ml.