Yu, Pauline K. W.

An evaluation of the accuracy and convenience of the Auxotab Enteric 1 System for identification of Enterobacteriaceae was performed with 160 bacteria. Identification at the species level was correct in 134 (83.8%) instances and at the generic level in 144 (90%) instances. Sixty strains failed to achieve the minimal concentration of organisms required to complete the identification process within 7 hr. The system was judged to be laborious and to present a potential hazard to those working with it.

The characterization of 556 Micrococcaceae isolates from various clinical sources has been presented. The incidence of coagulase-negative mannitol-positive staphylococci was 3.2% and that of coagulase-positive mannitol-negative staphylococci was 1.6%. There appears to be insufficient justification for the routine reporting of staphylococcal variants from a general bacteriology laboratory, and biotyping should be reserved for special circumstances.

The in vitro activities of verdamicin and gentamicin were studied in parallel against 1,049 bacterial isolates. Verdamicin demonstrated activity similar to that of gentamicin against members of the family Enterobacteriaceae and against Pseudomonas aeruginosa at 2 and 8 μg/ml, respectively. Proteus rettgeri and Providencia stuartii were notably more susceptible to verdamicin. The new aminoglycoside was also highly active against staphylococci but was not effective against group D streptococci.

Kanamycin, BB-K8, and gentamicin were tested in parallel against 1,037 bacterial strains isolated from clinical material. The activity of BB-K8 at 20 μg/ml was comparable to that of gentamicin at 8 μg/ml against Pseudomonas aeruginosa and against Enterobacteriaceae , with the exception of gentamicin-resistant strains of Proteus rettgeri and Providencia stuartii , in which case the activities of BB-K8 and kanamycin were the same. BB-K8 exhibited little or no activity against streptococci. The activity of BB-K8 was affected by pH and inoculum size. A regression graph for inhibition data with a 10-μg disk of BB-K8 was developed, and synergistic activity of penicillin and BB-K8 against Streptococcus faecalis was tested.

The in vitro inhibitory and bactericidal activities of spectinomycin hydrochloride were tested against a variety of bacteria. The antibiotic was inhibitory at 31.2 μg/ml to most strains of Escherichia coli, Klebsiella, Enterobacter , and Staphylococcus epidermidis . Concentrations of antibiotic exhibiting bactericidal activity exceeded the inhibitory concentration by at least fourfold. Regression graphs were plotted for results obtained with 30-, 100-, 200-, and 300-μg spectinomycin discs; tentative interpretative standards are proposed.

Because excessively high rates of false resistance have been encountered with the 10-μg amikacin disk in diffusion susceptibility tests, a study was performed to examine existing zone diameter interpretative criteria and to compare the accuracy of 10- and 30-μg amikacin disks by the error rate-bounded classification scheme. Although current zone diameter interpretative criteria eliminate false susceptibles, there is an unacceptably high rate of false resistants. This problem can be resolved in most instances by revising the zone diameter interpretative criteria for the 10-μg disk (resistant, ≤9 mm; indeterminate, 10 to 11 mm; susceptible, ≥12 mm) or, preferably, by replacing the 10-μg disk with a 30-μg disk and adopting new interpretative criteria (resistant, ≤14 mm; indeterminate, 15 to 16 mm; susceptible, ≥17 mm). Because of significant differences in performance among media, it is necessary to include Pseudomonas aeruginosa ATCC 27853 among controls routinely tested and to exclude from use lots of Mueller-Hinton agar yielding results outside the 75% tolerance (90% confidence) limits for amikacin.

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.

Abstract We report a case of cerebral abscess due to Haemophilus paraphrophilus in a 51-year-old man who was otherwise healthy and had no cardiac abnormality. A source for the infection was not definitively identified; however, the patient had had dental manipulations 2 weeks before the onset of symptoms, and an oral source is probable. The patient was treated successfully with antibiotics after removal of the abscess. Bacteriological studies are discussed.