Occurrence of chloramphenicol-acetylating enzymes in various gram-negative bacilli

The occurrence of a chloramphenicol-acetylating enzyme, similar to that found in Escherichia coli, carrying an R factor was investigated in various gram-negative bacilli. The acetylated products of chloramphenicol were identified by chromatography and quantitatively assayed after benzene extraction. The investigated strains were of the Salmonella-Arizona group, the Klebsiella-Aerobacter group, Serratia marcescens, the Proteus group, and Pseudomonas aeruginosa, most of which were isolated from 1947 to 1957. Both chloramphenicol-sensitive and -resistant strains were included, but none of them was able to transfer chloramphenicol resistance by conjugation. In the Proteus group, a significant level of a chloramphenicol-acetylating enzyme was found in most strains, whether they were sensitive or resistant to chloramphenicol; the resistant strains showed higher levels of the enzyme. Some chloramphenicol-sensitive strains lacked this enzyme. Only the sensitive strains containing the enzyme could easily produce chloramphenicol-resistant mutants with higher enzyme activity. Thus, the chloramphenicol resistance of this group can be reasonably explained on the basis of the chloramphenicol-acetylating enzyme. All of the Pseudomonas aeruginosa strains were resistant to chloramphenicol, and most strains showed low levels of the enzyme (which, however, did not appear sufficient to explain their resistance). All of the strains of the other groups (except one strain of Enterobacter cloacae) lacked the enzyme, although most strains of the Klebsiella-Aerobacter group and of S. marcescens were resistant to chloramphenicol. With respect to the origin of the resistance gene of the R factor, it is noteworthy that the strains of Proteus mirabilis isolated in 1947 possessed this enzyme before the discovery of chloramphenicol.

Use of Water-Drinking Tonography in Mass Screening for Glaucoma*

The results of mass screening for glaucoma of workers in a factory in Chiba Prefecture, Japan, are reported. At the first-stage examination, tonometry was performed with standardized Schiøtz tonometers on 1,527 subjects (3,054 eyes) with no ocular symptoms. When the tension was 5.0/5.5 gm or higher, the patient was regarded as a preliminary suspect and a detailed ophthalmologic examination was recommended. The second-stage examination, in the University Clinic included campimetry, vision tests, water-drinking tonography, tonometry with applanation and Schiøtz tonometers, funduscopy and gonioscopy. Of the 239 (381 eyes) preliminary suspects, 79 came to the Clinic for the second-stage examination. Water-drinking tonography, done on 104 eyes with tension of greater than 5.0/5.5 gm, revealed that 48 had a Po/C ratio greater than 100, which strongly suggests the presence of glaucoma. In water-drinking tonography, a Po/C ratio greater than 100 was noted in about 34% of 58 eyes with a tension of 4.25/5.5-5.0/5.5 gm, suggesting that the index for separating glaucoma suspects from normals could be brought down to the level of 5.0/5.5 gm. The over-all percentage of glaucoma cases found was 1.3%. The efficacy of water-drinking tonography in mass screening for glaucoma has been discussed.