Hideomi Nakahara

Mercury Resistance and R Plasmids in Escherichia coli Isolated from Clinical Lesions in Japan

The mercury and antibiotic resistance of 338 strains of Escherichia coli isolated from hospital patients was determined. Resistance to mercury was found in 58.6% of the isolates. The frequencies of resistance to streptomycin (Sm), tetracycline (Tc), chloramphenicol (Cm), kanamycin (Kan), cephaloridine (Cer), and gentamicin (Gm) were 66.3, 60.3, 56.5, 42.9, 32.1, and 1.5%, respectively. Among the above, 198 mercury- and antibiotic-resistant isolates were selected and tested for their ability to transfer the resistance to susceptible strains of E. coli K-12 and Klebsiella pneumoniae JK5. R plasmids carrying mercury resistance were demonstrated in 89.9% of the mercury-resistant strains of E. coli. Furthermore, R(Hg,Sm,Tc,Cm) plasmids were demonstrated most frequently, followed by R(Hg,Sm,Tc,Cm,Kan), R(Hg,Cm,Kan), and R(Hg,Sm,Tc,Cm,Kan,Cer) plasmids.

Mercuric reductase enzymes from Streptomyces species and group B Streptococcus

Mercury volatilization (Hg2+ reductase) activity has been found with Hg2+-resistant isolates of three Streptomyces species and with three Hg2+-resistant strains of group B Streptococcus from clinical sources in Japan. Hg2+ reductase activities in crude cell extracts showed the temperature sensitivity, the requirement for an added thiol compound and the characteristic dependence on NAD(P)H cofactors of similar enzymes isolated from other bacteria.

A Bacteriological Study on Children with Staphylococcal Toxic Epidermal Necrolysis in Japan

From 1973 to 1976, 21 patients with staphylococcal toxic epidermal necrolysis were admitted to the Jikei University Hospital in Tokyo. Of all of them were isolated coagulase-positive Staphylococcus aureus from various sites. In Japan, unlike in Europe and America, phage group II cocci were found in few cases. On the other hand, S. aureus belonging to other phage groups than group II (I, III mixed group and III group) were very commonly isolated. All the isolates produced exfoliatin which was capable of producing exfoliation in newborn mice. The type (A or B) of exfoliation which was detected by the antiserum agar method did not correlate to the severity of this disease.

Volatilization of mercury compounds by methylmercury-volatilizing bacteria in Minamata Bay sediment.

Minamata Bay has been heavily polluted by high mercury concentrations which gave rise for a long time to methylmercury poisoning, Minamata disease (Kutsuna 1968; Irukayama 1977). The mercury still exists in the sediments of the Bay. The population of mercury-resistant bacteria in the sediments of Minamata Bay is larger than that in the sediments of other marine environments. The mercury-resistant bacteria isolated from a marine environment have been found to transform organic and inorganic mercury compounds into mercury vapor. The mercury-resistance confirmed in various bacterial genera has been shown to be plasmid-mediated volatilization. However, there has been little definitive information on the volatilization of organic mercury by the bacteria living in the mercury-polluted environment. It is important to know what bacterial transformations of mercury have been taking place and how the mercury-resistant bacteria may be playing a role in the mercury cycle in the marine environment of Minamata Bay. The object of the present study is to clarify the characteristics of the methylmercury-volatilizing bacteria in the sediments of Minamata Bay and of the volatilization of various mercury compounds by these bacteria.

Chlorhexidine resistance in Escherichia coli isolated from clinical lesions

Clinical isolates of Escherichia coli (148 strains) were studied for their resistance to chlorhexidine, six antibiotics and three metals. The distribution pattern of their susceptibility to chlorhexidine clearly revealed two peaks, and the resistance was differentiated by 5 micrograms/ml of chlorhexidine. Resistance to chlorhexidine was found in 12.8% of the isolates. The frequencies of resistance to SM, TC, CP, KM, CER, GM, Hg, Cd and As were 43.2, 36.4, 18.9, 25.0, 16.2, 4.1, 35.1, 91.2 and 47.2%, respectively. The frequency of chlorhexidine resistance was lower than that of drug and metal resistance except in the case of GM resistance. Furthermore, all of these chlorhexidine-resistant strains were multiple-drug-resistant also multiple-metal-resistant.

Survey of Resistance to Metals and Volatilization Activity of Hg-Resistant R Plasmids in Citrobacter Isolated from Clinical Lesions in Japan

Clinical isolates of Citrobacter (277 strains) were studied for the resistance to four metals and four drugs. The distribution patterns of their susceptibility to Hg, Cd and As clearly revealed two peaks, but only a single peak of resistance to Pb. The frequencies of resistance to Hg, Cd, As, SM, TC, CP and KM were 31.8, 94.2, 57.8, 51.3, 44.8, 35.7 and 28.9%, respectively. And we selected 88 mercury resistant strains, and they were tested for their ability to transfer the resistance to the mercury and drug sensitive recipients of E. coli K12-ML1410-Nx and E. coli JE17-Rif. Among 88 strains of Hg resistant Citrobacter, 80 R plasmids with Hg resistance could be demonstrated. It should be noted that transferable R plasmids with Hg resistance were demonstrated in 91% of the Hg-resistant isolates. Furthermore, we tested the volatilization of mercury by strains containing these mercury resistance plasmids, by using radioactive 203Hg2+. All of these isolates of Citrobacter have volatilization activity of Hg2+. Also, all of these volatilization activity is inducible.

Immunological properties in staphylococcal toxic epidermal necrolysis.

The analysis of host defenses in 4 patients with staphylococcal toxic epidermal necrolysis revealed normal serum immunoglobulin levels, but a deficiency in cell-mediated immunity as detected by the tuberculin reactions. We suspected that the transient deficiency of cell-mediated immunity may have contributed to the development of this disease.

Benzethonium Chloride Resistance in Pseudomonas aeruginosa Isolated from Clinical Lesions

The benzethonium chloride resistance of 341 strains of Pseudomonas aeruginosa isolated from Jikei University Hospital was determined. The distribution pattern of the susceptibility to benzethonium chloride clearly revealed two peaks, and the resistance was differentiated by 1000 micrograms/ml (0.1%) of benzethonium chloride. The frequency of resistance to benzethonium chloride was 51.6%. Furthermore, the frequencies of resistance to SM, TC, CP, KM, GM, PIP, Hg, Cd, As and chlorhexidine were 42.5, 15.8, 41.3, 29.6, 14.0, 8.2, 88.3, 97.9, 97.1, and 74.5%, respectively.