Search citation statements
Paper Sections
Citation Types
Year Published
Publication Types
Relationship
Authors
Journals
Many strains with transferable colicinopenic factors were found to mobilize non-transferable but extrachromosomally located streptomycin resistance determinants in laboratory strains. I n turn, with only one exception, all strains which were found in triparental crosses to mobilize the transfer of the S-determinants harboured a transferable col factor. These findings may show the ecological importance of transferable colicinogenic strains which occur frequently among wild type strains of E. coli in the origin and spreading of resistance transfer factors under natural conditions. When studying transfer factors and transferable resistance, it is nesseesary t o check the donor strains for colicinogeny and t o destroy the colicines produced. Otherwise false negative results may be obtained.During the investigation of the so-called transfer factors (ANDERSON 1968) in antibiotic-susceptible wild type strains of Escherichi coli, it was found in this laboratory that, with only one exception, the susceptible transfer factor bearing (tj") strains of E . coli are colicinogenic and harbour a transferable col factor.Occurrence of the transfer factor property in some colicinogenic strains i. e. that function of a sex factor which provides transfer of non-transmissible but extrachromosomal resistance to antibiotics was also observed by LEWIS (1968). The principles of this mobilization were reviewed by MEYNELL et al. (1968).I n turn, we also observed that the strain E . coli K-260, bearing three colicinogenic factors, and some other strains with transferable colicinogenic factors (further designed as tf+col+) e . g. 63 R-82 and 62 G-1 were able to mobilize extrachromosomal but non-transferable streptomycin resistance (further designated as tj-S,,). It therefore seemed interesting to investigate, on a larger scale, the ability of the tf+col+ factors to mobilize and mediate the transfer of S-determinants which ot'herwise are not transferred to various recipient strains although localized extrachromosomally (LEWIS 1969. Therefore, 15 tf+col+ strains and 8 tf-col' strains i. e . strains with non-transmissible col factors were tested. Throughout this study, trypsine was used t o inactivate the colicines produced.
Many strains with transferable colicinopenic factors were found to mobilize non-transferable but extrachromosomally located streptomycin resistance determinants in laboratory strains. I n turn, with only one exception, all strains which were found in triparental crosses to mobilize the transfer of the S-determinants harboured a transferable col factor. These findings may show the ecological importance of transferable colicinogenic strains which occur frequently among wild type strains of E. coli in the origin and spreading of resistance transfer factors under natural conditions. When studying transfer factors and transferable resistance, it is nesseesary t o check the donor strains for colicinogeny and t o destroy the colicines produced. Otherwise false negative results may be obtained.During the investigation of the so-called transfer factors (ANDERSON 1968) in antibiotic-susceptible wild type strains of Escherichi coli, it was found in this laboratory that, with only one exception, the susceptible transfer factor bearing (tj") strains of E . coli are colicinogenic and harbour a transferable col factor.Occurrence of the transfer factor property in some colicinogenic strains i. e. that function of a sex factor which provides transfer of non-transmissible but extrachromosomal resistance to antibiotics was also observed by LEWIS (1968). The principles of this mobilization were reviewed by MEYNELL et al. (1968).I n turn, we also observed that the strain E . coli K-260, bearing three colicinogenic factors, and some other strains with transferable colicinogenic factors (further designed as tf+col+) e . g. 63 R-82 and 62 G-1 were able to mobilize extrachromosomal but non-transferable streptomycin resistance (further designated as tj-S,,). It therefore seemed interesting to investigate, on a larger scale, the ability of the tf+col+ factors to mobilize and mediate the transfer of S-determinants which ot'herwise are not transferred to various recipient strains although localized extrachromosomally (LEWIS 1969. Therefore, 15 tf+col+ strains and 8 tf-col' strains i. e . strains with non-transmissible col factors were tested. Throughout this study, trypsine was used t o inactivate the colicines produced.
During obligatory bacteriological examinations of persons occupied in food industry or distribution, we isolated from the stool specimens of 3 persons of a meat factory strains of Salmonella anatum resistant to antibiotics.Two atrains, S. anatum 5915 and 8. anatum 6100, respectively, were found to be resistant to tetracyclines (T) only, while the third strain showed an unusual type of resistance to colistine (colimycin).Our Antibiotic Reference Laboratory has just started a thorough examination of resistant Salmonella strains in Czechoslovakia for the presence of R-factors.Both T-resistent strains were therefore tested, in mixed cultures, with Escherichia coli K 12 185 resistant to nalidixic acid (Nx), for t&e transfer of their T-monoresistance. The procedure we are using for the detection of R-factors and for following up their further transfers, was already described (KRCMERY and J A N O U~K O V~ 1969, FRI~DERICQ et al. 1971). Briefly, 2 ml of 6 hrs. shaken cultures of the donor strains in nutrient broth (DIFCO) were mixed with equal volumes of 6 hrs. broth cultures of E. coli K 12 185 Nx, which is susceptible to T, but has a chromosomally located high-level resistance to Nx. The strains of S. anatum tested were all highly sensitive to Nx as seen in control plating on MACCONKEY Agar (DIFCO) containing 0.5 to 10.0 pglml of Nx. After overnight incubation, the mixture was diluted to lo-' in saline, and 0.01 ml of each dilution was plated on a segment of MACCONKEY Agar containing 20 pg/ml of T and the same amount of Nx. The plates were incubated 20 hrs. a t 37 "C.The growth with a considerable frequency on MACCONKEY Agar with T and Nx of E. coli K 12 185 Nx after the mixed incubation with 8. anaturn strain 5915suggests the transferable nature of the T-determinant in that Salmonella strain.The T-determinant of S.anatum 6100 was not transferable in the experimental system used, which, however, does not exclude its transferability t o another recipient strain. The frequencies of transfer are given as the fraction of resistant colonies of the recipient strain out of the total number of recipient cells, which was about 2.8 x lo8 cells/ml. I n the above instance, about los cells/ml of the recipient strain, present in the mixture with S. anatum 5915, received the Tdeterminant. The level of acquired T-resistance in the colonies of strain E. coli K 12 185 Nx on MACCONKEY Agar was between 50 and 75 pg/ml of T.The transferability of this T-determinant was reconfirmed by its further transfer from E. coli K 12 185 Nx T to S. typhimurium SH, susceptible to T
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.