Transferable Drug Resistance Research Articles

Conjugative R plasmids in Streptococcus agalactiae (group B)

Twenty-one drug-resistant clinical isolates of group B streptococci were investigated for drug-resistance transfer by conjugation. Six strains were resistant to tetracycline, two to chloramphenicol, one to both drugs, and twelve to macrolide antibiotics (erythromycin, oleandomycin and spiramycin), lincomycin, pristinamycin I, and/or chloramphenicol and tetracycline. Ten strains carried R plasmids which were transferable to group B and/or group D recipients by a conjugation-like phenomenon. Six plasmids were transferred at a high frequency (9 × 10 −2 to 4 × 10 −4) and four, at low frequency (5 × 10 −6 to 7 × 10 −8). The molecular weight of one plasmid (pIP501) was investigated after transfer into the new hosts and was found to be similar to that carried by the wild strain (19.8 × 10 6).

Transferable drug resistance in bacteria of coastal canal water and sediment

This study was undertaken to determine the comparative incidence of drug-resistant coliforms and salmonellae in the water and bottom sediments of six coastal canal communities which are used heavily for recreational activities. Of a total of 423 coliforms, 300 fecal coliforms and 100 salmonella isolates examined, 74.9% coliforms, 61.3% fecal coliforms and 71.0% salmonellae were resistant to one or more of the 12 antibiotics tested. Multiple resistance occurred in 48.9% coliforms, 32.7% fecal coliforms and 68.0% salmonella strains. A total of 178 coliforms, 137 fecal coliforms and 51 salmonella isolates were tested for the presence of resistance transfer factors, and 53.9%, 53.3% and 56.9% isolates, respectively, were capable of transferring their resistance patterns to Escherichia coli and/or Salmonella choleraesuis recipient strains. A significantly higher number of drug-resistant bacteria carrying R-factors (R +) was found to occur in sediment than in surface water.

Les additifs en nutrition animale. Effets sur l'homme, les animaux et l'environment

Animal feed additives have been used for many years. They have played a part in meeting the increasing demand for animal products due to industrialization and urbanization while the useful agricultural areas and the number of agricultural workers were decreasing. The biological and economic advantages of feed additives are well known. They allow the sanitary drawbacks of great overcrowding of animals to be palliated. Those advantages exist in spite of improvements in the quality of the diet and in the environment. They have been diminishing but remain real. They save feed, protein, time and worry for the farmer. However, several objections have been raised against the use of feed additives. They are more theoretical than actual. The problem of residues is discussed. It appears without foundation when the watchfulness of the national and international organizations controlling the use of feed additives is taken into consideration. The problem of transferable drug resistance through the plasmids, especially in Enterobacteria, is more relevant to microbial ecology than to the utilization of antibiotics or even of copper salts. All things considered, the balance is in favour of the use of feed additives.

Anaerobes and transferable drug resistance

Anaerobes and transferable drug resistance

Some Characteristics of Pathogenic E. Coli Strains

SUMMARY Escherichia coli strains isolated from pericardial lesions or blood of diseased chickens (317 strains) and turkeys (181 strains) and from cloacae of apparently normal chickens (88 strains) from healthy flocks were examined serologically. Among 498 strains isolated from clinical material, 61.9% were found to belong to one or another of the three serological groups, 078:K80 (which comprised 35.6% of isolates from chickens and 25.9% from turkeys), 01:K1 and 02:K1. Only 25% of isolates from healthy chickens could be placed into any of the above PK groups. Most (92%) of the strains isolated from clinical material caused septicemia and death by oral inoculation in one-day-old chicks. All the strains were non-haemolytic; a higher proportion of strains isolated from clinical material than those from healthy chicks produced colicines; the proportion of lysogenic strains was similar in both groups of isolates. Most of the strains (99.2%) isolated from diseased birds and 75% of those from healthy chickens were found to be resistant to one or more of the anti-bacterial drugs tested. Twenty-four patterns of resistance were noted, of which multiple resistance to sulphonamide, streptomycin, oxytetracycline, chloramphenicol was the most common. The percentage of isolates from clinical material found to be resistant to sulphonamide (300 μg), oxytetracycline (50 μg), streptomycin (25 μg), chloramphenicol (50 μg), furazolidone (15 μg), ampicillin (25 μg) and neomycin (30 μg) was 90.6, 90.6, 64.8, 54.4, 45.4, 17.6 and 15.5 respectively. The corresponding figures for resistant strains from healthy chickens were 65.9, 19.3, 42.1, 2.3, 10.2, 4.5 and 0 respectively. None of the strains from healthy chickens and only four isolates from diseased birds showed resistance to nalidixic acid. The incidence of transferable drug resistance was higher among strains from clinical material than those from healthy birds. More than half of the resistant strains of the former isolates possessed the transfer factor and were able to transfer their resistance to a recipient strain in vitro .

Spontaneous, ultraviolet and ionizing radiation mutagenesis in two auxotrophic strains of Salmonella typhimurium carrying an R plasmid

Ultraviolet-induced, gamma-induced and spontaneous mutation yields were studied in two different auxotrophic strains of Salmonella typhimurium in the presence and absence of the UV-protecting drug resistance transfer factor R-Utrecht. One strain, carrying the hisC557 (amber) mutation, showed significantly increased spontaneous, UV- and γ-induced mutability in the presence of the R-Utrecht plasmid. The other strain, carrying the trpD1 mutation (thought to be a missense mutation), also showed significantly increased UV mutability in the presence of the R factor, but appeared to show no significant increase in spontaneous mutability and only a very slight increase in γ-mutability when carrying the R factor. These results demonstrate that the R-Utrecht plasmid, known to enhance UV-induced mutation yields in S. typhimurium, can also significantly enhance both spontaneous and γ-induced mutation yields in this species. The latter effects are not so discernible with all markers, however, as shown by the results with strains carrying the tpD1 mutation. Enhancement of spontaneous mutability thus appears to be correlated with enhancement of γ-mutability rather than UV mutability.

Drug resistance in group D streptococci of clinical and nonclinical origin: prevalence, transferability, and plasmid properties.

Group D streptococci isolated from clinical specimens and from sewage were investigated with regard to resistance to tetracycline (Tc), erythromycin (Em), and chloramphenicol (Cm). The median values of the percentages of resistant strains from sewage were: for Tc, 14%; for Em, 2.8%; and for Cm, 0.1%. For the recent isolates of clinical origin, resistance percentages found were 58% for Tc, 12% for Em, and 14% for Cm, and, in comparison to clinical isolates from 1964, the incidence of drug resistance slightly increased. In strains of both sources, the drug resistance was often found to be transferable to another group D streptococcus, probably by conjugation. Two strains were able to transfer their Em resistance to a streptococcus strain of group B. No transfer of drug resistance to a group A streptococcus and Escherichia coli was observed. All beta-hemolytic streptococci were also bacteriocinogenic, and frequently these properties were found to be transferable. The function, size, and base composition of the plasmids of two drug-resistant Streptococcus faecalis strains were investigated; strain M439 harbors at least two conjugative plasmids: pRI401, molecular weight 30 x 10(6), coding for Tc resistance, and pRI402, molecular weight 41 x 10(6), coding for Em resistance. Strain M403 carries one single conjugative plasmid species, coding for Tc resistance. The molecular weight of this plasmid, pRI404, was 37 x 10(6). The guanine plus cytosine content of these plasmids was 35 to 36%.

Sequential Hospitalwide Outbreaks of Resistant Serratia and Klebsiella Infections

Late in 1973 at the Nashville Veterans Administration Hospital, an intrusion of Serratia marcescens infections that were resistant to gentamicin sulfate and other antimicrobial agents occurred. This abated somewhat, only to be superseded by another wave of multiply-resistant infections due to Klebsiella pneumoniae beginning in the spring of 1974. Approximately 400 patients had substantial infections with these organisms during the 2 1/4 year period, imposing considerable morbidity and mortality. Due to the serious and lasting impact that these events imposed on patient care in our hospital, we sought explanations for the sequential infectious outbreaks. Both may have arisen because of the same persisting pressures favoring prevalence of multidrug-resistant bacteria. Indirect evidence including the sequential order of the outbreaks, similarity of antibiotograms, transferable multiple drug resistance from Serratia to Klebsiella, and possession of approximately equal molecular weight plasmids supported the notion that the two outbreaks were causally related.

Further observations on the genetic transfer of drug resistance in Eimeria maxima

Experiments are described which support the view that, in Eimeria maxima, drug resistance factors are transferred at zygote formation. The phenomenon occurred between infections which were initiated by the inoculation of merozoites. It also took place between variants of the same, but not between different species. Transference of drug resistance wsa not affected by the treatment of the chicks with acriflavine.

Transferable drug resistance in the gonococcus

Transferable drug resistance in the gonococcus

Ubiquity of R Factor-Mediated Antibiotic Resistance in the Healthy Population

An attempt was made to assess the occurrence of R factor-mediated antibiotic resistance in the healthy population. Samples of aerobic, gram-negative intestinal bacteria from men from various parts of the country at military conscription were analysed for transferable drug resistance. The obtained frequency, about 15% of R factor carriers in the studied group, was interpreted to reflect the existence of a reservoir of R factors, from which resistant, pathogenic bacteria could be selected under antibiotic therapy. Resistance to tetracycline, streptomycin and sulfonamides dominated among the identified R factor-borne resistance traits.

R factor-mediated polarized chromosomal transfer in Escherichia coli C.

Five transferable drug resistance factors (R factors) with the ability to bring about chromosomal transfer in Escherichia coli C were investigated with respect to the direction and origin of chromosome transfer. They were found to constitute two groups, both with a clockwise direction of transfer. One group has its origin of transfer between arg and pro, and the other group has its origin of transfer between try and man on the E. coli C chromosome. With one R factor in particular, the rapid increase in the production of recombinants was followed by a decrease in numbers as mating was prolonged.

Extrachromosomal deoxyribonucleic acid in R factor-harboring Enterobacteriaceae.

Extrachromosomal deoxyribonucleic acid (DNA) from 24 different R factor-harboring Enterobacteriaceae was isolated and characterized by analytical ultracentrifugation and electron microscopy. The R factors represented 15 different patterns of transferable drug resistance found in enterobacteria from an enclosed geographic area. All of the strains contained extrachromosomal, circular DNA molecules within the range of 0.4 to 52 mum. More than one size class of circular DNA molecules was observed in the majority of the extrachromosomal DNA preparations. The buoyant density of the extrachromosomal DNA ranged from 1.700 to 1.720 g/cm3. The majority of the bacteria contained extrachromosomal DNAs of various densities. Three-fourths of the R factors were classified as fi+. The investigation illustrates the extensive variability in the physical characteristics of plasmid DNA from R factor-harboring strains.

Problems in evaluating nitrofurantoin susceptibility tests for Klebsiella-Enterobacter.

Tube dilution susceptibility tests in Trypticase soy broth showed that resistance to gentamicin (minimum bactericidal concentration >==12.5 mug/ml) among hospital isolates of Pseudomonas aeruginosa increased from 13.9% in 1969 to 38.9% in 1972. Transfer of drug resistance to six aminoglycosides from one wild Pseudomonas strain to another was accomplished in recombination experiments. A carbenicillin-resistant, beta-lactamase-producing strain served as the recipient. The exconjugant was resistant not only to aminoglycosides, including amikacin, but also to all clinically employed antimicrobials. Aminoglycoside resistance in the exconjugant was cured by sodium dodecyl sulfate. This transferable aminoglycoside resistance was not mediated by adenylylation or, as judged by bioassay, by other antibiotic-inactivating or -modifying processes.

Transmissible drug resistance of Escherichia coli and Salmonella from humans, animals, and their rural environments.

Isolates of Escherichia coli and Salmonella species obtained from humans, animals, and their rural environments were tested for their ability to transfer multiple drug resistance to competent recipients. In all, 125 (52.9%) of 242 isolates of E.coli transferred all or part of their resistance to E.coli CSH-2, and 103 (44.4%) of 232 isolates of E.coli transferred all or part of their resistance to Salmonella choleraesuis var. kuzendorf 214. The data suggest that the multiple drug resistance of E.coli transferred all or part of their resistance to Salmonella choleraesuis var kuzendorf 214. The data suggest that the multiple drug resistance of E. coli in the gut of humans who work with livestock may be due to the transfer of resistance determinants from animal strains to the resident flora of the human gut. Such transfer could occur during transient passage through the digestive tract. Multiple drug-resistant Salmonella were isolated from all sources. In all, 48 (80%) of 60 isolates of Salmonella transferred all or part of their resistance to E. coli CSH-2, and isolates of Salmonella transferred all or part of their resistance to E.coli CSH-2, and 42 (82.4%) of 51 isolates of Salmonella transferred all or part of their resistance to S. choleraesuis var, kuzendorf 214. Fifty-three (46.9%) of 113 antibiotic-sensitive isolates of E.coli possessed resistance transfer factor, and six (23.1%) of 26 isolates with resistance transfer factor mobilized resistance determinants in isolates unable to transfer drug resistance during conjugation experiments.

Transfer of drug resistance to myxococcus from bacteria carrying drug-resistance factors.

Resistance to chloramphenicol was successfully transferred from strains of Escherichia coli carrying R factors representative of compatibility groups F, W, S and N to strains of Myxococcus xanthus and M. fulvus. Resistance to kanamycin was transferred from an R factor in group S, and to neomycin from an R factor of group P. Myxobacterial strains differed in their capacity to take up the resistances and also in the stability of the resistance character. strains of M. fulvus were obtained that acquired resistance to chloramphenicol without exposure to R plus eubacterial strains. Cell-free preparations of all the chloramphenicol-resistant strains catalysed the acetylation of the drug. Cholramphenicol resistance was successfully transferred from the presumed R plus strains of Myxococcus and also from the spontaneously occurring chloramphenicol-resistant M. fulvus to other Myxococcus strains. Moreover, recombinants resistant to both rifampicin and 5-fluorouracil were obtained, though infrequently, by mixing Myococcus strains resistant to rifampicin and chloramphenicol with other myxococci resistant to 5-fluorouracil, both when the chloramphenicol resistance was derived from S-a (group W) and when it was the endogenous M fulvus resistance. Thus it appears that S-a and a new chloramphenicol resistance factor from M. fulvus will mobilize a chromosomal genetic marker in Myxococcus.

British Food Journal Volume 77 Issue 3 1975

Natural selection—survival of the fittest—is as old as life itself. Applied genetics which is purposeful in contrast to natural selection also has a long history, particularly in agriculture; it has received impetus from the more exacting demands of the food industry for animal breeds with higher lean : fat and meat : bone ratios, for crops resistant to the teeming world of parasites. Capturing the exquisite scent, the colours and form beautiful of a rose is in effect applied genetics and it has even been applied to man. For example, Frederick the Great, Emperor of Prussia, to maintain a supply of very tall men for his guards—his Prussian Guards averaged seven feet in height—ordered them to marry very tall women to produce offspring carrying the genes of great height. In recent times, however, research and experiment in genetic control, more in the nature of active interference with genetic composition, has developed sufficiently to begin yielding results. It is self‐evident that in the field of micro‐organisms, active interference or manipulations will produce greater knowledge and understanding of the gene actions than in any other field or by any other techniques. The phenomenon of “transferred drug resistance”, the multi‐factorial resistance, of a chemical nature, transferred from one species of micro‐organisms to another, from animal to human pathogens, its role in mainly intestinal pathology and the serious hazards which have arisen from it; all this has led to an intensive study of plasmids and their mode of transmission. The work of the Agricultural Research Council's biologists (reported elsewhere in this issue) in relation to nitrogen‐fixing genes and transfer from one organism able to fix nitrogen to another not previously having this ability, illustrates the extreme importance of this new field. Disease susceptibility, the inhibition of invasiveness which can be acquired by relatively “silent” micro‐organisms, a better understanding of virulence and the possible “disarming” of organisms, particularly those of particular virulence to vulnerable groups. Perhaps this is looking for too much too soon, but Escherichia coli would seem to offer more scope for genetic experiments than most; it has serotypes of much variability and viability; and its life and labours in the human intestine have assumed considerable importance in recent years. The virulence of a few of its serotypes constitute an important field in food epidemiology. Their capacity to transfer plasmids—anent transfer of drug resistance— to strains of other organisms resident in the intestines, emphasizes the need for close study, with safeguards.

Repair by genetic recombination in bacteria: overview.

DNA molecules that have been damaged in both strands at the same level are not subject to repair by excision but instead can be repaired through recombination with homologous molecules. Examples of two-strand damage include postreplication gaps opposite pyrimidine dimers, two-strand breaks produced by X-rays, and chemically induced interstrand cross-links. In ultraviolet-irradiated bacteria, the newly synthesized DNA is of length equal to the interdimer spacing. With continued incubation, this low-molecular-weight DNA is joined into high-molecular-weight chains (postreplication repair), a process associated with sister exchanges in bacteria. Recombination is initiated by pyrimidine dimers opposite postreplication gaps and by interstrand cross-links that have been cut by excision enzymes. The free ends at the resulting gaps presumably initiate the exchanges. Postreplication repair in Escherichia coli occurs in recB- AND RECC but is greatly slowed in recF- mutants. RecB and recC are the structural genes for exonuclease V, which digests two-stranded DNA by releasing oligonucleotides first from one strand and then from the other. The postreplication sister exchanges in ultra-violet-irradiated bacteria result in the distribution of pyrimidine dimers between parental and daughter strands, indicating that long exchanges involving both strands of each duplex occur. The R1 restriction endonuclease from E. COli has been used to cut the DNA of a bacterial drug-resistance transfer factor with one nuclease-sensitive site, and also DNA from the frog Xenopus enriched for ribosomal 18S and 28S genes. The fragments were annealed with the cut plasmid DNA and ligated, producing a new larger plasmid carrying the eukaryotic rDNA and able to infect and replicate in E. coli.

Detection of R Factors in Naturally Occurring Vibrio anguillarum Strains

R factors were detected in Vibrio anguillarum strains from vibrio-diseased freshwater fish, ayu (Plecoglossus altivelis), in Japan. It was found that 65 out of the 68 random isolates from epidemics of vibrio disease in 1973 carried transferable drug resistance factors. The most common type determined resistance to sulfonamides, streptomycin, chloramphenicol, and tetracycline and belong to the fi(-) type. The high incidence of R factors in Vibrio anguillarum from cultured fish is assumed to be due to selective pressure exerted by chemotherapeutic agents used in fish culturing.

Chemotherapy of rodent malaria: Transfer of resistance vs mutation

Pyrimethamine-resistant strains of Plasmodium berghei and P. vinckei were produced by exposing populations of erythrocytic parasites to the selection pressure of increasing doses of drug as well as by single-step mutations. Pyrimethamine-sensitive parasites of both rodent plasmodia were found to mutate at a rate of 1–2 × 10 −11 when exposed to a single course of drug therapy, consisting of 15 mg/kg/day for 4 consecutive days, given subcutaneously. Resistance obtained by either method, was found to be stabile for at least 40 passages in the absence of drug pressure, the longest number of passages tested. Parasites exposed to 15 mg/ kg/day were also found to be resistant to 160 mg/kg/day, the maximum dose of pyrimethamine tolerated by the rodent host. Plasmodium berghei chloroquine-sensitive parasites were found to have a mutation rate of 1.5 × 10 −10, when exposed to a single course of chloroquine therapy, consisting of 30 mg/kg/day chloroquine base given for 4 consecutive days, subcutaneously. These parasites were also found to be resistant to 60 mg/kg/day the highest dose of chloroquine tolerated by the rodent host. Chloroquine-resistant strains of P. vinckei could not be developed by a single-step mutation nor by selection by slow increases in drug pressure. Pyrimethamine-resistant strains of P. berghei, whether, the resistance was developed by single-step mutation, or by slowly increasing the pyrimethamine doses over extended periods of time, demonstrated dihydrofolate reductases which were similar in activity, Michaelis constants, and inability to be stimulated by increased concentrations of KCl. The same was found to be true for the dihydrofolate reductases (EC 1.5.1.3) isolated from pyrimethamine-resistant P. vinckei strains. The enzymes isolated from the resistant strains differed in all respects from their sensitive counterparts. Attempts at drug resistance-transfer, using both a biological filter system, and a dual drug resistant system, were both unsuccessful. The origin of all drug resistant strains studied and reported in this paper, can best be explained by the occurrence of mutation, most probably involving the change of a single nucleotide base in the DNA.