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PubMed2004

Molecular diversity of new Thermococcales isolates from a single area of hydrothermal deep-sea vents as revealed by randomly amplified polymorphic DNA fingerprinting and 16S rRNA gene sequence analysis.

Members of the Thermococcales are anaerobic Archaea belonging to the kingdom Euryarchaea that are studied in many laboratories as model organisms for hyperthermophiles. We describe here a molecular analysis of 86 new Thermococcales isolates collected from six different chimneys of a single hydrothermal field located in the 13 degrees N 104 degrees W segment of the East Pacific ridge at a depth of 2,330 m. These isolates were sorted by randomly amplified polymorphic DNA (RAPD) fingerprinting into nine groups, and nine unique RAPD profiles were obtained. One RAPD group corresponds to new isolates of Thermococcus hydrothermalis, whereas all other groups and isolates with unique profiles are different from the 22 reference strains included in this study. Analysis of 16S rRNA gene sequences of representatives of each RAPD group and unique profiles showed that one group corresponds to Pyrococcus strains, whereas all the other isolates are Thermococcus strains. We estimated that our collection may contain at least 11 new species. These putative species, isolated from a single area of hydrothermal deep-sea vents, are dispersed in the 16S rRNA tree among the reference strains previously isolated from diverse hot environments (terrestrial, shallow water, hydrothermal vents) located around the world, suggesting that there is a high degree of dispersal of Thermococcales: About one-half of our isolates contain extrachromosomal elements that could be used to search for novel replication proteins and to develop genetic tools for hyperthermophiles.

Base Sequence↗

PubMed1969

Frequency of R factor-mediated multiple drug resistance in Klebsiella and Aerobacter.

A comparative study was done on the transfer frequency of R factors from 90 strains of multiple drug-resistant Aerobacter and 81 strains of Klebsiella to Escherichia coli CSH-2 (F(-), met(-), pro(-), Nal-r). The most common resistance patterns for the Aerobacter isolants were ampicillin streptomycin chloramphenicol tetracycline and ampicillin streptomycin chloramphenicol tetracycline kanamycin neomycin; for the Klebsiella isolants, the most common resistance pattern was ampicillin kanamycin streptomycin tetracycline chloramphenicol neomycin. R factors were isolated from 14.1% of the Aerobacter strains; 61.5% of these R factors harbored R determinants for ampicillin streptomycin tetracycline. R factors were isolated from 79.1% of the Klebsiella strains; four R factors were isolated with significant frequency; streptomycin chloramphenicol kanamycin neomycin, 37.5%; ampicillin streptomycin tetracycline kanamycin neomycin, 14.1%; ampicillin streptomycin tetracycline, 12.5%; and streptomycin chloramphenicol tetracycline, 12.5%.Chloramphenicol, kanamycin, and neomycin resistance was rarely transferred from the Aerobacter strains, although over 50% of the clinical isolants possessed resistance to these antibiotics. In contrast, over 75% of the Klebsiella strains transferred resistance to chloramphenicol, kanamycin, neomycin. Highest frequency of transferred resistance to individual drugs in the Aerobacter strains was to streptomycin (14.8%), whereas in the Klebsiella group resistance to four drugs was transferred at a very high frequency: streptomycin (80.8%), chloramphenicol (78.5%), kanamycin (76.4%), and neomycin (75.9%).

Ampicillin↗

PubMed1969

Effect of beta-lactamase location in Escherichia coli on penicillin synergy.

Resistance to ampicillin in Escherichia coli is due generally to the presence of a beta-lactamase (penicillinase). Resistant strains have been found to fall into two groups: those with high-level resistance (1,000 mug/ml or greater) and those with low-level resistance (8 to 250 mug/ml). Most of the high-level resistant organisms posses beta-lactamases whose synthesis is episomally mediated. These strains release penicillinase from the cell when they are subjected to osmotic shock. Low-level resistant strains do not release the enzyme with osmotic shock. High-level resistant strains are not susceptible to the synergistic action of a penicillinase-resistant penicillin with ampicillin. Seventy eight per cent of low-level resistant strains are susceptible to the synergistic action of ampicillin and oxacillin. The two types of beta-lactamases are similar in regard to most properties; both enzymes are subject to competitive inhibition by penicillinase-resistant penicillins. The difference in location in the cell might explain why only some strains of E. coli are susceptible to the synergistic action of penicillin combinations.

Ampicillin↗

PubMed1969

Transferable drug resistance among Enterobacteriaceae isolated from cases of neonatal diarrhea in calves and piglets.

Fecal specimens were collected on 22 different Nebraska ranches and at the Department of Veterinary Science from young calves and pigs with neonatal diarrhea. Enterobacteriaceae isolated from these fecal specimens were screened for resistance to tetracycline, streptomycin, sulfamethizole, kanamycin, chloramphenicol, colistin, nitrofurantoin, and nalidixic acid. Of the 92 strains studied, 57 were resistant to one or more of these antimicrobial agents. Resistant strains were obtained from all herds involved in the study. The two most common resistance patterns were tetracycline streptomycin sulfamethizole (22 of 57) and tetracycline (13 of 57). None of the strains were resistant to chloramphenicol, colistin, nitrofurantoin, or nalidixic acid. The 57 resistant strains were studied to determine whether the resistance was transferable. Forty-three of the 57 resistant strains could transfer part or all of their resistance pattern to a drug-sensitive recipient. The 43 R(+) strains were obtained from 17 of the 23 herds studied. Considerable variation was observed between different R(+) strains in the frequency of transfer of resistance to a particular drug. In addition, variation in the frequency of transfer of different resistance determinants in individual R(+) strains was noted.

Animals↗

PubMed1974

Survival of R+ Escherichia coli in sea water.

The survival of Escherichia coli strains in sea water appears not to be affected by the possession of an R(+) factor. Sea water induces no detectable curing of R(+)E. coli.

Anti-Bacterial Agents↗

PubMed1974

Simultaneous loss of proteinase- and lactose-utilizing enzyme activities in Streptococcus lactis and reversal of loss by transduction.

During studies on spontaneous loss of lactose metabolism in Streptococcus lactis C2, it was found that the lactose-negative (lac(-)) mutants were also proteinase negative (prt(-)). This pleiotropic effect was observed in S. diacetilactis 18-16, but not in S. cremoris B1. The lac(-)prt(-) mutants from S. lactis C2 were able to grow in milk, but no pH change or measurable protein breakdown occurred. When the milk was supplemented with glucose, a slow decline in pH occurred. Addition of a protein hydrolysate to milk did not stimulate acid production. When both supplements were added to milk, normal growth and pH change were obtained. When the lac(-)prt(-) mutant of S. lactis C2 was transduced with the temperate phage from the lac(+)prt(+) parent culture, approximately equal numbers of lac(+)prt(-) and lac(+)prt(+) transductants were obtained. When the spontaneous lac(+)prt(-) strain of S. lactis C2 was converted to a lac(-)prt(-) derivative and transduced, similar results were obtained. The co-transduction of the lactose and proteinase markers suggest they are closely associated. The findings indicate that the transducing phage from S. lactis C2 can be used to examine the causes of instability in both the lactose and proteinase enzyme systems of this organism.

Animals↗

PubMed1975

Plasmid distribution and evidence for a proteinase plasmid in Streptococcus lactis C2-1.

Five plasmids, distinguishable by their molecular weights (10(6), 2 x 10(6), 5 x 10(6), 10(7), 3 x 10(7), respectively) were isolated from Streptococcus lactis C2. A spontaneous proteinase-negative derivative of this strain lacked the 10(7) plasmid.

Centrifugation, Density Gradient↗

PubMed1968