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At least 235 records · Page 13Linked to original sources
PubMed1979

MMS mutagenesis in strains of Escherichia coli carrying the R46 mutagenic enhancing plasmid: phenotypic analysis of Arg+ revertants.

Arg+ revertants of E. coli AB1157 and derivative strains were selected after MMS mutagenesis and subjected to a phenotypic analysis which permitted the partitioning of revertants into 4 classes. The distribution of these revertant classes was influenced by mutations affecting DNA-repair systems, mutagen treatment and revertant-selection methods. Introduction of the R46 plasmid into strains also affected this mutational specificity, and it was concluded that the plasmid's mutagenic enhancing effect does not merely augment the cellular error-prone capacity to repair MMS damage to DNA.

Arginine↗
PubMed1994

Discrimination of epidemic and sporadic isolates of Acinetobacter baumannii by repetitive element PCR-mediated DNA fingerprinting.

In 1990, there was a significant increase in the number of lower respiratory tract infections and surgical wound infections in the adult intensive care units of our tertiary care teaching hospital caused by Acinetobacter baumannii compared with the number in 1989. During the 5-month period from April through August 1990, 84 isolates of A. baumannii were recovered from 50 hospitalized patients. Biotyping, comparison of antibiograms, plasmid analysis, and DNA polymorphisms of 20 isolates from 20 different patients, determined by the use of repetitive element PCR with primers aimed at repetitive extragenic palindromic sequences and enterobacterial repetitive intergenic consensus sequences, were used to investigate this apparent outbreak. Biotyping, antibiograms, plasmid analysis, and enterobacterial repetitive intergenic consensus PCR were not useful epidemiologically. Repetitive element PCR-mediated DNA fingerprinting using repetitive extragenic palindromic primers discriminated between epidemic and sporadic strains of A. baumannii and demonstrated four discrete clusters which were unique epidemiologically.

Acinetobacter↗
PubMed2004

Recognition of DNA by omega protein from the broad-host range Streptococcus pyogenes plasmid pSM19035: analysis of binding to operator DNA with one to four heptad repeats.

pSM19035-encoded omega protein forms a dimer (omega2) that binds to a set of 7-bp repeats with sequence 5'-NATCACN-3'. Upon binding to its cognate sites, omega2 regulates transcription of genes required for copy number control and stable inheritance of plasmids, and promotes accurate plasmid segregation. Protein omega2 binds poorly to one heptad but the affinity to DNA increases with two and more unspaced heptads in direct or inverted orientation. DNA titration of increasing numbers of heptads with omega2, monitored by circular dichroism measurements, indicates the binding of one omega2 to one heptad (omega2:heptad stoichiometry of 1:1). Spacing of two directly or inversely oriented heptads by 1 to 7 bp reduces the affinity of the protein for its cognate target site. The binding affinity of omega2 for two directly repeated heptads was severely reduced if one of the base pairs of the core 5'-ATCAC-3' sequence of one of the heptads was individually substituted by any other base pair. Hydroxyl radical footprinting shows a protection pattern at the 5'-ATCAC-3' core. These data suggest that each heptad defines an operator half-site and that tight binding of the symmetric omega2 to the central 5'-TCA-3' core of symmetric or asymmetric targets (differently oriented heptads) is probably achieved by structural changes of DNA and/or protein or both.

Bacterial Proteins↗
PubMed1984

Restriction site bank vectors. II. DNA sequence analysis of plasmid pJRD158.

pJRD158 is a small plasmid vector (3903 bp) derived from pBR327 and specifying resistance to ampicillin and tetracycline. It contains 28 unique restriction sites (and 4 nonunique restriction sites) that can be used for cloning. The DNA sequence and computer-assisted restriction site analysis of pJRD158 are reported. Evidence is also presented that suggests a 2-bp revision of the DNA sequence of pBR322 in the RNA primer region.

Ampicillin↗
PubMed1998

Analysis of plasmid DNA from a pharmaceutical perspective.

The advent of gene therapy and polynucleotide-based vaccines has resulted in the use of plasmid DNA as a drug substance. Although biologically (cell or animal) based assays must currently be employed to establish the identity and potency of such drugs, we argue that in the future, a combination of microchip-based mutation detection devices combined with an array of chromatographic, electrophoretic, hydrodynamic, and spectroscopic methods can be employed to rigorously establish these properties. We review a variety of such methods in this context and also consider the issue of the chemical stability of plasmids. Extensive comparison is made to protein-based pharmaceuticals with the unique importance of polynucleotide sequence emphasized in comparison to protein tertiary structure.

Chemistry Techniques, Analytical↗
PubMed1990

[Analysis of plasmid profile of antibiotic-resistant Enterobacteriaceae circulating in hospitals].

Certain pheno- and genotype properties of S. typhimurium and some other representatives of Enterobacteriaceae resistant to antimicrobial drugs were studied. The strains were isolated from children with salmonellosis within 4 months when an infection hospital was subjected to microbiological observation. It was shown that by their antibiotic resistance, phagovars and molecular weights of the plasmid DNas, the strains S. typhimurium were similar to those isolated during hospital infections. The conjugative plasmids responsible for antibiotic resistance in some strains did not differ in their molecular weights and antibiotic resistance markers. The strains S. typhimurium similar in their pheno- and genotype properties were isolated only from 2 patients which allowed one to consider it possible that the patients were infected by the strains of common genesis. Analysis of nonpathogenic representatives of Enterobacteriaceae isolated from the patients along with the S. typhimurium strains confirmed the fact that the patients were infected with the same pathogenic strain.

Anti-Bacterial Agents↗
PubMedDate not supplied

Epidemiologic typing of Enterobacter sakazakii in two neonatal nosocomial outbreaks.

Two unrelated hospital outbreaks of Enterobacter sakazakii, involving meningitis, bacteremia, and colonization of neonates, were investigated. In each of these outbreaks, E. sakazakii was isolated from both patients and dried infant formula. In previous outbreaks, the source and mode of transmission of E. sakazakii in neonatal infections was not determined. In this study, we used a combination of typing methods (plasmid analysis, antibiograms, chromosomal restriction endonuclease analysis, ribotyping, and multilocus enzyme electrophoresis) to evaluate the isolates from each outbreak as to their relatedness. The typing results differed among outbreaks, but in each one, patient and formula isolates shared the same typing pattern. The only exceptions were disk antibiograms, which often varied among colonies selected from each of the isolates. Plasmid analysis, chromosomal restriction endonuclease analysis, ribotyping, and multilocus enzyme electrophoresis all were effective as epidemiological typing methods for E. sakazakii, especially when used in combination. By using this typing scheme, we have confirmed that E. sakazakii from intrinsically contaminated dried infant formula was the source of neonatal infection.

Anti-Bacterial Agents↗
PubMed1982

Analysis of plasmid genome evolution based on nucleotide-sequence comparison of two related plasmids of Escherichia coli.

Plasmid Rsc13, a small derivative of the plasmid R1, contains a region necessary for replication as well as a complete copy (4957 bp) of the ampicillin resistance transposon, Tn3. We determined the nucleotide sequence of the replication region of Rsc13 to be 2937 bp and then compared this region (designated the 2.9-kb region) to the analogous region of pSM1, a small derivative of the plasmid R100 which has common ancestry with R1. Rsc13 and pSM1 were 96% homologous in this 2.9-kb region except for a discrete region of about 250 bp which showed only 44% homology. The sequence and distribution of nucleotide substitutions between Rsc13 and pSM1 supported a map of possible genes and sites which have previously been seen in the replication region of Rsc13 and pSM1 which showed only 44% homology. Analysis of the amino acid sequence and predicted conformation of the two RepA2 polypeptides, however, suggested that they were very similar. We proposed that the repA2 region of R1 and R100 was replaced by a substitution of a short DNA segment from another plasmid which was evolutionarily related to R1 and R100 but had more divergence. This event may have been mediated by a mechanism similar to that of gene conversion as described in eukaryotic systems.

Ampicillin↗
PubMed1988

Plasmid DNA analysis of Staphylococcus epidermidis isolated from blood and colonization cultures in very low birth weight neonates.

We prospectively studied the course of colonization and sepsis with Staphylococcus epidermidis among 29 very low birth weight neonates undergoing prolonged umbilical catheterization. S. epidermidis bacteremia occurred in 7 patients. In 6 bacteremia was preceded by positive colonization cultures. Isolates obtained from nares, base of umbilicus, umbilical catheter entry sites, catheter tips and blood were examined for plasmid DNA profiles. In 4 patients the plasmid profiles of the catheter entry site isolates were identical with those of the blood isolates. In the other 3 bacteremic patients plasmid profiles of the catheter entry site and blood isolates were different. No correlation was observed in the plasmid DNA patterns of isolates obtained from catheter tip cultures as compared to the corresponding blood cultures. The blood isolates from bacteremic patients had different plasmid profiles.

Catheterization↗
PubMed1996

Analysis of gram negative recolonization of the neuropathic bladder among patients with spinal cord injuries.

Over a 4 year period, 119 acute spinal cord injury (SCI) patients were enrolled in this study. The 101 males and 18 females had a mean age of 35.9 years (range 16-87). Sixty-two patients were tetraplegic and 57 were paraplegic. All patients had a urine specimen taken for culture, colony count and sensitivity once weekly while they were receiving intermittent catheterization. Of these, 22 patients (18.5%), none of whom had underlying genito-urinary (GU) pathology, developed recolonization by an organism of the same species and genus previously cultured. All 22 reached sterile-urine between colonizations after being treated with antibiotics for at least 7 days. The 16 males and six females had a mean age of 35.1 years (range 17-79). Sixteen were tetraplegic and six were paraplegic. Plasmid analysis (PA) was used to determine whether these recolonizations were from the same or from a different strain. In those instances where the bacteria harbored no plasmids or where the results of plasmid analysis were otherwise inconclusive, bacteria were also compared using restriction fragment length polymorphism (RFLP) analysis. Recolonization was caused primarily by E. coli and K. pneumoniae. While there was no significant difference between the two organisms with respect to the number of days when sterile urine occurred to the time when recolonization was observed, there were significant differences seen in both organisms with regard to the time lapse from one colonization to the next: the average number of days to recolonization with an identical organism was 10.3 days, whereas with a different strain it was 15.9 days (P < 0.04). When a different organism was cultured between the recolonizations, the mean recolonization interval was 17.9 days. When no intervening organism occurred, the interval was 9.5 days (P < 0.005). Both intervals measured the days from the first sterile urine after the first colonization to the next colonization. These data indicate the proclivity for two common Gram negative normal bowel inhabitants to recolonize the neuropathic bladder of spinal cord injured patients even after adequate treatment. PA and RFLP provide a means of discriminating between relapses by the same organism versus recurrences by a different organism of the same species and genus. Those with the same identity tend to recur sooner than those of different identities and may be suspected when relapse occurs within two weeks of cessation of 7 day course of antibiotics. While an intervening organism may delay the relapse (or recurrence), it does not prevent it and identical organisms can reappear even after adequate therapeutic regimens. Since none of the patients in this study had GU pathology, recolonization by an identical strain (relapse) does not necessarily warrant an extensive investigation for disease within the GU tract.

Adolescent↗
PubMed2000

Emerging antimicrobial resistance, plasmid profile and pulsed-field gel electrophoresis pattern of the endonuclease-digested genomic DNA of Neisseria gonorrhoeae.

Resistant gonococci are very prevalent in many countries, particularly in Asia. This study was conducted to determine the trend of resistance, the effect of decreasing the ciprofloxacin susceptibilities of gonococci on the prevalence of penicillinase-producing N. gonorrhoeae (PPNG), and to compare the epidemiology of strains with the previous studies. A total of 602 strains of gonococci were isolated from prostitutes in 1997-1999. Antimicrobial susceptibility was tested by NCCLS disk diffusion and agar dilution methods. For epidemiologic analysis, plasmid analysis and pulsed-field gel electrophoresis (PFGE) were performed. The proportion of PPNG remained high (79%), and the strains with decreased susceptibility to ciprofloxacin increased significantly from 67% in 1997 to 84% in 1999. Compared to our previous study, the PFGE patterns were similar, while the proportion of strain with the 3.2-MDa plasmid markedly decreased. In conclusion, a rapid increase in ciprofloxacin-nonsusceptible strains may suggest difficulties in the treatment of gonococcal infections in the near future with the drug. The recent decrease of PPNG with the 3.2-MDa plasmid may suggest that there is an epidemiological change in gonococcal infections, and the prevalence of related PFGE patterns suggests the dissemination of a few clones among the high risk populations.

DNA↗
PubMed1991

Characterisation of PPNG and non-PPNG Neisseria gonorrhoeae isolates from Singapore.

OBJECTIVE: To characterise Neisseria gonorrhoeae isolates from Singapore. DESIGN: Characterisation of Neisseria gonorrhoeae isolates by auxotyping, serological analysis and plasmid profile analysis. SPECIMENS: Sixty randomly collected isolates from 41 symptomatic, untreated males and 19 female prostitutes were studied. RESULTS: Auxotyping of 25 PPNG and 35 non-PPNG strains showed that the Pro-auxotype was prevalent among both PPNG (56%) and non-PPNG (42.5%) strains. Prototrophic strains comprised 28% of PPNG and 32.5% of non-PPNG strains respectively. Serovar analysis showed that with the exception of seven serogroup WI strains, the majority belonged to serogroup WII/III. Serovar Aedih was predominant among both serogroup WI PPNG (80%) and non-PPNG (100%) strains. Serogroup WII/III PPNG strains were represented by nine serovars with the predominant serovars being Bacjk (28%) and Bcgjk (16%). Eleven serovars were identified in the WII/III non-PPNG strains and the major serovars were Bajk (20%), Bacjk (17%), Back (11.4%) and Beghjk (11.4%). Analysis of the 25 PPNG strains showed that 16 of them carried the 4.4 MDa (Asian type) resistance plasmid and nine strains harboured the 4.4 MDa plasmid in conjunction with the 24.5 MDa transfer plasmid. The cryptic plasmid of 2.6 MDa was present in 27 of the 35 non-PPNG strains. Five of the non-PPNG strains harbouring the cryptic plasmid also contained the 24.5 MDa transfer plasmid. The plasmid combination of 2.6 + 7.8 + 24.5 MDa was detected in three non-PPNG strains. CONCLUSION: The combination of epidemiological methods used in this study indicated the heterogeneity of N gonorrhoeae strains in Singapore. A total of 16 different combinations of auxotype, plasmid profile and serovar were seen in the 25 PPNG strains compared with 24 such combinations in the 35 non-PPNG strains. Such sensitive differentiation would otherwise not be possible using either auxotype-serovar (A/S) or auxotype-plasmid analysis.

Female↗
PubMed1987

Genetic and physical analysis of plasmid genes expressing inducible resistance of tellurite in Escherichia coli.

A large (greater than 250 kb) conjugative plasmid, pMER610, specifying resistance to tellurium and mercury was isolated from an Alcaligenes strain and transferred by conjugation to Escherichia coli AB1157. The acquisition of pMER610 by AB1157 increased the resistance to both telurite and tellurate by 100-fold. Expression of tellurite resistance by pMER610 and the cloned Ter determinant was inducible by prior exposure to tellurite at levels sub-toxic to the sensitive AB1157. Physical analysis of the cloned Ter fragment located the resistance determinant to a 3.55 kb region. Insertion of Tn 1000 (gamma delta) into this region produced two classes of sensitive mutations, fully sensitive and intermediate or hyposensitive, which map in adjacent regions and form two complementation groups. Maxicell analysis identified four polypeptides (15.5, 22, 23 and 41 kDa) expressed by the Ter clone. The 23 kDa polypeptide may not be required for resistance since tellurium-sensitive gamma delta insertion mutations were not detected in the 23 kDa coding region.

Alcaligenes↗
PubMed1991

Evaluation of coagulase-negative staphylococci in blood cultures. A prospective clinical and microbiological study.

Coagulase-negative staphylococci (CNS) are the commonest microorganisms in blood cultures, and sorting out patients with CNS septicemia from sample contamination a persistent problem. We prospectively evaluated 73 patients with CNS-positive blood cultures during 1 year and analysed the corresponding 122 isolates in order to determine the rate of septicemia and define the role of microbiological markers of identity such as plasmid profile for that purpose. Three patients had true septicemia, all of them with implanted foreign devices. The plasmid analysis, being the most reliable identity marker, had its greatest implication in reducing the intermediate group of patients clinically suspected of septicemia from 12 to 4. Strict clinical criteria and serial blood cultures are most important in sorting out patients with CNS septicemia from cases of sample contamination. In high risk patients--critically ill with implanted foreign devices--plasmid analysis or other reliable markers of identity are of great additional value.

Adult↗
PubMed1999

Typing and characterization of mechanisms of resistance of Shigella spp. isolated from feces of children under 5 years of age from Ifakara, Tanzania.

Eighty-six strains of Shigella spp. were isolated during the dry season from stool samples of children under 5 years of age in Ifakara, Tanzania. The epidemiological relationship as well as the antimicrobial susceptibility and mechanisms of resistance to ampicillin, chloramphenicol, and co-trimoxazole were investigated. Four different epidemiological tools, pulsed-field gel electrophoresis (PFGE), repetitive extragenic palindromic (REP)-PCR, plasmid analysis, and antibiogram, were compared for typing Shigella strains. Seventy-eight (90%) strains were Shigella flexneri and were distributed into four groups, by either PFGE or REP-PCR, with 51, 17, 7, and 3 strains. The four strains of Shigella dysenteriae belonged to the same group, and the four strains of Shigella sonnei were distributed in two groups with three and one strain each. Plasmid analysis showed a high level of heterogeneity among strains belonging to the same PFGE group, while the antibiogram was less discriminative. REP-PCR provided an alternative, rapid, powerful genotyping method for Shigella spp. Overall, antimicrobial susceptibility testing showed a high level of resistance to ampicillin (81.8%), chloramphenicol (72.7%), tetracycline (96.9%), and co-trimoxazole (87.9%). Ampicillin resistance was related to an integron-borne OXA-1-type beta-lactamase in 85.1% of the cases and to a TEM-1-type beta-lactamase in the remaining 14.8%. Resistance to co-trimoxazole was due to the presence of a dhfr Ia gene in all groups except one of S. flexneri, where a dhfr VII gene was found within an integron. Chloramphenicol resistance was associated in every case with positive chloramphenicol acetyltransferase activity. All strains were susceptible to nalidixic acid, ciprofloxacin, ceftazidime, cefotaxime, and cefoxitin. Therefore, these antimicrobial agents may be good alternatives for the treatment of diarrhea caused by Shigella in Tanzania.

Bacterial Typing Techniques↗
PubMed1997

Shigella serogroups identified from adult diarrhoeal out-patients in Addis Ababa, Ethiopia: antibiotic resistance and plasmid profile analysis.

Fifty shigella strains were isolated from 700 diarrhoeal samples collected from adult diarrhoeal out-patients in Addis Ababa. Among the isolates, serogroup A comprised 28%, B 44%, C 18% and D 10%. Among all shigella serogroups, highest resistance was encountered to tetracycline (74%), ampicillin (70%), cephalothin (64%), trimethoprim-sulfamethoxazole (52%) and chloramphenicol (50%) while least resistance was observed to gentamicin (0%), polymyxin B (10%) and nalidixic acid (14%). Gentamicin, polymyxin B and nalidixic acid were found to be the drugs of choice for cases of shigellosis. All drug resistant isolates analysed for plasmids contained multiple plasmids ranging from 1.8 to greater than 21 Kilobases.

Adolescent↗