Marilyn Roberts | University of Washington (original) (raw)
Papers by Marilyn Roberts
Applied and Environmental Microbiology, 1996
An erythromycin-resistant (Em r) Listeria innocua and an Em r Listeria monocytogenes isolate both... more An erythromycin-resistant (Em r) Listeria innocua and an Em r Listeria monocytogenes isolate both carried ermC genes, which code for rRNA methylases. The ermC genes were transferable by conjugation to recipient L. monocytogenes, Listeria ivanovii, and Enterococcus faecalis but did not appear to be associated with conjugative plasmids. Listeria species are widespread in the environment and the intestines of humans and animals and can also be found in food (1, 4, 6, 11). Until recently, the genus was thought to be uniformly susceptible to antibiotics active against gram-positive bacteria. Penicillin is normally the drug of choice for treatment, but both erythromycin and tetracycline are alternatives for patients who are allergic to penicillin (8). Now both singly and multiply antibiotic-resistant listerias have been described (3, 4, 6, 7, 9, 11, 13). We (7) as well as others (4, 9, 11) have found tetracycline resistance due to the Tet M determinant in Listeria innocua, Listeria monocytogenes, and, more recently, Listeria welshimeri from food, the environment, and human disease. The Tet K and L determinants have been found in a few L. innocua isolates from food (7), while the Tet S determinant has been found in L. monocytogenes, L. innocua, and L. welshimeri (3, 4). Multiantibiotic resistance plasmids encoding chloramphenicol (cat221/cat223), macrolide/lincosamide/ streptogramin (MLS) (ermB), and tetracycline resistance (tetM) or chloramphenicol, MLS, streptomycin, and tetracycline resistance have been found in L. monocytogenes from both France and Switzerland (9). Recently, trimethoprim and streptomycin resistance has also been found in the genus (4). One streptomycin-resistant L. innocua strain carried a streptomycin nucleotidyltransferase related to the aad6 gene (4). These reports illustrate that more listerias are becoming antibiotic resistant by the acquisition of known gram-positive antibiotic resistance genes. We have been examining antibiotic resistance genes in listerias isolated from food (6, 7). Previously, we found that 11 of 12 L. innocua isolates from chicken or turkey frankfurters and mozzarella cheese were resistant to tetracycline and carried the tetM gene (6, 7). In the same studies, we identified one L. innocua and one L. monocytogenes strain which were resistant to erythromycin (MIC, Ͼ256 g/ml). Neither was tetracycline resistant. The L. monocytogenes isolate carried two small plasmids of roughly 3 and 7 kb. In this study on erythromycin determinants, Southern blots of purified total cell DNA (7, 10) were hybridized under stringent conditions with each of the following intragenic Erm probes: Erm A, pEM9592, 0.7-kb SspI; Erm B, pJIR229, 0.8-kb PstI-EcoRI; Erm C, pBR328: 33RV, 0.9-kb HpaI (15-17). We found that both isolates hy
Applied and Environmental Microbiology, 1993
Eleven of 12 tetracycline-resistant Listeria innocua strains, isolated from chicken or turkey fra... more Eleven of 12 tetracycline-resistant Listeria innocua strains, isolated from chicken or turkey frankfurters and mozzarella cheese, were shown to carry DNA sequences which hybridized with the Tet M probe; of these, two strains also hybridized with Tet K. The remaining strain hybridized with the Tet K probe only. The Tet M determinant appeared to be located on the chromosome; in one case, it was transferable by conjugation to recipients Listeria monocytogenes, Listeria ivanovii, and Enterococcus faecalis.
Frontiers in Microbiology, Feb 5, 2015
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Antimicrobial Agents and Chemotherapy, 1991
Tetracycline-resistant Tet M-negative isolates of Actinomyces viscosus, Eubacterium lentum, Mobil... more Tetracycline-resistant Tet M-negative isolates of Actinomyces viscosus, Eubacterium lentum, Mobiluncus curtisii, and Mobiluncus mulieris were screened with the Tet K, Tet L, and Tet O DNA probes. Ten (71%) of the resistant Mobiluncus strains hybridized with the Tet O probe, two of the three E. lentum strains hybridized with the Tet K probe, and the A. viscosus isolate hybridized with the Tet L probe.
Critical Reviews in Oral Biology & Medicine, 1998
In the last 20 years, changes in world technology have occurred which have allowed for the rapid ... more In the last 20 years, changes in world technology have occurred which have allowed for the rapid transport of people, food, and goods. Unfortunately, antibiotic residues and antibiotic-resistant bacteria have been transported as well. Over the past 20 years, the rise in antibiotic-resistant gene carriage in virtually every species of bacteria, not just oral/respiratory bacteria, has been documented. In this review, the main mechanisms of resistance to the important antibiotics used for treatment of disease caused by oral/respiratory bacteria-including β-lactams, tetracycline, and metronidazole-are discussed in detail. Mechanisms of resistance for macrolides, lincosamides, streptogramins, trimethoprim, sulfonamides, aminoglycosides, and chloramphenicol are also discussed, along with the possible role that mercury resistance may play in the bacterial ecology.
Journal of Bacteriology, Apr 1, 1978
An indigenous Neisseria gonorrhoeae conjugative plasmid, pLE2450, was tested for its ability to m... more An indigenous Neisseria gonorrhoeae conjugative plasmid, pLE2450, was tested for its ability to mediate chromosomal gene transfer between gonococcal strains. Plasmid-mediated chromosomal transfer was detected at a low frequency and can be used to establish certain linkage relationships between amino acid and antibiotic resistance markers.
Journal of General Microbiology, 1979
Of 261 strains of Neisseria gonorrhoeae examined for plasmids, 6 were plasmid-free, 217 contained... more Of 261 strains of Neisseria gonorrhoeae examined for plasmids, 6 were plasmid-free, 217 contained only a small multicopy 2.6 x lo6 dalton plasmid and 38 carried a large 24.5 x los dalton plasmid. Restriction enzyme digests and DNA-DNA hybridization studies revealed that the large plasmids isolated between 1940 and 1978 share a common core of DNA sequences (70 to 100%) and represent a group of closely related molecules.
Journal of Clinical Microbiology, Feb 1, 1992
We developed a polymerase chain reaction (PCR)-based test for detecting the protozoan parasite Tr... more We developed a polymerase chain reaction (PCR)-based test for detecting the protozoan parasite Trichomonas vaginalis. Genomic libraries were constructed from two independent clinical isolates of T. vaginalis. From these libraries, 12 genomic clones were purified, sequenced, and then screened for uniqueness by computerassisted sequence comparisons. PCR reactions were performed to evaluate eight PCR-primer pairs, including a primer pair that targeted the T. vaginalis ferredoxin gene. All eight primer pairs yielded PCR products of the expected sizes. However, six of the primer pairs amplified their respective target sequences in limited numbers of clinical T. vaginalis isolates, suggesting the presence of significant genomic variability among isolates. An exception was a primer pair, termed TVA5-TVA6, that amplified a 102-bp genomic sequence, termed A6p, in all of 24 clinical isolates. The A6p sequence was not detected by PCR in human DNA or in a wide variety of flagellates, ciliates, or bacteria tested. The A6p sequence appears highly selective for a broad range of T. vaginalis isolates and holds promise for PCR-based diagnosis of the parasite.
Molecular and Cellular Probes, Oct 1, 1993
Journal of Clinical Microbiology, 1984
Seventy strains of Mobiluncus, motile curved anaerobic bacteria associated with bacterial vaginos... more Seventy strains of Mobiluncus, motile curved anaerobic bacteria associated with bacterial vaginosis, were correctly identified to species level by using bacteria fixed to nitrocellulose and hybridized with 32P-labeled DNA.
Antimicrobial Agents and Chemotherapy, 1996
Journal of Bacteriology, 1987
Transposon Tn916 was transferred from Streptococcus faecalis to Mycoplasma hominis by a mating pr... more Transposon Tn916 was transferred from Streptococcus faecalis to Mycoplasma hominis by a mating process resembling conjugation with a frequency of 10(-6) to 10(-7). Tn916 was inserted into the mycoplasmal chromosome in single and multiple copies.
Antimicrobial Agents and Chemotherapy, 1991
Two tetracycline-resistant (Tcr) Moraxella (Branhamella) catarrhalis strains from England were co... more Two tetracycline-resistant (Tcr) Moraxella (Branhamella) catarrhalis strains from England were compared with two previously characterized Tcr Texas strains. Both pairs carried the Tet B determinant, which was nontransferable. Pulsed-field gel electrophoresis of their genomic DNA restriction fragments demonstrated that the strains from the same area were identical (clonal); however, the Texas and English strains differed from each other.
Antimicrobial Agents and Chemotherapy, 1994
Genital and anorectal isolates of Neisseria meningitidis were characterized, and their antimicrob... more Genital and anorectal isolates of Neisseria meningitidis were characterized, and their antimicrobial susceptibilities were determined. Twelve of 43 isolates demonstrated moderate susceptibility to penicillin G (MIC range, 0.125 to 0.5 microgram/ml). Two isolates were resistant to tetracycline (MIC, > or = 8 micrograms/ml) and contained plasmids of 25.2 MDa.
Antimicrobial Agents and Chemotherapy, 1988
Similar to Neisseria gonorrhoeae, tetracycline-resistant isolates of N. meningitidis, Kingella de... more Similar to Neisseria gonorrhoeae, tetracycline-resistant isolates of N. meningitidis, Kingella denitrificans, and Eikenella corrodens contained 25.2-megadalton plasmids carrying the TetM determinant. In contrast, tetracycline-resistant N. subflava biovar perflava-N. sicca and N. mucosa isolates carried the TetM determinant in the chromosome.
Antimicrobial Agents and Chemotherapy, 1986
Clinical isolates of Gardnerella vaginalis, Streptococcus agalactiae, Bacteroides spp., and Mobil... more Clinical isolates of Gardnerella vaginalis, Streptococcus agalactiae, Bacteroides spp., and Mobiluncus spp. were screened for resistance to tetracycline and for the presence of the streptococcal tetM determinant. The S. agalactiae and G. vaginalis strains contained DNA sequences homologous to the tetM determinant, while strains of the other two genera did not.
Antimicrobial Agents and Chemotherapy, 1989
The increasing resistance of genital mycoplasmas to tetracycline poses a problem because tetracyc... more The increasing resistance of genital mycoplasmas to tetracycline poses a problem because tetracycline is one of the few antimicrobial agents active against Mycoplasma hominis, Ureaplasma urealyticum, chlamydiae, gonococci, and other agents of genitourinary-tract disease. Since the quinolones are a promising group of antimicrobial agents, the susceptibilities of M. hominis and U. urealyticum to the newer 6-fluoroquinolones were determined by the agar dilution method. Ciprofloxacin, difloxacin, and ofloxacin had good activity against M. hominis, with the MIC for 50% of isolates tested (MIC50) being 1 microgram/ml. Fleroxacin, lomefloxacin, pefloxacin, and rosoxacin had MIC50s of 2 micrograms/ml. Enoxacin, norfloxacin, and amifloxacin had MIC50s of 8 to 16 micrograms/ml, and cinoxacin and nalidixic acid were inactive (MIC50, greater than or equal to 256 micrograms/ml). Overall, the activities of 6-fluoroquinolones for ureaplasmas were similar to those for M. hominis, with MICs being th...
Antimicrobial Agents and Chemotherapy, 1995
To assess the activities of two glycylcyclines, N,N-dimethylglycylamido (DMG) derivatives of mino... more To assess the activities of two glycylcyclines, N,N-dimethylglycylamido (DMG) derivatives of minocycline (MINO) and 6-demethyl-6-deoxytetracycline (DMDOT), 203 gonococcal isolates recovered at six sexually transmitted disease clinics in the western United States were evaluated. Antimicrobial susceptibilities to tetracycline HCl, doxycycline, MINO, DMG-DMDOT, and DMG-MINO were determined by agar dilution tests. DMG-DMDOT and DMG-MINO were more active than tetracycline HCl, doxycycline, or MINO regardless of the presence of Tet M or of chromosomal mutations mediating tetracycline resistance (P < 0.001).
Journal of Antimicrobial Chemotherapy, Oct 1, 1997
Journal of Clinical Periodontology, Oct 1, 2002
ABSTRACT
Applied and Environmental Microbiology, 1996
An erythromycin-resistant (Em r) Listeria innocua and an Em r Listeria monocytogenes isolate both... more An erythromycin-resistant (Em r) Listeria innocua and an Em r Listeria monocytogenes isolate both carried ermC genes, which code for rRNA methylases. The ermC genes were transferable by conjugation to recipient L. monocytogenes, Listeria ivanovii, and Enterococcus faecalis but did not appear to be associated with conjugative plasmids. Listeria species are widespread in the environment and the intestines of humans and animals and can also be found in food (1, 4, 6, 11). Until recently, the genus was thought to be uniformly susceptible to antibiotics active against gram-positive bacteria. Penicillin is normally the drug of choice for treatment, but both erythromycin and tetracycline are alternatives for patients who are allergic to penicillin (8). Now both singly and multiply antibiotic-resistant listerias have been described (3, 4, 6, 7, 9, 11, 13). We (7) as well as others (4, 9, 11) have found tetracycline resistance due to the Tet M determinant in Listeria innocua, Listeria monocytogenes, and, more recently, Listeria welshimeri from food, the environment, and human disease. The Tet K and L determinants have been found in a few L. innocua isolates from food (7), while the Tet S determinant has been found in L. monocytogenes, L. innocua, and L. welshimeri (3, 4). Multiantibiotic resistance plasmids encoding chloramphenicol (cat221/cat223), macrolide/lincosamide/ streptogramin (MLS) (ermB), and tetracycline resistance (tetM) or chloramphenicol, MLS, streptomycin, and tetracycline resistance have been found in L. monocytogenes from both France and Switzerland (9). Recently, trimethoprim and streptomycin resistance has also been found in the genus (4). One streptomycin-resistant L. innocua strain carried a streptomycin nucleotidyltransferase related to the aad6 gene (4). These reports illustrate that more listerias are becoming antibiotic resistant by the acquisition of known gram-positive antibiotic resistance genes. We have been examining antibiotic resistance genes in listerias isolated from food (6, 7). Previously, we found that 11 of 12 L. innocua isolates from chicken or turkey frankfurters and mozzarella cheese were resistant to tetracycline and carried the tetM gene (6, 7). In the same studies, we identified one L. innocua and one L. monocytogenes strain which were resistant to erythromycin (MIC, Ͼ256 g/ml). Neither was tetracycline resistant. The L. monocytogenes isolate carried two small plasmids of roughly 3 and 7 kb. In this study on erythromycin determinants, Southern blots of purified total cell DNA (7, 10) were hybridized under stringent conditions with each of the following intragenic Erm probes: Erm A, pEM9592, 0.7-kb SspI; Erm B, pJIR229, 0.8-kb PstI-EcoRI; Erm C, pBR328: 33RV, 0.9-kb HpaI (15-17). We found that both isolates hy
Applied and Environmental Microbiology, 1993
Eleven of 12 tetracycline-resistant Listeria innocua strains, isolated from chicken or turkey fra... more Eleven of 12 tetracycline-resistant Listeria innocua strains, isolated from chicken or turkey frankfurters and mozzarella cheese, were shown to carry DNA sequences which hybridized with the Tet M probe; of these, two strains also hybridized with Tet K. The remaining strain hybridized with the Tet K probe only. The Tet M determinant appeared to be located on the chromosome; in one case, it was transferable by conjugation to recipients Listeria monocytogenes, Listeria ivanovii, and Enterococcus faecalis.
Frontiers in Microbiology, Feb 5, 2015
Users may download and print one copy of any publication from the public portal for the purpose... more Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Antimicrobial Agents and Chemotherapy, 1991
Tetracycline-resistant Tet M-negative isolates of Actinomyces viscosus, Eubacterium lentum, Mobil... more Tetracycline-resistant Tet M-negative isolates of Actinomyces viscosus, Eubacterium lentum, Mobiluncus curtisii, and Mobiluncus mulieris were screened with the Tet K, Tet L, and Tet O DNA probes. Ten (71%) of the resistant Mobiluncus strains hybridized with the Tet O probe, two of the three E. lentum strains hybridized with the Tet K probe, and the A. viscosus isolate hybridized with the Tet L probe.
Critical Reviews in Oral Biology & Medicine, 1998
In the last 20 years, changes in world technology have occurred which have allowed for the rapid ... more In the last 20 years, changes in world technology have occurred which have allowed for the rapid transport of people, food, and goods. Unfortunately, antibiotic residues and antibiotic-resistant bacteria have been transported as well. Over the past 20 years, the rise in antibiotic-resistant gene carriage in virtually every species of bacteria, not just oral/respiratory bacteria, has been documented. In this review, the main mechanisms of resistance to the important antibiotics used for treatment of disease caused by oral/respiratory bacteria-including β-lactams, tetracycline, and metronidazole-are discussed in detail. Mechanisms of resistance for macrolides, lincosamides, streptogramins, trimethoprim, sulfonamides, aminoglycosides, and chloramphenicol are also discussed, along with the possible role that mercury resistance may play in the bacterial ecology.
Journal of Bacteriology, Apr 1, 1978
An indigenous Neisseria gonorrhoeae conjugative plasmid, pLE2450, was tested for its ability to m... more An indigenous Neisseria gonorrhoeae conjugative plasmid, pLE2450, was tested for its ability to mediate chromosomal gene transfer between gonococcal strains. Plasmid-mediated chromosomal transfer was detected at a low frequency and can be used to establish certain linkage relationships between amino acid and antibiotic resistance markers.
Journal of General Microbiology, 1979
Of 261 strains of Neisseria gonorrhoeae examined for plasmids, 6 were plasmid-free, 217 contained... more Of 261 strains of Neisseria gonorrhoeae examined for plasmids, 6 were plasmid-free, 217 contained only a small multicopy 2.6 x lo6 dalton plasmid and 38 carried a large 24.5 x los dalton plasmid. Restriction enzyme digests and DNA-DNA hybridization studies revealed that the large plasmids isolated between 1940 and 1978 share a common core of DNA sequences (70 to 100%) and represent a group of closely related molecules.
Journal of Clinical Microbiology, Feb 1, 1992
We developed a polymerase chain reaction (PCR)-based test for detecting the protozoan parasite Tr... more We developed a polymerase chain reaction (PCR)-based test for detecting the protozoan parasite Trichomonas vaginalis. Genomic libraries were constructed from two independent clinical isolates of T. vaginalis. From these libraries, 12 genomic clones were purified, sequenced, and then screened for uniqueness by computerassisted sequence comparisons. PCR reactions were performed to evaluate eight PCR-primer pairs, including a primer pair that targeted the T. vaginalis ferredoxin gene. All eight primer pairs yielded PCR products of the expected sizes. However, six of the primer pairs amplified their respective target sequences in limited numbers of clinical T. vaginalis isolates, suggesting the presence of significant genomic variability among isolates. An exception was a primer pair, termed TVA5-TVA6, that amplified a 102-bp genomic sequence, termed A6p, in all of 24 clinical isolates. The A6p sequence was not detected by PCR in human DNA or in a wide variety of flagellates, ciliates, or bacteria tested. The A6p sequence appears highly selective for a broad range of T. vaginalis isolates and holds promise for PCR-based diagnosis of the parasite.
Molecular and Cellular Probes, Oct 1, 1993
Journal of Clinical Microbiology, 1984
Seventy strains of Mobiluncus, motile curved anaerobic bacteria associated with bacterial vaginos... more Seventy strains of Mobiluncus, motile curved anaerobic bacteria associated with bacterial vaginosis, were correctly identified to species level by using bacteria fixed to nitrocellulose and hybridized with 32P-labeled DNA.
Antimicrobial Agents and Chemotherapy, 1996
Journal of Bacteriology, 1987
Transposon Tn916 was transferred from Streptococcus faecalis to Mycoplasma hominis by a mating pr... more Transposon Tn916 was transferred from Streptococcus faecalis to Mycoplasma hominis by a mating process resembling conjugation with a frequency of 10(-6) to 10(-7). Tn916 was inserted into the mycoplasmal chromosome in single and multiple copies.
Antimicrobial Agents and Chemotherapy, 1991
Two tetracycline-resistant (Tcr) Moraxella (Branhamella) catarrhalis strains from England were co... more Two tetracycline-resistant (Tcr) Moraxella (Branhamella) catarrhalis strains from England were compared with two previously characterized Tcr Texas strains. Both pairs carried the Tet B determinant, which was nontransferable. Pulsed-field gel electrophoresis of their genomic DNA restriction fragments demonstrated that the strains from the same area were identical (clonal); however, the Texas and English strains differed from each other.
Antimicrobial Agents and Chemotherapy, 1994
Genital and anorectal isolates of Neisseria meningitidis were characterized, and their antimicrob... more Genital and anorectal isolates of Neisseria meningitidis were characterized, and their antimicrobial susceptibilities were determined. Twelve of 43 isolates demonstrated moderate susceptibility to penicillin G (MIC range, 0.125 to 0.5 microgram/ml). Two isolates were resistant to tetracycline (MIC, > or = 8 micrograms/ml) and contained plasmids of 25.2 MDa.
Antimicrobial Agents and Chemotherapy, 1988
Similar to Neisseria gonorrhoeae, tetracycline-resistant isolates of N. meningitidis, Kingella de... more Similar to Neisseria gonorrhoeae, tetracycline-resistant isolates of N. meningitidis, Kingella denitrificans, and Eikenella corrodens contained 25.2-megadalton plasmids carrying the TetM determinant. In contrast, tetracycline-resistant N. subflava biovar perflava-N. sicca and N. mucosa isolates carried the TetM determinant in the chromosome.
Antimicrobial Agents and Chemotherapy, 1986
Clinical isolates of Gardnerella vaginalis, Streptococcus agalactiae, Bacteroides spp., and Mobil... more Clinical isolates of Gardnerella vaginalis, Streptococcus agalactiae, Bacteroides spp., and Mobiluncus spp. were screened for resistance to tetracycline and for the presence of the streptococcal tetM determinant. The S. agalactiae and G. vaginalis strains contained DNA sequences homologous to the tetM determinant, while strains of the other two genera did not.
Antimicrobial Agents and Chemotherapy, 1989
The increasing resistance of genital mycoplasmas to tetracycline poses a problem because tetracyc... more The increasing resistance of genital mycoplasmas to tetracycline poses a problem because tetracycline is one of the few antimicrobial agents active against Mycoplasma hominis, Ureaplasma urealyticum, chlamydiae, gonococci, and other agents of genitourinary-tract disease. Since the quinolones are a promising group of antimicrobial agents, the susceptibilities of M. hominis and U. urealyticum to the newer 6-fluoroquinolones were determined by the agar dilution method. Ciprofloxacin, difloxacin, and ofloxacin had good activity against M. hominis, with the MIC for 50% of isolates tested (MIC50) being 1 microgram/ml. Fleroxacin, lomefloxacin, pefloxacin, and rosoxacin had MIC50s of 2 micrograms/ml. Enoxacin, norfloxacin, and amifloxacin had MIC50s of 8 to 16 micrograms/ml, and cinoxacin and nalidixic acid were inactive (MIC50, greater than or equal to 256 micrograms/ml). Overall, the activities of 6-fluoroquinolones for ureaplasmas were similar to those for M. hominis, with MICs being th...
Antimicrobial Agents and Chemotherapy, 1995
To assess the activities of two glycylcyclines, N,N-dimethylglycylamido (DMG) derivatives of mino... more To assess the activities of two glycylcyclines, N,N-dimethylglycylamido (DMG) derivatives of minocycline (MINO) and 6-demethyl-6-deoxytetracycline (DMDOT), 203 gonococcal isolates recovered at six sexually transmitted disease clinics in the western United States were evaluated. Antimicrobial susceptibilities to tetracycline HCl, doxycycline, MINO, DMG-DMDOT, and DMG-MINO were determined by agar dilution tests. DMG-DMDOT and DMG-MINO were more active than tetracycline HCl, doxycycline, or MINO regardless of the presence of Tet M or of chromosomal mutations mediating tetracycline resistance (P < 0.001).
Journal of Antimicrobial Chemotherapy, Oct 1, 1997
Journal of Clinical Periodontology, Oct 1, 2002
ABSTRACT