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R J Wallace

Publications and source records attributed to R J Wallace.

At least 19 recordsLinked to original sources
PubMed1992

Rumen microbiology, biotechnology and ruminant nutrition: the application of research findings to a complex microbial ecosystem.

Research on rumen microorganisms has contributed greatly to our understanding of anaerobic microbial ecosystems, and has also influenced feeding practices and nutritional modelling with ruminants. However, it can be argued that rumen microbiology has not yet fulfilled its true potential. Growth-promoting ionophores, antibiotics and microbial feed additives were introduced before their microbiological effects had been determined. A more pro-active role for the microbiologist was predicted with the advent of recombinant DNA technology. Whether ventures in molecular biology can be applied successfully to benefit nutrition and health is likely to depend on whether means can be found for maintaining new strains in vivo.

Animal Feed↗
PubMed1992

Selective isolation of bacteria with dipeptidyl aminopeptidase type I activity from the sheep rumen.

Five-hundred-and-six fresh isolates of rumen bacteria were tested for their ability to hydrolyse the synthetic substrate for dipeptidyl aminopeptidase type I, GlyArg-4-methoxy-2-naphthylamide (GlyArg-MNA), using a gel overlay technique. Twelve positive isolates were small Gram-negative rods which resembled Bacteroides ruminicola in their biochemical and morphological properties. SDS-PAGE of whole cell extracts indicated that two were similar to B. ruminicola strain B14, six resembled B. ruminicola strain M384, and four were similar to B. ruminicola GA33. All hydrolysed GlyArg-MNA, Ala2 and Ala5, and showed no activity against Leu-MNA. Ala3 and Ala2, but no Ala4, was produced from Ala5. The different groups had different, distinctive activity profiles. The two remaining positive isolates were Lactobacillus spp. with an exceptionally high Leu-MNA activity. It was concluded that, although different strains may only be distantly related, B. ruminicola forms the most important group of bacteria in the rumen to possess a dipeptidyl aminopeptidase type I activity.

Animals↗
PubMed1992

Cloning and DNA sequence of the Mycobacterium fortuitum var fortuitum plasmid pAL5000.

The complete nucleotide sequence of the Mycobacterium fortuitum var fortuitum plasmid pAL5000 has been determined. Computer analysis of this 4821-bp plasmid for protein coding regions, based on mycobacterial codon usage preferences, reveals the presence of two putative protein coding regions immediately downstream from typical mycobacterial promoter and ribosome binding sites. Both open reading frames, ORF1 and ORF2, produced proteins with the predicted respective sizes previously shown in minicell expression experiments [A. Labidi et al. (1985) FEMS Microbiol. Lett. 30, 221-225]. ORF1 encodes a putative 20-kDa basic protein with characteristics of a DNA binding protein involved in plasmid DNA replication. ORF2 encodes a 67-kDa protein with an amino-terminal sequence suggestive of a transported protein and a possible transmembrane anchor near its carboxyl-terminal. The current sequence and its analysis are more consistent with the minicell expression experiments than the previously published sequence of the pAL5000 plasmid [J. Rauzier et al. (1988) Gene 71, 315-321].

Amino Acid Sequence↗
PubMed1992

Isoelectric focusing patterns of beta-lactamases in the rapidly growing mycobacteria.

beta-lactamases from 259 strains of rapidly growing mycobacteria that included the third biovariant complex of Mycobacterium fortuitum, M. peregrinum, M. abscessus, M. chelonae, the M. chelonae-like organisms (MCLO), and M. smegmatis were analyzed by isoelectric focusing (IEF). All isolates produced acidic beta-lactamases with major band isoelectric points (pIs) between 4.4 and 6.0. Each of the 6 taxonomic groups exhibited 1 or 2 characteristic beta-lactamase IEF patterns. Heterogeneity among IEF patterns was evident in 5 of the 6 groups, however, and was greatest among the third biovariant complex of M. fortuitum. beta-lactamase patterns correlated with previously identified taxonomic subgroups of M. smegmatis and the third biovariant complex of M. fortuitum. beta-lactamase IEF analysis of MCLO strains isolated from two outbreaks demonstrated its possible usefulness for epidemiologic evaluation.

Animals↗
PubMed1992

Acetylation of peptides inhibits their degradation by rumen micro-organisms.

Proteins and peptides were acetylated using acetic anhydride in order to block their N-terminal amino groups and thereby to prevent their hydrolysis by rumen microbial aminopeptidases. The effects of acetylation on peptide breakdown and ammonia production were determined by incubating unmodified and acetylated substrates with sheep rumen micro-organisms in vitro. Ammonia production from casein and lactalbumin was affected little by acetylation, but acetylation of the corresponding enzymic hydrolysates caused ammonia production to be more than halved after 3-6 h incubation. Estimation of peptides remaining in rumen fluid showed that the decreased ammonia production was a consequence of peptides being hydrolysed more slowly. Acetylated Ala-Ala, Ala-Ala-Ala (Ala3), Leu-Gly-Gly, Phe-Gly-Gly and Val-Gly-Ser-Glu survived incubation with rumen fluid in vitro for 6 h, whereas almost none of the corresponding unmodified peptides was present at 6 h. The protection afforded to larger pure peptides was less reliable: for example, 72% of acetylated bradykinin was hydrolysed after 1 h. N-Acetyl Ala3 had only a minor inhibitory effect on the breakdown of Ala3 and Ala4, suggesting that although acetyl peptides were broken down more slowly than unmodified peptides they did not inhibit peptidase activity.

Acetylation↗
PubMed1992

Tsukamurella paurometabolum: a novel pathogen causing catheter-related bacteremia in patients with cancer.

Tsukamurella paurometabolum is a weakly acid-fast, pleomorphic gram-positive bacterium found in soil. Human infection due to this organism has rarely been described, and there are no published accounts of bacteremia. Three cases of bacteremia due to T. paurometabolum and related to long-term use of a central venous catheter in patients with cancer who were receiving chemotherapy are described.

Actinomycetales↗
PubMed1992

Skin, soft tissue, and bone infections due to Mycobacterium chelonae chelonae: importance of prior corticosteroid therapy, frequency of disseminated infections, and resistance to oral antimicrobials other than clarithromycin.

Little is known of clinical disease due to Mycobacterium chelonae chelonae. One hundred skin, soft tissue, or bone isolates of this rapidly growing mycobacterium were identified over 10 years. Clinical disease included disseminated cutaneous infection (53%); localized cellulitis, abscess, or osteomyelitis (35%); and catheter infections (12%). Underlying conditions with disseminated infection included organ transplantation, rheumatoid arthritis, and autoimmune disorders; 92% involved corticosteroid use. Trauma and medical procedures were risk factors for localized infections. Corticosteroids and chronic renal failure were risk factors for catheter infections. Overall, 62% of patients were receiving corticosteroids and 72% were immunosuppressed. MICs of six oral antimicrobials were obtained for 180 isolates by broth microdilution. Up to 20% of isolates were susceptible to doxycycline, ciprofloxacin, ofloxacin, and sulfamethoxazole. In contrast, 100% were susceptible to clarithromycin (MICs less than or equal to 1 microgram/mL). Disease due to M. chelonae chelonae usually occurs in the setting of corticosteroid therapy and is often disseminated; the organisms require high MICs of oral antimicrobials other than clarithromycin.

Abscess↗
PubMed1992

Properties of ionophore-resistant Bacteroides ruminicola enriched by cultivation in the presence of tetronasin.

Bacteroides ruminicola M384 was grown in the presence of increasing concentrations of tetronasin, an ionophore that has been developed as a feed additive for ruminants. The resulting culture, B. ruminicola M384/TnR, was then maintained in medium containing 0.1 microgram tetronasin/ml. Growth of the parent strain was eliminated by the addition of 0.1 micrograms tetronasin/ml, but the growth rate of B. ruminicola M384/TnR, which grew more slowly than the parent strain, was unaffected by adding tetronasin. Bacteroides ruminicola M384/TnR retained its resistance to tetronasin even after repeated subculture in the absence of the ionophore, suggesting that a mutation had occurred. The absence of plasmids in individual colonies of B. ruminicola M384/TnR implied that the mutation was chromosomal. Bacteroides ruminicola M384/TnR was also more resistant to the ionophores monensin and lasalocid and, to a lesser degree, to the antibiotic avoparcin than B. ruminicola M384. Binding of [14C]tetronasin to B. ruminicola M384/TnR was lower than binding of the ionophore to the parent stain, and this difference was eliminated by washing cells with EDTA. The peptidolytic activity of B. ruminicola M384 towards triphenylalanine (Mr = 460) was unaffected in B. ruminicola M384/TnR, but the rate of breakdown tetraphenylalanine (Mr = 607) was decreased. This difference was also abolished by EDTA. It was concluded that growth of B. ruminicola in the presence of tetronasin resulted in a mutation affecting the permeability of the cell envelope, such that permeation of tetronasin and molecules of a similar size (Mr = 628) was decreased.

Animals↗
PubMed1992

Activities of four macrolides, including clarithromycin, against Mycobacterium fortuitum, Mycobacterium chelonae, and M. chelonae-like organisms.

Susceptibilities to erythromycin by broth microdilution were compared with those to the newer macrolide clarithromycin for 223 isolates of rapidly growing mycobacteria belonging to seven taxonomic groups. Seventy-nine random isolates were also tested against azithromycin and roxithromycin. The MIC of clarithromycin for 90% of strains tested (MIC90) was 0.25 microgram/ml for isolates of Mycobacterium chelonae subsp. chelonae and 0.5 microgram/ml for M. chelonae subsp. abscessus, with 100% of strains inhibited by less than or equal to 1 microgram/ml. Clarithromycin was 10 to 50 times more active than erythromycin and four- to eightfold more active than the other newer macrolides against M. chelonae. MICs of clarithromycin frequently increased with prolonged incubation with isolates of M. chelonae subsp. abscessus but not M. chelonae subsp. chelonae. MICs of clarithromycin were much higher for M. fortuitum bv. fortuitum (MIC50, 2.0 microgram/ml; MIC90, greater than 8.0 microgram/ml). The three newer macrolides had comparable activity against M. fortuitum bv. peregrinum (MIC90s of 0.5 to 2.0 microgram/ml compared with erythromycin MIC90s of greater than 8.0 microgram/ml). Overall, clarithromycin was the most active agent, inhibiting all isolates of M. chelonae subsp. chelonae, M. chelonae subsp. abscessus, M. fortuitum bv. peregrinum, and the M. chelonae-like organisms and 35% of M. fortuitum bv. fortuitum at less than or equal to 1 microgram/ml. Clinical trials of the newer macrolides, especially clarithromycin, against these environmental mycobacterial species appear to be warranted.

Azithromycin↗
PubMed1992

Activities of clarithromycin against eight slowly growing species of nontuberculous mycobacteria, determined by using a broth microdilution MIC system.

MICs of clarithromycin against 324 clinical isolates belonging to eight species of slowly growing nontuberculous mycobacteria were determined by using a broth microdilution system. Isolates were inoculated into twofold drug dilutions in Middlebrook 7H9 broth (pH corrected to 7.4) and then incubated at 30 degrees C for 7 days for Mycobacterium marinum and for 14 days for all other species. The MIC for 90% of the strains (MIC90) was less than or equal to 0.5 micrograms/ml for isolates of Mycobacterium gordonae (6 strains), Mycobacterium scrofulaceum (5 strains), Mycobacterium szulgai (6 strains), and Mycobacterium kansasii (35 strains). MICs for M. marinum (25 strains) and Mycobacterium avium complex (237 strains) were higher, but 100% and 89% of the strains, respectively, were susceptible to less than or equal to 4 micrograms/ml. In contrast, MICs for five of six M. simiae strains were greater than 8 micrograms/ml, and the range of MICs for Mycobacterium nonchromogenicum varied from less than or equal to 0.125 to 8 micrograms/ml. For the 237 isolates of M. avium complex, the MIC50 was 2 micrograms/ml and the MIC90 was 8 micrograms/ml. MICs for most isolates (77%) were in the 1- to 4-micrograms/ml range. For the 80 isolates in this group known to be from AIDS patients, the MIC50 was 4 micrograms/ml and the MIC90 was 8 micrograms/ml. These MIC studies combined with preliminary clinical trials suggest that clarithromycin may be useful for drug therapy of most species of the slowly growing nontuberculous mycobacteria except M. simiae.

Clarithromycin↗
PubMed1992

Large restriction fragment patterns of genomic Mycobacterium fortuitum DNA as strain-specific markers and their use in epidemiologic investigation of four nosocomial outbreaks.

Pulsed-field gel electrophoresis and restriction endonucleases with rare recognition sites were used to generate large restriction fragment (LRF) patterns of genomic DNA from 48 isolates of Mycobacterium fortuitum biovariant fortuitum. Epidemiologically unrelated isolates gave highly diverse patterns when AsnI, HpaI, AflII, DraI, NdeI, XbaI, SpeI, or SspI was used. Epidemiologically related isolates produced identical or minimally different LRF patterns. Minor variations in LRF patterns were seen in two epidemic isolates digested with XbaI, suggesting that genetic alteration had occurred. LRF patterns were used to study three cardiac surgery wound infection outbreaks and one respiratory disease nosocomial outbreak. In two outbreaks, LRF patterns confirmed the reported clustering of isolates on the basis of multiple phenotyping methods. In the remaining two outbreaks, isolates which could not be separated by prior typing methods were easily distinguished by LRF pattern analysis. Environmental water isolates from two outbreaks had LRF patterns identical to those of the disease-producing strains, confirming that the local environment was the source of infection. Pulsed-field gel electrophoresis of LRFs of genomic DNA offers great promise as an epidemiologic tool for the study of M. fortuitum.

Cross Infection↗
PubMed1992

DNA polymorphisms in strains of Mycobacterium tuberculosis analyzed by pulsed-field gel electrophoresis: a tool for epidemiology.

Mycobacterium tuberculosis isolates were studied by comparing large restriction fragment (LRF) patterns produced by digestion of chromosomal DNA with infrequent-cutting endonucleases and pulsed-field gel electrophoresis. Four cultures of H37Rv and 36 clinical isolates of M. tuberculosis were compared by using DraI, AsnI, XbaI, and SpeI. DraI and AsnI allowed easy visual separation of 18 of 21 epidemiologically unrelated strains. XbaI and SpeI allowed discrimination of all 21 unrelated strains, including the 3 strains inseparable with DraI and AsnI, but comparison of LRF patterns was more tedious because of overlapping fragments. A total of 26 isolates belonging to 10 clusters of related isolates were compared by pulsed-field gel electrophoresis, with all related isolates giving identical LRF patterns. These included multiple isolates from the same patient or the same family. The same grouping of clustered isolates was obtained when BamHI DNA digests were hybridized with two probes from the insertion sequence IS6110. Long-term laboratory passage of H37Rv produced minimal detectable changes in LRF patterns. LRF patterns are useful tools for epidemiologic studies of tuberculosis without the need for radioactive or specific DNA probes.

DNA Fingerprinting↗
PubMed1992

beta-Lactamase inhibitors and the inducibility of the beta-lactamase of Mycobacterium tuberculosis.

Ten clinical isolates and the type strain (H37Rv) of Mycobacterium tuberculosis were shown to produce an intracellular beta-lactamase. Crude enzyme preparations were extracted from acetone cell powders by grinding with zirconium beads in 0.133 M glycine with 1.0% Triton X-100. The enzymes had identical patterns on isoelectric focusing, with two major bands at isoelectric points of 4.9 and 5.1. The beta-lactamase was highly susceptible to the new beta-lactamase inhibitor BRL 42715, with an I50 of 0.0001 microgram/ml. The enzyme was also susceptible to clavulanic acid with an I50 (0.05 microgram/ml), which was similar to the value for the common bacterial beta-lactamase TEM-1 (0.01 microgram/ml). The latter result is consistent with previous MIC studies with M. tuberculosis, which have shown synergy between clavulanic acid and amoxicillin. BRL 42715 and clavulanic acid were more active than sulbactam, tazobactam, and cloxacillin. These studies support the potential value of penicillin/clavulanic acid and penicillin/BRL 42715 combinations in the treatment of tuberculosis.

Dose-Response Relationship, Drug↗
PubMed1992

Contamination of flexible fiberoptic bronchoscopes with Mycobacterium chelonae linked to an automated bronchoscope disinfection machine.

Between December 5, 1989, and September 25, 1990, Mycobacterium chelonae was isolated from endoscopic or bronchial washings in 14 patients on a single clinical service. A phenotypically unique strain of M. chelonae subspecies abscessus that was highly resistant to cefoxitin (MIC greater than 256 micrograms/ml) and different from 13 control isolates of M. chelonae recovered elsewhere in the hospital was identified in all these patients and the rinse water from the bronchoscope disinfecting machine. None of the outbreak patients had evidence of invasive M. chelonae disease. Aggressive infection control measures on the disinfecting machine, including use of sterile water in the wash and rinse cycles, increasing the 2% alkaline glutaraldehyde exposure time, frequent replacement of the glutaraldehyde, and disinfection of the machine, failed to eradicate the M. chelonae, presumably because of the presence of a biofilm inside the machine. Rinsing the scopes with 70% alcohol after automated disinfection eliminated the outbreak strain. This study demonstrates that automated bronchoscope disinfecting machines may become heavily contaminated with mycobacteria that resist usual disinfection, resulting in a source of bronchoscope contamination.

Bronchoscopes↗
PubMed1991

Clinical disease, drug susceptibility, and biochemical patterns of the unnamed third biovariant complex of Mycobacterium fortuitum.

Previous studies of Mycobacterium fortuitum identified isolates that did not fit its two recognized biovariants. Eighty-five clinical isolates of this group, the "third biovariant complex", were evaluated. They represented 16% of 410 isolates of M. fortuitum submitted to a Texas laboratory and 22% of 45 isolates in Queensland, Australia. Most infections (76%) involved skin, soft tissue, or bone and occurred after metal puncture wounds or open fractures. Isolates differed from biovar fortuitum in resistance to pipemidic acid and use of mannitol and inositol as carbon sources. Two subgroups were present, and examples were deposited in the American Type Culture Collection. Isolates were resistant to doxycycline and one-third were resistant to cefoxitin. All were susceptible to amikacin, ciprofloxacin, sulfamethoxazole, and imipenem. Surgical debridement combined with drug therapy based on in vitro susceptibilities resulted in cures of cutaneous disease or osteomyelitis. DNA homology studies are needed to determine the taxonomic status of these organisms.

Bacterial Typing Techniques↗
PubMed1991

A survey of peptidase activity in rumen bacteria.

Twenty-nine strains of 14 species of rumen bacteria were screened for their ability to hydrolyse Ala2, Ala5, GlyArg-4-methoxy-2-naphthylamide (GlyArg-MNA) and Leu-MNA. Several species, notably Megasphaera elsdenii, were active against Ala2, and a smaller number, including Bacteroides ruminicola, Butyrivibrio fibrisolvens, Ruminococcus flavefaciens, Lachnospira multipara and Ruminobacter amylophilus, broke down Ala5. Streptococcus bovis had an exceptionally high leucine arylamidase activity. However, only Ba. ruminicola hydrolysed GlyArg-MNA. Further investigation revealed that only Ba. ruminicola and Bu. fibrisolvens hydrolysed Ala5 to Ala3 and Ala2, with little ALa4 being produced, in a manner similar to rumen fluid. The activity of Ba. ruminicola against synthetic peptidase substrates, including GlyArg-MNA, LysAla-MNA, ArgArg-MNA, GlyPro-MNA, LeuVal-MNA, and Ala3-p-nitroanilide, was similar to that of rumen fluid, whereas the activity of Bu. fibrisolvens was quite different. Since the main mechanism by which peptides are broken down in the rumen is similar to dipeptidyl aminopeptidase type I, for which GlyArg-MNA is a diagnostic substrate, it was concluded that Ba. ruminicola was the most important single species in peptide breakdown in the rumen.

Alanine↗
PubMed1991

Comparison of the activity of cefixime and activities of other oral antibiotics against adult clinical isolates of Moraxella (Branhamella) catarrhalis containing BRO-1 and BRO-2 and Haemophilus influenzae.

MICs of 10 oral antibiotics were determined for 105 Moraxella catarrhalis and 96 Haemophilus influenzae isolates from adults. A two- to fourfold increase in MICs of oral cephalosporins was seen in the presence of BRO-1 but not with TEM-1 or BRO-2. The MICs of cefixime for 90% of strains of H. influenzae (0.125 microgram/ml) and M. catarrhalis (0.25 microgram/ml) were 8- to 64-fold lower than those of other oral cephalosporins.

Administration, Oral↗