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J M Musser

Publications and source records attributed to J M Musser.

At least 37 records · Page 2Linked to original sources
PubMed2001

Identification and characterization of a second extracellular collagen-like protein made by group A Streptococcus: control of production at the level of translation.

A recent study found that group A Streptococcus (GAS) expresses a cell surface protein with similarity to human collagen (S. Lukomski, K. Nakashima, I. Abdi, V. J. Cipriano, R. M. Ireland, S. R. Reid, G. G. Adams, and J. M. Musser, Infect. Immun. 68:6542-6553, 2000). This streptococcal collagen-like protein (Scl) contains a long region of Gly-X-X motifs and was produced by serotype M1 GAS strains. In the present study, a second member of the scl gene family was identified and designated scl2. The Scl2 protein also has a collagen-like region, which in M1 strains is composed of 38 contiguous Gly-X-X triplet motifs. The scl2 gene was present in all 50 genetically diverse GAS strains studied. The Scl2 protein is highly polymorphic, and the number of Gly-X-X motifs in the 50 strains studied ranged from 31 in one serotype M1 strain to 79 in serotype M28 and M77 isolates. The scl1 and scl2 genes were simultaneously transcribed in the exponential phase, and the Scl proteins were also produced. Scl1 and Scl2 were identified in a cell-associated form and free in culture supernatants. Production of Scl1 is regulated by Mga, a positive transcriptional regulator that controls expression of several GAS virulence factors. In contrast, production of Scl2 is controlled at the level of translation by variation in the number of short-sequence pentanucleotide repeats (CAAAA) located immediately downstream of the GTG (Val) start codon. Control of protein production by this molecular mechanism has not been identified previously in GAS. Together, the data indicate that GAS simultaneously produces two extracellular human collagen-like proteins in a regulated fashion.

Amino Acid Sequence↗
PubMed2001

Transmission dynamics and molecular characterization of Mycobacterium tuberculosis isolates with low copy numbers of IS6110.

Population-based analysis of Mycobacterium tuberculosis transmission in Houston, Tex., over 5 years identified 377 patients infected with an isolate containing one to four copies of IS6110. The isolates were analyzed by spoligotyping and assigned to one of three major genetic groups based on nucleotide polymorphisms in codons katG 463 and gyrA 95. Prospectively obtained patient interviews were reviewed to assess epidemiologic links between apparently clustered patients. A total of 13 groups of isolates with the same IS6110 profile were identified, representing 326 of the 377 patients (86.5%; range 2 to 113 patients). In contrast, 28 groups of isolates containing 334 patients (88.6%) had the same spoligotype (range, 2 to 143 patients). Combination of IS6110 profile and spoligotype data identified 31 clusters with 300 patients (79.6%; range, 2 to 82 patients). All 377 isolates belonged to major genetic group 1 (77 patients) or genetic group 2 (300 patients); no major genetic group 3 isolates were identified. Among the 228 patients interviewed, 33 patients (14.5%) were directly linked to another patient in the same cluster. Possible epidemiologic links were also found among 11 patients. Moreover, many clusters consisted of individuals with the same ethnicity. In conclusion, we confirmed that IS6110 profiling and spoligotyping together provide enhanced molecular discrimination of M. tuberculosis isolates with low copy numbers of IS6110. Identification of epidemiologic links among some of the patients verified that the combination of these two methods reliably indexes tuberculosis transmission.

Bacterial Typing Techniques↗
PubMed2001

Treatment of isoniazid-resistant tuberculosis in southeastern Texas.

BACKGROUND: Isoniazid-resistant tuberculosis (INHr-TB) can be treated successfully with several treatment regimens. However, the optimal regimen and duration are unclear. STUDY OBJECTIVE: To analyze the efficacy of treatment regimens used for INHr-TB in the southeastern Texas region. DESIGN: Retrospective cohort study. SETTING: Health-care facilities reporting tuberculosis (TB) patients in the Houston and Tyler areas. SUBJECTS: All patients reported to have INHr-TB from 1991 to 1998. Exclusion criteria included poor compliance, additional first-line drug-resistance (except aminoglycosides), and death before completion of 1 month of treatment. MEASUREMENTS AND RESULTS: Main treatment outcomes were treatment failure, relapse, and TB-related death. Fifty-three of 83 patients were included in the study; aminoglycoside resistance coexisted in 37.5% of isolates. Seven types of treatment regimens were identified. Eighteen patients (34%) received rifampin, pyrazinamide, and ethambutol thrice weekly for 9 months. Four patients (7.5%) had a total effective treatment duration of < 9 months. Thirty patients (56.6%) and 16 patients (30.2%) received thrice-daily and daily treatment regimens, respectively. Forty-nine patients achieved sputum conversion. Treatment failure and death occurred in one patient (1.9%). Three patients (5.7%) experienced relapses. There was a significant difference in total effective treatment time between patients with and without relapses (8.3 +/- 1.1 months vs 11.1 +/- 2.1 months; p < 0.02). Twice-weekly treatment regimens were associated with relapse (p = 0.05). CONCLUSIONS: Several treatment regimens were prescribed for INHr-TB in southeastern Texas. INHr-TB treatment durations were > 7 months, and treatment regimen efficacy was adequate. Twice-weekly treatment was associated with relapse, whereas thrice-weekly and daily treatments performed similarly. A prospective study with different treatment durations is needed to determine the optimal treatment regimen for patients with INHr-TB.

Adolescent↗
PubMed2001

Screening method for identification of beta-lactams in bovine urine by use of liquid chromatography and a microbial inhibition test.

OBJECTIVE: To develop a multiple-residue screening method for the detection of beta-lactams in bovine urine. ANIMALS: 6 clinically normal Holstein cows and 6 calves. PROCEDURE: Pooled urine obtained from cows was used as a negative-control sample or spiked with varying concentrations of 6 beta-lactam antibiotics. Urine samples were prepared for liquid chromatography by diluting 1 ml of urine with 9 ml of 0.01M KH2PO4, 0.01 M Na2PO4, and filtering. Filtrate (2,000 ml) was eluted with a mobile phase in a gradient program. A fraction corresponding to each beta-lactam of interest was collected and evaporated to < 1 ml, and water then was added to achieve a 1 ml volume. The collected fraction was tested, using a microbial inhibition test. Then, calves were fed milk spiked with a mixture of 5 beta-lactam antibiotics at a concentration 40X the FDA tolerance in milk. Three hours following the feeding, urine samples were obtained from the calves and tested, as described for the urine samples for the cows. RESULTS: The lowest concentrations of amoxicillin, ampicillin, cephapirin, cloxacillin, desfuroylceftiofurcysteine, and penicillin G that were consistently detected in urine were 100, 10, 100, 250, 1,000, and 10 ng/ml, respectively. Amoxicillin, ampicillin, cephapirin, cloxacillin, desacetylcephapirin, and penicillin G were detected in urine samples of 6/6, 5/6, 0/6, 6/6, 2/6, and 3/6 calves respectively, fed antibiotic-spiked milk. CONCLUSIONS AND CLINICAL RELEVANCE: The integrated method described can be used to detect or identify beta-lactam antibiotics in bovine urine. This method can be used to test cattle for beta-lactam residues.

Animals↗
PubMed2001

Potential for milk containing penicillin G or amoxicillin to cause residues in calves.

The potential for antibiotic residues in calves from consuming milk containing penicillin G or amoxicillin was investigated. Six calves were fed milk replacer, 6% body weight twice daily, containing 0.293, 2.92, or 5.85 microg of penicillin/ml (ppm) G or 0.25, 1.0, or 2.0 microg of amoxicillin/ml for three consecutive feedings. Urine and blood samples were collected after each feeding. Serum and urine samples were tested with a microbial receptor assay and a microbial growth inhibition assay to indicate potential drug residues. Penicillin G and amoxicillin were detected in the serum and urine of several calves 3 h after drinking spiked milk replacer. Possible violative drug residues in the calves were detected by the microbial growth inhibition assay up to 15 h after drinking spiked milk replacer. Penicillin G, but not amoxicillin, could be detected in urine 24 h after the final feeding of spiked milk replacer. Subsequently, six calves were fed milk replacer containing 11.7 microg of penicillin G/ml (ppm) twice daily, 6% body weight per feeding. Calves were slaughtered 3 h after the final feeding. Mean (+/-SD) concentrations of penicillin G measured by high-pressure liquid chromatography in liver, kidney, muscle, and serum were 0.409 (+/-0.167) microg/g, 0.031 (+/-0.012) microg/g 0.008 (+/-0.002) microg/g, and 0.013 (+/-0.006) mg/ml, respectively. This study indicates that calves fed milk with amoxicillin or penicillin G could possibly have violative residues if slaughtered within 24 h after feeding. Violative drug residues in liver tissue were found in calves slaughtered 3 h after consuming milk replacer containing 11.7 microg of penicillin G/ml (ppm).

Amoxicillin↗
PubMed2001

Molecular diagnosis of mycobacteria.

Tuberculosis is one of the leading infectious diseases in the world and is responsible for more than 2 million deaths and 8 million new cases annually. Because of the slow growth rate of the causative agent Mycobacterium tuberculosis, isolation, identification, and drug susceptibility testing of this organism and other clinically important mycobacteria can take several weeks or longer. During the past several years, many molecular methods have been developed for direct detection, species identification, and drug susceptibility testing of mycobacteria. These methods can potentially reduce the diagnostic time from weeks to days. Currently, two nucleic acid amplification methods, the Enhanced Mycobacterium tuberculosis Direct Test (Gen-Probe) and the Amplicor Mycobacterium tuberculosis Test (Roche Diagnostic Systems), have been approved by the Food and Drug Administration for direct detection of M. tuberculosis from clinical specimens. PCR-based sequencing has become commonly used to identify many mycobacterial species. DNA probes have been widely used for species determination of the most commonly encountered mycobacteria. High-density oligonucleotide arrays (DNA microarrays) also have been applied to simultaneous species identification and detection of mutations that confer rifampin resistance in mycobacteria.

Drug Resistance, Microbial↗
PubMed2001

The contribution of ethnicity to Mycobacterium tuberculosis strain clustering.

OBJECTIVE: Descriptive study of molecular epidemiologic patterns of tuberculosis cases among ethnic minorities in Houston, Texas. DESIGN: Population-based, prospective, active surveillance, and molecular epidemiology study. PATIENTS: Tuberculosis cases reported to the City of Houston Tuberculosis Control Office between October 1995 and September 1998. RESULTS: During the study period, 1,139 culture-positive patients were enrolled for whom isolates of their culture specimen were available. Of these, 910 were part of an ethnic minority. Molecular characterization identified 689 of 1,139 isolates to be clonally related. Factors significantly associated with tuberculosis strain clustering in a multivariable logistic regression analysis were: birth in the United States, a history of homelessness, infection with the human immunodeficiency virus (HIV), pulmonary disease, infection with a tuberculosis strain from principal genetic group 1 or 3, living in a residence with five or more persons present, and use of public transportation more than once weekly. Asian ethnicity and increasing age were associated with decreased odds of clustering. CONCLUSIONS: Ethnicity was not a significant covariate for strain clustering after adjustments for factors related to socio-economic status.

Adult↗
PubMed2000

Epidemiologic differences between United States- and foreign-born tuberculosis patients in Houston, Texas.

The proportion of foreign-born tuberculosis patients in the United States is increasing. To analyze the epidemiology of tuberculosis in foreign-born people, culture-positive patients with tuberculosis in Houston, Texas, were interviewed from October 1995 through September 1998, and their isolates were molecularly characterized. Of the 1131 patients included in the study, 795 (70.3%) were US born and 336 (29.7%) were foreign born. The decrease in tuberculosis case rate among US-born people was 3.5 times that of foreign-born people. Significantly more US-born than foreign-born patients belonged to strain clusters (71.3% vs. 29.5%; P<.001). Risk factors associated with strain clustering were as follows: black ethnicity, low income, and homelessness in US-born patients and homelessness in foreign-born patients. Isolates from foreign-born patients were more likely to be resistant to >/=1 drug (15.4% vs. 8.4%; P=.001) and to be multidrug resistant (2.4% vs. 0.7%; P=.027) than isolates from US-born patients. These observations warrant increased emphasis on this distinct subpopulation of tuberculosis patients.

Adolescent↗
PubMed2000

Human immune response to streptococcal inhibitor of complement, a serotype M1 group A Streptococcus extracellular protein involved in epidemics.

Streptococcal inhibitor of complement (Sic) is a highly polymorphic extracellular protein made by serotype M1 group A Streptococcus strains that contributes to bacterial persistence in the mammalian upper respiratory tract. New variants of the Sic protein arise very rapidly by positive selection in human populations during M1 epidemics. The human antibody response to Sic was analyzed. Of 636 persons living in diverse localities, 43% had anti-Sic serum antibodies, but only 16.4% had anti-M1 protein serum antibody. Anti-Sic antibody was also present in nasal wash specimens in high frequency. Linear B cell epitope mapping showed that serum antibodies recognized epitopes located in structurally variable regions of Sic and the amino terminal hypervariable region of the M1 protein. Phage display analyses confirmed that the polymorphic regions of Sic are primary targets of host antibodies. These results support the hypothesis that selection of Sic variants occurs on mucosal surfaces by a mechanism that involves acquired host antibody.

Adolescent↗
PubMed2000

Selection of antibiotic-resistant bacterial mutants: allelic diversity among fluoroquinolone-resistant mutations.

To obtain a general framework for understanding selection of antibiotic-resistant mutants, allelic diversity was examined with about 600 fluoroquinolone-resistant mutants of mycobacteria. Selection at low fluoroquinolone concentration produced many low-level resistance mutants. Some of these contained mutations that conferred unselected antibiotic resistance; none contained alterations in the quinolone-resistance-determining region of the GyrA protein, the principal drug target. As selection pressure increased, a variety of GyrA variants became prevalent. High concentrations of antibiotic reduced the variety to a few types, and eventually a concentration was reached at which no mutant was recovered. That concentration defined a threshold for preventing the selection of resistance. The pattern of variants selected, which was also strongly influenced by antibiotic structure, readily explained the variants present in clinical isolates. Thus, resistance arises from selection of mutants whose identity depends on drug concentration and structure, both of which can be manipulated to restrict selection.

Alleles↗
PubMed2000

Crystal structure of the zymogen form of the group A Streptococcus virulence factor SpeB: an integrin-binding cysteine protease.

Pathogenic bacteria secrete protein toxins that weaken or disable their host, and thereby act as virulence factors. We have determined the crystal structure of streptococcal pyrogenic exotoxin B (SpeB), a cysteine protease that is a major virulence factor of the human pathogen Streptococcus pyogenes and participates in invasive disease episodes, including necrotizing fasciitis. The structure, determined for the 40-kDa precursor form of SpeB at 1.6-A resolution, reveals that the protein is a distant homologue of the papain superfamily that includes the mammalian cathepsins B, K, L, and S. Despite negligible sequence identity, the protease portion has the canonical papain fold, albeit with major loop insertions and deletions. The catalytic site differs from most other cysteine proteases in that it lacks the Asn residue of the Cys-His-Asn triad. The prosegment has a unique fold and inactivation mechanism that involves displacement of the catalytically essential His residue by a loop inserted into the active site. The structure also reveals the surface location of an integrin-binding Arg-Gly-Asp (RGD) motif that is a feature unique to SpeB among cysteine proteases and is linked to the pathogenesis of the most invasive strains of S. pyogenes.

Bacterial Proteins↗
PubMed2000

Complete nucleotide sequence and genomic structure of the human NRAMP1 gene region on chromosome region 2q35.

Several lines of independent evidence suggest that human Natural Resistance Associated Macrophage Protein 1 gene (NRAMP1) is an important regulator of susceptibility to infectious diseases caused by certain intracellular pathogens. Here, we report the nucleotide sequence of 32198 bp of genomic DNA overlapping NRAMP1 on chromosomal region 2q35. The NRAMP1 gene spans 13604 bp. The gene and its 5' genomic region are highly enriched for DNA repeat sequences. A second gene was identified in the immediate vicinity of NRAMP1 and was tentatively named Nuclear LIM Interactor-Interacting Factor (NLI-IF) by analogy to its closest ortholog. The human NLI-IF gene begins 4721 bp downstream of the NRAMP1 stop codon and is composed of seven exons varying in size from 57 bp to 1644 bp. The gene gives rise to a 2655-bp mRNA transcript that contains a 783-bp open reading frame. The predicted molecular weight of the 261-amino acid NLI-IF protein is 29.2 kDa. Several putative gene regulatory elements were identified in the 5' upstream region of NLI-IF, including consensus binding sequences for Sp1, AP-2, NF-kappa B, and PU 1. The NLI-IF amino acid sequence has homology to proteins that have a high degree of homology with the NLI-interacting factor from Gallus gallus and are found in divergent species ranging from yeast to plants. NLI-IF is part of a human gene family encoding four related proteins of unknown function. Northern blot analysis of 15 different human tissues revealed a 2.6-kb NLI-IF mRNA that was ubiquitously expressed, but at varying levels. A second transcript with estimated size of 7 kb was expressed only in the placenta. Our data provide new sequence information about the NRAMP1 gene region that will be useful in the search for genetic variants causally involved in altered susceptibility to infectious diseases.

Amino Acid Sequence↗
PubMed2000

Genetic diversity and evidence for acquired antimicrobial resistance in Mycobacterium tuberculosis at a large hospital in South India.

OBJECTIVE: To assess genetic diversity and drug resistance of Mycobacterium tuberculosis isolates collected at Christian Medical College Hospital (CMCH), Vellore, India, between July 1995 and May 1996. MATERIALS AND METHODS: Isolates were subjected to IS6110-based restriction fragment length polymorphism (RFLP) analysis and tested for resistance to isoniazid, rifampin, ethambutol, streptomycin, and pyrazinamide, and DNA from selected strains was sequenced in regions associated with drug resistance. RESULTS: One hundred and one M. tuberculosis isolates were collected from 87 patients with pulmonary tuberculosis. Charts of 69 patients were reviewed for history of tuberculosis illness and treatment. DNA from 29 strains was sequenced in katG, rpoB, and gyrA, and sometimes pncA regions. Analysis by RFLP revealed a high degree of genetic diversity, with no identifiable clusters of infection. Of the strains tested, 51% were resistant to at least one antibiotic, and 43% were resistant to more than one drug. There was a high rate of resistance observed in patients whose charts indicated a history of improperly administered tuberculosis treatment, whereas little drug resistance was observed in patients never previously treated for tuberculosis. Sequencing of genes associated with drug resistance revealed several previously unreported mutations in resistant strains. CONCLUSIONS: This analysis suggests that the cases of tuberculosis in the sample are largely reactivation of long-standing infections and that the drug resistance among patients in CMCH is largely acquired or secondary rather than attributable to the spread of drug-resistant strains.

Antitubercular Agents↗
PubMed2000

Invasive group A streptococcal disease in the Netherlands: evidence for a protective role of anti-exotoxin A antibodies.

As part of a nationwide surveillance in The Netherlands during 1994-1997, 53 patients with invasive group A streptococcal (GAS) infections were evaluated for medical history, symptoms, and outcome. Patients' isolates were tested for the production of pyrogenic exotoxins A (SPE-A) and B (SPE-B). Acute-phase sera from all patients and convalescent sera from 12 patients were investigated for the presence of antibodies against SPE-A and SPE-B. Twenty-three patients developed toxic shock-like syndrome and 16 died. Absence of antibodies against SPE-A and/or SPE-B was a risk factor for developing invasive streptococcal disease. Toxic shock and mortality were associated with a lack of anti-SPE-A antibodies (P<.025). Anti-SPE-A antibodies were found in convalescent sera from all patients infected by speA-positive isolates. Virtually all invasive speA-positive streptococci expressed SPE-A protein in vitro. Thus antibodies against SPE-A appeared vital for mediating the outcome of invasive GAS disease in this population.

Adolescent↗
PubMed2000

Negligible genetic diversity of mycobacterium tuberculosis host immune system protein targets: evidence of limited selective pressure.

A common theme in medical microbiology is that the amount of amino acid sequence variation in proteins that are targets of the host immune system greatly exceeds that found in metabolic enzymes or other housekeeping proteins. Twenty-four Mycobacterium tuberculosis genes coding for targets of the host immune system were sequenced in 16 strains representing the breadth of genomic diversity in the species. Of the 24 genes, 19 were invariant and only six polymorphic nucleotide sites were identified in the 5 genes that did have variation. The results document the highly unusual circumstance that prominent M. tuberculosis antigenic proteins have negligible structural variation worldwide. The data are best explained by a combination of three factors: (i) evolutionarily recent global dissemination in humans, (ii) lengthy intracellular quiescence, and (iii) active replication in relatively few fully immunocompetent hosts. The very low level of amino acid diversity in antigenic proteins may be cause for optimism in the difficult fight to control global tuberculosis.

Acyltransferases↗
PubMed2000

Molecular genetic analysis of nucleotide polymorphisms associated with ethambutol resistance in human isolates of Mycobacterium tuberculosis.

Ethambutol (EMB) is a central component of drug regimens used worldwide for the treatment of tuberculosis. To gain insight into the molecular genetic basis of EMB resistance, approximately 2 Mb of five chromosomal regions with 12 genes in 75 epidemiologically unassociated EMB-resistant and 33 EMB-susceptible Mycobacterium tuberculosis strains isolated from human patients were sequenced. Seventy-six percent of EMB-resistant organisms had an amino acid replacement or other molecular change not found in EMB-susceptible strains. Thirty-eight (51%) EMB-resistant isolates had a resistance-associated mutation in only 1 of the 12 genes sequenced. Nineteen EMB-resistant isolates had resistance-associated nucleotide changes that conferred amino acid replacements or upstream potential regulatory region mutations in two or more genes. Most isolates (68%) with resistance-associated mutations in a single gene had nucleotide changes in embB, a gene encoding an arabinosyltransferase involved in cell wall biosynthesis. The majority of these mutations resulted in amino acid replacements at position 306 or 406 of EmbB. Resistance-associated mutations were also identified in several genes recently shown to be upregulated in response to exposure of M. tuberculosis to EMB in vitro, including genes in the iniA operon. Approximately one-fourth of the organisms studied lacked mutations inferred to participate in EMB resistance, a result indicating that one or more genes that mediate resistance to this drug remain to be discovered. Taken together, the results indicate that there are multiple molecular pathways to the EMB resistance phenotype.

Antitubercular Agents↗