Biomedical subjects

B Beall

Publications and source records attributed to B Beall.

At least 19 recordsLinked to original sources

PubMed2003

Evaluation of synthetic, M type-specific peptides as antigens in a multivalent group A streptococcal vaccine.

The recent development of emm gene sequence-based typing methodology has allowed group A streptococci (GAS) M serotype prevalence data to be determined. This information has been used to identify the components of a multivalent M protein peptide vaccine that could theoretically prevent most of the GAS-mediated diseases in the USA. In this study, we have evaluated in mice the immunogenicity and protective ability of multiple synthetic, M type-specific peptides, derived from the N-termini of three prevalent GAS serotypes (three peptides per serotype, total of nine peptides). At least one peptide, representing each of the three M types tested, was immunogenic. Five of the nine synthetic peptides tested, elicited an immune response in mice, and sera raised against four of the peptides, all possessed functional activity as demonstrated in a bactericidal assay. In vivo nasopharyngeal challenge experiments were carried out with peptides from the M1 (peptide M1-3) and M3 (peptide M3-2) proteins induced in vivo immune protection by reducing intranasal carriage. Reduction in colonization for M1-3 and M3-2 was 90% (P=0.02) and 66% (P<0.17), respectively. A reduction in colonization of 67% (P=0.03) was observed for M3-2 immunized mice when M43, a heterologous serotype, was used as the challenge strain. These results show the utility of synthetic, M type-specific peptides as antigens in a multivalent GAS vaccine.

Administration, Intranasal↗

PubMed2003

Epidemiologic analysis of invasive and noninvasive group a streptococcal isolates in Hong Kong.

Since the mid-1980s, there has been a resurgence of severe forms of invasive group A streptococcal (GAS) disease in many Western countries. In Hong Kong, a similar increase has also been observed in recent years. One hundred seven GAS isolates collected from 1995 to 1998 from individuals with necrotizing fasciitis, toxic shock syndrome, meningitis, or other type of bacteremic sepsis (invasive group, n = 24) as well as from individuals with minor skin and throat infections (noninvasive group, n = 83) were characterized through serologic and/or emm sequence typing. Thirty-two M protein gene sequence types were identified. Types M1, M4, and M12 were the most prevalent in both the invasive group and the noninvasive group; together they accounted for 70.8 and 37.3% of the isolates, respectively. No clear pattern of skin and throat infection M types was observed. Type M1 was overrepresented in the invasive and pharyngeal isolates. The same pulsed-field gel electrophoresis pattern was shared by most invasive and all pharyngeal M1 isolates. Overall, resistance to erythromycin (32%) and tetracycline (53%) was high, but M1 isolates were significantly less likely to have resistance to either antimicrobial agent than non-M1 isolates. One novel emm sequence type, stHK, was identified in an isolate from a patient with necrotizing fasciitis. Minor emm gene sequence alterations were noted for 31 isolates, and for 13 of these isolates, deletion, insertion, or point mutations were seen in the hypervariable 50 N-terminal residues.

Amino Acid Sequence↗

PubMed2001

Fesselin, a synaptopodin-like protein, stimulates actin nucleation and polymerization.

Fesselin is a proline-rich actin binding protein that has recently been isolated from smooth muscle [Leinweber, B. D., Fredricksen, R. S., Hoffman, D. R., and Chalovich, J. M. (1999) J. Muscle Res. Cell Motil. 20, 539-545]. Fesselin is similar to synaptopodin [Mundel, P., Heid, H. W., Mundel, T. M., Krüger, M., Reiser, J., and Kriz, W. (1997) J. Cell Biol. 139, 193-204] in terms of its size, isoelectric point, and sequence although synaptopodin is not present in smooth muscle. The function of fesselin is unknown. Evidence is presented here that fesselin accelerates the polymerization of actin. Fesselin was effective on actin isolated from either smooth or skeletal muscle at low ionic strength and in the presence of 100 mM KCl. At low ionic strength, fesselin decreased the time for 50% polymerization to about 1% of that in the absence of fesselin. The lag phase characteristic of the slow nucleation process of polymerization was eliminated as the fesselin concentration was increased from very low levels. Fesselin did not alter the critical concentration for actin but did increase the rate of elongation by approximately 3-fold. The increase in elongation rate constant is insufficient to account for the total increase in polymerization rate. It is likely that fesselin stabilizes the formation of actin nuclei. Time courses of actin polymerization at varied fesselin concentrations and varied actin concentrations were simulated by increasing the rate of nucleation and both the forward and reverse rate constants for elongation.

Actins↗

PubMed2001

Necrotizing fasciitis due to penicillin-resistant Streptococcus pneumoniae: case report and review of the literature.

Necrotizing fasciitis (NF) is a life-threatening infection involving rapid necrosis of subcutaneous and fascial tissues. Streptococcus pneumoniae (SPN) soft tissue infection is exceedingly uncommon, reported primarily in patients with immunosuppression or other underlying conditions. We report a case of NF and septic shock in a healthy 32-year-old man, whose only predisposing factor was antecedent blunt trauma. Pathological examination and culture of the extensive tissue debridement were positive only for SPN. The serotype 9V isolate was penicillin (PCN)-resistant (MIC=2.0), and closely-related by pulse field gel electrophoresis and multilocus fingerprinting to clone France 9V-3, an important genetic reservoir for increasing PCN-resistance worldwide. This unique case has implications for our pathogenic under-standing and empiric management of NF.

Adult↗

PubMed2001

Group A streptococcal genotypes from pediatric throat isolates in Rome, Italy.

In a study assessing genetic diversity, 114 group A streptococcus (GAS) isolates were recovered from pediatric pharyngitis patients in Rome, Italy. These isolates comprised 22 different M protein gene (emm) sequence types, 14 of which were associated with a distinct serum opacity factor/fibronectin binding protein gene (sof) sequence type. Isolates with the same emm gene sequence type generally shared a highly conserved chromosomal macrorestriction profile. In three instances, isolates with dissimilar macrorestriction profiles had identical emm types; in each of these cases multilocus sequence typing revealed that isolates with the same emm type were clones having the same allelic profiles. Ninety-eight percent of the pharyngeal isolates had emm types previously found to be highly associated with mga locus gene patterns commonly found in pharyngeal GAS isolates.

Adolescent↗

PubMed2001

Genetic and phenotypic features of Streptococcus pyogenes strains isolated in Brazil that harbor new emm sequences.

In the present study, 37 group A Streptococcus (GAS) strains belonging to 13 new emm sequence types identified among GAS strains randomly isolated in Brazil were characterized by using phenotypic and genotypic methods. The new types were designated st204, st211, st213, st809, st833, st854, st2904, st2911, st2917, st2926, st3757, st3765, and st6735. All isolates were susceptible to the antimicrobial agents tested, except to tetracycline. They all carried the speB gene, and 94.6% produced detectable SpeB. Most strains belonging to a given emm type had similar or highly related pulsed-field gel electrophoresis profiles that were distinct from profiles of strains of another type. The other characteristics were variable from isolate to isolate, although some associations were consistently found within some emm types. Unlike the other isolates, all type st213 isolates were speA positive and produced SpeA. Strains belonging to st3765 were T6 and opacity factor (OF) negative. Individual isolates within OF-positive emm types were associated with unique sof gene sequence types, while OF-negative isolates were sof negative by PCR. This report provides information on new emm sequence types first detected in GAS isolates from a geographic area not extensively surveyed. Such data can contribute to a better understanding of the local and global dynamics of GAS populations and of the epidemiological aspects of GAS infections occurring in tropical regions.

Antigens, Bacterial↗

PubMed2000

Contrasting molecular epidemiology of group A streptococci causing tropical and nontropical infections of the skin and throat.

Disease caused by group A streptococci (GAS) in tropical regions often takes the form of impetigo, whereas pharyngitis tends to predominate in temperate zones. GAS derived from asymptomatic throat infections and pyoderma lesions of rural Aboriginal Australians were evaluated for phylogenetic distant emm genes, which represent ecological markers for tissue site preference. On the basis of the percentage of total isolates from a given tissue, emm pattern A-C organisms exhibited a stronger predilection for the throat, whereas pattern D organisms preferred the skin. Only 16% of isolates collected by active surveillance displayed pattern A-C, which reflects the low incidence of oropharyngeal infection. Importantly, most (70%) pattern A-C organisms were isolated from skin sores, despite their innate tendency to infect the throat. Combined with findings from nontropical populations, analysis of the data supports the hypothesis that GAS tissue preferences are genetically predetermined and that host risk factors for infection strongly influence the differential reproduction of individual clones.

Adult↗

PubMed2000

Major related sets of antibiotic-resistant Pneumococci in the United States as determined by pulsed-field gel electrophoresis and pbp1a-pbp2b-pbp2x-dhf restriction profiles.

To assess the genetic diversity of pneumococci causing serious disease within the United States, restriction profiles of 3 penicillin-binding protein (PBP)-gene amplicons and the dhf amplicon were examined in 241 recent sterile-site isolates from 7 population centers. This analysis provided markers useful for epidemiologic studies and was generally predictive of resistances to beta-lactam antibiotics and trimethoprim-sulfamethoxazole. Eight pulsed-field gel electrophoresis (PFGE) types, each representing 3-40 isolates, accounted for 134 of the 144 beta-lactam-resistant pneumococci (MICs >/=1 microgram/mL for penicillin, cefotaxime, or both). Five of these PFGE types contained subtypes highly related to subtypes of previously characterized pneumococcal clones. Within 4 of these PFGE types, the major composite PBP gene-dhf profile was highly related to the composite profile from the previously characterized related clone. Eight capsular serotypes were found among the 144 beta-lactam-resistant pneumococci. Divergent capsular types among isolates with identical PBP gene-dhf profiles and related PFGE types indicated several instances of capsular serotype switching.

Amino Acid Sequence↗

PubMed2000

Impact of azithromycin on oropharyngeal carriage of group A Streptococcus and nasopharyngeal carriage of macrolide-resistant Streptococcus pneumoniae.

BACKGROUND: Invasive group A streptococcal (GAS) infections are a cause of serious morbidity and high mortality. There is a need for a simple, effective antimicrobial regimen that could be used to prevent invasive GAS disease in high risk situations. To assess azithromycin as a chemoprophylactic agent, we evaluated its efficacy for eradication of oropharyngeal (OP) GAS and its impact on the nasopharyngeal (NP) colonization rate of macrolide-resistant Streptococcus pneumoniae. METHODS: We obtained OP and NP swabs for GAS and pneumococcus culture, respectively, from 300 schoolmates of a child with an invasive GAS infection. GAS culture-positive students were treated with daily azithromycin (12 mg/kg/day) for 5 days. We obtained follow-up OP and NP swabs at 9 (Day 17) and 24 (Day 32) days post-treatment from those students identified as GAS carriers on Day 0 and determined macrolide susceptibility of GAS and pneumococcal isolates. RESULTS: Of the 300 students swabbed 152 (50%) carried GAS in their oropharynx. On Day 17, efficacy of azithromycin for GAS eradication was 95% (140 of 147) for all students. NP colonization rates for pneumococci decreased from 46% (67 of 146) to 12% (17 of 144; P < 0.001) by Day 17 and to 20% (27 of 137; P < 0.001) by Day 32. The prevalence of erythromycin-resistant pneumococcal isolates increased from 2% (3 of 146) to 4% (6 of 144) by Day 17 and to 8% (11 of 137; P = 0.04) by Day 32. CONCLUSIONS: Azithromycin is an effective short course regimen for eradication of oropharyngeal GAS. However, azithromycin selected for macrolide-resistant strains of pneumococci. These findings highlight the importance of determining the appropriate circumstances for antimicrobial prophylaxis to prevent invasive GAS infections.

Anti-Bacterial Agents↗

PubMed2000

An outbreak of skin sepsis in abattoir workers caused by an 'unusual' strain of Streptococcus pyogenes.

An outbreak of indolent skin infections due to an 'unusual' serological type of Streptococcus pyogenes that lasted for 3 months and affected eight workers in an abattoir is described. The group A streptococcal (GAS) isolates were serotyped as M-type 59; however, they possessed a T-protein pattern (T5/27/44) that is not commonly associated with M-type 59. Further genotypic characterisation studies revealed that all eight isolates were indistinguishable by pulsed-field gel electrophoresis (PFGE) and possessed the emm gene encoding for the M-type 59. Once identified, and after a combination of penicillin treatment, exclusion of workers with lesions and reinforcement of standard hygiene precautions, no further cases developed. Although common in the 1970s and 1980s, streptococcal infections in this situation are now reported infrequently. This report serves to highlight the issues surrounding working practices in abattoirs.

Abattoirs↗

PubMed2000

Limiting the spread of resistant pneumococci: biological and epidemiologic evidence for the effectiveness of alternative interventions.

Streptococcus pneumoniae infections are a leading cause of respiratory illness in young children, the elderly, and persons with chronic medical conditions. The emergence of multidrug-resistant pneumococci has compromised the effectiveness of antibiotic therapy for pneumococcal infections. As antibiotic-resistant strains increase in prevalence, there is a need for interventions that minimize the spread of resistant pneumococci. In this review we provide a framework for understanding the spread of pneumococcal resistance and evaluate proposed interventions to reduce this spread. Pneumococci differ from many drug-resistant pathogens because asymptomatic carriers play a key role in transmission of resistant strains and the genes encoding resistance are spread primarily by transformation and conjugative transposons. Evidence suggests that modifications of treatment regimens that have proved effective at limiting resistance in other pathogens may not prevent the spread of pneumococcal resistance. In contrast, programs encouraging more judicious antibiotic use have been shown to be effective. Additionally, a newly developed conjugate pneumococcal vaccine holds great potential as an "antiresistance vaccine" that simultaneously reduces the burden of invasive disease and the prevalence of resistant strains. Several areas of future epidemiologic and laboratory research hold promise to contribute to the reduced spread of pneumococcal resistance.

Anti-Bacterial Agents↗

PubMed2000

Genetic locus for streptolysin S production by group A streptococcus.

Group A streptococcus (GAS) is an important human pathogen that causes pharyngitis and invasive infections, including necrotizing fasciitis. Streptolysin S (SLS) is the cytolytic factor that creates the zone of beta-hemolysis surrounding GAS colonies grown on blood agar. We recently reported the discovery of a potential genetic determinant involved in SLS production, sagA, encoding a small peptide of 53 amino acids (S. D. Betschel, S. M. Borgia, N. L. Barg, D. E. Low, and J. C. De Azavedo, Infect. Immun. 66:1671-1679, 1998). Using transposon mutagenesis, chromosomal walking steps, and data from the GAS genome sequencing project (www.genome.ou.edu/strep. html), we have now identified a contiguous nine-gene locus (sagA to sagI) involved in SLS production. The sag locus is conserved among GAS strains regardless of M protein type. Targeted plasmid integrational mutagenesis of each gene in the sag operon resulted in an SLS-negative phenotype. Targeted integrations (i) upstream of the sagA promoter and (ii) downstream of a terminator sequence after sagI did not affect SLS production, establishing the functional boundaries of the operon. A rho-independent terminator sequence between sagA and sagB appears to regulate the amount of sagA transcript produced versus transcript for the entire operon. Reintroduction of the nine-gene sag locus on a plasmid vector restored SLS activity to the nonhemolytic sagA knockout mutant. Finally, heterologous expression of the intact sag operon conferred the SLS beta-hemolytic phenotype to the nonhemolytic Lactococcus lactis. We conclude that gene products of the GAS sag operon are both necessary and sufficient for SLS production. Sequence homologies of sag operon gene products suggest that SLS is related to the bacteriocin family of microbial toxins.

Amino Acid Sequence↗

PubMed2000

Pneumococcal pspA sequence types of prevalent multiresistant pneumococcal strains in the United States and of internationally disseminated clones.

In a recent genotypic survey of beta-lactam-resistant pneumococci recovered in different areas of United States during 1997, eight clonal types that each represented 3 to 40 isolates accounted for 134 of 144 isolates (G. Gherardi, C. Whitney, R. Facklam, and B. Beall, J. Infect. Dis. 181:216-229, 2000). We determined the degree of pspA gene diversity among these 134 isolates and for 11 previously characterized internationally disseminated multiresistant strains. Thirty-four different pspA restriction profiles were determined for an amplicon encompassing the variable portion of the structural gene that encodes the surface-exposed domain of PspA and a variable-length proline-rich putative cell wall-associated domain. These restriction profiles closely correlated with those of 33 different pspA sequence types of an approximately 230-residue region corresponding to residues 182 to 410 of the strain Rx1 PspA. These residues encompass a 100-residue clade-defining region known to contain cross-protective epitopes for which 17 sequence types were found. Distinct, conserved pspA sequence types were found for the majority of strains within seven of the eight U.S. clonal types assessed, while one pulsed-field gel electrophoresis type was represented by isolates of three distinct PspA clades. Sequence typing of pspA provides an added level of specificity in the subtyping of isolates and is a necessary first step in determining the components needed in a PspA vaccine which could elicit effective cross-protective coverage.

Amino Acid Sequence↗

PubMed2000

Analysis of immunoreactivity to a Streptococcus equi subsp. zooepidemicus M-like protein To confirm an outbreak of poststreptococcal glomerulonephritis, and sequences of M-like proteins from isolates obtained from different host species.

The etiologic agent of a large 1998 outbreak of poststreptococcal acute glomerulonephritis (PSGN) in Nova Serrana, Brazil, was found likely to be a specific strain of Streptococcus equi subsp. zooepidemicus from contaminated cheese (S. Balter et al., Lancet 355:1776-1780, 2000). In the present study, we used a serologic screen for a known surface-exposed virulence factor to confirm the epidemiologic findings. Using primers flanking a previously characterized M-like protein gene (J. F. Timoney et al., Infect. Immun. 63:1440-1445, 1995), we amplified and sequenced the M-like protein (designated Szp5058) gene and found it to be identical among four independent acute-phase PSGN patient isolates. Convalescent-phase sera from 33 of 44 patients in the PSGN outbreak were found to contain antibodies highly reactive to a purified Szp5058 fusion protein, compared with 1 of 17 control sera (P < 0. 0001), suggesting that Szp5058 was expressed during infection and further implicating this strain as the cause of the PSGN outbreak. The predicted signal sequence and cell wall association motif of Szp5058 were highly conserved with the corresponding sequence from S. equi subsp. zooepidemicus SzpW60, while the predicted surface-exposed portions differed markedly between these two proteins. The 5' end of the szp5058 gene, including its variable region, was identical to the szp gene from another strain associated with a previous PSGN outbreak in England (M. Barham et al., Lancet i:945-948, 1983), and the corresponding szp sequence found from the Lancefield group C type strain isolated from a guinea pig. In addition, the hypervariable (HV) portion of szp5058 was identical to a previously published HV sequence from a horse isolate (J. A. Walker and J. F. Timoney, Am. J. Vet. Res. 59:1129-1133, 1998). Three other strains of S. equi subsp. zooepidemicus, including another strain previously associated with a PSGN outbreak, were each found to contain a distinct szp gene. Two of these szp genes had HV regions identical to szp regions from isolates recovered from different host species.

Amino Acid Sequence↗

PubMed1999

Genetic linkage of exotoxin alleles and emm gene markers for tissue tropism in group A streptococci.

In group A streptococci, genetic markers for principal tissue reservoir are located within emm genes, which encode surface proteins that have a role in virulence. A worldwide collection of 160 isolates was evaluated for two traits: chromosomal emm gene markers for tissue tropism (designated patterns A-E), and bacteriophage-associated genes (speA and speC) encoding pyrogenic exotoxins. The speA and speC alleles of organisms harboring the emm marker for a pharyngeal reservoir (pattern A-C) differ from spe alleles that predominate in organisms with the emm marker for impetigo (pattern D). However, organisms that display the emm marker for both tissue sites (pattern E) are not intermediate for the distribution of either speA or speC alleles, but instead resemble pattern A-C isolates for speA and pattern D strains for speC. Statistically significant nonrandom associations between exotoxin alleles and emm patterns were observed but cannot be readily explained by niche separation alone.

Alleles↗

PubMed1999

Genotypic survey of recent beta-lactam-resistant pneumococcal nasopharyngeal isolates from asymptomatic children in Chile.

To assess pneumococcal strain variability among young asymptomatic carriers in Chile, we used serotyping, antibiotic susceptibility testing, and genotyping to analyze 68 multidrug-resistant pneumococcal isolates recovered from 54 asymptomatic children 6 to 48 months of age. The isolates represented capsular serotypes 19F (43 isolates), 14 (14 isolates), 23F (7 isolates), 6B (3 isolates), and 6A (1 isolate). Genotypic analysis, which included pulsed-field gel electrophoresis (PFGE) of chromosomal digests, penicillin binding protein (PBP) gene fingerprinting, and dhf gene fingerprinting, revealed that the isolates represented six different genetic lineages. Clear circumstantial evidence of capsular switching was seen within each of four of the genetically related sets. The majority of the isolates, consisting of the 43 19F isolates and 2 type 6B isolates, appeared to represent a genetically highly related set distinct from previously characterized pneumococcal strains. Each of three other genetically defined lineages was closely related to one of the previously characterized clones Spain(6B)-2, France(9V)-3, or Spain(23F)-1. A fifth lineage was comprised of four type 23F isolates that, by the techniques used for this study, were genetically indistinguishable from three recent type 19F sterile-site isolates from the United States. Finally, a sixth lineage was represented by a single type 23F isolate which had a unique PFGE type and unique PBP and dhf gene fingerprints.

Base Sequence↗

PubMed1998

Two iron-regulated putative ferric siderophore receptor genes in Bordetella bronchiseptica and Bordetella pertussis.

Two iron-regulated genes with deduced homology to TonB-dependent ferric siderophore receptors were cloned from Bordetella bronchiseptica by screening a library of TnphoA insertion mutants. bfrB and bfrC were iron-repressed in B. bronchiseptica by a Fur-dependent mechanism, and were expressed from promoters overlapped by potential Fur-binding sites. Both genes were highly conserved among Bordetella species and were also iron-regulated in Bordetella pertussis. bfrB and bfrC mutants of both species and a bfrB-bfrC double mutant of B. bronchiseptica had no discernible defects in utilization of known iron sources for Bordetella.

Alkaline Phosphatase↗

PubMed1998

Invasive group A streptococcal disease in metropolitan Atlanta: a population-based assessment.

Active, population-based surveillance for invasive group A streptococcal (GAS) disease was conducted in laboratories in metropolitan Atlanta from 1 January 1994 through 30 June 1995. Clinical and laboratory records were reviewed and isolates characterized. One hundred and eighty-three cases of invasive GAS disease were identified (annual incidence, 5.2 cases/100,000). The incidence was highest among blacks (9.7/100,000 per year; relative risk (RR), 1.92; confidence interval (CI), 1.69-2.19; P < .0001) and the elderly, particularly nursing home residents (RR, 13.66; CI, 7.07-26.40; P < .0001). The mean age of patients was 41.3 years (range, 0-95 years). Skin and soft-tissue infections were most common. Mortality was 14.4%; risk of death was significantly higher for patients with streptococcal toxic shock syndrome (STSS) (RR, 9.73; CI, 3.34-29; P = .0008) and individuals infected with M-type 1 (RR, 7.40; CI, 1.5-16; P = .0084). Fourteen percent of invasive GAS infections were STSS and 3% were necrotizing fasciitis. Invasive GAS disease was associated with varicella infection in children (RR, 12.19; CI, 5.58-26.62; P < .0001). M (or emm) types included M1 (16%), M12 (12%), and M3 (11%). Continued study of GAS disease is essential to further define risk factors and risk of secondary cases and to develop effective prevention strategies.

Adolescent↗