Haemophilus influenzae: genetic variability and natural selection to identify virulence factors.
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Evolution, Molecular↗
Biomedical subjects
Carl F Marrs
Publications and source records attributed to Carl F Marrs.
Comparison of DNA dot blot hybridization and lancefield capillary precipitin methods for group B streptococcal capsular typing.
Group B streptococci (GBS) (Streptococcus agalactiae) are a major cause of sepsis and meningitis in neonates and infants and of invasive disease in pregnant women, nonpregnant, presumably immunocompromised adults, and the elderly. Nine GBS serotypes based on capsular polysaccharide antigens have been described. The serotype distributions among invasive and colonizing isolates differ between pediatric and adult populations and have changed over time. Thus, periodic monitoring of GBS serotype distributions is necessary to ensure the proper formulation and application of an appropriate GBS vaccine for human use and to detect the emergence of novel serotypes. Since the mid-1990s, the proportion of GBS isolates that are nontypeable by standard serologic methods has increased, creating a need for more sensitive typing methods. We describe a typing method that uses DNA dot blot hybridization with probes generated by PCR from the GBS capsular genes for serotypes Ia, Ib, and II to VIII. PCR primers were designed to amplify type-specific GBS capsular gene sequences. Gene probes were constructed from the PCR products and used to classify isolates based on hybridization profiles. A total of 306 previously serotyped invasive and colonizing isolates were used to compare our dot blot capsular typing (DBCT) identification method with Lancefield serotyping (LS). A dot blot capsular type was assigned to 99% (303 of 306) of the isolates, whereas 273 of 306 isolates (89%) were assigned a Lancefield serotype. The overall agreement between the methods was 95% (256 of 270 isolates typeable by both methods). We conclude that the DBCT method is a specific and useful alternative to the commonly used LS method.
Bacterial Capsules↗
Prevalence of the hifBC, hmw1A, hmw2A, hmwC, and hia Genes in Haemophilus influenzae Isolates.
Adherence of Haemophilus influenzae to respiratory epithelial cells is the first step in the pathogenesis of H. influenzae infection and is facilitated by the action of several adhesins located on the surface of the bacteria. In this study, prevalences of hifBC, which represent the pilus gene cluster; hmw1A, hmw2A, and hmwC, which represent high-molecular-weight (HMW) adhesin genes; and hia, which represents H. influenzae adhesin (Hia) genes were determined among clinical isolates of encapsulated type b (Hib) and nonencapsulated (NTHi) H. influenzae. hifBC genes were detected in 109 of 170 (64%) Hib strains and in 46 of 162 (28%) NTHi isolates (P = 0.0001) and were more prevalent among the invasive type b strains than invasive NTHi strains (P = 0.00003). Furthermore, hifBC genes were significantly more prevalent (P = 0.0398) among NTHi throat isolates than NTHi middle ear isolates. hmw1A, hmw2A, hmwC, and hia genes were not detected in Hib strains. Among NTHi isolates, the prevalence of hmw1A was 51%, the prevalence of hmw2A was 23%, the prevalence of hmwC was 48%, and the prevalence of hia was 33%. The hmw genes were significantly more prevalent among middle ear than throat isolates, while hia did not segregate with a respiratory tract site. These results show the variability of the presence of adhesin genes among clinical H. influenzae isolates and suggest that hemagglutinating pili may play a larger role in H. influenzae nasopharyngeal colonization than in acute otitis media whereas the HMW adhesins may be virulence factors for acute otitis media.
Adhesins, Bacterial↗
Identification of risk factors for extrapulmonary tuberculosis.
The proportion of extrapulmonary tuberculosis cases in the United States has increased from 16% of tuberculosis cases, in 1991, to 20%, in 2001. To determine associations between the demographic, clinical, and life style characteristics of patients with tuberculosis and the occurrence of extrapulmonary tuberculosis, a retrospective case-control study was conducted. This study included 705 patients with tuberculosis, representing 98% of the culture-proven cases of tuberculosis in Arkansas from 1 January 1996 through 31 December 2000. A comparison between 85 patients with extrapulmonary tuberculosis (case patients) and 620 patients with pulmonary tuberculosis (control patients) showed women (OR, 1.98; 95% CI, 1.25-3.13), non-Hispanic blacks (OR, 2.38; 95% CI, 1.42-3.97), and HIV-positive persons (OR, 4.93; 95% CI, 1.95-12.46) to have a significantly higher risk for extrapulmonary tuberculosis than men, non-Hispanic whites, and HIV-negative persons. This study expands the knowledge base regarding the epidemiology of extrapulmonary tuberculosis and enhances our understanding of the relative contribution of host-related factors to the pathogenesis of tuberculosis.
Adolescent↗
Identification of a gene encoding heat-resistant agglutinin in Escherichia coli as a putative virulence factor in urinary tract infection.
Escherichia coli causes the vast majority of urinary tract infections (UTI) in both ambulatory and hospital patients. Several uropathogenic virulence factors have been identified, but half of all E. coli isolates that cause UTI have none or only one of the known virulence factors. Thus, it is reasonable to presume that other bacterial factors may be important in UTI pathogenesis. In order to find additional uropathogenic E. coli genes, we used genomic subtraction to identify DNA regions present in a uropathogenic strain of E. coli (1128-11). Genomic subtraction yielded 40 tester-specific fragments, including a novel heat-resistant agglutinin (hra) gene fragment. hra occurred in 55% of 486 UTI strains compared to 28% of 165 rectal strains (P = 0.001). The hra gene in 1128-11 was cloned, sequenced, and found to have 91% homology to the hra gene from E. coli meningitis strain RS218. The genetic organization of genes flanking hra in 1128-11 is distinct from the hra found in E. coli strains J96 and RS218. In our UTI and rectal specimen collections, hra was positively associated with a number of known virulence genes, including pathogenicity island genes hly and cnf, which are absent in 1128-11. The presence of hra in 1128-11 independent of hly/cnf suggests multiple mechanisms by which hra can be acquired by pathogenic E. coli strains. The flanking genes suggest that in 1128-11, hra may be part of a novel variant of a pathogenicity island V.
Adhesins, Bacterial↗
Evaluation of genotyping large numbers of Escherichia coli isolates by enterobacterial repetitive intergenic consensus-PCR.
We analyzed a large collection of Escherichia coli isolates typed by enterobacterial repetitive intergenic consensus (ERIC)-PCR with BioNumerics gel analysis software. However, the interexperimental variation of ERIC-PCR caused the computer software to classify repeated isolates as different. ERIC-PCR should not be used as the sole determinant of genetic similarity when typing large numbers of bacterial isolates via computer software.
Base Sequence↗
Uropathogenic Escherichia coli are more likely than commensal E. coli to be shared between heterosexual sex partners.
Because uropathogenic Escherichia coli are better adapted than other E. coli to the urethra, periurethra, and vagina, the authors reasoned that uropathogenic E. coli would be more likely than commensal E. coli to be shared between sex partners. In this 1996-1999 Michigan study, the genetic identity of E. coli isolated from 166 women with E. coli urinary tract infection (UTI) and 94 women without UTI and their sex partners was determined by pulsed-field gel electrophoresis. Rectal isolates were considered uropathogenic E. coli if genetically identical to the urinary isolate causing UTI. All eight urinary isolates from men with UTI partners were identical to the E. coli found in the urine or vagina of their sex partner. When the 550 unique rectal E. coli isolates from couples were considered the unit of analysis, E. coli that caused UTI were nine times (odds ratio (OR) = 8.87, 95% confidence interval (CI): 5.41, 14.54) more likely than other E. coli to be shared between sex partners. Sharing occurred twice as frequently (OR = 1.87, 95% CI: 1.13, 3.08) if the E. coli had P pili or if the couples engaged in oral sex (OR = 2.09, 95% CI: 1.09, 4.00). Uropathogenic E. coli are more likely than commensal E. coli to be shared with a current heterosexual sex partner. Both sexual behaviors and a bacterial virulence factor, P pili, modified sharing.
Adaptation, Physiological↗
Molecular epidemiology of 3 putative virulence genes for Escherichia coli urinary tract infection-usp, iha, and iroN(E. coli).
This study describes the epidemiological association of 3 putative genes for virulence of uropathogenic Escherichia coli; uropathogenic specific protein (usp), a Vibrio cholerae zot gene homologue; IrgA homologue adhesin (iha), a nonhemagglutinating adhesin; and iroN(E. coli), a catechole siderophore receptor homologue. We compared the relative frequency in urinary tract infection (UTI) isolates (n=508), compared with non-UTI isolates (n=416). iroN(E. coli) occurred 2.1-3.6 times more frequently in UTI isolates than in rectal isolates (P=1.1x10-18 to P=2.7x10-5) and was associated with several uropathogenic virulence genes found on pathogenicity islands. usp occurred more frequently in isolates from patients with pyelonephritis (P=3.6x10-9), in periurethral isolates (P=.001), and in isolates from patients with UTI who were aged 40-65 years (P=.004), when compared with the rectal isolates; iha was not associated with UTI in this study.
Adolescent↗
Determinants of co-colonization with group B streptococcus among heterosexual college couples.
BACKGROUND: Group B causes morbidity and mortality among newborns, pregnant women, and nonpregnant adults. Among adults, sexual and fecal-oral routes of transmission are hypothesized; this study addresses whether sexual transmission occurs. METHODS: Our outcome of interest was group B. From our investigation of the heterosexual transmission of urinary tract infections among college students at the University of Michigan, conducted in 1996-1999, we identified 120 couples in which one or both partners carried group B. Each partner completed a questionnaire regarding potential risk factors for colonization. RESULTS: Co-colonization with the identical group B strain (as determined by pulsed-field gel electrophoresis) occurred in 86% of the 57 co-colonized couples. When the male sex partner carried group B, 64% of female partners also were colonized; conversely, 49% of male partners of colonized females were colonized with identical strains. Among behaviors predicting co-colonization within the partnership, male-to-female oral sex was a risk factor among both women (odds ratio [OR] = 2.9; 95% confidence interval [CI] = 1.2-6.9) and men (OR = 2.5; CI = 1.1-5.6). First sex at age 20 years or older was associated with an increased risk among women (OR = 2.1; CI = 0.7-6.4) and among men (OR = 3.0; CI = 1.0-9.3), and four or more lifetime sex partners was associated with a decreased risk of co-colonization among women (OR = 0.6; CI = 0.2-1.5) and among men (OR = 0.4; CI = 0.2-1.0). CONCLUSIONS: Among heterosexual college couples, sexual activity, particularly male-to-female oral sex, increases the risk of co-colonization with an identical group B strain. Future studies should evaluate the role of the pharynx and examine the effects of both bacterial characteristics and host response on transmission.
Adolescent↗
Variations in 10 putative uropathogen virulence genes among urinary, faecal and peri-urethral Escherichia coli.
A total of 868 isolates was screened from seven different collections of organisms from previous studies - pyelonephritis in children aged 1-24 months; first, second and recurring urinary tract infection (UTI) in women aged 18-39 years; UTI in women aged 40-65 years and peri-urethral and faecal isolates from women aged 18-39 years - for the presence of 10 potential Escherichia coli UTI virulence genes. Previously reported differences between the frequency of these genes in UTI compared with faecal isolates were confirmed and extended. A single virulence signature (strains containing aer, kpsMT, ompT, fim and papGAD) occurred in 29% of the pyelonephritic isolates, but in no more than 11% of the other collections. Peri-urethral isolates were found to have frequencies of these 10 genes that differed from those found for both UTI and faecal isolates.
Adolescent↗
Group B Streptococcus colonization in male and nonpregnant female university students: a cross-sectional prevalence study.
We describe the prevalence of colonization with group B Streptococcus species in a random sample of otherwise healthy male and nonpregnant female college students. Colonization with group B Streptococcus species occurs at a high frequency among healthy students, and there was a suggestion that it is associated with having engaged in sexual activity, tampon use, milk consumption, and hand washing done < or =4 times per day. However, larger studies are needed to verify these findings.
Adolescent↗