Androulla Efstratiou

Genetic relationships between clinical isolates of Streptococcus pneumoniae, Streptococcus oralis, and Streptococcus mitis: characterization of "Atypical" pneumococci and organisms allied to S. mitis harboring S. pneumoniae virulence factor-encoding genes.

ABSTRACT The oral streptococcal group (mitis phylogenetic group) currently consists of nine recognized species, although the group has been traditionally difficult to classify, with frequent changes in nomenclature over the years. The pneumococcus (Streptococcus pneumoniae), an important human pathogen, is traditionally distinguished from the most closely related oral streptococcal speciesStreptococcus mitis and Streptococcus oralis on the basis of three differentiating characteristics: optochin susceptibility, bile solubility, and agglutination with antipneumococcal polysaccharide capsule antibodies. However, there are many reports in the literature of pneumococci lacking one or more of these defining characteristics. Sometimes called “atypical” pneumococci, these isolates can be the source of considerable confusion in the clinical laboratory. Little is known to date about the genetic relationships of such organisms with classical S. pneumoniae isolates. Here we describe these relationships based on sequence analysis of housekeeping genes in comparison with previously characterized isolates of S. pneumoniae,S. mitis, and S. oralis. While most pneumococci were found to represent a closely related group these studies identified a subgroup of atypical pneumococcal isolates (bile insoluble and/or “acapsular”) distinct from, though most closely related to, the “typical” pneumococcal isolates. However, a large proportion of isolates, found to be atypical on the basis of capsule reaction alone, did group with typical pneumococci, suggesting that they have either lost capsule production or represent as-yet-unrecognized capsular types. In contrast to typical S. pneumoniae, isolates phenotypically identified as S. mitis and S. oralis, which included isolates previously characterized in taxonomic studies, were genetically diverse. While most of the S. oralis isolates did fall into a well-separated group, S. mitis isolates did not cluster into a well-separated group. During the course of these studies we also identified a number of potentially important pathogenic isolates, which were frequently associated with respiratory disease, that phenotypically and genetically are most closely related to S. mitis but which harbor genes encoding the virulence determinants pneumolysin and autolysin classically associated with S. pneumoniae.

Epidemiology of Severe Streptococcus pyogenes Disease in Europe

ABSTRACT The past 2 decades have brought worrying increases in severe Streptococcus pyogenes diseases globally. To investigate and compare the epidemiological patterns of these diseases within Europe, data were collected through a European Union FP-5-funded program (Strep-EURO). Prospective population-based surveillance of severe S. pyogenes infection diagnosed during 2003 and 2004 was undertaken in 11 countries across Europe (Cyprus, the Czech Republic, Denmark, Finland, France, Germany, Greece, Italy, Romania, Sweden, and the United Kingdom) using a standardized case definition. A total of 5,522 cases were identified across the 11 countries during this period. Rates of reported infection varied, reaching 3/100,000 population in the northern European countries. Seasonal patterns of infection showed remarkable congruence between countries. The risk of infection was highest among the elderly, and rates were higher in males than in females in most countries. Skin lesions/wounds were the most common predisposing factor, reported in 25% of cases; 21% had no predisposing factors reported. Skin and soft tissue were the most common foci of infection, with 32% of patients having cellulitis and 8% necrotizing fasciitis. The overall 7-day case fatality rate was 19%; it was 44% among patients who developed streptococcal toxic shock syndrome. The findings from Strep-EURO confirm a high incidence of severe S. pyogenes disease in Europe. Furthermore, these results have identified targets for public health intervention, as well as raising awareness of severe S. pyogenes disease across Europe.

Clinical and Microbiological Characteristics of Severe Streptococcus pyogenes Disease in Europe

ABSTRACT In an attempt to compare the epidemiology of severe Streptococcus pyogenes infection within Europe, prospective data were collected through the Strep-EURO program. Surveillance for severe cases of S. pyogenes infection diagnosed during 2003 and 2004 was undertaken in 11 countries across Europe by using a standardized case definition and questionnaire. Patient data as well as bacterial isolates were collected and characterized by T and M/emm typing, and selected strains were analyzed for the presence of superantigen genes. Data were analyzed to compare the clinical and microbiological patterns of the infections across the participating countries. A total of 4,353 isolates were collected from 5,521 cases with severe S. pyogenes infections who were identified. A wide diversity of M/emm types (n = 104) was found among the S. pyogenes clinical isolates, but the M/emm type distribution varied broadly between participating countries. The 10 most predominant M/emm types were M/emm type 1 (M/emm1), M/emm28, M/emm3, M/emm89, M/emm87, M/emm12, M/emm4, M/emm83, M/emm81, and M/emm5, in descending order. A correlation was found between some specific disease manifestations, the age of the patients, and the emm types. Although streptococcal toxic shock syndrome and necrotizing fasciitis were caused by a large number of types, they were particularly associated with M/emm1 and M/emm3. The emm types included in the 26-valent vaccine under development were generally well represented in the present material; 16 of the vaccine types accounted for 69% of isolates. The Strep-EURO collaborative program has contributed to enhancement of the knowledge of the spread of invasive disease caused by S. pyogenes within Europe and encourages future surveillance by the notification of cases and the characterization of strains, which are important for vaccination strategies and other health care issues.

Group B streptococcal disease in UK and Irish infants younger than 90 days

The incidence, morbidity, and mortality of group B streptococcal disease in the UK and Republic of Ireland are largely unknown. Between Feb 1, 2000, and Feb 28, 2001, we identified cases of invasive group B streptococcal disease in infants younger than 90 days through surveillance involving paediatricians, microbiologists, and parents. 568 cases were identified, equivalent to a total incidence of 0.72 per 1000 live-births (95% CI 0.66-0.78); the incidence for early-onset disease (n=377) was 0.48 per 1000 (0.43-0.53), and for late-onset disease (n=191) was 0.24 per 1000 (0.21-0.28). Risk factors were identifiable for 218 (58%) cases of early-onset disease. 53 infants died (overall 9.7%). We have established the minimum current burden of group B streptococcal disease in UK and Irish infants. This information will assist in the formulation of guidelines for prevention of this disease.

Severe Streptococcus pyogenes Infections, United Kingdom, 2003–2004

Epidemiology of severe disease caused by this organism has changed, with increased incidence and different risk groups.

Clonal Spread of Group A Streptococcus with the New Type of Erythromycin Resistance

In 1990, a new type of erythromycin resistance phenotype, designated NR, was found in group A streptococcus (GAS) in Finland. In the present study, the distribution of GAS isolates with this and other erythromycin-resistance phenotypes was surveyed in Finland, and the clonality of the isolates was explored. Of 4179 GAS isolates collected from all over Finland, 695 (17%) were resistant to erythromycin, and 82% of these had the NR phenotype. Of a group of 96 isolates with the NR phenotype from different areas, 91% was T4 serotype, opacity factor-positive. The majority of these isolates were studied further: All were M4 serotype and 88% were of one clonal origin in genetic analyses. Thus, one single clone predominates among erythromycin-resistant GAS in Finland. This clone is of T4M4 serotype and mediates the new type of erythromycin resistance, characterized by the NR phenotype.

Characterization of Group B Streptococci Recovered from Infants with Invasive Disease in England and Wales

Group B streptococci (GBS) are a major cause of invasive disease in infants, with enhanced surveillance in England and Wales showing an incidence of 0.74 cases per 1000 live births and a mortality rate of 8%. Among 353 isolates obtained during enhanced surveillance, the predominant serotypes were III (48%), Ia (27%), and V (10%), and the remainder comprised Ib, II, IV, VI, and VII; 3% were not typable. Isolates from patients with early-onset disease had serotypes III (38%), Ia (32%), and V (13%), with late-onset disease having a higher incidence of type III (67%) strains. Patients infected with serotype III strains had a higher rate of meningitis, and those with type V strains had a higher mortality rate. Isolates were susceptible to penicillin and ampicillin, but 4% were resistant to erythromycin, and 91% were resistant to tetracycline. A trivalent vaccine containing capsular polysaccharides III, Ia, and V could theoretically provide coverage against 85% of the cases of GBS disease among infants in England and Wales.

Pangenomic Study of Corynebacterium diphtheriae That Provides Insights into the Genomic Diversity of Pathogenic Isolates from Cases of Classical Diphtheria, Endocarditis, and Pneumonia

Corynebacterium diphtheriae is one of the most prominent human pathogens and the causative agent of the communicable disease diphtheria. The genomes of 12 strains isolated from patients with classical diphtheria, endocarditis, and pneumonia were completely sequenced and annotated. Including the genome of C. diphtheriae NCTC 13129, we herewith present a comprehensive comparative analysis of 13 strains and the first characterization of the pangenome of the species C. diphtheriae. Comparative genomics showed extensive synteny and revealed a core genome consisting of 1,632 conserved genes. The pangenome currently comprises 4,786 protein-coding regions and increases at an average of 65 unique genes per newly sequenced strain. Analysis of prophages carrying the diphtheria toxin gene tox revealed that the toxoid vaccine producer C. diphtheriae Park-Williams no. 8 has been lysogenized by two copies of the ω(tox)(+) phage, whereas C. diphtheriae 31A harbors a hitherto-unknown tox(+) corynephage. DNA binding sites of the tox-controlling regulator DtxR were detected by genome-wide motif searches. Comparative content analysis showed that the DtxR regulons exhibit marked differences due to gene gain, gene loss, partial gene deletion, and DtxR binding site depletion. Most predicted pathogenicity islands of C. diphtheriae revealed characteristics of horizontal gene transfer. The majority of these islands encode subunits of adhesive pili, which can play important roles in adhesion of C. diphtheriae to different host tissues. All sequenced isolates contain at least two pilus gene clusters. It appears that variation in the distributed genome is a common strategy of C. diphtheriae to establish differences in host-pathogen interactions.

The epidemiology of severe Streptococcus pyogenes associated disease in Europe

Several European countries reported outbreaks of severe disease caused by Streptococcus pyogenes in the late 1980s. This marked a departure from the previous decades, where very few such outbreaks were noted. These changes in disease occurrence formed part of a global phenomenon, the reasons for which have yet to be explained. Results of surveillance activities for invasive S. pyogenes infection within Europe over the past fifteen years identified further increases in many countries. However, variations in surveillance methods between countries preclude robust comparisons being made, illustrating the need for a unified surveillance strategy across Europe. This was finally embodied in the Strep-EURO programme, introduced in 2002.

Diphtheria in the United Kingdom, 1986–2008: the increasing role of Corynebacterium ulcerans

Diphtheria is an uncommon disease in the UK due to an effective immunization programme; consequently when cases do arise, there can be delays in diagnosis and case-fatality rates remain high. We reviewed 102 patients with infections caused by toxigenic corynebacteria (an average of four per year) reported in the UK between 1986 and 2008: 42 Corynebacterium diphtheriae, 59 C. ulcerans and one C. pseudotuberculosis, as well as 23 asymptomatic carriers. Five fatalities were reported, all in unvaccinated patients. The major risk factor for C. diphtheriae infection continued to be travel to an endemic country. C. ulcerans infections became more common than C. diphtheriae infections in the UK; they were associated with contact with companion animals. The occurrence of indigenous severe C. ulcerans infections and imported C. diphtheriae cases highlights the need to maintain UK routine vaccination coverage at the 95% level in the UK, as recommended by the World Health Organization.