Carriage-associated Streptocccus pneumoniae serotype 1 in Brussels, Belgium.

Streptococcus pneumoniae serotype 1 presents a high invasiveness index and is seldom isolated from its niche, the nasopharynx. We report an unusual serotype 1 carriage in a healthy pediatric population at the time of the heptavalent pneumococcal vaccine adoption in Belgium. Our sampling period coincides with an epidemic wave of serotype 1 invasive pneumococcal infections. Invasive and colonizing isolates were characterized by both antibiotic resistance profile and multilocus sequence typing and were shown to share the same backbone (ST306 and ST350).

Characterization of novel phages isolated in coagulase-negative staphylococci reveals evolutionary relationships with Staphylococcus aureus phages.

Despite increasing interest in coagulase-negative staphylococci (CoNS), little information is available about their bacteriophages. We isolated and sequenced three novel temperate Siphoviridae phages (StB12, StB27, and StB20) from the CoNS Staphylococcus hominis and S. capitis species. The genome sizes are around 40 kb, and open reading frames (ORFs) are arranged in functional modules encoding lysogeny, DNA metabolism, morphology, and cell lysis. Bioinformatics analysis allowed us to assign a potential function to half of the predicted proteins. Structural elements were further identified by proteomic analysis of phage particles, and DNA-packaging mechanisms were determined. Interestingly, the three phages show identical integration sites within their host genomes. In addition to this experimental characterization, we propose a novel classification based on the analysis of 85 phage and prophage genomes, including 15 originating from CoNS. Our analysis established 9 distinct clusters and revealed close relationships between S. aureus and CoNS phages. Genes involved in DNA metabolism and lysis and potentially in phage-host interaction appear to be widespread, while structural genes tend to be cluster specific. Our findings support the notion of a possible reciprocal exchange of genes between phages originating from S. aureus and CoNS, which may be of crucial importance for pathogenesis in staphylococci.

Sequential multiplex PCR assay for determining capsular serotypes of colonizing S. pneumoniae.

BACKGROUND: Asymptomatic nasopharyngeal carriage represents an important biological marker for monitoring pneumococcal serotype distribution and evaluating vaccine effects. Serotype determination by conventional method (Quellung reaction) is technically and financially challenging. On the contrary, PCR-based serotyping represents a simple, economic and promising alternative method. METHOD: We designed a novel multiplex PCR assay for specific detection of the 30 classical colonizing S. pneumoniae serogroups/types. This multiplex assay is composed of 7 consecutive PCR reactions and was validated on a large and recent collection of Streptococcus pneumoniae isolated during a prospective study conducted in Belgium at the time of PCV7 adoption. RESULTS: The multiplex PCR assay allowed the typing of more than 94% of the isolates of a collection of pneumococci isolated from Belgian preschool attendees (n = 332). Seventy-five percent of the isolates were typed after 3 subsequent PCR reactions. Results were in agreement with the Quellung identification. CONCLUSION: Our novel multiplex assay is an accurate and reliable method which can be used in place of the conventional method for S. pneumoniae carriage studies.

Characterization of a novel temperate phage originating from a cereulide-producing Bacillus cereus strain.

A novel temperate bacteriophage was isolated from a Bacillus cereus cereulide-producing strain and named vB_BceS-IEBH. vB_BceS-IEBH belongs to the Siphoviridae family. The complete genome sequence (53 kb) was determined and annotated. Eighty-seven ORFs were detected and for 28, a putative function was assigned using the ACLAME database. vB_BceS-IEBH replicates as a plasmid in the prophage state. Accordingly, a 9-kb plasmid-like region composed of 13 ORFs was identified. A fragment of around 2000 bp comprising an ORF encoding a putative plasmid replication protein was shown to be self-replicating in Bacillus thuringiensis. Mass spectrometry analysis of the purified vB_BceS-IEBH particle identified 8 structural proteins and enabled assignment of a supplementary ORF as being part of the morphogenesis module. Genome analysis further illustrates the diversity of mobile genetic elements and their plasticity within the B. cereus group.

Group A Streptococcus virulence and host factors in two toddlers with rheumatic fever following toxic shock syndrome.

BACKGROUND: Rheumatic fever (RF) classically occurs after group A Streptococcus (GAS) pharyngitis in children aged over 5 years in developing countries. The present report describes the bacterial and host determinants in non-related toddlers who developed RF diagnostic criteria after toxic shock syndrome (TSS). METHODS AND RESULTS: A 13-month-old boy and a 14-month-old girl presented GAS TSS. After several weeks, multiple subcutaneous nodules as well as migratory polyarthritis or monoarthritis developed in both children, fulfilling Jones criteria of RF. The relevance of the Jones criteria for very young children is, however, debatable and their use might lead to the unnecessary prescribing of secondary prophylaxis. A molecular analysis of both bacterial and host factors was carried out in an attempt to decipher the combination that could have led to such uncommon, but very similar presentations. The two GAS isolates belonged to the usual, although distinct, invasive emm-types 1 and 3. Both isolates carried a wide set of prophage-encoded virulence factors, with only the speG and speA superantigen-encoding genes in common. Both patients shared the HLA DQB1*0301 allele, which has been associated with susceptibility to GAS necrotizing fasciitis. CONCLUSIONS: Our study exemplifies the particularity of RF in young children and the complex role of superantigens and streptodornases in GAS-related pathologies.

Polyclonal dissemination of tetracycline resistance among Streptococcus pyogenes paediatric isolates from Brazil.

INTRODUCTION: Scarce data are available on Group A Streptococcus (GAS) antibiotic resistance in South America. METHODOLOGY: The antibiotic susceptibility patterns of GAS recovered from symptomatic children living in the central part of Brazil during a prospective epidemiological study were analyzed. RESULTS: No isolates were resistant to penicillin or macrolides.  Sixty-one percent of the isolates were highly resistant to tetracycline, of which 85% harboured the tetM resistance gene. Ninety-five percent of these tetracycline resistant isolates were also resistant to minocycline. Thirty different emm-types were associated with tetracycline resistance. Phylogenetic analysis indicates that tetracycline resistance arose independently in distantly related emm-types. CONCLUSIONS: A high level of GAS tetracycline resistance has been observed in the central part of Brazil due to the polyclonal dissemination of resistant emm-types.