Virulence Factors of Streptococcus pneumoniae. Comparison between African and French Invasive Isolates and Implication for Future Vaccines.

BACKGROUND: Many surface proteins thought to promote Streptocococcus pneumoniae virulence have recently been discovered and are currently being considered as future vaccine targets. We assessed the prevalence of 16 virulence genes among 435 S. pneumoniae invasive isolates from France and the "African meningitis belt" region, with particular focus on serotype 1 (Sp1), to compare their geographical distribution, assess their association with site of infection and evaluate their potential interest as new vaccine candidates. METHODS: Detection by PCR of pspA (+families), pspC (+pspC.4), pavA, lytA, phtA,B,D,E, nanA,B,C, rrgA (Pilus-1), sipA (Pilus-2), pcpA and psrp was performed on all isolates, as well as antibiotic resistance testing and MLVA typing (+MLST on 54 representative strains). Determination of ply alleles was performed by sequencing (Sp1 isolates). RESULTS: MLVA and virulence genes profiles segregated Sp1 isolates into 2 groups that followed continent distribution. The ply allele 5 and most of the genes that were variable (nanC, Pilus-2, psrp, pcpA, phtD) were present in the French Sp1 isolates (PMEN clone Sweden(1)-28, ST306) but absent from the African ones. Whereas all African Sp1 isolates clustered into a single MLST CC (CC217), MLVA distinguished two CCs that followed temporal evolution. Pilus-2 and psrp were more prevalent in bacteraemic pneumonia yielded isolates and phtB in meningitis-related isolates. Considering vaccine candidates, phtD was less prevalent than anticipated (50%) and pcpA varied importantly between France and Africa (98% versus 34%). Pilus-1 was carried by 7-11% of isolates and associated with ß-lactams resistance. CONCLUSIONS: Most virulence genes were carried by the European ST306 clone but were lacking on Sp1 isolates circulating in the African meningitis belt, where a more serious pattern of infection is observed. While virulence proteins are now considered as vaccine targets, the geographical differences in their prevalence could affect the efficacy expected from future vaccines.

Multiple-locus variable-number tandem-repeat analysis of Streptococcus pneumoniae and comparison with multiple loci sequence typing.

BACKGROUND: Streptococcus pneumoniae infections remain a major cause of morbidity and mortality worldwide. The diversity of pneumococci was first evidenced by serotyping of their capsular polysaccharides, responsible of virulence, resolving into more than 93 serotypes. Molecular tools have been developed to track the emergence and the spread of resistant, hyper virulent or non-vaccine type clones, particularly DNA-based methods using genetic polymorphism. Pulsed-Field Gel Electrophoresis analysis (PFGE) and Multiple Loci Sequence Typing (MLST) are the most frequently used genotyping techniques for S. pneumoniae. MLST is based on sequence comparison of housekeeping genes clustering isolates within sequence types. The availability of genome sequence data from different S. pneumoniae strains facilitated the search for other class of genetic markers as polymorphic DNA sequences for a Multiple-Locus Variable-Number Tandem-Repeat Analysis (MLVA). This study aims at confirming the relevance of MLVA of S. pneumoniae, comparing MLST and MLVA performances when discriminating subgroups of strains belonging to the same Sequence Type (ST), and defining a restricted but universal set of MLVA markers that has at least the same discriminatory power as MLST for S. pneumoniae by applying marker sets used by different authors on 331 isolates selected in UK. RESULTS: A minimum spanning tree was built including the serotypes distribution and comparing MLVA and MLST results. 220 MLVA types were determined grouped in 10 Sequence Types (ST). MLVA differentiated ST162 in two clonal complexes. A minimal set was defined: ms 25 and ms37, ms17, ms19, ms33, ms39, and ms40 including two universal markers. The selection was based on MLVA markers with a Diversity Index >0.8 and a selection of others depending of the population tested and the aim of the study. This set of 7 MLVA markers yields strain clusters similar to those obtained by MLST. CONCLUSIONS: MLVA can discriminate relevant subgroups among strains belonging to the same ST. MLVA offers the possibility to deduce the ST from the MLVA Type. It permits to investigate local outbreaks or to track the worldwide spread of clones and the emergence of variants.

[Acute appendicitis due to both Klebsiella pneumoniae and serotype 35B Streptococcus pneumoniae, an emergent serotype]. / Appendicite aiguë à Klebsiella pneumoniae et Streptococcus pneumoniae de sérotype 35B, un sérotype émergent.

Streptococcus pneumoniae has been rarely considered as an infectious agent in appendicitis. We report a case of a 47-year-old woman with acute appendicitis caused both by serotype 35B S. pneumoniae and Klebsiella pneumoniae. The pathway of the appendix colonisation remains unclear. It could be explain by direct infection via mucosal translocation or by hematogenous spread. Pneumococcal appendicitis could progress to perforation more frequently. The use of intraoperative samples for management of appendicitis is controversial. But, culture with appropriate media is the only mean to isolate bacteria not very often encountered in appendicitis and to identify species of epidemiologic interest as serotype 35B S. pneumoniae, a non vaccinal serotype resistant to penicillin which is considered as a potential emergent pathogen. In the case of S. pneumoniae appendicitis, it could be recommended to take complementary directed samples to understand its pathophysiology.

Efficacy of a swab transport system in maintaining long-term viability of Staphylococcus aureus.

The noncharcoal liquid Amies swab transport system (Copan, Bovezzo, Italy) can be used for the collection and transport of biologic samples from carriers and infected patients for the detection of strains of Staphylococcus aureus in epidemiologic field studies. We suggest that the maximum holding time, between swab collection and culture, should be 18 days.