Streptococcus pneumoniae capsule determines disease severity in experimental pneumococcal meningitis.

Streptococcus pneumoniaebacteria can be characterized into over 90 serotypes according to the composition of their polysaccharide capsules. Some serotypes are common in nasopharyngeal carriage whereas others are associated with invasive disease, but when carriage serotypes do invade disease is often particularly severe. It is unknown whether disease severity is due directly to the capsule type or to other virulence factors. Here, we used a clinical pneumococcal isolate and its capsule-switch mutants to determine the effect of capsule, in isolation from the genetic background, on severity of meningitis in an infant rat model. We found that possession of a capsule was essential for causing meningitis. Serotype 6B caused significantly more mortality than 7F and this correlated with increased capsule thickness in the cerebrospinal fluid (CSF), a stronger inflammatory cytokine response in the CSF and ultimately more cortical brain damage. We conclude that capsule type has a direct effect on meningitis severity. This is an important consideration in the current era of vaccination targeting a subset of capsule types that causes serotype replacement.

Clinical decisions related to CBC screening of asymptomatic full-term infants at risk for group B streptococcus disease

Objective. Although complete blood count (CBC) changes occur with the development of clinical sepsis in newborns, the CBC has not been reported to be a sensitive predictor of sepsis in asymptomatic full-term newborn infants, nor has it been reported to be related to risk factors for sepsis or clinical decisions. The objective of this study was to evaluate the relationship between the WBC/I:T (immature:total neutrophil) ratio and maternal group B streptococcal (GBS) risk factors (rupture of membranes ≥18 hours, maternal temperature ≥100.4°F, maternal age ≤20 years, previous infant with invasive GBS disease, maternal GBS bacteriuria, and black ethnicity); and to evaluate the relationship between the WBC/I:T ratios and providers' clinical decisions (observe versus repeat the CBC or complete sepsis evaluation) in the asymptomatic full-term newborn at risk for early-onset GBS sepsis. ^ Methods. Medical records of infants admitted to the well baby nursery at a tertiary care teaching hospital in Houston, TX between 1/1/99 and 12/31/00 whose gestational ages were ≥35 weeks; who had mothers with GBS positive or unknown culture status and inadequate intrapartum antibiotic prophylaxis; and who had screening CBCs performed in the first 30 hours of life because of GBS risk were reviewed (n = 412). Demographic information, maternal GBS risk factors, CBC results, clinical decisions, and rationales for clinical decisions were collected. ^ Results. With the exception of black ethnicity (p = .0000, odds ratio = 0.213), no statistically significant differences in risk factors between infants with normal and abnormal WBC counts or normal and abnormal I:T ratios were found. Infants with abnormal WBCs had a significantly higher likelihood of having a CBC repeated (p = 0.002 for WBC). Providers documented the CBC result in the rationale for clinical decisions in 62% of the cases. ^ Conclusion. The CBC results were not related to maternal risk factors for GBS except for ethnicity. Black infants had significantly lower WBC levels than infants of other ethnicities, although this difference was clinically insignificant. Infants with abnormal WBCs had a significantly higher likelihood of undergoing repeat CBCs but not sepsis evaluations. Provider rationale was difficult to evaluate due to insufficient documentation. The screening CBC result did not impact the clinicians' decisions to initiate sepsis evaluations in this population. ^

Alpha C protein of group B Streptococcus as a potential vaccine candidate

Group B Streptococcus (GBS) is a leading cause of life-threatening infection in neonates and young infants, pregnant women, and non-pregnant adults with underlying medical conditions. Immunization has theoretical potential to prevent significant morbidity and mortality from GBS disease. Alpha C protein (α C), found in 70% of non-type III capsule polysaccharide group B Streptococcus, elicits antibodies protective against α C-expressing strains in experimental animals and is an appealing carrier for a GBS conjugate vaccine. We determined whether natural exposure to α C elicits antibodies in women and if high maternal α C-specific serum antibody at delivery is associated with protection against neonatal disease. An ELISA was designed to measure α C-specific IgM and IgG in human sera. A case-control design (1:3 ratio) was used to match α C-expressing GBS colonized and non-colonized women by age and compare quantified serum α C-specific IgM and IgG. Sera also were analyzed from bacteremic neonates and their mothers and from women with invasive GBS disease. Antibody concentrations were compared using t-tests on log-transformed data. Geometric mean concentrations of α C-specific IgM and IgG were similar in sera from 58 α C strain colonized and 174 age-matched non-colonized women (IgG 245 and 313 ng/ml; IgM 257 and 229 ng/ml, respectively). Delivery sera from mothers of 42 neonates with GBS α C sepsis had similar concentrations of α C-specific IgM (245 ng/ml) and IgG (371 ng/ml), but acute sera from 13 women with invasive α C-expressing GBS infection had significantly higher concentrations (IgM 383 and IgG 476 ng/ml [p=0.036 and 0.038, respectively]). Convalescent sera from 5 of these women 16-49 days later had high α C-specific IgM and IgG concentrations (1355 and 4173 ng/ml, respectively). In vitro killing of α C-expressing GBS correlated with total α C-specific antibody concentration. Invasive disease but not colonization elicits α C-specific IgM and IgG in adults. Whether α C-specific IgG induced by vaccine would protect against disease in neonates merits further investigation. ^

THE OCCURRENCE OF GROUP G STREPTOCOCCUS IN THE DOMESTIC CAT: COMPARISON OF THE PHYSIOLOGICAL PROPERTIES OF GROUP G STREPTOCOCCUS ISOLATED FROM HUMANS AND CATS

The occurrence of group G streptococci in cats and evaluation of the recovered organisms as potential human pathogens was investigated. Throat swabs were obtained from 89 cats (47 males and 42 females) and vaginal swabs from 39 female cats. Eighty-three of the examined cats were housed in individual cages at a University Animal Care Facility. Six cats, 2 mature males, 2 mature females and 2 young females were family pets in a rural area. Beta-hemolytic streptococci were recovered from 33 (37%) of the 89 cat throats cultured, and 27 (30.3%) were identified as group G. More males (34%) than females (24%) had throat cultures positive for group G. From the 39 vaginal cultures examined, 24 (61.5%) contained beta-hemolytic streptococci and 23 (58.9%) were identified as group G streptococci. Streptococci were not recovered from the vaginal cultures of the 5 females under 6 months of age.^ Thirty one group G streptococci isolated from cats were compared with 37 isolates of group G obtained from humans (health status or site of origin unknown). More group G cat isolates (81%) produced deoxyribonuclease (DNase) than did the human isolates (36%). The proportion of cat throat and vaginal isolates producing DNase was the same. Production of nicotinamide adenine dinucleotide glycohydrolase (NADase) by group G isolates of human origin was 70%, cat throat isolates 53% and cat vaginal isolates 37%. The Serum Opacity Factor was present in 73% of the cat throat isolates of group G, 43.7% of the cat vaginal isolates and 58.6% of the human isolates. Possession of an anti-phagocytic factor (M protein like substance) demonstrated by the ability to multiply in fresh human blood was greater in the group G from cat throats (46.7%) than from cat vagina (37.5%) or from the human isolates (13.5%). Many of the biochemical characteristics of the group G streptococci of cat origin were more similar to the biochemical characteristics of group A streptococci, than to the characteristics of group G of human origin. The group G streptococci, found in a large number of cats, could be potential human pathogens, as their physiological and biological characteristics are very similar to those of group A, a known human pathogen. ^

Inactivation of the α C protein antigen gene, bca, by a novel shuttle/suicide vector results in attenuation of virulence and immunity in group B Streptococcus

The α C protein of group B Streptococcus (GBS) is a major surface-associated antigen. Although its role in the biology and virulence of GBS has not been defined, it is opsonic and capable of eliciting protective immunity. The α C protein is widely distributed among clinical isolates and is a potential protein carrier and antigen in conjugate vaccines to prevent GBS infections. The structural gene for the α C protein, bca, has been cloned and sequenced. The protein encoded by bca is related to a class of surface-associated proteins of Gram-positive cocci involved in virulence and immunity. To investigate the potential roles of the α C protein, bca null mutants were generated in which the bca gene was replaced with a kanamycin resistance cassette via homologous recombination using a novel shuttle/suicide vector. Studies of lethality in neonatal mice showed that the virulence of the bca null mutants was attenuated 5- to 7-fold when compared with the isogenic wild-type strain A909. Significant differences in mortality occurred in the first 24 h, suggesting that the role of the α antigen is important in the initial stages of the infection. In contrast to A909, bca mutants were no longer killed by polymorphonuclear leukocytes in the presence of α-specific antibodies in an in vitro opsonophagocytic assay. In contrast to previous studies, α antigen expression does not appear to play a role in resistance to opsonophagocytosis in the absence of α-specific antibodies. In addition, antibodies to the α C protein did not passively protect neonatal mice from lethal challenge with bca mutants, suggesting that these epitopes are uniquely present within the α antigen as expressed from the bca gene. Therefore, the α C protein is important in the pathogenesis of GBS infection and is a target for protective immunity in the development of GBS vaccines.

Multilocus analysis of extracellular putative virulence proteins made by group A Streptococcus: Population genetics, human serologic response, and gene transcription

Species of pathogenic microbes are composed of an array of evolutionarily distinct chromosomal genotypes characterized by diversity in gene content and sequence (allelic variation). The occurrence of substantial genetic diversity has hindered progress in developing a comprehensive understanding of the molecular basis of virulence and new therapeutics such as vaccines. To provide new information that bears on these issues, 11 genes encoding extracellular proteins in the human bacterial pathogen group A Streptococcus identified by analysis of four genomes were studied. Eight of the 11 genes encode proteins with a LPXTG(L) motif that covalently links Gram-positive virulence factors to the bacterial cell surface. Sequence analysis of the 11 genes in 37 geographically and phylogenetically diverse group A Streptococcus strains cultured from patients with different infection types found that recent horizontal gene transfer has contributed substantially to chromosomal diversity. Regions of the inferred proteins likely to interact with the host were identified by molecular population genetic analysis, and Western immunoblot analysis with sera from infected patients confirmed that they were antigenic. Real-time reverse transcriptase–PCR (TaqMan) assays found that transcription of six of the 11 genes was substantially up-regulated in the stationary phase. In addition, transcription of many genes was influenced by the covR and mga trans-acting gene regulatory loci. Multilocus investigation of putative virulence genes by the integrated approach described herein provides an important strategy to aid microbial pathogenesis research and rapidly identify new targets for therapeutics research.

An unmodified heptadecapeptide pheromone induces competence for genetic transformation in Streptococcus pneumoniae.

Competence for genetic transformation in Streptococcus pneumoniae has been known for three decades to arise in growing cultures at a critical cell density, in response to a secreted protease-sensitive signal. We show that strain CP1200 produces a 17-residue peptide that induces cells of the species to develop competence. The sequence of the peptide was found to be H-Glu-Met-Arg-Leu-Ser-Lys-Phe-Phe-Arg-Asp-Phe-Ile-Leu-Gln-Arg- Lys-Lys-OH. A synthetic peptide of the same sequence was shown to be biologically active in small quantities and to extend the range of conditions suitable for development of competence. Cognate codons in the pneumococcal chromosome indicate that the peptide is made ribosomally. As the gene encodes a prepeptide containing the Gly-Gly consensus processing site found in peptide bacteriocins, the peptide is likely to be exported by a specialized ATP-binding cassette transport protein as is characteristic of these bacteriocins. The hypothesis is presented that this transport protein is encoded by comA, previously shown to be required for elaboration of the pneumococcal competence activator.

Homeologous recombination and mismatch repair during transformation in Streptococcus pneumoniae: saturation of the Hex mismatch repair system.

The ability of the Hex generalized mismatch repair system to prevent recombination between partially divergent (also called homeologous) sequences during transformation in Streptococcus pneumoniae was investigated. By using as donor in transformation cloned fragments 1.7-17.5% divergent in DNA sequence from the recipient, it was observed that the Hex system prevents chromosomal integration of the least and the most divergent fragments but frequently fails to do so for other fragments. In the latter case, the Hex system becomes saturated (inhibited) due to an excess of mismatches: it is unable to repair a single mismatch located elsewhere on the chromosome. Further investigation with chromosomal donor DNA, carrying only one genetically marked divergent region, revealed that a single divergent fragment can lead to saturation of the Hex system. Increase in cellular concentration of either HexA, the MutS homologue that binds mismatches, or HexB, the MutL homologue for which the essential role in repair as yet remains obscure, was shown to restore repair ability in previously saturating conditions. Investigation of heterospecific transformation by chromosomal DNA from two related streptococcal species, Streptococcus oralis and Streptococcus mitis, also revealed complete saturation of the Hex system. Therefore the Hex system is not a barrier to interspecies recombination in S. pneumoniae. These results are discussed in light of those described for the Mut system of Escherichia coli.

Sépsis neonatal com meningite a streptococcus do grupo B na era do rastreio e da quimioprofilaxia : a propósito de um caso clínico

Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2014

Associação de infecção por Streptococcus Bovis e o carcinoma colorrectal

Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2014

Recurrent bacteremia with Streptococcus dysgalactiae: a case-control study.

Beta-hemolytic streptococci of groups C and G, designated as Streptococcus dysgalactiae (SD), can cause severe and recurring invasive infections. In this case-control study, we aimed to identify clinical and molecular risk factors for recurrence of SD bacteremia. Twenty-two cases of recurrent SD bacteremia were identified, and median time between episodes was 6 months. The most frequent clinical manifestation was skin and soft tissue infection. Cases and 92 controls, with single-episode SD bacteremia, showed similar demographics, had similar Charlson comorbidity scores, and had similar clinical presentations. Thirty-day fatality was 13% among controls, whereas none of 22 cases died. In 19 cases (86%), the same emm type was encountered in both episodes. SD isolates from recurrent episodes and from single episodes had a similar emm type distribution. Thus, we did not identify clinical risk factors for recurrences. The high proportion of identical emm types in recurrent episodes indicates a host-specific colonization.

Serotype/serogroup-specific antibiotic non-susceptibility of invasive and non-invasive Streptococcus pneumoniae, Switzerland, 2004 to 2014.

Concurrent analysis of antibiotic resistance of colonising and invasive Streptococcus pneumoniae gives a more accurate picture than looking at either of them separately. Therefore, we analysed 2,129 non-invasive and 10,996 invasive pneumococcal isolates from Switzerland from 2004 to 2014, which spans the time before and after the introduction of the heptavalent (PCV7) and 13-valent (PCV13) conjugated pneumococcal polysaccharide vaccines. Serotype/serogroup information was linked with all antibiotic resistance profiles. During the study period, the proportion of non-susceptible non-invasive and invasive isolates significantly decreased for penicillin, ceftriaxone, erythromycin and trimethoprim/sulfamethoxazole (TMP-SMX). This was most apparent in non-invasive isolates from study subjects younger than five years (penicillin (p = 0.006), erythromycin (p = 0.01) and TMP-SMX (p = 0.002)). Resistant serotypes/serogroups included in PCV7 and/or PCV13 decreased and were replaced by non-PCV13 serotypes (6C and 15B/C). Serotype/serogroup-specific antibiotic resistance rates were comparable between invasive and non-invasive isolates. Adjusted odds ratios of serotype/serogroup-specific penicillin resistance were significantly higher in the west of Switzerland for serotype 6B (1.8; 95% confidence interval (CI): 1.4-4.8), 9V (3.4; 95% CI: 2.0-5.7), 14 (5.3; 95% CI: 3.8-7.5), 19A (2.2; 95% CI: 1.6-3.1) and 19F (3.1; 95% CI: 2.1-4.6), probably due to variations in the antibiotic consumption.

Short communication: Role of Streptococcus pluranimalium in Mediterranean buffaloes (Bubalus bubalis) with different udder health statuses

The aims of the current study were to describe presence and clinical role over time of Streptococcus pluranimalium isolated in milk samples of Mediterranean buffalo (MB). Two hundred composite milk samples originating from 40 primiparous MB were collected at 10, 30, 60, 90, and 150d in milk (DIM) and from 20 pluriparous MB at 77 to 120 DIM. Milk samples were used for analysis of somatic cell counts, bacteriological cultures, and identification (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry). Nine of 200 (4.5%) samples of primiparous MB and 3 of 20 (15%) samples of pluriparous MB were positive for Strep. pluranimalium. The prevalence of the bacterium in primipari was 0% (0/40) at 10, 30, and 150 DIM, whereas it was 5 (2/40) and 17.5% (7/40) at 60 and 90 DIM, respectively. Eight primipari were positive only once, whereas 1 was positive at 2 different samplings. Mono-infection was not detected in any of the age categories or udder health status. Infections were transient in primipari. Clinical mastitis was observed in primipari once at 90 DIM, subclinical mastitis detected twice in the same animals at 60 and 90 DIM, and intramammary infections were diagnosed 1 and 5 times at 60 and 90 DIM in primipari, respectively, whereas 3 infections were diagnosed in pluripari. The clinical reflections demonstrate for the first time the presence of Strep. pluranimalium in MB and its association with different udder health status. Nevertheless, it cannot be excluded that the bacterium may simply follow a pattern of commensal or opportunistic behavior, taking advantage of a preexisting bacterial udder infection.