Streptococcus agalactiae: prevention and vaccine development.

Streptococcus agalactiae, group B Streptococcus (SGB), is the most important cause of morbi-mortality among newborn population, and an important pathogen among immunossupressed adult patients. Despite the advances in the treatment and prevention of neonatal infections as a consequence of implementation of national and international recommendations for prevention of infection, there are still some improvements for the final control of the disease. In this sense, the vaccination against SGB could be an effective measure for the prevention of disease in those cases where intrapartum prophylaxis is not useful and in adult patients with risk factors for invasive infection due to SGB. This review summarizes the efforts made until now in order to establish the control of the infection, and brings some information on the current state-of-the art of vaccines against SGB, in which different strategies in their design have been used.

Prevention of group B streptococcal neonatal disease revisited. The DEVANI European project.

The purpose of this paper was to present the current knowledge on the prevention of group B streptococcus (GBS) neonatal infections and the status of prevention policies in European countries and to present the DEVANI pan-European program, launched in 2008. The aim of this program was to assess the GBS neonatal infection burden in Europe, to design a new vaccine to immunize neonates against GBS infections, to improve the laboratory performance for the diagnosis of GBS colonization and infection, and to improve the methods for the typing of GBS strains. The current guidelines for GBS prevention in different countries were ascertained and a picture of the burden before and after the instauration of prevention policies has been drawn. After the issue of the Centers for Disease Control and Prevention (CDC) guidelines, many European countries have adopted universal screening for the GBS colonization of pregnant women and intrapartum prophylaxis to colonized mothers. Nevertheless, some European countries continue advocating the risk factor approach to GBS prevention. Most European countries have implemented policies to prevent GBS neonatal infections and the burden of the disease has decreased during the last several years. Nevertheless, further steps are necessary in order to develop new strategies of prevention, to improve microbiological techniques to detect GBS colonization and infection, and to coordinate the prevention policies in the EU.

Consideraciones actuales sobre la prevención de la transmisión vertical del estreptococo β - hemolítico del grupo B / Current considerations on the prevention of vertical transmission of group B beta´hemolytic streptococcus

La sepsis bacteriana del neonato es un síndrome clínico caracterizado por signos de infección sistémica acompañados de bacteriemia. Denominamos infección neonatal de transmisión vertical aquella que es transmitida por la madre al feto o al recién nacido (RN) durante el embarazo, el parto el período neonatal. Las bacterias implicadas son las que se encuentran en el canal del parto que en su mayoría son de baja virulencia, pero ocasionalmente pueden infectar a la madre o al RN. Actualmente el principal agente de infección bacteriana de transmisión vertical es el Streptococcus agalactiae (estreptococo β – hemolítico del grupo B) (EGB), siendo menos frecuente la infección por Escherichia coli y otros bacilos gran negativos y se suele observar, sobre todo, en RN prematuros y de muy bajo peso (AU)

Neonatal bacterial sepsis is a clinical syndrome characterized by signs of systemic infection accompanied by bacteriemia. Neonatal infection due to vertical transmission refers to that which is transmitted by the mother to the fetus or to the newborn (NB) during the pregnancy, delivery and neonatal period. The bacterias involved are those found in the delivery canal, which mostly have low virulence, but they may sometimes infect the mother or NB. Currently the primary agent of vertical transmission bacterial infection is the Streptococcus agalactiae (group B β-hemolytic streptococcus) (EGB) infection by Escherichia coli and other gram negative bacilli being less frequent and it is generally observed, above all, in premature very low weight NB (AU)

Probable early-onset group B streptococcal neonatal sepsis: a serious clinical condition related to intrauterine infection.

BACKGROUND: The estimated incidence of true early-onset group B streptococcal (GBS) neonatal infection is based on positive GBS blood or cerebrospinal fluid (CSF) culture results, but the real burden of disease is underestimated owing to the high incidence of culture-negative sepsis possibly because of antibiotic administration to the mother. OBJECTIVE: To examine the rate of probable early-onset GBS neonatal sepsis and to assess its impact on total GBS neonatal disease. DESIGN: A multicentre longitudinal prospective surveillance of 107,021 deliveries. RESULTS: The rates of culture-proven and probable early-onset GBS sepsis were 0.39 and 0.47 per 1000 live births, respectively. Of great concern was the finding of three deaths related to the infection in the group with probable early-onset GBS sepsis. CONCLUSIONS: The use of chemoprophylaxis in GBS-colonised pregnant women, especially when it is incomplete, may not be sufficient to prevent clinical neonatal infection, but may inhibit the growth of GBS in blood and CSF cultures. In assessing the effectiveness of GBS prophylaxis, it is advisable to consider the incidence of culture-positive and probable culture-negative GBS neonatal infection.

Genetic diversity of Streptococcus agalactiae strains colonizing the same pregnant woman.

Pulsed-field gel electrophoresis (PFGE) of SmaI-DNA digests and serotyping was performed on 15 colonies of Streptococcus agalactiae (GBS) from each of 30 vaginal rectal colonized women. Five distinct GBS serotypes were observed among the 30 specimens (Ia, Ib, II, III and V). In 29 of the 30 samples, the same serotype was observed among all 15 colonies; in the remaining specimen, the 15 colonies yielded two serotypes (II and V). The PFGE profiles of all colonies in 27 of the 30 subjects were indistinguishable within each subject. In the remaining women, different DNA profiles were identified among the colonies in each specimen, one of whom carried two different serotypes. Furthermore, strains of the same serotype belonging to different women were genetically heterogeneous.

Human rhabdomyosarcoma cells for rapid detection of enteroviruses by shell-vial assay.

The ability of the RD (rhabdomyosarcoma) and MRC-5 cell-lines to detect enteroviruses in 33 clinical samples (cerebrospinal fluid, stools and throat swabs) was evaluated. The samples had previously tested enterovirus-positive by traditional tube-culture and had been frozen after their initial processing. By traditional tube-culture, 100 and 85 % of samples were positive for enterovirus in RD and MRC-5 cells, respectively. By rapid shell-vial assay, 94 and 45.5 % were positive after 48 h incubation in RD and MRC-5 cells, respectively. RD cells supported growth of all enterovirus serotypes, whereas MRC-5 cells were not able to detect any of the three coxsackieviruses that were found (one coxsackievirus A9 and two coxsackievirus B5). The shell-vial assay with RD cell-lines may be a useful tool for rapid diagnosis of enteroviral infection.

Pigment production by Streptococcus agalactiae in quasi-defined media.

A quasi-defined medium that supports the growth of Streptococcus agalactiae as pigmented colonies has been developed. The medium contains starch, a peptic digest of albumin, amino acids, nucleosides, vitamins, and salts. The presence of free cysteine, which could be replaced with other sulphur-containing compounds and to a lesser degree by reducing agents, was required for pigment formation.

Clinical significance of polymicrobial versus monomicrobial bacteremia involving Pseudomonas aeruginosa.

The objective of this study was to examine the clinical significance of polymicrobial bacteremia involving Pseudomonas aeruginosa. Two hundred forty-eight episodes of Pseudomonas aeruginosa bacteremia, 43 of which were polymicrobic, were studied prospectively over a 6-year period. Three sets of blood cultures were obtained for each patient. Positive results for all three blood cultures were found more frequently in patients with polymicrobial infection, who were older than those with monomicrobial infection. Patients with polymicrobial bacteremia also were worse clinically and developed shock more frequently. Crude mortality was higher in patients with polymicrobial infection. A multivariate analysis revealed three variables significantly and independently associated with polymicrobial Pseudomonas aeruginosa bacteremia: higher age, poor clinical status of the patient, and positive results for all blood cultures obtained.

[Liver abscess caused by Klebsiella pneumoniae in diabetic patients]. / Absceso hepático por Klebsiella pneumoniae en pacientes diabéticos.

Pyogenic liver abscess are macroscopic collections of pus within the hepatic parenchyma after a bacterial infection. These infections are usually polymicrobial in nature, and in most occasions due to biliary tract diseases or cryptogenetic in origin. Monomicrobial hepatic abscess caused by Klebsiella pneumoniae are uncommon lesions in western countries. These lesions are associated with underlying diseases, particularly diabetes mellitus, and are frequently complicated with septic metastasis. We report here three cases of monomicrobial liver abscess caused by Klebsiella pneumoniae in diabetic patients, without septic metastasis and a favourable outcome.

Use of Granada medium to detect group B streptococcal colonization in pregnant women.

Direct inoculation onto Granada medium (GM) in plates and tubes was compared to inoculation into a selective Todd-Hewitt broth (with 8 microg of gentamicin per ml and 15 microg of nalidixic acid per ml) for detection of group B streptococci (GBS) in pregnant women with 800 vaginal and 450 vaginoanorectal samples. Comparatively, GM was found to be as sensitive as the selective broth for the detection of GBS in vaginal specimens and more sensitive than selective broth for the detection of GBS in vaginoanorectal samples (96 versus 82%). The use of GM improved the time to reporting of a GBS-positive result by at least 24 h and reduced the direct cost of screening. We have also found that the inconvenience of anaerobic incubation of GM plates can be avoided when a cover slide is placed upon the inoculum, because aerobic incubation in GM plates with cover slides causes GBS to develop the same pigmentation that it develops with incubation under anaerobic conditions. These data support the routine use of GM plates or tubes as a more accurate, easier, and cheaper method of identification of GBS-colonized women compared to the enrichment broth technique.

Rapid detection of respiratory viruses by shell vial assay using simultaneous culture of HEp-2, LLC-MK2, and MDCK cells in a single vial.

A shell vial assay with simultaneous culture of HEp-2, LLC-MK2, and MDCK cell lines in a single tube (CoHLM SV assay) was compared with traditional tube culture (TC) for the detection of the main respiratory viruses in 358 nasal wash specimens. A total of 170 strains were isolated from 168 virus-positive samples. A total of 94. 1% of the strains (160 strains; 128 respiratory syncytial viruses and 32 other viruses) were detected by the CoHLM SV assay in 48 h, whereas 98.2% of the strains (167 strains; 132 respiratory syncytial viruses and 35 other viruses) were detected by TC in a mean time of 6 days. The CoHLM SV assay may be useful for the rapid detection of respiratory viruses.

Identification of a peptide from mammal albumins responsible for enhanced pigment production by group B streptococci.

The peptide from peptones responsible for enhanced pigment production by Streptococcus agalactiae in culture media has been isolated from a peptic digest of human albumin and has been identified as Ile-Ala-Arg-Arg-His-Pro-Tyr-Phe. The related heptapeptide lacking the N-terminal Ile also had pigment-enhancing activity. A sequence similarity search showed that these sequences are present only in mammal albumins.

Infections due to sandfly fever virus serotype Toscana in Spain.

Of the sandfly fever viruses known to be human pathogens (serotypes Toscana [TOS], Sicilian [SFS], and Naples [SFN]), only TOS has demonstrated neurotropic activity. Infections by TOS have been reported in Mediterranean countries, but the virus was previously isolated only in Italy and Portugal. We isolated 15 strains of TOS between 1988 and 1996 from the cerebrospinal fluid of patients with acute aseptic meningitis in Granada, Spain. This finding led us to study the presence of antibodies to TOS, SFS, and SFN in 1,181 adults and 87 children from different regions of Spain. We found that the prevalence of antibodies to these viruses was 26.2%, 2.2, and 11.9%, respectively; these rates imply that TOS infections are common in Spain.

Timing of intrapartum ampicillin and prevention of vertical transmission of group B streptococcus.

OBJECTIVE: To evaluate the relationship between the time elapsed from the administration of ampicillin prophylaxis to delivery and its efficacy in interrupting intrapartum transmission of group B streptococcus. METHODS: During the 12-month study period, all women who came to the Virgen de las Nieves Hospital (Granada, Spain) for delivery were screened for group B streptococcus vaginal carriage by a pigment-detection culture-based procedure. Colonized women were treated with ampicillin (2 g intravenously), and the interval between ampicillin administration and delivery was recorded. Newborns from colonized mothers also were screened to detect group B streptococcus colonization. RESULTS: During the study period, 4525 women were admitted to the hospital for delivery and screened for group B streptococcus vaginal colonization. Group B streptococcus was detected in 543 women (12%), of whom 454 gave birth vaginally to 454 liveborn infants. Intrapartum ampicillin was given to 201 of these 454 women (44%), and 10% of the newborns from mothers who received intrapartum ampicillin prophylaxis were colonized by group B streptococcus. The relationship between timing of ampicillin administration and rate of neonatal group B streptococcal transmission was as follows: less than 1 hour before delivery, 46%; 1-2 hours, 29%; 2-4 hours, 2.9%; and more than 4 hours, 1.2%. Among the 253 mothers who received no intrapartum prophylaxis, colonization was found in 120 of their newborns (47%). CONCLUSION: When the time between the start of ampicillin prophylaxis and delivery is at least 2 hours, vertical transmission of group B streptococcus is minimized.

Endocarditis caused by nonhemolytic group B streptococcus.

We report a case of bacterial endocarditis caused by nonhemolytic group B streptococcus (GBS) in a 67-year-old man with no predisposing risk factors. Nonhemolytic GBS strains rarely cause illness and are usually detected in perinatal infections. We believe this to be the first reported case of endocarditis caused by a nonhemolytic strain of GBS.

Identification of serum and urine proteins responsible for enhanced pigment production by group B streptococci as amylases.

The serum and urine proteins responsible for enhanced pigment production in Streptococcus agalactiae in culture media were purified by chromatography and were identified as amylases by comparison of their amino acid composition with that calculated for proteins with known sequences. Similar pigment-enhancing activity was displayed by other amylases of nonanimal origin and by maltooligosaccharides.