Invasive disease caused simultaneously by two different serotypes of Streptococcus pneumoniae: a microbiological appreciation

We report a clinical case of a child with an invasive pneumococcal disease caused by two different pneumococcal serotypes that belonged to different sequence types. She was a 15-month-old girl with pneumonia and pleural effusion in which S. pneumoniae colonies with different morphologies grew, one from the blood culture (characteristic greyish appearance) and the other from the pleural fluid (mucoid appearance). The isolate from blood was serotype 22 F (ST698/CC698/GPSC61), while the isolate from the pleural fluid was serotype 3 (ST180/CC180/GPSC12). The patient fully recovered after treatment with intravenous ampicillin followed by oral amoxicillin.

Comparison of next generation technologies and bioinformatics pipelines for capsular typing of Streptococcus pneumoniae

Whole genome sequencing (WGS)-based approaches for pneumococcal capsular typing have become an alternative to serological methods. In silico serotyping from WGS has not yet been applied to long-read sequences produced by third-generation technologies. The objective of the study was to determine the capsular types of pneumococci causing invasive disease in Catalonia (Spain) using serological typing and WGS and to compare the performance of different bioinformatics pipelines using short- and long-read data from WGS. All invasive pneumococcal pediatric isolates collected in Hospital Sant Joan de Déu (Barcelona) from 2013 to 2019 were included. Isolates were assigned a capsular type by serological testing based on anticapsular antisera and by different WGS-based pipelines: Illumina sequencing followed by serotyping with PneumoCaT, SeroBA, and Pathogenwatch vs MinION-ONT sequencing coupled with serotyping by Pathogenwatch from pneumococcal assembled genomes. A total of 119 out of 121 pneumococcal isolates were available for sequencing. Twenty-nine different serotypes were identified by serological typing, with 24F (n = 17; 14.3%), 14 (n = 10; 8.4%), and 15B/C (n = 8; 6.7%) being the most common serotypes. WGS-based pipelines showed initial concordance with serological typing (>91% of accuracy). The main discrepant results were found at the serotype level within a serogroup: 6A/B, 6C/D, 9A/V, 11A/D, and 18B/C. Only one discrepancy at the serogroup level was observed: serotype 29 by serological testing and serotype 35B/D by all WGS-based pipelines. Thus, bioinformatics WGS-based pipelines, including those using third-generation sequencing, are useful for pneumococcal capsular assignment. Possible discrepancies between serological typing and WGS-based approaches should be considered in pneumococcal capsular-type surveillance studies.

Trends in invasive bacterial diseases during the first 2 years of the COVID-19 pandemic: analyses of prospective surveillance data from 30 countries and territories in the IRIS Consortium

BACKGROUND

The Invasive Respiratory Infection Surveillance (IRIS) Consortium was established to assess the impact of the COVID-19 pandemic on invasive diseases caused by Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, and Streptococcus agalactiae. We aimed to analyse the incidence and distribution of these diseases during the first 2 years of the COVID-19 pandemic compared to the 2 years preceding the pandemic.

METHODS

For this prospective analysis, laboratories in 30 countries and territories representing five continents submitted surveillance data from Jan 1, 2018, to Jan 2, 2022, to private projects within databases in PubMLST. The impact of COVID-19 containment measures on the overall number of cases was analysed, and changes in disease distributions by patient age and serotype or group were examined. Interrupted time-series analyses were done to quantify the impact of pandemic response measures and their relaxation on disease rates, and autoregressive integrated moving average models were used to estimate effect sizes and forecast counterfactual trends by hemisphere.

FINDINGS

Overall, 116 841 cases were analysed: 76 481 in 2018-19, before the pandemic, and 40 360 in 2020-21, during the pandemic. During the pandemic there was a significant reduction in the risk of disease caused by S pneumoniae (risk ratio 0·47; 95% CI 0·40-0·55), H influenzae (0·51; 0·40-0·66) and N meningitidis (0·26; 0·21-0·31), while no significant changes were observed for S agalactiae (1·02; 0·75-1·40), which is not transmitted via the respiratory route. No major changes in the distribution of cases were observed when stratified by patient age or serotype or group. An estimated 36 289 (95% prediction interval 17 145-55 434) cases of invasive bacterial disease were averted during the first 2 years of the pandemic among IRIS-participating countries and territories.

INTERPRETATION

COVID-19 containment measures were associated with a sustained decrease in the incidence of invasive disease caused by S pneumoniae, H influenzae, and N meningitidis during the first 2 years of the pandemic, but cases began to increase in some countries towards the end of 2021 as pandemic restrictions were lifted. These IRIS data provide a better understanding of microbial transmission, will inform vaccine development and implementation, and can contribute to health-care service planning and provision of policies.

FUNDING

Wellcome Trust, NIHR Oxford Biomedical Research Centre, Spanish Ministry of Science and Innovation, Korea Disease Control and Prevention Agency, Torsten Söderberg Foundation, Stockholm County Council, Swedish Research Council, German Federal Ministry of Health, Robert Koch Institute, Pfizer, Merck, and the Greek National Public Health Organization.

Distribution of Multidrug-Resistant Invasive Serotypes of Streptococcus pneumoniae during the Period 2007-2021 in Madrid, Spain

After the systematic use of conjugate vaccines, the invasive pneumococcal disease (IPD) was included into the Madrid Notifiable Diseases Surveillance System through an Epidemiological Surveillance Network. Furthermore, Streptococcus pneumoniae was included in the Spanish Plan of Antibiotic Resistance. The aim of this study was to analyse the multidrug-resistant (MDR) phenotype distribution among invasive strains of Streptococcus pneumoniae isolated during 2007-2021 from usually sterile clinical samples in Madrid, Spain. A total number of 7133 invasive pneumococcal isolates were studied during the period from February 2007 to December 2021. Serotyping was characterised using the Pneumotest-Latex and by the Quellung reaction. Antibiotic susceptibility testing to penicillin (PEN), erythromycin (ERY), and levofloxacin (LVX) was performed using the E-test according to the EUCAST guidelines and breakpoints. Combination of non-susceptibility to PEN at standard dosing regimen (PNSSDR), resistance to ERY (ERYR) and to LVX (LVXR) was considered to be multidrug-resistant at standard dosing regimen of penicillin (MRPSDR), whereas the combination of resistance to PEN (PENR), ERYR, and LVXR was considered multidrug-resistant (MDR). The number of MDRPSDR and or MDR strains in the entire population (n = 7133) during the complete period (2007-2021) were 51 (0.7%) and 6 (0.1%), respectively. All MDRPSDR and/or MDR strains belonged to nine serotypes: 19A (n = 13), 15A (n = 12), 9V (n = 12), 14 (n = 7), 24F (n = 3), 15F (n = 1), 19F (n = 1), 6B (n = 1) and 6C (n = 1). Only two serotypes (9V and 19A) were found among MDR strains, and most of them (5/6) belonged to serotype 9V. Only 12.4% of the strains typified as serotype 9V were MDRPSDR and only 5.2% as MDR. The levels of pneumococcal MDRPSDR and/or MDR in this study were low and all six MDR strains were isolated between 2014 and 2018. These results reinforce the importance of monitoring the evolution of non-susceptible serotypes including those with MDR in the coming years, especially after the introduction of new conjugate vaccines of a broader spectrum.

Evolution of Antimicrobial Susceptibility to Penicillin in Invasive Strains of Streptococcus pneumoniae during 2007-2021 in Madrid, Spain

The use of pneumococcal conjugate vaccines has affected the epidemiology and distribution of Streptococcus pneumoniae serotypes causing Invasive Pneumococcal Disease (IPD). The aim of this study was to analyze the evolution of the phenotypical profiles of antimicrobial susceptibility to penicillin (PEN) in all IPD strains isolated in Madrid, Spain, during 2007-2021. In total, 7133 invasive clinical isolates were characterized between 2007 and 2021. Levels of PENR and PNSSDR were 2.0% and 24.2%, respectively. In addition, 94.4% of all the PENR belonged to four serotypes, including 11A (33.6%), 19A (30.8%), 14 (20.3%) and 9V (9.8%). All the strains of serotype 11A, which is a non-PCV13 serotype, were detected after the year 2011. Serotypes 6C, 15A, 23B, 24F, 35B, 19F, 16F, 6B, 23F, 24B, 24A, 15F and a limited number of strains of serogroups 16 and 24 (non-typed at serotype level) were associated with PNSSDR (p < 0.05). PNSSDR strains of non-PCV13 serotypes 11A, 24F, 23B, 24B, 23A and 16F were more frequent from 2014 to 2021. The changes in S. pneumoniae serotype distribution associated with the use of conjugate vaccines had caused in our region the emergence of non-PCV13 pneumococcal strains with different PENR or PNSSDR patterns. The emergence of serotype 11A resistant to penicillin as the most important non-PCV13 serotype is a worrisome event with marked relevance from the clinical and epidemiological perspective.

IE-7925. Contribución de las vacunas antineumocócicas y la pandemia por SARS-CoV-2 en la evolución epidemiológica de la enfermedad neumocócica invasiva en España

Se evaluó la distribución de serotipos de la enfermedad neumocócica invasiva (ENI) por grupos de edad en España, así como el impacto de las vacunas antineumocócicas y el SARS-CoV-2.

Métodos

Estudio descriptivo que incluye 4.297 aislados clínicos de neumococo procedentes de niños y adultos con diagnóstico de ENI y durante el periodo 2019-2022.

Resultados

Se observó una disminución del 58% de los casos de ENI para todas las edades durante el primer año de pandemia por SARS-CoV-2 (2.435 casos en 2019 frente a 1.031 casos en 2020) con una reducción del 22% en 2021 (801 casos) frente a 2020. En los niños, la reducción fue del 53% en 2020 (239 casos en 2019 vs. 112 casos en 2020) con un aumento del 18% en 2021. El serotipo más frecuente en los 3 años fue el 24F. En adultos de 18-64 años y ≥ 65 años se observó una marcada reducción de casos de ENI durante el 2020 en comparación con 2019 (55% para 18-64 años y 61% para ≥ 65 años). Sin embargo, durante el año 2021, la disminución de ENI fue mucho más atenuada en comparación al 2020 (< 28% en ambos grupos de edad) y en lo que llevamos de 2022 han aumentado los casos con respecto al mismo periodo de 2021. En los adultos, el serotipo más frecuente fue el 8 seguido por el 3, representando entre los 2 hasta el 37% de todos los casos de ENI durante 2019-2021.

Conclusiones

La aparición del SARS-CoV-2 en España se asocia a una disminución de los casos de ENI con una recuperación parcial en los niños en el 2021 y en el 2022 tanto en la población pediátrica como adulta. Las nuevas vacunas conjugadas de 15 y 20 serotipos, incrementarán la fracción de la enfermedad prevenible por la vacunación frente a los serotipos circulantes.

A national longitudinal study evaluating the activity of cefditoren and other antibiotics against non-susceptible Streptococcus pneumoniae strains during the period 2004-20 in Spain

BACKGROUND

Surveillance studies including antibiotic resistance and evolution of pneumococcal serotypes are critical to evaluate the susceptibility of commonly used antibiotics and the contribution of conjugate vaccines against resistant strains.

OBJECTIVES

To determine the susceptibility of clinical isolates of Streptococcus pneumoniae with reduced susceptibility to penicillin to a panel of antibiotics during the period 2004-20 and characterize the impact of pneumococcal conjugate vaccines in the evolution of resistant serotypes.

METHODS

We selected 3017 clinical isolates in order to determine the minimal inhibitory concentration to penicillin, amoxicillin, cefotaxime, erythromycin, levofloxacin and oral cephalosporins, including cefditoren, cefixime and cefpodoxime.

RESULTS

The antibiotics with the lowest proportion of resistant strains from 2004 to 2020 were cefditoren (<0.4%), followed by cefotaxime (<5%), penicillin (<6.5%) and levofloxacin (<7%). Among oral cephalosporins, cefixime was the cephalosporin with the highest MIC90 (32 mg/L) and MIC50 (8-16 mg/L) throughout the study, followed by cefpodoxime with highest values of MIC90 (4 mg/L) and MIC50 (2 mg/L) for the majority of the study period. In contrast, cefditoren was the cephalosporin with the lowest MIC90 (1 mg/L) and MIC50 (0.25-0.5 mg/L).

CONCLUSIONS

Cefditoren was the antibiotic with the highest proportion of susceptible strains. Hence, more than 80% of the clinical strains were susceptible to cefditoren throughout the period 2004-20. The proportion of resistant isolates to cefditoren and cefotaxime was scarce, being less than 0.4% for cefditoren and lower than 5% for cefotaxime, despite the increased rates of serotypes not covered by the 13-valent pneumococcal conjugate vaccine.

Pulmonary BCG induces lung-resident macrophage activation and confers long-term protection against tuberculosis

[Figure: see text].

Impact of Biological Therapies on the Immune Response after Pneumococcal Vaccination in Patients with Autoimmune Inflammatory Diseases

Patients with different autoimmune inflammatory diseases (AIID) on biological therapy are at risk of pneumococcal disease. Adults with inflammatory arthropathies, connective tissue diseases, psoriasis, or inflammatory bowel disease on biological therapy such as anti-TNFα, rituximab, tocilizumab, abatacept, or anakinra were included in this study. Patients completed a protocol combining the pneumococcal vaccines PCV13 and PPV23. Immune response against pneumococcal serotypes 1, 3, 7F, 14, 19A, and 19F were assessed evaluating functional antibodies by an opsonophagocytosis killing assay (OPKA). In this study, 182 patients with AIID completed the sequential vaccination protocol. Patients on etanercept tended to achieve OPKA titers against a larger number of serotypes than the rest of patients on other biological therapies, while adalimumab was associated to a lower number of serotypes with OPKA titers. Rituximab was not associated with a worse response when compared with the rest of biological agents. Not glucocorticoids, nor synthetic disease-modifying antirheumatic drugs, interfered with the immune response. OPKA titers against serotype 3 which is one of the most prevalent, was obtained in 44% of patients, increasing up to 58% in those on etanercept. Hence, almost 50% of patients on biological therapy achieved functional antibodies after the administration of a complete pneumococcal vaccination protocol.

1515. Nationwide trends of invasive pneumococcal disease in Spain for the period 2009-2019

Background

Introduction of pneumococcal conjugate vaccines (PCV) is an effective measure to control the invasive pneumococcal disease (IPD) although the emergence of non-vaccine serotypes is of great concern worldwide.

Methods

This study includes national data from IPD cases affecting pediatric and adult population for the period (2009-2019). Data contain 25341 laboratory-confirmed clinical isolates of Streptococcus pneumoniae causing IPD in Spain.

Results

The overall reduction of IPD cases by serotypes included in PCV13 was 88% for children and 67% in adults with a constant increase of IPD cases by serotype 8 in adults since 2015. In children, serotypes 24F (12%), 8 (10%) and 3 (9%) were the most frequent in 2019 whereas in adults, serotypes 3 and 8 accounted for 37% of IPD cases. IPD cases in adults by additional serotypes covered by the 23-valent polysaccharide vaccine (PPV23) have risen constantly within the years, increasing from 19% in 2009 to 52% in 2019. IPD cases by Non-vaccine types in adults (not covered by PCV13 or PPV23) show a moderate increase from 14% in 2009 to 24% in 2019.

Conclusion

Emerging serotypes are observed in Spain with the rise of serotype 24F in children and 8 in adults as a worrisome event.

Disclosures

Jose Yuste, n/a, GSK (Consultant)MSD (Consultant, Research Grant or Support)Pfizer (Consultant)

Nationwide Trends of Invasive Pneumococcal Disease in Spain From 2009 Through 2019 in Children and Adults During the Pneumococcal Conjugate Vaccine Era

Background

Introduction of pneumococcal conjugate vaccines (PCVs) has reduced the disease caused by vaccine serotypes in children, providing herd protection to adults. However, the emergence of nonvaccine serotypes is of great concern worldwide.

Methods

This study includes national laboratory data from invasive pneumococcal disease (IPD) cases that affected pediatric and adult populations during 2009–2019. The impact of implementing different vaccine strategies for immunocompetent adults by comparing Spanish regions that used the 13-valent PCV (PCV13) vs regions that used the 23-valent pneumococcal polysaccharide vaccine (PPV23) was also analyzed for 2017−2019.

Results

The overall reductions in IPD cases by PCV13 serotypes in children and adults were 88% and 59%, respectively, during 2009–2019, with a constant increase in serotype 8 in adults since 2015. IPD cases by additional serotypes covered by PPV23 increased from 20% in 2009 to 52% in 2019. In children, serotype 24F was the most frequent in 2019, whereas serotypes 3 and 8 accounted for 36% of IPD cases in adults. Introduction of PCV13 or PPV23 in the adult calendar of certain Spanish regions reduced the IPD cases by PCV13 serotypes by up to 25% and 11%, respectively, showing a decrease of serotype 3 when PCV13 was used.

Conclusions

Use of PCV13 in children has affected the epidemiology, reducing the burden of IPD in children but also in adults by herd protection; however, the increase in serotype 8 in adults is worrisome. Vaccination with PCV13 in adults seems to control IPD cases by PCV13 serotypes including serotype 3.

Emerging non-13-valent pneumococcal conjugate vaccine (PCV13) serotypes causing adult invasive pneumococcal disease in the late-PCV13 period in Spain

OBJECTIVE

An early reduction of adult invasive pneumococcal disease (IPD) was observed after the 13-valent pneumococcal conjugate vaccine (PCV13) introduction for children in Spain. We analysed the epidemiology of adult IPD in the late-PCV13 period.

METHODS

This was a prospective multicentre study of adult IPD involving six hospitals. Strains were serotyped, genotyped and studied for antimicrobial susceptibility. The late-PCV13 period was compared with the pre- and early-PCV13 periods.

RESULTS

A total of 2197 episodes were collected-949 in 2008-2009, 609 in 2012-2013 and 639 in 2015-2016. The initial decrease of IPD observed (from 12.3/100 000 to 8.1/100 000; 2008-2009 versus 2012-2013) plateaued in 2015-2016 (8.3/100 000). IPD due to PCV13 serotypes decreased (from 7.7 to 3.5 to 2.3/100 000; p < 0.05), whereas IPD caused by non-PCV13 serotypes increased (from 4.5 to 4.6 to 6.0/100 000; p < 0.05). The most frequent serotypes in the late-PCV13 period were: 8 (15.1%), 3 (10.5%), 12F (7.9%) and 9N (5.4%). These serotypes were related to major genotypes: CC53 (59.8%) and CC404 (30.4%) for serotype 8, CC180 (64.1%) and CC260 (28.1%) for serotype 3, CC989 (91.7%) for serotype 12F and CC67 (84.8%) for serotype 9N. Penicillin-non-susceptibility (21.2%) was associated with serotypes 11A (CC156), 14 (CC156) and 19A (CC320), and macrolide-resistance was related to serotypes 24F and 19A. Rates of pneumococcal meningitis remained stable throughout the periods (ranges 0.9, 0.8 and 1.0/100 000).

CONCLUSIONS

The initial decrease of adult IPD observed after PCV13 introduction for children has been balanced by the rise of non-PCV13 serotypes. The spread of antibiotic-resistant lineages related to non-PCV13 serotypes (11A and 24F) could be a threat for the treatment of serious pneumococcal diseases.

Direct identification of pneumococcal serotypes in blood cultures by a PCR-reverse-hybridisation technique

INTRODUCTION

The objective of this study was to assess the performance of a technique (S. PneumoStrip test) based on PCR followed by reverse strip hybridisation for the detection of Streptococcus pneumoniae serotypes directly in blood culture vials.

METHODS

One hundred and ten (110) pairs of isolated strains and their corresponding original blood cultures vials were studied in parallel. Pure isolated strains were conventionally serotyped using latex agglutination and the Quellung reaction. The S. PneumoStrip test was carried out directly in the original blood culture samples.

RESULTS

In 102 cases (92.7%), results of the serotype obtained by Quellung coincided with their corresponding original blood cultures typed by S. PneumoStrip.

CONCLUSIONS

S. PneumoStrip test is a good alternative technique for direct pneumococcal serotyping in blood culture clinical samples.

An Uncharacterized Member of the Gls24 Protein Superfamily Is a Putative Sensor of Essential Amino Acid Availability in Streptococcus pneumoniae

Proteins belonging to the Gls24 superfamily are involved in survival of pathogenic Gram-positive cocci under oligotrophic conditions and other types of stress, by a still unknown molecular mechanism. In Firmicutes, this superfamily includes three different valine-rich orthologal families (Gls24A, B, C) with different potential interactive partners. Whereas the Streptococcus pneumoniae Δgls24A deletion mutant experienced a general long growth delay, the Δgls24B mutant grew as the parental strain in the semisynthetic AGCH medium but failed to grow in the complex Todd-Hewitt medium. Bovine seroalbumin (BSA) was the component responsible for this phenotype. The effect of BSA on growth was concentration-dependent and was maintained when the protein was proteolyzed but not when heat-denatured, suggesting that BSA dependence was related to oligopeptide supplementation. Global transcriptional analyses of the knockout mutant revealed catabolic derepression and induction of chaperone and oligopeptide transport genes. This mutant also showed increased sensibility to cadmium and high temperature. The Δgls24B mutant behaved as a poor colonizer in the nasopharynx of mice and showed 20-fold competence impairment. Experimental data suggest that Gls24B plays a central role as a sensor of amino acid availability and its connection to sugar catabolism. This metabolic rewiring can be compensated in vitro, at the expenses of external oligopeptide supplementation, but reduce important bacteria skills prior to efficiently address systemic virulence traits. This is an example of how metabolic factors conserved in enterococci, streptococci, and staphylococci can be essential for survival in poor oligopeptide environments prior to infection progression.

Comparación agronómica y cualitativa de 3 clones preseleccionados de la variedad tinta Bruñal, en Valladolid (España), en el periodo 2015–2016

La variedad de vid tinta Bruñal está localizada mayoritariamente en la Denominación de Origen (D.O.) Arribes, ubicada en las provincias de Zamora y Salamanca. Presenta características, tanto de tipo morfológico, tal como el tamaño reducido de baya y de racimo, como de tipo cualitativo, tal como el alto contenido de polifenoles en el hollejo, que han propiciado un gran interés para su desarrollo y difusión comercial. El programa de prospección de la variedad Bruñal en la D.O. Arribes, iniciado en 2002 por parte del ITACYL, permitió identificar numerosas cepas de dicha variedad que se encontraban aisladas en viñedos heterogéneos de elevada edad. Tras varios años de trabajo, evaluando aspectos morfológicos y agronómicos en los viñedos originales, se llevó a cabo una primera preselección de cepas procedentes de diferentes viñedos que pudieran presentar cierta variabilidad genética, con el ánimo de iniciar un proceso que desembocase en una selección clonal, una vez que la variedad Bruñal fue incluida en el Registro de Variedades Comerciales de vid del MAGRAMA, el que se reconocen las sinonimias Albarín Tinto y Baboso Tinto (B.O.E. 71, 24-marzo-2011). La primera preselección clonal de Bruñal se llevó a cabo a través de la plantación de 10 cepas de cada uno de los tres clones previamente elegidos en viñedos originales, en una colección del ITACYL ubicada en Valladolid. Se ha llevado a cabo un estudio del comportamiento vegetativo, productivo y cualitativo de los tres clones, injertados sobre 110R, durante el período 2015-2016, sobre cepas, conducidas en espaldera, con un marco de plantación de 2.7 × 1.4 m, y podadas en cordón Royat bilateral. El clon CL-89 resultó más productivo, con un incremento medio del 16% respecto al CL-128, el cual, a su vez, fue un 47% más productivo que el CL-96. Las diferencias observadas en el rendimiento se debieron principalmente a la variación en el peso del racimo, que, a su vez, se debió mayormente al número de bayas del mismo. El peso de madera de poda mostró claras diferencias entre clones, de manera que el clon CL-128 resultó más vigoroso que el CL-96, con un incremento medio de peso del 19% respecto a éste, el cual fue más vigoroso que el CL-89, con un incremento medio del 38% respecto a éste. La variación del peso de sarmiento fue la causa determinante de las diferencias en el peso de madera de poda. En cuanto a la calidad de uva, el clon CL-96 mostró mayor capacidad de intensificación de la maduración tecnológica, acumulando más azúcares e incrementando el pH, aunque reduciendo el IPT. El clon CL-89 presentó cierta tendencia contraria al CL-96, con menos azúcares, ácido málico y potasio, pero sorprendentemente mayor valor de IPT. El clon CL-128 mostró un comportamiento intermedio en general, aunque destacó por su mayor acidez total y contenido en ácido málico. Atendiendo a las diferencias observadas entre clones, existe la posibilidad de conjugarlas con los objetivos de las nuevas plantaciones de Bruñal.

Combination of Antibodies and Antibiotics as a Promising Strategy Against Multidrug-Resistant Pathogens of the Respiratory Tract

The emergence of clinical isolates associated to multidrug resistance is a serious threat worldwide in terms of public health since complicates the success of the antibiotic treatment and the resolution of the infectious process. This is of great concern in pathogens affecting the lower respiratory tract as these infections are one of the major causes of mortality in children and adults. In most cases where the respiratory pathogen is associated to multidrug-resistance, antimicrobial concentrations both in serum and at the site of infection may be insufficient and the resolution of the infection depends on the interaction of the invading pathogen with the host immune response. The outcome of these infections largely depends on the susceptibility of the pathogen to the antibiotic treatment, although the humoral and cellular immune responses also play an important role in this process. Hence, prophylactic measures or even immunotherapy are alternatives against these multi-resistant pathogens. In this sense, specific antibodies and antibiotics may act concomitantly against the respiratory pathogen. Alteration of cell surface structures by antimicrobial drugs even at sub-inhibitory concentrations might result in greater exposure of microbial ligands that are normally hidden or hardly exposed. This alteration of the bacterial envelope may stimulate opsonization by natural and/or specific antibodies or even by host defense components, increasing the recognition of the microbial pathogen by circulating phagocytes. In this review we will explain the most relevant studies, where vaccination or the use of monoclonal antibodies in combination with antimicrobial treatment has demonstrated to be an alternative strategy to overcome the impact of multidrug resistance in respiratory pathogens.

Immunization with LytB protein of Streptococcus pneumoniae activates complement-mediated phagocytosis and induces protection against pneumonia and sepsis

The cell wall glucosaminidase LytB of Streptococcus pneumoniae is a surface exposed protein involved in daughter cell separation, biofilm formation and contributes to different aspects of the pathogenesis process. In this study we have characterized the antibody responses after immunization of mice with LytB in the presence of alhydrogel as an adjuvant. Enzyme-linked immunosorbent assays measuring different subclasses of immunoglobulin G, demonstrated that the antibody responses to LytB were predominantly IgG1 and IgG2b, followed by IgG3 and IgG2a subclasses. Complement-mediated immunity against two different pneumococcal serotypes was investigated using sera from immunized mice. Immunization with LytB increased the recognition of S. pneumoniae by complement components C1q and C3b demonstrating that anti-LytB antibodies trigger activation of the classical pathway. Phagocytosis assays showed that serum containing antibodies to LytB stimulates neutrophil-mediated phagocytosis against S. pneumoniae. Animal models of infection including invasive pneumonia and sepsis were performed with two different clinical isolates. Vaccination with LytB increased bacterial clearance and induced protection demonstrating that LytB might be a good candidate to be considered in a future protein-based vaccine against S. pneumoniae.

Spatial and temporal variability of cv. Tempranillo phenology and grape quality within the Ribera del Duero DO (Spain) and relationships with climate

The aim of this work was to analyze spatial phenology and grape quality variability related to the climatic characteristics within the Ribera del Duero Designation of Origin (DO). Twenty plots planted with cv. Tempranillo and distributed within the DO were analyzed for phenology from 2004 to 2013. Grape quality parameters at ripening (berry weight, sugar content, acidity and pH, and anthocyanins) were analyzed in 26 plots for the period 2003-2013. The relationships between phenology and grape parameters with different climatic variables were confirmed with a multivariate analysis. On average, bud break was April 27(th), bloom June 17(th), and veraison August 12th. However, phenology during the time period showed high variability, with differences between years of up to 21 days for a phenology stage. The earliest dates were observed in dry years (2005, 2006, and to a lesser degree in 2009) while the later phenology dates occurred in the wettest year of the period (2008). High correlations were found between veraison date and temperature variables as well as with precipitation-evapotranspiration recorded during the bloom-veraison period. These effects tended to be higher in the central part of the DO. Grape quality parameters also showed high variability among the dry and the wet years, and the influence of extreme temperatures on color development as well as the effect of available water on acidity were observed.

Emergence of Amoxicillin-Resistant Variants of Spain9V-ST156 Pneumococci Expressing Serotype 11A Correlates with Their Ability to Evade the Host Immune Response

Capsular switching allows pre-existing clones of Streptococcus pneumoniae expressing vaccine serotypes to escape the vaccine-induced immunity by acquisition of capsular genes from pneumococci of a non-vaccine serotype. Here, we have analysed the clonal composition of 492 clinical isolates of serotype 11A causing invasive disease in Spain (2000–2012), and their ability to evade the host immune response. Antibiograms, serotyping and molecular typing were performed. The restriction profiles of pbp2x, pbp1a and pbp2b genes were also analysed. Interaction with the complement components C1q, C3b, C4BP, and factor H was explored whereas opsonophagocytosis assays were performed using a human cell line differentiated to neutrophils. Biofilm formation and the polymorphisms of the major autolysin LytA were evaluated. The main genotypes of the 11A pneumococci were: ST62 (447 isolates, 90.6%), followed by ST6521 (35 isolates, 7.3%) and ST838 (10 isolates, 2.1%). Beta lactam resistant serotype 11A variants of genotypes ST838 and ST6521 closely related to the Spain^9V-ST156 clone were first detected in 2005. A different pattern of evasion of complement immunity and phagocytosis was observed between genotypes. The emergence of one vaccine escape variant of Spain^9V-ST156 (ST6521^11A), showing a high potential to avoid the host immune response, was observed. In addition, isolates of ST6521^11A showed higher ability to produce biofilms than ST838^11A or ST62^11A, which may have contributed to the emergence of this PEN-resistant ST6521^11A genotype in the last few years. The emergence of penicillin-resistant 11A invasive variants of the highly successful ST156 clonal complex merits close monitoring.

Auranofin efficacy against MDR Streptococcus pneumoniae and Staphylococcus aureus infections

BACKGROUND

Auranofin is an FDA-approved, gold-containing compound in clinical use for the oral treatment of rheumatoid arthritis and has been recently granted by the regulatory authorities due to its antiprotozoal properties.

METHODS

A reprofiling strategy was performed with a Streptococcus pneumoniae phenotypic screen and a proprietary library of compounds, consisting of both FDA-approved and unapproved bioactive compounds. Two different multiresistant S. pneumoniae strains were employed in a sepsis mouse model of infection. In addition, an MRSA strain was tested using both the thigh model and a mesh-associated biofilm infection in mice.

RESULTS

The repurposing approach showed the high potency of auranofin against multiresistant clinical isolates of S. pneumoniae and Staphylococcus aureus in vitro and in vivo. Efficacy in the S. pneumoniae sepsis model was obtained using auranofin by the oral route in the dose ranges used for the treatment of rheumatoid arthritis. Thioglucose replacement by alkyl chains showed that this moiety was not essential for the antibacterial activity and led to the discovery of a new gold derivative (MH05) with remarkable activity in vitro and in vivo.

CONCLUSIONS

Auranofin and the new gold derivative MH05 showed encouraging in vivo activity against multiresistant clinical isolates of S. pneumoniae and S. aureus. The clinical management of auranofin, alone or in combination with other antibiotics, deserves further exploration before use in patients presenting therapeutic failure caused by infections with multiresistant Gram-positive pathogens. Decades of clinical use mean that this compound is safe to use and may accelerate its evaluation in humans.

The effects of methionine acquisition and synthesis on Streptococcus pneumoniae growth and virulence

Bacterial pathogens need to acquire nutrients from the host, but for many nutrients their importance during infection remain poorly understood. We have investigated the importance of methionine acquisition and synthesis for Streptococcus pneumoniae growth and virulence using strains with gene deletions affecting a putative methionine ABC transporter lipoprotein (Sp_0149, metQ) and/or methionine biosynthesis enzymes (Sp_0585 - Sp_0586, metE and metF). Immunoblot analysis confirmed MetQ was a lipoprotein and present in all S. pneumoniae strains investigated. However, vaccination with MetQ did not prevent fatal S. pneumoniae infection in mice despite stimulating a strong specific IgG response. Tryptophan fluorescence spectroscopy and isothermal titration calorimetry demonstrated that MetQ has both a high affinity and specificity for L-methionine with a K_D of ∼25 nM, and a ΔmetQ strain had reduced uptake of C₁₄-methionine. Growth of the ΔmetQ/ΔmetEF strain was greatly impaired in chemically defined medium containing low concentrations of methionine and in blood but was partially restored by addition of high concentrations of exogenous methionine. Mixed infection models showed no attenuation of the ΔmetQ, ΔmetEF and ΔmetQ/ΔmetEF strains in their ability to colonise the mouse nasopharnyx. In a mouse model of systemic infection although significant infection was established in all mice, there were reduced spleen bacterial CFU after infection with the ΔmetQ/ΔmetEF strain compared to the wild-type strain. These data demonstrate that Sp_0149 encodes a high affinity methionine ABC transporter lipoprotein and that Sp_0585 – Sp_0586 are likely to be required for methionine synthesis. Although Sp_0149 and Sp_0585-Sp_0586 make a contribution towards full virulence, neither was essential for S. pneumoniae survival during infection.

Effects of Streptococcus pneumoniae strain background on complement resistance

Background

Immunity to infections caused by Streptococcus pneumoniae is dependent on complement. There are wide variations in sensitivity to complement between S. pneumoniae strains that could affect their ability to cause invasive infections. Although capsular serotype is one important factor causing differences in complement resistance between strains, there is also considerable other genetic variation between S. pneumoniae strains that may affect complement-mediated immunity. We have therefore investigated whether genetically distinct S. pneumoniae strains with the same capsular serotype vary in their sensitivity to complement mediated immunity.

Methodology and Principal Findings

C3b/iC3b deposition and neutrophil association were measured using flow cytometry assays for S. pneumoniae strains with different genetic backgrounds for each of eight capsular serotypes. For some capsular serotypes there was marked variation in C3b/iC3b deposition between different strains that was independent of capsule thickness and correlated closely to susceptibility to neutrophil association. C3b/iC3b deposition results also correlated weakly with the degree of IgG binding to each strain. However, the binding of C1q (the first component of the classical pathway) correlated more closely with C3b/iC3b deposition, and large differences remained in complement sensitivity between strains with the same capsular serotype in sera in which IgG had been cleaved with IdeS.

Conclusions

These data demonstrate that bacterial factors independent of the capsule and recognition by IgG have strong effects on the susceptibility of S. pneumoniae to complement, and could therefore potentially account for some of the differences in virulence between strains.

Enhanced in vivo activity of cefditoren in pre-immunized mice against penicillin-resistant S. pneumoniae (serotypes 6B, 19F and 23F) in a sepsis model

BACKGROUND

Specific antibodies are likely to be present before S. pneumoniae infection. We explored cefditoren (CDN) total and free values of serum concentrations exceeding the MIC (t>MIC) related to efficacy in a mice sepsis model, and the effect of specific gammaglobulins on in-vitro phagocytosis and in-vivo efficacy.

METHODOLOGY/PRINCIPAL FINDINGS

We used three pneumococcal isolates (serotype, MIC OF CDN): Strain 1 (6B, 1 microg/ml), Strain 2 (19F, 2 microg/ml) and Strain 3 (23F, 4 microg/ml). Hyperimmune serum (HS) was obtained from mice immunized with heat-inactivated strains. In-vitro, phagocytosis by HS diluted 1/10 in presence/absence of sub-inhibitory concentrations was measured by flow cytometry including fluorescent bacteria and a neutrophil cell line. In-vivo dose-ranging experiments with HS (dilutions 1/2-1/16) and CDN (6.25 mg/kg-100 mg/kg tid for 48 h) were performed to determine the minimal protective dilution/dose (highest survival) and the non-protective highest dilution/dose (highest mortality: HS-np dilution and CDN-np dose) over 7 days. Efficacy of CDN-np in animals pre-immunized with HS-np (combined strategy) was explored and blood bacterial clearance determined. The CDN measured protein binding was 86.9%. In-vitro, CDN significantly increased phagocytosis (vs. HS 1/10). In non pre-immunized animals, t>MIC values for CDN of approximately 35% (total) and approximately 19% (free) were associated with 100% survival. Significant differences in survival were found between HS-np alone (< or = 20%) or CDN-np alone (< or = 20%) vs. the combined strategy (90%, 60% and 60% for Stains 1, 2 and 3), with t>MIC (total/free) of 22.8%/14.3%, 26.8%/16.0%, and 22.4%/12.7% for Strains 1, 2 and 3, respectively. Prior to the second dose (8 h), median bacterial counts were significantly lower in animals surviving vs. dead at day 7.

CONCLUSIONS/SIGNIFICANCE

In mice (CDN protein binding similar to humans) total t>MIC values of approximately 35% (approximately 19% free) were efficacious, with a decrease in the required values in pre-immunized animals. This reinforces that immunoprotection to overcome resistance may provide lifesaving strategies.

Streptococcus pneumoniae resistance to complement-mediated immunity is dependent on the capsular serotype

Streptococcus pneumoniae strains vary considerably in the ability to cause invasive disease in humans, and this is partially associated with the capsular serotype. The S. pneumoniae capsule inhibits complement- and phagocyte-mediated immunity, and differences between serotypes in these effects on host immunity may cause some of the variation in virulence between strains. However, the considerable genetic differences between S. pneumoniae strains independent of the capsular serotype prevent an unambiguous assessment of the effects of the capsular serotype on immunity using clinical isolates. We have therefore used capsular serotype-switched TIGR4 mutant strains to investigate the effects of the capsular serotype on S. pneumoniae interactions with complement. Flow cytometry assays demonstrated large differences in C3b/iC3b deposition on opaque-phase variants of TIGR4(-)+4, +6A, +7F, and +23F strains even though the thicknesses of the capsule layers were similar. There was increased C3b/iC3b deposition on TIGR4(-)+6A and +23F strains compared to +7F and +4 strains, and these differences persisted even in serum depleted of immunoglobulin G. Neutrophil phagocytosis of the TIGR4(-)+6A and +23F strains was also increased, but only in the presence of complement, showing that the effects of the capsular serotype on C3b/iC3b deposition are functionally significant. In addition, the virulence of the TIGR4(-)+6A and +23F strains was reduced in a mouse model of sepsis. These data demonstrate that resistance to complement-mediated immunity can vary with the capsular serotype independently of antibody and of other genetic differences between strains. This might be one mechanism by which the capsular serotype can affect the relative invasiveness of different S. pneumoniae strains.

The effects of PspC on complement-mediated immunity to Streptococcus pneumoniae vary with strain background and capsular serotype

Streptococcus pneumoniae may evade complement activity by binding of factor H (FH), a negative regulator of the alternative pathway, to the surface protein PspC. However, existing data on the effects of FH binding to PspC on complement activity are conflicting, and there is also considerable allelic variation in PspC structure between S. pneumoniae strains that may influence PspC-dependent effects on complement. We have investigated interactions with complement for several S. pneumoniae strains in which the gene encoding PspC has been deleted. The degree of FH binding varied between strains and was entirely dependent on PspC for seven strains. Data obtained with TIGR4 strains expressing different capsular serotypes suggest that FH binding is affected by capsular serotype. Results of immunoblot analysis for C3 degradation products and iC3b deposition assays suggested that FH bound to PspC retained functional activity, but loss of PspC had strikingly varied effects on C3b/iC3b deposition on S. pneumoniae, with large increases on serotype 4, 6A, 6B, and 9V strains but only small increases or even decreases on serotype 2, 3, 17, and 23F strains. Repeating C3b/iC3b assays with TIGR4 strains expressing different capsular serotypes suggested that differences in the effect of PspC on C3b/iC3b deposition were largely independent of capsular serotype and depend on strain background. However, data obtained from infection in complement-deficient mice demonstrated that differences between strains in the effects of PspC on complement surprisingly did not influence the development of septicemia.

Maturation of Streptococcus pneumoniae lipoproteins by a type II signal peptidase is required for ABC transporter function and full virulence

Cell surface lipoproteins are important for the full virulence of several bacterial pathogens, including Streptococcus pneumoniae. Processing of prolipoproteins seems to be conserved among different bacterial species, and requires type II signal peptidase (Lsp) mediated cleavage of the N-terminal signal peptide to form the mature lipoprotein. Lsp has been suggested as a target for new antibiotic therapies, but at present there are only limited data on the function of Lsp for Gram-positive bacterial pathogens. We have investigated the function and role during disease pathogenesis of the S. pneumoniae Lsp, which, blast searches suggest, is encoded by the gene Sp0928. Expression of Sp0928 protected Escherichia coli against the Lsp antagonist globomycin, and proteomics and immunoblot analysis demonstrated that deletion of Sp0928 prevented processing of S. pneumoniae prolipoproteins to mature lipoproteins. These data strongly suggest that Sp0928 encodes the S. pneumoniae Lsp. However, immunoblots of membrane-associated proteins, immunoelectron microscopy and flow cytometry assays all confirmed that in the absence of Lsp, immature lipoproteins were still attached to the cell surface. Despite preservation of lipoprotein attachment to the cell membrane, loss of S. pneumoniae Lsp resulted in several phenotypes associated with impaired lipoprotein function and reduced S. pneumoniae replication in animal models of infection.

Serum amyloid P aids complement-mediated immunity to Streptococcus pneumoniae

The physiological functions of the acute phase protein serum amyloid P (SAP) component are not well defined, although they are likely to be important, as no natural state of SAP deficiency has been reported. We have investigated the role of SAP for innate immunity to the important human pathogen Streptococcus pneumoniae. Using flow cytometry assays, we show that SAP binds to S. pneumoniae, increases classical pathway–dependent deposition of complement on the bacteria, and improves the efficiency of phagocytosis. As a consequence, in mouse models of infection, mice genetically engineered to be SAP-deficient had an impaired early inflammatory response to S. pneumoniae pneumonia and were unable to control bacterial replication, leading to the rapid development of fatal infection. Complement deposition, phagocytosis, and control of S. pneumoniae pneumonia were all improved by complementation with human SAP. These results demonstrate a novel and physiologically significant role for SAP for complement-mediated immunity against an important bacterial pathogen, and provide further evidence for the importance of the classical complement pathway for innate immunity.

Serum amyloid P (SAP) is a protein that is found in high concentrations in the blood, the exact function(s) of which are not clear. However, no known natural state of SAP deficiency has been identified, which suggests that SAP does have a vital role in human health. SAP can bind to molecular patterns found on the surface of bacteria, and it has been proposed that this may mark bacteria for attack by the immune system. We have investigated whether SAP helps protect against an important bacterial pathogen, Streptococcus pneumoniae. We show that SAP binds to different strains of S. pneumoniae, and that this leads to activation of an important component of the immune response called the complement system. Complement is particularly important for defence against S. pneumoniae infections, and using animal models of infection, we demonstrate that loss of SAP makes mice more susceptible to S. pneumoniae pneumonia. These results suggest that SAP helps the immune system to recognise invasion by bacteria and describe a new mechanism required for control of S. pneumoniae infections. This study may help the design of new therapeutic strategies to prevent or treat important bacterial diseases.

Natural human antibodies to pneumococcus have distinctive molecular characteristics and protect against pneumococcal disease

The molecular and functional characteristics of natural antibody from the preimmune repertoire have not been explored in detail in man. We describe seven human IgM monoclonal antibodies selected on the basis of pneumococcal polysaccharide binding that share both molecular and functional characteristics with natural antibody, suggesting a common B cell lineage origin. Unlike class-switched antibodies, which are serotype-specific, the antibodies were polyreactive and bound all pneumococcal polysaccharide capsular serotypes tested. Some bound endogenous antigens, including blood group antigens and intermediate filament proteins. All the antibodies used unmutated heavy chain V (IGHV) that are expressed at an increased frequency in the elderly and in the preimmune repertoire. The CDR3 was characterized by long length (mean aa 18.4 (+/-4.2) and selective use of IGHD6 (P < 0.001) and IGHJ6 (P < 0.01) family genes. The clones expressing IGHV1-69 and IGHV 3-21 provided significant passive protection against invasive pneumococcal disease in vivo.

Roles of the alternative complement pathway and C1q during innate immunity to Streptococcus pyogenes

Complement is important for innate immunity to the common bacterial pathogen Streptococcus pyogenes, but the relative importance of the alternative and classical pathways has not been investigated. Using mice and human serum deficient in either C1q, the first component of the classical pathway, or factor B, an important component of the alternative pathway, we have investigated the role of both pathways for innate immunity to S. pyogenes. C3b deposition on four different strains of S. pyogenes was mainly dependent on factor B. As a consequence opsonophagocytosis of S. pyogenes was reduced in serum from factor B-deficient mice, and these mice were very susceptible to S. pyogenes infection. In contrast, C3b deposition was not dependent on C1q for two of the strains investigated, H372 and H305, yet opsonophagocytosis of all four S. pyogenes strains was impaired in serum deficient in C1q. Furthermore, infection in C1q-deficient mice with strain H372 resulted in a rapidly progressive disease associated with large numbers of bacteria in target organs. These results demonstrate the important role of the alternative pathway and C1q for innate immunity to S. pyogenes and suggest that C1q-mediated innate immunity to at least some strains of S. pyogenes may involve mechanisms that are independent of C3b on the bacteria.

Antibodies to the iron uptake ABC transporter lipoproteins PiaA and PiuA promote opsonophagocytosis of Streptococcus pneumoniae

PiaA and PiuA are the lipoprotein components of the Pia and Piu Streptococcus pneumoniae iron uptake ABC transporters and are required for full virulence in mouse models of infection. Active or passive vaccination with recombinant PiuA and PiaA protects mice against invasive S. pneumoniae disease. In this study we have analyzed the antibody responses and mechanism of protection induced by PiuA and PiaA in more detail. For both proteins, two booster vaccinations induced stronger antibody responses in mice than a single or no booster vaccinations, and 5 mug of protein induced similar levels of antibody responses as 20 mug. Immunoglobulin G (IgG) subclass-specific enzyme-linked immunosorbent assays demonstrated that the antibody response to PiuA and PiaA was predominantly IgG1, with induction of only low levels of IgG2a. Anti-PiaA and anti-PiuA polyclonal rabbit antibodies bound to the surface of live S. pneumoniae when assessed by flow cytometry but did not inhibit growth of S. pneumoniae in cation-depleted medium or bacterial susceptibility to the iron-dependent antibiotic streptonigrin. However, anti-PiaA and anti-PiuA did increase complement-independent and -dependent opsonophagocytosis of different serotypes of S. pneumoniae by the human neutrophil cell line HL60. Hence, vaccination with PiaA and PiuA protects against S. pneumoniae infection by inducing antibodies that promote bacterial opsonophagocytosis rather than inhibiting iron transport.

Additive inhibition of complement deposition by pneumolysin and PspA facilitates Streptococcus pneumoniae septicemia

Streptococcus pneumoniae is a common cause of septicemia in the immunocompetent host. To establish infection, S. pneumoniae has to overcome host innate immune responses, one component of which is the complement system. Using isogenic bacterial mutant strains and complement-deficient immune naive mice, we show that the S. pneumoniae virulence factor pneumolysin prevents complement deposition on S. pneumoniae, mainly through effects on the classical pathway. In addition, using a double pspA-/ply- mutant strain we demonstrate that pneumolysin and the S. pneumoniae surface protein PspA act in concert to affect both classical and alternative complement pathway activity. As a result, the virulence of the pspA-/ply- strain in models of both systemic and pulmonary infection is greatly attenuated in wild-type mice but not complement deficient mice. The sensitivity of the pspA-/ply- strain to complement was exploited to demonstrate that although early innate immunity to S. pneumoniae during pulmonary infection is partially complement-dependent, the main effect of complement is to prevent spread of S. pneumoniae from the lungs to the blood. These data suggest that inhibition of complement deposition on S. pneumoniae by pneumolysin and PspA is essential for S. pneumoniae to successfully cause septicemia. Targeting mechanisms of complement inhibition could be an effective therapeutic strategy for patients with septicemia due to S. pneumoniae or other bacterial pathogens.

Inactivation of Salmonella typhimurium and Escherichia coli O157:H7 in apple juice by a combination of nisin and cinnamon

Pasteurized apple juice with nisin (0, 25, 50, 100, and 200 ppm, wt/vol) and cinnamon (0 and 0.3%, wt/vol) was inoculated with Salmonella Typhimurium and Escherichia coli O157:H7 at 10(4) CFU/ml and stored at 5 and 20 degrees C. Counts on tryptic soy agar (TSA), selective medium (xylose Lysine desoxycholate agar for Salmonella Typhimurium, and MacConkey sorbitol agar for E. coli O157:H7), and thin agar layer (TAL) were determined at 1 h and 1, 3, 7, and 14 days. The TAL method (selective medium overlaid with TSA) was used for recovery of sublethally injured cells. The pathogens were gradually inactivated by the acidic pH of apple juice. Nisin and cinnamon greatly contributed to the inactivation. The killing effect was more marked at 20 degrees C, with counts in all treated samples being undetectable by direct plating in 3 days for Salmonella Typhimurium and 7 days for E. coli O157:H7. Thus, several factors influenced the decrease in counts: low pH, addition of nisin and cinnamon, and storage temperature. The TAL method was as effective as TSA in recovering injured cells of the pathogens. The combination of nisin and cinnamon accelerates death of Salmonella Typhimurium and E. coli O157:H7 in apple juice and so enhances the safety of the product.

Beta-lactam activity against resistant pneumococcal strains is enhanced by the immune system

Pandemic resistance in Streptococcus pneumoniae is compromising antibiotic activity. Antibiotics that act on the cell wall, such as beta-lactams, may have a combined effect with the immune system against S. pneumoniae, since both act on the bacterial envelope. This combined effect can be studied in vitro or in vivo with respect to bacterial killing, since lysis is the end-point of both beta-lactams and the immune system. We review here the in vitro increase in the bactericidal activity of aminopenicillins by non-specific immunity (complement and polymorphonuclear leucocytes). Few data are available on the collaboration of specific immunity and beta-lactams. We also review the effect of the presence of specific antibodies on the in vivo T > MIC needed for the therapeutic efficacy of amoxicillin, and on blood bacterial clearance in animal models. The effect that immunity has on pharmacodynamic parameters, such as T > MIC, in non-human studies may be used as a tool to predict the effect of these pharmacodynamic variations in overcoming resistance and its selection, in the context of increasing the use of pneumococcal conjugated vaccines.

Inactivation of Listeria monocytogenes Scott A 49594 in apple juice supplemented with cinnamon

Normal (pH 3.7) and adjusted (pH 5.0) pasteurized apple juice containing cinnamon (0, 0.1, 0.2, and 0.3%) was inoculated with Listeria monocytogenes Scott A 49594 at 10(4) CFU/ml and stored at 5 and 20 degrees C for 7 days. Counts on tryptic soy agar (TSA), modified Oxford (MOX) medium, and thin agar layer (TAL) were determined at 1 h and 1, 3, and 7 days. The TAL method (MOX medium overlaid with TSA) was used for the recovery of injured cells. In apple juice, both at normal and adjusted pH, with any doses of cinnamon, no L. monocytogenes (a 4.6-log CFU/ml reduction) was detected after 1 h of storage at both temperatures, and no growth occurred at any points of storage. Therefore, cinnamon by itself (regardless of pH) had a pronounced killing effect. A further enrichment step with brain heart infusion agar showed that L monocytogenes was completely inactivated in apple juice stored at 20 degrees C, except in pH 5.0 samples with 0.1% of cinnamon. The TAL method was as effective as TSA in recovering injured cells of L. monocytogenes. Cinnamon considerably inactivates L. monocytogenes in apple juice and thus enhances the safety of this product.

Modification of bacteraemia by specific antibodies and relation with mortality in a pneumococcal mouse sepsis model

The relationship between mortality and the bacteraemic profile was investigated in a pneumococcal (serotype 6B) sepsis BALB/c mouse model where animals received protection by specific hyperimmune serum. A single intraperitoneal dose of hyperimmune serum obtained from mice immunized with the heat-inactivated strain was administered (non-diluted or diluted to 1/4 or to 1/16) to 5-mice study groups 1 h prior to intraperitoneal inoculation with the infective inoculum (3.57 x 108 cfu/ml). Blood cultures were performed daily over 15 days, with 8 microl of blood being collected from the tail vein; the samples were resuspended in Todd-Hewitt broth containing 10% trisodium citrate and plated onto blood agar for colony counting. Animals included in the control group received placebo (PBS). Mortality was 100% in control animals within the first 48 h. Hyperimmune serum decreased and delayed mortality in a dose-related trend, producing 100%, 80%, 60% and 40% survival rates at 72, 96, 144 and 360 h, with non-diluted serum. Bacteraemic profiles with maximum colony counts > or =5 x 107 cfu/ml in blood during the follow-up period were related to > or =65% probability of death, regardless of the serum dilution administered.

Effects of specific antibodies against Streptococcus pneumoniae on pharmacodynamic parameters of beta-lactams in a mouse sepsis model

A dose-ranging study to investigate the in vivo effects of the presence of specific antibodies on the efficacy of beta-lactam treatment of sepsis caused by Streptococcus pneumoniae (non-beta-lactam-susceptible serotype 6B isolate) was performed with a BALB/c mouse model. Hyperimmune serum was obtained from mice immunized with the heat-inactivated strain. The rate of mortality was 100% in nontreated animals in the absence of specific antibodies. A single injection of a one-half or one-quarter dilution of hyperimmune serum produced 60 to 40% survival rates. In the absence of specific antibodies, the minimal effective doses of amoxicillin and cefotaxime that produced survival rates of 100 and 80% were 25 and 50 mg/kg of body weight (three times a day for up to six doses), respectively. These doses produced times that the levels in serum remained above the MIC (deltaT > MICs) approximately 30% of the dosing interval. When specific antibodies were present (by administration of a one-half or one-quarter dilution of hyperimmune serum), the minimal effective doses of the antibiotics were 3.12 and 6.25 mg/kg ( approximately 8 times lower), with the deltaT > MICs being approximately 3 and 5% of the dosing interval for amoxicillin and cefotaxime, respectively. This in vivo combined pharmacodynamic effect offers possibilities that can be used to address penicillin resistance.

Beta-lactam modification of the bacteraemic profile and its relationship with mortality in a pneumococcal mouse sepsis model

A sepsis BALB/c mice model was used to investigate the relationship between mortality and the bacteraemic profile produced by a serotype 6B Streptococcus pneumoniae clinical isolate (MIC/MBC of amoxicillin 4/4 mg/L and of cefotaxime 2/4 mg/L). Animals were treated subcutaneously with doses of amoxicillin or cefotaxime ranging from 6.25 to 50 mg/kg tds for 48 h, starting 1 h after intraperitoneal inoculation (2 x 10(7) cfu/mouse). Blood cultures were carried out daily over 15 days. A survival rate of 100% was obtained with amoxicillin 25 mg/kg and of 60% with cefotaxime 50 mg/kg. A statistically significant (P = 0.012) relationship was found between the maximum cfu/mL in blood and mortality. A maximum log cfu/mL of 6.5 was associated with an 84% probability of death.