The changing epidemiology of community-acquired pneumonia: nationwide register-based study in Sweden.

BACKGROUND: There is limited evidence on the impact of pneumococcal conjugate vaccine childhood immunization programmes (PCV-CIP) on community-acquired pneumonia (CAP) in individuals with underlying diseases. METHODS: A nationwide cohort study using Swedish health registers to assess the incidence of hospitalization with all-cause (AC-CAP) and pneumococcal or lobar (PL-CAP) CAP between 2005 and 2015, in relation to PCV-CIP introduction in 2007-09. RESULTS: In total, 303 691 episodes of AC-CAP occurred, of which 14 225 were PL-CAP. Comparing before (2005-06) with after (2014-15) PCV-CIP, relative incidence reductions were 36% (95% Confidence Interval 32-40), 20% (14-25) and 16% (11-22) of AC-CAP for age groups < 2, 2-4 and 5-17 years, respectively, with similar reductions in young children with and without comorbidities. The reductions were more pronounced for PL-CAP. In the age groups 40-64, 65-74, 75-84 and ≥85 years there were relative increases of 11% (8-14), 18% (15-22), 15% (12-17) and 30% (27-34) of AC-CAP, respectively, but these increases were attenuated after adjustment for admittance practices using four control conditions. In adults with comorbidities, there was an increase in incidence of AC-CAP, and PL-CAP, in contrast to adults without reported underlying diseases where the incidence was stable or diminished for some age groups. Over the study period, there was an increased proportion of pneumonia patients with underlying diseases in all ages. CONCLUSION: This emphasizes that direct preventive interventions should be targeted towards individuals with underlying diseases. Future studies should investigate reasons for the observed increased risk in adults with comorbidities, for example due to pneumococcal nonvaccine serotypes, or other pathogens, preferentially affecting subjects with underlying diseases.

Pathogenesis and prevention of risk of cardiovascular events in patients with pneumococcal community-acquired pneumonia.

It is now well recognized that cardiovascular events (CVE) occur quite commonly, both in the acute phase and in the long-term, in patients with community-acquired pneumonia (CAP). CVE have been noted in up to 30% of patients hospitalized with all-cause CAP. One systematic review and meta-analysis of hospitalized patients with all-cause CAP noted that the incidence rates for overall cardiac events were 17.7%, for incident heart failure were 14.1%, for acute coronary syndromes were 5.3% and for incident cardiac arrhythmias were 4.7%. In the case of pneumococcal CAP, almost 20% of patients studied had one or more of these cardiac events. Recent research has provided insights into the pathogenesis of the acute cardiac events occurring in pneumococcal infections. With respect to the former, key involvements of the major pneumococcal protein virulence factor, pneumolysin, are now well documented, whilst systemic platelet-driven neutrophil activation may also contribute. However, events involved in the pathogenesis of the long-term cardiovascular sequelae remain largely unexplored. Emerging evidence suggests that persistent antigenaemia may predispose to the development of a systemic pro-inflammatory/prothrombotic phenotype underpinning the risk of future cardiovascular events. The current manuscript briefly reviews the occurrence of cardiovascular events in patients with all-cause CAP, as well as in pneumococcal and influenza infections. It highlights the close interaction between influenza and pneumococcal pneumonia. It also includes a brief discussion of mechanisms of the acute cardiac events in CAP. However, the primary focus is on the prevalence, pathogenesis and prevention of the longer-term cardiac sequelae of severe pneumococcal disease, particularly in the context of persistent antigenaemia and associated inflammation.

Aetiology of lower respiratory tract infection in adults in primary care: a prospective study in 11 European countries.

OBJECTIVES: To describe the role of bacteria (including bacterial resistance), viruses (including those recently described) and mixed bacterial-viral infections in adults presenting to primary care with lower respiratory tract infection (LRTI). METHODS: In all, 3104 adults with LRTI were enrolled, of whom 141 (4.5%) had community-acquired pneumonia (CAP), and 2985 matched controls in a prospective study in 16 primary care networks in Europe, and followed patients up at 28-35 days. We detected Streptococcus pneumoniae and Haemophilus influenzae and assessed susceptibility, atypical bacteria and viruses. RESULTS: A potential pathogen was detected in 1844 (59%) (in 350 (11%) bacterial pathogens only, in 1190 (38%) viral pathogens only, and in 304 (10%) both bacterial and viral pathogens). The most common bacterial pathogens isolated were S. pneumoniae (5.5% overall, 9.2% in CAP patients) and H. influenzae (5.4% overall, 14.2% in CAP patients). Less than 1% of S. pneumoniae were highly resistant to penicillin and 12.6% of H. influenzae were ß-lactamase positive. The most common viral pathogens detected were human rhinovirus (20.1%), influenza viruses (9.9%), and human coronavirus (7.4%). Influenza virus, human parainfluenza viruses and human respiratory syncytial virus as well as human rhinovirus, human coronavirus and human metapneumovirus were detected significantly more frequently in LRTI patients than in controls. CONCLUSIONS: A bacterial pathogen is identified in approximately one in five adult patients with LRTI in primary care, and a viral pathogen in just under half, with mixed infections in one in ten. Penicillin-resistant pneumococci and ß-lactamase-producing H. influenzae are uncommon. These new findings support a restrictive approach to antibiotic prescribing for LRTI and the use of first-line, narrow-spectrum agents in primary care.

Coeliac disease and invasive pneumococcal disease: a population-based cohort study.

Severe infections are recognized complications of coeliac disease (CD). In the present study we aimed to examine whether individuals with CD are at increased risk of invasive pneumococcal disease (IPD). To do so, we performed a population-based cohort study including 29 012 individuals with biopsy-proven CD identified through biopsy reports from all pathology departments in Sweden. Each individual with CD was matched with up to five controls (n = 144 257). IPD events were identified through regional and national microbiological databases, including the National Surveillance System for Infectious Diseases. We used Cox regression analyses to estimate hazard ratios (HRs) for diagnosed IPD. A total of 207 individuals had a record of IPD whereas 45/29 012 had CD (0·15%) and 162/144 257 were controls (0·11%). This corresponded to a 46% increased risk for IPD [HR 1·46, 95% confidence interval (CI) 1·05-2·03]. The risk estimate was similar after adjustment for socioeconomic status, educational level and comorbidities, but then failed to attain statistical significance (adjusted HR 1·40, 95% CI 0·99-1·97). Nonetheless, our study shows a trend towards an increased risk for IPD in CD patients. The findings support results seen in earlier research and taking that into consideration individuals with CD may be considered for pneumococcal vaccination.

Lung epithelium and myeloid cells cooperate to clear acute pneumococcal infection.

The Gram-positive bacterium Streptococcus pneumoniae causes life-threatening infections, especially among immunocompromised patients. The host's immune system senses S. pneumoniae via different families of pattern recognition receptors, in particular the Toll-like receptor (TLR) family that promotes immune cell activation. Yet, while single TLRs are dispensable for initiating inflammatory responses against S. pneumoniae, the central TLR adapter protein myeloid differentiation factor 88 (MyD88) is of vital importance, as MyD88-deficient mice succumb rapidly to infection. Since MyD88 is ubiquitously expressed in hematopoietic and non-hematopoietic cells, the extent to which MyD88 signaling is required in different cell types to control S. pneumoniae is unknown. Therefore, we used novel conditional knockin mice to investigate the necessity of MyD88 signaling in distinct lung-resident myeloid and epithelial cells for the initiation of a protective immune response against S. pneumoniae. Here, we show that MyD88 signaling in lysozyme M (LysM)- and CD11c-expressing myeloid cells, as well as in pulmonary epithelial cells, is critical to restore inflammatory cytokine and antimicrobial peptide production, leading to efficient neutrophil recruitment and enhanced bacterial clearance. Overall, we show a novel synergistic requirement of compartment-specific MyD88 signaling in S. pneumoniae immunity.

Human isolates of Listeria monocytogenes in Sweden during half a century (1958-2010).

Isolates of Listeria monocytogenes (n = 932) isolated in Sweden during 1958-2010 from human patients with invasive listeriosis were characterized by serotyping and pulsed-field gel electrophoresis (PFGE) (AscI). Of the 932 isolates, 183 different PFGE types were identified, of which 83 were each represented by only one isolate. In all, 483 serovar 1/2a isolates were distributed over 114 PFGE types; 90 serovar 1/2b isolates gave 32 PFGE types; 21 serovar 1/2c isolates gave nine PFGE types; three serovar 3b isolates gave one PFGE type; and, 335 serovar 4b isolates gave 31 PFGE types. During the 1980s in Sweden, several serovar 4b cases were associated with the consumption of European raw soft cheese. However, as cheese-production hygiene has improved, the number of 4b cases has decreased. Since 1996, serovar 1/2a has been the dominant L. monocytogenes serovar in human listeriosis in Sweden. Therefore, based on current serovars and PFGE types, an association between human cases of listeriosis and the consumption of vacuum-packed gravad and cold-smoked salmon is suggested.

Oral bacterial community dynamics in paediatric patients with malignancies in relation to chemotherapy-related oral mucositis: a prospective study.

The role of oral bacteria in the development of chemotherapy-related oral mucositis has not been fully elucidated. This study aimed to investigate oral bacterial community diversity and dynamics in paediatric patients with malignancies in relation to the occurrence of oral mucositis. Patients with malignancies (n = 37) and reference individuals without known systemic disorders (n = 38) were recruited. For patients, oral bacterial samples were taken from mucosal surfaces both at the time of malignancy diagnosis and during chemotherapy. If oral mucositis occurred, samples were taken from the surface of the mucositis lesions. Oral mucosal bacterial samples were also taken from reference individuals. All samples were assessed using a 16S ribosomal RNA gene 454 pyrosequencing method. A lower microbial diversity (p < 0.01) and a higher intersubject variability (p < 0.001) were found in patients as compared with reference individuals. At the time of malignancy diagnosis (i.e. before chemotherapy) patients that later developed mucositis showed a higher microbial diversity (p < 0.05) and a higher intersubject variability (p < 0.001) compared with those without mucositis. The change of bacterial composition during chemotherapy was more pronounced in patients who later developed mucositis than those without mucositis (p < 0.01). In conclusion, we found a higher microbial diversity at the time of malignancy diagnosis in patients who later develop oral mucositis and that these patients had a more significant modification of the bacterial community by chemotherapy before the occurrence of mucositis. These findings may possibly be of clinical importance in developing better strategies for personalized preventive management.

Increased incidence of invasive group A streptococcal infections in Sweden, January 2012-February 2013.

The incidence of invasive group A streptococcal infections in Sweden was 6.1 per 100,000 population in 2012, the highest since the disease became notifiable in 2004. Furthermore, January and February 2013 marked a dramatic increase of cases notified, partly explainable by an increase of emm1/T1 isolates, a type previously shown to cause severe invasive disease more often than other types. Healthcare providers in Sweden and health authorities in neighbouring countries have been informed about this increase.

Description of macrolide-resistant and potential virulent clones of Streptococcus pyogenes causing asymptomatic colonization during 2000-2006 in the Lisbon area.

The asymptomatic oropharyngeal colonization rate by Streptococcus pyogenes was 10.7% in children (901 among 8,405 children 0-16 years old) and 3.3% in adults (37 among 1,126 households of children) in the Lisbon area during 2000-2006. Macrolide-resistant S. pyogenes from children (n = 149) was variable with time: 9.8-10.7% in 2000-2002, 28.1% in 2003, 19.6-2.7% in 2004-2005 and 14.6% in 2006. Eight lineages (97.3% of isolates) were identified based on at least 80% similarity of PFGE patterns, T types, emm types and multilocus sequence types (ST). The elevated frequency of macrolide resistance was associated with M phenotype lineages I (emm12/ST36) and V (emm4, emm75/ST39 and a novel emmstMrp6 type) and with one cMLS(B) lineage IV (emm28/ST52) known to be associated with upper respiratory tract and invasive infections. Significant associations (p < 0.05) between emm type/virulence genotype were found, such as emm1/speA (+) ssa (-), emm4/ssa (+) prtF1 (+), emm12/speA (-) ssa (-). The high prevalence (>20%) of speC, prtF1 or ssa was probably caused either by clonal dissemination (speC), or to horizontal gene transfer events (prtF1 and ssa). This report contributes to a better understanding of the molecular epidemiology and evolution of macrolide-resistant S. pyogenes causing symptom-free oropharyngeal colonization. These colonizing strains carry macrolide resistance and virulence genes capable of being transferred to other bacterial species sharing the same niche.

Cellular interactions by LPxTG-anchored pneumococcal adhesins and their streptococcal homologues.

In this review we focus on three important families of LPxTG-anchored adhesins in the human pathogen Streptococcus pneumoniae, but also their homologues in related streptococci. We discuss the contribution of these streptococcal adhesins to host tropism, pathogenesis and their interactions with different host cell types. The first surface structures discussed are the heteropolymeric pili that have been found in important streptococcal pathogens such as S. pneumoniae, S. pyogenes, S. agalactiae and E. faecalis/faecium. Major and minor pilus subunit proteins are covalently joined and finally attached to the cell wall through the action of specific sortases. The role of pili and individual pilin subunits in adhesion and pathogenesis and their structure and assembly in different streptococcal species are being covered. Furthermore, we address recent findings regarding a family of large glycosylated serine-rich repeat (SRR) proteins that act as fibrillar adhesins for which homologues have been found in several streptococcal species including pneumococci. In the pneumococcal genome both pili and its giant SRR protein are encoded by accessory genes present in particular clonal lineages for which epidemiological information is available. Finally, we briefly discuss the role played by the pneumococcal neuraminidase NanA in adhesion and pathogenesis.

A case of diphtheria in Sweden, October 2011.

In October 2011, a child who had arrived in Sweden from Somalia presented with atypical tonsillitis, was treated with penicillin and the symptoms resolved. A throat swab was positive for toxigenic Corynebacterium diphtheriae. The child's family were then vaccinated with diphtheria, tetanus and pertussis vaccine and screened for C. diphtheriae. No secondary cases were found. A high level of adherence to childhood vaccination programmes is an effective way to protect populations against diphtheria.

Pattern of accessory regions and invasive disease potential in Streptococcus pneumoniae.

BACKGROUND: The invasive disease potential (IDP) of Streptococcus pneumoniae differs between serotypes, but the reason for this is unknown. METHODS: A total of 47 pneumococcal isolates from 13 serotypes with different IDPs in humans that belonged to 37 multilocus sequence types were compared by whole genome microarrays and mutant analyses. RESULTS: Approximately 34% of the genes were variable, including 95 genes previously shown by signature-tagged mutagenesis (STM) to be required for invasive disease in mice. Many variable genes were localized to 41 accessory regions (ARs), of which 24 contained genes previously identified by STM as required for invasive disease. Only AR6 and AR34 were preferentially found in isolates of serotypes with high IDPs. Neither AR6, which carries a gene previously identified bySTMas required for invasive disease and encodes a 6-phospho-betaglucosidase, nor the putative adhesin expressed by AR34 was required for mouse virulence in TIGR4. CONCLUSIONS: Pneumococci possess a repertoire of ARs that differ between clones and even between isolates of the same clone. The ARs required for invasive disease in humans may be redundant, as no unique pattern distinguished the most invasive clones from others. The ARs that contained genes previously identified by STM as required for virulence in mice were frequently absent from invasive human isolates. Only 1 AR (AR6) was present in almost all isolates from the serotypes with the highest IDP (1, 4, and 7F), whereas it was missing from many others.

Cloning, expression, purification, crystallization and preliminary X-ray analysis of the pilus-associated sortase C from Streptococcus pneumoniae.

The pilus-associated sortase C from Streptococcus pneumoniae (SrtC or Srt-2) acts as a polymerase for the pilus subunit proteins RrgA and RrgB. Here, the crystallization and preliminary X-ray diffraction analysis of three crystal forms of SrtC are reported. One crystal form belongs to space group P2(1)2(1)2(1), with unit-cell parameters a = 48.9, b = 96.9, c = 98.9 A, alpha = beta = gamma = 90 degrees . The other two crystal forms belong to space group P222, with unit-cell parameters a = 48.8, b = 97.2, c = 99.2 A, alpha = beta = gamma = 90 degrees and a = 48.6, b = 96.5, c = 98.8 A, alpha = beta = gamma = 90 degrees , respectively. Preliminary analysis indicates the presence of two molecules in the asymmetric unit of the crystal for all three forms.

Secreted enteric antimicrobial activity localises to the mucus surface layer.

OBJECTIVES: The intestinal mucosa is constantly exposed to a dense and highly dynamic microbial flora and challenged by a variety of enteropathogenic bacteria. Antibacterial protection is provided in part by Paneth cell-derived antibacterial peptides such as the alpha-defensins. The mechanism of peptide-mediated antibacterial control and its functional importance for gut homeostasis has recently been appreciated in patients with Crohn's ileitis. In the present study, the spatial distribution of antimicrobial peptides was analysed within the small intestinal anatomical compartments such as the intestinal crypts, the overlaying mucus and the luminal content. METHODS: Preparations from the different intestinal locations as well as whole mouse small intestine were extracted and separated by reversed-phase high-performance liquid chromatography. Antibacterial activity was determined in extracts, and the presence of antimicrobial peptides/proteins was confirmed by N-terminal sequencing, mass spectrometry analysis and immunodetection. RESULTS: The secreted antibacterial activity was largely confined to the layer of mucus, whereas only minute amounts of activity were noted in the luminal content. The extractable activity originating from either crypt/mucus/lumen compartments respectively (given as a percentage) was for Listeria monocytogenes, 48 (4)/44 (4)/8 (8); Enterococcus faecalis, 44 (10)/49 (3)/7 (7); Bacterium megaterium, 56 (4)/42 (3)/2 (1); Streptococcus pyogenes, 48 (4)/46 (3)/6 (6); Escherichia coli, 46 (4)/47 (3)/7 (7); and Salmonella enterica sv. Typhimurium, 38 (3)/43 (7)/19 (10). A spectrum of antimicrobial peptides was identified in isolated mucus, which exhibited strong and contact-dependent antibacterial activity against both commensal and pathogenic bacteria. CONCLUSION: These findings show that secreted antimicrobial peptides are retained by the surface-overlaying mucus and thereby provide a combined physical and antibacterial barrier to prevent bacterial attachment and invasion. This distribution facilitates high local peptide concentration on vulnerable mucosal surfaces, while still allowing the presence of an enteric microbiota.

RrgA is a pilus-associated adhesin in Streptococcus pneumoniae.

Adherence to host cells is important in microbial colonization of a mucosal surface, and Streptococcus pneumoniae adherence was significantly enhanced by expression of an extracellular pilus composed of three subunits, RrgA, RrgB and RrgC. We sought to determine which subunit(s) confers adherence. Bacteria deficient in RrgA are significantly less adherent than wild-type organisms, while overexpression of RrgA enhances adherence. Recombinant monomeric RrgA binds to respiratory cells, as does RrgC with less affinity, and pre-incubation of epithelial cells with RrgA reduces adherence of wild-type piliated pneumococci. Non-adherent RrgA-negative, RrgB- and RrgC-positive organisms produce pili, suggesting that pilus-mediated adherence is due to expression of RrgA, rather than the pilus backbone itself. In contrast, RrgA-positive strains with disrupted rrgB and rrgC genes exhibit wild-type adherence despite failure to produce pili by Western blot or immunoelectron microscopy. The density of bacteria colonizing the upper respiratory tract of mice inoculated with piliated RrgA-negative pneumococci was significantly less compared with wild-type; in contrast, non-piliated pneumococci expressing non-polymeric RrgA had similar numbers of bacteria in the nasopharynx as piliated wild-type bacteria. These data suggest that RrgA is central in pilus-mediated adherence and disease, even in the absence of polymeric pilus production.

Clonal success of piliated penicillin nonsusceptible pneumococci.

Antibiotic resistance in pneumococci is due to the spread of strains belonging to a limited number of clones. The Spain(9V)-3 clone of sequence type (ST)156 is one of the most successful clones with reduced susceptibility to penicillin [pneumococci nonsusceptible to penicillin (PNSP)]. In Sweden during 2000-2003, a dramatic increase in the number of PNSP isolates was observed. Molecular characterization of these isolates showed that a single clone of sequence type ST156 increased from 40% to 80% of all serotype 14, thus causing the serotype expansion. Additionally, during the same time period, we examined the clonal composition of two serotypes 9V and 19F: all 9V and 20% of 19F isolates belonged to the clonal cluster of ST156, and overall approximately 50% of all PNSP belonged to the ST156 clonal cluster. Moreover, microarray and PCR analysis showed that all ST156 isolates, irrespective of capsular type, carried the rlrA pilus islet. This islet was also found to be present in the penicillin-sensitive ST162 clone, which is believed to be the drug-susceptible ancestor of ST156. Competitive experiments between related ST156 serotype 19F strains confirmed that those containing the rlrA pilus islet were more successful in an animal model of carriage. We conclude that the pilus island is an important biological factor common to ST156 isolates and other successful PNSP clones. In Sweden, a country where the low antibiotic usage does not explain the spread of resistant strains, at least 70% of all PNSP isolates collected during year 2003 carried the pilus islet.

Role of the innate immune system in host defence against bacterial infections: focus on the Toll-like receptors.

The innate immunity plays a critical role in host protection against pathogens and it relies amongst others on pattern recognition receptors such as the Toll-like receptors (TLRs) and the nucleotide-binding oligomerization domains proteins (NOD-like receptors, NLRs) to alert the immune system of the presence of invading bacteria. Since their recent discovery less than a decade ago, both TLRs and NLRs have been shown to be crucial in host protection against microbial infections but also in homeostasis of the colonizing microflora. They recognize specific microbial ligands and with the use of distinct adaptor molecules, they activate different signalling pathways that in turns trigger subsequent inflammatory and immune responses that allows a immediate response towards bacterial infections and the initiation of the long-lasting adaptive immunity. In this review, we will focus on the role of the TLRs against bacterial infections in humans in contrast to mice that have been used extensively in experimental models of infections and discuss their role in controlling normal flora or nonpathogenic bacteria. We also highlight how bacteria can evade recognition by TLRs.

Addition of a macrolide to a ss-lactam in bacteremic pneumococcal pneumonia.

In the study presented here, data collected prospectively from 340 adult patients hospitalised in five countries with bacteremic pneumococcal CAP and treated with a ss-lactam +/- a macrolide were analysed retrospectively to evaluate the efficacy of this antimicrobial combination. Univariate and multivariate analyses revealed no significant effect on case fatality rate when a macrolide/ss-lactam regimen was used as initial therapy. Results were not affected by severity of illness, or by excluding patients who died within 2 days of admission. Identified predictors of death in a multivariate regression model were age >65 years (OR=2.6), two or more lung lobes affected (OR=2.2), and severity of disease as estimated using the acute physiology score (APS)>8.

A pneumococcal pilus influences virulence and host inflammatory responses.

Streptococcus pneumoniae (pneumococcus) is a major cause of morbidity and mortality world-wide. The initial event in invasive pneumococcal disease is the attachment of encapsulated pneumococci to epithelial cells in the upper respiratory tract. This work provides evidence that initial bacterial adhesion and subsequent ability to cause invasive disease is enhanced by pili, long organelles able to extend beyond the polysaccharide capsule, previously unknown to exist in pneumococci. These adhesive pili-like appendages are encoded by the pneumococcal rlrA islet, present in some, but not all, clinical isolates. Introduction of the rlrA islet into an encapsulated rlrA-negative isolate allowed pilus expression, enhanced adherence to lung epithelial cells, and provided a competitive advantage upon mixed intranasal challenge of mice. Furthermore, a pilus-expressing rlrA islet-positive clinical isolate was more virulent than a nonpiliated deletion mutant, and it out-competed the mutant in murine models of colonization, pneumonia, and bacteremia. Additionally, piliated pneumococci evoked a higher TNF response during systemic infection, compared with nonpiliated derivatives, suggesting that pneumococcal pili not only contribute to adherence and virulence but also stimulate the host inflammatory response.