Invasive Serotype Research Articles

Serotype changes and antimicrobial nonsusceptibility rates of invasive and non-invasive Streptococcus pneumoniae isolates after implementation of 10-valent pneumococcal nontypeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) in Bulgaria

The 10-valent pneumococcal conjugate vaccine (PCV10) has been included in Bulgarian Childhood Immunization Program since 2010. This study aimed to assess serotype distribution and antimicrobial resistance of 198 invasive and non-invasive Streptococcus pneumoniae strains that had been isolated in Bulgaria during 2011–2016 from patients with invasive (IPD) and non-invasive (NIPD) pneumococcal diseases. The most common invasive serotypes were 3 (10.1%), 19F (4.0%), and 7F (3.0%). A significant decrease in the proportion of invasive vaccine types (VTs) from 64.2% to 35.2% was found in comparison with pre-vaccine era. The most common serotypes among middle ear fluids were 3, 19A and 19F (5.6% each), and VTs fell down from 66.4% to 40.0% in post-PCV10 period. Among respiratory isolates, the most prevalent serotypes were some emergent serotypes such as 15A/B/C (5.0%), 19A, and 6C (4.0% each). VTs decreased significantly (16.3%) among vaccinated children compared to unvaccinated children and adults (44.0%). Two non-VTs (19A and 6C) have increased significantly more (p<0.05) in vaccinated children than in unvaccinated patients. The rates of antibiotic nonsusceptible S. pneumoniae in Bulgaria remained high in post-PCV10 era. Among all source of isolates, antimicrobial nonsusceptibility rates were: oral penicillin – 46.5%, trimethoprim-sulfamethoxazole – 45.4%, erythromycin – 43.9%, tetracycline – 37.4%, and multidrug-resistance (MDR) was 44%. The most common MDR serotypes were 19F, 19A, 6A/C, 15A/B/C and 23A. Our results proved that PCV10 vaccination substantially reduced VTs pneumococcal IPD and NIPD. There has been a shift in the distribution of S. pneumoniae serotypes mostly in vaccinated children but also in the whole population and strong serotype-specific antibiotic resistance was observed after vaccine implementation. Therefore, it is important to continue monitoring serotype changes and pneumococcal resistance among all patient ages in addition to aid in determining the long-term effectiveness of PCV10 interventions.

Characteristics of invasive Haemophilus influenzae serotype a (Hia) from Nunavik, Canada and comparison with Hia strains in other North American Arctic regions

Objective: This study examines the microbiological characteristics of invasive Haemophilus influenae serotype a (Hia) isolates from Nunavik (northern Quebec), Canada. The relationship between invasive Hia isolates from Nunavik, Nunavut, Canada, and Alaska, USA will be discussed. MethodsTwenty invasive Hia isolates were recovered from patients in Nunavik from 2010 to 2013 and characterized by biotype, multi-locus sequence typing, IS1016-bexA deletion, antibiotic susceptibility and pulsed field gel electrophoresis (PFGE). ResultsAll 20 Hia isolates were biotype II, sequence type −23, did not have IS1016-bexA deletions and were susceptible to all antibiotics tested. PFGE showed only two patterns, with 19 isolates giving identical molecular fingerprints, and the remaining isolate gave a PFGE pattern >95% similar. ConclusionOne major clone of Hia appears to be causing invasive disease in Nunavik, Canada. Based on previous studies, Hia from Nunavut were also typed as ST-23, while invasive Hia isolates from Alaska belonged to either ST-23 or closely related STs. Thus invasive Hia in the North America Arctic belonged to the ST-23 clonal complex and lacked the IS1016-bexA partial deletion.

The rise and fall of pneumococcal serotypes carried in the PCV era

Streptococcus pneumoniae is a major cause of meningitis, sepsis and pneumonia worldwide. Vaccination using pneumococcal conjugate vaccines (PCV) has therefore been part of the UK’s childhood immunisation programme since 2006. Here we describe pneumococcal carriage rates in children under five years of age attending the paediatric department of a large UK hospital in response to vaccine implementation over seven winter seasons from 2006 to 2013. S. pneumoniae (n=696) were isolated from nasopharyngeal swabs (n=2267) collected during seven consecutive winters, October to March, 2006/7 to 2012/13. This includes the period immediately following the introduction of the seven-valent pneumococcal conjugate vaccine (PCV7) in 2006 in addition to pre- and post-PCV13 introduction in 2010. We show a decrease in PCV13 vaccine serotypes (VT) in the three years following PCV13 vaccine implementation (2010/11 to 2012/13). Serotype 6A represented the only observed VT following PCV13 implementation with all others (including PCV7 serotypes) absent from carriage. Overall pneumococcal carriage, attributable to non-VT (NVT), was consistent across all sampling years with a mean of 31·1%. The ten most frequently isolated NVTs were 6C, 11A, 15B, 23B, 15A, 21, 22F, 35F, 23A and 15C. Fluctuations in the prevalence of each were however noted. Comparing prevalence at 2006/07 with 2012/13 only 15A was shown to have increased significantly (p value of 0·003) during the course of PCV implementation. These data support the increasing evidence that the primary effect of PCVs is due to population immunity by reducing or eliminating the carriage of invasive VT serotypes. With IPD being increasingly attributed to non-vaccine serotypes, surveillance of carriage data continues to act as an early warning system for vaccine design and public health policy that require continual data of both carried pneumococcal serotypes and IPD attributed serotype data.

Organs from a Highly Virulent Zoonotic Outbreak Strain of Streptococcus agalactiae Serotype III, Multilocus Sequence Type 283 Infective Endocarditis Did Not Result in Transmission with Adequate Prophylactic Antibiotic Cover

BackgroundIn 2015, an outbreak of invasive Streptococcus agalactiae serotype III, multilocus sequence type (MLST) 283, related to raw freshwater fish consumption was reported in Singapore. Clinical manifestations of this strain of S. agalactiae were associated with severe clinical course, septicemia and higher incidence of neurological infection. Reports of successful solid organ transplantation from donors with infective endocarditis (IE) are uncommon.MethodsWe present a patient who received kidney transplantation from a donor with S. agalactiae IE.ResultsA 59-year-old man had disseminated S. agalactiae infection causing IE, endopthalmitis, septic arthritis of the right knee, and lumbar spondylodiscitis. Blood cultures, synovial fluid on admission grew S. agalactiae serotype III MLST 283. A transthoracic echocardiogram showed an aortic valve vegetation measuring 0.8 × 0.3 cm. He demised from an intracranial bleed 12 days after admission. Blood cultures prior to harvest, urine cultures and pre-implantation biopsies did not demonstrate infection.Our recipient is a 65-year-old woman with end-stage renal failure. She underwent dual deceased donor kidney transplantation. She received IV basiliximab, IV methylprednisolone followed by PO prednisolone, MMF, and tacrolimus. There was no delayed graft function. She was treated for pneumonia post-operatively and received IV Meropenem and later IV piperacillin–tazobactam for 7 days and subsequently IV ceftriaxone for 2 weeks. She remains well without evidence of S. agalactiae transmission 6 months later. On follow-up, urine cultures are negative with good graft function.ConclusionThis strain of bacteria is associated with invasive infection suggesting increased virulence, the experience from the 2015 outbreak in Singapore echoes this finding. To our knowledge, this is the first reported renal transplantation from a donor with a zoonotic S. agalactiae IE. Whilst IE is not an absolute contraindication to organ transplantation, caution should taken with administration of appropriate antibiotics to donor and recipient. This supports guidelines of a less-restrictive donor screening criteria and potentially increases the donor pool.Disclosures All authors: No reported disclosures.

Nasopharyngeal Pneumococcal Carriage During Childhood Community-Acquired Alveolar Pneumonia: Relationship Between Specific Serotypes and Coinfecting Viruses.

Respiratory viruses and Streptococcus pneumoniae are known to be copathogens in childhood pneumonia. However, it is unclear whether all pneumococcal serotypes are equally prone to such interaction. We attempted to determine association between carried pneumococcal serotypes and respiratory viruses during childhood community-acquired alveolar pneumonia (CAAP). The study was conducted during respiratory syncytial virus (RSV) seasons, before pneumococcal vaccine introduction. Children aged <5 years diagnosed with CAAP with positive pneumococcal nasopharyngeal cultures from whom viral diagnostic tests were obtained were enrolled. Viral detection was done by culture, direct immunofluorescence assay (DFA) or polymerase chain reaction. Adjusted odd ratios (ORs) for serotype-specific carriage rates by presence of specific viruses were calculated: single RSV-positive (RSV[+]); other respiratory viruses (ORspVs[+]); and no respiratory virus (RspVs[-]). We compared invasive and noninvasive pneumococcal serotypes according to previous publications. Invasive serotype colonization was significantly lower in RSV(+) versus RspVs(-) CAAP (OR = 0.18; 95% confidence interval [CI] = .05-.60), whereas colonization with noninvasive serotypes tended to be higher in RSV(+) (OR = 2.39; 95% CI = .98-5.79). We found an inverse relationship between pneumonia-associated invasive pneumococcal serotypes and RSV detection during CAAP. This finding may lead to better understanding of the interaction between respiratory viruses and S. pneumoniae in CAAP pathogenesis.

Emergence of Multidrug-Resistant Pneumococcal Serotype 35B among Children in the United States.

Streptococcus pneumoniae serotype 35B is a nonvaccine serotype associated with high rates of penicillin nonsusceptibility. An increase in the proportion of multidrug-resistant (MDR) 35B isolates has recently been reported. The genetic events contributing to the emergence of MDR serotype 35B are unknown. The sequence type (ST) composition of 78 serotype 35B isolates obtained from pediatric patients with invasive pneumococcal disease from 1994 to 2014 and 48 isolates from pediatric patients with otitis media (noninvasive) from 2011 to 2014 was characterized by multilocus sequence typing (MLST). The most common STs were ST558 (69.2%), ST156 (10.3%), and ST452 (3.8%). Two major clonal complexes (CC), CC558 and CC156, were identified by eBURST analysis. Overall, 91% (71/78) of isolates were penicillin nonsusceptible and 16.7% (13/78) were MDR. Among all invasive serotype 35B isolates, MDR isolates increased significantly, from 2.9% (1/35) to 27.9% (12/43) (P = 0.004), after the 13-valent pneumococcal conjugate vaccine (PCV13) was introduced. All CC156 isolates were identified after the introduction of PCV13 (0/35 [0%] before versus 9/43 [20.9%] after; P = 0.003) and were MDR. All CC156 isolates had similar antimicrobial susceptibility patterns; in contrast, high variability in antimicrobial susceptibility was observed among CC558 isolates. The distributions of CC558 and CC156 among invasive and noninvasive isolates were not different. The increased prevalence of MDR serotype 35B after the introduction of PCV13 was directly associated with the emergence of ST156. Genotyping suggests that capsular switching has occurred between MDR vaccine serotypes belonging to ST156 (e.g., 9V, 14, and 19A) and serotype 35B.

The incidence of invasive pneumococcal serotype 3 disease in the Danish population is not reduced by PCV-13 vaccination.

Since 2010, Denmark has included the 13-valent pneumococcal conjugated vaccine (PCV-13) in the childhood immunization programme. However, serotype 3 remains as an important cause of invasive pneumococcal disease (IPD) in Denmark. IPD surveillance data (1999–2016) was used to calculate the incidence and age-distribution of serotype 3 IPD, and the effect of PCV-13 on serotype 3 IPD incidence was examined. The incidence of serotype 3 IPD in the age group below 65 years was 0.51/100,000 pre PCV-13, and 0.45/100,000 post PCV-13. In the group 0–4 years, serotype 3 IPD incidence was 0.28/100,000 pre PCV-13, and 0.16/100,000 post PCV-13. Serotype 3 IPD incidence in the elderly showed a mean of 4.27/100,000 pre PCV-13, and 4.32/100,000 post PCV-13. PCV-13 childhood immunization in Denmark has not lead to a reduction of the incidence of IPD caused by serotype 3. The reason behind this missing effect needs to be investigated further.

Epidemiological Aspects of Pneumococcal Meningitis in the Russian Federation

Introduction. Pneumococcal meningitis (PM) refers to severe manifestations of pneumococcal disease with high mortality and frequent post-infectious complications. In the context of the introduction of vaccination against pneumococcal infections in the Russian Federation healthcare practice increases the importance of close monitoring of the spread of the PM in the country, identifying areas of concern, the definition of risk and serotype structure of pneumococcus, which is an essential component of the assessment of the effectiveness of vaccination. Materials and methods. We collected 1380 cases identified by the PM on the territory of the Russian Federation in 2010 - 2014. We analyzed the incidence, mortality, mortality, age distribution, social belonging PM patients in the whole country, and in the federal districts. Determined serotype affiliation 35 pneumococcal strains isolated from patients with PM in Russia in 2015. Results. The proportion of pneumococci in the etiological structure of bacterial meningitis during the 2010 - 2014 fluctuated in the range of 18.4 - 24.8% and averaged 22.1%. The incidence of the PM in the Russian Federation in 2010 - 2014 determined at the level of 0.19, the death rate - 0.03. The level of mortality in pneumococcal meningitis in the Russian Federation in 2010 - 2014 increased from 13 (2010) to 21.1% (2014), the average was 17.1%. The most vulnerable age groups were adults over 25 years old and children up to 6 years. Among children under the age of 6 years mortality was 10.7%. The study of serotypes of 35 pneumococcal strains showed that in 2015 serotype structure of invasive pneumococcal vaccine serotypes maintained dominance, the proportion reached 75% for PCV13 and 54% for PCV10. Conclusion. The problem of pneumococcal meningitis remains valid in the Russian Federation. Active use of vaccines, especially in children, will reduce the incidence of this infection and the severity of its consequences.

Influenza A Virus Infection Predisposes Hosts to Secondary Infection with Different Streptococcus pneumoniae Serotypes with Similar Outcome but Serotype-Specific Manifestation.

Influenza A virus (IAV) and Streptococcus pneumoniae are major causes of respiratory tract infections, particularly during coinfection. The synergism between these two pathogens is characterized by a complex network of dysregulated immune responses, some of which last until recovery following IAV infection. Despite the high serotype diversity of S. pneumoniae and the serotype replacement observed since the introduction of conjugate vaccines, little is known about pneumococcal strain dependency in the enhanced susceptibility to severe secondary S. pneumoniae infection following IAV infection. Thus, we studied how preinfection with IAV alters host susceptibility to different S. pneumoniae strains with various degrees of invasiveness using a highly invasive serotype 4 strain, an invasive serotype 7F strain, and a carrier serotype 19F strain. A murine model of pneumococcal coinfection during the acute phase of IAV infection showed a significantly increased degree of pneumonia and mortality for all tested pneumococcal strains at otherwise sublethal doses. The incidence and kinetics of systemic dissemination, however, remained bacterial strain dependent. Furthermore, we observed strain-specific alterations in the pulmonary levels of alveolar macrophages, neutrophils, and inflammatory mediators ultimately affecting immunopathology. During the recovery phase following IAV infection, bacterial growth in the lungs and systemic dissemination were enhanced in a strain-dependent manner. Altogether, this study shows that acute IAV infection predisposes the host to lethal S. pneumoniae infection irrespective of the pneumococcal serotype, while the long-lasting synergism between IAV and S. pneumoniae is bacterial strain dependent. These results hold implications for developing tailored therapeutic treatment regimens for dual infections during future IAV outbreaks.

Customized sequential multiplex PCR for accurate and early determination of invasive pneumococcal serotypes found in India

For accurate and earlier detection of invasive pneumococcal serogroup/serotypes from India, we have rearranged the African sequence of multiplex PCR provided by the Centers for Disease Control and Prevention, USA. This modified approach can successfully be adapted for earlier serotype detection of 95% of the pneumococcal strains prevalent in India.

A Multischool Outbreak Due to Salmonella enterica serovar Napoli Associated with Elevated Rates of Hospitalizations and Bacteremia, Milan, Italy, 2014.

A multischool outbreak of salmonellosis caused by Salmonella enterica serovar Napoli was investigated in the province of Milan from October to November 2014, following an increase in school absenteeism coinciding with two positive cases. Epidemiological studies detected 47 cases in four primary schools: 46 children and 1 adult woman (51.4% males and 48.6% females, median age 8.9). From these, 14 cases (29.8%) were severe and resulted in hospitalization, including 6 children (12.8%) who developed an invasive salmonellosis. The epidemic curve revealed an abnormally long incubation period, peaking 1 week after the first confirmed case. Twenty-five available isolates were typed by pulsed-field gel electrophoresis showing an identical pattern. The isolate belongs to ST474, an ST composed exclusively of Salmonella Napoli human strains isolated in France and Italy. Antibiotic resistance analysis showed resistance to aminoglycosides, correlating with the presence of the aminoglycoside resistance gene aadA25 in its genome. Trace-back investigations strongly suggested contaminated ham as the most likely food vehicle, which was delivered by a common food center on 21 October. Nevertheless, this ingredient could not be retrospectively investigated since it was no longer available at the repository. This represents the largest Salmonella Napoli outbreak ever reported in Italy and provides a unique scenario for studying the outcome of salmonellosis caused by this emerging and potentially invasive nontyphoidal serotype.

Phylogenetic Analysis of Invasive Serotype 1 Pneumococcus in South Africa, 1989 to 2013.

Serotype 1 is an important cause of invasive pneumococcal disease in South Africa and has declined following the introduction of the 13-valent pneumococcal conjugate vaccine in 2011. We genetically characterized 912 invasive serotype 1 isolates from 1989 to 2013. Simpson's diversity index (D) and recombination ratios were calculated. Factors associated with sequence types (STs) were assessed. Clonal complex 217 represented 96% (872/912) of the sampled isolates. Following the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13), ST diversity increased in children <5 years (D, 0.39 to 0.63, P = 0.002) and individuals >14 years (D, 0.35 to 0.54, P < 0.001): ST-217 declined proportionately in children <5 years (153/203 [75%] versus 21/37 [57%], P = 0.027) and individuals >14 years (242/305 [79%] versus 96/148 [65%], P = 0.001), whereas ST-9067 increased (4/684 [0.6%] versus 24/228 [11%], P < 0.001). Three subclades were identified within ST-217: ST-217C1 (353/382 [92%]), ST-217C2 (15/382 [4%]), and ST-217C3 (14/382 [4%]). ST-217C2, ST-217C3, and single-locus variant (SLV) ST-8314 (20/912 [2%]) were associated with nonsusceptibility to chloramphenicol, tetracycline, and co-trimoxazole. ST-8314 (20/912 [2%]) was also associated with increased nonsusceptibility to penicillin (P < 0.001). ST-217C3 and newly reported ST-9067 had higher recombination ratios than those of ST-217C1 (4.344 versus 0.091, P < 0.001; and 0.086 versus 0.013, P < 0.001, respectively). Increases in genetic diversity were noted post-PCV13, and lineages associated with antimicrobial nonsusceptibility were identified.

Active hospital-based surveillance of invasive pneumococcal disease and clinical pneumonia in infants and young children in two Polish counties.

IntroductionInvasive pneumococcal disease (IPD) incidence, serotype distribution, and antibiotic susceptibility of Streptococcus pneumoniae were estimated in children aged 28 days to < 60 months.Material and methodsOne-year prospective, hospital-based surveillance was conducted starting on February 15, 2008, at two children's hospitals serving the city and surrounding county of Poznań and Poznański, Poland. Eligible children had fever ≥ 39.0°C or physician-suspected IPD. Blood cultures were obtained from all children, cerebrospinal fluid in suspected meningitis cases, and chest radiographs (CXRs) in suspected pneumonia cases.ResultsSeven of 1,581 eligible children had confirmed IPD. Estimated IPD incidence per 100,000 children was 11.89 (95% CI: 4.78–24.50) overall and 20.1 (95% CI: 6.52–46.84) in subjects aged 28 days to < 24 months. One S. pneumoniae isolate of each of the following serotypes was obtained: 6B, 14, 23A, 23F, and 33F. Two isolates were resistant to both trimethoprim-sulfamethoxazole and erythromycin. Clinical pneumonia incidence among children aged 28 days to < 24 months and 24 months to < 60 months was 3,151.3 (95% CI: 2934.7–3379.7) and 962.7 (95% CI: 861.2–10,072.9) per 100,000 children, respectively. CXR-confirmed pneumonia rates in the same groups were 1,035.7 (95% CI: 913.2–1,170.1) and 379.8 (95% CI: 317.1–451.3) per 100,000 children, respectively.ConclusionsIPD is an important cause of morbidity in Poznań and Poznański county, Poland. Among participants aged < 5 years with fever or suspected IPD, pneumonia was the most common diagnosis and was highest in children aged < 24 months.

Nasopharyngeal carriage of Streptococcus pneumoniae among children in an urban setting in Brazil prior to PCV10 introduction

Information on pneumococcal carriage in the pre-vaccine period is essential to predict and assess the impact of PCV in settings where disease surveillance is particularly difficult. Therefore, we present data on pneumococcal carriage before the introduction of the 10-valent-pneumococcal conjugate vaccine (PCV10) in Brazil. We conducted a prospective study on a cohort of 203 children aged <5 years old, randomly selected in an urban community located in the periphery of the city of Salvador, Brazil and followed them from January/2008 to January/2009. Nasopharyngeal swabs were collected from each child at four times. In total, 721 swabs were collected, yielding a pneumococcal carriage prevalence of 55% (n=398). In multivariate analyses, the variables associated with carriage were having contact with three or more children <2 years old (OR, 2.00; 95% CI 1.33–2.89) and living in a house with an average of 3 residents per room (OR, 1.77; 95% CI 1.05–3.10). Also, white participants were more likely to be protected from colonization (OR, 0.52; 95% CI 0.29–0.93), and prevalence of carriage varied over time, with lower prevalence occurring from February to June (OR, 0.53; 95% CI 0.37–0.78) compared to July to January. Contact with children under 2 years of age and living in crowded housing also were associated with colonization by highly invasive serotypes, although this relationship was not significant. The most prevalent vaccine serotypes were 6A/B (25.4%), 19F (10.1%) and 14 (9.0%), while the most prevalent non-vaccine serotypes were 16F (4.8%), 15B/C (4.5%) and 6C/D (3.5%). Overall, 38.4% (153/398) of the isolates were non-susceptible to penicillin, and of those, 73.8% (113/153) were non-susceptible to trimethoprim/sulfamethoxazole. Colonization rate by PCV10 serotypes was 52.2%. Routine PCV10 vaccination can lead to significant changes in pneumococcal serotypes found in NP colonization, indicating a need for continued monitoring, especially in crowded settings, as occurs in Brazil's slums.

Invasive Haemophilus influenzae Serotype A Infection in Children, Clinical Description of an Emerging Pathogen—Alaska, 2002–2014

Invasive Haemophilus influenzae Serotype A Infection in Children, Clinical Description of an Emerging Pathogen—Alaska, 2002–2014

Development and characterization of a novel model of invasive pneumococcal pneumonia in invasively ventilated PIGS

Streptococcus pneumoniae is the most common causative pathogen of community-acquired pneumonia (CAP). Often, patients with pneumococcal CAP are admitted into intensive care units, particularly when affected by invasive serotypes.

Vaccinations in respiratory medicine

Vaccinations are the most successful and cost-effective measures for prevention of infections. Important pathogens of respiratory tract infections (e.g. influenza viruses and pneumococci) can be effectively treated by vaccinations. The seasonal trivalent and recently now quadrivalent influenza vaccines include antigens from influenza A and B type viruses, which have to be modified annually oriented to the circulating strains. The effective protection by influenza vaccination varies considerably (too short protection time, mismatch); therefore, administration late in the year is the best approach (November/December). Two pneumococcal vaccines are recommended for adults: the over 30-year-old 23-valent polysaccharide vaccine (PPV23) and the 4-year-old 13-valent conjugate vaccine (PCV13). The immunological and clinical efficacy of PPV23 is controversially discussed; however, a moderate reduction of invasive pneumococcal infections is widely accepted. The PCV13 stimulates a T-cell response and has currently demonstrated its clinical efficacy in an impressive study (CAPiTA). The problem of PCV13 is the relatively limited coverage of only 47% of the currently circulating invasive pneumococcal serotypes.

A Structural Snapshot of Type II Pilus Formation in Streptococcus pneumoniae

Pili are fibrous appendages expressed on the surface of a vast number of bacterial species, and their role in surface adhesion is important for processes such as infection, colonization, andbiofilm formation. The human pathogen Streptococcus pneumoniae expresses two different types of pili, PI-1 and PI-2, both of which require the concerted action of structural proteins and sortases for their polymerization. The type PI-1 streptococcal pilus is a complex, well studied structure, but the PI-2 type, present in a number of invasive pneumococcal serotypes, has to date remained less well understood. The PI-2 pilus consists of repeated units of a single protein, PitB, whose covalent association is catalyzed by cognate sortase SrtG-1 and partner protein SipA. Here we report the high resolution crystal structures of PitB and SrtG1 and use molecular modeling to visualize a "trapped" 1:1 complex between the two molecules. X-ray crystallography and electron microscopy reveal that the pneumococcal PI-2 backbone fiber is formed by PitB monomers associated in head-to-tail fashion and that short, flexible fibers can be formed even in the absence of coadjuvant proteins. These observations, obtained with a simple pilus biosynthetic system, are likely to be applicable to other fiber formation processes in a variety of Gram-positive organisms.

Emergence of Serotype IV Group B Streptococcus Adult Invasive Disease in Manitoba and Saskatchewan, Canada, Is Driven by Clonal Sequence Type 459 Strains.

Serotype IV group B Streptococcus (GBS) is emerging in Canada and the United States with rates as high as 5% of the total burden of adult invasive GBS disease. To understand this emergence, we studied the population structure and assessed the antimicrobial susceptibility of serotype IV isolates causing adult invasive infection in Manitoba and Saskatchewan, Canada, between 2010 and 2014. Whole-genome sequencing was used to determine multilocus sequence typing information and identify genes encoding antimicrobial resistance in 85 invasive serotype IV GBS strains. Antimicrobial susceptibility testing was performed by standard methods. Strain divergence was assessed using genome-wide single-nucleotide polymorphism analysis. Serotype IV strains were responsible for 16.9% of adult invasive GBS infections in Manitoba and Saskatchewan during the period. The majority of serotype IV isolates (89%) were clonally related, tetracycline-, erythromycin-, and clindamycin-resistant sequence type 459 (ST459) strains that possessed genes tetM and ermTR. Genome comparisons between ST459 and serotype V ST1 GBS identified several areas of recombination in an overall similar genomic background. Serotype IV ST459 GBS strains are expanding and causing a substantial percentage of adult invasive GBS disease. This emergence may be linked to the acquisition of resistance to tetracycline, macrolides, and lincosamides.

Salmonella: A review on pathogenesis, epidemiology and antibiotic resistance

Salmonella is one of the most frequently isolated foodborne pathogens. It is a major worldwide public health concern, accounting for 93.8 million foodborne illnesses and 155,000 deaths per year. To date, over 2500 Salmonella serotypes have been identified and more than half of them belong to Salmonella enterica subsp. enterica, which accounts for the majority of Salmonella infections in humans. Salmonella infections that involve invasive serotypes are often life threatening, necessitating appropriate and effective antibiotic therapy. The emergence of multi-drug-resistant (MDR) Salmonella serotypes is having a great impact on the efficacy of antibiotic treatment, and an increasing prevalence of MDR strains may lead to an increase in mortality rates of Salmonella infections. Epidemiological studies indicate that MDR Salmonella serotypes are more virulent than susceptible strains, as reflected by increased severity and more prolonged disease in patients infected by MDR strains. Preventive measures have been proposed to eliminate the spread of Salmonella infection. While the maintenance of effective food hygiene and water sanitation remain the cornerstones, additional measures such as restriction of indiscriminate use of antibiotics in food animals are important. This review provides an overview of Salmonella infection, and discusses the nomenclature, pathogenesis, clinical manifestations, epidemiology and antibiotic resistance of Salmonella.