Multilocus Sequence Typing Data Research Articles

Standardization of multilocus sequence typing scheme for Mycobacterium abscessus and Mycobacterium massiliense

This study aims to develop a multilocus sequence typing (MLST) scheme for Mycobacterium abscessus complex for the typing of stains within each species. A total of 89 clinical isolates of M. abscessus complex from 71 patients of 2 tertiary care hospitals in South Korea were included. Forty-two isolates were identified as M. abscessus, and 29, as Mycobacterium massiliense through sequencing of 8 housekeeping genes and rpoB. The MLST scheme identified 26 different sequence types(STs) and 13 different clonal complexes (CCs) in M. abscessus and 12 different STs and 6 different CCs in M. massiliense. The MLST data showed high concordance with the XbaI-macrorestriction patterns of pulsed-field gel electrophoresis in the duplicated isolates. Our MLST schemes could identify different strains of M. abscessus and M. massiliense, and the schemes also showed a reliable reproducibility. Therefore, our MLST schemes may be useful in studying the epidemiology of M. abscessus and M. massiliense infections.

P3.257 Distinct But Also Highly Similar Chlamydia Trachomatis Strains in Nanjing, China and in Amsterdam, the Netherlands

In China, Chlamydia trachomatis infections are endemic in the general population, but most infections are found in specific risk groups, such as female sex workers. The most prevalent C. trachomatis...

Strains of Pseudomonas syringae pv. syringae from pea are phylogenetically and pathogenically diverse.

Pseudomonas syringae pv. syringae causes extensive yield losses in the pea crop worldwide, although there is little information on its host specialization and its interactions with pea. A collection of 88 putative P. syringae pv. syringae strains (including 39 strains isolated from pea) was characterized by repetitive polymerase chain reaction (rep-PCR), multilocus sequence typing (MLST), and syrB amplification and evaluated for pathogenicity and virulence. rep-PCR data grouped the strains from pea into two groups (1B and 1C) together with strains from other hosts; a third group (1A) was formed exclusively with strains isolated from non-legume species. MLST data included all strains from pea in the genomospecies 1 of P. syringae pathovars defined in previous studies; they were distributed in the same three groups defined by rep-PCR. The inoculations performed in two pea cultivars showed that P. syringae pv. syringae strains from groups 1A and 1C were less virulent than strains from group 1B, suggesting a possible pathogenic specialization in this group. This study shows the existence of genetically and pathogenically distinct P. syringae pv. syringae strain groups from pea, which will be useful for the diagnostic and epidemiology of this pathogen and for disease resistance breeding.

Elucidating the aetiology of human Campylobacter coli infections.

There has been little research on the determinants of Campylobacter coli infection, despite its contributing up to 10% of human Campylobacter infections. A case-control and two case-case study methods explored the aetiology of C. coli over a one year period across Scotland. The case-control multivariate model found an increased risk of C. coli infection in people older than 19 years (O.R. = 3.352), and during the summer months (O.R. = 2.596), while residing in an urban area decreased the risk (O.R. = 0.546). The first case-case study compared C. coli and C. jejuni cases and also showed a higher risk of C. coli during the summer (O.R. = 1.313) and in people older than 19 years (O.R. = 0.791). Living in an urban area was associated with a reduced risk of infection (O.R. = 0.769). Multi-locus sequence typing (MLST) indicated that sheep and chicken C. coli sequence types (STs) were most frequently found in humans whilst those from cattle and pigs were rarer. MLST diversity was high in isolates from pigs and chicken, intermediate in human isolates, and low in ruminant isolates. The second case-case study used MLST data to ascribe putative sources of infection to the cases. The putative source for 40% of cases was chicken, with 60% acquired from other sources (ruminants 54% and pigs 6%). The case-case analysis also showed that female gender was a risk factor (O.R. = 1.940), which may be explained by females being more likely to prepare poultry in the home. These findings indicate differences between the aetiology of C. coli and C. jejuni infections: this should be taken into account by public health professionals when developing strategies to reduce the burden of human campylobacteriosis.

Multilocus sequence analysis of Borrelia burgdorferi s.l. in Russia

Borrelia burgdorferi sensu lato is a species complex that includes the causative agents of Lyme borreliosis (LB). Classification of the complex was greatly influenced by the method of multilocus sequence typing (MLST), proposed in 2008 and analyzing the spatial distribution of sequence types (STs). Despite the fact that Russia is the largest natural focus of LB to date, it is represented by only 3 strains of the 1323 strains deposited in the MLST database. In this paper, we identified STs for 24 B. burgdorferi s.l. strains isolated from ticks from almost all regions of Russia, 16 of which have not been described so far. It has been shown that the Russian isolates of B. afzelii are of Asian origin and are characterized by a lack of territorial mixing of STs. In contrast, B. garinii and B. bavariensis showed ST mixing between different localities. Comparison of MLST data with the results of sequence analysis of rrf–rrl intergenic spacer led to the conclusion that the previously described genomic groups of B. garinii correspond to the genospecies according to the new classification: 20047 corresponds to B. garinii, and NT29 corresponds to B. bavariensis. The genomic group, ChY13p, characterized by an unusual PCR-RFLP profile, belongs to the species B. garinii (prototype strain 20047). Thus, the use of a reliable method to study the phylogeny and evolution of Borrelia based on MLST, helps to clarify the existing classification. The standardized research procedure and database created could become the basis for a global scientific cooperation in LB research.

Genotypic Diversity and Virulence Characteristics of Clinical and Environmental Vibrio vulnificus Isolates from the Baltic Sea Region

The genetic diversity of Vibrio vulnificus isolates from clinical and environmental sources originating from the Baltic Sea region was evaluated by multilocus sequence typing (MLST), and possible relationships between MLST clusters, potential genotypic and phenotypic traits associated with pathogenicity, and source of isolation were investigated. The studied traits included genotyping of polymorphic loci (16S rRNA, vcg, and pilF), presence/absence of potential virulence genes, including nanA, nab, and genes of pathogenicity regions, metabolic features, hemolytic activity, resistance to human serum, and cytotoxicity to human intestinal cells. MLST generated 35 (27 new) sequence types and divided the 53 isolates (including four reference strains) into two main clusters, with cluster I containing biotype 1 and 2 isolates of mainly environmental origin and cluster II containing biotype 1 isolates of mainly clinical origin. Cluster II isolates were further subdivided into two branches. Branch IIB included isolates from recent cases of wound infections that were acquired at the German Baltic Sea coastline between 2010 and 2011 and isolates from seawater samples of the same regions isolated between 1994 and 2010. Comparing the MLST data with the results of genotyping and phenotyping showed that strains of MLST cluster II possess a number of additional pathogenicity-associated traits compared to cluster I strains. Rapid microbiological methods such as matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry combined with typing of selected virulence-associated traits (e.g., serum resistance, mannitol fermentation, nanA, and pathogenicity region XII) could be used for risk assessment purposes regarding V. vulnificus strains isolated from the Baltic Sea region.

Characterization of water and wildlife strains as a subgroup ofCampylobacter jejuniusing DNA microarrays

Campylobacter jejuni is the leading cause of human bacterial gastroenteritis worldwide, but source attribution of the organism is difficult. Previously, DNA microarrays were used to investigate isolate source, which suggested a non-livestock source of infection. In this study we analysed the genome content of 162 clinical, livestock and water and wildlife (WW) associated isolates combined with the previous study. Isolates were grouped by genotypes into nine clusters (C1 to C9). Multilocus sequence typing (MLST) data demonstrated that livestock associated clonal complexes dominated clusters C1-C6. The majority of WW isolates were present in the C9 cluster. Analysis of previously reported genomic variable regions demonstrated that these regions were linked to specific clusters. Two novel variable regions were identified. A six gene multiplex PCR (mPCR) assay, designed to effectively differentiated strains into clusters, was validated with 30 isolates. A further five WW isolates were tested by mPCR and were assigned to the C7-C9 group of clusters. The predictive mPCR test could be used to indicate if a clinical case has come from domesticated or WW sources. Our findings provide further evidence that WW C. jejuni subtypes show niche adaptation and may be important in causing human infection.

Molecular epidemiology and resistance profiles of Clostridium difficile in a tertiary care hospital in Spain

Epidemiological surveillance of Clostridium difficile infection has gained importance in recent years as a result of the rapid spread of epidemic strains, including hypervirulent strains and strains with reduced susceptibility to antimicrobials. The molecular epidemiology and antimicrobial susceptibility of C. difficile in the reference hospital of the Balearic Islands (Spain) is reported in this study. One hundred isolates of toxigenic C. difficile from different patients were selected using rapid dual EIA screening test. All isolates were characterized through toxin profile, PCR ribotyping and, in addition, multi-locus sequence typing (MLST) was performed on fifty selected strains. MICs to metronidazole, vancomycin, erythromycin and moxifloxacin were also determined. A total of 43 different ribotypes were distinguished, with higher prevalence of ribotype 014 (34%). Twenty one per cent of the isolates expressed binary toxin and it is noteworthy that 62% of these were identified as the hypervirulent ribotype 078, the second most prevalent ribotype found in our hospital (13%). A total of 20 different sequence types (STs) were found, including a new described allele and ST. MLST data showed a clear concordance between some ribotypes and STs, mainly represented by ribotype 014/ST-2, ribotype 078/ST-11 and ribotype 001/ST-3. Phylogenetic analysis also revealed that most of the isolates were genetically related, forming a large clonal complex. Finally, ribotypes 078 (ST-11) and 001 (ST-3) were associated with higher resistance to erythromycin and to erythromycin and moxifloxacin, respectively. All these data suggest that the combination of ribotyping and MLST is a good tool for the surveillance of the changing epidemiology of C. difficile. A wide dissemination of clones has been observed in our setting, ribotype 014 (ST-2) being the most prevalent followed by the hypervirulent ribotype 078 (ST-11) and ribotype 001 (ST-3), their spread in our setting probably influenced by their higher resistance.

The Evolutionary Path to Extraintestinal Pathogenic, Drug-Resistant Escherichia coli Is Marked by Drastic Reduction in Detectable Recombination within the Core Genome

Escherichia coli is a highly diverse group of pathogens ranging from commensal of the intestinal tract, through to intestinal pathogen, and extraintestinal pathogen. Here, we present data on the population diversity of E. coli, using Bayesian analysis to identify 13 distinct clusters within the population from multilocus sequence typing data, which map onto a whole-genome-derived phylogeny based on 62 genome sequences. Bayesian analysis of recombination within the core genome identified reduction in detectable core genome recombination as one moves from the commensals, through the intestinal pathogens down to the multidrug-resistant extraintestinal pathogenic clone E. coli ST131. Our data show that the emergence of a multidrug-resistant, extraintestinal pathogenic lineage of E. coli is marked by substantial reduction in detectable core genome recombination, resulting in a lineage which is phylogenetically distinct and sexually isolated in terms of core genome recombination.

Endophytic establishment of the soil isolate Burkholderia sp. CC-Al74 enhances growth and P-utilization rate in maize (Zea mays L.)

Bacteria are common inhabitants of the rhizosphere or as endophytes in internal plant tissues. Among many bacterial genera, Burkholderia is a genus rich in nitrogen-fixing and phosphate-solubilizing strains that have been isolated from various plant systems. The function of phosphate-solubilizing bacteria in agriculture has been well documented, including enhancements in growth, yield and disease-resistance of crops. However, their response when introduced into a plant system in vitro is poorly studied. Inoculation of Burkholderia sp. CC-Al74, a phosphate-solubilizing soil isolate, on maize seeds resulted in the persistent endophytic establishment as determined by PCR detection method using Burkholderia-specific 16S rRNA gene primers. Burkholderia sp. CC-Al74-inoculated maize showed significant increases in plant height, plant biomass and root length, of about 45%, 48% and 86%, respectively, as compared to non-inoculated controls. After endophytic establishment, inoculated maize seedlings showed 2.4-fold increase in P-utilization rate in planta as well as an increased rhizosphere phosphatase activity as compared to the non-inoculated control. Nutrient analysis of inoculated maize showed 150% and 90% higher contents of P and N as compared to the non-inoculated control, respectively. Multilocus sequence typing (MLST) analysis showed that Burkholderia sp. CC-Al74 had a unique Sequence-Type, ST-730, which was novel when compared with existing STs in the MLST database. The phylogeny produced by recA sequence and MLST data revealed that Burkholderia sp. CC-Al74 is a novel member of Burkholderia cepacia complex. In summary, we provide direct evidence, which shows that the soil isolate Burkholderia sp. CC-Al74 could improve P-utilization rate as well as total P and N contents post-endophytic colonization in maize in vitro.

High-throughput single-nucleotide polymorphism-based typing of shared Pseudomonas aeruginosa strains in cystic fibrosis patients using the Sequenom iPLEX platform

Shared strains of Pseudomonas aeruginosa are now well recognized in people with cystic fibrosis (CF), and suitable P. aeruginosa laboratory typing tools are pivotal to understanding their clinical significance and guiding infection control policies in CF clinics. We therefore compared a single-nucleotide polymorphism (SNP)-based typing method using Sequenom iPLEX matrix-assisted laser desorption ionization with time-of-flight mass spectrometry (MALDI-TOF MS) with typing methods used routinely by our laboratory. We analysed 617 P. aeruginosa isolates that included 561 isolates from CF patients collected between 2001 and 2009 in two Brisbane CF clinics and typed previously by enterobacterial repetitive intergenic consensus (ERIC)-PCR, as well as 56 isolates from non-CF patients analysed previously by multilocus sequence typing (MLST). The isolates were tested using a P. aeruginosa Sequenom iPLEX MALDI-TOF (PA iPLEX) method comprising two multiplex reactions, a 13-plex and an 8-plex, to characterize 20 SNPs from the P. aeruginosa housekeeping genes acsA, aroE, guaA, mutL, nuoD, ppsA and trpE. These 20 SNPs were employed previously in a real-time format involving 20 separate assays in our laboratory. The SNP analysis revealed 121 different SNP profiles for the 561 CF isolates. Overall, there was at least 96% agreement between the ERIC-PCR and SNP analyses for all predominant shared strains among patients attending our CF clinics: AUST-01, AUST-02 and AUST-06. For the less frequently encountered shared strain AUST-07, 6/25 (24%) ERIC-PCR profiles were misidentified initially as AUST-02 or as unique, illustrating the difficulty of gel-based analyses. SNP results for the 56 non-CF isolates were consistent with previous MLST data. Thus, the PA iPLEX format provides an attractive high-throughput alternative to ERIC-PCR for large-scale investigations of shared P. aeruginosa strains.

Predicted strain coverage of a meningococcal multicomponent vaccine (4CMenB) in Europe: a qualitative and quantitative assessment

A novel multicomponent vaccine against meningococcal capsular group B (MenB) disease contains four major components: factor-H-binding protein, neisserial heparin binding antigen, neisserial adhesin A, and outer-membrane vesicles derived from the strain NZ98/254. Because the public health effect of the vaccine, 4CMenB (Novartis Vaccines and Diagnostics, Siena, Italy), is unclear, we assessed the predicted strain coverage in Europe. We assessed invasive MenB strains isolated mainly in the most recent full epidemiological year in England and Wales, France, Germany, Italy, and Norway. Meningococcal antigen typing system (MATS) results were linked to multilocus sequence typing and antigen sequence data. To investigate whether generalisation of coverage applied to the rest of Europe, we also assessed isolates from the Czech Republic and Spain. 1052 strains collected from July, 2007, to June, 2008, were assessed from England and Wales, France, Germany, Italy, and Norway. All MenB strains contained at least one gene encoding a major antigen in the vaccine. MATS predicted that 78% of all MenB strains would be killed by postvaccination sera (95% CI 63-90, range of point estimates 73-87% in individual country panels). Half of all strains and 64% of covered strains could be targeted by bactericidal antibodies against more than one vaccine antigen. Results for the 108 isolates from the Czech Republic and 300 from Spain were consistent with those for the other countries. MATS analysis showed that a multicomponent vaccine could protect against a substantial proportion of invasive MenB strains isolated in Europe. Monitoring of antigen expression, however, will be needed in the future. Novartis Vaccines and Diagnostics.

Practicalities of Using Non-Local or Non-Recent Multilocus Sequence Typing Data for Source Attribution in Space and Time of Human Campylobacteriosis

In this study, 1208 Campylobacter jejuni and C. coli isolates from humans and 400 isolates from chicken, collected in two separate periods over 12 years in The Netherlands, were typed using multilocus sequence typing (MLST). Statistical evidence was found for a shift of ST frequencies in human isolates over time. The human MLST data were also compared to published data from other countries to determine geographical variation. Because only MLST typed data from chicken, taken from the same time point and spatial location, were available in addition to the human data, MLST datasets for other Campylobacter reservoirs from selected countries were used. The selection was based on the degree of similarity of the human isolates between countries. The main aim of this study was to better understand the consequences of using non-local or non-recent MLST data for attributing domestically acquired human Campylobacter infections to specific sources of origin when applying the asymmetric island model for source attribution. In addition, a power-analysis was done to find the minimum number of source isolates needed to perform source attribution using an asymmetric island model. This study showed that using source data from other countries can have a significant biasing effect on the attribution results so it is important to carefully select data if the available local data lack in quality and/or quantity. Methods aimed at reducing this bias were proposed.

First environmental isolation of Cryptococcus gattii, genotype AFLP5, from India and a global review

We report the first environmental isolation from India of Cryptococcus gattii, genotype amplified fragment length polymorphism 5 (AFLP5), which is one of the rarely reported genotypes of this pathogen. It originated from decayed wood inside a trunk hollow of Manilkara hexandra, a native tree in Delhi. We investigated 101 isolates of C. gattii, originating from 556 samples of decayed wood inside trunk hollows of 311 heterogeneous tree species and their surrounding soil. Of these, only a solitary isolate proved to be AFLP5, the remainder belonged to AFLP4. Antifungal susceptibility testing showed a low MIC90 (0.25 μg ml(-1) ) of the new azoles posaconazole and isavuconazole for these environmental isolates. Genotype AFLP5 has been mainly reported from environmental sources in Colombia and from clinical sources in California (USA), where it seems to be endemic. Phylogenetic analysis of multi-locus sequence typing data showed that the Indian AFLP5 C. gattii isolate had a distinct profile compared with a cluster of mainly Colombian and Californian C. gattii AFLP5 isolates. As molecular typing of human pathogenic fungi is still in its infancy and not accessible to many countries, our current knowledge cannot be taken as reflective of the true geographic distribution of C. gattii AFLP5 or its other rarely reported molecular types.

A FRET-Based Real-Time PCR Assay to Identify the Main Causal Agents of New World Tegumentary Leishmaniasis

In South America, various species of Leishmania are endemic and cause New World tegumentary leishmaniasis (NWTL). The correct identification of these species is critical for adequate clinical management and surveillance activities. We developed a real-time polymerase chain reaction (PCR) assay and evaluated its diagnostic performance using 64 archived parasite isolates and 192 prospectively identified samples collected from individuals with suspected leishmaniasis enrolled at two reference clinics in Lima, Peru. The real-time PCR assay was able to detect a single parasite and provided unambiguous melting peaks for five Leishmania species of the Viannia subgenus that are highly prevalent in South America: L. (V.) braziliensis, L. (V.) panamensis, L. (V.) guyanensis, L. (V.) peruviana and L. (V.) lainsoni. Using kinetoplastid DNA-based PCR as a gold standard, the real-time PCR had sensitivity and specificity values of 92% and 77%, respectively, which were significantly higher than those of conventional tests such as microscopy, culture and the leishmanin skin test (LST). In addition, the real-time PCR identified 147 different clinical samples at the species level, providing an overall agreement of 100% when compared to multilocus sequence typing (MLST) data performed on a subset of these samples. Furthermore, the real-time PCR was three times faster and five times less expensive when compared to PCR - MLST for species identification from clinical specimens. In summary, this new assay represents a cost-effective and reliable alternative for the identification of the main species causing NWTL in South America.

Source tracking of human leptospirosis: serotyping and genotyping of Leptospira isolated from rodents in the epidemic area of Guizhou province, China

BackgroundSustained human leptospirosis as well as death cases has been reported in Qiandongnan Prefecture, Southeast of Guizhou, China, recently, but these human patients were only clinically diagnosed, and leptospires have never been isolated from patients in these epidemic regions, In order to track the source of infection and understand the etiologic characteristic of leptospirosis, we performed rodent carrier surveillance for leptospirosis in the epidemic area in 2011. The population distribution of rodents in the epidemic regions was revealed.ResultsFour strains of leptospire were isolated from Apodemus agrarius. Microscopic agglutination test (MAT) confirmed the four isolates belonged to leptospiral serogroup Icterohaemorrhagiae. Multilocus sequence typing (MLST) indicated that all the four strains were defined as sequence type 1(ST1), which is identical to the three strains isolated from Rattus tanezumi in Rongjiang County in 2007. Clustering analysis of the MLST data indicated that the local isolates exactly matched with reference strain of leptospiral serovar Lai strain 56601, which is consistent with anti-Leptospira antibody detection of patients using MAT.ConclusionsApodemus agrarius may be the potentially important carrier of leptospirosis and the potential source of leptospiral infection in human, and serovar Lai maybe the epidemic serovar of Leptospira in the localities.

International Life Science Institute North America Cronobacter (Formerly Enterobacter sakazakii) isolate set.

Foodborne pathogen isolate collections are important for the development of detection methods, for validation of intervention strategies, and to develop an understanding of pathogenesis and virulence. We have assembled a publicly available Cronobacter (formerly Enterobacter sakazakii) isolate set that consists of (i) 25 Cronobacter sakazakii isolates, (ii) two Cronobacter malonaticus isolates, (iii) one Cronobacter muytjensii isolate, which displays some atypical phenotypic characteristics, biochemical profiles, and colony color on selected differential media, and (iv) two nonclinical Enterobacter asburiae isolates, which show some phenotypic characteristics similar to those of Cronobacter spp. The set consists of human (n = 10), food (n = 11), and environmental (n = 9) isolates. Analysis of partial 16S rDNA sequence and seven-gene multilocus sequence typing data allowed for reliable identification of these isolates to species and identification of 14 isolates as sequence type 4, which had previously been shown to be the most common C. sakazakii sequence type associated with neonatal meningitis. Phenotypic characterization was carried out with API 20E and API 32E test strips and streaking on two selective chromogenic agars; isolates were also assessed for sorbitol fermentation and growth at 45°C. Although these strategies typically produced the same classification as sequence-based strategies, based on a panel of four biochemical tests, one C. sakazakii isolate yielded inconclusive data and one was classified as C. malonaticus. EcoRI automated ribotyping and pulsed-field gel electrophoresis (PFGE) with XbaI separated the set into 23 unique ribotypes and 30 unique PFGE types, respectively, indicating subtype diversity within the set. Subtype and source data for the collection are publicly available in the PathogenTracker database (www. pathogentracker. net), which allows for continuous updating of information on the set, including links to publications that include information on isolates from this collection.

Pneumococcal Capsular Switching: A Historical Perspective

Background.Changes in serotype prevalence among pneumococcal populations result from both serotype replacement and serotype (capsular) switching. Temporal changes in serotype distributions are well documented, but the contribution of capsular switching to such changes is unknown. Furthermore, it is unclear to what extent vaccine-induced selective pressures drive capsular switching.Methods.Serotype and multilocus sequence typing data for 426 pneumococci dated from 1937 through 2007 were analyzed. Whole-genome sequence data for a subset of isolates were used to investigate capsular switching events.Results.We identified 36 independent capsular switch events, 18 of which were explored in detail with whole-genome sequence data. Recombination fragment lengths were estimated for 11 events and ranged from approximately 19.0 kb to ≥58.2 kb. Two events took place no later than 1960, and the imported DNA included the capsular locus and the nearby penicillin-binding protein genes pbp2x and pbp1a.Conclusions.Capsular switching has been a regular occurrence among pneumococcal populations throughout the past 7 decades. Recombination of large DNA fragments (>30 kb), sometimes including the capsular locus and penicillin-binding protein genes, predated both vaccine introduction and widespread antibiotic use. This type of recombination has likely been an intrinsic feature throughout the history of pneumococcal evolution.

Match Rates into Family Medicine among Regional Medical Campus Graduates, 2007-2009

Regional medical campuses (RMCs) are geographically separate from parent campuses, have administrative ties to deans' offices, and offer at least 4 third-year clerkships. This study sought to describe the match rates into family medicine for graduates of RMCs and non-RMCs. The authors obtained the 2007 to 2009 match lists from schools participating in the Association of American Medical College's Group on Regional Medical Campuses. RMC match numbers for family medicine were subtracted from the total number of family medicine matched US seniors as published by the National Residency Match Program. The outcome of interest was the relative frequencies of RMC and non-RMC graduates matching into family medicine. Between 2007 and 2009, 261 graduates from 29 RMCs accounted for 8% of all family medicine matches. During the study period, the match rate into family medicine for RMC graduates was 80% higher than that of non-RMC graduates (14.2% vs 7.9% for all 3 years). In 2009, only 3 of the RMCs had family medicine match rates lower than that of non-RMCs (7.5%). The RMC match rate into family medicine was nearly twice that of non-RMCs. RMCs may play a role in addressing physician workforce imbalances.

Evolving Picture of Invasive Pneumococcal Disease in Massachusetts Children

As expected, the heptavalent pneumococcal conjugate vaccine (PCV7) had a significant impact on invasive pneumococcal disease (IPD) in children. In addition to the substantial decline in IPD, increased disease due to nonvaccine serotypes and a changing clinical presentation emerged. The objective of this study is to describe these trends in IPD in the late PCV7-era. We report on continued, prospective, population-based surveillance of childhood IPD in Massachusetts children during the period 2007 to 2009 and make comparisons with the earlier 2001 to 2006 PCV7-era. Demographic and clinical data were collected for all cases. Streptococcus pneumoniae isolates from normally sterile sites were serotyped and further evaluated using antimicrobial susceptibility testing, multilocus sequence typing and eBURST analysis. IPD incidence rates are calculated by age, year and serotype. There were 326 cases of IPD between 2007 and 2009 in children < 18 years of age. Overall IPD incidence rate was 7.5 cases per 100,000 population and was not statistically different from the observed incidence in 2001 to 2006 (P > 0.05). As compared with the earlier period, the proportion of bacteremic pneumonia among all IPD cases was almost 3-fold greater in 2009 to 2010 (P < 0.01). PCV7 serotypes accounted for 7%, whereas the 13-valent pneumococcal conjugate vaccine serotypes accounted for 77% of all cases between 2007 and 2009. IPD due to serotypes 19A and 7F increased, and 19A and 7F were isolated in 41% and 20% of all IPD cases in the same period, respectively. Serotype 19A also comprised a majority of the penicillin- and ceftriaxone-resistant isolates. Analysis of multilocus sequence typing data showed a significant increase in ST191, ST695 and ST320 and a significant decrease in ST199 and ST180. The reduction in IPD after introduction of PCV7 persists in Massachusetts children; however, serotypes causing IPD have changed significantly in the last decade. Continued surveillance is necessary to determine the impact of 13-valent pneumococcal conjugate vaccine, as well as track potential changes in disease incidence and character due to non-13-valent pneumococcal conjugate vaccine serotypes.