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July 7, 2019

Candida auris for the clinical microbiology laboratory: Not your grandfather’s Candida species

Candida auris is a newly emerging species that was first identified in Asia in 2009 but has rapidly spread across the world. C. auris differs from most other Candida species in that antifungal resistance is the norm rather than the exception, it is a commensal of human skin rather than the human gut, and it can be easily transmitted from person to person in a health care setting. This review discusses the emergence of C. auris, global epidemiology, identification, antifungal susceptibility testing, and precautions to be taken when it is identified from a patient specimen.


July 7, 2019

Genomic analysis of factors associated with low prevalence of antibiotic resistance in extraintestinal pathogenic Escherichia coli sequence type 95 strains.

Extraintestinal pathogenic Escherichia coli (ExPEC) strains belonging to multilocus sequence type 95 (ST95) are globally distributed and a common cause of infections in humans and domestic fowl. ST95 isolates generally show a lower prevalence of acquired antimicrobial resistance than other pandemic ExPEC lineages. We took a genomic approach to identify factors that may underlie reduced resistance. We fully assembled genomes for four ST95 isolates representing the four major fimH-based lineages within ST95 and also analyzed draft-level genomes from another 82 ST95 isolates, largely from the western United States. The fully assembled genomes of antibiotic-resistant isolates carried resistance genes exclusively on large (>90-kb) IncFIB/IncFII plasmids. These replicons were common in the draft genomes as well, particularly in antibiotic-resistant isolates, but we also observed multiple instances of a smaller (8.3-kb) ampicillin resistance plasmid that had been previously identified in Salmonella enterica. Among ST95 isolates, pansusceptibility to antibiotics was significantly associated with the fimH6 lineage and the presence of homologs of the previously identified 114-kb IncFIB/IncFII plasmid pUTI89, both of which were also associated with reduced carriage of other plasmids. Potential mechanistic explanations for lineage- and plasmid-specific effects on the prevalence of antibiotic resistance within the ST95 group are discussed. IMPORTANCE Antibiotic resistance in bacterial pathogens is a major public health concern. This work was motivated by the observation that only a small proportion of ST95 isolates, a major pandemic lineage of extraintestinal pathogenic E. coli, have acquired antibiotic resistance, in contrast to many other pandemic lineages. Understanding bacterial genetic factors that may prevent acquisition of resistance could contribute to the development of new biological, medical, or public health strategies to reduce antibiotic-resistant infections.


July 7, 2019

Complete genome sequences of three Salmonella enterica subsp. enterica serovar Saintpaul isolates associated with a 2013 multistate outbreak in the United States.

In 2013, a multistate outbreak of Salmonella enterica subsp. enterica serovar Saintpaul from cucumber caused 84 cases of salmonellosis in the United States. In this announcement, we report the complete genome sequences of three clinical Salmonella Saintpaul isolates associated with the 2013 outbreak. Copyright © 2017 Yao et al.


July 7, 2019

Emergence of a new Neisseria meningitidis clonal complex 11 lineage 11.2 clade as an effective urogenital pathogen.

Neisseria meningitidis (Nm) clonal complex 11 (cc11) lineage is a hypervirulent pathogen responsible for outbreaks of invasive meningococcal disease, including among men who have sex with men, and is increasingly associated with urogenital infections. Recently, clusters of Nm urethritis have emerged primarily among heterosexual males in the United States. We determined that nonencapsulated meningococcal isolates from an ongoing Nm urethritis outbreak among epidemiologically unrelated men in Columbus, Ohio, are linked to increased Nm urethritis cases in multiple US cities, including Atlanta and Indianapolis, and that they form a unique clade (the US Nm urethritis clade, US_NmUC). The isolates belonged to the cc11 lineage 11.2/ET-15 with fine type of PorA P1.5-1, 10-8; FetA F3-6; PorB 2-2 and express a unique FHbp allele. A common molecular fingerprint of US_NmUC isolates was an IS1301 element in the intergenic region separating the capsule ctr-css operons and adjacent deletion of cssA/B/C and a part of csc, encoding the serogroup C capsule polymerase. This resulted in the loss of encapsulation and intrinsic lipooligosaccharide sialylation that may promote adherence to mucosal surfaces. Furthermore, we detected an IS1301-mediated inversion of an ~20-kb sequence near the cps locus. Surprisingly, these isolates had acquired by gene conversion the complete gonococcal denitrification norB-aniA gene cassette, and strains grow well anaerobically. The cc11 US_NmUC isolates causing urethritis clusters in the United States may have adapted to a urogenital environment by loss of capsule and gene conversion of the Neisseria gonorrheae norB-aniA cassette promoting anaerobic growth.


July 7, 2019

Phylogeography of Burkholderia pseudomallei isolates, Western Hemisphere.

The bacterium Burkholderia pseudomallei causes melioidosis, which is mainly associated with tropical areas. We analyzed single-nucleotide polymorphisms (SNPs) among genome sequences from isolates of B. pseudomallei that originated in the Western Hemisphere by comparing them with genome sequences of isolates that originated in the Eastern Hemisphere. Analysis indicated that isolates from the Western Hemisphere form a distinct clade, which supports the hypothesis that these isolates were derived from a constricted seeding event from Africa. Subclades have been resolved that are associated with specific regions within the Western Hemisphere and suggest that isolates might be correlated geographically with cases of melioidosis. One isolate associated with a former World War II prisoner of war was believed to represent illness 62 years after exposure in Southeast Asia. However, analysis suggested the isolate originated in Central or South America.


July 7, 2019

The blaOXA-23-associated transposons in the genome of Acinetobacter spp. represent an epidemiological situation of the species encountering carbapenems.

High rates of carbapenem resistance in the human pathogen Acinetobacter baumannii threaten public health and need to be scrutinized.A total of 356 A. baumannii and 50 non-baumannii Acinetobacter spp. (NBA) strains collected in 2013 throughout South Korea were studied. The type of blaOXA-23 transposon was determined by PCR mapping and molecular epidemiology was assessed by MLST. Twelve representative strains and two comparative A. baumannii were entirely sequenced by single-molecule real-time sequencing.The carbapenem resistance rate was 88% in A. baumannii, mainly due to blaOXA-23, with five exceptional cases associated with ISAba1-blaOXA-51-like. The blaOXA-23 gene in A. baumannii was carried either by Tn2006 (44%) or Tn2009 (54%), with a few exceptions carried by Tn2008 (1.6%). Of the NBA strains, 14% were resistant to carbapenems, two with blaOXA-58 and five with blaOXA-23 associated with Tn2006. The Tn2006-possessing strains belonged to various STs, whereas Tn2008- and Tn2009-possessing strains were limited to ST208 and ST191, respectively. The three transposons were often multiplied in the chromosome, and the gene copy number and the carbapenem MICs presented linear relationships either very strongly for Tn2008 or moderately for Tn2006 and Tn2009.The dissemination of Tn2006 was facilitated by its capability for intercellular transfer and that of Tn2009 was attributable to successful dissemination of the ST191 bacterial host carrying the transposon. Tn2008 was infrequent because of its insufficient ability to undergo intercellular transfer and the scarce bacterial host A. baumannii ST208. Gene amplification is an adaptive mechanism for bacteria that encounter antimicrobial drugs.© The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.


July 7, 2019

Benchmark datasets for phylogenomic pipeline validation, applications for foodborne pathogen surveillance.

As next generation sequence technology has advanced, there have been parallel advances in genome-scale analysis programs for determining evolutionary relationships as proxies for epidemiological relationship in public health. Most new programs skip traditional steps of ortholog determination and multi-gene alignment, instead identifying variants across a set of genomes, then summarizing results in a matrix of single-nucleotide polymorphisms or alleles for standard phylogenetic analysis. However, public health authorities need to document the performance of these methods with appropriate and comprehensive datasets so they can be validated for specific purposes, e.g., outbreak surveillance. Here we propose a set of benchmark datasets to be used for comparison and validation of phylogenomic pipelines.We identified four well-documented foodborne pathogen events in which the epidemiology was concordant with routine phylogenomic analyses (reference-based SNP and wgMLST approaches). These are ideal benchmark datasets, as the trees, WGS data, and epidemiological data for each are all in agreement. We have placed these sequence data, sample metadata, and “known” phylogenetic trees in publicly-accessible databases and developed a standard descriptive spreadsheet format describing each dataset. To facilitate easy downloading of these benchmarks, we developed an automated script that uses the standard descriptive spreadsheet format.Our “outbreak” benchmark datasets represent the four major foodborne bacterial pathogens (Listeria monocytogenes, Salmonella enterica, Escherichia coli, and Campylobacter jejuni) and one simulated dataset where the “known tree” can be accurately called the “true tree”. The downloading script and associated table files are available on GitHub: https://github.com/WGS-standards-and-analysis/datasets.These five benchmark datasets will help standardize comparison of current and future phylogenomic pipelines, and facilitate important cross-institutional collaborations. Our work is part of a global effort to provide collaborative infrastructure for sequence data and analytic tools-we welcome additional benchmark datasets in our recommended format, and, if relevant, we will add these on our GitHub site. Together, these datasets, dataset format, and the underlying GitHub infrastructure present a recommended path for worldwide standardization of phylogenomic pipelines.


July 7, 2019

A case of decreased susceptibility to ceftriaxone in Neisseria gonorrhoeae in the absence of a mosaic penicillin-binding protein 2 (penA) allele.

We report a case of Neisseria gonorrhoeae with a non-mosaic penA allele that exhibited decreased susceptibility to extended-spectrum cephalosporins, including a ceftriaxone minimum inhibitory concentration of 0.5 µg/mL. An analysis of resistance determinants suggested that the observed phenotype might have resulted from the combined effects of mutations in multiple genes.


July 7, 2019

Complete genome sequence of Mycobacterium chimaera strain CDC2015-22-71.

Mycobacterium chimaera is a nontuberculous mycobacterium species commonly found in the environment. Here, we report the first complete genome sequence of a strain from the investigation of invasive infections following open-heart surgeries that used contaminated LivaNova Sorin Stockert 3T heater-cooler devices. Copyright © 2017 Hasan et al.


July 7, 2019

Complete genome sequence of Clostridioides difficile epidemic strain DH/NAP11/106/ST-42, isolated from stool from a pediatric patient with diarrhea.

We report here the complete genome sequence of Clostridioides difficile strain DH/NAP11/106/ST-42, which is now the most common strain causing C. difficile infection among U.S. adults. This strain was isolated from the stool from a hospitalized pediatric patient with frequent relapses of C. difficile infection. Copyright © 2017 Ozer et al.


July 7, 2019

A nosocomial outbreak of extensively drug resistant (XDR) Acinetobacter baumannii isolates containing blaOXA-237 encoded on a plasmid.

Carbapenem antibiotics are among the mainstay for treating infections caused by Acinetobacter baumannii, especially in the Northwest United States where carbapenem resistant A. baumannii remain relatively rare. However, between June 2012 and October 2014, an outbreak of carbapenem-resistant A. baumannii occurred in 16 patients from 5 healthcare facilities in the state of Oregon. All isolates were defined as extensively-drug resistant (XDR). MLST revealed that the isolates belonged to sequence type 2 (international clone 2, IC2), and were greater than 95% similar by rep-PCR analysis. Multiplex PCR revealed the presence of a blaOXA carbapenemase gene, later identified as blaOXA-237 Whole genome sequencing of all isolates revealed a well-supported separate branch within a global A. baumannii phylogeny. Pacific Biosciences (PacBio) SMRT sequencing was also performed on one isolate to gain insight into the genetic location of the carbapenem resistance gene. We discovered that blaOXA-237, flanked on either side by ISAba1 elements in opposite orientations, was carried by a 15,198 bp plasmid designated pORAB01-3, and was present in all 16 isolates. The plasmid also contained genes encoding for: a TonB-dependent receptor, septicolysin, a type IV secretory system conjugative DNA transfer family protein, an integrase, a RepB family plasmid DNA replication initiator protein, an a/ß hydrolase, and a BrnT/BrnA type II toxin-antitoxin system. This is the first reported outbreak associated with this specific carbapenemase. Particularly worrisome is that blaOXA-237 was plasmid encoded and found in the most prominent worldwide clonal group IC2, potentially giving pORAB01-3 great capacity for future widespread dissemination. Copyright © 2017 American Society for Microbiology.


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