We sequenced the genomes of 10 Salmonella enterica serovar Infantis isolates containing bla CTX-M-65 obtained from chicken, cattle, and human sources collected between 2012 and 2015 in the United States through routine National Antimicrobial Resistance Monitoring System (NARMS) surveillance and product sampling programs. We also completely assembled the plasmids from four of the isolates. All isolates had a D87Y mutation in the gyrA gene and harbored between 7 and 10 resistance genes [aph(4)-Ia, aac(3)-IVa, aph(3=)-Ic, bla fosA3, floR, dfrA14, sul1, tetA, aadA1] located in two distinct sites of a megaplasmid (ϳ316 to 323 kb) similar to that described in a bla CTX-M-65 -positive S. Infantis isolate from a patient in Italy. High-quality single nucleotide polymorphism (hqSNP) analysis revealed that all U.S. isolates were closely related, separated by only 1 to 38 pairwise high-quality SNPs, indicating a high likelihood that strains from humans, chickens, and cattle recently evolved from a common ancestor. The U.S. isolates were genetically similar to the bla CTX-M-65 -positive S. Infantis isolate from Italy, with a separation of 34 to 47 SNPs. This is the first report of the bla CTX-M-65 gene and the pESI (plasmid for emerging S. Infantis)-like megaplasmid from S. Infantis in the United States, and it illustrates the importance of applying a global One Health human and animal perspective to combat antimicrobial resistance.

Raw produce, including cantaloupe, can serve as a vehicle for listeriosis. This outbreak highlights the importance of preventing produce contamination within farm and processing environments.

Vibrio vulnificus is a human pathogen that produces lethal septicemia in susceptible persons, and the primary virulence factor for this organism is capsular polysaccharide (CPS). The role of the capsule in V. vulnificus biofilms was examined under a variety of conditions, by using either defined CPS mutants or spontaneous CPS expression phase variants derived from multiple strains. CPS expression was shown to inhibit attachment and biofilm formation, which contrasted with other studies describing polysaccharides as integral to biofilms in related species.Vibrio vulnificus is indigenous to estuarine environments (9,18,24,36,43) and causes human infections associated with raw oyster consumption (3). Pathogenesis was recently reviewed, and virulence is primarily attributed to capsular polysaccharide (CPS) expression (34). Opaque (O) colony morphology, indicative of a virulent, encapsulated phenotype, exhibits reversible phase variation to translucent (T) colony types with reduced CPS expression and decreased virulence (30,47). Defined mutations in the CPS operon confirmed the relationship of CPS and virulence (28,42,44,45). Vibrio spp. attach to algae and zooplankton (5,15,16,17,19,22), and V. vulnificus may be more concentrated in oysters and fish which feed on these organisms (9,29,36,43). Microbial communities attached to nutrient-rich surfaces are generally referred to as biofilms and are thought to engage in complex signaling for expression of CPS and other factors (7,25,26). For example, V. cholerae biofilms require production of polysaccharide, pili, and flagella (5,21,23,37,38,39,46). Biofilms for V. vulnificus biotype 2 eel pathogens were recently described (20); however, this group differs from human pathogens of biotype 1 in that biotype 2 lipopolysaccharide (LPS) is homogeneous (serovar E) and CPS may not always be required for virulence (2). The role of CPS in biofilms of either biotype has not been addressed; therefore, our studies examined V. vulnificus biofilms in O versus T phase variants and CPS mutants that differed in their abilities to produce capsular polysaccharide.CPS expression inhibits V. vulnificus biofilm formation. Surface CPS displays a continuum of expression among V. vulnificus strains (44). Strains for this study are detailed in Table 1 and were stored at Ϫ70°C in 50% glycerol to ensure stability of phase variants. O strains are completely encapsulated, while T strains either are acapsular or have reduced, patchy capsules. Mutant strains are acapsular but differ in CPS biosynthesis: CVD752 contains a polar transposon mutation in the CPS operon that eliminates biosynthesis, while MO6-24/31T contains a nonpolar mutation, specifically targeting the CPS transport function of the wza gene, and can synthesize CPS but is unable to transport it to the cell surface (44, 45).Biofilm formation on abiotic surfaces was examined by crystal violet absorption assays, and the relative biofilm content was estimated from the concentration of dye eluted from destained cells and matrix (32). Examination...

We identified a novel serotype 1/2a outbreak strain and 2 novel epidemic clones of Listeria monocytogenes while investigating a foodborne outbreak of listeriosis associated with consumption of cantaloupe during 2011 in the United States. Comparative analyses of strains worldwide are essential to identification of novel outbreak strains and epidemic clones.