The combination of CRISPR-MVLST and PFGE provides increased discriminatory power for differentiating human clinical isolates of Salmonella enterica subsp. enterica serovar Enteritidis.

Salmonella enterica subsp. enterica serovar Enteritidis (S. Enteritidis) is a major cause of foodborne salmonellosis. Rapid, efficient and accurate methods for identification are required to track specific strains of S. Enteritidis during outbreaks of human salmonellosis. By exploiting the hypervariable nature of virulence genes and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs), we previously developed a powerful sequence-based subtyping approach, designated CRISPR-MVLST. To substantiate the applicability of CRISPR-MVLST, we analyzed a broad set of S. Enteritidis isolates collected over a six-year period. Among 141 isolates we defined 22 Enteritidis Sequence Types (ESTs), the majority of which were novel. Notably, strains exhibiting the common PFGE pattern, JEGX01.0004 (characteristic of ∼40% of S. Enteritidis isolates in the United States), were separated into twelve distinct sequence types. Conversely, isolates of EST4, the most predominant EST we observed, comprised eight different PFGE patterns. Importantly, we showed that some genotypes that were previously associated with the food supply chain at the farm level have now been identified in clinical samples. CRISPR sequence data shows subtle but distinct differences among different alleles of S. Enteritidis, suggesting that evolution of these loci occurs vertically, as opposed to previously reported evolution by spacer acquisition in other bacteria.

Outbreak of influenza A (H3N2) variant virus infection among attendees of an agricultural fair, Pennsylvania, USA, 2011.

During August 2011, influenza A (H3N2) variant [A(H3N2)v] virus infection developed in a child who attended an agricultural fair in Pennsylvania, USA; the virus resulted from reassortment of a swine influenza virus with influenza A(H1N1)pdm09. We interviewed fair attendees and conducted a retrospective cohort study among members of an agricultural club who attended the fair. Probable and confirmed cases of A(H3N2)v virus infection were defined by serology and genomic sequencing results, respectively. We identified 82 suspected, 4 probable, and 3 confirmed case-patients who attended the fair. Among 127 cohort study members, the risk for suspected case status increased as swine exposure increased from none (4%; referent) to visiting swine exhibits (8%; relative risk 2.1; 95% CI 0.2-53.4) to touching swine (16%; relative risk 4.4; 95% CI 0.8-116.3). Fairs may be venues for zoonotic transmission of viruses with epidemic potential; thus, health officials should investigate respiratory illness outbreaks associated with agricultural events.

Measles outbreak associated with an international youth sporting event in the United States, 2007.

BACKGROUND: Despite elimination of endemic measles in the United States (US), outbreaks associated with imported measles continue to occur. In 2007, the initiation of a multistate measles outbreak was associated with an imported case occurring in a participant at an international youth sporting event held in Pennsylvania. METHODS: Case finding and contact tracing were conducted. Control measures included isolating ill persons and administering postexposure prophylaxis to exposed persons without documented measles immunity. Laboratory evaluation of suspected cases and contacts included measles serologic testing, viral culture, detection of viral RNA by reverse-transcription polymerase chain reaction, and viral genotyping. RESULTS: The index case occurred in a child from Japan aged 12 years. Contact tracing among 1250 persons in 8 states identified 7 measles cases; 5 (71%) cases occurred among persons without documented measles vaccination. Epidemiologic and laboratory investigation supported a single chain of transmission, linking the outbreak to contemporaneous measles virus genotype D5 transmission in Japan. Of the 471 event participants, 193 (41%) lacked documentation of presumed measles immunity, 94 (49%) of 193 were US-resident adults, 19 (10%) were non-US-resident adults (aged >18 years), and 80 (41%) were non-US-resident children. DISCUSSION: Measles outbreaks associated with imported disease are likely to continue in the US. Participants in international events, international travelers, and persons with routine exposure to such travelers might be at greater risk of measles. To reduce the impact of imported cases, high measles, mumps, and rubella vaccine coverage rates should be maintained throughout the US, and support should continue for global measles control and elimination.