Sara M. Reese

Transmission dynamics of Francisella tularensis subspecies and clades by nymphal Dermacentor variabilis (Acari: Ixodidae).

In the United States, the American dog tick, Dermacentor variabilis (Say) is considered an important biological vector of Francisella tularensis, the etiologic agent of tularemia. In this study, we evaluated the vector efficiency of nymphal D. variabilis infected as larvae with differing clades and subspecies (A1b, A2, and type B) of F. tularensis. In all cases, D. variabilis larvae were able to acquire, maintain, and transstadially transmit F. tularensis. Significant replication of the bacteria also occurred in infected nymphs. Transmission of F. tularensis to Swiss Webster mice was not observed with A1b, and low rates were observed with A2 (8.0%) and type B (13.5%). Negative effects on tick survivorship were also observed for A1b, A2, and type B infections. Our results provide evidence of a high fitness cost and low transmission rates during the immature stages, suggesting that D. variabilis may play a limited role in enzootic maintenance of F. tularensis.

An Acarologic Survey and Amblyomma americanum Distribution Map with Implications for Tularemia Risk in Missouri

In the United States, tickborne diseases occur focally. Missouri represents a major focus of several tickborne diseases that includes spotted fever rickettsiosis, tularemia, and ehrlichiosis. Our study sought to determine the potential risk of human exposure to human-biting vector ticks in this area. We collected ticks in 79 sites in southern Missouri during June 7-10, 2009, which yielded 1,047 adult and 3,585 nymphal Amblyomma americanum, 5 adult Amblyomma maculatum, 19 adult Dermacentor variabilis, and 5 nymphal Ixodes brunneus. Logistic regression analysis showed that areas posing an elevated risk of exposure to A. americanum nymphs or adults were more likely to be classified as forested than grassland, and the probability of being classified as elevated risk increased with increasing relative humidity during the month of June (30-year average). Overall accuracy of each of the two models was greater than 70% and showed that 20% and 30% of the state were classified as elevated risk for human exposure to nymphs and adults, respectively. We also found a significant positive association between heightened acarologic risk and counties reporting tularemia cases. Our study provides an updated distribution map for A. americanum in Missouri and suggests a wide-spread risk of human exposure to A. americanum and their associated pathogens in this region.

Identification of super-infected Aedes triseriatus mosquitoes collected as eggs from the field and partial characterization of the infecting La Crosse viruses.

BackgroundLa Crosse virus (LACV) is a pathogenic arbovirus that is transovarially transmitted by Aedes triseriatus mosquitoes and overwinters in diapausing eggs. However, previous models predicted transovarial transmission (TOT) to be insufficient to maintain LACV in nature.ResultsTo investigate this issue, we reared mosquitoes from field-collected eggs and assayed adults individually for LACV antigen, viral RNA by RT-PCR, and infectious virus. The mosquitoes had three distinct infection phenotypes: 1) super infected (SI+) mosquitoes contained infectious virus, large accumulations of viral antigen and RNA and comprised 17 of 17,825 (0.09%) of assayed mosquitoes, 2) infected mosquitoes (I+) contained no detectable infectious virus, lesser amounts of viral antigen and RNA, and comprised 3.7% of mosquitoes, and 3) non-infected mosquitoes (I-) contained no detectable viral antigen, RNA, or infectious virus and comprised 96.21% of mosquitoes. SI+ mosquitoes were recovered in consecutive years at one field site, suggesting that lineages of TOT stably-infected and geographically isolated Ae. triseriatus exist in nature. Analyses of LACV genomes showed that SI+ isolates are not monophyletic nor phylogenetically distinct and that synonymous substitution rates exceed replacement rates in all genes and isolates. Analysis of singleton versus shared mutations (Fu and Lis F*) revealed that the SI+ LACV M segment, with a large and significant excess of intermediate-frequency alleles, evolves through disruptive selection that maintains SI+ alleles at higher frequencies than the average mutation rate. A QTN in the LACV NSm gene was detected in SI+ mosquitoes, but not in I+ mosquitoes. Four amino acid changes were detected in the LACV NSm gene from SI+ but not I+ mosquitoes from one site, and may condition vector super infection. In contrast to NSm, the NSs sequences of LACV from SI+ and I+ mosquitoes were identical.ConclusionsSI+ mosquitoes may represent stabilized infections of Ae. triseriatus mosquitoes, which could maintain LACV in nature. A gene-for-gene interaction involving the viral NSm gene and a vector innate immune response gene may condition stabilized infection.

Collaboration for containment: Detection of OXA-23–like carbapenamase-producing Acinetobacter baumannii in Colorado

MRSA/VRE and non-MRSA/VRE patients in Martin et al are not included. Second, for rate calculation, we calculated the rate per 1,000 patient days, whereas Martin et al considered the rate per 1,000 admissions.Whether thishad any influenceonoutcomes is unknown. Similar to the previous study by Martin et al that indicated no change in the healthcare associated infection (HAI) rates of MRSA/VRE after elimination of CP, we also reported no significant change in HAI rates in MRSA/VRE patients after eliminating CP in our study. Thus, eliminating CP for MRSA/VRE patients is not associated with increased HAI rates with MRSA/ VRE and could improve patient safety outcomes. Our observation that MRSA/VRE patients are at higher risk of noninfectious adverse events argues the need for serious consideration of eliminating CP among MRSA/VRE patients.

Healthcare-Associated Infections in Colorado Dialysis Treatment Centers

Conclusions: To our knowledge, this is the first description of CLABSI and CLD data submission to the NHSN using the CDA file generation and upload method. The use of an ESS coupled with CDA functionality streamlines the event documentation and data submission process. Early adopters of this practice and the resultant errors highlighted opportunities for improvement in ESS and NHSN compatibility. It also emphasized the need to eliminate the intermediary, user-driven steps and develop a fully automated submission method.