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Tick-borne relapsing fever and Borrelia hermsii, Los Angeles County, California, USA.

ABSTRACT: The primary cause of tick-borne relapsing fever in western North America is Borrelia hermsii, a rodent-associated spirochete transmitted by the fast-feeding soft tick Ornithodoros hermsi. We describe a patient who had an illness consistent with relapsing fever after exposure in the mountains near Los Angeles, California, USA. The patient's convalescent-phase serum was seropositive for B. hermsii but negative for several other vector-borne bacterial pathogens. Investigations at the exposure site showed the presence of O. hermsi ticks infected with B. hermsii and the presence of rodents that were seropositive for the spirochete. We determined that this tick-borne disease is endemic to the San Gabriel Mountains near the greater Los Angeles metropolitan area.

SUBMITTER: Schwan TG

PROVIDER: S-EPMC2744237 | biostudies-literature | 2009 Jul

REPOSITORIES: biostudies-literature

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Tick-borne relapsing fever and Borrelia hermsii, Los Angeles County, California, USA.

Schwan Tom G TG Raffel Sandra J SJ Schrumpf Merry E ME Schrumpf Merry E ME Webster Larry S LS Marques Adriana R AR Spano Robyn R Rood Michael M Burns Joe J Hu Renjie R

Emerging infectious diseases 20090701 7

The primary cause of tick-borne relapsing fever in western North America is Borrelia hermsii, a rodent-associated spirochete transmitted by the fast-feeding soft tick Ornithodoros hermsi. We describe a patient who had an illness consistent with relapsing fever after exposure in the mountains near Los Angeles, California, USA. The patient's convalescent-phase serum was seropositive for B. hermsii but negative for several other vector-borne bacterial pathogens. Investigations at the exposure site ...[more]

PMID: 19624916

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Project description:An unrecognized focus of tick-borne relapsing fever caused by Borrelia hermsii was identified in 2002 when five people became infected on Wild Horse Island in Flathead Lake, Montana. The terrestrial small mammal community on the island is composed primarily of pine squirrels (Tamiasciurus hudsonicus) and deer mice (Peromyscus maniculatus), neither of which was known as a natural host for the spirochete. Thus a 3-year study was performed to identify small mammals as hosts for B. hermsii.Small mammals were captured alive on two island and three mainland sites, blood samples were collected and examined for spirochetes, and serological tests performed to detect anti-B. hermsii antibodies. Ornithodoros hermsi ticks were collected and fed on laboratory mice to assess infection. Genomic DNA samples from spirochetes isolated from infected mammals and ticks were analyzed by multilocus sequence typing.Eighteen pine squirrels and one deer mouse had detectable spirochetemias when captured, from which 12 isolates of B. hermsii were established. Most pine squirrels were seropositive, and the five species of sciurids combined had a significantly higher prevalence of seropositive animals than did the other six small mammal species captured. The greater diversity of small mammals on the mainland in contrast to the islands demonstrated that other species in addition to pine squirrels were also involved in the maintenance of B. hermsii at Flathead Lake. Ornithodoros hermsi ticks produced an additional 12 isolates of B. hermsii and multilocus sequence typing identified both genomic groups of B. hermsii described previously, and identified a new genomic subdivision. Experimental infections of deer mice with two strains of B. hermsii demonstrated that these animals were susceptible to infection with spirochetes belonging to Genomic Group II but not Genomic Group I.Pine squirrels are the primary hosts for the maintenance of B. hermsii on the islands in Flathead Lake, however serological evidence showed that numerous additional species are also involved on the mainland. Future studies testing the susceptibility of several small mammal species to infection with different genetic types of B. hermsii will help define their role as hosts in this and other endemic foci.

Project description:BackgroundAntibiotic resistant strains of Acinetobacter baumannii have been responsible for an increasing number of nosocomial infections including bacteremia and ventilator-associated pneumonia. In this study, we analyzed 38 isolates of A. baumannii obtained from two hospital outbreaks in Los Angeles County for the molecular epidemiology, antimicrobial susceptibility and resistance determinants.MethodsPulsed field gel electrophoresis, tri-locus multiplex PCR and multi-locus sequence typing (Pasteur scheme) were used to examine clonal relationships of the outbreak isolates. Broth microdilution method was used to determine antimicrobial susceptibility of these isolates. PCR and subsequent DNA sequencing were employed to characterize antibiotic resistance genetic determinants.ResultsTrilocus multiplex PCR showed these isolates belong to Global Clones I and II, which were confirmed to ST1 and ST2, respectively, by multi-locus sequence typing. Pulsed field gel electrophoresis analysis identified two clonal clusters, one with 20 isolates (Global Clone I) and the other with nine (Global Clone II), which dominated the two outbreaks. Antimicrobial susceptibility testing using 14 antibiotics indicated that all isolates were resistant to antibiotics belonging to four or more categories of antimicrobial agents. In particular, over three fourth of 38 isolates were found to be resistant to both imipenem and meropenem. Additionally, all isolates were found to be resistant to piperacillin, four cephalosporin antibiotics, ciprofloxacin and levofloxacin. Resistance phenotypes of these strains to fluoroquinolones were correlated with point mutations in gyrA and parC genes that render reduced affinity to target proteins. ISAba1 was detected immediately upstream of the bla OXA-23 gene present in those isolates that were found to be resistant to both carbapenems. Class 1 integron-associated resistance gene cassettes appear to contribute to resistance to aminoglycoside antibiotics.ConclusionThe two outbreaks were found to be dominated by two clonal clusters of A. baumannii belonging to MLST ST1 and ST2. All isolates were resistant to antibiotics of at least four categories of antimicrobial agents, and their antimicrobial susceptibility profiles correlate well with genetic determinants. The results of this study will facilitate our understanding of the molecular epidemiology, antimicrobial susceptibility and mechanisms of resistance of A. baumannii obtained from Los Angeles hospitals.

Project description:ImportanceDescribing the changes in trauma volume and injury patterns during the course of the coronavirus disease 2019 (COVID-19) pandemic could help to inform policy development and hospital resource planning.ObjectiveTo examine trends in trauma admissions throughout Los Angeles County (LAC) during the pandemic.Design, setting, and participantsIn this cohort study, all trauma admissions to the 15 verified level 1 and level 2 trauma centers in LAC from January 1 to June 7, 2020 were reviewed. All trauma admissions from the same period in 2019 were used as historical control. For overall admissions, the study period was divided into 3 intervals based on daily admission trend analysis (January 1 through February 28, March 1 through April 9, April 10 through June 7). For the blunt trauma subgroup analysis, the study period was divided into 3 similar intervals (January 1 through February 27, February 28 through April 5, April 6 through June 7).ExposuresCOVID-19 pandemic.Main outcomes and measuresTrends in trauma admission volume and injury patterns.ResultsA total of 6777 patients in 2020 and 6937 in 2019 met inclusion criteria. Of those admitted in 2020, the median (interquartile range) age was 42 (28-61) years and 5100 (75.3%) were men. Mechanisms of injury were significantly different between the 2 years, with a higher incidence of penetrating trauma and fewer blunt injuries in 2020 compared with 2019 (penetrating: 1065 [15.7%] vs 1065 [15.4%]; blunt: 5309 [78.3%] vs 5528 [79.7%]). Overall admissions by interval in 2020 were 2681, 1684, and 2412, whereas in 2019 they were 2462, 1862, and 2613, respectively. There was a significant increase in overall admissions per week during the first interval (incidence rate ratio [IRR], 1.02; 95% CI, 1.002-1.04; P = .03) followed by a decrease in the second interval (IRR, 0.92; 95% CI, 0.90-0.94; P < .001) and, finally, an increase in the third interval (IRR, 1.05; CI, 1.03-1.07; P < .001). On subgroup analysis, blunt admissions followed a similar pattern to overall admissions, while penetrating admissions increased throughout the study period.Conclusions and relevanceIn this study, trauma centers throughout LAC experienced a significant change in injury patterns and admission trends during the COVID-19 pandemic. A transient decrease in volume was followed by a quick return to baseline levels. Trauma centers should prioritize maintaining access, capacity, and functionality during pandemics and other national emergencies.

Dataset Information

Tick-borne relapsing fever and Borrelia hermsii, Los Angeles County, California, USA.

Publications

Tick-borne relapsing fever and Borrelia hermsii, Los Angeles County, California, USA.

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