We determined whether Francisella spp. are present in water, sediment, and soil from an active tularemia natural focus on Martha’s Vineyard, Massachusetts, during a multiyear outbreak of pneumonic tularemia. Environmental samples were tested by polymerase chain reaction (PCR) targeting Francisella species 16S rRNA gene and succinate dehydrogenase A (sdhA) sequences; evidence of the agent of tularemia was sought by amplification of Francisella tularensis-specific sequences for the insertion element ISFTu2, 17-kDa protein gene tul4, and the 43-kDa outer membrane protein gene fopA. Evidence of F. tularensis subsp. tularensis, the causative agent of the human infections in this outbreak, was not detected from environmental samples despite its active transmission among ticks and animals in the sampling site. Francisella philomiragia was frequently detected from a brackish-water pond using Francisella species PCR targets, and subsequently F. philomiragia was isolated from an individual brackish-water sample. Distinct Francisella sp. sequences that are closely related to F. tularensis and Francisella novicida were detected from samples collected from the brackish-water pond. We conclude that diverse Francisella spp. are present in the environment where human cases of pneumonic tularemia occur.

Cross-resistance in rifamycins has been observed in rifampin (RIF)-resistant Mycobacterium tuberculosis complex isolates; some rpoB mutations do not confer broad in vitro rifamycin resistance. We examined 164 isolates, of which 102 were RIF-resistant, for differential resistance between RIF and rifabutin (RFB). A total of 42 unique single mutations or combinations of mutations were detected. The number of unique mutations identified exceeded that reported in any previous study. RFB and RIF MICs up to 8 µg/ml by MGIT 960 were studied; the cut-off values for susceptibility to RIF and RFB were 1 µg/ml and 0.5 µg/ml, respectively. We identified 31 isolates resistant to RIF but susceptible to RFB with the mutations, D516V, D516F, 518 deletion, S522L, H526A, H526C, H526G, H526L and two dual mutations (S522L+K527R and H526S+K527R). Clinical investigations using RFB to treat MDR TB cases harboring those mutations are recommended.

Deer keds (Lipoptena cervi) are thought to have been introduced into New England from Europe during the 1800s. We sought to determine whether L. cervi from Massachusetts deer contained evidence of infection by Bartonella schoenbuchensis, which appears to be maintained by L. cervi in Europe. Five of 6 keds were found to contain B. schoenbuchensis DNA, and 2 deer ticks cofeeding on deer with such keds did as well. The detection of Bartonella DNA in deer ticks probably represents contamination by infected deer blood.

Martha’s Vineyard (MV), Massachusetts has been the location of two outbreaks of pneumonic tularemia; landscaping activities have been associated with risk, suggesting environmental inhalation exposure. We determined whether salinity or other components of brackish-water present in a location with endemic tularemia may prolong survival of F. tularensis. In addition, we demonstrate for the first time that F. tularensis Type A appears similar to Type B with respect to environmental stability. The results of this study suggest an explanation for why MV is the site of pneumonic tularemia transmission as opposed to sites in the southcentral USA, where tularemia is more commonly reported: Bacteria may be more prone to surviving in salt-influenced soil or moisture in the island setting.

The role of lone star ticks as vectors for Rocky Mountain spotted fever (RMSF) remains poorly described. We compared the entomological inoculation rates (EIRs) for Rickettsia spp. for representative sites in Missouri and Kansas, states that frequently report RMSF each year. Host-seeking ticks were collected during 2006 and pooled tick homogenates analyzed by polymerase chain reaction to detect probable R. rickettsii, with confirmation for multiple gene targets performed on individual ticks from pools that screened positive. Of 870 adult and nymphal lone star ticks, Amblyomma americanum (L.), 0.46% contained DNA of Rickettsia rickettsii. Interestingly, two of these positive ticks were concurrently infected by R. amblyommii. More than 90% of lone star tick pools contained R. amblyommii DNA. Of 169 dog ticks that were analyzed, none were infected by R. rickettsii. The entomological inoculation rate for spotted fever group (SFG) rickettsiae within lone star ticks was an order of magnitude greater than that for dog ticks. We conclude that lone star ticks may be epidemiologically significant vectors of Rocky Mountain spotted fever and of spotted fever group rickettsiae.