Genotyping and Axenic Growth ofCoxiella burnetiiIsolates Found in the United States Environment

Abstract

Coxiella burnetii is a gram-negative bacterium that is the etiologic agent of the zoonotic disease Q fever. Common reservoirs of C. burnetii include sheep, goats, and cattle. These animals shed C. burnetii into the environment, and humans are infected by inhalation of aerosols. A survey of 1622 environmental samples taken across the United States in 2006-2008 found that 23.8% of the samples contained C. burnetii DNA. To identify the strains circulating in the U.S. environment, DNA from these environmental samples was genotyped using an SNP-based approach to derive sequence types (ST) that are also compatible with multispacer sequence typing methods. Three different sequence types were observed in 31 samples taken from 19 locations. ST8 was associated with goats and ST20 with dairy cattle. ST16/26 was detected in locations with exposure to various animals and also in locations with no direct animal contact. Viable isolates were obtained for all three sequence types, but only the ST20 and ST16/26 isolates grew in acidified citrate cysteine medium (ACCM)-2 axenic media. Examination of a variety of isolates with different sequence types showed that ST8 and closely related isolates did not grow in ACCM-2. These results suggest that a limited number of C. burnetii sequence types are circulating in the U.S. environment and these strains have close associations with specific reservoir species. Growth in ACCM-2 may not be suitable for isolation of many C. burnetii strains.

Transmission of Coxiella burnetii by ingestion in mice

“…In the absence of additional test strains within each sequence type, it is not possible to demonstrate conclusively that virulence is distinct among these groups. However, these strains show remarkably consistent species association and in vitro growth characteristics, which supports the notion that they may have similar characteristics in vivo as well [4,28]. Furthermore, similar patterns of virulence were observed in a study utilising a guinea pig IP model, where NM and another ST16, Ohio, were determined to be the most virulent, followed by Q195, an ST20, and finally the ST8s, Q238 and Priscilla [23].…”

The anti-apoptotic Coxiella burnetii effector protein AnkG is a strain specific virulence factor

“…As representative for the first group, we chose Nine Mile I (NMI) and for the second and third groups 19/34 and Z3574-1/92, respectively. First, we had to establish axenic growth of these isolates, as axenic media does not support growth of all C. burnetii strains 35 . While growth of NMI in ACCM-2 and ACCM-D has been shown, growing 19/34 and Z3574-1/92 in axenic media has never been attempted.…”

Swab cloths as a tool for revealing environmental contamination by Q fever in ruminant farms

“…Although historical data suggest that C. burnetii might be able to resist for several months at room temperature (Williams, ), new data are needed to assess the infectivity of qPCR‐detected bacteria in environmental samples. Interestingly, the presence of infectious bacteria was demonstrated in the USA for a small number of environmental samples using intraperitoneal inoculation of BALB/c mice (Kersh et al., , ) or acidified citrate cysteine medium (Kersh et al., ). However, due to both ethical and technical reasons, such studies can only be performed on a limited number of samples.…”

“…Interestingly, the presence of infectious bacteria was demonstrated in the USA for a small number of environmental samples using intraperitoneal inoculation of BALB/c mice (Kersh et al, 2010(Kersh et al, , 2013 or acidified citrate cysteine medium (Kersh et al, 2016). However, (Selim, Yang, Rousset, Thiéry, & Sidi-Boumedine, 2018), or designing molecular markers of viability will help in assessing the potential public health impact of environmental contamination by C. burnetii.…”