Oropharyngeal Tularemia Outbreak Associated with Drinking Contaminated Tap Water, Turkey, July-September 2013

Tularemia From Veterinary Occupational Exposure

Tularemia is a disease caused by Francisella tularensis, a highly infectious bacteria that can be transmitted to humans by direct contact with infected animals. Because of the potential for zoonotic transmission of F. tularensis, veterinary occupational risk is a concern. Here, we report on a human case of tularemia in a veterinarian after an accidental needlestick injury during abscess drainage in a sick dog. The veterinarian developed ulceroglandular tularemia requiring hospitalization but fully recovered after abscess drainage and a course of effective antibiotics. To systematically assess veterinary occupational transmission risk of F. tularensis, we conducted a survey of veterinary clinical staff after occupational exposure to animals with confirmed tularemia. We defined a high-risk exposure as direct contact to the infected animal's body fluids or potential aerosol inhalation without use of standard personal protective equipment (PPE). Survey data included information on 20 veterinary occupational exposures to animals with F. tularensis in 4 states. Veterinarians were the clinical staff most often exposed (40%), followed by veterinarian technicians and assistants (30% and 20%, respectively). Exposures to infected cats were most common (80%). Standard PPE was not used during 80% of exposures; a total of 7 exposures were categorized as high risk. Transmission of F. tularensis in the veterinary clinical setting is possible but overall risk is likely low. Veterinary clinical staff should use standard PPE and employ environmental precautions when handling sick animals to minimize risk of tularemia and other zoonotic infections; postexposure prophylaxis should be considered after high-risk exposures to animals with suspected or confirmed F. tularensis infection to prevent tularemia.

Optimized MALDI TOF Mass Spectrometry Identification of Francisella tularensis Subsp. holarctica

Francisella tularensis is a tier 1 agent causing the zoonosis tularemia. This highly infectious Gram-negative bacterium is occasionally isolated from human samples (especially blood samples) in routine clinical microbiology laboratories. A rapid and accurate method for identifying this pathogen is needed in order to optimize the infected patient’s healthcare management and prevent contamination of the laboratory personnel. MALDI TOF mass spectrometry has become the gold standard for the rapid identification of most human pathogens. However, F. tularensis identification using such technology and commercially available databases is currently considered unreliable. Real-time PCR-based methods for rapid detection and accurate identification of F. tularensis are not available in many laboratories. As a national reference center for tularemia, we developed a MALDI TOF database allowing accurate identification of the species F. tularensis and its differentiation from the closely related neighbor species F. tularensis subsp. novicida and F. philomiragia. The sensitivity and specificity of this database were validated by testing 71 F. tularensis strains and 165 strains from 63 species not belonging to the Francisella genus. We obtained accurate identification at the species level and differentiation of all the tested bacterial strains. In particular, F. tularensis could be accurately differentiated from other small Gram-negative bacilli occasionally isolated from human samples, including species of the HACEK group and Brucella melitensis.

Seroepidemiology, Spatial Distribution, and Risk Factors of Francisella tularensis in Jordan

There is a paucity of data on Francisella tularensis in the Middle East and North Africa. This is the first countrywide study to determine the seroprevalence, spatial distribution, and risk factors for F. tularensis in Jordan. A total of 828 Jordanians were serologically tested for F. tularensis by ELISA. These individuals filled out a self-administered questionnaire to collect demographic and risk factor information. Bivariate and multivariate logistic regressions were performed to determine which variables are associated with seropositivity. The overall seroprevalence of F. tularensis was 7.7% (95% CI: 6.10-9.75). The bivariate analyses showed that age, region of residence, small ruminant ownership, and practicing horticulture were significantly associated with seropositivity, and these variables were controlled for in the multivariate analysis. The multivariate analysis showed an increased odds of seropositivity among individuals living in northern desert, middle, and northern highland areas, compared with individuals living in the drier southern area, as 7.27 (95% CI: 2.49-21.19), 3.79 (95% CI: 1.53-9.39), and 3.52 (95% CI: 1.45-388.55), respectively. Individuals owning a small ruminant had 1.86 (95% CI: 1.02-3.40) greater odds for seropositivity than individuals who do not own a small ruminant. Individuals practicing horticulture had 2.10 (95% CI: 1.20-3.66) greater odds for seropositivity than individuals who do not practice horticulture. This is the first study to address the seroprevalence of F. tularensis in Jordan and the Middle East. Further research is needed to identify clinical cases of tularemia in Jordan and to determine the circulating F. tularensis subspecies.

Surveillance of Francisella tularensis in surface water of Kurdistan province, west of Iran

BACKGROUND

The etiologic agent of tularemia, Francisella tularensis, is transmitted to humans via ingestion of contaminated water or food, arthropods bite, respiratory aerosols, or direct contact with infected animals body fluids or tissues. In the current study, due to the importance of water in transmitting the disease and the report of the disease in different regions of Iran, surface water of Kurdistan province were evaluated for the presence of F.tularensis.

MATERIALS AND METHODS

Sampling was carried out in five-counties of Kurdistan province. Sixty-six specimens of surface water were collected. The detection was carried out by targeting ISFtu2 and fopA genes using TaqMan real-time PCR. Moreover, the samples were both cultured and inoculated into NMRI inbreed mice. Spleens of inoculated mice and bacterial isolates were tested by TaqMan real-time PCR.

RESULTS

Despite the lack of isolation of F. tularensis, the results of the molecular testing indicate the presence of bacteria in surface water. Molecular positivity of one sample (1.51%) was confirmed using a real-time PCR for both ISFtu2 and fopA genes. Moreover, 4.54% of the samples were positive for ISFtu2.

CONCLUSION

Since the in vitro isolation of bacteria from environmental samples is associated with a very low success rate and depends on various environmental parameters, the use of molecular techniques for monitoring of the bacteria in the contaminated areas is fully recommended.

Clinical characteristics in a sentinel case as well as in a cluster of tularemia patients associated with grape harvest

BACKGROUND

Tularemia is caused by Francisella tularensis and can occasionally establish foodborne transmission.

METHODS

Patients were identified by active case detection through contact with the treating physicians and consent for publication was obtained. Clinical data were accumulated through a review of the patient charts. Serology, culture, and PCR methods were performed for confirmation of the diagnosis.

CASE CLUSTER

A 46-year-old patient was hospitalised in the University Hospital Frankfurt (a tertiary care hospital) for pharyngitis and cervical lymphadenitis with abscess. A diagnosis of tularemia was made serologically, but treatment with ciprofloxacin initially failed. F. tularensis was detected in pus from the lymph node using a specific real-time PCR. The use of RD1 PCR led to the identification of the subspecies holarctica. Antibiotic therapy with high-dose ciprofloxacin and gentamicin was administered and was subsequently changed to ciprofloxacin and rifampicin. During a must-tasting, five other individuals became infected with tularemia by ingestion of contaminated must. All patients required treatment durations of more than 14 days.

CONCLUSIONS

Mechanically harvested agricultural products, such as wine must, can be a source of infection, probably due to contamination with animal carcasses. The clinical course of tularemia can be complicated and prolonged and requires differentiated antibiotic treatment.

Tularemia as a waterborne disease: a review

Francisella tularensis is a Gram-negative, intracellular bacterium causing the zoonosis tularemia. This highly infectious microorganism is considered a potential biological threat agent. Humans are usually infected through direct contact with the animal reservoir and tick bites. However, tularemia cases also occur after contact with a contaminated hydro-telluric environment. Water-borne tularemia outbreaks and sporadic cases have occurred worldwide in the last decades, with specific clinical and epidemiological traits. These infections represent a major public health and military challenge. Human contaminations have occurred through consumption or use of F. tularensis-contaminated water, and various aquatic activities such as swimming, canyoning and fishing. In addition, in Sweden and Finland, mosquitoes are primary vectors of tularemia due to infection of mosquito larvae in contaminated aquatic environments. The mechanisms of F. tularensis survival in water may include the formation of biofilms, interactions with free-living amoebae, and the transition to a 'viable but nonculturable' state, but the relative contribution of these possible mechanisms remains unknown. Many new aquatic species of Francisella have been characterized in recent years. F. tularensis likely shares with these species an ability of long-term survival in the aquatic environment, which has to be considered in terms of tularemia surveillance and control.

A Single Mechanosensitive Channel Protects Francisella tularensis subsp. holarctica from Hypoosmotic Shock and Promotes Survival in the Aquatic Environment

Francisella tularensis subsp. holarctica is found in North America and much of Europe and causes the disease tularemia in humans and animals. An aquatic cycle has been described for this subspecies, which has caused waterborne outbreaks of tularemia in at least 10 countries. In this study, we sought to identify the mechanosensitive channel(s) required for the bacterium to survive the transition from mammalian hosts to freshwater, which is likely essential for the transmission of the bacterium between susceptible hosts. A single 165-amino-acid MscS-type mechanosensitive channel (FtMscS) was found to protect F. tularensis subsp. holarctica from hypoosmotic shock, despite lacking much of the cytoplasmic vestibule domain found in well-characterized MscS proteins from other organisms. The deletion of this channel did not affect virulence within the mammalian host; however, FtMscS was required to survive the transition from the host niche to freshwater. The deletion of FtMscS did not alter the sensitivity of F. tularensis subsp. holarctica to detergents, H₂O₂, or antibiotics, suggesting that the role of FtMscS is specific to protection from hypoosmotic shock. The deletion of FtMscS also led to a reduced average cell size without altering gross cell morphology. The mechanosensitive channel identified and characterized in this study likely contributes to the transmission of tularemia between hosts by allowing the bacterium to survive the transition from mammalian hosts to freshwater.IMPORTANCE The contamination of freshwater by Francisella tularensis subsp. holarctica has resulted in a number of outbreaks of tularemia. Invariably, the contamination originates from the carcasses or excreta of infected animals and thus involves an abrupt osmotic downshock as the bacteria enter freshwater. How F. tularensis survives this drastic change in osmolarity has not been clear, but here we report that a single mechanosensitive channel protects the bacterium from osmotic downshock. This channel is functional despite lacking much of the cytoplasmic vestibule domain that is present in better-studied organisms such as Escherichia coli; this report builds on previous studies that have suggested that parts of this domain are dispensable for downshock protection. These findings extend our understanding of the aquatic cycle and ecological persistence of F. tularensis, with further implications for mechanosensitive channel biology.