Antimicrobial Agents and Chemotherapy. 2014 Sep;58(9):5510-8. doi: 10.1128/AAC.03443-14. Epub 2014 Jul 7.

Efficacy of liposome-encapsulated ciprofloxacin in a murine model of Q fever.

 

IH. Norville,a G. J. Hatch,b K. R. Bewley,b D. J. Atkinson,a K. A. Hamblin,a J. D. Blanchard,d S. J. Armstrong,a J. K. Pitman,b E. Rayner,b G. Hall,b J. Vipond,b T. P. Atkinsa,c

a Defence Science and Technology Laboratory, Porton Down, Salisbury, United Kingdom;

b Public Health England, Porton Down, Salisbury, United Kingdom;

c College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom;

d Aradigm Corporation, Hayward, California, USA

 

Abstract

Encapsulation of antibiotics may improve treatment of intracellular infections by prolonging antibiotic release and improving antibiotic uptake into cells. In this study, liposome-encapsulated ciprofloxacin for inhalation (CFI) was evaluated as a post exposure therapeutic for the treatment of Coxiella burnetii, the causative agent of Q fever. Intranasal treatment of male A/Jola (A/J) mice with CFI (50 mg/kg of body weight) once daily for 7 days protected mice against weight loss and clinical signs following an aerosol challenge with C. burnetii. In comparison, mice treated twice daily with oral ciprofloxacin or doxycycline (50 mg/kg) or phosphate-buffered saline (PBS) lost 15 to 20% body weight and exhibited ruffled fur, arched backs, and dehydration. Mice were culled at day 14 post challenge. The weights and bacterial burdens of organs were determined. Mice treated with CFI exhibited reduced splenomegaly and reduced bacterial numbers in the lungs and spleen compared to mice treated with oral ciprofloxacin or doxycycline. When a single dose of CFI was administered, it provided better protection against body weight loss than 7 days of treatment with oral doxycycline, the current antibiotic of choice to treat Q fever. These data suggest that CFI has potential as a superior antibiotic to treat Q fever.

PMID: 25001305

 

Supplement

Q fever is a bacterial disease which can be spread to humans from contact with infected goats, cattle and sheep (McQuiston and Childs, 2002). Infection can occur by inhaling very small numbers (less than10) of the bacterium Coxiella burnetii. Q fever infections are globally widespread and there was recently a large outbreak in the Netherlands which resulted in over 4000 humans cases and over 50 000 goats were culled to try to stop the spread of the disease (Whelan et al., 2011; Dijikstra et al., 2012). The symptoms of Q fever can present as a severe flu-like illness which resolves in two weeks, however some individuals have debilitating long term health problems, such as infected heart valves and chronic fatigue syndrome (Maurin and Raoult, 1999). This disease is usually successfully treated with the antibiotic doxycycline, but in some cases the treatment time lasts over 18 months. In addition, there are problems with increasing levels of antibiotic resistance which can make current antibiotic treatments ineffective (Rouli et al., 2012).

 

Fig 1

Figure 1. Delivery of encapsulated antibiotic (CFI) into the lung following inhalational infection with C. burnetii.

 

Inhaled, encapsulated antibiotics have several advantages over traditional oral antibiotics (Cipolla et al., 2013). Delivery of an encapsulated antibiotic directly into the lung can result in higher levels of drug lasting for longer at the site of infection, which may act to reduce the numbers of bacteria and reduce the infection (Figure 1). The inhaled formulation of antibiotic we studied in this paper (Ciprofloxacin for Inhalation; CFI) was encapsulated in a liposome (a tiny water droplet containing the drug surrounded by a lipid membrane made out of materials similar to those naturally occurring in human lungs). The presence of the liposome improves the antibiotic killing effect by improving uptake of the antibiotic into infected immune cells. In addition, CFI has been shown to successfully treat other lung infections, such as Tularaemia and Plague and has completed several human clinical studies for the treatment of chronic lung disease caused by the bacterium Pseudomonas aeruginosa (Bruinenberg et al., 2010; Hamblin et al., 2014; Serisier et al., 2013) Therefore, we hypothesized that delivery of CFI into the lung of a mouse infected with C. burnetii might improve disease outcome.

First, we developed a mouse model of Q fever to enable us to monitor and treat disease within a laboratory setting. We infected mice with an aerosol of bacteria causing Q-fever and observed the mice for 14 days. The mice lost weight and showed signs of disease such as ruffled fur and a hunched posture which peaked at day 8 after infection and then got better by day 14 (Figure 2). The infected mice also had enlarged lungs and spleens which became heavily infected as the disease progressed (Figure 3). These observations indicate that there are several similarities between the disease occurring in experimentally infected mice and naturally acquired human Q fever.

 

Fig 2

Figure 2. The mean percentage change in body weight of mice infected by the aerosol route with C. burnetii or PBS (uninfected control). Infected mice lose 15-20% bodyweight.

 

We then wanted to determine whether encapsulation of antibiotic improves treatment of Q fever using our mouse model. The antibiotic ciprofloxacin is not usually used to treat Q fever in humans as it does not work well. We confirmed this in our studies, as mice treated with oral ciprofloxacin all looked ill and lost nearly the same amount of body weight (17%) as mice who did not received any antibiotic (18%). However, mice that received an intranasal dose of encapsulated ciprofloxacin (CFI) did not have any significant weight loss and did not appear to be ill. In addition, CFI was present in the lung at a higher concentration and for longer than oral ciprofloxacin.

Finally, we wanted to see if CFI is better than the current antibiotic of choice to treat Q fever, doxycycline. As expected, whilst being treated with oral doxycycline, the mice did not get ill. However, when doxycycline treatment was stopped, the mice became ill and lost as much weight as those who had not received any antibiotic (Figure 4). Mice treated with intranasal CFI for 7 days were protected from severe disease, with minimal weight loss, no signs of disease and reduced numbers of bacteria in the lung and spleen.

 

Key findings from this work:

  • We have developed a well-characterised mouse model of inhaled Q fever infection, enabling us to test new antibiotics
  • Encapsulation of ciprofloxacin (CFI) enables effective delivery of the antibiotic into the lung and improves disease outcome compared to oral ciprofloxacin;
  • Treatment with CFI is better at preventing severe Q fever than the current antibiotic of choice, doxycycline.

 

Fig 3

Figure 3. The number of C. burnetii found in mouse tissues following an aerosol infection.

 

 

Fig 4

Figure 4. Mean percentage weight loss in mice infected with C. burnetii and then treated for 7 days with doxycycline or CFI. Mice treated with doxycycline lose weight after the antibiotic treatment stops. Mice treated with CFI have significantly reduced weight loss from day 8 after infection (p<0.001).

 

References

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