Experimental pleural empyema model in rabbits: Why, how and what are the next steps
Authors: Cvijanovic Vlado , Vojvodic Danilo , Djurdjevic Dragan , Jovic Milena , Stanic Vojkan , Sekulovic Leposava , Peric Tijana 
Published: May 2014

Bacgraund/Aim. The use of new therapeutic methods to prevent development of
fibrothorax as the final complication of the human pleural infections
requires research with experimental animals. The aim of this study was to
standardize the procedures for the establishment of our own experimental
model of empyema in rabbits, since it should be able to offer similar
conditions found in human pleural infections. Methods. This experiment
included 15 chinchilla rabbits, weighing from 2.3 to 2.8 kg. There were 12
rabbits in the experimental group, while 3 rabbits formed the control group.
On the first day, we administered 0.4-0.5 mL of turpentine in the right
pleural space of the rabbits from the experimental group in order to provoke
sterile exudative pleurisy. After 24 h we injected 1 mL of Staphylococcus
aureus and 1 mL of Escherichia coli bacteria in the same concentration of 4.5
x 108 bacteria/mL. Thoracocentesis for the pleural fluid analysis was
performed 24, 48, 72, and 96 h after bacteria instillation. In these pleural
samples we estimated the number of leucocytes and the values of lactate
dehydrogenase (LDH), glucose and pH in pleural fluid, as well as the presence
of bacteria. We did not protect the animals with antibiotics, and on the day
7 of the experiment they were sacrificed with the lethal dose of barbiturate
(iv). The lung from the empyemic side of all experimental animals and the
lung of one control animal were histopathologically examined. Results. A
total of 4 animals had a small amount of clear pleural fluids or there was no
fluid obtained with thoracocentesis 24 and 48 h after the bacteria
instillation. after the bacteria instillation. In the remaining 8 rabbits 24
h after bacteria administration the mean values (? SD) of the parameters
monitored were as follows: Le 34.75 ? 6.13 x 109/L, LDH 17,000 ? 4,69 U/L,
glucose 1.23 ? 0.45 mmol/L, and pH 6.975 ? 0.15. The obtained values met the
criteria for the evaluation of effusion as pleural empyema or complex and
complicated pleural effusion (LDH > 1000 U/L, glucose < 2.31 mmol/L and pH <
7.20). Bacterial cultures were positive in 5 out of 8 first pleural samples
and in only 2 samples after 48 h of bacteria administration. There was a
positive correlation between the number of leukocytes and the LDH value (r =
0.071, p < 0.001), and a negative correlation between the number of
leukocytes and the glucose level (r = 0.864, p < 0.001), and the leukocytes
number and pH of the pleural fluid (r = 0.894, p < 0.001). The mean glucose
value increased after 48 h (3.23 ? 0.44 mmol/L), and the pH value rose after
72 h (7.22 ? 0.03) which was beyond the empyema level. Conclusion. The
creation of the experimental empyema model is a very delicate work with
uncertain success. Its value and importance are crucial for pleural pathology
research. With the intention to obtain a more empyemic pleural reaction we
created a model with two different human pathogen bacteria. We generated the
satisfactory results, but not as good as those contained in some of the
reference literature data.