Basrah Journal of Veterinary Research,Vol.17, No.3,2018
Proceeding of 6th International Scientific Conference,College of Veterinary Medicine
University of Basrah,Iraq
1
STUDY THE PATHOLOGIC EFFECT OF Staphylococcus aureus
POST INFECTION IN RABBITS
ZainabJamal M.Jawad , Zainab Ismail Ibrahim, Aseel Ismail Ibrahim
* Department Pathology and Poultry Disease , College of Veterinary Medicine,
University of Baghdad,Baghdad,Iraq
**Department Clinical Laboratory Sciences,College of Pharmacy, University of
Baghdad , Baghdad,Iraq
Keywords: Staphylococcus aureus, infections in rabbits, histopathology.
Corresponding Author: zainab0jamal@yahoo.com
ABSTRACT
Staphylococcus aureus (S.aureus) is a versatile opportunistic pathogen that causes a
wide spectrum of pathologies. In rabbits, this bacterium infects dermal lesions causing
suppurative dermatitis, and invades subcutaneous tissues, causing different wellknown
disease conditions such as mastitis, abscesses (subcutaneously or affecting
internal organs) and pododermatitis. The aim of the study is to update the knowledge
on rabbit Staphylococcosis by focusing mainly on the different histopathologic
changes. Twenty rabbits were used as laboratory animal models in an experiment
designed to study the pathogenesis of S. aureus. A dose of (1x108 CFU/ml) of a
Rifampicin-resistant S.aureus was given through the following routes: Intratracheal
(IT), andsterile distilled water was given by same route to a group of rabbits used as
control.There were difference in temperature and body weights among treated animals
and control,but it were statistically significant(P˂0.05).
Basrah Journal of Veterinary Research,Vol.17, No.3,2018
Proceeding of 6th International Scientific Conference,College of Veterinary Medicine
University of Basrah,Iraq
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INTRODUCTION
Staphylococcus aureus is a pathogen capable of infecting humans and a wide variety of
animals. This bacterium affects rabbits of different ages, infects dermal lesions and invades
subcutaneous tissues (1), resulting in different pathologies including suppurative dermatitis,
mastitis, multisystemicabscessation and pododermatitis (2). The ability of S. aureus to
cause disease is due to a combination of virulence factors. Bacteria are considered major
risk factors for diseases of respiratory system (3), skin (4), the eye (5) and other septicemia
in rabbits (4, 6) as seen in this study. Bacterial infection following ulceration of paws and
urine burns (7,4) was the likely cause to Sore hocks/chronic ulcerative pododermatitis and
arthritis and osteomyelitis encountered in this study.
International dissemination of high virulent S. aureus clone in rabbits has been reported (8).
Clinical diseases caused by S. aureusinfections in rabbits are dermal lesions,
pododermatitis, abscesses and mastitis; consequently lead to poor production and mortality
in young and infertility of the breeders (9 ,10). As a result of agalactia in the doe caused by
S. aureus, suckling rabbits acquire infection during lactation that lead to high mortality
rates in offspring. Natural infection of the mammary gland of rabbits with S. aureus can
cause acute gangrenous or chronic purulent mastitis (11,9). In the acute gangrenous form,
which is rapidly fatal, the mammary tissue becomes oedematous, haemorrhagic and
necrotic.Rabbit Staphylococcosis: Difficult solutions for serious problems
Staphylococcus aureus infections are a major problem in rabbits. The main manifestations
are subcutaneous abscesses, mastitis, pododermatitis and septicaemia. Two patterns of
infection can be distinguished. In the first type, clinical signs remain limited to a small
number of rabbits in a flock. This type has little economic importance and is caused by
low-virulence S. aureus strains. In the second type, the disease shows an epidemic spread.
Consequences are poor production results, infertility and death. This leads to chronic
problems and a subsequent decline in production. The latter type is caused by highvirulence
strains. Biotyping, phage typing and RAPD typing contribute to the
characterization of high-virulence S. aureus strains. Administration of antibiotics,
disinfection of the environment and vaccination are not able to solve the problems.
Therefore, the only effective measure is to cull the entire flock and to restart with a new
rabbit population after thorough disinfection. Limiting the introduction of new rabbits in
existingrabbitsand reducing contacts between rabbits to an absolute minimum are currently
the only way to face this most difficult problem,(12) showed that staphylococci based
mastitis was one of the main factors of culling of adult rabbits.
MATERIALS AND METHODS
Basrah Journal of Veterinary Research,Vol.17, No.3,2018
Proceeding of 6th International Scientific Conference,College of Veterinary Medicine
University of Basrah,Iraq
178
At this study (15) male and female rabbits with body weight ranged between (2090-
1080gm.) were used. The animals were raised and bred in the animal house of College of
veterinary medicine/ University of Baghdad where the research was done. The animals
were kept in cages of (20*30*50) cm³ dimensions in average of three rats in each cage one
month before study for acclimatization in optimum conditions of breeding at (22±3) ºC
with a (14/10) hours (Light/Dark) cycle.Commercial feed pellets and drinking water were
given all the time of experiment(13).
Inoculum:
S. aureusstrain used in this research isolated from mastitis case diagnosis at medicine
department/ College of veterinary medicine/ University of Baghdad.The dose prepared as
(14).
Experimental design:
Fifteen rabbits (white newzeland), were used as laboratory animal models in an experiment
designed to study the pathogenesis of S. aureus and divided randomly into infected
group(n=12) with a dose of 1x108 CFU/ml of a Rifampicin-resistant S.aureusIntratrachial
(I/T), and controlgroup ( n=3)with sterile distilled water was given by same route.
The animals sacrificed at the end of experiment post infection (1, 3,7,14days), after postmortem
examination the tissue specimens were preserved in formalin 10% to prepare
hematoxylene-eosin tissue slides (15).
RESULTS
1- Clinical signs:
The clinical signs appeared in rabbits injected via (I/T) were characterized by chock &
cough for a while after injection, difficulty in breathing and then death of two animals from
(I/T) group after one day of injection.
A significant decrease (P ˃ 0.05) in body weight in infected group I/T along the
experimental periods comparing with control group,also the body temperature showed
significant increase (P ˃ 0.05) ininfected group along the experimental periods comparing
with control group (Figure-1).
Basrah Journal of Veterinary Research,Vol.17, No.3,2018
Proceeding of 6th International Scientific Conference,College of Veterinary Medicine
University of Basrah,Iraq
179
Figure- 1: illustrated temperature changes at(I/T) group,while the normal body
temperature was 37.7 °C.
2- Isolation of bacteria and Grossappearance:
Isolation of bacteria from lung and liver after 1day post infection was positive while at (3,
7,14days)after infection the isolation of bacteria was positive for lung,liver,brain,blood,and
kidneys.
Gross lesion were characterized by hemorrhageand presence of blood on the lumen of
trachea,hydropercardium,paleness due to emphysema of some lobes of lung , pulmonary
consolidation and liver congestion with pale area (1-3) mm in diameter on its surface.There
were congestion of most visceral organs of treated rabbits and congestion of brain(Figure -
2).
3-Histopathologic examination:
Histopathological changes were characterized by suppurativetrachietis in(I/T) groupas
sloughing of lining epithelia of trachea with focal area of (PMNS) cells infiltration
especially neutrophils instead of normal tissue(Figure-3).Abscesses formed consisted of
dead andlive tissue cells.This lesion was diagnosed as suppurativetrachietis with congestion
of blood vessels.In pulmonary tissue the lesion mainly PMNs infiltration, congestion of
alveolar capillaries caused thickening of alveolar walls (Figure-4).
37.5
37.6
37.7
37.8
37.9
38
38.1
38.2
38.3
38.4
0 2 4 6 8 10 12 14 16
Basrah Journal of Veterinary Research,Vol.17, No.3,2018
Proceeding of 6th International Scientific Conference,College of Veterinary Medicine
University of Basrah,Iraq
The liver in all infected
vacuolar degeneration of hepatocytes;
accumulation especially neutrophils
Hemorrhage, congestion of blood
neuroglial cells and degeneration
(chromatolysis),with thickness of pia mater layer due to infiltration of (PMNS) cells and
lymphocytes(Figure -6).
Cloudy swelling of lining epithelia of the
necrotic tubules, dilation
especially neutrophils and
Heart,showed intramuscular
infiltration of inflammatory cells especially neutrophils some muscle fibers lo
to inflammation became enlarged, swollen
Marked Rifampicin–resistant
animals was recovered and identified
included:blood, heart, lung, liver, kidney and brain.
Figure- 2: rabbit brain of (I/T
the brain.
180
animals were characterized by hemorrhage, congestion
different in severity with focal areas of (PMNS
neutrophils(Figure-5)
, vessels in all layers of the brain were seen with edema of
or loss of nuclei of some Purkinje cells
,renal tubules appeared in star
of bowman's space with mild infiltration of inflammatory cell
its severity continuousalong the experimental
fibers odemaand congestion of blood vessels with mild
swollen.
Staphylococcus aureus strain used in all the inoculated
permanently from the samples
:T- 3 days); congestion blood vessels and enlargement of
and
PMNS)
star- shaped with some
cells
along periods.
and loss its disc due
train taken which
Basrah Journal of Veterinary Research,Vol.17, No.3,2018
Proceeding of 6th International Scientific Conference,College of Veterinary Medicine
University of Basrah,Iraq
181
Figure- 3:Histopathological section of rabbit treachea (I/T-14days);
showedsuppurativetrachietis, PMNs infiltration and necrotic epithelial debris, (H&E, stain
10X)
Figure-4:Histopathological section of rabbit lung (I/T-1day); characterized by thickening
of alveolar wall, infiltration of neutrophils cells, congestion of blood vessels with
emphysema (H&E, stain 4X).
Basrah Journal of Veterinary Research,Vol.17, No.3,2018
Proceeding of 6th International Scientific Conference,College of Veterinary Medicine
University of Basrah,Iraq
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Figure- 5:Histopathological section of rabbit liver (I/T-14days);suppurativehepatitis,
infiltration of (PMNs) cells, mainly neutrophils in the liver parenchyma (H&Estain, 20X).
Figure-6:Histopathological section of rabbit cerebellum(I/T-1day); characterized by
chromatolysis of perkunji cells,(H&Estain,10X).
Basrah Journal of Veterinary Research,Vol.17, No.3,2018
Proceeding of 6th International Scientific Conference,College of Veterinary Medicine
University of Basrah,Iraq
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DISCUSSION
The body weight along the period of the study which showed a significant decrease
(P<0.05)was due to systemic reaction against the bacterial infection and it toxins on enteral
organs which confirmed by positive isolation of bacteria and the effect of bacterial toxin on
the digestive system which effect the absorption of food from intestine(16).While the body
temperature showed significant increasecomparing with control group due to the
Neutrophiles ability to produce endogenous pyrogenes which it is responsible to increase
the body temperature or due to the effect of bacteria(causing lesions) on hypothalamus it is
the part of brain responsible to regulate body temperature lead to increase the body
temperature (17).the clinical sings that experiment animals show (chock & cough for a
while after injection, difficulty in breathing) it is consider as normal reaction to the irritant
injected material .on the other hand, the death of animals occur due to the lethal toxin effect
of Staphylococcus aureuswhich it kill with in (2-24 h) (18).However, the congestion of
some organs was due to bacterial toxins harmful effects on endothelial blood vessels while
lead to cause disturbance in the permeability of these blood vessels(19,20).
The typical inflammation response to bacterial infection of Staphylococcus
aureuswascharacterized byaccumulation of inflammatory cells at different part of the organ
mainly (neutrophils, macrophage and lymphocytes) which lead to abcessation or
suppurative inflammationat different organs such as trachea, heart, lung, liver, kidney
andbrain(21,22) with degeneration changes(19).
TheStaphylococcus aureusbacteria were isolated along the hall period of experiment from
blood, as trachea, heart, lung, liver, kidney and brain,may due to the distribution of bacteria
via the blood stream (bacteremia)(23, 17).
CONCLUSIONS:
This study proved that the rabbit is a good laboratory animal for specific Staphylococcus
aureus tests, the clinical signs and histopathological changes (grossly and microscopically)
were variable in different internal organs. The bacteria label technic was suitable way to
study the same bacteria without mixing with others from same type.
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