2.Bacterial endocarditis 2. Bacterial endocarditis

Incidence

Most commonly affects older, male, large breed dogs, and German shepherd dogs may be predisposed to develop the condition. It is rare in the cat.



Gross pathology

Large cauliflower-like vegetative masses develop attached to the endothelium of the valve leaflets. The mitral valve is most commonly affected, followed by the aortic valve. The tricuspid valve is only occasionally involved.

When bacterial endocarditis does occur in the cat is usually affects the mitral valve.



Histopathology

The lesions consist of bacteria, with inflammatory cells (mononuclear cells and neutrophils) and platelets in an amorphous mass of fibrin and necrotic tissues.



Aetiopathogenesis

Usually secondary to a bacteraemia. Bacteria most frequently cultured from the lesions are coagulase positive staphylococci (particularly Staoureus), Escherichia coli and 13-haemolytic streptococci. Periodontal infection is very common in older dogs and cats, and may act as a primary site for the development of a bacteraemia.

Emboli from the heart valves may travel to any organ, e.g. the kidney, spleen and myocardium, causing abscesses or infarction.



Pathophysiology

The lesions cause valvular regurgitation or incompetence, leading to leftheart failure.



Clinical findings

The most common clinical findings in decreasing order of occurrence are:
(1) fever
(2) tachycardia
(3) vomiting
(4) lameness
(5) cardiac murmur
(6) ventricular arrhythmia
(7) renal failure
(8) heart failure
(9) sudden death
(10) myopathy.


Laboratory findings
(1) positive blood culture - not always detected
(2) leukocytosis with left shift
(3) monocytosis
(4) low serum albumin
(5) increased serum alkaline phosphatase (occasional finding)
(6) hypoglycaemia (occasional finding)
(7) normocytic normochromic anaemia
(8) increased erythrocyte sedimentation rate.


Diagnosis

Is based on history and clinical signs, laboratory findings, the presence of a murmur and positive blood culture. Echocardiographic examination is also very helpful.



Treatment

Prolonged high dose bactericidal antibiotics (ideally based on culture and sensitivity results) which penetrate fibrin. Several antibiotics are usually given alternatively over a 6-8-week period.



S. aureus are usually:
&Nbsp; Sensitive to Resistant to
&Nbsp; Cephalosporins Penicillin
&Nbsp; Aminoglycosides Ampicillin
&Nbsp; Erythromycin Trimethoprim
&Nbsp; Chioramphenicol


E. Coli are usually:
&Nbsp; Sensitive to Resistant to
&Nbsp; Gentamicin Ampicillin
&Nbsp; Cephalosporins Chloramphenicol


b-Haemolytic streptococci are usually:
&Nbsp; Sensitive to Resistant to
&Nbsp; Penicillin Erythromycin
&Nbsp; Ampicillin Aminoglycosides
&Nbsp; Cephalosporins Trimethoprim
&Nbsp; Chloramphenicol


Higher than normal dose rates of antibiotics are recommended in bacterial endocarditis, and the intravenous route is preferred initially.

It is important to treat concomitant problems, and care needs to be taken in geriatric patients when using drugs such as the aminoglycosides which may be nephrotoxic.