Causative agents of cardiovascular infections

thumb | 350px| Infekční endokarditida. Původce: Haemophilus parainfluenzae. Heart infections include infectious endocarditis, myocarditis and pericarditis. Vascular infections include the focal infections of great blood vessels, infections regarding endothelium of small vessels and infections due to catethetrisation.

Heart infections

Infectious endocarditis

• Severe illness, infected trombus is attatched to the heart valve or mural endocardium, with risk of embolisation.
• Nosocomial infections – in developed countries 5–29 % of the cases (the risk of invasive procedures).
• Intact endotelium is resistant to all pathogens except for S. aureus.

The etiological agent

Staphylococcus aureus

• Affects both altered and healthy valves, as well as valve replacements;
• at risk of embolisation to distant organs;
• isolated in 20% of the cases.

Coagulase-negative staphylococci (St. epidermidis, St. haemolyticus, St. hominis)

• Commensals of the skin with great affinity for artificial surfaces;
• most frequent causes of endocarditis regarding artificial valve , pacemaker, sepsis after catheterisation;
• usually without embolisation;
• less sensitive to ATB.

Streptococci

• Viridans and hemolytic streptococci;
• S. pneumoniae – etiological agent in 60 % of the cases;
• Trapping in anaerobic hemoculture bottles, cultivation on enriched medium;
• they disrupt valves that were damaged prior to that;
• S.mitis, S.sanguis, S.mutans, S.bovis.

Enterococci

• Enter the bloodstream after uroinfections or infections of biliary tract;
• ATB resistence as a main complication.

Gram-negative bacteria

• E.coli, salmonella, klebsiella.

Pseudomonas

• Nosocomial endocarditis, commonly occurs in polymorbid patients;
• high lethality (up to 80 %);
• treated with an urgent surgical procedure.

Candida, Aspergillus

• Infectious agent in immunodeficient or immunosupressed patients;
• large vegetations (several cm) → risk of valve obturation, massive embolism;
• difficult to identify from hemoculture.

Diagnostics

• Echocardiography, hemoculture (at least two samples must be obtained).

Therapy

• ATB based on infectious agent, usually high dosage;
• hospitalisation is mandatory, surgical procedure in some cases.

Myocarditis

thumb| 300px| Virová myokarditida.

• Inflammation of myocardium.

Etiology

• Most common are viral infections;
• virus Coxsackie B, adenovirus, enterovirus, borrelia, leptospira, treponema, diphteria toxin;
• fungal myocarditis;
• parasitic myocarditis – rare in CzR , higher occurence in tropical areas, lately a complication of toxoplasmosis in AIDS positive patients.

Diagnostics

• Echocardiography, CRP, histological analysis of punctured tissue;
• for now, there is no reliable test for in vitro diagnosis.

Therapy

• Anti-infectives according to the infectious agent.

Pericarditis

• Serous pericarditis – of viral origin, spirochetes;
• purulent pericarditis – as a complication of bacterial sepsis, S.aureus, gram-positive bacteria;
• giant cell pericarditis due to tuberculosis.

Diagnostics

• EKG, CT, etiological agents are identified by examination of punctured liquid sample.

Therapy according to etiology.

Clinical samples in cardiac infections

• Hemocultures: hemoculture bottles with broth, when signs of growth are present, the sample is examined under the microscope and by cultivation test;
• Cultivation: blood agar with staphylococcal line, cultivation in 5 % CO₂ atmosphere, Endo's medium or McConkey agar, anaerobic culture, Sabouraud agar;
• in suspicion of slowly growing bacteria it is crucial to examine the seemingly negative hemoculture under the microscope, chocolate agar inoculation after 3 weeks, incubation in 5 % CO₂ atmosphere for 3 - 4 weeks

Vascular infections

Focal infections of blood vessels

• Infectious aneurysm – streptococci, S. aureus;
• endarteritis – S. aureus;
• infected thrombus in aortic bulge – salmonella;
• purulent thrombophlebitis – streptococci, anaerobic bacteria.

Nosocomial catheter infections

• Dangerous mainly regarding central venous catheter, infection of peripheral venous catheters is more frequent, yet less severe;
• S. epidermidis, coagulase-negativne stafylococci, S. aureus, E. faecalis, E. coli, Candida albicans,...

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Related articles

• Infectious endocarditis
• Myocarditis
• Pericarditis