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McMaster University
Health Sciences
Kirsten Culver

CARDIOVASCULAR INFECTIONS MODULE The cardiovascular system consists of the heart, blood vesseis and blood. As blood circulates throughiut the body, it comes into contact with many tissues and organs. As such, the bloodstream serves as an excellent vehicle for the spread of pathogenoic orangisms – facilitating the infection of multiple organ system Bloodstream infections manifest clinical into many forms. For example persistent bactermia ( presence of bacter in the blood) is suggestive of intravasculsr infection such as endocarditis or catheter related infections. These tpyes of infecrion such are life threatening and the appropriate diagnosis and management of such infection are critical to patient survivial INTRODUCTION In lecture, you learned that CV infection can manifest in the heart, vavles, mypcatdium and pericardium. Moreover, you learned that each site of infection possess characteristic signs and symptoms that when identified help facilitate diagnosi. In this laboratory module , you will explore some of the specimen collection methos and laboratory diagnostic techniques used to indentify acute bacterial endocarditis; serious CV infection. PATENT SCENARIO Anne is a 33 year old women who presents to the ER with fever, SOB, and chest pain. In ER, Anne vitals signs are as follows: • BP – 100/70 • HR – 110 • Tempertaure – 39 • RR – 33 • O2 – 90% on RA The ER nurse who finds infection marks on both arms examines Anne. Anna tell the nurse that she has been abusing heroin for the past 3 years and that she last injected drugs 3 day ago. Examination of Anne’s chest reveals a dullness to percussion in the left lung base and crackles and wheezes in the same area. A loud hear murmur is also heard. Anne tells the ER physician that this is the frist time she ver been told about having a heart murmur ( result of turbulent blood flow- narrowing and leaking ) Based on the physical exam, a chest x-ray and 2 sets of bloods cultures are ordered Annes chest xrays reveal several small area of infilrates in the lower lobes of her left lung Within 4 hours of delivering the blood sample to medical mirco lab, lab techiams calls to report that both sets of blood cultures are positive for staphylococcus aureus STAPHYYLOCOCCUS AURENUS Staphyslococcus anreus is gram positive bacterium that appears microscopically a grape- like clusters. Staphylococci are ubiquitous, and can survive extreme condition of drying, heat, low oxygen and high salt environments S anreus has many surface protein that allow the organism to bind to tissues and foreigin bodies coated with fibronectin, fibrinogen, and collagen, thereby allowing the bacterium to adhere to sutures, catheter, prostetic vavle and other devices such as dirty needles . S aureus colonizes the skin and mucous membrane of 30% - 50% of healthy adult and children. Rates of carriage on the hands and other skin area of more than 50% of these individual occurs in children with burns, and in people with frequent needle use ( e.g. diabetes mellitus, hemodialysis, recreational durg use, allergy shots) As such, these individuals ( including drug users such as anne) are at an increased risk of vascular –access bacteremia. QUESTION At this point in the patient scenario, we have learned the following infro: • Anne has a fever • Is experiencing chest pain and increased HR • Has a low BO • Experiencing SOB and increased RR • Chest xrays reveal lower lobe infiltrates in the left lung • A new heart murmur • Blood culture are postibe for S. anreus • Intervenous drug user Based on this info what diagnosis do you suspect? • Actue bacterial Endocarditis • Community Acquired Pneumonia • Celluitis ANSWER: ACUTE BACTERIAL, ENDOCARDITIS Correct. IV drug use are at increased risk of vascular access bacteremia, which can then leas to endocarditis. Annes new and loud heat murmur is consistent with heart valve damage. Right sided endocarditis most often occurs when an aggressive species of skin bacteria, Such as S. anreus, enters the bloodstream and attacks a normal undamaged heart vavle. When S.anreus bacteria begin to multiply inside the heart, small clumps of bacteria called septic emboli may move into the bloodstream – spreading the infection to other organ especially the kidney, lungs and brain. It is likely that the pneumonia seen in Annes chest xray is a result of bacteria from her heart moving into, and this
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