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Microbiology MBBS > Cardiovascular infections, blood stream infections > Flashcards

Cardiovascular infections, blood stream infections Flashcards

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1
Q

Cardiovascular system infections include

A 
1. Infections of the heart:
 Infective endocarditis 
 Myocarditis 
 Pericarditis
2. Infections of blood vessels
3. Device related infections:
 CBSI catheter based bloodstream infections
 Suppurative thrombophlebitis 
4. Autoimmune mediated
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2
Q

Composition of bulky friable vegetations of infective endocarditis

A
  1. Platelets
  2. Fibrin
  3. Microcolonies of organisms
  4. Scanty inflammatory cells
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3
Q

Common areas where vegetations of infective endocarditis are seen

A
  1. Heart valves (M/C)
  2. Low pressure side of ventricular septal defect
  3. Mural endocardium
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4
Q

Acute endocarditis

A

Rapidly damaged cardiac structures
Extracardiac spread
Highly virulent S. aureus attacking normal valves
Substantial morbidity and mortality even with appropriate antibiotic therapy/surgery

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5
Q

Subacute endocarditis

A 
Usually occurs in previously damaged heat
Less virulent viridans streptococci
Insidious onset, metastasises spelt
Gradually progressive
Recover after antibiotic therapy
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6
Q

Pathogenesis of infective endocarditis

A
  1. Underlying risk factors
  2. Endothelial damage
  3. Colonisation
  4. Formation of vegetations
  5. Metastasis
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7
Q

Portal of entry for organisms causing infective endocarditis

A

Oral cavity: viridans streptococci
Skin: Staphylococci
Upper respiratory tract: HACEK organisms
GIT: Streptococcus gallolyticus and enterococci

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8
Q

Clinical manifestations of infective endocarditis

A
  1. Cardiac manifestations: murmur (new or old)
  2. Non cardiac manifestations
  3. Laboratory manifestations:
    Anaemia, microscopic haematuria
    Leucocytosis
    Elevated ESR, CRP or rheumatoid factor
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9
Q

Non cardiac manifestations of infective endocarditis

A 
Fever, chills and sweats 
Anorexia, weight loss
Myalgia, arthralgia
Arterial embolism, splenomegaly
Osler’s nodes, subungual haemorrhage, Janeway lesions
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10
Q

Major criteria of Duke’s criteria

A
  1. Positive blood cultures:
    • Typical IE organism isolated from two different blood cultures
    • Persistently positive blood culture other than typical IE organisms
    • Single positive blood culture for Coxiella burnetti of phase I IgG titre of > 1:800
  2. Evidence of endocardial involvement:
    • Positive ECG
    • new valvular regurgitation
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11
Q

Minor criteria of Duke’s criteria

A
  1. Predisposition
  2. Fever
  3. Vascular phenomenon
  4. Immunological phenomenon:
    glomerulonephritis, Osler’s nodes, Roth’s spots, Rheumatoid factor
  5. Microbiological evidence: not meeting major criteria
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12
Q

Treatment of infective endocarditis

A
  1. Regimen for S. aureus IE:
    • for native valve IE:
    For MSSA: cloxacillin, nafcillin
    For MRSA: vancomycin
    • for prosthetic valve IE:
    In addition, rifampin and gentamicin
  2. For viridans streptococci and S. gallolyticus:
    Native valve: penicillin, ceftriaxone
    Prosthetic valve: in addition, gentamicin
  3. For HACEK: Ceftriaxone or ciprofloxacin
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13
Q

Staphylococcal endocarditis

A

S. aureus is M/C cause, acute course

Larger vegetations, septic embolism features like Osler’s nodes, sabungual haemorrhage, stroke,(encephalopathy)

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14
Q

Diseases caused by viridans streptococci

A

Commensals of mouth and upper respiratory tract

  1. SABE Subacute bacterial endocarditis
  2. Dental caries
  3. In cancer patients
  4. S. milleri group produces suppurative infections particularly brain abscesses and empyema
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15
Q

Nutritionally variant Streptococci

A

They require vitamin B - pyridoxal
Earlier they were grouped along with viridans streptococci
Normal inhabitants of oral cavity, and can cause infective endocarditis
Penicillin + gentamicin for treatment

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16
Q

S. gallolyticus

A

Formerly S. bovis is a group D streptococcus
Commensal of intestine of animals
Can cause bacteremia, subacute endocarditis and associated with colorectal cancer or polyps
Penicillin is DoC

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17
Q

HACEK group members

A 
Haemophilus parainfluenzae
Aggregatibactor species
Cardiobacterium hominis
Eikenella corrodens - ampicillin DoC
Kingella kingae
For others DoC is Ceftriaxone
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18
Q

HACEK group

A

Highly fastidious, slow growing, capnophilic, gram negative bacteria that normally reside on oral cavity as commensals
Associated with local infections of mouth and endocarditis
DoC is Ceftriaxone except for Eikenella

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19
Q

Myocarditis

A

Manifested by chest pain, arrhythmias or CHF
Rapidly progressive and often fatal
Infectious or non-infectious
Usually by viruses like Coxsackievirus, adenovirus, … or sometime by Trypanosoma cruzi

20
Q

Pericarditis

A

Chest pain, pericardial friction rub and pericardial effusion
Infectious or non-infectious
M/C viruses like Coxsackievirus (adenovirus)
Rarely bacteria like S. aureus, H. influenzae- suppurative pericarditis as a complication of pneumonia
M. tuberculosis as a complication of TB

21
Q

Mycotic aneurysm

A

Refers aneurysms of infectious etiology like syphilitic aneurysms
Streptococci and staphylococci are also causes

22
Q

Infective endoarteritis

A

Inflammation of arterial wall with or without aneurysmal dilation

23
Q

Suppurative thrombophlebitis STP

A

Inflammation of vein wall
Occurs secondary to IV catheter or dermal infection
M/C IV cannulation:
After 3-4 days of IV cannulation which gets colonised by the organism in patients skin or hands of healthcare workers
S. aureus, enterobacteriaceae, yeasts

24
Q

Lamierre’s syndrome

A

Thrombophlebitis of internal jugular vein and bacteremia- caused usually by Fusobacteri necrophorum, following recent oropharyngeal infection

25
Q

Genes predisposing to acute rheumatic fever

A

HLA-DR7

HLA-DR4

26
Q

Modified Jones criteria

Major criteria

A
  1. Carditis: clinical or sub clinical
  2. Arthritis:
    • only polyarthritis for low risk
    • monoarthritis, polyarthritis or polyarthralgia for high risk
  3. Chorea
  4. Erythema marginatum
  5. Subcutaneous nodules
27
Q

Jones criteria

Minor criteria

A 
1. Polyarthralgia for low-risk
 Monoarthralgia for high-risk 
2. Hyperpyrexia:
 >= 38.5°C for low risk
 >= 38°C for high risk
3. CRP>= 3 mg/dL
 ESR >= 60 mm/h for low risk
 ESR >= 30 mm/h for high risk
4. Prolonged PR interval
28
Q

Clinical manifestations of acute rheumatic fever

A
  1. Migratory polyarthritis
  2. Pancarditis
  3. Subcutaneous nodules
  4. Sydenham’s chorea
  5. Erythema marginatum
29
Q

Rheumatic heart disease

treatment

A

Penicillin is the drug of choice
Can be given orally or IM
Supportive treatment should be given for arthritis, arthralgia and fever.

30
Q

Types of bacteremia

A
  1. Transient bacteremia:
    Occurs spontaneously or due to minor events
  2. Continuous bacteremia:
    Fairly constant rate release
    Cardiovascular infections, early stages of certain infections
  3. Intermittent bacteremia:
    Undrained abscess, early coarse of some infections
31
Q

Bacteremia and septicemia

A

Bacteremia refers to the presence of bacteria in blood without any multiplication
Septicaemia is a condition in which bacteria circulate and actively multiply in the blood stream and may produce their products like toxins

32
Q

Fungemia

A

Usually a serious condition, occurring primarily in immunosuppressed individuals, patients with malignancies, patients in chemotherapy and in those with serious or terminal illness

33
Q

Stages of blood stream infection

A
  1. Bacteremia
  2. Sepsis:
    Fever, hypothermia
    Hyperventilation
    Skin lesions, mental changes, diarrhoea
  3. Septic shock:
    Hypotension
    DIC
    Multi organ failure
34
Q

Parameters of SOFA score

A

Diagnosis of sepsis

  1. Respiratory system-PaO2/FiO2
  2. Coagulation system- platelet count
  3. Liver-serum bilirubin
  4. Cardiovascular- mean arterial pressure MAP
  5. CNS: Glasgow Coma Scale
  6. Renal: serum creatinine and urine output
35
Q

qSOFA criteria

A

At bedside

  1. Respiratory rate >= 22/min
  2. Altered mentation
  3. Systolic blood pressure <= 100mm Hg
36
Q

Septic shock

A

Persisting hypotension requiring vasopressors to maintain MAP >= 65 mmHg
Serum lactate > 2 mmol/L despite adequate volume resuscitation

37
Q

Media used for conventional blood culture for bloodstream infections

A
  1. Monophasic medium:
    Contains 50-100 mL of brain heart infusion broth
  2. Castaneda’s biphasic medium:
    It consists of BHI agar slope and BHI broth
    Dilution of 1:5, so the antibacterial agents are diluted
    SPS is added to the medium as an anticoagulant. It also counteracts the antibacterial agents.
38
Q

Fever of unknown origin

A

Prolonged febrile illness without an established etiology despite of intensive evaluation and diagnostic testing

  1. Fever >=38.3°C in at least two occasions
  2. Duration of illness >= 3 weeks
  3. No known immunocompromised state
  4. Diagnosis that remains uncertain after a thorough history-taking, physical examination and some obligatory investigations
39
Q

Etiology of fever of unknown origin FUO

A 
1. Infections: 36%
 Both localised and systemic
2. Neoplasms: 19%
 Lymphoma, myeloma, leukaemia,...
3. Non-infectious inflammatory diseases: 19%
 Rheumatic arthritis, SLE
4. Miscellaneous: 19%
 Metabolic diseases, granulomatous diseases
5. Undiagnosed: 7%
40
Q

Microscopic investigations of bloodstream infections

A
  1. Blood microscopy
  2. Stool wet mount
  3. Gram stain
  4. Acid fat stain
  5. Periodic acid schiff stain
41
Q

Culture specimens used for bloodstream infections

A
  1. Blood culture
  2. Culture on Lowenstein Jensen medium or M. tuberculosis
  3. Puss and exudate specimens
  4. Sabouraud Dextrose Agar
  5. Cell line culture
42
Q

Serological tests for bloodstream infections

A
  1. ELISA and rapid tests for viral diseases
  2. Standard agglutination test for brucellosis
  3. Microscopic agglutination test for leptospirosis
  4. Cold agglutination test for mycoplasma
  5. Weil Felix test for rickettsial disease
  6. Paul Bunnell test for IM
  7. Widal test
  8. Microimmunofluorescence test for chlamydia
  9. RA factor
  10. Anti nuclear antibody detection
42
Q

Microorganism causing iron deficiency anaemia

A
  1. Hookworm
    • Necator or Ancylostoma
  2. Trichuris trichura
  3. Schistosoma species
44
Q

Microorganism causing megaloblastic anemia

A

Diphyllobothrium latum

45
Q

Microorganisms causing haemolytic anemia

A
  1. Malaria
  2. Babesia microti
  3. Bartonella bacilliformis
  4. Clostridial sepsis
  5. Mycoplasma pneumoniae
  6. Infectious mononucleosis (EB virus)
  7. Hepatitis A virus

Microbiology MBBS (16 decks)

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