Unit 5 - Blood Stream Infections

What defenses are used for the cardiovascular system?

• blood-borne components of innate / adaptive immunity

  • phagocytosis

  • adaptive immunity

• normal biota: WBC

What defenses are used for the lymphatic system?

• numerous innate defenses

• normal biota: unclear

Bacteriema

• viable organisms in blood

• threatens all organ systems

Continuous Bacteremia

• meningitis

• osteomyelitis

• osteoarthritis

• pneumonia

• typhoid fever

• peritonitis

Transient Bacteremia

• after manipulation of mucous membranes or infected tissues

What are the different entry of organisms into blood?

• Genitourinary 25%

• Respiratory 20%

• Abscess 10%

• Surgical wound 5%

• Biliary Tract 5%

• Miscellaneous 10%

• Unknown origin 25%

Septicemia

• bacteremia + clinical presentation of signs and symptoms of bacterial invasion and toxin production

What are the different bacterial toxins in the bloodstream?

• Endotoxin or lipopolysaccharide (LPS) - gram negative

• Exotoxins: gram negative and gram positive

What are the stages of sepsis?

1. microorganisms enter the bloodstream / cause inflammation

2. Severe sepsis

   1. systemic inflammatory response, and organ involvement

3. Septic Shock

   1. sepsis + refractory hypotension

What are signs / symptoms of sepesis

• fever > 38 or hypothermia < 36

• tachycardia

• tachypnea

• hypotension

• followed by organ involvement

• abrupt onset: shaking, chills,fever, hypothermia

• delirium, stupor, agitation, nausea, vomiting

• acute renal failure

What are lab findings of septic shock?

• leukocytosis (total WBC > 10,000 leukocytes/mm³)

• ↑ BUN / creatinine

• ↑ liver enzymes

• decreased PO2

• elevated CRP

• elevated procalcitonin

• lactate levels?

What are characteristics of septic shock?

• acute circulatory failure caused by toxins of microorganisms

• multiple organ failure

• acute respiratory distress

• DIC

• tissue destruction

• death

What are high risk factors for sepsis?

• immunosuppression

• underlying disease: heart disease, rheumatic fever

• medical devises: shunt, graft

• surgery / invasive procedures

• widespread use of broad spectrum antimicrobial agents

• age

• longer survival of debilitated and seriously ill patients

What are SIRS (Systemic Inflammatory Response Syndrome)?

• 2 or more of:

  • fever > 38 (100.4) or < 36 (96.8)

  • Hr> 90 bpm

  • RR > 20 bpm

  • PaCO2 < 32

  • abnormal WBC

    • > 12,000

    • < 4,0000

    • > 10% immature (band) forms

What is used to treat sepsis?

• antimicrobial agents

  • start empirically → identify organism → switch to more effective agent

  • B lactams + aminoglycoside = common

• Increased BP

• Oxygen

• Hemodialysis

• Physiologic support : IV fluids

• Anticoagulation : curb DIC

• Anticytokine therapies: investigational agent

Phlebitis

• infection / inflammation of veins

Endocarditis

• infection / inflammation of inner lining of arteries

Carditis/ Myocarditis

• heart muscle

Endocarditis

• infection of the heart, usually the valves

Pericarditis

• infection of the region around the heart

  • ex: pericardial fluid

What are examples of contaminating organisms from the skin?

• coagulase-negative staphylococci

• Corynebacterium spp. (diphtheroids)

• Streptococcus spp.

• Bacillus spp

Examples of Aerobic Gram-Negative Rods

• older enterobacteriales

Glucose Non-Fermenting GNR/GNCB

• Pseudomonas aeruginosa and other pseudomonads

• Acinetobacter sp.

• Stenotrophomonas maltophilia

• Burkholderia cepacia complex

• Elizabethkingia meningoseptica

Fastidious Gram-Negative organisms

• Haemophilus influenzae

• Neisseria meningitidis

• Brucella sp.

• Streptobacillus moniliformis

Aerobic Gram Positive Organisms

• Staphylococcus aureus

• Coagulase-negative staphylococci

  • S. lugdunensis, S. epidermidis, etc.

• Viridans streptococci: S. mutans group (S. mutans)

• Nutritionally-variant streptococci

  • vitamin B6-dependent streptococci (Abiotrophia sp.)

• Enterococcus sp.

What is associated with neonatal spesis?

• Beta-hemolytic Streptococci (group B)

What is associated with pneumonia?

• Streptococcus pneumoniae

What is asscociated with Pregnant women?

• Listeria monocytogenes

Anaerobic Gram Negative Rods

• Bacteroides fragilis

• Other Bacteriodes spp.

• Capnocytophaga ochracea

Anaerobic Gram-Positive Rods

• Clostridium perfringens

• Clostridium septicum

• Finegoldia magna

• Peptostreptococcus sp.

• Cutibacterium acnes

Mycobacteria

• Mycobacterium tuberculosis

• Mycobacterium avium complex

Spirochetes

• Borrelia spp.

• Leptospira spp.

Fungi

Yeasts

• Candida albicans

• Other Candida spp.

• Cryptococcus neoformans

Filamentous fungi

• Malassezia furfur

• Histoplasma capsulatum

• Coccidiodes immitis

• Blastomyces dermatitidis

• Rhizopus spp.

What is a hazardous isolate encountered in blood?

• Francisells tularensis

What is the special concern for AIDS patients and microorganisms encountered in blood

• suspect mycobacteria, fungi, viruses

What is the primary pathogen seen in Acute Infective Endocarditis

• Staph. aureus

• Strep. pneumoniae

Describe Acute Infective Endocarditis

• rapid: hrs -days

• attacks normal, healthy valves

• severe toxicity

• complications

  • acute valvular regurgitation, heart failure, septic shok, early arterial emboli

What are risk factors for Acute Infective Endocarditis

• IV drug users

• central venous catheters

• invasive surgical / healthcare exposures

What is used to treat Acute Infective Endocarditis?

• high acute mortality

• needs immediate blood cultures

• emergent empiric IV antibiotics

What pathogen is associated with subacute infective endocarditis (SBE)

• Viridans group streptococci

  • S. sanguinis

  • S. mutans

• Enterococcus faecalis

Describe subacute infective endocarditis

• develop over weeks - months

• attacks pre-damaged, abnormal, prostetic valves

• mild - moderate malaise, fatigue, anorexia, weight loss

• complications

  • heart failure, anemia of chronic disease, subacute systemic emboli

What are risk factors for subacute infective endocarditis ?

• poor dental hygeine/ dental procedures

• pre-existing structural heart lesions

What is used to treat subacute infective endocarditis

• treatable if diagnosed early

• needs many blood cultures before targeted therapy

What Gram Positive Cocci are often seen in Infectious Endocarditis

1. S. aureus - acute

2. S. pneumoniae - acute

3. coagulase-negative staphylococci

4. Viridans streptococci

   1. S. mitis group - sub acute

5. Enterococcus and Streptococcus bovis

What Nonfermentors are often seen in Infectious Endocarditis

• Pseudomonas

• Acinetobacter

What members of the HACEK Group are seen in Infectious Endocarditis?

• Aggetbacter (Haemophilus) aphrophilus

• Aggregatibacter (Actinobacillus) actinomycetemcomitans

• Cardiobacterium hominis

• Caphnocytophaga

• Eikenella corrodens

• Kingella kingae

What is used to treat Native Valve Endocarditis

• Penicillin G + Gentamicin

  • covers streptococci

What is used to treat intravenous drug use Endocarditis?

• nafcillin + gentamicin

  • methicillin-sensitive staph

• vancomycin

  • MRSA

What is used to treat Prosthetic valve endocarditis

• vancomycin + gentamicin

  • MRSA

  • coagulase-negative staph

What is used to treat HACEK microorganisms?

• ceftriaxone

What is the most important variable for blood culture detection?

• volume of blood collected

  • increase volume = increase in pathogen recovery

What is the correct Blood-to-Broth ratio

• 1:5 to 1:10

What are the correct volumes of blood collected?

• 20 ml (2 bottles) - adults

• 2 ml for newborn weighing < 1 kg

• 4 ml from newborn weighing > 2 kg

What is important for specimen collection?

1. volume of blood collected

2. Blood-to-broth ratio

3. skin disinfection is critical

4. draw prior to antimicrobial therapy

5. number of cultures

   1. need more than 1

   2. 3 are recommended

6. Timing

   1. collect before anticipated temperature rise

   2. for Bacterial endocarditis

      1. take 3-4 sets from different venipuncture sites at 30-60 minute intervals

What should contamination rates be for specimen collection

• < 3%

What could indicate contamination of a single positive culture is growing?

1. Coagulase-negative staphylococci

2. Corynebacterium

3. Cultibacterium

4. Streptococcus

5. Bacillus

What is needed for the first step of specimen collection: Gather materials needed for blood draw?

1. sterile gloves

2. alcohol and iodophor (iodine compound)

   1. 2% chlorhexidine with/without alcohol

3. do NOT use iodine for neonates

4. double needle collection set or vacutainer setup

5. aerobic / anaerobic blood culture bottles

6. tourinquet

What is the protocol for Specimen Collection

• prepare blood culture bottles

• prepare skin for venipuncture

  • NEVEW draw through indwelling catheter

  • ALWAYS draw below IV line

  • locate / palpate vein

  • swab with alcohol

  • swab with iodophor/let sit for 30 sec - 1 min

• perform venipuncture

  • inoculate aerobic/anaerobic blood culture bottles

  • label bottles accurately

What is the preferred source for routine blood cultures?

• fresh peripheral venipuncture

  • draw from a line only when peripheral access fails

How should blood specimen be stored/ transported

• transport: within 2 hrs

• hold specimen at room temp or 35C

What are the rules of specimen collection for adults?

• 20-30 ml/culture/venipuncture

• 3 cultures over 24 hr period

• > 80 lbs: 30-40 ml / 2 blood cultures

What are the rules for specimen collection for baterial endocarditis /acute infective endocarditis

• 3-5 culture sets total

• 3 sets drawn

  • if negative at 24 hrs: obtain 2 more sets

    • if still negative: consider new diagnosis

What are the specimn collection rules for subacute inefective endocarditis?

• establish diagnosis

• obtain 3-5 sets

• antimcirobial therapy