Bacteriemia and sepsis

Transcription

1 Bacteriemia and sepsis

2 Case 1 An 80-year-old man is brought to the emergency room by his son, who noted that his father had become lethargic and has decreased urination over the past 4 days. The patient was homebound and over the past week had remained in bed. His medical history included several bouts of acute urinary tract obstruction and an enlarged prostate gland. On physical examination, the patient is febrile (38C), hypotensive (95/55 mm Hg). His mucous membranes are dry and skin turgor is poor. The urinary bladder is percussable to the level of the umbilicus. Rectal examination shows an enlarged prostate. The white blood count is 15000/mm 3.

3 Case 1 -What is the most likely cause of this patient`s problem? - What diagnostic tests are indicated? - Should the patient be hospitalized? - Should antibiotic therapy be started, and if so, with what type of agent or agents? - What is appropriate follow-up?

4 Case 2 A 21-year-old male college student reports a 3-day history of fever and a 2-day history of dizziness on standing. Five days earlier, the patient had sustained a crushing injury to the lateral forefoot, resulting in an abrasion and laceration. The area became swollen, hot, red, and tender over the next 4 days, with yellow drainage from the laceration. Physical examination shows a temperature of 38C, a blood pressure of 100/60 m Hg and a pulse rate of 100 beats/min. The patient`s face and trunk are flushed. Puffy edema of the face and extremities is noted. The right foot is swollen, red, and hot, and the lateral aspect of the forefoot is lacerated, with copious yellow pus exuding from the laceration. A Gram stain of the wound exudate shows Gram-positive cocci in clusters with numerous PMN cells.

5 Case 2 - What is the best diagnosis? - What is the pathophysiology behind the patient`s systemic signs and symptoms? - What tests are necessary to confirm the diagnosis? - What antibiotic treatment should the patient receive? - What immediate comlications are anticipated and how should they be treated?

6 Bacteremia is defined by isolation of bacteria from peripheral blood - sources: trauma, a focus of infection from the human body

7 Bacteremia transient inconsequental - Bacteremia may led to the establishment of distant foci of infection (meningitis, pneumonia, osteomyelitis, etc.) - Bacteremia may progress to septic shock

8 Sepsis (septicemia) is a systemic disease triggered by an infection and characterized by hemodynamic abnormalities and organ failure. - if untreated, the condition progresses to circulatory collapse (septic shock), disseminated intravascular coagulation (DIC), multiple organ failure and death

9 Diagnosis of bacteremia bacteria must be isolated from the blood Organism Frequency of isolation Gram-positive cocci Gram-positive rods Gram-negative rods Anaerobes Fungi 31-41% 1% 47-61% 2-17% 2-12%

10 Laboratory diagnosis Various factors influence the successful recovery of bacteria from blood: 1. attantion to proper technique for blood collection - the skin at the site of venipuncture should be troroughly disinfected - blood should be drawn from two different sites

11 Laboratory diagnosis Various factors influence the successful recovery of bacteria from blood: 2. multiple samples should be taken - 3 blood samples taken over 24h allow for successful recovery of bacteria in 99% of patients with bacteremia

12 Laboratory diagnosis Various factors influence the successful recovery of bacteria from blood: 3. blood for culture should be drawn before initiating antimicrobial therapy

13 Blood culture Volume of blood:10-30 ml for adults and 1-5 ml for children The blood collected is then injected into blood culture bottles The blood is injected into two bottles: one is incubated anaerobically and other aerobically.

14 Treatment of bacteremia and sepsis Immediate, aggressive therapy is mandatory when bacteria are isolated from blood broad-spectrum antimicrobial agents (with relatively low toxicity are preferred)

15 Bacteremic infections and sepsis Gram-negative bacteremia Etiology: members of the families - Enterobacteriaceae E. coli - 35% cases Klebsiella, Enterobacter, Serratia - 38% cases - Pseudomonadaceae Pseudomonas aeruginosa - 12% cases

16 Bacteremic infections and sepsis Gram-negative bacteremia Origin: - gastrointestinal tract - urinary tract - skin

17 Bacteremic infections and sepsis Gram-negative bacteremia Predisposing factors: - surgery (abdominal, genitourinary) - urinary track manipulations (catheterization) - underlying diseases that may compromise the patient`s defenses - large blood loss - ischemia of the intestinal wall

18 Bacteremic infections and sepsis Gram-negative bacteremia Pathogenesis - Gram-negative bacteria release LPS (endotoxin) - LPS activates macrophages (IL-1, TNFα, IL-8) - LPS activates the complement - LPS activates coagulation systems

19 Bacteremic infections and sepsis Gram-negative bacteremia Special types of Gram-negative bacteremia - Bacteroides bacteremia origin: abscess, oral cavity, genitouretral tract predisposing factors: hospitalized patients, womenfollowing septic abortion

20 Bacteremic infections and sepsis Gram-negative bacteremia Special types of Gram-negative bacteremia - Meningococcemia - N. meningitidis A, B - lead to meningitis - pethechial hemorrhages are the most characteristic finding on physical examination

21 Bacteremic infections and sepsis Gram-positive bacteremia S. aureus viridans streptococci Str. pneumoniae anaerobic cocci

22 Bacteremic infections and sepsis Gram-positive bacteremia Pathogenesis: S. aureus and S. pyogenes release exotoxins that act as superantigens (activate MHC-II molecules on macrophages and stimulate large number of TLy----released cytokines)

23 Bacteremic infections and sepsis Gram-positive bacteremia Special types of Gram-positive bacteremia - Staphylococcal bacteremia - origin: cutaneous abscess or furuncule, contaminated intravascular catheters, etc. S. aureus - Staphylococcal toxic shock syndrome (TSS)

24 Case 1 revisited The elderly patient with urinary tract obstruction most likely has Grm-negative bacteremia, probably caused by E. coli originating from the urinary tract. Blood samples for culture should be drawn immediately. A urinary catheter should be insert and urine should be send for analysis. The patient should be hospitalized, because he is most likely bacteremic, and shows signs of severe dehydration and shock, which strongly suggest sepsis. The patient should be given antibiotics. A combination of a betalactam and an aminoglycoside antibiotic should be used. Within 1-2 days, when blood culture and urine culture results are available, change the therapy according to AST.

25 Case 2 revisited In the case of the college student with foot injury, the best diagnosis is sepsis and shock due to staphylococcal wound infection, specifically TSS. The toxin produced in the wound by S. aureus (TSST-1) is liberated into the blood stream and caused shock ---local infection and systemic intoxication Cultures of the wound pus and at least 2 sets of blood cultures are indicated. If S. aureus is cultured, blood can be tested for TSST-1 production. Immediate treatment in a hospital should include a semisynthetic anti-staphylococcal penicillin administered intravenously.