Institute for Microbiology, Medical Faculty of Masaryk University and St. Anna Faculty Hospital in Brno Agents of bloodstream infections Bloodstream infections • Bloodstream infections are not so common as e. g. respiratory of urinary tract infections, but they use to be severe and threatening the patient‘s life • Types of bloodstream infections: – Infection of the complete bloodstream = sepsis – Infection of a part of bloodstream (endocarditis, tromboflebitis); usually leads to sepsis Bacteremia = mere presence of bacteria in blood. Nevertheless: Bacteria (at least higher ammounts of them) = starting mechanism of sepsis Interaction of microbial products with macrophages releases a lot of cytokines → systemic inflammatory response syndrome (SIRS) characterized by – elevated temperature – accelerated pulse and breathing – leukocytosis Sepsis Sepsis = suspect or proved infection + systemic inflammatory response syndrome Severe sepsis = sepsis + organ dysfunction (hypotension, hypoxemia, oliguria, metabolic acidosis, thrombocytopenia, confusion, DIC) Septic shock = severe sepsis + hypotension despite adequate supply of fluids Features of sepsis Clinical: fever or hypothermia (often changing) ↑↓ T tachycardia  P tachypnoe ↑ B lowered blood pressure ↓ BP confusion Pathophysiological: higher heart output lower peripheral vascular resistance Laboratory: leucocytes ↑↓ Leu serum bicarbonate ↓ HCO[3]^- bacteremia may not be already demonstrable Types of bacteremia – I Intermitent bacteremia – in localized infections pneumonia (for example pneumococci) meningitis (for example meningococci) pyelonephritis (Escherichia coli) osteomyelitis (Staphylococcus aureus) septic arthritis (S. aureus, gonococci) and others Types of bacteremia – II Continual bacteremia – in generalized infections typhoid fever (Salmonella Typhi) brucellosis (Brucella melitensis) plague (Yersinia pestis) Pathogens, causing primary, continual bacteremia, are quite rare today. But under some circumstances, also pathogens from „group I“ may perform a continual bacteremia, or rather sepsis Types of bacteremia – III Bacteremia in bloodstream infections thrombophlebitis (S. aureus, S. pyogenes) acute endocarditis (S. aureus, S. pyogenes, S. pneumoniae, Neisseria gonorrhoeae) subacute bacterial endocarditis = sepsis lenta (viridans streptococci, enterococci, HACEK group = Haemophilus aphrophilus Actinobacillus actinomycetemcomitans Cardiobacterium hominis Eikenella corrodens Kingella kingae) „culture-negative“ endocarditis (bartonellae, coxiellae, legionellae) Types of bacteremia – IV Special circumstanses Bacteremia in some malignities (colonic Ca – Streptococcus bovis, leukemia - various bacteria) Bacteremia in intravenous drug users (mostly skin flora – staphylococci, corynebacteria; sometimes also mouth flora and bacteria from the environment) Bacteremia in iatrogenic infections (e. g. mouth floora after tooth extraction, pharyngeal flora after bronchoscopy etc.) Types of bacteremia – V Bacteremia related to artificial material Typically on vascular catheters, invasive devices and implants, endoprotheses etc. (biofilm) More common in emergency units, immunocompromised, febrile neutropenia Caused by coagulase-negative staphylococci, S. aureus, enterococci, corynebacteria, yeasts etc. As the majority of them are normal flora of skin, it is extremelly dificult to differenciate bacteremia from pseudobacteremia here! Candida Sepsis according to the origin • sepsis from wounds (Staphylococcus aureus, Streptococcus pyogenes and other beta-hemolytic streptococci, Pseudomonas aeruginosa in burns) • urosepsis (Escherichia coli, Proteus mirabilis and other enteric bacteria) • abdominal sepsis (often polymicrobial etiology, anaerobes (Bacteroides etc.) and facultative anaerobes (Escherichia coli…) Fulminant sepsis Fulminant sepsis is a sepsis with a quick course; when it is not diagnosed in time, it often kills the patients Clonal strains of Neisseria meningitidis (sepsis with or without meningitis) Streptococcus pyogenes (often together with necrotizing fasciitis of muscle fasciae) Yersinia pestis Nosocomial sepsis Often related with artificial materials Staphylococci, coagulase-negative (intravenous catheter-associated sepsis, infections of plastic devices in situ, febrile neutropenia) Staphylococcus aureus (infected surgical wounds) E. coli + other enterobacteria (catheter-associated infections of the urinary tract) Gram-negative non-fermenting rods (contaminated infusion fluids) yeasts (catheter-associated sepsis, febrile neutropenia) Enterococci and many other microbes Staphylococci in blood culture Diagnostics of sepsis • Blood cultures (not clotted blood; ¹ blood for serological examintion!) – Today mostly in special vessels for authomated culture – At least two, but better two blood culutres, usually at the temperature increase – At least one blood culture should be taken from a new venepunction (i. e. not only central venous cathether) • parts of blood catethers Blood sampling • Aseptically! Not only because of the patient, but also because of the sample. Skin cleaning is not sufficient, disinfection is necessary • The disinfectant should be let to act enough (in alcohol disinfectants it is necessary to let them dry) • Mostly use three identical type vessels, eventualy one for anaerobic culture (especially in suspicion for abdominal origin of sepsis) • It is necessary to fill in the order form carefully, to add the time of material taking Contaminants • Inproper sampling, insufficient disinfection • Sampling from cathehers only and not venepunction (the bacterium colonizing the venous catether is not necesarilly a real bloodstream pathogen) • Coagulase-negative staphylococci Examples of blood culture vessels Blood culture device The same device open Treatment of sepsis At intensive care units only • antibiotics – usually empiric therapy in the beginning, targeted therapy later • removal of all infected tissues or devices • support of breathing and hemodynamics (artificial ventilation, oxygen, fluids, vasopressors etc.) Homework 8 – solution Michael Sweerts (1618-1664): Plague in an Ancient City Homework 9