Cardiovascular Flashcards
What are the three types of circulation
Pulmonary - Deoxy blood to lungs and oxygenated to heart
Systemic - Oxygenated blood away from the heart to the body and deoxy blood back to the heart
Coronary - circulation of the blood within the heart
bacteremia
BLOOD IS STERILE
- presence of living organism in the blood
-isnt always a blood infection
-can be dental work, injury, surgery
-transient because immune system kills it
-person can be asymp or have mild fever
pseudo- bactermia
false positive blood culture due to improper phlebotomy - no illness
-isolation of skin contaminants like CONs
Occult bactermia
-bacteria in blood of febrile child <2 who has no focus of infection and doesnt look ill
-S pneumo and H flu type used to cause but now with vaccines its not an issue
Transient vs intermittent vs continuous persistent bacteria
classification of bacteremia by duration
Transient - temporary , removed by the immune system
Intermittent -
Periodic seeding by same bacteria from an existing infection - cleared by immune system
Continous/ Persistent
-bacteria from intravacsular source that is released constantly into blood
-always present in blood
-due to heart valve infections, catheters,
Primary vs 2ndary vs bacteremia of unknown origin
classification on site of origin
primary - bacteria in vascular system due to infected cardiac valve or IV catheter
2ndary - bacteria from extravascular source -like lungs in pt with pneumonia
Bacteremia of unknown origin
-source if undefined
-very poor prognosis
Classification determines therapy and prognosis
classification of bacteremia by place of acquisition
Community acquired
from general community
S pneumo
Nosocomial bactermia
healthcare facility acquired
S. aureus, Enterococcus & Enterobacterales
classification of bacteremia by type or # of org
Gram pos, neg, anaerobic or polymicrobial
mix is usually from GIT, burns or IV drug use
SEPTICEMIA
presence & replication of organism in blood = infection of blood.
-bacterial invasion & toxin production evident.
-leads to systemic inflammatory response called Sepsis
Non-infectious inflammatory response sepsis severe sepsis septic shock death
Systemic inflammatory response syndrome (SIR)
-DR uses to categorize spectrum of increasingly severe inflammatory reactions from septicemia.
Fever, altered mental state, drop in systolic blood pressure, elevated resp/heart rate, high WBC
MOST COMMON ORGANISMS CAUSING SEPTICEMIA
Staphylococcus aureus
Escherichia coli
Streptococcus pneumoniae
Extravascular septicemia:
infection in other body part or bacteria that disseminate as part of pathogenesis (Listeria, Salmonella)
-bacteria gets into blood via lymphatics
Intravascular septicemia:
Bacteria directly enters blood
-Intravascular Catheter = temporary ones in peripheral veins or semi permanent ones in central veins
-CoNS, S. aureus & Enterococcus most common gram pos.
-M. avium complex in HIV pos.
INFECTIONS OF THE HEART
bacteria in blood can lead to
Myocarditis
Endocarditis
Pericarditis-infection of sac around heart (Pericardium)
INFECTIVE ENDOCARDITIS
-bacteria seeding heart valves forming a biofilm and infection
-valve damage and heart failure
-bacteria seeds blood causing continuous bacteremia with periodic febrile episodes
Acute endocarditis:
INFECTIVE ENDOCARDITIS
-quick
-affects healthy heart
-caused by virulent bacteria like S. aureus, Enterococci, S. pneumo
HOWEVER S. lugdunensis or Corynebacterium jekeium caused progressive endocarditis in prosthetic heart valves or pace makers
Sub acute endocarditis
INFECTIVE ENDOCARDITIS
-slow progression
-affects hearts that are abnormal or already damaged
-caused by less virulent orgs NF or mouth like Viridans, bovis, mutans,
LAB DIAGNOSIS OF BLOOD INFECTIONS
blood culture
-positive = critical = fatal outcome , contact physician and gram
When are BC collected
fever of unknown origin
-SID symptoms low blood pressure, raised heart & respiratory rate or shock with organ failure
-pt has severe invasive infection
-there is endocarditis
OBTAINING A BLOOD CULTURE
-strict aseptic technique
-Label w patient info, date & time of draw
-Take before antibiotics & from veins- not arteries
-Don’t take from indwelling IV or intra-arterial lines
-draw below IV line
-Cleanse skin with 70%-95% ethanol followed by 2% chlorhexidine - leave on for at least 30sec let air dry
-BC bottles have SPS to inhibit Neisseria and P anaerobius
-Or put blood in tube with anticoagulants - don’t use EDTA, Na citrate or Heparin –can inhibit organism growth.
BLOOD CULTURE VIALS
-O2& ANO2 BC bottles
-Nutritionally enriched have resins or charcoal to absorb toxins & antibiotics.
-SPS is the anticoag that inactivates antibiotics, neutralizes serum bactericidal activity & phagocytosis by immune cells
in ANO2 there is thioglycolate as O2 reducing agent & empty space in neck has gas mix that is not O2.
-drawn in sets -
1 SET = 1 O2 & 1 ANO2 vial - inoculate O2 first –to avoid contamination with air
VOLUME OF BLOOD DRAWN FOR BLOOD CULTURES (BC)
volume of blood is most important to recovery
-bacterial effect of serum in blood has to be diluted by blood culture media
-1: or 1:10 ratio
Adults
10ml per bottle
Children - volume based on weight and special vial used
HOW MANY SETS OF BC TO DRAW
Best is 3-4 sets in 24 hours
-but general practice is 2 sets in 24 hrs
-both sets can be done at the same time but they have to be from different spots or 1-2 hours from different venipuncture site
-if pt is negative after 2 sets in 48 hours keep taking sets or the organism can be viral - NO GROWTH IN BC
SPECIAL CONSIDERATIONS FOR ENDOCARDITIS INVESTIGATION
is acute is suspected or is sub acute is suspected
BC should be taken during fever and before antibiotics
-immune system keeps bacteria levels low but fever will occur when the #s are high
If Acute endocarditis suspected:
Timing of draw is critical, take 2-3 sets of BC in a 30min time period
If sub acute endocarditis is suspected
-timing of draw less important instead focus on getting bacteria when it is increased in numbers in blood - INCREASE SAMPLE VOLUME
-3-5 sets spaced 30min to 1 hour apart in 24hrs
CONTAMINATION OF BC BOTTLES
-False positive
-bacteria growing isnt what is actually in pts blood
-due to contamination from improper technique
-acceptable rate is 2%
-common contaminants are skin flora except in endocarditis
-if skin flora is reported the physician needs to decide if it should be treated
CRITERIA TO DETERMINE CONTAMINATION OF BC VIALS
Identity of organism
S. aureus, Enterobacterales, GAS, S. pneumoniae, P. aeruginosa & C. albicans almost always a true septicemia
CoNS, Micrococcus, diphtheroids & P. acnes are contaminants EXCEPT in endocarditis
CRITERIA TO DETERMINE CONTAMINATION OF BC VIALS
How many bottles is organism growing in
if same organism is in multiple bottles or set then it is a true infection doesnt matter if it is skin flora or not
can be endocarditis
CRITERIA TO DETERMINE CONTAMINATION OF BC VIALS
Isolation of organism from blood + another sterile or non- sterile site.
person has a urine culture with the same organism – could mean a true septicemia
AUTOMATED BC SYSTEM EXAMPLES
BacT ALERT
- colorimetric change caused by shifts in pH from increased CO2 levels due to organism growth
AUTOMATED BC SYSTEM EXAMPLES
BACTEC
Detects changes in fluorescence caused by shifts in pH from increased CO2 levels due to organism growth
AUTOMATED BC SYSTEM EXAMPLES
Versa Trek
measures pressure changes caused by gas consumption or production due to organism growth
What happens when Negative BC:
Preliminary report of No growth after 48 hrs sent on all bottles negative at this time.
Kept for 5 days before final report of No growth sent out
What happens when positive BC:
in BSC L2 - broth removed and inoculated to slide for gram and to BA, CHOC, CNA, MAC, BRUC.
-do gram and issue preliminary
-phone physician with GRAM
-inform which bottles are positive (Aer or Anaero) and in how many sets after how many hours of incubation
WORK UP OF POSITIVE BC
set up ID & AST
-Maldi for some organisms can be done right from the BC vial broth
-centrifuge to concentrate and lyse to remove protein in RBC (interferes with MALDI)
-molecular can be done from the broth as well
-phone and send reports to dr everyday
-BC are like CSF STAT
CORYNEBACTERIUM JEIKEIUM
Less common ORGANISMS THAT CAUSE ENDOCARDITIS OR BACTEREMIA
Normal flora of skin, but MOST COMMON CAUSE of prosthetic joint, native valve endocarditis, sepsis, & meningitis
-nosocomial
-very virulent & multi drug resistant.
Vancomycin drug of choice
Strict aerobe, ppt/small NH, white
small pleomorphic gram pos bacilli
Cat pos
Urease neg
Sucrose - neg
-BC DO MALDI
HACEK ORGANISMS
Less common ORGANISMS THAT CAUSE ENDOCARDITIS OR BACTEREMIA
fastidious, gnb that are slow-growing – may take > 5 days - like increased CO2 for growth
Haemophilus spp. including H. aphrophilus
Aggregatibacter
Cardiobacterium hominis
Eikenella corrodens
Kingella kingae
NF of mouth but can cause mouth infections
-cause native or prosthetic valve endocarditis
-cause subacute endocarditis
-if endocarditis is suspected and BC is negative then subculture the BC to CHOC and keep longer
Capnocytophaga
Less common ORGANISMS THAT CAUSE ENDOCARDITIS OR BACTEREMIA
NF of mouth of human and animals
-peridontal disease
-risky for sick ppl and those who have spleen removed are at risk of septicemia & endocarditis.
-GNB slender with pointed ends (fusiform).
-Facultative but like CO2.
-Slow growing take 48-72hrs.
-Grows on BA/CHOC –sm colonies that look like film that spreads away from center of colony due to gliding motility
-Oxidase: positive
Brucella Species
Less common ORGANISMS THAT CAUSE ENDOCARDITIS OR BACTEREMIA
-infectious (BSL3)-
-from eating unpasteurized dairy
Brucella abortus from cattle
Brucella suis from pigs
Brucella canis from dogs
Brucella melitensis from goat or sheep
CL2- BSC class II with PPE when working with specimen
-CL3 when working with colonies on culture plates. MOST COMMON LAB WORK ASSOCIATED INFECTION
-arthritis and spleen/liver enlargement
-can invade cells and cause septicemia, endocarditis and meningitis
Brucella LAB TESTING
tests from colony must be CL3 –sent to PHL
-blood, tissues, fluids, bone marrow.
-Cultures incubated 21 days before negative report can be sent out.
-BA, CHOC & Brucella agar in 5-10%CO2.
- BA: small, grey NH MAC: NG
-Gram: gncb,
-Oxidase & Urease: positive - ID to genus level.
- use MALDI or PCR.
-Serology
Reported to MOH –potential bioterrorism agent.
Treatment is combination of multiple antibiotics
OTHER ORGANISMS TO CONSIDER IF BC IS POSITIVE BUT SUBCULTURE IS NG
Nutritionally variant Streptococci
Abiotrophia & Granulicatella
-Oral NF but can cause endocarditis & septicemia.
-needs pyridoxal (vitamin B6) to grow
-Can add to BA ingredients or as a disk or a staph streak.
-satellite around Staph as NH or AH colonies
-grows in BC vials because human blood has vitamin B6.
-Gram: pleomorphic cocci both in pairs & chains that may look bacillary
OTHER ORGANISMS TO CONSIDER IF BC IS POSITIVE BUT SUBCULTURE IS NG
Campylobacter spp. :
-gastroenteritis, from eating undercooked meat or animal products
-can be missed in BC because it only grows on CHOC or CAMPY because it like a microaerophilic conditions 42C for 48 hours
-hard to see on gram
-use fuchcin counterstain
-acridine orange fluorescent stain
-small curved GNB - gull wings
OTHER ORGANISMS TO CONSIDER IF BC IS POSITIVE BUT SUBCULTURE IS NG
Mycobacteria (BSL3):
-BC media needs enrichment like LJ or Middlebrook base
- 6-8 wks. to grow.
-Mycolic acid won’t stain with gram –use ZN, kinyoun or Auramine Rhodamine.
OTHER ORGANISMS TO CONSIDER IF BC IS POSITIVE BUT SUBCULTURE IS NG
Coxiella burnetii (BSL3):
-Zoonotic, from cows or goats- highly infectious, transmitted by inhalation or rarely by eating raw animal products.
-<5% of those infected especially those with valve defects or vascular grafts will get endocarditis – called Q fever
-Gnb, fastidious, obligate intracellular pathogen, won’t grow on routine media.
-Must use serology to diagnose endocarditis.
Fungemia
Fungal growth in blood
C albicans - most common
-yeast is quick to grow in vials
-dimorphs grow in vials but they take longer and can be missed after the 5 day incubation check
-if youre investigating a slow grower sub negative BC vials to fungal plates & keep up to 4 weeks
Viremia:
Presence of virus in blood
BC are negative
Diagnosed by serology or molecular testing
