Bacterial Identification Flashcards
2 reasons culture is better for bacterial diagnostics than PCR
- Cost (urine culture $1 vs $15)
2. Sensitivity (culture better than PCR - might not even pick up the bacteria)
MALDI-TOF
Matrix assisted laser desorption ionization - time of flight
Move to proteomics and using a mass spec
What are protein biomarkers?
Highly expressed proteins responsible for housekeeping functions
Ex: ribosomal (16S) and transcription/translation proteins
These are what are detected in MALDI-TOF
Why is MALDI-TOF better than Vitek?
Cheaper**
Faster
Better
Bacteremia
The presence of bacteria in the bloodstream
2 mechanisms that bacteremia occurs
- Drainage from the primary focus of infection via the lymphatic system to the vascular system (ex: abscess)
- Direct entry from needles, contaminated IV devices, or graft material or trauma
Transient bacteremia
Minutes to hours
Often occurs following manipulation of infected tissues or instrumentation of contaminated mucosal surfaces (ex: brushing teeth)
Onset of acute bacterial infections such a pneumonia, meningitis and septic arthritis
Intermittent bacteremia
Most commonly occurs with un-drained abscesses
Continuous bacteremia
Usually reflects an endovascular infection such as endocarditis or an infected aneurysm
What are some of the most common primary foci
IV devices
Respiratory tract
Urinary tract
Intra-abdominal infections
What 3 bacteria are the most common causes of bacteremia
S. aureus and E. coli the most
Coagulase negative Staph is a close third
What are some poor prognosis findings for bacteremia
Advanced age Nosocomial bacteria (more resistant usually) Enterococcal, gram -'ve, or fungal etiology (harder to treat) Underlying cirrhosis or malignancy Primary focus in the resp tract or skin Surgical wound of abscess Septic shock Lack of a febrile response to sepsis
Nosocomial infections
Hospital acquired infections
Usually more resistant to drugs
Why do you need to dilute the blood in broth?
Diluting greater than 1:5 increases microbial recovery, probably by diluting antimicrobial agents and natural inhibitory factors in the blood
Whats the most common anticoagulant in blood?
SPS