Infectious Disease Introduction Flashcards
What cells make up a WBC differential? What might be observed when using a differential for a patient has an infection?
Neutrophils > Lymphocytes > Monocytes > Eosinophils > Basophils
Bacterial infection might cause a left shift (increase in number of immature leukocytes especially neutrophil band cells, since body is working hard to rapidly mount a defense)
Define Minimum Inhibitory Concentration (MIC), and what are the 3 breakpoints?
MIC: lowest concentration of antibiotic that inhibits visible growth of the bacteria
- Susceptible = can treat with appropriate recommended doses
- Intermediate = can appropriately treat in body sites where drug is physiologically concentrated or if high dose is used
- Resistant = inhibition not achievable by concentration from normal dose
List the (aerobic) gram positive cocci
Coagulase positive: Staphylcoccus aureus - MSSA or MRSA
Coagulase negative: Staph. epidemidis and Staph. saprophyticus
Enterococcus faecalis, enterococcus faecium, enterococcus durans
Streptococcus pneumoniae (pneumococcus)
Beta-hemolytic: Streptococcus pyogenes (GrpA), streptococcus agalactiae (GrpB), streptococcus bovis (nonenterococci GrpD)
Alpha-hemolytic/Viridians: Streptococcus sangius, streptococcus salivarius, streptococcus mitis, streptococcus mutans
Where do staphylococci colonize? What infections do they cause?
Colonize skin and nose
Major role in post-surgical infection and can adhere to foreign materials and catheter
Infections: cellulitis/wounds/trauma, bacteremia/endocarditis, pneumonia, osteomyelitis, UTI
What has staphylococci developed resistance to? Any solutions?
Penicillin resistance by producing beta-lactamase (90% of all are PCN resistant)
Methicillin resistance by MecA gene for novel PBP2a (50% S. aureus resistant, 70% CoNS resistant)
*Methicillin-susceptible isolates are also susceptible to cephalosporins and carbapenems
Where do Streptococci colonize and what infections do they cause?
Colonizes skin (GrpA S. pyogenes), mouth (anaerobes, viridans strep), nasopharynx (GrpA S pyogenes), lower GI (GrpD S bovis, viridans strep), and female genital tract (GrpB S agalactiae)
Infections: cellulitis (GrpA S pyogenes may cause necrotizing fasciitis), dental carries (viridans strep), pharyngitis (strep throat i.e. Group A S pyogenes), bacteremia/endocarditis (viridans strep), neonatal meningitis (GrpB S agalactiae)
What is the general treatment for streptococci? Which specific types of streptococci show more resistance?
Use penicillin
More resistance with Alpha-hemolytic strep (specifically S. mitis)
Where do pneumococci colonize and what infections do they cause?
Colonizes oropharyx and nasopharynx
Infections: otitis media, sinusitis, bronchitis, pneumonia (CAP), meningitis
What is the concern for asplenia with pneumococci infection?
At risk for fulminant sepsis syndrome since there is a lack of filtration mechanism of spleen macrophages
Can not clear encapsulated organisms: S. pneumoniae, H. influenzae, N. menigitidis
What is the general treatment for pneumococci?
Due to PBP alterations, there are penicillin-resistant strains
Can use 3rd generation cephalosporins ) i.e. ceftriaxone)
May de-escalate with cultures and sensitivities
*De-escalate = start with broad spectrum until culture results return, then reassess therapy
Where do enterococci colonize and what infections do they cause?
Colonizes GI and female genital tract
Infections: opportunistic, UTI, bacteremia/endocarditis, intra-abdominal infections (but less significant for these in comparison to gram negatives and anaerobes)
Give examples of (aerobic) gram negative bacteria
*this flashcard only includes the bolded ones from lecture, there are many more gram negative bacteria not listed here
Rods:
Enterobacteraciea (i.e. Enterobacter spp, E. coli, Klebsiella pneumoniae, Proteus vulgaris, Proteus mirabilis, Serratia marcenena)
Pseudomonas aeruginosa
Cocci/coccobaccili (i.e. Haemophilis influenzae, Neisseria menigitidis)
Where do enterobacteraciae colonize and what infections do they cause?
*gram negative
Colonizes GI (source usually from soil, water, vegetation) *since gram negative... has LPS, cell wall component and endotoxin
Infections: UTI (70% of them), intra-abdominal, bacteremia, nosocomial pneumonia, diabetic foot infections
How is treatment guided for enterobacteraciae?
Resistance is prevalent and is more common in hospital-acquired infections
Treatment guided by in vitro susceptibility
Where can pseudomonas colonize and what infections do they cause? Name a specific example.
i.e. Pseudamonas aeruginosa = can colonize upper respiratory tract of immunocompromised patients (i.e. COPD, CF)
Not considered normal flora since found in soil/water/vegetation
Also is OPPORTUNISTIC so will attack immunocompromised, after broad spectrum antibiotics, and those on ventilation equipment
Pseudomonas infections: nosocomial infections i.e. HAP
Also febrile neutropenia, skin and soft tissue (burns, trauma, post-surgery), and UTI
Name the SPACE organisms, why is “double covering” needed to treat these?
SPACE = Serratia, Pseudomonas, Acinetobacter, Citrobacter, Enterobacter
Double covering means using two antibiotics to cover the same organism (the nasty ones)
Based on empiric treatment and may provide synergistic/additive effects especially for potentially resistant bacteria that may otherwise survive (but will cause more adverse effects)
Give specific examples of cocci/coccobacilli (gram negative) and whether they are encapsulated or not
Haemophilus influenzae: if it is encapsulated it is not a regular colonizer but is more virulent and causes meningitis… if it has no capsule then it colonizes the upper respiratory tract and can cause otitis media, sinusitis and CAP
Neisseria menigitidis: it is encapsulated and colonizes the oro/nasopharynx, can cause meningitis and less commonly pneumonia
*humans are its only natural host
Why does a polysaccharide capsule make it difficult to treat the bacteria that has it?
Capsule helps the bacteria elude the immune system and requires the spleen to be eliminated
Polysaccharide is the target for Haemophilis influenza type B (Hib) and Meningococcal vaccine
Give 3 examples each of anaerobes found above and below the diaphragm
Above diaphragm: Peptostreptococcus spp (gram positive cocci), Actinomyces spp (gram positive rod), Fusobacterium (gram negative rod)
Below diaphragm: Bacteriodes fragilis (gram negative rod), Lactobacillus (gram positive rod), Clostridium spp (gram positive rod)
Which isolates are usually penicillinase producers?
Gram-negative isolates
Anaerobes are a diverse group and are found above and below diaphragm, where do they colonize and what infections do they cause?
Colonizes upper and lower GI tract as well as vagina
Infections: intra-abdominal, aspiration pneumonia, endometritis, PID, diabetic LE infections, dental carries, head and neck infections
What are considered atypicals (bacteria)? Give 3 examples
Not normal colonizers and not able to gram stain
Multiply intracellularly
i. e. Mycoplasma pneumonia, Legionella pneumophilia, Chlamydophila pneumoniae
* Result in CAP
Give an example of a bacteria that causes HAP
Viridans streptococcus
Give 3 examples of bacteria that can cause CAP
S. pneumoniae
Atypicals
H. influenzae
