Infectious Disease - Principles in Abx Selection Handout Flashcards
Gram Stain Positive color
PURPLE
Gram Positive Cocci in clusters: Coagulase positive
S. aureus
Gram Positive Cocci in clusters: Coagulase negative
S. epidermidis S. lugdunensis S. hominis S. saprophyticus S. haemolyticus S. capitis
Gram-positive cocci in pairs
Streptococcus pneumoniae
Gram-positive cocci in chains:
Viridans streptococci (α-hemolytic):
S. milleri S. mutans S. salivarius S. mitis S. sanguis
Gram-positive cocci in chains:
Group streptococci (β-hemolytic):
Group A (S. pyogenes),
Group B (S. agalactiae)
Group C (Streptococcus equi)
Group D (S. bovis, S. equinus),
Groups F and G streptococci (S. dysgalactiae)
Gram-positive cocci in pairs & chains
Enterococcus spp. (E. faecalis, E. faecium, E. durans, E. gallinarum, E.
avium, E casseliflavus, E. raffinosus)
Gram-positive bacilli classifications
non spore forming
spore forming
branching, filamentous
Gram-positive bacilli classifications:
non spore forming
Corynebacterium spp. (C. diphtheriae, C. jeikeium, C. striatum, etc.)
Lactobacillus spp.
Listeria monocytogenes
Gram-positive bacilli classifications:
spore forming
Bacillus spp. (B. anthracis, B. cereus, etc.)
Streptomyces spp.
Gram-positive bacilli classifications:
branching, filamentous
Erysipelothrix rhusiopathiae
Nocardia spp. (N. asteroides)
Gram Stain Negative color
red
Gram-negative cocci
Neisseria spp. (N. gonorrhoeae, N. meningitidis, etc.)
Moraxella catarrhalis
Gram-negative coccobacilli
Haemophilus spp. (H. influenzae, H. parainfluenzae, H. ducreyi, etc.)
Gram-negative bacilli examples
lactose-fermenting
non lactose fermenting
other gram negative bacilli
Gram-negative bacilli:
lactose fermenting
Aeromonas hydrophila
*Citrobacter spp. (C. freundii, C. koseri)
*Enterobacter spp. (E. cloacae, E. aerogenes [Klebsiella aerogenes])
*Escherichia coli
*Klebsiella spp. (K. pneumoniae, K. oxytoca)
Pasteurella multocida
Vibrio cholerae
Gram-negative bacilli:
non lactose fermenting
Acinetobacter spp. (A. baumannii)
Alcaligenes spp.
Burkholderia cepacia
*Morganella morganii
*Proteus spp. (P. mirabilis, P. vulgaris)
*Providencia spp. (P. rettgeri, P. stuartii)
Pseudomonas spp. (P. aeruginosa, P. putida, P. fluorescens)
*Salmonella spp. (S. typhi, S. paratyphi, S. enteritidis, S. typhimurium)
*Serratia marcescens
*Shigella spp. (S. dysenteriae, S. sonnei)
Stenotrophomonas maltophilia
Gram-negative bacilli:
other gram negative bacilli
Brucella spp. Bordetella spp. Campylobacter jejuni Francisella tularensis Helicobacter pylori
Define gram variable
stain both Gram-positive and Gram-negative in the same smear
Gram-variable bacilli example
Gardnerella vaginalis
Miscellaneous organisms where Gram stain
is typically not useful: 2 groups
atypical bacteria (Cell walls difficult to stain; Mycoplasma lack a cell wall)
spirochetes (Motile, corkscrew-shaped organism visualized
using dark field microscopy)
Miscellaneous: atypical bacteria examples
Chlamydophila pneumoniae
Chlamydia trachomatis
Legionella pneumophila
Mycoplasma pneumoniae
Miscellaneous: spirochetes
Treponema pallidum (syphilis) Borrelia burgdorferi (Lyme disease) Leptospira interrogans
Gram stain positive (anaerobic): gram positive cocci in chains
Peptostreptococcus spp. (P. anaerobius, P. intermedius) Finegoldia magna (formerly P. magnus)
Gram-positive bacilli (anaerobic): examples
non-spore forming
spore forming
branching, filamentous
Gram-positive bacilli (anaerobic):
non spore forming examples
Cutibacterium spp. (C. acnes [formerly Propionibacterium acnes])
Gram-positive bacilli (anaerobic):
spore forming
Clostridium spp. (C. perfringens, C. tetani, C. botulinum)
Clostridioides difficile
Gram-positive bacilli (anaerobic):
branching, filamentous
Actinomyces spp. (A. israelii)
Gram negative (anaerobic) cocci
Veillonella spp. (V. parvula)
Gram negative (anaerobic) bacilli
Bacteroides spp. (B. fragilis, B. thetaiotamicron, B. ovatus, B. distastonis)
Fusobacterium spp.
Normal flora: Skin
Diphtheriods (e.g., Corynebacterium spp.)
Staphylococci (esp. S. epidermidis)
Streptococci
Propionibacterium spp.
Normal flora: Oropharynx
Haemophilus spp.
Streptococci (viridans group)
Diphtheriods (e.g., Corynebacterium spp.)
Neisseria spp.
Oral anaerobes
Normal flora: gastrointestinal tract
Bacteroides spp.
Enterobacteriaceae
Enterococci
Fusobacterium spp.
Peptostreptococcus spp.
Clostridium spp.
Normal flora: Genital tract
Corynebacterium spp.
Enterobacteriaceae
Lactobacillus spp.
Mycoplasma spp.
Staphylococci
Streptococci
Anaerobes
Candida spp.
Fever is a ________ of infection
hallmark
Fever significant if oral temperature
> 38.0°C (100.4°F)
Rectal temperature generally 0.6°C (1°F) ______;
axillary temperature generally
0.6°C (1°F) ______
higher
lower
non-infectious causes of fever
Malignancy, collagen vascular disease (autoimmune)
Drug fever – fever coincides temporally with administration of the offending
agent and disappears promptly with withdrawal of the offending agent
Blood transfusions
Drug fever offending agents
β-lactam antibiotics, anticonvulsants, allopurinol, hydralazine,
nitrofurantoin, sulfonamides, phenothiazines, methyldopa
Absence of fever in a patient with signs and symptoms consistent with an
infection (false-negatives) EXAMPLES
Antipyretics – discourage during treatment of infection (may mask poor
therapeutic response)
Corticosteroids
Antimicrobial therapy (partial)
Overwhelming infection
Signs and symptoms of infection
Fever (temp > 38°C)
Increased white blood cell count
Chills, rigors
Tachycardia (> 90 beats/min)
Tachypnea (> 20 breaths/min)
Hypotension (SBP < 90 mmHg or MAP < 70)
Malaise
Mental status changes
Normal WBC count
4,500 to 10,500/mm3
Mature neutrophil (PMNs, polys, segs) normal range
50 - 70%
Immature neutrophils (bands) normal range
0 - 5%
Eosinophils normal range
0 - 5%
Basophils normal range
0 - 2%
Lymphocytes normal range
15 - 40%
Monocytes normal range
2 - 8%
Leukocytosis (increased neutrophils ± bands) – associated with
bacterial infection
Presence of immature forms (left shift) is an indication of
an increased
bone marrow response to the infection
elevated neutrophils +/- bands potentially due to
non-infectious diseases (e.g., leukemia, stress)
or
drug therapy (e.g., steroids, lithium)
elevated neutrophils +/- bands may be absent due to
neutropenic hosts; blunted in elderly
Leukopenia (abnormally low WBC count) may be sign of
an overwhelming infection; poor prognostic sign
B-lymphocytes ® proliferate into _________, which produce antibodies
involved in ________ immunity; some develop into memory cells
plasma cells
humoral
T-lymphocytes – involved in ____________ immunity
cell-mediated
T helper/inducer cells (CD4) –> regulation of the immune system; help
with ________ _________ and secrete ____________ that help protect
against bacterial/viral infections and tumors; the major marker of
immunocompetence in patients with ___________ (this cell line is
depleted with HIV infection)
antibody production
lymphokines
HIV infection
T suppressor (CD8) ® bind to and directly kill \_\_\_\_ \_\_\_\_\_; help with regulation of \_\_\_\_\_\_\_\_\_ and \_\_\_\_\_\_\_\_ immunity
tumor cells
humoral
cell-mediated
Define monocytosis
important phagocytic cells responsible for antigen processing
and presentation; associated with tuberculosis or lymphoma
Define eosinophilia
associated with allergic reactions or protozoal/parasitic
infections
Localized signs and symptoms of infection
a. Pain and inflammation – swelling, erythema, tenderness, purulent or abnormal
drainage
• Easily detected in superficial infections or infection of the bone or joint
b. Inflammation in deep-seated infections (e.g., pneumonia, meningitis, urinary
tract infection) – must examine tissues/fluids (sputum, CSF, urine)
c. May be absent in neutropenic hosts
ESR and CRP and infection
Elevated in the presence of an inflammatory process but does not confirm the
presence of infection
Normal ESR values
0 to 15 mm/hr in males
0 to 20 mm/hr in females
Normal CRP values
0 to 0.5 mg/dL
ESR and CRP elevated in presence of which infections
otitis media,
osteomyelitis, prosthetic joint infections, endocarditis, pelvic inflammatory
disease, and infections in transplant patients
Serial measurement of ESR and CRP may be useful in assessing response to…
treatment of deep-seated infections, such as endocarditis or osteomyelitis
PCT and infections
A precursor of calcitonin, a calcium regulatory hormone, which is a more
specific marker for bacterial infections than ESR or CRP
Some data suggest that PCT levels may be useful for assessing the efficacy of
empiric antibiotic therapy as well as for determining when antibiotic therapy
can be discontinued during the treatment of an infection
Normal PCT value
Normal value = < 0.05 μg/L
Meaning of PCT ≥ 10 μg/L ®
sepsis/systemic bacterial infection
Meaning of PCT between 2 and 10 μg/L
suggestive of sepsis
Meaning of PCT between 0.25 and 2 μg/mL
other condition or localized infection
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