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Antimicrobial Stewardship Training
Part 1: Review of
Basic Principles and Selected Antimicrobials
By Keith Teelucksingh, PharmD
Infectious Disease Pharmacist, Kaiser Permanente Vallejo
With contributions by Linh Van, PharmD
Infectious Disease Pharmacist, Kaiser Permanente Oakland
This course is accepted by the California State
Board of Pharmacy for 2.0 hours of credit.
Provider #127: Accredited by CAPE Coursework
expires: 1/1/2011
Antimicrobial Stewardship Training
An Antimicrobial Stewardship program is a “an
overarching program to change and direct antimicrobial
use at a heath care institution.”1
A series of training programs have been developed to
enhance pharmacists’ knowledge and expertise in
providing antimicrobial stewardship at Kaiser
Permanente hospitals.
1 MacDougall C, Polk R. Antimicrobial Stewardship Programs in Health Care
Systems. Clin. Microbiol. Rev. Vol. 18 Oct 2005, p. 638-656
Antimicrobial Stewardship Training*
Part 1: Review of Basic Principles and Selected
Antimicrobials
Provides core background information in three
modules:
 Microbiology Lab review
 Antibiotic review
 Allergy review
See Notes
Module 1 (of 3): Microbiology Lab Review*
Goal
The goal of the Microbiology Lab
Review module is to review and
enhance pharmacists’ basic
understanding of microbiology in the
clinical setting.
 See Notes
Objectives
Upon completion of this module, the participant will be able
to:
1.
Differentiate between gram-positive and gram-negative
bacteria and name pertinent species from each group.
2.
Be able to interpret blood, urine, tissue and sputum
culture results.
3.
Define contamination and colonization.
4.
Explain the purpose of urinalysis.
5.
Be able to name some species of Coagulase-negative
Staphylococcus (CoNS) and explain the significance of
isolating CoNS from blood cultures.
Definitions *



Infectious Disease: “an interaction with a microbe that
causes damage to the host.”1
Pathogen: “any microorganism that has the capacity to
cause disease.”1
Virulence: properties that enable a microorganism to
establish itself on or within a host of a particular species
and enhance its potential to cause disease.
1. Mandell, Bennett, & Dolin: Principles and Practice of Infectious Diseases, 6th Ed.
See Notes
Definitions *

Microbiology results will be reported similar to this
Organism: Staphylococcus aureus
Drug
MIC
Result
Penicillin
>8
R
Ampicillin
>8
R
Oxacillin
<=0.25
S
Clindamycin
<=1
S
Tetracycline
<=1
S
<=0.5/9.5
S
Trimeth/sulfa
See Notes
Definitions

Susceptible (S): implies that an infection due to the isolate
may be appropriately treated with the dosage of
antimicrobial agent recommended for that type of
infection.


Only use an antibiotic that is reported as susceptible.
Intermediate (I): implies that an infection due to the
isolate may be appropriately treated in body sites where
the drugs are physiologically concentrated or when a high
dosage of drug can be used (i.e., urinary tract).
Definitions



Resistant (R): isolates that are not inhibited by the
usually achievable concentrations of the agent with
normal dosage schedules and/or fall in the range where
specific microbial resistance mechanisms are likely (e.g.,
β-lactamases).
Minimum inhibitory concentration (MIC): the lowest
concentration of the antimicrobial agent that prevents
visible growth after an incubation period.
Breakpoint: discriminatory antimicrobial concentration
used in the interpretation of results of susceptibility
testing to define isolates as susceptible, intermediate or
resistant. That is, the MIC where a bacteria goes from S
to either I or R.
Gram Stain *

Provides for rapid identification of
presumed pathogen
 Gram Positive (+) versus Gram
negative (-)
 Gives idea of morphology or
arrangement of bacteria
 cocci vs. rod
 cluster, pairs, chain
 Aids in selecting appropriate
empiric antibiotic choices
 Can be performed on any body fluid
 Only useful as preliminary guide – NOT definitive
See Notes
Gram Stain *
Application of series of dyes
that affix to the peptidoglycan
in bacterial cell wall:
Purple
 Gram Positive
Bacteria isolated and colored with Gram stain. Grampositive cocci, Staphylococcus aureus, from a lab culture.
Pink
 Gram Negative
Gram-negative bacilli with a capsule, Klebsiella
pneumoniae, from a pneumonia lung abscess (magnified
1,000×).
See Notes
Bacterial Morphology *


Shapes
 cocci = round
 bacilli = rods
 coccobacilli = ovoid
 fusiform = pointed-end
Arrangements
 single
 pairs
 clusters
 chains
See Notes
Microbiology: Common Pathogens *
Gram-Positive Cocci
 Clusters



Staphylococcus spp.
Pairs or chains

Streptococcus spp.

S. pneumoniae,
S. viridans
Enterococcus spp.
including
Other species:

Micrococcus spp.
Staphylococcus aureus
See Notes
Microbiology: Common Pathogens
Gram-Positive Bacilli (Rods)

Diphtheroids:



Large, with spores:



Clostridium spp (anaerobic)
Bacillus spp
Branching, beaded, rods:



Corynebacterium spp.
Proprionibacterium acnes
Nocardia spp.
Actinomyces spp.
Other


Listeria spp.
Lactobacillus spp. (vaginal
flora)
Clostridium difficile
Common Bacteria and
Classifications
Adapted from Jeff Kuper, Pharm.D., BCPS
See Notes
Microbiology: Common Pathogens
Gram-Negative Cocci
 Diplococci
Pairs:


Neisseria meningitidis
Neisseria gonorrhea
Neisseria gonorrhoeae

Other

Acinetobacter spp.
(technically a rod but can
appear as cocci or bacilli)
Acinetobacter baumannii
Microbiology: Common Pathogens *
Gram-Negative Bacilli (Rods)
 Lactose fermenters
Enterobacteriaceae (“enteric Gm -”)
 Serratia spp.
 Proteus spp.
 Enterobacter spp.
 Escherichia coli
 Citrobacter spp.
 Klebsiella spp.

Nonfermenters



Pseudomonas aeruginosa
Acinetobacter baumannii
Pseudomonas aeruginosa
Stenotrophomonas maltophilia
See Notes
Microbiology: Common Pathogens

Anaerobes
 Gm +


Clostridium spp.

Peptostreptococcus (cocci)
(rods/bacilli)
Gm 

Bacteroides spp.
(rods/bacilli)
 e.g. B. fragilis
Prevotella spp.
(rods/bacilli)
Clostridium difficile adhering to microvilli in the gut
Microbiology: Common Pathogens

Atypical bacteria



Mycoplasma pneumoniae
Legionella pneumophilia
Chlamydia pneumoniae


These bacteria are hard to
culture on standard media,
hence the name ‘atypical.’
Commonly implicated in
infections like communityacquired pneumonia (CAP).
Legionella pneumophilia
*Program Learning*
1.
2.
3.
What type of bacteria is Bacteroides fragilis?
How does the group of Enterobacteriaciae appear on
gram stain?
Name some atypical bacteria. What types of infections
do atypical bacterial cause?
*Program Learning Answers*
1.
2.
3.
What type of bacteria is Bacteroides fragilis?
An anaerobic gram-negative rod.
How does the group of Enterobacteraciae appear on
gram stain?
Gram-negative and appear pink.
Name some atypical bacteria. What types of infections
do atypical bacterial cause?
Legionella pneumophilia, Chlamydia pneumoniae,
Mycoplasma pneumoniae. These are mostly associated
with community-acquired pneumonia.
Colonization *

The presence of bacteria on a body surface
or mucous membrance without causing
disease/infection.
 Upper respiratory tract (URT) –



Strep. viridans, Candida spp
Skin – S. epidermidis, Corynebacterium
spp., S. aureus
GI tract – E. coli, K. pneumoniae,
Candida spp., Bacteroides spp.
Urogential – Lactobacillus (vaginal flora)
S. epidermidis. CDC.
See Notes
Colonization *

The presence of bacteria/organisms in a culture does not
necessarily mean they are pathogenic.
 It is up to the clinician to interpret the culture result
and clinically correlate to the patient’s signs and
symptoms.
See Notes
Colonization

The following are considered sterile sites and are not prone
to colonization:
 Blood
 Brain
 Muscle
 CSF
 Synovial fluid
Contamination


An organism that is introduced at some point during the
culturing process not related to or causing an infectious
process.
 Examples: Improperly prepped skin prior to
venipuncture, drawn from ‘dirty’ IV line, poor lab
technique  contamination on Petri dish).
Example: skin flora (S. epidermidis) being isolated in
blood cultures.
Blood Cultures *



Definitive means of identifying most likely pathogens.
 Most pathogens will grow within first 12–24 hours of
collection (Candida, anaerobes may take longer).
Incubated for five days by laboratory.
Should be taken PRIOR to initiation of antibiotics.
 Growth may be inhibited by antibiotics.
See Notes
Blood Cultures *

Common contaminants:
 Gm +cocci: Coagulase neg Staph (CoNS):

S. epidermidis, S. hominis, S.capitis, S. warneri
Gm + rods: Corynebacterium spp., Micrococcus
spp., Bacillus spp. (not anthracis)
See Notes
GPC in clusters
(GPCcl)
staphylococci
coagulase (+)
coagulase (-)
(CoNS)
S. aureus
S. epidermidis
others
Adapted from Jeff Kuper, Pharm.D., BCPS
See Notes
Blood Cultures

The following should NEVER be considered
contaminants:

Staphylococcus aureus

Gram – rods/bacilli

Candida spp.
Blood Cultures *
So what’s the significance of isolating a Coagulase
negative Staphylococcus spp. (CoNS) species from
blood cultures?
See Notes
Blood Cultures: Significance of CoNS

Assess how many blood cultures are positive vs. how
many were drawn.
 There should be a low suspicion for true infection if
only one blood culture from multiple sets drawn
around the same time period are positive for CoNS
 There should be a low suspicion if only one culture is
positive and cultures were drawn from separate sites
(e.g., one from IV line, one from peripheral site). See
next slide for more information.
Blood Cultures: Significance of CoNS *

What disease state/infection being treated?
 Patients with an indwelling central line, hemodialysis
catheter may be more at risk of infection.
 Patients with foreign material (especially cardiac),
bone/joint infections may have positive blood cultures
for CoNS.
See Notes
Blood Cultures: Significance of CoNS *


What constitutional symptoms does the patient have?
 Fever, leukocytosis
What type of patient?
 Immunocompetent
 Immunocompromised
 Chemotherapy/meds
 Disease state (advanced HIV)
 Transplant
 Neutropenic
See Notes
Blood Cultures: Significance of CoNS

In general, a solitary peripheral blood culture positive for
CoNS in an immunocompetent patient should be regarded
as a contaminant if:
 No other blood cultures drawn in a reasonable time
frame are also growing CoNS.
 The patient does not have prosthetic material present
or does not have a central line/catheter.
 If another source of infection is identified to account
for the patient’s constitutional symptoms.
 If patient has no signs or symptoms of infection.
Blood Cultures: Significance of CoNS
Just as in any clinical situation where the case is not
straightforward or there are questions:

If ever in doubt, present case to ID physician.
Urine Culture *




Urine samples are held for 24 hours by microbiology lab.
Bacterial growth expressed as colony counts, i.e.,
>100,000 colony forming units (CFU).
Should always have a corresponding urinalysis (UA)
performed for microscopy.
If >2 bacteria are isolated from a urine culture, the lab
will not perform any further work-up on the specimen.
See Notes
Urine Culture

Why perform a UA?
 The examination of fluid microscopy allows for some
differentiation between infection vs. colonization vs.
contamination.
 Infected fluid should have WBC, neutrophils or other
inflammatory markers.
 Uninfected fluids generally are devoid of these
markers.
 Keep in mind that immunocompromised patients
may not be able to mount a strong enough immune
response to produce these markers.
Urine Culture: Interpreting the UA



How many WBCs in urine?
How many epithelial/squamous cells present?
 The lower the number, the ‘cleaner’ the sample (i.e.,
you can probably trust culture result).
 The higher the number increases risk of
contamination with colonizing flora (i.e., sample
taken too early in the urine stream)
What amount of leukocyte esterase present?
 Given as trace, small, moderate and large.
 Found in certain WBC, sign of inflammation.
Tissue Culture


Preliminary report available at 24 hours, incubated for 72
hours total.
Lab will quantify growth of organism: rare, light,
moderate and heavy.
 Tissue sample is plated onto agar plate.
 Quantification of growth on plate gives some idea of
the bacterial burden of a sample.
Tissue Culture

These cultures can vary in quality:
 Some may be superficial samples (i.e., more prone to
contamination or colonization); others may be deep
tissue samples or cultures from an operation (i.e., less
likely to be contaminated or colonized).
 The presence of cellulitis, pus, exposed bone can help
distinguish true infection from contamination or
colonization.
 Read the MD note carefully and get some idea of
what the area looks like, whether the MD thinks the
area looks clinically infected or not.
Sputum Culture



Gram stain done initially by lab to assess quality of
specimen.
If > 10 epithelial cells, sample is not worked up:
 Sample not indicative of lower airway secretion.
 May be prone to contamination.
Patients with pulmonary infection should have purulent
sputum.
 Presence of WBC on gram stain.
*Program Learning*
1.
2.
3.
4.
Name some organisms that are commonly found on the
skin.
True or False: Coagulase positive Staphylococci
growing from a blood culture should be considered a
contaminant.
Which microbes may take longer to grow out in blood
cultures?
True or False: It is common for CSF and synovial fluid
to be colonized with bacteria.
*Program Learning Answers*
1.
2.
Name some organisms that are commonly found on the
skin:
S. epidermidis, S. aureus, Corynebacterium spp.
True or False: Coagulase positive Staphylococci
growing from a blood culture should be considered a
contaminant.
False: CoNS are usually contaminants. Staphylococcus
aureus is coagulase + and should never be considered
a contaminant when isolated from the blood.
*Program Learning Answers*
3.
Which microbes may take longer to grow out in blood
cultures?
Anaerobes and Candida spp. take longer to grow out in
blood cultures.
4.
True or False: It is common for CSF and synovial fluid
to be colonized with bacteria.
CSF and synovial fluid are considered sterile sites and
are not commonly colonized.
References



Mandell, Bennett & Dolin. Principles and Practice of Infectious
Disease. 7th ed. http://cl.kp.org (accessed Oct. 14, 2009).
Kaiser Permanente Laboratory Manual – Information - Northern
California. http://cl.kp.org (accessed Oct. 14, 2009).
Mermel, L. et al. Clinical Practice Guidelines for the Diagnosis and
Management of Intravascular catheter-related infection: 2009
Update by the Infectious Diseases Society of America. Clin Infect
Dis. 2009;49:1-45.
This concludes Module 1, the Microbiology Lab Review.
Please proceed to Modules 2 and 3.