antimicrobial stewardship training this course is accepted by the california state board of pharmacy...
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Antimicrobial Stewardship Training
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
Part 1: Review of Basic Principles and Selected
Antimicrobials
By Keith Teelucksingh, PharmD Infectious Disease Pharmacist, Kaiser Permanente Vallejo
With contributions by Linh Van, PharmDInfectious Disease Pharmacist, Kaiser Permanente Oakland
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*
GoalThe 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
Trimeth/sulfa <=0.5/9.5 S
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
Pink Gram Negative
Bacteria isolated and colored with Gram stain. Gram-positive cocci, Staphylococcus aureus, from a lab culture.
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. including S. pneumoniae, S. viridans
Enterococcus spp. Other species:
Micrococcus spp.Staphylococcus aureus
See Notes
Gram-Positive Bacilli (Rods) Diphtheroids:
Corynebacterium spp. Proprionibacterium acnes
Large, with spores: Clostridium spp
(anaerobic) Bacillus spp
Branching, beaded, rods: Nocardia spp. Actinomyces spp.
Other Listeria spp. Lactobacillus spp. (vaginal
flora)
Microbiology: Common Pathogens
Clostridium difficile
Gram-Negative Cocci Diplococci
Pairs: Neisseria meningitidis Neisseria gonorrhea
Other Acinetobacter spp.
(technically a rod but can appear as cocci or bacilli)
Microbiology: Common Pathogens
Neisseria gonorrhoeae
Acinetobacter baumannii
Gram-Negative Bacilli (Rods) Lactose fermentersEnterobacteriaceae (“enteric Gm -”)
Serratia spp. Proteus spp. Enterobacter spp. Escherichia coli Citrobacter spp. Klebsiella spp.
Nonfermenters Acinetobacter baumannii Pseudomonas aeruginosa Stenotrophomonas
maltophilia
Microbiology: Common Pathogens *
Pseudomonas aeruginosa
See Notes
Microbiology: Common Pathogens
Anaerobes Gm +
Clostridium spp. (rods/bacilli)
Peptostreptococcus (cocci)
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 community-acquired pneumonia (CAP).
Legionella pneumophilia
*Program Learning*
1. What type of bacteria is Bacteroides fragilis?2. How does the group of Enterobacteriaciae
appear on gram stain?3. Name some atypical bacteria. What types of
infections do atypical bacterial cause?
*Program Learning Answers*
1. What type of bacteria is Bacteroides fragilis? An anaerobic gram-negative rod.
2. How does the group of Enterobacteraciae appear on gram stain? Gram-negative and appear pink.
3. 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. aureusS. epidermidis
others
GPC in clusters(GPCcl)
staphylococci
coagulase (+)coagulase (-)
(CoNS)
S. aureusS. 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
If ever in doubt, present case to ID physician.
Just as in any clinical situation where the case is not straightforward or there are questions:
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. Name some organisms that are commonly found on the skin.
2. True or False: Coagulase positive Staphylococci growing from a blood culture should be considered a contaminant.
3. Which microbes may 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.
*Program Learning Answers*
1. Name some organisms that are commonly found on the skin: S. epidermidis, S. aureus, Corynebacterium spp.
2. 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.