Module 7: Antimicrobial Selection & Respiratory Infections Flashcards
Cu____e (24 hours)
- Most definitive method for diagnosis and treatment of an infection
- Sites tested determined by suspected site of infection (urine, blood, CSF, sputum, etc.)
- Provides initial identification of organism by gram stain, growth on selective media, presence or absences of enzymes, and chemical characteristics.
Culture
A G___ s____ is used to classify bacteria into Gram + or Gram - based on the organisms ability to retain stain (either purple/blue or red), indicating the makeup of it’s cell wall. The staining also allows for visualization of the organism and morphology (cocci, rods, etc). This is usually the first test performed on a culture of a potentially infectious site. It allows practitioners to streamline antibiotic therapy initially.
Gram stain
Regarding Gr__ st___s:
- It is essential to know organism morphology and what organism are “typically” associated with infections at a given site. With this information, antibiotic selection can be made based on susceptibility, location (can we achieve appropriate concentrations?) and patient factors.
- Eg. (see discussions) S. pneumoniae [Gm+ diplococci] and H. influenza [gm - coccobacilli] are pathogens typically associated with CAP.
Gram stain
Coloni______:
organisms do not invade the host but are part of the normal flora (Microorganisms that normally reside at a given site).
Colonization
Examples of col________n:
- The small and large intestine normal flora includes many organisms such as: lactobacillus, streptococcus, enterococcus, Enterobacteriaceae, Peptostreptococcus, Bacteroides and anaerobes.
- Staphylococcus species are common skin flora and are not found in the normal flora of the GI tract (so it’s presence there would be pathogenic)
- The presence of large numbers of epithelial cells (from the skin) would indicate contamination
Colonization
I________:
organisms invade the host and patient has s/Sx’s of infectious process
Infection
Cont_______:
the isolated organisms came from the patient’s skin or the environment.
Contamination
V________:
The ability of an agent of infection to produce disease. The v________ of a microorganism is a measure of the severity of the disease it causes.
virulence
Pathog_______ refers to the ability of an organism to cause disease (ie, harm the host). This ability represents a genetic component of the pathogen and the overt damage done to the host is a property of the host-pathogen interactions. Commensals and opportunistic pathogens lack this inherent ability to cause disease. However, disease is not an inevitable outcome of the host-pathogen interaction and, furthermore, pathogens can express a wide range of virulence.
Pathogenicity
V________, a term often used interchangeably with pathogenicity, refers to the degree of pathology caused by the organism. The extent of the this is usually correlated with the ability of the pathogen to multiply within the host and may be affected by other factors (ie, conditional). In summary, an organism (species or strain) is defined as being pathogenic (or not), and depending upon conditions, may exhibit different levels of this.
Virulence
Sensitivity of organism to antimicrobial agent
- M__: Lowest concentration of drug that will inhibit visible growth
- M__: Lowest concentration of drug that fails to show growth or results in 99.9% reduction of the initial inoculum
MIC
MBC
Antibacterial combinations:
- S______: Greater activity than the sum of activity of either agent alone
- A_________: Activity that is worse than either agent alone
- A______e/I_________t: Activity that is neither synergistic or antagonistic
Synergy
Antagonism
Additive/Indifferent
Post-antibiotic effect
- Persistent suppression of bacterial growth after brief exposure to the antibiotic
Post-antibiotic effect
“Time dependent killers”
- killing is dependent on the time an organism is in contact with the drug
“Time dependent killers”
“Concentration dependent killers”
- killing is dependent on the concentration of the drug that the organism is exposed to
“Concentration dependent killers”
Steps of bacterial infection:
- Bind: to electrochemically complementary tissue
- Colonize: exponential growth
- Produce: toxins and enzymes
Steps of bacterial infection
Mechanisms of bacterial res_______ (the ability of a microbe to resist the effects of medication previously used to treat them) causing antibiotics to be ineffective:
- Porin channels adapt to prevent drug entry
- Drug-metabolizing enzymes, e.g., beta-lactamases
- ATP driven P-glycoprotein efflux pumps
- Changes in drug binding proteins, e.g., for β-lactams
resistance
(Type of antibiotic treatment)
E______:
Initial broad antimicrobial spectrum before identification of the organisms directed against the organisms know to cause the infection in question based on patient’s presentation
Empiric
(Type of antibiotic treatment)
Def_______:
Antimicrobials selected based on clear identification of the organism(s) and proven sensitivity of the organism(s)
Definitive
(Type of antibiotic treatment)
Proph_______:
Antimicrobial directed against a single pathogen or multiple pathogens to prevent an infection from occurring. Usually short-term (before surgery, dental procedures) but can be long-term (AIDS).
Prophylactic:
Please be very familiar with the respiratory infections that were emphasized in the threads, readings and study guide [CAP, Aspiration pneumonia, AOM, and ABRS] as well as familiarity with symptom management (Table72-6).
Things to consider are causative organism, risk factors for infection, risk factors for MDR, treatment, consideration of the “whole” patient when selecting among the possible alternative possibilities, drug interactions, adverse effects and patient education
Just a reminder. Start digging into these things soon.
Most pneumonia arises following the a_________ of microorganisms from the oral cavity or nasopharynx. The term aspiration pneumonia should be reserved for pneumonitis resulting from the altered clearances. The pathogens that commonly produce pneumonia, such as Streptococcus pneumoniae, Haemophilus influenzae, gram-negative bacilli, and Staphylococcus aureus, are relatively virulent bacteria so that only a small inoculum is required and the a_________ is usually subtle. A true a_________ pneumonia, by convention, usually refers to an infection caused by less virulent bacteria, primarily anaerobes, which are common constituents of the normal flora in a susceptible host prone to aspiration [Am J Med. 2013 Nov;126(11):995-1001]
aspiration
Use of medications such as H2-receptor antagonists or proton-pump inhibitors may alter gastric pH allowing growth of potentially pathogenic organisms within gastric aspirations such that if aspiration occurs, it will more than likely be infectious in nature.
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A number of interventions (eg, positioning, dietary changes, drugs, oral hygiene, tube feeding) have been proposed to prevent aspiration, especially in older adult patients and stroke patients
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Treatment
For community acquired aspiration pneumonia consider treatment for both streptococci and anaerobes options include (dosing for adults with normal renal function)
- clindamycin 300 mg orally 4 times daily or 600 mg IV every 8 hours
- a beta-lactam/beta-lactamase inhibitor such as amoxicillin-clavulanate 875 mg orally twice daily or ampicillin-sulbactam 1.5-3 g IV every 6 hours
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For hospital-acquired aspiration pneumonia treatment should be based on suspected pathogens options, with anaerobic coverage, include (dosing for adults with normal renal function)
- piperacillin-tazobactam 4.5 g every 6 hours or ampicillin-sulbactam 1.5 g (1 g ampicillin/0.5 g sulbactam) to 3 g (2 g ampicillin/1 g sulbactam) every 6 hours
- an antipseudomonal carbapenem, such as meropenem 1 g every 8 hours
- an antipseudomonal cephalosporin, such as cefepime 1-2 g every 8-12 hours or ceftazidime 1 g every 8-12 hours PLUS metronidazole 500 mg IV every 8 hours or clindamycin 600 mg-2.7 g IV daily (in 2-4 equally divided doses)
- PLUS consideration of vancomycin 15 mg/kg every 12 hours (adjusted to troughs of 15-20 mcg/mL) or linezolid if MRSA is suspect
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HAP/VAP/HCAP
Hospital-acquired (or nosocomial) pneumonia (HAP) is pneumonia that occurs 48 hours or more after admission and did not appear to be incubating at the time of admission.
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Ventilator-associated pneumonia (VAP) is a type of HAP that develops more than 48 to 72 hours after endotrachael intubation.
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Healthcare-associated pneumonia (HCAP) is defined as pneumonia that occurs in a non hospitalized patient with extensive healthcare contact, as defined by one or more of the following:
- Intravenous therapy, wound care, or intravenous chemotherapy within the prior 30 days
- Residence in a nursing home or other long-term care facility
- Hospitalization in an acute care hospital for two or more days within the prior 90 days
- Attendance at a hospital or hemodialysis clinic within the prior 30 days
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Multi-drug resistance (MDR) becomes important concern:
In critically ill patients, in those receiving antibiotics prior to the onset of pneumonia and in institutions where these pathogens are frequent .. coverage of methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa, and antibiotic-resistant gram-negative bacilli such as Acinetobacter spp and Legionella should be considered.
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Treatment of HCAP:
Early onset ≤ 5 days - S pneumonia, H influenzae MSSA, Gm- bacilli: 3rd generation cephalosporin, respiratory quinolone, amp/sulb OR ertapenem
- Late onset or risk of MDR organisms - P aeruginosa, ESBL k pneumonia, Acinobacter spp and MRSA: 4th gen cephalosporin, carbapenem,blactam/blactam inhibitor, respiratory quinolones +/- AMGs.
- Table 71-4
- If MRSA is concern- add vanco or linezolid to above
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CAP (community acquired pneumonia)
- An acute infection of the pulmonary parenchyma in a patient who has acquired the infection in the community
- The predominant pathogen is Streptococcus pneumoniae (See Key Concept pp1091). Other common pathogens include Haemophilus influenzae, Moraxella catarrhalis, the atypical bacteria (Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella spp) and respiratory viruses.
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Antibiotic therapy is typically begun on an empiric basis, since the causative organism is not identified in an appreciable proportion of patients. NOTE SITUATIONS WHERE DOUBLE COVERAGE (+) IS WARRANTED
- Adult outpatient w/o comorbidities; no ABs in past 3 months - amoxicillin (High Dose), doxycycline OR macrolides If local rates of macrolide-resistant Strep. pneumoniae < 25%.
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Antibiotic therapy is typically begun on an empiric basis, since the causative organism is not identified in an appreciable proportion of patients. NOTE SITUATIONS WHERE DOUBLE COVERAGE (+) IS WARRANTED
Adult outpatient w/ comorbidities OR AB use in past 3 months - respiratory quinolone (eg. levofloxacin, moxifloxacin) OR high dose amoxicillin or amox.tr-clv PLUS macrolide (eg azithromycin, clarithromycin) OR high dose amoxicillin or amox.tr-clv PLUS doxycycline
Comorbidities of concern:
- Alcoholism: Strep. pneumoniae, H. influenzae
- COPD: H. influenzae, M. catarrhalis, Strep. pneumoniae
- Post CVA-aspiration: Oral flora, Strep. pneumoniae
- Post-obstruction of bronchi: Strep. pneumoniae, anaerobes
- Post-influenza: Strep. pneumoniae, Staph. aureus
- Neutropenia, immunocompromised host: Pseudomonas aeruginosa
- Injection drug use: Staph. aureus (MRSA and MSSA)
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Adult inpatient (not ICU)- respiratory quinolone (eg. levofloxacin, moxifloxacin) OR 3rd gen cephalosporin or ertapenem PLUS macrolide or doxy.
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Adult inpatient (ICU, no pseudomonas) - 3rd gen cephalosporin PLUS azithromycin or respiratory quinolone
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Adult inpatient (ICU, pseudomonas) - cefepime or ceftazidime, or piperac/tazob, or imipenem, or meropenem + quinolone or AMG. If AMG add azithromycin or quinolone.
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If CA-MRSA is a concern: add vanco or linezolid or (if susceptible) clindamycin to above.
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Vaccinations
CDC recommendations on pneumococcal vaccination13-valent pneumococcal conjugate vaccine (PCV13) recommended for:
- all children aged 2-59 months
- persons aged > 5 years with medical conditions associated with increased risk of pneumococcal disease or complications
- recommended dosing schedule varies with patient age and immune status
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Vaccinations
23-valent pneumococcal vaccine (Pneumovax, PPSV23) recommended for
- all persons aged ≥ 65 years
- persons aged 19-64 years with chronic illness, asplenia, immunocompromised, or persons who smoke
- children ≥ 2 years old with underlying medical conditions (administration varies with previous vaccination status and medical status)
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Vaccinations
CDC recommends annual influenza vaccination for everyone 6 months and older with any licensed, age-appropriate flu vaccine (IIV, RIV4, or LAIV4) with no preference expressed for any one vaccine over another.
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URI
For most people colds are viral and symptoms are self-limited
Options: Table 72-6
- OTCs?? (analgesics/antipyretics, saline nasal irrigation, nasal glucocorticoids, oral/ nasal decongestants, mucolytic, antihistamines, etc
- Precautions?
- Limitations?
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AOM (Acute Otitis Media)
Presence of middle ear fluid and inflammation of the mucosa that lines the middle ear space
- S. pneumoniae is the most important bacterial cause of AOM, but can include others such as H influenza, M catarrhalis
- Risk factors - Table 72-1
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It is important to make an accurate diagnosis of AOM to avoid the inappropriate use of antibiotics and the associated increase in antibiotic-resistance rates.
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The choice of strategy for treating AOM depends upon the age of the child, the severity of illness, and parental preference
- If observation option is used, mechanism must be in place to ensure follow-up and begin antibiotic therapy if child worsens or fails to improve within 48-72 hours of onset of symptoms
- When decision to treat AOM with antibiotics has been made, reassess patient if caregiver reports symptoms have worsened or failed to respond to initial antibiotic therapy within 48-72 hours
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Amo________ is the drug of choice in most patients for AOM (Acute Otitis Media).
Amoxicillin
Treatment for AOM (Acute Otitis Media):
High dose amoxicillin
- amoxicillin recommended if child has not received amoxicillin in past 30 days, does not have concurrent purulent conjunctivitis, and is not allergic to penicillin.
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Treatment for AOM (Acute Otitis Media):
Amox/tr-clv
- antibiotic with additional beta-lactamase coverage (amoxicillin-clavulanate) is recommended if child has received amoxicillin in past 30 days, has concurrent purulent conjunctivitis, or has history of recurrent AOM unresponsive to amoxicillin.
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Treatment for AOM (Acute Otitis Media):
Cefuroxime, cefpodoxime or cefdinir (14mg/kg/d child)
- Reasonable with Mild hypersensitivity reactions.
- Mild delayed hypersensitivity reactions (Type II, II, Iv) to penicillin appear after more than one dose, typically after days of treatment. They lack features of immunoglobulin E (IgE)-mediated reaction (e.g., anaphylaxis, angioedema, bronchospasm, urticaria) and serious/life-threatening delayed drug reactions.
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Treatment for AOM (Acute Otitis Media):
ALT - macrolide, clindamycin OR smz/tmp
- Reasonable alternatives with anaphylaxis or IgE mediated reaction to penicillin / cephalosporin
- Immediate reactions (Type I) to penicillin classically begin within one hour of the initial or last-administered dose and have features of IgE-mediated reaction (e.g., anaphylaxis, angioedema, bronchospasm, urticaria) or Serious delayed reactions.
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Treatment for AOM (Acute Otitis Media):
Adjunctive therapies / Pain management
- Pain is a common feature of AOM and may be severe. Treatment to reduce ear pain in children with AOM whether or not they are treated with antibiotics is recommended
- oral analgesics such as acetaminophen or ibuprofen
- topical anesthetics - Most, if not all have been withdrawn from the market in the United States because they have not been evaluated by the US Food and Drug Administration for safety, effectiveness, and quality
- Decongestants and antihistamines - Studies suggest lack of benefit and a potential for delayed resolution of middle ear fluid
- external application of heat or cold, instillation of olive oil or herbal extracts - clinical conclusions regarding use is limited due to lack of supporting evidence
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AOM (URI)
Caused by: H influenzae, s pneumoniae, m catarrhalis.
Treated with:
- High dose amoxicillin (90mg/kg/d child)[i]
- Amox/tr-clv if coverage for lactamase producing bacteria is necessary [ii]
- Cefuroxime, cefpodoxime or cefdinir(14mg/kg/d)
- ALT - macrolide, clindamycin or smz/tmp[iii]
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Sinusitis
- Acute rhinosinusitis (ARS) is defined as symptomatic inflammation of the nasal cavity and paranasal sinuses lasting less than four weeks. The term “rhinosinusitis” is preferred to “sinusitis” since inflammation of the sinuses rarely occurs without concurrent inflammation of the nasal mucosa
- Risk factors for ARBS - table72-3
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In addition to supportive care, options for the outpatient management of uncomplicated acute bacterial rhinosinusitis (ABRS) are observation or antibiotics depending on patient follow-up.
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