ID juju Flashcards
What are infectious agents?
•Viruses •Bacteria •Fungi •Protozoans •Helminths
What are situations in which infections can occur?
- Organ system specific
- Immunosuppressed ( HIV, Neutropenic)
- post abx use: C. diff
- Diabetes: pseudomonsa MC
- Sickle Cell Disease: salmonella (any encapsulated), splenomegaly
- Prosthetic Devices: foreign device with no defense mechanism.( endocarditis
- S. aureus)
- Travel
MC bacterial infection
pseudomonas
What is a direct stain?
Prep smear of specimen +staining to detect microorganisms.
- ex: Gram Stain
What is the gram stain process?
Patient specimen is applied to glass slide, dried + fixed Slide is subjected to 2 stains
- Gram positive stain purple
- Gram negative stain red
- Nonbacterial, WBC= stain characteristic of cell type Color, shape and arrangement are described in microscopic analysis “Gram positive cocci in clusters”
What are the 4 steps in the process to end up with purple/red staining?
Crystal Violet Iodine Alcohol Safranin
What are some examples of gram positive bacteria?
Gram +:
- S. pneumoniae
- S. Aureus
- P. Aerguinosa
- S.Pyrogens
- C.botulinum
- C.Diptheria
—— Gram
-:
- N. Meningitis
- H.Pylori
- E.coli
- T.palladium
- V.cholerae
- N. gonorrhoea
What are some examples of gram negative bacteria?
Gram
-:
- N. Meningitis
- H.Pylori
- E.coli
- T.palladium
- V.cholerae
- N. gonorrhoea
—– Gram +:
- S. pneumoniae
- S. Aureus
- P. Aerguinosa
- S.Pyrogens
- C.botulinum
- C.Diptheria
What is the gold standard for growing a bacteria?
Culture: isolation of the pure organism
-Definitive identification & antimicrobial sensitivity
- MIC: minimum inhibitory concentration
- moderate to high expense Sample Collection → growth of organisms (aerobic or anaerobic) → isolation of organisms → Identification
What are types of sample collection for culture?
Liquid: body fluids (except not blood!) Solid/semisolid: Sputum, stool, tissue Swab: from infected site like a wound
Culture: process
Sample Collection → growth of organisms (aerobic or anaerobic) → isolation of organisms → Identification
- 1-3 days: longer
-gold standard isolation of the PURE ORGANISM
-definitive identification and antimicrobial susceptibility
-typical bacteria
-MIC, minimum inhibitory concentration- minimum dose that will kill
-gives you more than telling you if its gram + and
-
-lets you know if bacteria is resistant to antibiotics (MRSA)
-tells you at what dose/concentration the antibiotic will kill the bacteria
What is antigen detection?
- antigens: surface proteins detected with immunofluorescence in microscopic examination
- do not require growing the organism
- immunoasssays that detect soluble antigens
- immunoassays that detect the organism by its reaction to a reagent antibodies
- moderate expense
- manual with microscopic evaluation + fuorescent microscope
Nucleic Acid Detection
•detects the RNA of the infectious agent
- Valuable to detecting difficult to grow or slow growing organisms •HIV viral load •Only looks for that specific organism
- 1-2 hrs: no delay, FAST
- bacteria or viral
What is the issue with nucleic acid testing?
Viral particles can remain in system.You may have recovered and still positive ,you can have partially destroyed viral products in organ system (for ex, covid like 90 days)
What does serology detect?
Detect host *antibodies * that are produced in response to infections
- Immune markers
- syphillis
- see what antibodies are present in response to a disease to dx
- orange/red/fuschia: no antibodies
- yellow/any color change: + antibodies
How is syphillis tested?
Serology
MC types of infections that lead to sepsis
MC:
- skin
- lungs
- GI tract
- urinary tract sepsis: infection you have triggers a chain reaction throughout your body
How do you go about working up an infectious agent?
- List clinical signs /symptoms to identify specific organs and tissues likely to be infected 2. Collect appropriate samples + order appropriate tests to detect the most likely infectious agents (ex: gram stain, bacterial culture) 3. Empiric tx to protect against most likely pathogens 4. When lab identifies organism (s), they preform tests for antibiotic susceptibilities (BACTERIAL ONLY usually) and modify tx necessary to target pathogenic organism (s)
What is SIRS Criteria
Initial infection and 2+ OF THE FOLLOWING:
- Temp > 38 C or
- HR> 90 Bpm
- RR>20 Bpm
- WBC> 12,000 or
What is SEPSIS Criteria
Systemic response to infection
- SIRS AND
- Documented/ highly suspected infection
What is Severe Sepsis criteria?
Sepsis + evidence of organ dysfunction, hypo perfusion or hypotension
What is Septic Shock criteria?
Sepsis induced hypotension:
- systolic BP <90 , despite fluid resuscitation
- evidence of Organ dysfunction, hypo perfusion, or hypotension requires immediate medical attention
Symptoms + tx of septic shock
- Low BP (<90)
- pale and cool arms and legs
- chills
- difficulty breathing
- decreased urine output (vasodilation)
- Mental confusion and disorientation requires immediate medical attention tx:
- supplemental O2
- IV fluids
- abx
Bacteremia
•Blood should be sterile •Infections in organ or tissue can introduce bacteria to the blood stream •can lead to sepsis dx: •Blood culture: 4 bottles/vials total •Skin prep to eliminate skin microorganisms before venipuncture
- 2 samples taken at two different sites
- one aerobic set and one anaerobic set
What is a blood culture?
Lab test used to detect bacteria or fungi in a person’s blood.
-detect their presence by co2 production
- Skin prep to eliminate skin microorganisms before venipuncture
- 2 samples taken at two different sites
- one aerobic set and one anaerobic set positive blood culture: growth of microorganism generating CO2
The presence of microorganisms can indicate
a bloodstream infection such as bacteremia or fungemia, which in severe cases may result in sepsis.
Antimicrobial sensitivity tests are used to determine
Which abx are likely to effectively eliminate an infectious organism by exposing the organism to diff abx in vitro
- dilution method
- disc diffusion method
What diseases involved in tick transmission?
Lymes, Rickettsia/RMSF, Ehrlichia, Anaplasma
What testing is performed for ticks?
PCR and Serological Testing Lyme:
- two
-step testing RMSF:
- rash with endothelial vasculitis
- serological test Ehrlichia:
- lone start tick
- Nucleic acid amplification test Anaplasma:
- deer tick
- Nucleic acid amplification test
RMSF testing
RMSF:
- rash with endothelial vasculitis
- serological test Ehrlichia:
- lone start tick
- Nucleic acid amplification test Anaplasma:
- deer tick
- Nucleic acid amplification test
Ehrlichia what kind of tick and test?
Lone star tick. Nucleic acid amplification test.
Anaplasma, what kind of tick and test?
Deer tick. Nucleic acid amplification test.
Lyme Disease Testing Process
Two tier testing First tier: enzyme immunassay or Immunofluorescence assay
- detects antibodies produced by the body in response to infection
- positive/equivocal (unclear) = confirmatory testing
- negative: no further tests Second tier: confirmatory test:
- analyzes the blood for antibodies specific to different components (proteins) of the Borrelia burgdorferi bacteria
- sx for over 30 days: IgG western blot ONLY
- sx for less than or equal to 30 days: IgM and IgG western blot
- positive results = pt is positive for lyme ds
lyme ds: EIAs first tier vs second tier
First tier EIAs:
- Borrelia antigens
- distinguish between IgM and IgG class antibodies
- IgM = early/recent exposure
- if negative: no further testing second tier EIAs:
- detects total antibodies without differentiating between the antibody classes.
- if second tier EIAs are positive, the final patient result is considered positive
What is fungemia + causes
Candida normal flora in oral and GI tract causes:
- Steroid inhalers
- Nasal steroids– flonase
- Abx therapy
- Neutropenia
- Pts w indwelling lines
Transmission cycle of Plasmodium (Malaria)
- A bite from an infected mosquito 2. parasites travel to liver where they lie dormant for 10 days- 4 weeks 3. parasites leave liver and infect RBCs, then malaria signs and symptoms 4. new mosquito bite you and becomes infected
What patient would present with Plasmodium (malaria)? What kind of smear can you see the malaria on ?
Traveler with febrile illness
- RBC smears
How is babesiosis transmitted?
Tick transmission Infects RBC
babesiosis: sx and tx
Tick transmission Sx:
- infects RBCs
-> Hemolysis
- fever
- anorexia
- headache tx:
- self limited
viral blood infections
- mono/Epstein barr virus
- cytomegalovirus
- parvovirus B19
Mononucleosis / Epstein Barr Virus symptoms + testing
sx:
- Fever
- sore throat
- enlarged cervical lymph nodes testing:
- antibody test
- monospot
What is cytomegalovirus and who does it affect?
- Opportunistic infection in transplant or AIDS
- Fever
- affects Immunocompromised and Infants
Parvovirus B19- Fifths disease is transmitted via
Respiratory droplets
What does parvovirus cause?
- Slapcheek
- Aplastic crisis in those with chronic hemolytic anemia.
Lumbar Puncture is essential/extremely useful in the diagnosis of
Bacterial, fungal, mycobacterial, and viral central nervous system (CNS) infections and, subarachnoid hemorrhage (SAH), CNS malignancies, demyelinating diseases, and Guillain-Barré syndrome.
Lumbar Puncture Normal Measurements -Opening Pressure -Appearance -Protein -Glucose -Gram Stain -Glucose CSF: Serum Ratio -White Cell Count
-Opening Pressure: 7-18
-Appearance: Clear , colorless
-Protein: 23-38
-Glucose: 2/3 serum glucose
-Gram Stain: Negative
-Glucose CSF: Serum Ratio: 0.6
-White Cell Count: <5 cells
Lumbar Puncture Bacterial Measurements -Opening Pressure -Appearance -Protein -Glucose -Gram Stain -Glucose CSF: Serum Ratio -White Cell Count
-Opening Pressure : >30 (increased)
-Appearance: Turbid
-Protein: Increased
-Glucose: Decreased
-Gram Stain: Positive
-Glucose CSF: Serum Ratio: <0.4
-White Cell Count: Neutrophils
Lumbar Puncture Viral Measurements -Opening Pressure -Appearance -Protein -Glucose -Gram Stain -Glucose CSF: Serum Ratio -White Cell Count
-Opening Pressure: Normal (7-18) or mild increase
-Appearance: Clear
-Protein: Normal/ decreased
-Glucose: Normal
-Gram Stain: Negative
-Glucose CSF: Serum Ratio: > 0.6
-White Cell Count: Lymphocytes
Lumbar Puncture SAH Measurements -Opening Pressure -Appearance -Protein -Glucose -Gram Stain -Glucose CSF: Serum Ratio -White Cell Count
-Opening Pressure: Increased
-Appearance: Grossly bloody, Xanthrochromic or clear
-Protein: Increased
-Glucose: Normal
-Gram Stain: Negative
-Glucose CSF: Serum Ratio: 0.6
-White Cell Count: May increase d/t bleeding
Osteomyelitis: What is S.aureus population at risk?
All ages– infants & children Most frequent organism causing hematogenous osteomyelitis
Osteomyelitis: What is salmonella spp. population at risk?
Sickle cell pts, immunocompromised
Osteomyelitis: What is pseudomonas population at risk?
Iv drug abusers, puncture wound, urinary catheters
Osteomyelitis: Aerobic, gram negative (enterobacter and proteus)
UTIs, diabetic foot infections, vascular insufficiency
Osteomyelitis: Aerobic streptococci and anaerobe streptococci
aerobic:
- Patients with bites, diabetic foot lesions, or vascular insufficiency anaerobic:
- Patients with foreign body associated infections
- prosthetic joints (chronic infection), bites, diabetic foot lesions or decubitus ulcers
Osteomyelitis: fungal species
- Patients with catheter-related fungemia
- IV drug abusers
- immunocompromised individuals ( low T cell counts)
Joint Infections what kind of gram stain? What else?
- Synovial fluid gram stain
- Culture for organism
- Microscopy for crystals (Gout, Arthritis- big toe)
Impetigo: what is it
Vesicles honey colored crust on epidermis S. aureus, S. Pyogenes
What is Erysipelas ? tx
Erythematous, painful with sharply demarcated RAISED regular border, superficial dermis S. pyogenes, s. agalactiae tx:
- cephalexin , cefazolin
What is cellulitis?
Erythematous diffuse FLAT lesion, irregular border deep dermis S. pyogenes, streptococcus. agalactiae, s. aureus
What is folliculitis ?
Localized inflamed papules w pus hair follicle S. aureus, P.aerguinosa (hot tubs)
—– tx:
- warm moist compress
Skin Abscess( furuncle )overview
Raised tender inflamed nodule w central region of purulence
- pus area is initially firm
-> becomes fluctuant S. aureus
- affects the deep dermis tx:
- Incision and drainage (gold standard)
- abx directed at s. aureus
Necrotizing soft tissue fasciitis
Very painful area of inflammation w rapid progression to bullae purpura anesthesia and systemic toxicity
- affects fascia and muscle, + local blood vessels and nerves
- monomicrobial or polymicrobial form Tx:
- surgical debridement
- broad spectrum systemic abx
Cat- Scratch Disease- Bartonella is typically characterized by
Self-limited regional lymphadenopathy.
- visceral organ, neurologic, and ocular involvement
- bartonella henselae
- dx: lymph node bx, serology testing, PCR
Tinea Faciei
Itchy spots on cheeks Raised Bumps, blisters or scabs
Tinea Capitis
Round itchy scaly, similar to dandruff, bald spots due to hair loss, kerion, favus=severe
Tinea Manuum
Blistering rashes w sticky fluid on hands, skin discoloration
Tinea Cruris
Itchy reddish brown rashes on groin can spread to buttocks
Tinea Pedis
Round dry patches on top of foot, cluster of blisters on side of foot, moist peeling in between toes, dry but not inflamed
Tinea Incognito
Any ringworm affected area may develop this
- Bruised and broken blood vessels
- raised and scaly rashes
- skin is more pustular and irritable
Tinea Unguium
White/yellow streaks on toe fingernails Nail can lift or become damaged
Tinea Corporis
On torso, body, legs more prominent in body folds, kerion may develop
Tinea Barbae
Facial hair area
-crusting and swelling, facial hair easily pulled out
Varicella- Chicken Pox is characterized by
Vesicular rash predominately trunk, scalp & face •Remains in sensory ganglia, later presenting as herpes zoster Less common due to increased vaccination ( 1 year of age) “Tear drops on a rose petal” PNA ( severe cases) Serologic testing for immunity
What can varicella cause in immunocompromised?
PNA
What testing for varicella?
Serologic testing for immunity
Measles (Rubeola) is a highly contagious characterized by
High Fever & rash of tiny red spots
- 14 days post exposure: diffuse rash
- kolpik spots: white little spots inside the mouth Spreads through air
-> respiratory system ds
- through contact w infected mucus and saliva Can get secondary bacterial PNA and Encephalitis**
How many days post exposure will patients with measles develop a diffuse rash
14 days
Rubella ( German Measles) is a mild illness characterized by
- fever + Rash and enlarged lymph nodes
- Eye anomalities: cataracts, glaucoma, nystagmus, iris dysplasia, microphtalmia
- congenital defects if fetus is exposed
-> more serious in pregnant women (mild in kids) - Acquired via inhalation of infectious large particle aerosols and close and prolonged contact with infected individuals
-incubation: ~14-18 days - 2004: officially eliminated from US
Rubella incubation?
14-18 days
What can occur if fetus exposed to rubella?
◦Congenital defects
-microcephaly, heart disease, peticheae +purpura
Measels vs Rubella
MEASLES:
-rubeola
-viral
-respiratory
-contagious through mucus and saliva RUBELLA:
-contagious
-mostly children
-rash, fever, eye redness
-mild in kids
-serious in pregnant women
-> microcephaly congenital defects
GI bacterial infections: incubation period, duration, signs
stool test
GI acute viral gastroenteritis
rotavirus and norovirus: cruise ships fecal oral route
What are protozoan infections of GI tract? Treat with what?
Amoebiasis + Giardiasis: Tx metronidazole/ tinidazole Cryptosporidiosis: tx azithromycin, nitazoxanide Cyclosporiasis: tx Bactrim dx: Stool O&P exam
Helminth
◦Tapeworms (cestodes) ◦Roundworms (nematodes) ◦Flukes (trematodes)
Diagnosis of helminth with
Detection of larvae or eggs in stool.
Botulism description + sx
Rare neuroparalytic syndrome due to neurotoxin from bacteria Clostridium botulinum
- blocks release of acetylcholine at peripheral cholinergic synapses sx:
- symmetric descending weakness and paralysis to diaphragm
With botulism what is blocked?
Blocks the release of acetylcholine at peripheral cholinergic synapses.
What is food contamination for botulism
◦Canned food ◦Honey containing spores
- do not give kids under 2 honey
How do you test for botulism?
Test for toxin in serum or stool
Salmonella: incubation, druation, signs
Salmonella → eggs, undercooked chicken, reptiles (turtles)** Incubation: 6-48 h Duration: 1-7 days Signs:
- n/v/d
- abdominal pain
- fever
- +/- blood
Amoebiasis
- midl diarrhea
- severe dysentery
- can cause severe dysentery and colitis
- abscess on the liver fecal oral route: ingestion of cysts from contaminated water sources Dx: stool O&P exam
