Infectious Disease Process (22 questions) Flashcards
24 Exam questions
Characteristics of bacteria
Free-living; single celled organisms; multiply through replication and cellular division; contain DNA, ribosomes, membrane and cell wall
What bacteria/organisms can penetrate the epithelium of the conjunctiva or cornea?
Neisseria gonorrhoeae, Neisseria meningitidis, Streptococcus pneumoniae, Listeria monocytogenes, Corynebacterium Diphtheriae.
For all others, a breach in the protective epithelial barrier or mucous membranes must occur.
What specimens are not appropriate for anaerobic cultures
Anaerobes are commonly found on
mucous membranes and other sites such as the vagina and oral cavity.
Therefore, specimens likely to be contaminated with these organisms
should not be submitted for culture.
Sputum
Rectal swab
Nasal or throat culture
Urethral swab
Voided urine
Anaerobic culture should be used for:Blood, transtracheal aspirate, spinal fluid
What is Virulence
Ability to invade and create disease in a host. Ability to grow and multiply.
1st element virulence
ability of organism to survive in external environment during transit between hosts
2nd element virulence
mechanisms for transmission to new host
Antigen
Any substance that the immune system can recognize and can thus stimulate an immune response
Antibody
(Immunoglobulin) protein that is produced by B cells that tightly bind to the antigen of an invader, tagging the invader for attack or directly neutralizing it
T cell (T lymphocyte)
A white blood cell that is involved in acquired immunity and that may be one of three types: helper, killer (cytotoxic), or regulatory.
B cell (B lymphocyte)
a WBC that produces antibodies specific to the antigen that stimulated their production
What is a neutrophil
First to arrive at the site of an infection
most abundant phagocyte
they inhibit the growth of bacteria or fungus
quickly enter tissues and phagocytize pathogens- phagocytosis (engulf and ingest particles of nutrients or bacteria)
bands = immature WBC (elevated in serious infection)
Monocytes
Largest Leucocyte (WBC)
cells of chronic inflammation, “late comers” to infection
Mast cells
Located in connective tissue and mucous membranes
When activated Excrete histamine and heparin
Histamine dilates blood vessels and causes neutrophils and macrophages to the site (characteristic signs of inflammation)
A cell in tissues that releases histamine and other substances involved in inflammatory and allergic reactions.
Lymphocyte
WBC responsible for acquired (specific) immunity, including producing antibodies (by B cells), distinguishing self from oneself (by T cells), and killing infected cells and cancer cells (by killer T cells).
Leukocyte
WBC such as a monocyte, neutrophil, eosinophil, basophil or a lymphocyte (B cell or T cell)
What is an eosinophil
WBC - Active and killing bacteria and parasites
they also can cause tissue damage during allergic reaction. Important in hypersensitivity rxn.
Cytokines
Proteins that are secreted by immune and other cells that acts as the immune systems messendgers to help regulate an immune response
What is the basophil
WBC activated by pathogen and releases histamine (substance involved in allergic rxn)
Produces substances that attract other WBC (neutrophils and eosinophils) to a trouble spot
important defense against parasites
Play a role in allergic reactions (such as cause asthma)
Co- infection for Hep B
Hepatitis D. Only occurs among people infected with Hep B. Uncommon in US. Transmitted through contact with infectious blood.
HIV/AIDS
affects CD4 cells or T cells, compromising immune system to fight off infection
*Transmission: body fluids (most commonly during unprotected sex)
*no cure, tx with antiretroviral improves survival
* prevention= standard precautions, risk reduction, med adherence
HIV/AIDS exposure
Western Blot detects antibody 1-3 months after exposure.
Incubation: 1-3 months
ELISA positive 3 weeks to 6 months (rare) after exposure are rare.
Hepatitis D
Co-infection with Hepatitis B Incubation: 2-8 weeks Transmission bloodborne not usually sexual Standard Precautions
Influenza
*Incubation 1-4 days (avg 2), shed day prior sx onset through 5-10 days.
* Influenza A= predominant cause epidemic. Influenza B also causes epidemics but clinical illness is usually milder.
*Droplet Precautions (includes eye protection) for 7 days after illness onset or 24 hours after the resolution of fever and respiratory symptoms, whichever is longer. extended for children and immunocompromised patients who might shed virus for longer periods. AGP’s: N95 and AIIR (if available)
because droplets do not remain suspended in the air and generally travel only
a short distance (≤1 meter) through the air. Contact with respiratory-droplet
contaminated surfaces is another possible source of transmission.
In recent years, influenza A and B
strains also have been named according to the city or state and year of their
initial isolation, for example, A/Texas/36/91 (H1N1) or B/Hong Kong/330/2001.
Lyme Disease
Borrelia burgdorferi. Incubation 3-30 days after tick bite.
characteristic skin rash
called erythema migrans (annular lesions that burns and itches)
Standard Precautions. Most common New England, Mid Atlantic, Upper Midwest and northern Cali
Bacterial Meningitis
CLOUDY CSF, increase WBC, increased protein, decrease glucose.
Determined based off of exam of CSF.
Appearance is cloudy- presence of significant concentration of WBC’s, RBC’s bacteria and/or protein.
WBC is increased if untreated bacterial meningitis.
Meningitis
Meningococcus Neisseria meningitidis Gram negative diplococcus Droplet Precautions until 24 hrs effective antbx Prophylaxis for exposed HCWs
Viral meningitis
More prevalent during late summer Most often seen in ages <40 yrs Standard Precautions Recovery usually without sequelae CSF lymphocytes without organisms
Pertussis
Whooping Cough Incubation: 7-10 days. Onset = Catarrhal stage: 1-2 weeks. Paroxysmal coughing that can last 1-6 weeks (up to 10). Droplet Precautions until 5 days effective antbx
Scabies
incubation 4-6 weeks (early as 10 days). Sx= burrow-type pruritic (itchy) lesions on hands, webs of fingers, wrists and exterior surfaces of elbows and knees, outer surfaces of feet, armpits, butt and waist. Contact precautions until 24 hours after topical tx.
Facultative anaerobe
Utilize O2 if present but still grow in absence of O2
Hep C
found in blood and certain body fluids
Incubation average 45 days
antibody detected between 4-24 weeks after onset
there is NO vaccine to prevent HCV infection
Hep B
found in blood and certain body fluids
incubation average 90 days
HBsAG (hep B surface antigen) found in serum 1-2 months post exposure
Prevention= vaccination
HbsAg- current or chronic HBV
HbsAb- recovery or immunity to HBV
Anti-Hbc-current or previous HBV infection Thom
Anti-Hbc IgM- recent acute infection
Hep A IgM Antibodies detectable
within 3 weeks of exposure
5-10 days post exposure ?
IgM antibodies to HAV (IgM anti-HAV), which are used
to diagnose acute HAV infection, are detectable within 3 weeks of exposure
and are present at the onset of jaundice
gG anti-HAV is
also detectable at onset of jaundice and remains positive lifelong, indicating
immunity to HAV.
Hep A= fecal-oral
average incubation= 28 days
Prevention= vaccination
Biofilm
Any group of microorganisms in which cells stick to each other on a surface. Also referred to as “slime”, generally composed of extracellular SNA, protein and polysaccharides. Prevents water-soluble elements (ABX and Disinfectants) from reaching pathogens
Gram stains are first step to classify organism as gram- pos or gram- neg. The determinant factor for gram stains are cell well components of
Peptidoglycans
Good gram stain specimen will have
<10 epithelial and >25 PMN. Bad= large epithelial (ex: oral contamination - spit)
Bacteria
Free living, single celled organisms, multiply through replication and cell division, cell contains DNA, ribosome membrane and cell wall
Gram + cocci in clusters
Staphylococcus.
Most common = staph aureus (MRSA, MSSA) and staph epidermis (coag-neg)- both leading causes of CLABSI
Gram + cocci in pairs or chains. Normally found in GI tract
Enterococcus.
Most common commensals in human intestines: enterococcus faecalis and enterococcus faecium. Another example =VRE
Gram + cocci in chains. Normally found in genital tract and alimentary canal (mouth, pharynx, esophagus, stomach, intestine, anus)
Streptococcus.
Most Common= Streptococcus pneumoniae (lancet shaped gram +), and strep pyogenes aka “Group A strep”
Gram + rods
Baciullus species, clostridium species, diphtheroid bacillus, Corynebacterium species and listeria species
Gram - rods
Enterobacteriaceae (Enteric- E. Coli, klebsiella pneumoniae, Serratia marcescens, Enterobacter cloacae, proteus mirabills)
and
Non- Enteric: Pseudomonas aeruginosa, Acinetobacter bahmannii , Neisseria meningitis, legionella, Haemophiles influenzae, steno
Reproduce by spore formation
Fungi
Fungi labeled as two different groups based on appearance of colony formed
Yeast (creamy)- reproduce by budding
Molds (fuzzy) spread by spores
Yeast species
Candida albicans: normal GI/skin flora
Candida auris: frequent with LTC pt with catheter. Often multidrug resistant
Long branching filaments of calls called hypae
Mold
Examples:
Aspergillus (construction)
Rhizopus (soil, environment, dressings)
Stachybotrys - black mold found after water damage
Obligate intracellular parasites that require living host cells to grow and reproduce
Viruses. Contains DNA or RNA
not living germs, proteins without RNA or DNA
Prions
Ex: CJD
Bacteria that may have + AFB smear, but don’t need isolation
Nocardia, Actinomyces, Rhodococcus, Legionella micdadei or cysts of Cryptosporidium species.
Community acquired pna (CAP) quality measure for those 65 or order
Screen for pneumococcal vax and administration before discharge, if necessary
immunocompromised status
- Neutropenia (absolute neutrophils count <500/mm3)
- Leukemia or lymphoma
- HIV with CD4 count <200
- Splenectomy
- Early post-transplant
- On cytotoxic chemotherapy
- On high-dose steroid therapy: >40 mg prednisone or its equivalents
(>160 mg hydrocortisone, >32 mg methylprednisolone, >6 mg
dexamethasone, >200 mg cortisone) daily for >2 weeks
most common ESBL-producing pathogens.
E. coli and Klebsiella pneumoniae, which confer resistance to all
β-lactam drugs except the carbapenems
Mechanical barriers to infection include
skin, mucous membranes, and tears.
Movement due to cilia or peristalsis helps to keep air passages and the
gastrointestinal tract free from microorganisms. The trapping effect of mucus
that lines the respiratory and gastrointestinal tract helps protect the lungs and
digestive systems from infection. Chemical factors include fatty acids in sweat
that inhibit the growth of bacteria. Lysozyme and phospholipase found in
tears, saliva, and nasal secretions can break down the cell wall of bacteria and
destabilize bacterial membranes. The low pH of sweat and gastric secretions
prevents growth of bacteria
The most common opportunistic
bacterial infections associated with cell-mediated immunity dysfunction are
primarily intracelluar pathogens that include:
- Listeria monocytogenes
- Salmonella spp.
- Mycobacterium spp., including M. tuberculosis
- Nocardia (N. asteroides, others)
- Legionella pneumophila, other species of Legionella
- Rhodococcus equi
- Pseudomonas pseudomallei
All viruses are
obligate intracellular parasites. Obligate intracellular parasitic bacteria include
Chlamydia, Rickettsia, Coxiella, and certain species of Mycobacterium. Epidemic typhus and Q fever
Intracellular parasites are parasitic microorganisms that are capable
of growing and reproducing inside the cells of a host. Obligate intracellular
parasites cannot reproduce outside their host cell, meaning that the parasite’s
reproduction is entirely reliant on intracellular resources.
Spores
Resistant to Abx.
The function of a spore is to permit the cell to survive unfavorable
conditions such as extremes of temperature or moisture. Spores become
dormant at these times; they do not multiply in adverse conditions. Instead,
the spore protects the bacteria until favorable conditions occur, at which
time the bacteria can begin to multiply. Spores are usually formed by Grampositive
bacteria.
Staphylococcus aureus
Food poisoning with most rapid onset (as little as 30 min, but usually 1-6 hours)
Staphylococcal toxins are
resistant to heat and cannot be destroyed by cooking. Foods at highest risk
of producing toxins from Staphylococcus aureus are those that are made
by hand and require no cooking. Some examples of foods that have caused
staphylococcal food poisoning are sliced meat, puddings, pastries, and
sandwiches. Staphylococcal toxins are fast acting, sometimes causing illness
in as little as 30 minutes after eating contaminated foods, but symptoms
usually develop within 1 to 6 hours. Patients typically experience several of
the following: nausea, retching, vomiting, stomach cramps, and diarrhea.
Most common bacterial foodborne illness
salmonella, clostridium perfringes and campylobacter
Salmonella
Foodborne illness (bacterial). Most persons infected with Salmonella develop diarrhea, fever,
and abdominal cramps 12 to 72 hours after infection. The illness usually
lasts 4 to 7 days, and most persons recover without treatment.
Associated Foods: Contaminated eggs, poultry, unpasteurized milk or juice, cheese, contaminated raw fruits and vegetables (alfalfa sprouts, melons). S. typhiepidemics are often related to fecal contamination of water supplies or street-vended foods.
Clostridium perfringens toxin
Foodborne illness (bacterial)
Incubation: 8-16 hr
Food Associated: Meats, poultry, gravy, dried or precooked foods, time- and/or temperature-abused food
Duration: 24-48 hr
Campylobacter
Foodborne illness (bacterial)
Incubation: 2-5 days
Associated Foods: Raw and undercooked poultry, unpasteurized milk, contaminated water
Duration: 2-10 days
Toxoplasma gondii
Foodborne illness (parasitic)
Incubation: 5-23 days
Flu like sx
Associated Foods: Accidental ingestion of contaminated substances (e.g., soil contaminated with cat feces on fruit and vegetables), raw or partly cooked meat (especially pork, lamb, or venison). Passed from mother (who acquired acute infection during pregnancy) to child
Duration: months
Listeria monocytogenes
Foodborne illness (bacterial)
Incubation: 9–48 hr for gastrointestinal symptoms, 2–6 wk for invasive disease
At birth and infancy. Can cause pre-mature birth
Associated Foods: Fresh soft cheeses, unpasteurized or inadequately pasteurized milk, ready-to-eat deli meats, hot dogs
Duration: variable
norovirus
Foodborne illness (viral)
Incubation: 12–48 hr
Associated Foods: Shellfish, fecally contaminated foods, ready-to-eat foods (salads, sandwiches, ice, cookies, fruit) touched by infected food workers.
Duration: 12–60 hr
Exotoxin
Secreted by bacteria, specifically gram positive. Are heat inactivated, neutralized by specific antibody and may have enzymatic activity
Endotoxin
Complexes of bacterial proteins, lipids and polysaccharides that remain firmly within bacteria. Surface components of gram negative bacteria that resist inactivation of heat, only partially neutralize by antibody and have capability of interacting with host system to set off cascade of responses that can cause fever, swelling, pain, shock, vascular leaking
Most common organism contamination for TPN
Candida
With strict adherence to aseptic compounding technique,
contamination of the total parental nutrition (TPN) solution is rarely the
cause of sepsis.
TPN can foster microbial growth. Organisms that
have been reported to proliferate in TPN include fungi (Candida albicans or
Malassezia furfur); Gram-positive bacteria (coagulase-negative Staphylococcus,
Staphylococcus saprophyticus, or Staphylococcus epidermidis); and Gramnegative
bacteria (Escherichia coli or Pseudomonas aeruginosa) bacteria.
gram - that causes chronic gastritis in humans and most common cause of ulcers
H. Pylori
Gram neg rod, can cause serious pneumonia. Known Reservoir is air conditioner cooling towers
Legionella pneumophilia
Gram neg rod/bacilli, can cause serious infections in ICU patients. Can be very resistant
Acinetobacter baumannii
Enteric gram net rod. Can cause UTI’s. Known to produce carbapenemase
Klebsiella pneumoniae
Gram positive cocci in clusters. Can cause CLASI and prosthetic infections
Staphylococcus epidermidis
Lancet shaped gram positive diplococci. Can cause pneumonia
Streptococcus pneumoniae
Gram negative diplococci. Normal flora of the respiratory tract but can cause
Meningitis
Neisseria meningitis
Gram negative rod which is considered normal flora in GI tract
E. Coli
Mold found in soil, outdoor and indoor air. Have been associated with outbreaks related to construction
Aspergillus
Good specimen (not saliva) the gram stain should show
Fewer than 10 epithelial cells
Chicken pox/herpes zoster-varicella/shingles
sudden onset slight fever, skin eruptions that are macupapular for hours, vesicular for 3-4 days then granular scab
*incubation is 2-3 weeks
*Iso chicken pox= Airborne/contact
*iso zoster = standard unless disseminated then contact. Iso until scabbed.
Incubation period scabies
4-6 weeks
Can be as short as 10 days
Types of bacterial meningitis
Haemophilus influenzae type b (HIB)
Pneumococcus (strep pneumo)
Meningococcus (Neisseria)
Pathogen that is active and reproduces, but requires livings cells to do so
Virus
HbsAg
Current or chronic HBV
HbsAb
Recovery or immunity to HBV
Anti-Hbc
Current or previous HBV infection
Anti Hbc IgM
Recent acute HBV infection
If also AbsAg+ = acute infection
Distinguishes acute from chronic infection
