Module 12: Microbiology and Infection Flashcards
The process of infection
- agent
- reservoir
- portals of entry and exit
- mode of transmission
- immunity
Robert Koch and Koch’s postulates
Definition and Types of Reservoirs
- Definition: the normal habit where the agent lives and multiplies
- where the agent propagates itself in nature
- Types:
- symptomatic carriers
- carriers
- inapparent throughout history
- incubatory
- convalescent
- animals
- direct zoonoses
- inanimate objects
- water
- food
- soil
- air
- fomites
The Portals of Infection
- 3 I’s: inhalation, ingestion, injection
- respiratory tract
- upper and lower
- **most common**
- conjuctiva
- urogenital tract
- GI tract
- upper and lower
- placenta
- mother to child transmission
- skin
- broken and unbroken
Modes of Transmission
- contact
- requiring proximity to an infected host or discharge from an infected host
- vehicle:
- an inanimate intermediate carrier
- i.e. chapstick, shared waterbottle
- Vector
- an animate carrier, often an insect
- mechanical
- e.g. carried on the foot of an insect
- biological:
- grows inside vector
- i.e. mosquito
- grows inside vector
Define: Infection
- entry and multiplication of a microorganism or parasite in the body of a host
Define: Infectious disease
infection + signs and symptoms
Define: Contamination
Presence of a living agent on the exterior of the body or an article of clothing
Define: Reservoir
the normal habitat where the agent lives and multiplies
- a dead-end host or temporary resting place of the agent is not a reservoir
Define: Carrier
a person or animal that harbor an infectious agent yet does not show any signs of infection
Define: Zoonosis
an infection naturally transmitted between non-human animals and humans
Define: Immunity
the host factors that alter the likelihood of infection and disease after the agent is encountered
Overview: Prokaryotes
- Bacteria
- do NOT have a true nucleus
- do NOT have organelles
- smaller ribosomes (70S) (30S/ 50S)
Overview: Eukaryotes
- Fungi; Protoza and Helminths
- have a true nucleus
- have organelles
- larger ribosome (80S) (40S/60S)
4 major groups of pathgoens that infect humans
- bacteria = prokaryotes
- fungi = eukaryote
- protozoa and helminths = eukaryotes
- viruses
Gram Positive Bacteria
- stain Purple due to iodine
- contain thick Peptidoglycan cell wall
Gram Negative Bacteria
- stain orange
- contain lipopolysaccharide outer membrane
Catalase Test
- will demonstrate if a bacteria is capable of aerobic respiration
- catalase is an enzyme that is used to protect the cell from oxidative damage by reactive oxygen species
- 2H2O2 → 2H2O + O2
- enzyme action is to breakdown toxic H2O2 (substrate name) producing gaseous oxygen and water
Coagulase Test
- this test is used to identify S.aureus which produces the enzyme coagulase
- Coagulase causes plasma to clot by converting fibrinogen to fibrin
- two types of coagulase are produced by most S. aureus
- Free coagulase:
- converts fibrinogen to fibrin by activating a coagulase-reacting factor present in plasma
- free coagulase is detected by clotting in the test tube
- converts fibrinogen to fibrin by activating a coagulase-reacting factor present in plasma
- Bound coagulase: (clumping factor)
- converts fibrinogen directly to fibrin without coagulase-reacting factor
- this can be detected by the clumping of pf bacterial cells in the rapid slide test
- converts fibrinogen directly to fibrin without coagulase-reacting factor
- Free coagulase:
Gram-Positive Cocci (3 examples)
- Staphylococcus aureus
- Streptococcus pneumoniae
- Streptococcus pyogenes (GAS)
Staphylococcus aureus
- Gram-positive cocci
- non-motile, catalase positive, oxidase negative
- mode of transmission:
- contact, unwashed hands
- Causes infection including:
- skin abscesses, osteomylitis, endocarditis, septic arthritis, entero toxis: Toxic shock syndrom and SSSS
- enterotoxins lead to effects in gut = diarrhea
- skin abscesses, osteomylitis, endocarditis, septic arthritis, entero toxis: Toxic shock syndrom and SSSS
- tx for MRSA: oral: Vancomycin or doxycyline, clindamycin, trimpethoprim-sulfamethoazole (Septra)
Staphylococcus epidermidis
- Gram positive cocci
- mode of tranmission:
- contact, unwashed hands
- Causes infections such as:
- prosthetic device infections, IV catheter infections, sepsis, meningitits, endocarditis, UTI
Gram-Negative Cocci (2 examples)
- Neisseria gonorrhoeae
- Neisseria meningiditis
Neisseria gonorrhoeae
- gram-negative cocci
- mode of tranmission:
- sexually; newborns can be infected during burth
- Cause of infections:
- in genital tract
- can reach organs via the bloodstream
- ceftriaxone + azithromycin
Neisseria meningiditis
- gram-negative diplococci
- catalase and oxidase positive
- non-motile
- encapsulated
- mode of transmission:
- airborne droplets
- Causes infections such as:
- meningococcemia, and meningitis
- most severe form of meningococcemia = Waterhouse Friderichsen syndrome
- **life-threatening**
- most severe form of meningococcemia = Waterhouse Friderichsen syndrome
- meningococcemia, and meningitis
- tx: 3rd generation cephalosporins (ceftriaxone)
Gram-negative bacilli (8 examples)
- E. coli
- Klebsiella
- Salmonella
- Vibrio cholerae
- Shigella
- Campylobacter jejuni
- Helicobacter pylori
- Bordatella pertussis
- Pseudomonas aeruginosa
E. coli
- gram-negative bacilli
- mobile
- mode of transmission:
- fecal-oral route
- causes infections such as:
- 5 major GI infections
- enteropathogenic
- enterotoxigenic: **most common cause of travelers diarrhea** Heat Labile Toxin: 2nd messenger cAMP →loss of electrolytes and water →secretory diarrhea
- Heat Stable Toxin
- enteroinvasive
- enterohemorrhagic: shiga toxin: inhibits protein synthesis (leads to apoptosis)
- enteroaggregative
- 5 major GI infections
- tx: avoid abx for enterohemorrhagic E.coli in children → increase risk of hemolytic uremic syndrome
- avoid anti-motility drugs
- rehydration
Klebsiella
- gram-negative bacilli
- mode of transmission:
- contact with ulcerative genital lesions
- causes infections such as:
- lobar pneumonia, lung abscess, UTI, bacteremia, enteritis, and meningitis (in infants), wound infections
Salmonella
- gram-negative bacilli
- uncooked chicken
- mode of transmission:
- fecal-oral
- specific contaminated food
- causes infections such as:
- “food poisoning” or gastroenteritis
- Starts with abdominal cramping followed by fever, diarrhea, and sometimes vomiting
- Diagnostic: Cx of stool
- Tx: Ceptra or Cipro or Fluoroquinolones (or 3rd generations cephalosporins if severe)
Vibrio
- gram-negative bacilli
- mode of transmission:
- fecal-oral; raw or inadequately cooked seafood
- Causes infections such as:
- cholera pandemics, epidemics and worldwide outbreaks
- tx: Tetracycline for moderate-severe cases
Lipopolysaccharide (LPS)
- produced by most gram-negative bacteria
- mostly serves at the major structural component of the outermembrane
- **modulates responses by the host immune system**
- low quantities →inflammation:
- monocyte/macrophage/ neutrophil activation
- endothelial activation
- complement activation
- Moderate quantities → systemic effects:
- fever
- leukocyte release from bones
- acute-phase reactants from liver
- High quantities → Septic Shock
- low cardiac output
- low peripheral resistance
- blood vessel ijjury, thrombosis, DIC
- ARDS
- acute respiratory distress syndrome
- low quantities →inflammation:
Mycobacterium
- only bacteria that are acid-fast
- resist staining in lab
- rods
- Mycobacterium tuberculosis
- Mycobaterium leprae
Mycobacterium tuberculosis
- acid-fast (lack a cell wall → only cholesterol), slow growing
- mode of transmission
- respiratory droplets
- 1.7 million people die each year
- causes disease in highly oxygenated tissues → aerobes
- infect the macrophages
- formation of granulations
Mycobacterium leprae
- acid-fast
- rod
- mode of transmission:
- prolonged close contact
- humans are natural host
- Lesions end up on cooler parts of the body such as the skin, nose, and peripheral nerves
- aka Leprosy
Rickettsiae
Rocky Mountain Fever
obligate intracellular gram negative coccobacilli
non-specific sxs (fever, myalgias, severe headache)
Rash that appears 2-6 days later
tx: Doxycycline
Measles
aka morbillivirus
negative sense, ssRNA
morbilliform rash
Koplik spots
begins on face and spreads to rest of body
Mumps
aka paramyxovirus
ssRNA
rubella
- toRch
- ssRNA
- 2-3 week incubation period
- lymphadenopathy
- pink maculopapular rash that begins on the face and lasts 3 days
- starts on face and spreads, spreads much faster than measles (rubeola)
- no cough, milder rash, and no koplik spots
- tx: supportive care
Erythema Infectiosum
ssDNA
aka slap cheek, or Fifth disease
aka Erythema infectiosum
rash worsens with bath
caused by Parvovirus B19
targets the erythroblasts →stops RBC production
can cause neonatal hydrops faecalis
tx: intrauterine blood transfusion for hydrops faecalis
Rabies
Rhabdoviridae
bullet shaped ssRNA, negative sense
tx: rapid PEP
HPV
Human papilloma virus
dsDNA
Influenza
ssRNA
hemagluttinin and neuraminidase
tx: neuraminidase inhibitors
vaccines: target hemagluttinin
Type A = most common
Type B= humans only
Type C = nonsymptomatic, little medical concern
SHIFT vs DRIFT
Prion
Creutzfeldt-Jakob Disease
Sponge-like lesions in the brain
as prions build up in brain–> it starts to shrink
pt usually dies within a year
Taniea Solium
from pigs helminth: tape worm
can cause cysticerosis if you ingest the eggs
tx: Praziquantel
Taenia Saginata
Cestodes (tapeworms)
from cows
sxs: weight loss, vomiting, appendicitis
do NOT form cysticercosis
tx: Praziquantel
Schistosomiasis
helminth: blood fluke (trematode)
- S. mansoni and S. japanicum: S Am, Mid East, Carib, Africa; Asia
- found in mesenteric venules, shed eggs into intestine
- hepatosplenomegaly, GI hemorrhage, portal hypertension
- S. haematobium: Africa and MidEast
- found in bladder veins, shed eggs into bladder/urine
- urticaria, hematuria, dysurea
- bladder cancer in advanced stages
- Diagnosis:
- ID of eggs in stool or urine (must be present in at least 3 samples)
- tissue biopsy (rectal or bladder)
- Tx: Praziquantel
Loeffler’s Syndrome
eosinophilic, cough up worm and swallow it
Pinworms
- Enterobious vermicularis
- Helminth: nematode (round worm)
- tx: Albendazole
**most common helminth infection in US** esp in children <12 yo
Roseola
HHV- 6
dsDNA
**ONLY VIRAL EXANTHEM THAT BEGINS ON THE TRUNK**
HIGH fever → rash
tx: supportive
Positive sense vs negative sense RNA
positive sense: very similar to mRNA → directly to protein
negative sense: is the complement to mRNA, needs to get converted to positive sense by RNA pol before translation can occur
Giardia
Giardia lamblia
- **most common protozoan parasite in the US **
- tx: metronidazole
Scabies
Sarcoptes scabiei
type of mite
tx. Permethrin
Candidiasis
yeast→Candida
- tx: fluconazole
- Intertriginous infections: well-demarcated erythematous patches of varying size and shape, primary patches may have satellite papules and pustules
Histoplasmosis
- Histoplasma
- Systemic fungi and mold → yeast at 37C
- inhalation from bats/ birds: CAVES and TREE REMOVAL
- acute pneumonia sometimes developes
- infect Macrophages
- bone marrow disruption
- apical pulmonary lesions resembling cavitary TB
- tx: itraconazole
Cryptococcosis
- yeast that can end up in the brain but is inhaled!
- **Defining opportunistic infection in aids patients**
- skin lesions that look similar to acne, molloscum contagiosum, or basal cell carcinoma
- CNS: low grade fever, ocular or facial palseys, headache
- Lungs: pneumonia, AIDS (severe dyspnea)
tx: Fluconazole for non CNS, CNS: amphotericin B
Pneumocystis
- yeast: pneumocystis jirovecii
- **only issue for immunocompromised people**
- aerosolized: fever, dyspnea and DRY cough
tx: Bactrim (sulfamethoxazole/trimethoprim )
high risk for HIV pts with CD4 counts <200/mcL
Strep pneumoniae
- gram + diplococci, ENCAPSULATED
- causes pneumonia:
- rusty mucus
- productive cough
- fever
- malaise
- sudden onset chills and rigors (violent shaking)
- causes: bacteremia and meningitis
- tx: Ceftriaxone
Neisseria meningitidis
- gram - diplococci, encapsulated
- tx: 3rd generation cephalosporins
- prevention: menveo and bexsero
Neisseria gonorrhea
- gram negative diplococci
- fimbriae
- encapsulated
- tx: Ceftriaxone
Diptheria
- caused by Corynebacterium diptheria
gram + rod - exotoxin
- begins with sore throat and fever
- pseudomembrane and lymphadenopathy
- myocarditis
- tx: Diptheria antitoxin + erythromycin or penicillin
Shigella
- gram - rod, with mobile tail
- bacterial dysentery
- facutative anaerobe
- fecal-oral
- fever, neutrophils in stool and blood may be present
- explosive watery diarrhea that progresses to mucoid and bloody with pus in stool
- produces “Shiga” enterotoxin: neurotoxic, cytotoxic, and enterotoxic
- associated with seizures
- tx: oral rehydration and electrolyte replacement and fluoroquinolones
*
Salmonellosis
- gram negative rod
- facultative anaerobe
- uncooked chicken and contact with reptiles
- S. typhi = typhoid fever
- enteric fever as a results of bacteremia
- “pea soup” diarrhea that may be bloody
- S. enterica
- gastroenteritis with “pea soup” brown-green color
- may have blood
- gastroenteritis with “pea soup” brown-green color
- tx: electrolyte and fluid replacement + Fluoroquinolones
Campylobacter jejuni
- curved gram negative bacillus
- fever with periumbilical abdominal pain (can mimic acute appenditicis)
- diarrhea watery →bloody
- transmission: contaminated food, domestic animals are a reservoir
- associated with Guillain Barre Syndrome
- unpasteurized milk
- tx: Macrolides or fluoroquinolones
- invasive diarrhea
Non-invasive Diarrheas
- Pathophys: enterotoxins increase GI secretion of electrolytes→secretory diarrhea
- no cell destruction/mucosal invastion
- Affected Area: small bowel→large voluminous stool
- Vomiting: often predominant sxs
- fecal blood/wbc/mucus: absent
- examples: viral, S. aureus, V, cholera, enterotoxigenic e. coli
Invasive Diarrheas
- Pathophys: cytotoxins cause mucosal invasion and cell damage
- affected area: Large bowel → many small-volume stools, high fever
- vomiting not as common
- for fecal blood/ WBCs and mucus
- examples: enterohemorrhagic E coli, Shigella, Salmonella, Campylobacter, Yersinia
Metronidazole
antifungal and antiprotozoal
Botulism
- Gram positive rod, Spore former, exotoxin, obligate anaerobe
- neurotoxin blocks release of acetylcholine
- canned food, honey for <1 year olds
- flaccid descending paralysis, N/V/D, 8 Ds, bilateral cranial nerve paralysis
- tx: antitoxin
Cholera
- Vibrio cholera, gram negative rod that looks like a comma, oxidase positive
- enterotoxin
- rice water stools
- NO fever
- diagnosis: stool cx
- tx: oral rehydration for mild cases, doxycycline for mod-severe cases
Rheumatic Fever
- causal agent: strep pyogenes (group A strep), gram positive cocci, beta-hemolysis, encapsulated
- Fever
- polyarthritis, carditis, erythema marginatum mostly on trunk and extremities → secondary autoimmune response
- tx: Penicillin G/amoxicillin and aspirin
Tetanus
- Clostridium tetani: gram positive rod, spore former, motile, obligate anaerobe, neurotoxins (exotoxin)
- spores from soil enter wound
- neurotoxins block release of inhibitory neurotransmitters like GABA and glycine → Severe Muscle Spasm descending
- tx: Metronidazole with tetanus immune globulin
- dtap and tdap
Malaria
- Plasmodium: blood and tissue protozoa. P. falciparum = most deadly: Cerebral malaria (AMS, delirium, seizures, coma) and blackwater fever (severe hemolysis +hemoglobinuria (dark urine) + renal failure)
- Cyclical Fevers (every 3 days or so)
- rigors, vomiting, myalgia, diaphoresis, hemolytic anemia, splenomegaly
- tx: Chloroquine
Toxoplasmosis
- protozoan carried by cats after ingesting infected mice
- disease in neonates is severe:
Tetrad of abnormalities:
- bilateral retinochoroiditis
- cerebral calcification
- hydrocephalus or microcephaly
- psychomotor retardation
- fever, jaundice, intracranial calcifications
- diagnosis: immunofluorescence assay for IgM antibody
- tx: Pyremethamine
Epstein Barr Virus
- dsDNA, mononucleosis, and Burkitt Lymphoma
- splenomegaly
- Burkitt Lymphoma: B-cell lymphoma presenting as jaw tumors in Africa
- tx: Acyclovir for mono, Chemo for burkitt lymphoma
ABx that target cell wall synthesis
-
Beta-lactams
- penicillins
- cephalosporins
- carbapenems
- monobactams
- Vancomycin
- Bacitracin
Abx that target the Cell membrane
- Polymyxins
Abx that target the 30S subunit of prokaryotes
- target protein synthesis in prokaryotes
- tetracyclines
- aminoglycosides
abx that target folate synthesis
- sulfonamides
- trimethoprim
- aka targets nucleid acid synthesis in prokaryotes
abx that target DNA Gyrase
- aka abx that target nucleid acid synthesis in prokaryotes
- Quinolones
Abx that target RNA polymerase
- Rifampin
- aka abx that target nucleic acid synthesis
abx that target 50S subunit
- target protein synthesis in prokaryotes
- Macrolides
- clindamycin
- linezolid
- Chloramphenicol
- strepogramins
-azoles
- antifungals that inhibit the synethsis of ergosterol (the main fungal sterol)
-polyenes
5- fluorocytosine
- antifungal that inhibits macromolecular synthesis
- inhibits fungal nucleid acid synthesis
Classes of Antivirals
- Antiretrovirals:
- attachment and penetration
- uncoating
- reverse transcription
- Integration
- Transcription
- Translation
- Release
- Antivirals
- attachement and penetration
- uncoating
- replication and expression
- assembly
- release
antifungals that form membrane pores
- amphotericin B
- nystatin
Gram Positive Bacilli (5 examples)
- Bacillus anthracis
- Corynebacteria diptheria
- Clostridium tetani
- Clostridium botulinum
- Clostridium difficile
Yeast vs Mold Reproduction
- yeast reproduction:
- budding asexually though mitotic asexual divison
- Mold reproduction:
- form hyphal septa
zika
- ssRNA, negative sense
- causes microcephaly, often asymptomatic in adults
- can be sexually transmitted and through aedes mosquito
- s/sxs: maculopapular rash, joint pain, fever, conjunctivits
- diagnosis: RT-PCR testing
- tx: rest, acetaminophen → avoid NSAIDs and ASA
Strongyloides stercoralis
Strongyloides stercoralis
nematode (round worm)
worm penetrates skin→lungs→GI tract
Loeffler’s syndrome: eosinophilic pneumonia, cough up worm and swallow it
CAN HAVE AUTOINFECTION → poop out worms but they repentrate skin around the anus and autoinfect
Tx: Ivermectin or albendazole
