BUGS Flashcards
Which microorganism is bacitracin-sensitive ?
Streptoccus pyogenes
What is the most common cause of rheumatic fever ?
Untreated pharyngitis caused by strep pyogenes.
What type of HSR is rheumatic fever ?
Type II HSR.
IgG against M protein cross-reaction with our own cardiac myosin.
What type of HSR is glomerulonephritis that occurs following strep infection ?
Type III HSR.
Against hyaloronic acid capsule (same as our basement membranes)
What is the organism that causes erysipelas ?
Streptococcus pyogenes
What is the main cause of pharyngitis is children ?
Streptococcus pyogenes
What is a rare complication of untreated pharyngitis in children ?
Scarlet fever
Possible complication of strep throat from phage-infected, Spe-producing strains.
Streptolysin O and S are virulence factors responsible for hemolysis in what strain of bacteria ?
S. pyogenes
SpeA, SpeB are superantigens responsible for toxic shock syndrome that belong to what strain of bacteria ?
S. pyogenes
What is the bacteria refered to as group A strep ?
S. pyogenes
What is the bacteria refered to as group B strep ?
S. agalactiae
S. agalactiae : bacitracin-sensitive or resistant ?
Resistant
Otherwise, S. agalactiae looks very similar to pyogenes. It is catalase ‘‘negative’’, grows in long chains of gram + cocci and is beta-hemolytic. However, s pyogenes is CAMP negative and S. agalactiae is CAMP positive.
What bacteria can cause meningitis in babies exposed to it during or just after birth ?
S. agalactiae
Due to its polyscaccharide capsule, the bug is able to cross baby’s BBB.
Which bacteria normally inhabit the lower GI and genital tract of 20% of females and can cause problems if the baby inhales it at brith ?
S. agalactiae
Which bacteria is the main cause of mastitis in breastfeeding women ?
S. agalactiae
Babies who are exposed to S. agalactiae in the vaginal canal during birth start showing signs of meningitis how long after they are born ?
within 1 week after birth.
Which strain of strep is optochin-sensitive and lysed by bile ?
S. pneumoniae
What strain of strep is alpha-hemolytic, has neurominadase A, has the capacity to autolize, causing localized inflammation and better susceptibility to atb due to release of cell wall material ?
S. pneumoniae
Antibiotics that target cell walls that are effective against S. pneumoniae ?
B lactams
Vancomycin
Always grows in chains of 2 bacteria ?
‘‘Lancet-shaped’’
‘‘diplococci’’
S. pneumoniae
Has > 90 types of capsular polysaccharides, can disable complement, cleave IgA and adhere to tissues using PspA and PspC surface proteins ?
These are virulence mechanisms of S.pneumoniae.
Leading cause of lobar pneumonia ?
S. pneumoniae
Especially in pts older than 65 y.o.
Smokers have î risk.
Leading cause of bacterial meningitis in older adults (> 65 y.o.) ?
S. pneumoniae
from untreated lobar pneumonia.
Leading cause of bacterial meningitis in children < 3 months old ?
S. agalactiae
Catalase ‘‘negative’’ gram + cocci that grows in chains and does b-hemolysis, especially when CO2 is present (capnophile):
Streptococcus pyogenes.
PCV13 vaccine :
**Protein conjugated **vaccine that protects against 13 capsule types of s.pneumoniae and recommended for use in children.
PPSV23 vaccine :
Non-protein conjugated vaccine that protects against 23 different capsule types of s.pneumoniae and recommended for use in older adults.
Boosters are required.
Older adults have decreased thymic functions, therefore, there is more benefits in offering them coverage against many capsule types vs protein-conjugated with longer memory because they can’t make proper T cell responses anyway.
Most common bacterial cause of otitis media in young children ?
S.pneumoniae
True or false, 80% of cases of otitis media resolve on their own?
True
Encapsulated bacteria are pros at natural transformation. Which bacteria is the number one best at undergoing natural transformation ?
S. pneumoniae
Are known to be effective antibiotics against s. pneumoniae, but known to cause *crisis by lysis *?
B lactams
Synergistic beta hemolysis with S.pyogenes or S.aureus:
S. agalactiae
What is the best b-lactams to give to a child with strep throat ?
Amoxicillin
What is the best atb to give to a pregnant woman who is infected with s.agalactiae ?
Ampicillin
Crosses the placenta
Viridians streptococci include what organisms ?
Streptococcus mitis, salivarus & mutans.
Optochin-resistant
alpha hemolytic
Not bile-soluble
Viridians are all normal oral flora. Which one is the number one cause of cavities and can also cause endocarditis in individuals who already had a underlying heart murmur ?
Streptococcus mutans
How to distinguish Streptococcus mutans from Streptococcus pneumoniae ?
On gram-stain, s. mutans grows as long chains vs diplococci.
S. mutans is not dissolved by bile vs S. pneumoniae.
What kind of hemolysis do Viridians do ?
alpha hemolysis
What strain of bacteria is part of normal gut flora but can be problematic if they enter the bloodstream or colonize the urinary tract ?
Enterococcus fecalis
Enterococcus faecium
Are broadly **atb resistant **and known to cause UTIs and wound infections ?
Enterococcus fecalis
Enterococcus faecium
What is the gene that allows Enterococcus species to resist Vancomycin ?
vanA cassette
Codes for an alternate peptidoglycan structure.
By extension, you can’t use b-lactams either.
2 bacteria that are PYR test positive :
S. pyogenes
Enterocci
Strains that are CAMP-test +
S. agalactiae
S. lugdunensis
Listeria monocytogenes
They can break down esculin in the agar and turn the plate to black ?
Enterococcus fecalis
Enterococcus faecium
grow in high salt conditions.
not lysed by bile
resistant to optochin
PYR + ; same as s.pyogenes.
Gram +, aerobic, b-hemolytic, spore forming rod that is motile :
Bacillus cereus
Cereolysin allows b-hemolysis in what spore forming gram + bacteria ?
Bacillus cereus
Foodborne illness linked with rice is typically from what spore forming bacteria ?
Bacillus cereus
Spore forming bacteria able to produce a poly-glutamate capsule, aerobic, non-motile and usually grows as large white ground glass colonies on blood agar?
Bacillus anthracis
B anthracis’s virulence comes from 2 A/B toxins that have the same B-subunit (protective antigens or PA), but 2 different A-subunits. One of the A subunit = edema factor (upregulates cAMP) ; the other = Lethal factor ( by cleaving MAPK stops translation).
The genes for PA, EF & LF are located on plasmids or chromosomes ?
Plasmids
Most common source of anthrax infections?
Livestock
Most common form of anthrax infection ?
Cutaneous anthrax.
represents > 95% of cases.
Low case fatality (20% if untreated).
Cutaneous anthrax is painless, necrotic wound infection with surrounding adema with usually no lymphadenopathy or swelling.
What other form of anthrax infection is caused by spores that have a very long latency and high case fatality.
Also called Woolsorter’s disease.
Pulmonary anthrax.
Not a lot of inflammation in the lungs, but a lot of edema. Usually the cough is not productive and both lobes are affected.
What is the mechanism of action of macrolides ?
The mechanism of action of macrolides revolves around their ability to bind the bacterial 50S ribosomal subunit causing the cessation of bacterial protein synthesis.
The CDC recommends what atb for mass casuality infections with anthrax ?
Fluoroquinolones
(Tendon damage is risk of long term usage)
The CDC recommends what type of atb for agriculture-related individual anthrax infections ?
Beta-lactams
Bacillus cereus and anthracis are both environmental bacteria that are broadly susceptible to atb. In case of intoxication with these, what is the course of treatment ?
No atb required
rehydration only
Specie of spore forming rods that are obligate anaerobes ?
Clostridium
Why are clostridium spore forming rods inconsistently stained ?
They use their own cell walls to make the spores, so some may appear lighter than the typical purple on gram stain even though gram +, due to the fact that they initially have fewer peptidoglycan layers than other aerobic spore forming bacteria (Clostridium use fermentation- less efficient metabolism).
Responsible for ‘‘gas’’ gangrene ?
Pushing on necrotic wound makes crepitance noise;
Develop rapidly and high case fatality.
Clostridium perfringens
Large, gram +, spore forming, strickly anaerobic, b-hemolytic (a toxin = phospholipase C)
A cellulitis with radiating, but no directional spread can be caused by what spore-forming Gram + bacteria ?
Clostridium perfringens
Myonecrosis with gas gangrene in the absence of infected wound can be caused by ?
‘‘Swarming’’ motility pattern on agar gel.
Clostridium septicum.
Mainly in pts with occult colon CA, leukemia or diabetes.
C. septicum escapes from GI tract –> blood –>muscles (low O2).
Bacteria responsible for food intoxication in buffets that only causes diarrhea approx 8-24h post ingestion?
C perfringens.
Large, gram +, spore-forming, strictly anaerobic, motile, and produce large terminal spores that makes them look like lollipops ?
Clostridium tetani
Rigid paralysis following a puncture wound is likely ?
Tetanus
Spastic paralysis with classic ‘‘lockjaw’’ or rictus sardonicus.
A/B toxin
B : binds motor neurons
A : stops GABA+ glycin release (inhibitory signal)
How do you treat tetanus ?
Metronidazole
Anti-tetanus toxin immunoglobulin (TIg)
Tetanus toxoid is part of the DTaP vaccine, which is recommended for babies as soon as ?
Adults needs boosters at what frequency ?
2 months old
boosters q 10 years
Clostridium strain that is most commonly non-motile and like Clostridium tetani, causes paralysis ?
Clostridium botulinum is non-motile.
C. tetani is motile.
Which strain of clostridium causes a flaccid paralysis as a result of A toxin preventing Ach release for vesicle in the neuromuscular junction ?
Clostridium botulinum
Main sources of C. botulinum ?
Homemade canned vegetables
Honey
Soy-based infant formulas
Honey should never be given to baby < 6 months old.
In adults and children > 1 year old, C. botulism presents as :
An intoxication
Adults and children have normal gut flora to outcompete botilinum.
Remember that bacteria that make spores do not grow well in the body as they are usually bacteria that thrive in the environement (unstable conditions)
In neonates (< 1 y.o.) botulism presents as :
Causes ‘‘floppy baby syndrome’’
An infection
(in intestinal tract)
What other conditions could present at as flaccid paralysis in the baby ?
Neonatal myasthenia gravis
Pompe’s disease
If MG is the cause, the baby is born with flaccid parylasis and sx will be better over time.
Pompe babies are born normal, quickly get parlaysis when galactose is introduced and sx get worse over time.
Baby is born normal and develop a progressive flaccid paralysis after having normal development.
How do you test for a suspected botulism in a baby?
Stool culture
(look for botulism toxins)
How do you test for suspected botulism in older children and adults ?
Test the suspected implicated food, not the patient. They don’t have the bacteria in them at all, the toxin is already on the neurons if they are symptomatic.
Which bacteria causing infection/intoxication have we not develop a vaccine against, but advise people to proper food handling practices instead ?
Clostridium botulinum
Both C. tetani and botulinum are broadly susceptible to atb. What is the atb of choice for both of these ?
Metronidazole
Less likely to harm normal flora
For babies who are infected with botulism the treatment is :
Atb
Anti-botulism toxin immunoglobulin
What bacteria is responsible for pseudomembranous colitis ?
Pseudomembrane : bunch of dead cells sloughing off all together (as a membrane).
C. difficile
carried asymptomatically by 5% of the population
Starts as watery diarrhae, then becomes more and more bloody and rich with mucous. Typical very foul odor.
Quite good at colonizing normal flora compared to other spore forming bacteria and following long-term antibiotic use, can cause inflammation and destruction of colonic epithelia ?
C. diff
Because they are quite atb resistant, they can outcompete normal gut flora following long course of atb, where most of the normal gut flora is destroyed.
DO NOT have A/B toxins, but their toxins that cause the pseudomembranous colitis are called toxins A & B :
C. diff
Most common atb associated with C. diff ?
Clarithromycin
Ciprofloxacin
True or false.
Use of alcohol-based sanitizers increases spread of C.diff spores from person to person ?
True
Treatment of C. difficile :
Oral vancomycin
Metronidazole
Fecal transplant
Gold standard : fidaxomicin
Fidaxomicin : protein-synthesis inhibitor.
Motility depends on the temperature of its environment ?
Listeria monocytogenes
Motile at 25 degrees
Non-motile at 37 degrees
It’s motility is described as ‘‘tumbling motility’’
Listeria monocytogenes
Short gram positive rod that is weakly b-hemolytic and CAMP-test + and does not make spores ?
Listeria monocytogenes
Listeria monocytogenes beta-hemolysis caused by :
Listeriolysin O
At 37C, rather than expressing flagella genes, they exprss actA, which causes restructuring of actin cytoskeleton forming ‘‘actin rockets’’ allowing bacteria to move from one cell to the other:
Listeria monocytogenes
In the human body, Listeria monocytogenes does not bother making flagellum. They get into my cells, use my actin cytoskeleton to make an actin tail and move around into my cell or to my other cells.
More actA is produced in cells that are trying to kill bacteria with ROS allowing Listeria monocytogenes to better survive the oxidative burst in cells. Why is that ?
actA gene is in the operon for glutathione.
Causes mild symptoms in healthy people but can cause septicemia in immunocompromised patients and pregnant women . The bacteria can also cross the placenta.
Pregnant women are 10x more likely to be symptomatic.
Listeria monocytogenes
True or false.
Anything that crosses the placenta needs to be intracellular but not everything that is intracellular crosses the placenta.
True
Only 2 intracellular bacteria are able to cross the placenta. Which ones?
Listeria monocytogenes (via actin rockets)
Syphillis
Many viruses do cross the placenta however. All intracellular.
In utero infections of Listeria monocytogenes can cause miscarriage or stillbirths. Among infants who survive, the case fatality is 30%. Babies who acquire listeria in utero present with what special feature at birth ?
Granulomas
(speckles all over)
Listeria monocytogenes is normal flora of many livestock animals. What is the most common source of listeria monocytogenes intoxications ?
Unpasterized dairy products.
Listeria grows pokay at frige and freezer temperatures.
Listeria monocytogenes can cause meningitis. How can you diagnose this ?
Blood/CSF culture. You incubate the plate at 4C. The reason for culturing it at 4C is that if a food is contaminated by Listeria, it is most likely contaminated by other bacteria so you don’t want them all growing on your plate. Listeria is the only one that grows ‘‘okay’’ at 4C.
Bacteria levels are quite low in the CSF so unlikely to be seen on CSF stain.
Infants who contracted Listeria in late pregnancy or near birth develop :
Meningitis 2 weeks postpartum.
Facultative psychrophile that grows at 4C and causes foodborn intoxications related to soft cheese/ice cream ?
Listeria monocytogenes
Listeria monocytogenes does what type of hemolysis ?
B hemolysis
Often not seen on gram-stain slides of patients infected with meningitis ?
Listeria monocytogenes.
Gold standard treatment for Listeria monocytogenes?
Penicillin or Ampicillin (if pregnant)
Because Listeria monocytogenes is an environmental organism, it is broadly susceptible to atb.
Gram + rod shaped bacteria and shows pleomorphism, is non spore-forming and responsible for erysipeloid ?
Erysipelothrix rhusiopathiae
Gram + rod shaped bacteria and shows pleomorphism, is non spore-forming and responsible for erysipeloid ?
Erysipelothrix rhusiopathiae
What distinguises Erysipelas from Erysipeloid ?
Usually painful
Only on hands
Lesion is purple vs red
Susceptible to many atb (environmental bug)
People who work with pigs
Can cause rapidly destructive ocular infections following traumatic inoculation of spores into the cornea ?
B. cereus.
Due to cereolysin.
Genus of gram + palissading rods
Corynbacterium
Thick cell wall (a little mycolic acid) so very purple on gram stain.
The B subunit of the A/B toxin binds to heparin-binding epidermal growth factor found on respiratory epithelium, some neurons and cardiac cells :
Corynbacterium diphtheriae
A sub-unit stops translation by binding EF2.
The beta-phage responsible for C. diphtheriae making the A/B toxin has insertion site in operon that is turned off by ?
Iron
Initial presentation is pharyngeal with grey membrane and ‘‘bullneck’’. Without treatment can cause cardiac arrythmia, heart failure. Neural sx and wound infections are also possible:
C. diphtheriae
What type of vaccine is DTaP and when do we administer it ?
Subunit toxoid vaccine.
First administration : 2 months old
Boosters : 4, 6 and 15-18 months old.
Only phage infected bacteria have toxin genes and therefore the production of toxin is an exemple of :
Lysogenic conversion
C. diphtheriae isolates only have humans as reservoirs and are broadly susceptible to atb. What atb is very effective against it ?
Macrolides
How do you test for C. diphtheria ?
Look for A/B toxin gene using PCR
Old technique was using anti-toxin antibodies - Elek test.
Makes H2S as part of metabolism which interacts with tellurite in Tinsdale media turning their color to jetblack ?
C. diphtheriae
Rare in healthy people, but can grow on indwelling medical devices and are very atb resistant because of their close association with hospitals ?
Corynbacterium jeikeium
In hospitalized patients, Corynbacterium urealyticum causes UTI that often complicate to what due to their urease activity ?
Kidney stones
Gram + bacteria that take a lot of time to grow (have a little mycolic acid in their cell wall), form ‘‘tooth looking’’ brownish colonies and clump together on slides ?
Actinomyces
(Infections are almost always endogenous)
Natural oral & vaginal flora
Involves some kind of oral trauma, usually appears on the jawline and pushing on the granulomatous lesion causes expression of yellow/orange nodules called ‘‘sulfur-granules’’.
Immunocompetent individuals can have it.
Cervicofacial actinomyces
Trx : debridement
Uniforemly susceptible to beta-lactams & macrolides
Can colonize IUDs causing which condition in immunocompetent individuals ?
Pelvic actinomyces
Only mycolic acid containing bacteria that can grow anaerobically ?
Actinomyces
Responsible for acne ?
Cutibacetrium acnes
Gram + non sporing bacilli
part of normal skin flora
Major contributor to vaginal normal flora and protects against yeats infections, staph TSS and some STIs. They are common contaminants in urine samples from women and are vancomycin resistant?
Lactobacillus
They can cause septicemia and endocarditis in very immunocompromised patients.
Don’t use alanine to make their cell walls (why they are resistant to vanco)
Main bacteria that colonize normal skin flora ?
Staph
Corynebacterium
Cutibacterium
What kind of stain for Actinomyces ?
Modified acid fast technique
Weakly acid fast and can be stained with either a gram stain or modified acid fast ?
Nocardia
Looks very filamentous.
What kind of culture media for Nocardia ?
Buffered-charcoal yeast extract
Has very complex nutritional requirements.
Nocardia’s key virulence factor that stops phagosome-lysosome fusion :
Cord factor
They also good at making catalse + superoxide dismutase, resisting oxidative burst.
In healthy people, Nocardia infection presents most commonly as :
Slowly developing, slowly resolving, slightly inflammed and itchy skin lesion following traumatic inoculation of the bacteria under the skin.
Colonies look like tiny fluffly cotton ball ?
‘‘aerial hyphae’’
Nocardia
Can cause TB like symptoms in immunocompromised patients ?
Actinomyces
Nocardia
Mycobacterium tuberculosis stops phagosome-lysosome fusion via :
PknG
Equivalent to cord factor of Nocardia
Structure made of granulocytes and other immune cells as a result of failed phagocytosis on the part of macrophages. Maintained by T cells secreting IFN-gamma :
Granuloma
Caseating center packed with bacteria & dead/dying macrophages typical of tuberculosis granuloma.
Infliximab (TNF inhibitor) increases risk of :
Immunosupressant that takes on the Th1 pathway
Granulomas will burst open, not maintained anymore by T cells.
What is the best way to visualize Nocardia ?
Modified acid fast stain
(can also be seen a little less clearly on gram stain)
Acid fast AF
Mycobacterium tuberculosis
Mycobacterium leprae
Super long to grow on culture (4-6 weeks) and look like dripped candle wax when it does.
Always starts as a pulmonary infection in people and spreads via respiratory droplets.
Mycobacterium tuberculosis
Can’t be grown in culture, need animal model to grow it :
Mycobacterium leprae
Cytokine that maintains the granuloma ?
IFN-gamma
secreted by CD4+ helper T cells
90-95% of patients infected with TB will have the bacteria walled-off in granulomas and have no symptoms. 5-10% will not maintain the granulomas and will go straight to cavitary lesions (very symptomatic). Symptoms include :
Night sweats
Fever
Wasting/Cachexia
Hemoptysis
M. tuberculosis can dessiminate through the boodstream to other body sites, especially those rich in APC like the spleen or the lymph nodes (secondary lymphoid tissues). This form of TB is called ?
Miliary tuberculosis
Pt will likely present with wasting, night sweats, fever, and abdo pain, but not necessarily pulmonary sx or TB in their sputum. Lymph node/spleen bx is required to diagnose if suspected.
If TB spreads to the spine, what is it called ?
Potts disease
Granuloma formation in response to TB is what type of HSR ?
Type IV HSR.
Most likely sites of spread of TB ?
Secondary lymphoid tissues (lymph nodes, spleen mainly).
Can also spread to my kidneys, bones and then to my spine or to the brain, causing meningitis.
Lowenstein-Jensen medium & Middlebrook Agar is used to grow what ?
Mycobacterium tuberculosis
4-6 weeks to grow.
**Acid fast bacilli **that requires acid fast stain and takes 4-6 weeks to grow when cultured ?
Mycobacterium tuberculosis
BCG vaccine (Bacille Calmette-Guerin) for prevention of TB is what type of vaccine ?
Live attenuated
Still given to newborns because benefits > risks and the time in their lives where they will have the most efficient thymus.
Not given in north america.
PPD skin test (Mantoux test) tests for :
Type IV HSR against M. tuberculosis cell envelop proteins.
TRUE OR FALSE
Positive-predictive value of PPD skin test is dependent on the prevalence of TB infection in the population tested ?
True
True or false.
BCG vaccine prevents childhood infections with TB and causes lasting immunity.
False
Decline in the function of the thymus over the lifespan decreases our protection against TB even in vaccinated people.
PPD test shows cell-mediated immunity, not infection. What does that imply ?
People who test positive might not be infected (only been vaccinated in the past) and thus should follow up with chest Xray.
Immunocompromised individuals are more likely to be infected but to test negative.
Isoniazid mechanism of action :
Stops mycolid acid synthesis
Liver damage in 10% of patients
Ethambutol is a drug that can be used for treatment of TB. What is its mechanism of action ?
Inhibits synthesis of lipoarabinomannan, a component of the cell wall of acid fast bacteria.
Can cause liver damage, colorblindness and gout.
Pyrazinamide mechanism of action ?
Disrupts ATP synthesis - disrupts interaction between plasma membrane and ATP synthase.
Rifampin is commonly used to treat TB infections. What is the mechanism of action ?
Stops RNA polymerase
TB isolates are becoming increasingly resistant to it.
Main mechanisms of drug resistance of Mycobacterium tuberculosis ?
Mutations to drug targets
Efflux pumps
To prevent resistance of Mycobacterium tuberculosis to drugs, what is the standard treatment ?
Isoniazid + Rifampin for > 6 months (directely-observed therapy)
Strains of Mycobacterium tuberculosis who are multiresistant are treated with combinations of new drugs which include :
Bedaquiline (ATP synthase)
Delamanid (disrupts cell respiration & ATP synthesis) ; used in combination with linezolid.
Mycobacterium leprae always causes skin infections and cannot spread systemically. Why is that ?
They cannot survive at human body temperature.
Skin and nares only.
CMI keeps M. leprae at very low levels, similar to how most people who get tuberculosis keep it under wraps for a long time. This form is called Tuberculoid leprosy. What are the symptoms and are people infectious ?
Slightly discolored lesions with edges that may be a little bit raised.
Not very infectious.
Th1, CMI response dominant with type IV HSR to lepromin ?
Tuberculoid leprosy.
Il-2, IFN-Y and IFNb dominate.
May have paresthesia, lesions are raised (buit up and hyperkeratotic) and patients typically have hypergammaglobulinemia ?
Th2 mediated, antibody response dominant
No type IV HSR to lepromin
Very infectious
Lepromatous leprosy.
Il-4, Il-5 and Il-10 dominate
CMI to M. Leprae has crashed (because of declining T cells levels for instance due to age, immunosupressants, or immunological tolerance mediated by Treg cells and long term low level exposure).
Begins with loss of facial hair and destruction of tissue around bridge of nose and hyperkeratosis of the face ?
Lepromatous leprosy
Leonine facies
Treatment for leprosy ?
Sulfa + dapsone
Sulfa (stops folate synthesis)
Dapsone (stops macrophage migration)
Causes tuberculosis like cavitary lung lesions, fever and waisting in people who are very immunocompromised only ?
Mycobacterium avium complex
Slowly resolving granulomatous subcutaneous infections following traumatic inoculation of the bacteria which are found in seawater ?
M. marinum
Main complication of untreated N. Gonorrheae ?
Septic arthritis
In women, N. gonorrheae is barely symptomatic. Why ?
Columnar epithelial in cervix are infected only, not cells in the vagina. Also competing flora, smaller urethra and less cells to infect compared to men who are usually very symptomatic.
What is the virulence factor that causes septic arthritis as a consequence of untreated N. Gonorrhea ?
Opa proteins
Surface protein that they can swap causing undulant symptoms.
Allow tight binding to my epithelial cells.
Are very good at disabling MAC complex (ability to hold C3b in altered conformation). People with deficiency of components of complements involved in MAC attack (C5, C6, C7, C8, C9) are more susceptible to this bacteria ?
Neisseria
What is the virulence factor of Neisseria that makes it very very pro-inflammatory ?
Lipo-oligosaccharides cell wall vs polysaccarides (Lipid A more exposed)
What bacteria have an IgA protease which cause destruction of IgA ?
Neisseria (2 strains)
Streptococcus pneumoniae
Haemophilus influenzae
î susceptibility to mucosal infections.
Gram negative that grows in pairs and tetrads and can grow in neutrophils or extracellularly ?
Non motile on their own.
Neisseria spp.
What is the best culture method for N. gonorrheae?
Thayer-Martin media
Chocolate agar in a high CO2 incubator with vancomycin and other antifungal drugs to prevent outgrowth by less fastidious normal flora.
Treatment of N. gonorrheae STD?
Ceftriaxone + azithromycin
Resistant to first generation b-lactams.
Treatment of N. gonorrheae STD?
Ceftriaxone + azithromycin
Resistant to first generation b-lactams.
Increasing resistance of N. gonorrheae has been seen against multiple classes of antibiotics. What would be an explanation for this ?
N. gonorrhae is great at both conjugation and natural transformation, making exchange of resistance genes common.
Gram negative that oxidizes both glucose and maltose, grows in pairs and can grow inside PMNs, LOS causes massive inflammation ?
N. meningiditis
Main cause of Epiglottitis with stridor and ‘‘thumb sign’’ on rx?
Haemophilus influenza
Positive Brudzinski’s and kernig’s sign indicate what ?
Meningitis
Follow by spinal tap. Gram negative cocci and lots of PMNs are likely to appear in the CSF of patient with meningitis.
What type of vaccine against N. meningiditis ?
Anti capsular
You give at 11-12 years old and booster at 16 y.o. before going to college.
MenACWY
Men B
Ddx of sore throat without other symptoms in young sexually active adults ?
Gonoccocal infection
Can cause blindness in babies born to asymptomatic mothers
Gonococcal conjunctivitis
Chlamydia trochomatis can cause identical sx by same etiology.
Prevent both with atb drops at birth.
All species lack fermentation pathways and are oxidase-positive.
Neisseria
Differences in oxidation of CHO and acid production can be used to differeniate N. gonorrheae from N. meningiditis. What CHO can they respectively oxidize ?
N. gonorrhae : glucose only.
N. meningiditis : glucose + maltose
Gram negative cocci that mainly grows in pairs and can grow inside PMNs ?
N. gonorrheae
N. meningiditis
Causes of meningitis in children and young adults ?
Neisseria meningiditis
Initially colonizes the upper RT, can spread from there to the bloodstream and then to CSF (encapsulated bacteria).
Strep pneumoniae, heamophilus influenzae and Neisseria species are pros at natural transformation, because they are encapsulated. N. gonorrheae doesn’t strictly have a capsule. What does it have that serves the same role at making natural transformation super easy?
Transformation-associated pili
Pts infected with N. gonorrheae often are co-infected with :
Chlamydia trachomatis
Catalase +, oxidizes glucose, but not maltose, causes STI ?
N. gonorrheae
IV ceftriaxone is standard treatment (< 10% CFR if treated promptly ; close to 100% if goes untreated) ?
N. meningiditis
Require hemin (X factor) and NAD (V factor) to grow but make no lysins and so can’t break down RBC on their own. We can see them grow as satellite colonies and in practice, we grow them on chocolate agar :
Haemophilus species
Gram negative bacterium that can grow as ‘‘coccobacillus’’ (longer rod). It colonizes the upper RT, where it is more likely to be found in ‘‘coccbacillus’’ short form. It is another organism that can cause meningitis.
Haemophilus influenzae
H. influenzae can causes less severe forms of influenzae because its less pro-inflammatory. What are the 2 virulence factors of H. influenzae ?
Capsule (just 1 type)
IgA protease
HiB vaccine
Anticapsular protein-conjugated vaccine that protects against the only capsule type of H. influenzae that causes disease.
Give to babies as early as 2 months ; boosters at 4, 6 and 12-15 months.
Meningitis and epiglottitis cause by H. influenzae are often associated with :
Orbital cellulitis
S. pneumoniae with H. influenzae and M.catarhalis and S. aureus are responsible for most cases of :
Otitis media
Most common cause of pink eye in children < 10 y.o. ?
Haemophilus influenzae
STI that is almost exclusively symptomatic in men that causes chancroid lesions on genitals that are super painful and bleed easily is caused by :
Haemophilus ducreyi
lesions look a lot like syphilis
What bacterium causes whooping cough ?
Bordetella pertussis
acellular pertussis part of the DTaP vaccin components that protect against Bordetella pertussis ?
Pertactin, filamentous hemagglutinin, pertussis and adenylate cyclase toxoids.
A/B toxin that î cAMP in epithelial cells causing water secretion from cells, stimulation of cough reflex. Sx persist for weeks after bacterial infection has been eliminated because A/B toxin has a very long half life :
Bordetella pertussis
Has tracheal toxin that binds and immobilizes/kills cilia ; filamentous hemagglutinin that binds CR3 (making them really good at living inside macrophages) and bind surface carbs on epithelial cells.
Bordetella pertussis
Different stages of Bordetella pertussis infection :
Paroxysmal stage can last for weeks, even after bacteria are cleared.
Bordet-Gengou or Regan-Lowe charcoal containing agar for culture of :
B. pertussis
Culture takes > 7 days
PCR better earlier test
Antibiotic most often successful in reducing length & severity of symptoms of B. pertussis ?
Macrolides
Gram-negative, obligate aerobes (catalase +) bacilli that lack fermentation pathways but are oxidase-positive. Most are motile, all are very antibiotic resistant ?
Pseudomonads
Found everywhere in nature (soil, fresh & salt water), can grow at wide range of temperatures (4-45C), tolerant to osmolarity and pH changes.
Pseudomonads
Pseudomonads are resistant to multiple classes of antibiotics, including late generation ones. What are the 2 main mechanisms of resistance ?
- Alteration of porin size
- Beta lactamases
Gram negative large rods, biofilms produced by high population density, glossy, gooey, green colonies that smell like grapes ?
Colonies are b hemolytic because of exotoxin A and phospholipases
Pseudomonas aeruginosa
The most important virulence mechanism of P. aeruginosa ?
Biofilms
Number 1 cause of lung infections in CF patients ?
P. aeruginosa
Common opportunitic infection of burn wounds?
Due to lack of sebum (sebum protects you from this bacteria)
P. aeruginosa
One of the top cause of CAUTIs that is especially hard to eradicate because the bacteria are protected by their biofilm, that also holds them to the catheter ?
P. aeruginosa
Causes hot tub folliculitis ?
P. aeruginosa
Sebum stripped from skin
Swimmer’s ear (infection of external auditory canal) after spending a lot of time in swimming pools is typically caused by :
P. aeruginosa
Db patients can also develop very destructive ear infections due to P. aeruginosa, but no link with swimming.
Abrasions caused by contact lenses can allow growth of what bacteria that can rapidly cause destructive eye infections ?
P. aeruginosa
What is Ecthyma gangrenosum ?
Destructive skin lesions that follow bloodstream infection of P. aeruginosa which can happen only in very immmunocompromised patients.
P. aeruginosa can also cause osteomyelitis in these patients.
Common contaminant of surfaces, reason why we can’t bring flowers in the hospital, very atb resistant, must test isolate individually and typically use > 1 drug at a time to treat ?
P. aeruginosa
Strict aerobic, oxidase & catalase +, beta hemolytic, smell like grape Jell-O?
Pseudomonas aeruginosa
Second most common cause of pulmonary infections in CF patients ?
Also nb 1 cause of onion rot
Burkholderia cepacia complex
B. cepacia yellowish/white (not green) and smell like dirt, not grapes.
Can also cause UTIs in catheterized pts.
Can cause meloidosis in healthy people, a pulmonary disease that is common in tropical regions of southeast Asia
Associated with lifestock
Burkholderia pseudomallei
treat with sulfa drugs or doxycycline.
Gram negative coccibacillus that is the leading cause of necrotizing wound infections in soldiers returning from Iraq/Afghanistan.
Acinetobacter baumannii
Soil bacterium, especially common in middle east & north africa.
VERY resistant to antibiotics.
Can grow as either rod shape or cocci shape
Preceeds necrotizing infection with A. baumannii?
'’Orange peel’’ cellulitis
Can cause hemorragic bullae form of necrotizing fasciitis ?
A. baumannii
Gram negative rods, oxidase-negative, catalase-positive, facultatively anaerobic. They all have some fermentations pathways and make ATP via aerobic respiration ?
Enterobacteriaceae
What are the 3 types of Enterobacteriaceae that can ferment lactose ?
E.coli
Proteus
Klebsiella
Will test positive on simmons citrate test ?
(ability to use citrate as sole source of carbon)
Salmonella
Enterobacteriacae that is urease positive ?
Proteus
Enterobacteriaceae that are motile ?
E. coli
Salmonella
Proteus
H antigen, K antigen, common antigen, O-polysaccharide, pilli, lipid A, type 3 secretion system, anti C3b & A/B toxins that î cAM and stop translation causing cell death are virulence factors of :
Enterobacteriacae
O-polysaccharides variable among strains
Polysaccharide core (common antigen) same amongst all strains of Enterobacteriacae.
What kind of response do we make against O polysaccharides of Enterobacteriacae ?
IgM
Thats why we can be infected with same strain multiple time (IgM – poor memory).
Role of type 3 secretion system in Enterobacteriacae?
Cytoskeleton rearrangment by injecting remodeling actin protein into our cells - causing the bacteria to be taken in.
Enterobacteriacae are broadly resistant to :
B lactams
Can cause infections just about anywhere, but yet is carried by just about everyone without any problems ?
E. coli
Infections mostly endogenous
Number 1 cause of UTIs ?
E. coli
Is an excellent ‘‘swimmer’’, able to ferment lacose aerobically and anaerobically, produces gas as part of metabolism, does not produce H2S or urease, beta-hemolytic (variable) ?
E. coli
ETEC causes watery diarrhae how ?
A/B toxin that upregulates cAMP
Or effacement of villi
Cut off for low ID (infectious dose) ?
less than 100 bacteria
No special exposure required.
Bacteria is very efficient at surviving gastric acidity.
Adhesins & Exotoxins of ETEC :
CFA/I CFA/II CFA/III
LT-1 (heat labile toxin)
STa (heat stable toxin)
LT-1 & STa toxins = A/B toxins that upregulate cAMP
Causes cholera-like toxins and symptoms, high ID and infections acquired via consumption of contaminated water?
ETEC
Builds ‘‘pedestals’’ using type 3 secretion system by injecting Tir proteins that bind bacterial receptor Intimin , resulting in reroganization of cytoskeleton preventing villi from reabsorbing water :
EPEC
Forms bacterial colonies with bacteria stacked like bricks on intestinal epithelial, preventing water reabsorption ?
Enteroaggregative E. coli (EAEC)
High ID
contaminated water, can cause outbreaks in daycares
Due to Aggregative adherence fimbriae (AAF)
Enteroinvasive E. coli shares what feature with Listeria and Shigella, causing the cytoskeleton to be rearranged and leading to mostly watery diarrhea, but with a little bit of blood (dysentery) ?
Actin rockets
Invasine plasmid antigen (IPA) causes the cytoskeletal rearrangements
Shiga toxin 1 & 2 (Stx-1 & Stx-2) are A/B toxins that bind the large subunit of ribosomes and stop translation. These toxins belong to what specific strain of E. coli ?
Enterohemorrhagic E. coli
Expression of these toxins are another example of lysogenic conversion.
Why does giving atb to people infected with EHEC exacerbate their symptoms ?
The phage insertion site is in an operon that is turned on by exposure to atb.
What is the main difference between Stx-1 & Stx-2 ?
Stx-1 : b subunit binds enterocytes (causing blood diarrhae)
Stx-2 : b subunit binds glomerular endothelial cells (causing hemolytic uremic syndrome)
How long after initial presentation of symptoms from EHEC can hemolytic uremic syndrome appear ?
6-10 days
Classic triad of hemolytic uremic syndrome (HUS) ?
Kidney failure
Thrombocytopenia
Microangiopathic hemolytic anemia
Schistocytes and helmet shaped RBCs in urine sample.
Infectious dose for EHEC is :
Very low
Ground meat that is undercooked is a good source of EHEC infections. Currently, most EHEC outbreaks are linked to :
Raw vegetables (manoure)
Main cause of pyelonephritis ?
E. coli
Kidney failure, but no bacteria in my urine sample
Hemolytic uremic syndrome caused by EHEC.
Intoxication not infection of kidneys
Nb 1 cause of UTI ?
E. coli
Nb 1 cause of CAUTI ?
P. aeruginosa
P pillin and flagella are virulence factors of what bacteria ?
E coli
Simmon citrate positive ?
Salmonella
Grow as black colonies on Ektoen enteric agar
Salmonella
Typhoid fever caused by :
Salmonella thyphi
rose spots
fever
can become permanent resident of gallbladder
What foods can cause salmonella ?
Contaminated raw eggs
Undercooked chicken
Most common manifestation of salmonella ?
Foodborne infection
**Gastroenteritis **
NoVo, maybe bloody diarrhea
No treatment
What strain of salmonella causes typhoid fever ?
Salmonalla serovar typhi
Typhoid fever is treated with what atb ?
Cipro
Vaccine available in endemic regions
Shigella and EHEC have similar symptoms because they share some toxins (Stx-1). What is a condition which can only be caused by EHEC ?
Hemolytic uremic syndrome
Only enterohemorragic E.coli has Stx-2.
Bipolar, ‘‘safety pin’’ staining ?
Yersinia
Enterobacteriaceae
Causes bubonic plague
Yersinia pestis
Very swollen lymph nodes ‘‘buboes’’ which can burst and cause septiciemia
Mechanism of spread : plasminogen activator expressed at 37 C which lyses clots
Yersinia pestis
flee bite which got infected from biting a rodent.
Causes blood flecked diarrhea with cramping and fever, especially in children. Associated with raw milk and undercooked pork ?
Yersinia enterocolitica
Pathogenicity mechanism : restructuring actin cytoskeleton of APCs via yop proteins.
Like monocytogenes, they grow well at 4C
Yersinia
Causes lobar pneumonia
Can cause NAFLD
Auto-brewery syndrome
Klebsiella pneumoniae
Characteritic feature of lobar pneumonia by K.pneumoniae ?
Bright red, gelatinous sputum
‘‘currant jelly’’
Rusty sputum likely pneumonia caused by :
S. pneumoniae
Pneumonia associated with green sputum and fulminant course likely caused by ?
P. aeruginosa
Kidney stones producing UTI , Urease +, H2S +, able to ferment lactose aerobically and anaerobically ?
Proteus mirabilis
Enterobacteriaceae that produce bright pigments are usually non pathogenic except they might be in a particular context :
Enterobacter, citrobacter, morganella, serratia, providencia, erwinia ..
can cause septicemia in hospitalized patients
Can cause necrotizing fasciitis secondary to foodborne infection (shellfish) or from wound infection following exposure to seawater ?
Vibrio vulnificius
GI infection that look just like v. parahaemolyticus, but can progress to gangrene in the legs.
More common in hepatic dysfunction
V. vulnificius
Very very high ID ; acute diarrheal disease due to upregulation of cAMP; bacteria are never internalized by intestinal cells ; from contaminated water :
Vibrio cholera
How do you treat vibrio infections?
A little resistant to b lactams;
Treat with macrolides & tetracyclines
Are more resistant to osmotic stress than most pathogenic bacteria due to their adaptation to brackish water ?
Vibrio species
Incubation of 48-72h, followed by fever and cramping, abdominal pain (severe) , diarrhea that is initially watery, followed by bloody diarrhea.
Most people will get a relapse after it felt they were feeling better; Pretty low ID.
The severe abdo pain can be confused as appendicitis.
Campylobacter
Main host of cholera bacteria ?
copepods (mini shrimps)
Can only be cultured in a ‘‘campy jar’’ that creates a 5% O2 and 10% CO2 environment ?
Can grow at 43C, would kill off most other bacteria and allow us to isolate it.
Happy about you getting a fever…
Campylobacter
Very skinny curved rods with 1 flagellum at each end and can be seen on gram-stain of pt’s stool ?
Campylobacter
Spin themselves through the intestinal epithelial cells, disrupting junctions between cells and causing infalmmation :
Campylobacter
Causes Guillain-Barre syndrome
Most common cause of flaccid paralysis in US.
Campylobacter jejuni
C. jejuni o19 has a sequence of polysaccharides identical to that of human motor neuron causing Guillain-Barre syndrome as autoimmune sequela.
The antibodies targeting gangliosides found on nodes of ranvier deposit on neurons, leading demyelination.
Virulence factors include mucinase, cagA, vacA, urease, flagella, T3SS
H. pylori
Gram - bacteria
65-80% of all gastric CA are caused by :
H. pylori
However, prevents esophageal CA (urease decreases acidity of stomach, reducing reflux and subsequent dysplasia). That is why we don’t treat everyone for H pylori if they are carriers, but asymptomatic.
Diagnosed by urease breath test
H. pylori
PPI
Clarithromycin
amoxicillin > 2 weeks
treats what ?
H. pylori
Risks
Clarithromycin : c diff
î pH : î risk of bacterial infection with high ID (terrible at surviving my gastric acidity)
Best at atb resistance ?
Pseudomonads
Absolute worse at atb resistance ?
Spirochetes
Tick needs to be attached at least for how long to be able to transmit lyme disease ?
8h
What are the virulence factors of B. burgdoferi ?
OspA surface protein : colonization of tick guts, expressed at 25C
OspC surface protein : spread from tick to mammals, expressed at 37C.
Rash that develop 1 week to 1 month after tick bite
Erythema migrans or bulls eye (>5cm)
B. burgdoferi
The only vector for lyme disease
Ixodes species carry B. burgdorferi.
Lone star ticks can cause :
Acquired red meat allergy
IgE & IgG
Borrelia, treponema and leptospira species are part of what class of bacteria ?
Spirochetes
Have internal flagella between 2 layers of cell envelope and you need darkfield microscopy to visualize them ?
Spirochetes
Very susceptible to b-lactams (may be resistant to other drugs though)
Spirochetes
Treponema, leptospira, borrelia
Transmission is blood-borne
Difficult to grow in culture
Not visible on gram stain
Spirochetes
Causing an immune reaction that causes me to attack my CNS (neuropathy, encephalitis), acrodermatitis atrophiticans and destructive chronic arthritis ?
Late stage lyme disease (stage 3)
Weeks to months post tick bite
people before this stage typically had d
Lab criteria for diagnosis of lyme
Demonstration of dx levels of IgM or IgG antibodies to the spirochetes (helpful in primary and secondary stages).
Chronic stage (3rd stage) : autoimmune disease at this point : î in antibody titer on bad days vs good days is criteria for dx… a little bit dicier.
Painless chancroid lesions with local lymphademopathy, transmitted sexually.
Primary stage
Lesions will go away on its own in 2 months. Generally why people don’t consult
Syphilis
Symptomatology of secondary stage syphilis
Palmar rash, bodywide rash, lymphadenopathy (generalized), condyloma latum, flu-like symptoms, neurosyphilis (usually asymptomatic)
Transmitted during primary and secondary syphillis.
Combo of type II and IV HSR
Lyme disease
Syphilis
Stage 3 syphilis presentation ?
AAA, aortitis, psychiatric manifestations, gumma (open destructive granulomas) as a result of destruction of tissues. Destructive bone and skin lesions.
all sx caused by autoimmune response.
Sloughing of skin, ‘‘snuffles rhinitis’’, deficiencies in cartilage in newborn
Congenital syphilis
You will never development tertiary syph (you are immune to it) but you will have lifelong infection with tissue destruction.
Deficiencies in bone and teeth development later in life, ‘‘saddle nose’’, ‘‘Huntchinson teeth’’ and ‘‘saber shins’’ or bowed legs.
Fibronectin wrapping of tissues by bacteria
Congenital syphilis
Drug of choice for syphilis :
Penicillin
Why are men 8x more likely to be infected with syphilis ?
Men who have sex with men exclusively are much likely to have syphilis vs men who have sex with women or both with women and men.
