What are following strategies for combating drug resistance
- Administer a combination of two antibiotics with different modes of actions
- Develop inhibitors of drug-inactivating proteins and efflux transporters
Define the MIC
the lowest concentration of an antibiotic that is inhibitory to bacterial cell growth
A patient has systemic febrile illness, which item in the history would indicate the highest risk for Brucella infection
Brucella: Bruce’s farms
contact with livestock or animal products
What antigens are effective for agglutination of intact bacteria by antibody?
-flagella (H antigen)
Capsule (K antigen)
(things outside of the bacteria, components of the cell wall.
Which characteristic of mycobacterium tuberculosis is believed to be the most essential to its transmission?
Their impermeable lipid rich envelope
-making them highly resistant to heat, cold and drying allowing them to persist for long periods of time in the environment
Gram stain has been performed to get the stain and the shape. An additional rapid test that may be preformed would be:
Serotyping using slide agglutination
When are each of these plates useful; Lowenstein-Jensen medium BCYE agar Chocolate agar Thayer-Martin Tellurite-containing medium such as Regan Lowe
Lowenstein-Jensen medium: standard medium used to grow M. tuberculosis
BCYE: clue for legionellosis
Chocolate agar: required to grow Neisseria species or Haemophilus inflenzae from sterile sites such as CSF
Thayer-Martin: chocolate agar with antibiotics used to culture only Neisseria species
Tellurite: is a clue to C- diphteriae
18 yr old college freshman living in university develops headache, neck stiffness, and fever. Gram stain of the CSF shows Gram-negative bacteria. A latex particle agglutination test confirms bacterial meningitis. The causative agent is most likely
Haemophilus influenza is only likel except for a 3 month to 5 year old child who has not been vaccinated as a child.
(young adult, crowded living conditions) is the giveaway to neisseria meningitidis
11 yr old girl, has gastrointestinal infection with cramping and watery stools. After several days she begins to pass blood per rectum and is hospitalized. She has decreasing urine output with rising blood urea nitrogen. . Total blood count reveals anemia and the peripheral smear is remarkable for fragmented red cells. What is the agent
Shigella sonnei - what is described is bacterial dysentery (blood and mucus in stool) `
After extensive oral surgery a 66 yr old patient who had rheumatic fever did not take prescribed perioperative prophylactic antibiotics and developed sub acute infective endocarditis. Which is the causative agent
Rheumatic fever was caused by Strep pyogenes
Viridians streptococci - which are part of the normal oral flora, are very good at attaching to damaged heart valves when they enter circulation after oral surgery.
women went to peru, she develops profuse, water diarrhea with flecks of mucus, both are hospitalized because of severity and rapidity of dehydration but she is not febrile. What is the agent?
what is a common virulence factor for bacteria that colonize mucosa?
ex. Neisseria meningitidis, streptococcus pneumoniae
What do chloramphenicol, tetracycline and erythromycin all have in common?
They inhibit the 70S ribosome.
What are the five most common cases of food poisoning world wide.
- Clostridium perfingens
What are the five most fatal microbes that cause food illness
- Vibrio vilnificus
- Clostridium botulinum
- Mycobacterium bovis
- Hepaptitis A
What are examples of nontreponemal tests and specific treponemal tests.
The difference between the two is one you are looking for antibodies the syphillus produces, the other is you are looking for what the body produces against syphillis.
Nontreponemal tests: syphillus infection leads to generation of antibodies to common antigen of host and these antibodies are called reagin.
Complement fixation: reagin in serum can fix complement in presence of cardiolipin
Specific: you detect antibodies directly towards treponema.
- FTA-ABS (indirect immunofluorescence)
- TPHA - RBCs treated to adsorb T.pallidum on surface, then mix with serum?
What are general characteristics of spirochetes and what are the ones you need to know
They are Gram Negative, coiled cell wall, and motile. They are best visualized using dark field microscopy. Spirochetal infections usually have stages of infections.
- Leptospirosis - Leptospira interrogans
- Treponema - syphillis
- Borelia burgdorferi - lyme disease
- Borellia recurrentis - relapsing fever.
Distinguish endemic and epidemic relapsing fever
I would think about if there is a middle man or not.
Epidemic: human to human transmission via the human body louse and usually happens during times of difficulty.
Endemic: there is another vessel. From animal to tick to human
Characteristic: sudden onset of fever with chills, severe headache and malaise which ends abruptly. Severity of symptoms decrease with each relapse.
Which organisms are transmitted through contaminated water?
- Leptospira interrogans - animal urine
- M. Marinum
- Legionella pneumonia - aerosol from water supply
Hawaiin Patient has conjunctiva. Other than that kinda okay and only had a mild fever. Patient has been swimming in their pool after the dog was in there.
What are the five serotypes of chlamydia trachomatis and their clinical manisfestations
- Ocular trachoma- the most common cause of blindness worldwide. Chronic conjunctivitis
- Inclusion conjunctivitis: Acute conjunctivitis which in adults, more than half also have UTIs
- UTI - most common cause of STD in America. The symptoms are largely asymptomatic. IN a woman the prolonged infection leads to urethritis, cervicitis and eventually PID (pelvic inflammatory disease) which leads to infertility. Men get urethritis, epididymitis, proctitis.
- Lymphogranuloma venereum - chronic infection of the lymphatic system. Swollen inguinal nodes
- Lymphogranuloma venereum
- infant pneumonia
What are general characteristics of chlamydia and the 3 species.
All chlamydia are obligate intracellular because they can’t synthesize ATP and they all share a unique lifestyle: As extracellular spores they are infectious stage, they get phagocytosed and form a reticular body (the second stage) and they live in the macrophage. The reticular bodies multiply, the cell ruptures and releases the Elementary bodies (spores). Difficult to stain but closer to Gram negative
- Chlamydia pneumoniae - mild upper respiratory tract infections but can also cause pneumonia and bronchitis
- Chlamydia psittaci: fever, headache, sore throat, cough that comes later in disease
- Chlamydia trachomatis.
What are grouped under “Ricketssia and other related organisms”
Rickettsia & Orentia
Erlichia and anaplasma
HGA/ anaplasma phagocytophilum
HGE/ Ehrlichia chaffeensis
Coxiella burnetti/Q fever
If you took an infected cell with Chlamydia trachomatis, looking under light microscopy what would you see?
A membrane bound inclusion body in the cytoplasm
What is the diagnostic test used to detect C. trachomatis
PCR based tests:
NAAT of nucleic acid from urine specimen or vaginal swab for women.
A young women comes in. You try gram staining but see nothing. You immunofluorescent stain epithelial cells centrifuged from urine detected a few cells with large cytoplasmic inclusions what is likely?
She also has cervicitis.
A boy comes in with fever, rash, malaise, nausea and vomiting. The rash extends to the patient’s palms and soles. Culturing even on chocolate agar proved impossible. Why?
This is Rickettsia Ricketsi and it is an obligate intracellular. Those pathogens needed to be grown in living mammalian cells.
In patients with Rocky Mountain fever, what kind of cell would you expect pathogen to be dividing in?
What would the infected cell of the Rickettsia look like under light microscopy?
You would see small rod shaped bacteria that are free in the cytosol.
What is the mode of action of erythromycin
Erythromycin is a kind of macrolide alone with azithromycin, clarithromycin, telithromycin
It binds to the large subunit (50S) of the prokaryotic 70S ribosome and blocks the translocation step. This is generally bacteriostatic.
25 yr old Patient has fever, headache and nonproductive cough for the past 3 days. She has an atypical pneumonia which shows bilateral lung infiltrates. Culture didn’t reveal anything. penicillin G was prescribed and this had no effect. A zpack did. What does she have
First of all for the first 7-10 days, serological tests are often negative. The atypical pneumonia with patchy infiltrate which seems worse than the patient appears is diagnostically mycoplasma along with cold agglutins. Patient is 25 years old which makes her an older adult and so she only has pneumonia, otherwise also bronchitis. The penicillin G was useless because no cell wall. The classic treatment is a macrolide.
What first diagnostic test would you do to detect primary syphillus?
Obtain serum and test for anti-phospholipid antibodies. (reagins) RPR or VDRL because upon syphillus infection, the body produces antibodies to lipoidal antigens that are present in a wide array of host tissues.
Then you would do a confirmatory test via the FTA-ABS which detects for specific antibodies to syphillus. If that is positive, thats what you’d expect.
What is the structural feature that is really unique to spirochetes (syphillus, lyme disease, relapsing fever, leptospirosis.
Flagella which lie inside the outer membrane.
What distinguishes the latent phase of treponema palladium infection?
Serologic tests will come back positive (RPR, FTAab) but there will be no clinical findings (no rash, genital lesions, inflammation or discharge).
They are infectious but some people can stay at this stage untreated
What is the main diagnostic test for Lyme’s disease?
A 2 pronged approach. You do a serologic test (testing serum) which is first an Elisa and if positive, a Western blot).
What are the three virulence factors of Bordetella pertussis that help it attach and prevent clearance by phagocytes? What are the 3 toxins?
- BrkA protein: complement resistance
- Fimbriae: phase variation
- Filamentous hemagglutinin - binds integrins on ciliated epithelial cells
- Tracheal cytotoxin (trachtor): stimulates IL-1 mediated killing of ciliated epithelium
- Adenylate cyclase toxin (edema factor shield) - causes so much edema, it compromised phagocyte function
- Pertussis toxin (bow tie) : systemic effects like lymphocytosis (alot of lymphocytes), sensitization to histamine and enhanced insulin secretion
What are the special growth requirements for H.influenza?
NAD + hemin
and chocolate agar
what does hAEMOPhiluS influenza stand for
A: arthritis E: epiglottits - can be fatal M: meningitis O: otitis media P: pneumonia S: sinusitis
All nosocomial pathogens have multiple antibiotic resistance mechanisms, what makes Klebsiella unique?
It is HIGHLY encapsulated
Bloody: currant jelly sputum.
Distinguishing features of Enteropathogenic yersinia
Grow at 4 degrees so its important for refrigerated foods, blood products.
Type III system blocks phagocytosis. (turkey baster)
It travels from the intestine to local lymph nodes. The painful inflammation can mimic appendicitis
Like salmonella it is a penetrating disease so early may be diarrhea but it will leave the intestine and cause systemic illness. Unlike salmonella, this one travels out to lymph nodes while salmonella travels systemically.
What is the diagnositic test for H. pylori and the treatment
Do a breath test. Make the patient consume radioactive 14 Carbon. H.pylori is urease positive. You measure the exhaled Co2.
Treatment is 3 membered:
- Bismuth salt
- Proton pump inhibitor.
What is Guillian Barre syndrome and what causes it?
Guillian Barre is ascending paralysis (look there are no d’s in the word but has A’s)
Campy = curved
Selective medium too - campy-BAP
Which bacteria produces Verotoxin?
Verotoxin aka, Shiga like toxin is therefore EHEC. Predominant serotype O157:H7
Inflammatory enteritis and HUS
Shiga toxin cleaves the RNA of large ribosomal subunit causing it to be inactive.
HUS: microvascular damage in kidney and red cell lysis
Cause shigella and nontyphoidal salmonella overall, invades and kills cells of intestinal mucosa.
What are the following
Perinatal mortality Neonatal mortality Post-neonatal mortality Infant mortality Child mortality
Perinatal: first 7 days Neonatal: first 28 days Post-neonatal: first 28-365 days - mostly due to diarrhea and respiratory infections Infant morality: first year of life Child: 5 year of life
What are three important viruses to know about for disease and water shit
- Polio: virtually eliminated but still exists in Africa and Central/South asia. It is enteric virus
- Rotavirus: the most common cause of severe,dehydrating diarrhea. More than 500,000 deaths in children aged five or younger.
- Norovirus: a leading cause of foodborn disease outbreaks. Millions of acute gastroenteritis
How long should you wait before entering a room a patient with Tb was in (assuming 4-6 airchanges per hour)
100 minutes, around 2 hrs is safe
What does the BCG vaccine do and don’t
It will protect severe complications of Tb in young children but nothing past that. Can result in false positives for tuberculin skin tests.
What are approaches to decolonization
- Mupirocin nasal ointment
(mostly bacteriostatic, it binds isoleucyl tRNA synthetase which will disrupt protein synthesis)
-develops high and low level resistance
Low level: point mutation in ileS
High level: new kind of ileS - mupa.
- Chlorhexidine gluconate
Encapsulated bacteria are positive Quellung and worrisome for sickle cell patients SHiNE SKiS
Strep agalactiae and pyogenes
Person with a local bacterial infection develops into fever and hypotension. What confirms Toxic Shock syndrome over septic shock?
If you get a negative blood culture that rules out septic shock.
Toxic shock: toxin gets into blood stream causing flood of cytokines
Septic shock: blood stream infection, would show up on blood culture.
A women has a bloodstream infection of staph aureus. What initiates her septic shock?
Binding of peptidoglycan and teichoic acid to TLRs.
Blood cultures so an alpha hemolytic gram positive. An IV drug user upon cardiac imaging shows masses of bacteria on the tricuspid valve. What is the insulting agent
Contamination of a needle or injection site with oral flora (S. Viridians)
What is a gram positive cocci that has remained relatively sensitive to penicillin G and what are examples of ones that aren’t
S. pyogenes (baker holding pencil)
What resulted in “intermediate resistance” of the S. pneumoniae?
Recombination via transformation with DNA from a resistant source resulting in PBP genes that are mosaics of sensitive and resistant sequences.
What makes Enterococcus more important then Group D streptococcus?
Enterococcus has more antibiotic resistance genes.
What is the antigenic component of the S. pneumonia vaccine?
Purified capsular polysaccharides
PPV - 23 valent, protects against older people
PCV13 - conjugated to nontoxic diptheria toxin (a protein) used only for children.
What feature of S. aureus makes it easily transmitted in a hospital setting
Resistance to heat, cold and drying
Lancefield groups, noted A, B, C, and D is specified based on what bacterial component?
Cell associated carbohydrate (C-group)
How does protein A aid in virulence.
Protein A binds the Fc region of igG, decreasing opsonization.
In a smear of an abscess, what type of white blood cell would be expected to predominate.
An isolate of staph aureus is fully-resistant to all penicillins and cephalosporins, what mechanism is most responsible for this resistance.
Insertion of a gene into S. aureus chromosome which codes for a penicillin binding protein to which no currently used beta-lactam binds.
What is a psychrophile and gimme examples
Bacteria capable of surviving and reproducing in cold temps.
What is a microaerophile:
Microaerophile: (Legionella) grows bets at below atmospheric concentrations of oxygen
Capnophile: grows best in a high CO2 atmosphere. (Neisseria)
What is high level bacterial classification based on
The DNA sequence of genes that encode ribosomal RNA>
What is the specific advantage and disadvantage of:
Direct microscopy is rapid but requires presence of a lot of bacteria
What is the specific advantage and disadvantage of:
Advantage: highly specific if appropriate reagents are used
Disadvantage: prone to false positives by contamination
What is the specific advantage and disadvantage of:
testing for immune response to pathogen?
Useful for organisms that are difficult to culture
Disadvantage is that it takes several days to compare samples for detection
What is the specific advantage and disadvantage of:
Detecting antigens via specific antibodies?
Its highly specific if proper reagants are used.
It is however up to the judgement of the clinician since all antigens cannot be tested.
What is the specific advantage and disadvantage of:
Isolation of the organism by culture
High sensitive, can get single viable colonies, provides material for metabolic testing and can test antibiotics on. Problem is it will take a while, growth may be slow and you have to test a bunch of medium.
How would you culture Neisseria meningitidis taken from a sterile site compared to one highly contaminated with normal flora
Chocolate agar vs Thayer Martin which contains NAD, hemin, and antibiotics that will kill normal flora.
When would you use MacConkey agar?
It contains lactose and pH sensitive dyes and inhibits growth of gram positives. iF you wanted to culture E.coli from stool (which will contain tons of gram negative and positive, use MacConkey. E.coli are also lactose fermenters.
Klebsiella also lactose fermenters
Describe the vaccine for Hib
Its purified H.influenza capsular polysaccharide covalently bound to dipthera toxoid
How is pertussis and haemophilus transmitted?
How is respiratory infection Legionella transmission different?
By respiratory droplets
Legionella is found in the environment (especially warm bodies of water). Aerosal from water supply can do this
Describe pertussis vaccine.
Its an acellular vaccine. Its just the toxoid with parts of virulence factors (antigens)
Inhalation of aerosolized water from a source containing protozoa puts you at risk for what microbe
What does Type III secretion system do for Yersinia?
It paralyzes phagocytes and so prevents ingestion of bacteria
Francisella tularensis is diagnosed primarily by serology. Why is that?
Francisella is so infectious that few laboratories have facilities to culture it safely.
Why is Francisella tularensis able to transmit via aerosol?
Francisela has an extremely low infectious dose, only a few bacteria are needed.
A gram negative rod is cultured from burn wounds. Colonies on MacConkey agar are colorless. The organism is known to not ferment any carbohydrates. On broth based agar colonies there is an intense blue green color. What is it
Why do capsules promote serious disease?
It prevents phagocytosis by neutrophils
For which disease is the diagnosis based on specific antibodies detecting the toxins?
C. dificile infection aka Antibiotic associated colitis
EIA detects toxins A and B
A: binds brush border causes inflammation and watery diarrhea
B: compromises cytoskeletal integrity and causes pseudomembrane that will cover the colon.
Cells of pathogenic Gram negative bacteria have common pili. What is the role of common pili?
Adherence of bacteria to mammalian cells.
What does the heat stable peptide of E.coli do?
It stimulates guanyl cyclase resulting in profuse water diarrhea
How does the shiga toxin, or verotoxin act to cause hemolytic uremic syndrome
Cleave the RNA of 80S ribosomes.
A sexually active woman develops a urinary tract infection that reaches the kidneys (pyelonephritis. Which class of pathogen is likely the cause?
How is shigella transmitted and what aspect promotes its spread between children
It is spread from people and its resistant to stomach acid and has low infectious doses.
What is the most widespread cause of resistance in Salmonella to penicillins?
Presence of plasmids that encode beta-lactamases
What distinguishes Typhoidal salmonella from non typhoidal Salmonella which allows it to spread mroe widely?
Presence of Type III secretion system that enables survival inside the phagocytic vacuole of macrophages
Which organism is most likely to cause chronic gastritis?
What observation would be seen with H.pylori on biopsy?
Curved or spiral bacteria seen in biopsy after silver staining.
Which site of the body is a predominant site of carriage of meningococci.
What conditions would you use to culture the microbe that cases septic arthritis, with gram negative diplococci?
Thayer martin agar, elevated CO2.
Leukopenia, thrombocytopenia and anemia. Deer is the reservoir and is transmitted by ticks
A women has aortitis. She has no mucosal ulcerations.
Her VLDR is negative but her FTA-ab test is positive, whats up?
The FTA-abs remains positive for life with or without antibiotic therapy. The VDRL test detects less specific reaginic antibodies, which decline with successful treatment, but also sometimes decline without treatment in tertiary syphilis. Therefore, based on the serologic data, this patient could have very early primary syphilis or untreated tertiary syphilis. The symptoms are consistent with tertiary syphilis.
Why does detecting very low probability events have a low Positive Predictive value?
That increases the number of false positives and so if you have a positive result, the predictive value is lower.
What is causing the crepitis in C. perfinges?
The H2 gas because although the CO2 gas can be reabsorbed, H2 does not get efficently reabsorbed into the tissue
Distinguish the two kinds of M. leprae
Tuberculoid: few lesions, few bacteria in them, caused by TH1 response.
Lepromatous: extensive tissue damage, with many spreading lesion which contain large numbers of bacteria. They are anergic to skin testing evidenced by inactivated cell mediated immunity.
Antibiotic for almost 5 years!
After eating food, students develop nausea, vomiting and abdominal cramping but no diarrhea. What is the agent
3 day fever, headache and a nonproductive cough. Penicillin did not work. Gram staining only showed normal flora
Swollen inguinal lymph node with fever of 104. Gram negative rods and successfully treated with streptomycin. Aspirtate sent to CDC
Produces a toxins that include phospholipases and enzymes that rapidly destroy tissue
aka Lecthicinase (phospholipase), lyses red blood cells.
Pneumonia. He is overweight smoker and drinks alot. Sputum has lots of neutrophils but couldnt find anything on Sheep blood and chocolate agars. Only on a special medium did they find tiny slender gram negative rods.
only known lyme virulence factor
What are the components of DTaP
D- diptheria antitoxin, it neutralizes the circulating toxin
T-tetanus: vaccine linked to dipthera protein. Also to bind the toxin
Acellular pertussis: virulence factors of pertussus, The fimbrae, pertussis toxoid,
Bipolar staining - safety pin
Hemolysin, PVL, staphylokinase
- Yersinia pestis
- S. aureus
What is similar between the Hib vaccine and S.pneumonia vaccine and Meningitis vaccine
Both are linked to diptheria toxin.
The difference is Hib is capsule polysaccharide and S.pneumonia is just polysaccharide with age distinctions, PPV13 for children.
meningitis is also capsular polysaccharides conjugated to diptheria toxoid.
Abscess drainage from his skin after a splinter reveals neutrophils and clumps of bacterial filaments, they stain Gram positive but irregularly along their lengthey grow in aerobic culture.
Lives in the soil and water. Gets it through respiration or lesion.
Oral abscess drainage showed huge numbers of neutrophils with weakly staining, gram positive filaments. They grew on anaerobic culture.
Normal flora of mouth, GI, respiratory tract and female genitourinacy tract. So anywhere along there.
Treatment is penicillin