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Which bugs grow pink colonies on MacConkey agar?

Teset with MacConKEE'S agar







What bugs ferment Lactose?

Which one does it really fast and why? 

Lactose is KEE

Klebsiella, E. Coli, Enterobacter

Klebsiell and E.Coli are fast

E.Coli has a B-galactosidase that breaks down lactose into glucose and galactose


IN EMB agar, we see lactose fermenster growing as purple/black colonies. 

Will show up as purple colonies with a green sheen



Gram-negative diplococci. Both ferment glucose and produce IgA proteases.



N. Gonorrhea is a huge pain the ass. What diseases does it cause?

Why can't we make a vaccine for it?

How is it trasmitted? Can we prevent it's transmission?

Causes gonorrhea, septic arthritis, neonatal conjunctivitis, pelvic inflammatory disease (PID), and Fitz-Hugh–Curtis syndrome

No vaccine due to antigenic variation of pilus proteins

Sexually or perinatally transmitted

Condoms sexual transmission. Erythromycin ointment prevents neonatal transmission

Treatment: ceftriaxone + (azithromycin or doxycycline) for possible chlamydial coinfection 


Young lady come to office with horrible pain in her left knee. It is warm and erythematous. During her social history she admits to having unprotected sex several weeks ago and thought she had a yeast infection for which she got treatment from her phamacist but it hasn't gone away. 

What is the Dx?

What are some other complications that present with this disease?

What should we tx her with?

Dx is Neisseria Gonorrhea

Presents with discharge that women may mistake for yeast infection. See PID which may lead to infertility and can cause septic arthritis, causing her knee pain. 

Tx: Ceftriaxone (+Azihtromycin or Doxyclcine to cover for Chlamydia)


Your friend's brother is back home from college and has been feeling like shit. He has fever with joint pain and say's it hurts to turn his head. He prefers to stay in his room in the basement as the light makes his headache worse. When you stop over to see him, you notice he has a dark rash on his lower legs and tell him he needs to get to the ER NOW! What is the DX?

What is a severe complication from this?

How do you tx this pt?

What should you and your friend take to prevent getting this?

Neisseria Meningiditis: you can get meningococcemia and TTP form this and in bad siutaitons Waterhouse-Friderichsen syndrome or even DIC

Treatment: ceftriaxone or penicillin G 

Rifampin, ciprofloxacin, or ceftriaxone prophylaxis in close contacts



What is the difference between N. Meningitis and Gonorrhea?


Maltose fermentation?

Glucose fermentation?


Meningitis: POlysaccharide capsule, ferments glucose AND maltose and transmitted via oral and respiratory secreations

Gonorrhea: NO capsules, CANT ferment maltose (can glucose) and sexually transmitted


This small Gram (-) rod is resposible for lots of diseaes and transmitted via aersolization. 

Makes and IgA protease

What diseases does it cause?

What do we culture it on?

HaEMOPhilus influenzae 

Causes Epiglottitis, Meningitis, Otitis Media, Pneumonia

Culture on Chocolate agar with factors V (NAD+) and X (hematin)


Little boy comes in with bad sore throat and difficulty breathing. You take a xray and it's posted below.

What medications do you prescribe for this pt?

What would you give if this were to cause meningitis?

Treat mucosal infections with amoxicillin +/− clavulanate.

Treat meningitis with ceftriaxone. Rifampin prophylaxis for close contacts. 


What do we give children to prevent epiglotitis?

What is special about this vaccine?

When is it given?

Vaccine contains type b capsular polysaccharide (polyribosylribitol phosphate) conjugatedto diphtheria toxoid or other protein. Given between 2 and 18 months of age.

 Does not cause the flu (influenza virus does). 


 A group of individuals comes down with unilateral lobar pneumonia. The pt had a fever and GI disturbance and are crrently hyponatermic. The doctors make a diagnosis based on an antiG they detected in the pts urine. 



How would you culture this organims?


Dx: Legionella pneumophila 

Tx: Macrolide or Quinolone

Gram-negative rod. Gram stains poorly—use silver stain. Grow on charcoal yeast extract culture with iron and cysteine.


Weird stuff I never knew about Legionella, but hey..

 Detected by presence of antigen in urine. Labs may show hyponatremia.

(remember also causes Pontiac fever! milder form!)


Aerobic, motile, gram-negative rod. Non-lactose fermenting, oxidase ⊕. Produces pyocyanin (blue-green pigment A ); has a grape-like odor. Produces endotoxin (fever, shock) and exotoxin A (inactivates EF-2). 

Pseudomonas aeruginosa 


PSEUDDOmonas is associated with: ƒ

ƒ Sepsis
ƒ Otitis Externa (swimmer’s ear)
ƒ UTIs

ƒ Drug use
ƒ Diabetes
ƒ Osteomyelitis (e.g., puncture wounds) 


You are treating a young girl in the PICU for severe 3rd degree burns and damage to the lungs for inhalation. She is feverish and severily ill. She has ulcers and indurations all around the burns and are discolored. What is the Dx and what can you tx it with?

Pseudomonas Aeruginosa


Extended-spectrum β-lactams (e.g.,piperacillin, ticarcillin, cefepime)

ƒ  Carbapenems (e.g., imipenem, meropenem)

ƒ  Monobactams (e.g., aztreonam)

ƒ  Fluoroquinolones (e.g., ciprofloxacin)

ƒ  Aminoglycosides (e.g., gentamicin,tobramycin)

ƒ  For multidrug-resistant strains: colistin,polymyxin B


Ecthyma gangrenosum—rapidly progressive, necrotic cutaneous lesion caused by Pseudomonas bacteremia. Typically seen in 

immunocompromised patients 


may contribute to chronic pneumonia in cystic fibrosis patients due to biofilm formation.

D/t infection with pseudomonas aeruginosa

Mucoid polysaccharide capsule


Name the virulence factors responsible for the following disease states

1. Cycstitis and Pyelonephritis

2. pneumonaie adn neonatal meningitis

3. Septic shock

1.  Fimbriae—cystitis and pyelonephritis;

2. K capsule—pneumonia, neonatal meningitis

3. LPS endotoxin—septic shock. 


Microbe invades intestinal mucosa and causes necrosis and inflammation. Clinical manifestations similar to Shigella. Very invasive and causes dysentary




1. Produces heat-labile and heat-stable enteroToxins. No inflammation or invasion. 

2. No toxin produced. Adheres to apical surface, flattens villi, prevents absorption. 


ETEC: travelers diarrhea

EPEC: Diarrhea, usually in children (Pediatrics). 


What bug is responsible for the following triad: anemia, thrombocytopenia, and acute renal failure

This toxin is simular to Shiga toxin

What is the bug responsible and what is the mechanism of the disease process?

EHEC O157:H7 

HUS: triad of anemia, thrombocytopenia, and acute renal failure due to microthrombi forming on damaged endothelium-->mechanical hemolysis (with schistocytes on peripheral blood smear), platelet consumption, and decraesed renal blood flow; microthrombi consume plats leading to thrombocytopenia 


Alcholic is brought to the ER  passed out. He has labored breathing and when he comes to you find out he's homeless and CXR shows lobar pneumonia. 

He coughs up globoid, bloody mucus. What is the dx?

Does this bug have a capsule?

Where is this bug usually found?




An intestinal flora that causes lobar pneumonia in alcoholics and diabetics when aspirated. Very mucoid colonies caused by abundant polysaccharide capsules.

Dark red “currant jelly” sputum (blood/mucus).

Also cause of nosocomial UTIs.


What are the 4 A's of KlebsiellA:

4 A’s of KlebsiellA:

Aspiration pneumonia

Abscess in lungs and liver



Major cause of bloody diarrhea, especially in children. Fecal-oral transmission through person- to-person contact or via ingestion of poultry, meat, unpasteurized milk. Contact with infected animals (dogs, cats, pigs) is also a risk factor. 

camplyobacter jejuni


Describe in as much detail as you can Campylobacter jejuni

What does it condition does it commonly procreed?

Big cause blood diarrhea  in kids

fecal oral transmission and foods like poultry, meat, unpast milk

S shaped, oxidase + and grows at 42 degress (hot a a campfire)

Preceeds Guillan Barre and reactive arthritis


Produces profuse rice-water diarrhea. Endemic to developing countries. Prompt oral rehydration is necessary. 


Mechanism of diesease?

Vibrio cholera

via enterotoxin that permanently activates Gs, INCREASE cAMP. 


Both Salmonella and Shigella are gram-negative bacilli that are_____ fermenters and oxidase ____




can disseminate hematogenously and have flagella with many animal reserviours.

Will produce hydrogen sulfide

Is invasive in intestinal mucosa and causes a monocytic response

Bug responsible?

Do we provide antibiotics?

Does this ferment lactose?


antibiotics may prolong fecal excreation

does NOT ferment lactose


This bug causes diarrhea with cell to cell transmission; NOT hematogenous spread. Doesn't make hydrogen sulfide. Does NOT invade intestinal mucosa and causes PMN infiltration. 

Causitive agent?

Do you provide antibiotics?

Does it ferment lactose?


antibiotics shorten duration of fecal excreation of organism

get bloody diarrhea and does NOT ferment lactose



What properties are unique to Salmonella

ƒ  Poultry, eggs, pets, and turtles are common sources

ƒ  Gastroenteritis is usually caused by non- typhoidal Salmonella 


What are the Four Fs of Shigella?

ƒ Four F’s: Fingers, Flies, Food, Feces

ƒ  In order of decreasing severity (less toxin produced): S. dysenteriae, S. flexneri, S.boydii, S. sonnei

ƒ  Invasion is the key to pathogenicity; organisms that produce little toxin can cause disease due to invasion 


What is the Virulence factor in Typhoid fever?

How does the body fight the diesease?

What symptosm to we see?

How do we tx it and prevent it?

Salmonella typhoid; Endotoxin; Vi capsule 

Infects Primarily monocytes 

Constipation, followed by diarrhea  and causes typhoid fever (rose spots on abdomen, constipation, abdominal pain, fever);

treat with ceftriaxone or fluoroquinolone and prevent: Oral vaccine contains live attenuated S. typhi IM vaccine contains Vi capsular polysaccharide 


Causes gastritis and peptic ulcers (especially duodenal). Risk factor for peptic ulcer, gastric adenocarcinoma, and MALT lymphoma.




 H. Pylori
Curved gram-negative rod that is catalase, oxidase, and urease ⊕ (can use urea breath test or fecal antigen test for diagnosis). Creates alkaline environment.

Most common initial treatment is triple therapy: proton pump inhibitor + clarithromycin + amoxicillin (or metronidazole if penicillin allergy).


What is the mainstay tx for pt that comes in with GERD and has a urease + test?

Most common initial treatment is triple therapy: proton pump inhibitor + clarithromycin + amoxicillin (or metronidazole if penicillin allergy).

for H. Pylor


Three bacteria that are Spiral-shaped bacteria with axial filaments. 

Which one is visualized with analine dyes in light microscopy?

Which is visualized by dark field microscopy?

Includes Borrelia (big size), Leptospira, and Treponema.

Only Borrelia can be visualized using aniline dyes (Wright or Giemsa stain) in light microscopy A due to size.

Treponema is visualized by dark-field microscopy


Surfer in Hawaii is comes down with the 'flu'. He is sore all over but states his calves hurt especially bad. His eyes are red and he looks even more than than usual. 


Leptospira Interrogans

Found in water contaminated with animal urine, causes flu-like symptoms, myalgias (classically of calves), jaundice, photophobia with conjunctival suffusion (erythema without exudate). Prevalent among surfers and in tropics (i.e., Hawaii). 


What is the Initial and later presentation of symptoms from Borrelia Burdorferi?

What is its vector?

What is it's natural reservoir?

Initial symptoms—erythema chronicum migrans B , flu-like symptoms, +/− facial nerve palsy.

ƒ Later symptoms—monoarthritis (large joints) and migratory polyarthritis, cardiac (AV nodal block), neurologic (meningitis, facial nerve palsy, polyneuropathy).

VECtor: Ixodes deer tick 

Natural reservoir is the mouse.



Your uncle is a nature enthusiast but hasn't been up for many adventures lately, he has felt exceptionally sore in his joints lately and thinks his age is just catching up to him. You ask him some questions to see if you can figure out what's going on and he mentins his fingers and toes occasionally feel tingly and the only time he's been sick was a few months ago with the flu. 

What organism is repsonsible?

What do you tx with?

What are some late complications?

Borrellia Burdorferii

Tx: doxycycline, ceftriaxone. 

Worry about AV nodal block

(can present with bilateral facial palsy)


Women presents with painless ulcer on her genitals. You can see an organism for the sample you took using dark field microscopy.

What serologic test do you use to dx?

What specific test do you use to confirm dx?

What do you tx with?

Primary syphillis

serologic testing: VDRL/RPR (non specific)

Confimr with FTA-ABS

Tx: Pen G


Young man comes to clinc with  painless, mucosal, and warty erosions on his nut sack and is freaking out. He states he thought it whatever he had went away a few months ago! You ask him to be more specific and he states he has an open sore on his genitals but it didn't hurt and then it was gone. 



What other signs would cue you in to this disease?

Secodary syphillus= Systemic: Treponema Pallidum: Disseminated disease with constitutional symptoms, maculopapular rash (including palms and soles ), condylomata lata (smooth, moist, painless, wart-like white lesions on genitals); also confirmable with dark-field microscopy. 

Tx with Pen G


A 55 yo woman comes to your clinic. She is in bad shape, walking with an ataxic gait. She is here for a physical and is worried about a growth on her nose. During your physical you note her left eye accomidates but does not react to light. During you history gathering you find out she was a prostitute in her early twenties but she doesn't do that anymore. 

What is this pts Dx?

How will you confirm?

What is she at risk for?

Tertiary syphillis

Dx:  test spinal fluid with VDRL and PCR. 

Risk: aortitis (vasa vasorum), neurosyphillis (tabes dorsalis), stroke in absence of HTN


16 yo girls comes to your clinic and you find out she is 3 weeks pregnant... Along with a baby, the boy she slept with also gave her syphillus.

What do you treat her with?

What risks do you need to warn her about if she doesn't get tx, go into detail!

To prevent, treat mother early in pregnancy, as placental transmission typically occurs after first trimester.

 Presents with facial abnormalities such as rhagades (linear scars at angle of mouth, black arrow in G ), snuffles (nasal discharge, red arrow in G ), saddle nose, notched (Hutchinson) teeth , mulberry molars, and short maxilla; saber shins; CN VIII deafness.



Women comes in complaining of foul smelling lady parts and gray discharge. After dx her you assure her it isn't an STD. 

Whats the Dx and characteristics of organism?


Gardnerella Vaginalis:

A pleomorphic, gram-variable rod involved in bacterial vaginosis (Associated with sexual activity, but not sexually transmitted) 

 Clue cells, or vaginal epithelial cells covered with Gardnerella bacteria (“stippled” appearance along outer margins), are visible under the microscope 

Treatment: Metronidazole or clindamycin. 


Your friend talks about an interesting case she saw in the ID department when she was rotating through a hospital in North Carolina. A young man came in with a rash all over his trunk but said it started on his wrists and ankles. Prior to the rash he had a fever of 101 and a bad headache. 

What is the responsible organism?


Characteristics of organims?

Rickettsia rickettsii= Rocky mountain spotted fever  with tick as vector: get a rash on hands and feet

Tx = Doxycycline

Characterstics: obligate intracellular organims; needs coA and NAD+; cant make it's own ATP


How do you distinguish Rickettsia typhus from Ricketssia Ricketssia?

What about R. Prowazekii?

Rickettsii on the wRists, Typhus on the Trunk. 

Endemic (fleas)—R. typhi.
Epidemic (human body louse)—R. prowazekii. Rash starts centrally and spreads out, sparing palms and soles. 

*all tx with Doxycycline


Patient presents with headache, muscle aches, and fatigue. In a culture you see these berry like inclusions. What is the Dx?

Do you see a rash with this?

Eherlichiosis: Ehrlichia (type of ricketsial disease), vector is tick. Monocytes with morulae  (berry-like inclusions) in cytoplasm. 

Rash is rare, tx with Doxycycline


An 35 yo man comes to the office complaining of persistant SOB and cough for the past two weeks. He works from home, has 2 children and has not significant travel hx except, he laughs, taking his kids to the petting zoo! CXR shows right lobar consolidation. 

What is the most likely Dx?

What is he at risk for if not tx?

How did he aquire this?


Coxiella burnetii= Q fever, no arthropod vector. Spores inhaled as aerosols from cattle/sheep amniotic fluid. Presents as pneumonia.

May cause endocarditis: Most common cause of culture ⊝ endocarditis

Got while at the petting zoo; Q fever is Queer because it has no rash or vector and its causative organism can survive outside in its endospore form. Not in the Rickettsia genus, but closely related. 


Obligate Intracellular organism that CANNOT make it's own ATP and causes mucosal infections. Leads to PID, follicular conjunctivitis and reactive arthritis. 


How is this dx?



Dx: Chlamydia

Lab diagnosis: cytoplasmic inclusions seen on Giemsa or fluorescent antibody–stained smear.

Tx = Azithromycin

(The chlamydial cell wall lacks classicpeptidoglycan (due to reduced muramic acid), rendering β-lactam antibiotics less effective)


Parts of Chlamydia:

_______ (small, dense) is “Enfectious” and Enters cell via Endocytosis-->  

transforms into _______ Replicates in cell by fission; Reorganizes into elementary bodies. 

ƒ Elementary body

ƒ Reticulate body


Chronic infection, cause blindness due to follicular conjunctivitis in Africa. 

Chlamydia trachomatis : Types A, B, and C 


Responsible for: Urethritis/PID, ectopic pregnancy, neonatal pneumonia (staccato cough) with eosinophilia, neonatal conjunctivitis. 

Chlamydia trachomatis : types D-K


small, painless ulcers on genitals--> swollen, painful inguinal lymph nodes that ulcerate (buboes). Treat with doxycycline. 



Lymphogranuloma venereum—

Chlamydia trachomatis  

Types L1, L2, and L3 




25 yo male comes in with bad headeache, and a nonproductive cough. His commanding officer said he should get looked at. CXR show diffuse interstitial infiltates that would indicate the pt should feel much worse then they do. 

You culture the sputum and see they can agglutinate and lyse RBCs and there is a high titer of cold agglutinins (IgM)


What do you tx with?

How does this gram stain?





Mycoplasma pneumoniae ; walking pneumoniae

Treatment: macrolides, doxycycline, or fluoroquinolone (penicillin ineffective since Mycoplasma have no cell wall). 

*No cell wall. Not seen on Gram stain. Pleomorphic 


Classic cause of atypical “walking” pneumonia (insidious onset, headache, nonproductive cough, patchy or diffuse interstitial infiltrate). X-ray looks worse than patient. High titer of cold agglutinins (IgM), which can agglutinate or lyse RBCs. Grown on Eaton agar.;  Frequent outbreaks in military recruits and prisons


What is the infection dose for Shigella?

What about Salmonella?



C. perfringens?

Shigella = infectious dose as low as 10 organims!

Salmonella, vibrio, C.perfringens and E.Coli are around 100,000 to 10000000000


What bug are pts with Sickel cell susceptible to that causes osteomylitis and what is the virulence factor?

Salmonella: virulence is Vi antigen: protects it from opsonization and phagocytosis 

Salmonella = gram (-) nonlactose fermenting, oxidase negative, motile gram (-) bug


Why is Thayer-Martin selectie medium used to isolate Neisseria species from clinical cultures?

= a chocolate (heated blood) agar with Vancomycin (inhibits G+), Polymyxin (to inhibit G-) Nystatin (to inhibt fungi) and Trimethoprim (to inhibit growth of other Gram -s like Proteus)

This will allow Neisseria to grow thus we can isolate it.