MICRO Flashcards
7 species included in the Enterobacteriaceae
E. coli Salmonella Shigella Klebsiella Enterobacter Serratia Proteus
5 lab characteristics of Enterobacteriaceae
Capsular K antigen – virulence Flagellar H antigen All ferment glucose Oxidase -
Does ETEC cause a fever?
Nope. It does not invade the intestinal wall.
Most common cause of gram negative sepsis
E. coli (#2 is Klebsiella)
Most common cause of food-associated diarrhea in developed countries
Salmonella enterica and enteridis Poultry, eggs, reptiles
Which bug do you avoid treating with antibiotics?
Salmonella –may prolong carrier state in salmonella GI tract infections
Bug associated with causing Reiter syndrome
Shigella flexneri
Diarrhea caused by gram - nonmotile organism that does not ferment lactose
Shigella
2 organisms associated with rice-water stools
Vibrio cholera ETEC
Diarrhea transmitted from pet feces
Yersinia enterocolitica
Diarrhea caused by gram - motile organism that does not ferment lactose
Salmonella
Diarrhea caused by gram - lactose fermenting bacteria with no fever
E. coli
2 organisms associated with diarrhea + recent ingestion of water from a stream
Giardia lamblia Entamoeba histolytica
4 organisms known to cause infections in the mouth of AIDS patients
Candida albicans HSV CMV EBV (oral hairy leukoplakia)
3 structural genes that code for HIV proteins
pol (Reverse transcriptase env (gp120, gp41) gag (p24)
32 y.o. male patient went camping in northern CA 2 weeks ago, had a 2 day stint of diarrhea and now presents with sx of liver damage and jaundice. Whats the infecting organism?
Entamoeba histolytica
Classic triad associated with congenital Toxoplasmosis
Chorioretinitis Hydrocephalus Intracranial calcifcations
Organism associated with hemoptysis
Paragonimus westermani
2 organisms that can lead to microcytic anemia
Acylostoma Necator
Organism associated with pigmented gallstones, cholangiocarcinoma
Clonorchis sinensis (undercooked fish)
Organism associated with liver cysts and how is it acquired
Echinococcus granulosus Ingestion of eggs from dog feces
Associated with Eosinophilic Loeffler’s pneumonitis and how it is treated
Ascaris Lumbricoides Treated with bendazoles or pyrantel pamoate
Most common cause of pneumonia in children 1-year-old or younger
RSV
Most commo ncause of pneumonia in the neonate (B-28 days)
Group B strep or E. coli
Common cause of pneumonia in patients with other healt hproblems
Klebsiella pneumonia
Common bacterial cause of COPD exacerbation
H. influenzae
Intra-alveolar exudate is found on CT. What is the causative organism?
S. pneumo usually Klebsiella This is LOBAR pneumonia.
Patchy distribution of acute inflammatory infiltrates involving >1 lobe. What are the 4 most likely causative organisms?
S. pneumo S. aureus H. influenzae Klebsiella
Diffuse patchy inflammation localized to interstitial areas involving >1 lobe. What are the 4 most likely causative organisms?
Viruses (influenza, RSV, adenoviruses) Mycoplasma Legionella Chlamydia
Air fluid levels are seen on CXR in an epileptic. What is the dx and what are the most causative organisms?
Lung abscess due to S. aureus or anaerobes (Bacteroides, Fusobacterium, Peptostreptococcus)
6 organisms that do not take gram stain.
These Rascals May Microscopically Lack Color. Treponema Rickettsia Mycobacteria (high lipid content in cell wall detected by carbolfuchsin in acid fast stain) Mycoplasma Legionella Chlamydia
Which bacteria are encapsulated? (6)
Some Killers Have Nice Shiny Bodies S pneumo K pneumo H influenzae B N meningitidis Salmonella Group B strep
What does the alpha toxin of S. aureus do?
Hemolysis
What does the beta toxin of S aureus do?
Sphingomyelinase
Which exotoxin contains a lecithinase that causes gas gangrene?
Alpha toxin of C. perfringens. The alpha toxin is a phospholipase that degrades tissue and cell membranes. The degradation of PLC causes myonecrosis and hemolysis (double zone of hemolysis on blood agar.)
This exotoxin destroys leukocytes.
Leukocidin of S. aureus
This exotoxin blocks the release of the inhibitory neurotransmitter glycine
Tetanospasmin
What 5 bacteria secrete enterotoxins (exotoxin that causes water and electrolyte imbalances of intestinal epithelium resulting in diarrhea)?
Vibrio cholera ETEC Staph aureus Salmonella Shigella
Name 5 bugs that stain with giemsa.
Certain Bugs Really TRY My Patience Chlamydia Borrelia Rickettsia TRYpanosomes Plasmodium
What does PAS stain?
Periodic acid Schiff stains glycogen and mucopolysaccharides (remember it stains T. whipplei)
Ziehl-Neelsen is used to stain what organisms?
Acid-fast organisms like Nocardia, Mycobacterium, Cryptosporidium, Isospora, Cyclospora, etc.
India ink stains what organism?
Cryptococcus neoformans (#1 cause of AIDS meningitis)
Silver stain is positive in what 3 organisms?
Fungi (such as Pneumocystis) Legionella H. pylori
Only gram + bacteria with an endotoxin
Listeria
Amish patient presents with her 5 year old son. Examination reveals gray pseudomembranes on the pharynx. What is the mechanism of the exotoxin used by the causative organism?
This is diphtheria toxin which inactivates elongation factor 2, inhibiting protein synthesis.
73 y.o. with severe exacerbation of COPD is on a ventilator and dies of a bacterial pneumonia. What is the mechanism of the toxin produced by the causative organism?
P. aeruginosa releases Exotoxin A which inactivates elongation factor 2, inhibiting protein synthesis and causing host cell death.
7 year old boy presents with blood and protein in the urine. CBC reveals thrombocytopenia. His mom states he had several episodes of bloody diarrhea about a week ago at a church picnic where he ate 6 hamburgers. What are the two possible causative organisms and what is the mechanism of the toxin used by these organisms?
This is HUS caused by either Shigella or EHEC (O157:H7 especially). These produce Shiga toxin or shiga-like toxin, which inactivates the 60S ribosome by removing adenine from rRNA, inhibiting protein synthesis. This enhances cytokine release, causing HUS. However, EHEC does not invade host cells while Shigella does.
Patient presents with watery diarrhea after recently visiting Mexico. Gram stain reveals gram negative rods that ferment lactose. What is the MOA of each toxin produced by this organism?
ETEC. Heat labile toxin overactivates adenylate cyclase (increases cAMP), thus increasing Cl- secretion in gut and H2O efflux. The heat-stable toxin overactivates guanylate cyclase (increases cGMP), thus decreasing the reabsorption of NaCl and H2O in the gut. These cause watery diarrhea, also known as Montezuma’s revenge. :)
Patient presents with a painless ulcer covered in black eschar on his face.
He’s a wool sorter. What is the exotoxin responsible for this lesion?
Edema factor from bacillus anthracis mimics the adenylate cyclase enzyme, increasing cAMP and causing increased fluid secretion. Characteristic edematous borders of black eschar lesion.
Patient presents with diffuse watery diarrhea for the past 3 days. Gram stain reveals gram negative curved rods that are oxidase + and grow in alkaline media. MOA of the toxin produced by the causative organism?
This is Vibrio cholerae and it produces the cholera toxin. This toxin overactivates adenylate cyclase (just like the heat-labile toxin of ETEC) by permanently activating Gs, thus increasing Cl- secretion in the gut and H2O efflux.
Amish patient presents with her 3 year old son who has a fever and a seal bark cough for the past 100 days. What is the mechanism of the exotoxin produced by the causative organism?
Bordetella pertussis produces the pertussis toxin, which overactivates adenylate cyclase (increasing cAMP) by disabling Gi, impairing phagocytosis which permits survival of the microbe. However, the toxin may not actually be the cause of the cough.
Name 4 organisms with exotoxins that increase cAMP.
CAMP.
Cholera
Anthrax
Montezuma’s revenge (ETEC)
Pertussis
A lady presents with fever, shock, and a diffuse rash over her body after realizing she left her tampon in for 6 days. What is the MOA of the toxin produced that is causing these symptoms, and name one other toxin that can cause similar symptoms.
This is toxic shock syndrome. TSST-1 from S. aureus and Exotoxin A from S. pyogenes are both superantigens that bring MHC II and TCR in proximity to outside of an antigen binding site, which causes an overwhelming release of IFN-y and IL-2.
Describe the 3 components of the main pathogenesis of endotoxins.
- Activate macrophages –> release of Il-1, TNF, and NO (cause fever and hypotension.)
- Activate complement (C3a, causing hypotension and edema; C5a, causing neutrophil chemotaxis)
- Activate tissue factor –> coag cascade – > DIC
First AID has a fun mneumonic
Edema (C3a)
Nitric oxide (hypotension; from macrophages)
DIC/Death (not that fun)
Outer membrane (where the LPS are found that contain endotoxins)
TNF-a
O-antigen
eXtremely heat stable (kind of a copout…)
IL-1 (fever)
Neutrophil chemotaxis (C5a)
What 3 organisms are most commonly implicated in sub-acute endocarditis?
Viridans strep (S mutans)
Enterococci
Coagulase negative staph (S. epidermidis)
Most common causative organism in mastitis.
S. aureus
Most common aerobic skin flora
S. epidermidis
3 infections caused by both S. pyogenes and S. aureus
Folliculitis
Cellulitis
Impetigo
You swab the vagina of a pregnant woman at 35 weeks. The organism is Hippurate Test positive and produces CAMP factor. If you did not administer prophylactic penicillin, what 3 possible disease manifestations would occur in the neonate?
Pneumonia
Meningitis
Sepsis
This is Group B Strep (S. agalactiae)
These gram + organisms are optochin sensitive, and the most common cause of what 3 diseases?
S. pneumo is the most common cause of
Meningitis in adults
Otitis media in children
Pneumonia in adults
Sinusitis
What is the virulence factor of S. aureus and its MOA?
Protein A binds the Fc region of Ig, preventing opsonization and phagocytosis.
IgA protease is produced by what 3 organisms in order to colonize respiratory mucosa?
S. pneumo
H influenza B
Neisseria
Most common cause of osteomyelitis
S. aureus
Organism that causes cervical lymphadenitis in children
Mycobacterium scrofulaceum
This organism causes pulmonary TB-like symptoms in COPD patients.
Mycobacterium kansasii
What does a negative PPD skin test indicate?
Immunocompromised
Steroids
Sarcoidosis
Malnourished
Or no infection (duh)
Patient has keloids and facial disfigurement. What is the causative organism?
This is Yaws caused by Treponema pertenue.
What is a Charcot joint?
This is usually in syphilis or diabetic patients. Their nerves are damaged so they cannot detect proprioception or pain so the joints get severely damaged and disfigured –seen especially in ankles.
What is the Rickettsial triad of symptoms?
Headache, fever, rash
A neonate is born with pneumonia and has a staccato like cough. What infection did his mother most likely have?
Chlamydia serotypes D-K. This could also cause ectopic pregnancy due to the extensive scarring of the fallopian tubes.
This organism presents as cytoplasmic inclusions seen on Giemsa or fluorescent antibody-stained smear. Additionally, the cell wall lacks muramic acid.
Chlamydia
4 organisms that cause a rash on the palms and soles.
Coxsackievirus A (hand foot and mouth)
Rocky Mountain Spotted Fever
Secondary Syphilis
You drive CARS with your PALMS AND SOLES. :)
A patient presents with fever and headache. Labs reveal monocytes with a morula in the cytoplasm. How did they get this infection?
Tick –erlichiosis.
Describe VDRL and name 4 causes of false positives.
VDRL detects non-specific antibody that reacts with beef cardiolipin. False positives can be caused by:
Viruses (mono, hepatitis)
Drugs
Rheumatic fever
Lupus, leprosy
Patient presents with fatigue, weakness, and jaundice. Upon examination, you note bilateral cojunctivitis. How did the patient most likely acquire the infection?
Swimming in animal urine in Hawaii. This is leptospirosis-caused Weil’s disease, which is the severe form. It causes jaundice, azotemia, fever, hemorrhage, and anemia. Leptospirosis also causes flu-like symptoms and photophobia with conjunctivitis.
How does gram negative sepsis cause decreased TPR?
LPS in gram negative organisms acts on iNOS, which converts L-arginine to NO. NO activates guanylyl cyclase, converting GTP – > cGMP. cGMP activates myosin phosphatase, which dephosphorylates myosin phosphate, relaxing smooth muscle cells.
An HIV patient with CSF showing 75/mm3 lymphocytes suddenly dies. Yeast is identified in the CSF. What is the most likely dx?
Cryptococcus meningitis
A patient recently returns from their trip to the Ohio River valley presenting with cough, fever, and malaise. They mention they spent their time exploring caves. Where can you expect to find the causative organism?
Histoplasma capsulatum hides within the macrophages and appears smaller than RBCs on blood smear.
A patient presents to the office complaining of cough, fever, and malaise for the past 10 days with a newer appearance of a rash. Laboratory dx reveals broad based budding yeast that are roughly the same size as RBCs. Where is the patient most likely from?
Blastomycosis is usually found in states east of Mississipi River and Central America.
After a recent earthquake in the San Joaquin Valley, several patients present to you complaining of cough, fever, and malaise. Descripe the appearance of the causative organism.
Coccidiomycosis looks like a spherule filled with endospores much larger than RBC. These spores are thrown up in the air and become spherules in lungs, particularly in times of earthquakes when dust is splayed everywhere.
A Latin American patient presents to you with severe cough, fever, and malaise. You note budding yeast with captain’s wheel appearance on stain that is much larger than RBCs. What is the causative organism/
Paracoccidiomycosis (Paracoccidio parasails with the captain’s wheel all the way to Latin America.)
Opportunistic mold with septate hyphae that branch at a 45 degree angle
Aspergillus fumigatus
Opportunistic mold with irregular nonseptate hyphae that branch at wide angles
Mucor (ribbon like hyphae)
Disc-shaped yeast forms on methenamine silver stain of lung tissue
Pneumocystis jirovecii
Name 5 infections associated with birds.
Histoplasma capsulatum
Cryptococus neoformans
Chlamydophila psittaci
H5N1 influenza
West Nile virus
Culture required for C. diphtheria
Tellurite plate or Loffler’s media
Culture required for M. pneumoniae
Eaton’s agar
Culture required for B. pertussis
Bordet-Gengou agar
Feature that aids in colonization of Neisseria spp.
Produce IgA protease
Describe the H. influenzae baccine.
Contains Type B capsular polysaccharide (polyribosylribitol phosphate) conjugated to diphtheria toxoid or other protein. Given between 2-18 months of age.
Most common organism that causes mastoiditis
H. influenzae
This organism is detected clinically by the presence of Ag in the urine.
Legionella
This organism is associated with diabetic osteomyelitis and malignant otitis externa (in diabetics)
P. aeruginosa
Structure of virus that causes pure RBC aplasia and rheumatoid-arthritis like symptoms in adults
Parvovirus is naked, SS and linear DNA
Family of viruses that causes progressive multifocal leukoencephalopathy in HIV
Polyomavirus (JC virus)
Pathogenesis of HHV 8
Lymphoangiogenic growth factors/cytokines: TNF alpha, IL-6, PDGF
This is Kaposis sarcoma
Classic presentation and cause of Roseola
High fever for a few days
Fever breaks, but then the kid breaks out in a diffuse maculopapular rash
Caused by HHV-6
Downey cells
Occur with EBV
T cells with abnormal cytoplasm and foamy appearance
What cells do CMV stay latent in?
Mononuclear cells
What cells does EBV stay latent in?
B cells
Enzyme HBV uses to make DNA
Reverse transcriptase
Serologic marker that is positive during window period of Hepatitis B infection
IgM core antibody
3 complications of measles
SSPE
Encephalitis
Giant cell pneumonia in immunosuppressed
Which family of viruses causes postauricular adenopathy, arthralgias, and a fine truncal rash?
Togavirus (Rubella)
Bullet shaped capsid
Rabies virus
What family of viruses has F (fusion) protein on their surface?
Paramyxoviruses – RSV, parainfluenza, mumps, measles
This causes respiratory epithelial cells to fuse and form multinucleated cells
Which virus causes African hemorrhagic fever?
Ebola
3 viral causes of aseptic meningitis
Echovirus
Coxsackievirus
Enterovirus
Describe the Tourniquet test.
This is the WHO field test for hemorrhagic fever caused by dengue. The BP cuff is inflated to a point between SBP and DBP and then left there for 5 minutes. If petechiae found underneath where cuff was, indicative of increased capilalry wall fragility and thrombocytopenia.
How does rabies virus travel through CNS so taht it can cause fatal encephalitis with seizures?
Retrograde fashion up axons
Examples of live virus vaccines
MMR
Sabin polio (oral)
VZV
Yellow fever
Smallpox
Intranasal influenza
Where does herpesvirus acquire its envelope?
Nuclear membrane (vs. plasma membrane, like most)
Which viral family carries diploid DNA?
Retrovirus
4 naked DNA viruses
Papillomavirus
Adenovirus
Polyomavirus
Parvovirus
4 naked RNA viruses
Calcivirus
Picornavirus
Reovirus
Hepevirus
3 DNA viruses that are not linear
Papilloma and polyoma (circular, supercoiled)
Hepadna (circular, incomplete)
Only DNA virus that is not icosahedral
Pox (complex)
Only DNA virus that does not replicate in the nucleus
Pox (carries own DNA-dependent RNA polymerase)
Name all 7 DNA viruses.
Hepadnavirus
Herpesviridae
Adenovirus
Poxvirus
Parvovirus
Papillomavirus
Polyomavirus
HHAPPPy
2 recombinant vaccines
HBV (recombinant HBsAg)
HPV (types 6, 11, 16, 18)
4 killed vaccines
Rabies
Influenza (injected)
Salk Polio
HAV
2 most common causes of pneumonia in Neonates (<4 weeks)
Group B strep
E. coli
5 most common causes of pneumonia in children 4 weeks-18 years old
Viruses (RSV)
Mycoplasma
C. trachomatis (infants-3 years)
C. pneumo (school age)
S. pneumo
3 most common causes of pneumonia in adults 18-40 y.o.
Mycoplasma
C. pneumo
S. pneumo
5 causes of pneumonia in adults 40-65 years old
S. pneumo
H. influenzae
Anaerobes
Viruses
Mycoplasma
5 causes of pneumonia in the Elderly
S. pneumo
Influenza virus*
Anaerobes
H. influenzae
Gram negative rods*
3 organisms associated with pneumonia in Alcoholics and IV drug users
S. pneumo
Klebsiella
Staphylococcus
4 causes of pneumonia in immunocompromised
Staph
Enteric gram negative rods
Fungi
Viruses
PCP with HIV
3 causes of post-viral pneumonia
Staph
H. influenzae
S. pneumo
3 most common causes of meningitis in the newborn 0-6 mo.
Group B strep
E. coli
Listeria
4 most common causes of meningitis in children 6 mo-6 years old
S pneumo
N. meningitidis
H influenzae type B
Enteroviruses
4 most common causes of meningitis 6-60 y.o.
S. pneumo
N. meningitidis (#1 in teens)
Enteroviruses
HSV
3 most common causes of meningitis in 60 y.o. and older
S. pneumo
Gram negative rods
Listeria
Most common cause of osteomyelitis overall
S. aureus
2 organisms that cause osteomyelitis in diabetics and IVDA
P. aeruginosa
Serratia
2 organisms that cause osteomyelitis in prosthetic replacement patients
S. aureus
S. epidermidis
What does a positive leukocyte esterase test indicate vs. a positive nitrite test?
If its postiive leukocyte esterase – bacterial UTI
If nitrite test is positive – gram negative bacterial UTI
Classic triad with congenital Toxoplasma gondii infection
Chorioretinitis
Hydrocephalus
Intracranial calcificaions
Fever in a post-op patient 1-2 days after surgey
Atelectasis
Early manifestations of congenital syphilis (first 5 weeks of life)
Hepatosplenomegaly, elevated LFTS
Hemolytic anemia, jaundice
Rash followed by desquamation of hands and feet
Snuffles (blood tinged nasal secretions)
Radiographic changes: metaphyseal dystrophy and periostitis
pH of vagina in candida infection
Low
pH of vagina in BV and trichomonas
High/basic
