Microbiology Flashcards
Thayer Martin VCN medium
Selective for Niesseria (e.g N.Gonorreha Gram-ive diplococci)
Medium contains vancomycin, Colisistin, Nystatin, Trimethoprim
which kills all others except Nisseria.
Group-A Strep
AKA Strep Pyogenes
M-protien (virulence factor)
resist phagocytosis (molecular mimicry)
has structural homology to Tropomyosin & Myosin reacts to epitopes on mysoin causing Rheumatic carditis
Main Causes of UTI
E-coli, Klebsiella, Proteus, Enterobacteria, Staph Saprophyticus
Congenital Syphillis
Tryponema Palladium (Spirochete)
Atypical Delivery
Abcess like foci of necrosis around umbilical vessels
Growth Restriction
Late symptoms(can be prevented by penicillin) are saddle nose & notched teeth
VDRL+, Rapid Reagin test
Organisms causing risk of ectopic Pregnancy
Nisseria Gonorrhea , Chlamydia trachomatis
cause PID and tubular scaring which increases the risk of ectopic pregnancy.
Clostridium Tetani
Causes tetanus
metalloprotease exotoxin tetanospasmin inhibits neurotransmitters Glycine & GABA
Muscle spasms, hyperreflexia, lock jaws
Scabies
Sarcoptes scabiei mite infestation Spread by direct person-to-person contact
Extremely pruritic, small, erythematous papules
Distribution: interdigital web spaces, flexor wrists, extensor elbows, axillae, feet, umbilicus & genitalia
Burrows (thin serpiginous lines) may not be visible but pathognomonic if present
H.Pylori
Gastritis, Ulcers, PUD
Also assosiated with MALT Lymphoma
Herpes
doble strand DNA virus (ds DNA)
HPV
ds DNA virus
Chlamydia
obligate intracellular bacteria; causes PID, cervicitis (yellow pus), or conjunctivitis (Neonatal blindness)
Niesseria Gonorrhea
gram-negative diplococcus;
presents with mucopurulent discharge; can be present with palmar pustule, arthritis/ joint pain, urethral discomfort
Hemophilus ducreyi
Gram Negative Rods
Causes CHANCROID (painful with a necrotic center)
CMV
Enveloped ds DNA virus
Causes congenital blinding
Can also cause pneumonitis & CMV retinitis
Immunocompromised patient at high risk (i.e transplant patients, HIV etc)
Histology : Enlarged cells with intranuclear and intracytoplasmic inclusions (OWLs EYE NUCLEUS)
there is often surrounding halo.
West Nile Virus
West Nile fever:
fever, headache, rash (maculopapular/morbilliform)
Neuroinvasive:
meningitis, encephalitis, acute asymmetric flaccid paralysis
Parkinsonian symptoms (eg, rigidity, bradykinesia, tremor)
West Nile virus is a single-strand flavivirus transmitted by mosquitoes, most commonly in the summer. Most infections are asymptomatic or may present with a flu-like illness (West Nile fever), often with a maculopapular or morbilliform rash. Neuroinvasive disease manifests as meningitis, encephalitis, or asymmetric flaccid paralysis; patients may have parkinsonian features (eg, tremor
Bordetella Pertussis
Gram –ive coccobacilli
Whooping cough
May be assosiated with vomitting and nausea
Tracheal toxin : destroy ciliated epithelial cells leads to loss of airway clearence
Pertussis/ AB toxin: activates adenylate cyclase leading to alteration in signalling inhibit phagocytosis and cause lymphocytosis.
Toxoplasma Gondii
Causes toxoplasmosis, seen in HIV patients
Multiple ring enhanced lesions in temporal lobe.
Clostridiodes difficile
Part of normal gut flora
Increase growth due to killing of other GI flora due to antibiotic use
Has Toxin A, Toxin B stimulate inflamatory reaction and disrupt the actin cytoskeletal structure resulting in pseudomembranous colitis characterized by:
Crampy abdominal pain
Watery Diarrhea
Leukocytosis
Norovirus
Single stranded RNA genome
MCC of viral gastroenteritis in developed countries
Acute onset resolves in 2-3 days
Vomitting
Watery Diarrhea (No blood or Mucus)
Fecal oral spread
Outbreaks in crowded settings
MacConkey Agar
Selective for gram negative rods
Gram –ive Bacilli (Rods) =
lactose fermenting (Colonies turn pink) & Non lactose fermenting
Lactose fermenting:
Slow- Citrobacter , Serratia
Fast- Inodole +ive = E.coli (ability to convert tryptophan to inodole)
Inodole –ive = Klebsiella , Enterobacter
Non-Lactose fermenting:
Oxidase +ive = Pseudomonas
Oxidase –ive =
H2S producing : Salmonella, Proteus
Non H2S producing : Shigella , Yersinia
ETEC
- Enterotoxigenic E. coli causes traveler’s diarrhea.
- Will present as brown/green diarrhea in person who’s gone to
Mexico or Middle East classically. - Heat-labile toxin ADP ribosylates adenylyl cyclase ↑ cAMP.
- Heat-stable toxin ADP ribosylates guanylyl cyclase ↑ cGMP.
EHEC
- Enterohemorrhagic E. coli causes bloody diarrhea 1-3 days after consumption of beef.
- Produces shiga-like toxin, which can cause hemolytic uremic syndrome
(HUS; triad of renal dysfunction, schistocytosis, thrombocytopenia).
Shigella
- Bloody diarrhea 1-3 days after consumption of beef.
- Also can cause HUS via shiga toxin.
- Requires very few organisms to cause infection.
- Main virulence is via its ability to invade, not the toxin itself.
- Both shiga toxin of Shigella and shiga-like toxin of EHEC inhibit protein synthesis by cleaving the eukaryotic 60S ribosomal subunit
Yersinia enterocolitica
- Causes bloody diarrhea + either appendicitis-like (i.e., RLQ) pain or arthritis.
- The RLQ pain is from mesenteric adenitis or terminal ileitis.
- Toxin has same MOA as ETEC heat-stabile toxin (i.e., cGMP).
Campylobacter jejuni
- Bloody diarrhea 1-3 days after consumption of poultry.
- Can cause Guillain-Barre syndrome (ascending paralysis + ¯ tendon reflexes + albuminocytologic dissociation in the CSF –> Tx with IVIG + plasmapheresis).
- Grows best at high temperatures (42 degrees).
Bacillus cereus
- Watery diarrhea and/or vomiting in patient who’s consumed reheated or fried rice. The process of heating/re-heating causes germination of spores.
- Can also cause eye infections.
Clostridium perfringens
- Watery/secretory diarrhea following consumption of poultry.
- Causes gas gangrene (CO2 gas) due to production of alpha-toxin/phospholipase; presents as black skin / crepitus.
- Can also cause emphysematous cholecystitis (air in gall bladder wall).
Clostridium difficile
- Diarrhea (pseudomembranous colitis) ~7-10 days after commencing oral antibiotics.
- Diagnose with stool AB toxin test.
- Treat with oral vancomycin.
Trichinella spiralis
- Ingested by eating pork/bear meat.
Causes triad of fever, periorbital edema, and myalgias. (Trichinosis)
Taenia solium
- Pork tapeworm.
Causes cysticercosis (muscle pain/cysts) + neurocysticercosis
(“Swiss cheese” appearance of brain or soap bubbles in ventricles).
Haemophilus
Influenzae
- Causes Epiglottitis
- Inflamed Epiglottitis;
- Thumbprint sign on Xray
- 2-3 Years old & unvaccinated children
- Capsule (Polyribitol Phosphate) inhibits Phagocytosis;
- IgA Proteases
- Gram (-) Rods grow on Chocolate Agar
- Tx: Ceftriaxone
Parainfluenza
(paramyxoviridae)
- Causes: Croup, Laryngotracheitis, Laryngotracheobronchitis
- Fever, sharp barking cough, inspiratory hoarse phonation, steeple sign on AP Xray seen on Croup.
- Seen in Infants
- Tx: Rivabarin
Respiratory Syncytial Virus RSV
(paramyxoviridae)
- Causes Bronchitis, Bronchiolitis
- Wheezing
- Infants or Child <5 Years old
Mycoplasma pneumoniae
- Causes Bronchitis, Bronchiolitis.
- Seen in Child >5 year old.
- Release of 02 radicals causes necrosis of epithelium.
- Slow Growth on Eaton Medium.
- Cold agglutinins.
Streptococcus pneumoniae
- Gram (+) diplococcus, alpha
hemolytic, catalase (-), lysed by bile, inhibited by optochin. - Causes Typical Lobar pneumonia.
- Rust colored sputum;
- Lobar pneumonia or less commonly, bronchopneumonia
- Seen in Adults and Alcoholics.
- Anti-phagocytic capsule.
- IgA protease.
- Tx : Macrolides + Quinolones
Staphylococcus Aureus
- Gram (+), Catalase (+) cocci in chains.
- Causes Typical Lobar pneumonia.
- Nosocomial/respiratory Salmon colored sputum.
- A protein binds to Fc of IgG to inhibit opsonization and phagocytosis.
- Tx : Beta-lactams, Carbapenems, Vancomycin.
Klebsiella pneumonia
- Encapsulated Gram (-) rod, Oxidase (-),
Lactose fermenting Facultative anaerobe. - Causes aspiration assossiated typical pneumonia.
- Chronic, lung disease, alcoholism or diabetes.
- Currant jelly sputum.
- Capsule protects against phagocytosis.
- Tx : Ceftriaxone +/- Aminoglycoside
Carbapenem for ESBL-strains
Anaerobes, mixed infection
(Bacteroides, Fusobacterium, Peptococcus)
- Aspiration of vomit, leads to enzyme damage, leads to anaerobic foci.
- Foul Smelling Sputum.
- Tx : Empiric Antibiotic Therapy
(Amoxicillin-Clavulanate, Gentamicin)
Pseudomonas aeruginosa
- Gram (-) rod, Oxidase (+), Blue green pigments.
- Seen in Neutropenic patients, burn patients, Chronic Granulomatous Disease, Cystic Fibrosis.
- Biofilm, Exotoxin A.
- Tx : Azithromycin, Third-Generation Cephalosporin.
Yersinia pestis
- Gram (-) rod, Coagulase (+) with a safety pin appearance
(bipolar staining). - Cause of bubonic and pulmonic plagues (this
one, characterized by pulmonary septic emboli), - Fever + Buboes.
- Flea bite (vector); Wild rodents are carriers (prairie dogs).
- Tx : Aminoglycosides.
Influenza A and B
(Orthomyxoviridae)
- Fever, Headache, Malaise, Myalgia and Cough.
- ”Flu” season.
- Antigenic drift (Influenza A and B).
- Antigenic shift (Influenza A).
Tx :
- Oseltamivir, Zanamivir
(Neuraminidase inhibitors)
- Killed vaccine
Francisella tularensis
- Gram (-) Aerobe, Cysteine (+)
- Inhalation of aerosolized blood from butchering or skinning rabbits.
Chlamydophila psittaci
- Gram (-) Obligate intracellular.
- Atypical pneumonia.
- Exposure to birds and/or parrots.
- Association with hepatitis.
Tx : Tetracycline, Erythromycin.
Pneumocystis jirovecii
- MCC cause of pneumonia in AIDS.
- Interstitial plasma cell pneumonia.
- Methamine silver cysts.
Tx : TMX-SMX.
Streptococcus pyogenes
- Gram (+), Catalase (-) coccus;
- Beta-hemolytic, Bacitracin sensitive.
- Inflamed tonsils/pharynx, abscesses; cervical lymphadenopathy, fever, stomach upset, sandpaper rash.
- Exotoxins A-C (superantigens).
- Tx : Penicillin.
Neutropenic patients are at high risk of what infections? Define Neutropenic Fever?
- Neutropenic patients are at high risk of Gram Negative infections
(i.e Pseudomonas). - Neutropenic Fever is defined as Fever > 101 F + Absolute neutrophil
count < 500 neutrophils/ mm3. - Gram Negative infections (i.e. Pseudomonas) are most important
cause associated with rapid clinical deterioration due to production
of endotoxins. - Gram Positive infections can also occur i.e. in case of indwelling
catheters but they are less virulent and have slow onset.
Give the classic triad of clinical features in congenital toxoplasmosis?
- Toxoplasma gondii infection in cats (definitive host)
- Spread to humans & animals via oocysts shed in cat feces
- Transplacental transmission from infected mother to fetus
Classic Triad:
- Chorioretinitis
- Hydrocephalus
- Intracranial calcifications
- Nonspecific: jaundice, hepatosplenomegaly
Name the 2 main virulence factors of Bacillus anthracis?
- Polypeptide capsule composed of poly-γ-D-glutamic acid (antiphagocytic)
- Exotoxin complex composed of protective antigen, edema factor, and lethal factor
organism to the yeast morphology (Blastomyces dermatitidis/Histoplasma capsulatum):
- Large, broad-based budding yeasts with thick refractile walls: Blastomyces dermatitidis
- Small, narrow-based budding yeasts within macrophages: Histoplasma capsulatum
Patient develops periorbital edema, myositis, and eosinophilia following consumption of undercooked pork. What is the causative parasite?
Trichinella (invades the skeletal muscle).
what are catalase positive organisms?
Catalase converts hydrogen peroxide into water and oxygen.
- Aspergillus
- Burkholderia cepacia
- Nocardia
- Serratia marcescens
- Staphylococcus aureus
Immunosuppressed patient with slowly worsening headache, fever, and confusion,
Cerebrospinal fluid latex agglutination test is positive for capsular polysaccharide antigen.
What is the diagnosis? How is this infection acquired?
Diagnosis: Cryptococcal meningitis
How is this infection acquired? Inhalation of yeast (resides in soil contaminated by bird droppings).
Tabes dorsalis
Years → decades after initial infection
Increased incidence/more rapid progression in those with HIV
Treponema pallidum directly damages dorsal sensory roots
Secondary degeneration of the dorsal columns
Clinical findings:
- Sensory ataxia
- Lancinating pains
- Neurogenic urinary incontinence
- Associated with Argyll Robertson pupils
Argyll Robertson pupil (small, irregularly shaped pupils that accommodate but do not react to light).
Rx: 10-14 days of intravenous penicillin G
Hepatitis main modes of transmission?
- Hepatitis A: fecal-oral (eg, undercooked shellfish)
- Hepatitis B: sexual, percutaneous (eg, intravenous drug use), vertical
(ie, mother-to-child) - Hepatitis C: percutaneous (eg, intravenous drug use), sexual
Most common causes of necrotizing fasciitis
Most common causes of necrotizing fasciitis:
1. Streptococcus pyogenes (group A Streptococcus)
2. Staphylococcus aureus
3. Clostridium perfringens
4. Polymicrobial infection
Toxoplasmosis
- Chorioretinitis
- Hydrocephalus
- Diffuse intracranial calcifications
Syphilis
- Rhinorrhea
- Skeletal anomalies
- Desquamating rash (palms/soles)
Rubella
- Cataracts
- Heart defects (eg, PDA)
- Sensorineural hearing loss
CMV
- Periventricular calcifications
- Microcephaly
- Sensorineural hearing loss
Diphtheria
Patient presents with fever; sore throat; cervical lymphadenopathy; and a gray, pharyngeal pseudomembrane. The diagnosis is diphtheria, which is caused by a gram-(positive) (bacillus).
Toxigenic Corynebacterium diphtheriae colonizes respiratory tract → secretes diphtheria toxin → inhibits host protein synthesis (ADP-ribosylation of EF-2) → local & systemic toxin-mediated effects
- Local: pseudomembranous pharyngitis, cervical lymphadenopathy
- Systemic: myocarditis/heart failure, neurologic toxicity
- Pharyngeal edema/pseudomembrane spread can obstruct
respiratory tract.
Main risk factors for this disease: Inadequate vaccination/10-year booster vaccination
Rx: Diphtheria antitoxin (most important)
Name 3 diseases caused by Ixodes scapularis tick bite?
- Babesiosis (Babesia)
- Lyme disease (Borrelia burgdorferi)
- Human granulocytic anaplasmosis (Anaplasma)
Entamoeba histolytica
Main route of transmission: Consumption of cysts in contaminated water/food or fecal-oral transmission.
Symptoms:
- Intestinal: abdominal pain, diarrhea, bloody/mucoid stool
- Extraintestinal: liver abscess (eg, RUQ pain)
Diagnostic stools:
- Stool PCR/antigen testing (preferred)
- Microscopy findings: Cysts, trophozoites with ingested red blood
cells.
Bacterial Vaginosis (Gardnerella Vaginalis)
- Thin Discharge with “ Fishy Odor “
- Clue cells
- Positive Whiff test
Rx: Metronidazole
Trichomoniasis (Trichomonas Vaginalis)
- Yellow Green Frothy Discharge
- Motile Trichomonads
Rx: Metronidazole
Candida Vaginitis (Candida Vaginalis)
- Thick Cottage-Cheese discharge
- Pseudohyphae
Rx: Fluconazole
Most Common cause of Viral meningitis?
Enteroviruses are the most common cause of viral meningitis.
Examples: coxsackievirus, echovirus, enterovirus.
Lactose Fermenting Gram Negative Bacilli
(Fast Lactose fermenting)
- E.coli (Indole +ive)
- Klebsiella (Indole -ive)
- Enterobacter (Indole -ive)
(Slow Lactose fermenting)
- Citrobacter
- Serratia
Non-Lactose Fermenting Gram Negative Bacilli
- Oxidase +ive: Pseudomonas
- Oxidase -ive:
. H2S Producing: Salmonella , Proteus
. Non-H2S Producing: Shigella & Yersinia
Spiral, Comma or S-shaped Gram Negative bacteria
- Oxidase Positive
- Campylobacter Jejuni (Grows in 42 C)
- Vibrio Cholera (Grows in Alkaline Media)
- H. Pylori (Urease Producing)
Gram Negative Coccobacilli
- H. Influenza
- B. Pertussis
- Pasteurella
- Brucella
- F. Tularensis
Gram Negative Diplococci
Aerobic
Maltose Utilization: Yes
- N. Meningitidis
Maltose Utilization: NO
- N. Gonorrhea
- Moraxella
Patient with fever, cough, dyspnea, diarrhea, and hyponatremia
Legionella pneumophila is a gram-(negative), (intracellular) bacteria that can be cultured on buffered charcoal yeast extract (BCYE) agar.
Legionella pneumophila
Recent travel (especially cruise/hotel visit)
Hospital/nursing home stay
- Fever >39 C (102.2 F)
- Bradycardia relative to high fever
- Headache & confusion
- Watery diarrhea
Laboratory findings:
- Hyponatremia
- Sputum Gram stain shows many neutrophils but few or no
organisms.
Diagnosis:
- Culture of organism on BCYE
- Legionella urine antigen test
The most common pathogen associated with osteomyelitis is?
Staphylococcus aureus.
The pathogen classically associated with sickle cell disease?
Salmonella
Vertebral osteomyelitis may also be classically associated with?
Mycobacterium tuberculosis, which causes Pott disease.
The most common cause of acute cystitis? Virulence factor?
- Escherichia coli is the most common cause of acute cystitis
- P fimbria is the virulence factor that allows it to adhere to
uroepithelium.
Pathogenesis of Mycobacterium tuberculosis:
Initially the organism replicates unchecked in alveolar macrophages due to virulence factors (eg, cord factor) (allow bacteria to escape destruction within phagolysosomes).
After a few weeks, T-helper subtype-(1) cells migrate to the infection sites and secrete interferon-gamma, resulting in activation of (macrophages), which wall off the mycobacteria.
This forms what characteristic histopathologic finding?
Granulomas.
(The center of the granuloma is acidic and hypoxic, which causes it to appear acellular & necrotic).
Patients with disseminated gonococcal infection typically present with?
Either purulent arthritis or the triad of polyarthralgia, dermatitis, and tenosynovitis.
What is the function of bacterial IgA protease?
Virulence factor that facilitates bacterial adherence to mucosa by cleaving IgA at hinge region (IgA antibodies usually bind to pili and other membrane proteins involved in adherence).
Name 4 bacteria that produce IgA protease.
- Haemophilus influenzae
- Neisseria gonorrhoeae
- Neisseria meningitidis
- Streptococcus pneumoniae
JC Virus
Polyomavirus family
JC virus can cause progressive multifocal leukoencephalopathy in patients with (advanced HIV) (eg, subacute neurologic deficits, asymmetric white matter demyelination).
BK virus
Polyomavirus family
BK cause life-long latent infections. reactivation can cause nephropathy in patients with (renal transplantation).
CMV infected cells Microscopic appearance?
Enlarged cells with intranuclear and intracytoplasmic inclusions (“owl’s-eye” appearance).
E.coli virulence factors
- Lipopolysaccharide (LPS):
Activates Macrophages > Widespread release of IL-1, IL-6 & TNF
alpha > Presents as Bacteremia , Septic Shock. - K-1 Capsular polysaccharide:
Prevent phagocytosis & Complement mediated Lysis > Presents
as Neonatal Meningitis. - Shiga toxin:
Inactivates 60S ribosomal subunit, halting protein synthesis &
causing cell death > Presents as Gastroenteritis (Bloody) - Heat stable/ Heat liable enterotoxin:
Promotes fluid and electrolyte secretion from intestinal
epithelium > Presents as Gastroenteritis (watery). - P-Fimbriae:
Allows adhesion to Uroepithelium > Presents as UTI.
Name 2 organisms that can cause impetigo?
1- Staphylococcus aureus (most common)
2- Streptococcus pyogenes (group A Streptococcus)
Pustules/vesicles with honey-crusted lesions, Most commonly involves face or extremities.
Complications:
Poststreptococcal glomerulonephritis
What is the classic blood smear finding in infectious mononucleosis (EBV)?
Atypical lymphocytes (reactive CD8+ T lymphocytes).
- Large reactive lymphocytes
- Abundant cytoplasm
- Cytoplasm indented by adjacent erythrocytes
Epstein-Barr virus preferentially infects (B/T) lymphocytes?
Epstein-Barr virus preferentially infects (B) lymphocytes by binding CD21 receptors.
Name 2 common pathogens associated with pelvic inflammatory disease?
- Chlamydia trachomatis
- Neisseria gonorrhoeae
Infections associated with ectopic pregnancy.
List the function of the Neisseria meningitidis virulence factors.
- Polysaccharide capsule: impairs phagocytosis of the bacteria
- Lipo-oligosaccharide: induces cytokine production, leading to
circulatory collapse - Pili: permits bacterial attachment to respiratory mucosa
- IgA protease: cleaves secretory IgA that would otherwise inhibit
the action of the pili
MacConkey agar is selective for?
- Gram-(negative) organisms.
- Organisms that ferment lactose cause a local drop in pH on the
agar, resulting in colonies with a pink appearance - e.g., Escherichia coli, Klebsiella, Enterobacter, Citrobacter.
A hydatid cyst is visualized on liver ultrasound.
This is most often caused by infection with (Echinococcus granulosus),
Acquired by ingestion of infective eggs in food contaminated with (dog) feces.
Patient with fever, agitation, pharyngeal spasms, dysphagia, and hydrophobia. What is the diagnosis? Brain histopathology shows what pathognomonic finding?
Rabies infection.
- Brain histopathology pathognomonic finding:
Negri bodies (eosinophilic neuronal cytoplasmic inclusions).
Name the function of the following glycoproteins in the influenza virus life cycle?
- Hemagglutinin: allows viral entry into the host cell
- Neuraminidase: allows release of virions from infected cell
Biopsy of a dome-shaped, umbilicated papule on the trunk shows epidermal hyperplasia with large, eosinophilic cytoplasmic inclusions. What is the diagnosis?
Molluscum contagiosum.
Mucormycosis
Patient with facial swelling, headache, purulent nasal discharge, and black necrotic eschar in nasal cavity.
Biopsy shows broad, non-septate hyphae branching at 90-degree angles
Risk factors include diabetes mellitus (especially diabetic ketoacidosis) and immunosuppression (eg, solid organ transplantation, hematologic malignancies, glucocorticoid therapy).
Foodborne botulism
Adult foodborne botulism characteristically presents as a symmetric descending paralysis that initially manifests with the following symptoms (3 Ds mnemonic):
- Diplopia
- Dysphagia
- Dysphonia
Parvo virus B-19
- Immunocompetent child: erythema infectiosum (“fifth disease”)
(“slapped cheek” appearance) - Immunocompetent adult: symmetric arthropathy (involving hands,
wrists, knees, and/or feet) - Patient with chronic hemolytic anemia: aplastic crisis
- Fetus: hydrops fetalis (severe anemia, HF , effusions & ascites)
Name 4 clinical manifestations of coxsackievirus infection.
- Aseptic meningitis
- Hand-foot-mouth disease
- Herpangina
- Myocarditis/pericarditis
Name the organisms most commonly associated with acute epididymitis?
- In young men: Chlamydia trachomatis, Neisseria gonorrhoeae
(sexually transmitted pathogens) - In older men (age >35): gram-negative colonic flora (eg,
Escherichia coli)
Child develops periorbital edema, tea-colored urine, hypertension, and oliguria 2 weeks after having a sore throat. Urinalysis shows protein and blood. What is the most likely causative organism?
Streptococcus pyogenes (Group A Streptococcus)
What are typical clinical features of shigellosis?
Small-volume bloody/mucoid diarrhea, abdominal tenderness, and fever.
Patient develops fever, headache, maculopapular rash, retroorbital pain, arthralgia, myalgia, epistaxis, and petechiae following a trip to Central America. What is the diagnosis?
Dengue virus infection
Nonhemorrhagic:
- Flu-like febrile illness with marked myalgia &/or arthralgia
- Diffuse maculopapular rash
- Retroorbital pain
- Leukopenia
Hemorrhagic:
- Increased vascular permeability
- Positive tourniquet test (petechiae after sphygmomanometer cuff
inflation for 5 min) - Hemoconcentration & thrombocytopenia
- Spontaneous bleeding → shock
In immunocompromised patients, cytomegalovirus infection can cause the following clinical manifestations:
- Retinitis
- Colitis
- Esophagitis
- Pneumonitis
- Hepatitis
Name the viral association for each AIDS-defining malignancy.
- Kaposi sarcoma = Human herpesvirus 8
- Invasive cervical carcinoma = Human papillomavirus
- Non-Hodgkin lymphoma = Epstein-Barr virus
- Primary CNS lymphoma = Epstein-Barr virus
Name 3 infections commonly associated with a rash involving the palms and soles.
- Hand-foot-and-mouth disease (coxsackievirus infection)
- Rocky Mountain spotted fever (Rickettsia rickettsii infection)
- Secondary syphilis (Treponema pallidum infection)
Key respiratory tract infections in children
1- Laryngotracheitis (Croup): Parainfluenza virus
- Age 6mo-3yrs
- Barking cough, Stridor, Hoarseness
2- Epiglottitis: H. Influenzae
- Unvaccinated Children
- Sore throat, Dysphagia, Drooling, tripod position.
3- Bronchiolitis: Respiratory Syncytial Virus (RSV)
- Age < 3yrs
- Wheezing Cough
Child with diffuse erythematous, sandpaper-like rash with circumoral pallor, and a bright red tongue. What is the diagnosis? What is the causative organism?
Scarlet fever caused by Streptococcus pyogenes (Group A Streptococcus). Associated with streptococcal pharyngitis.
Patient develops fever, myalgias, headache, and conjunctival hyperemia after kayaking trip due to infection with a spiral-shaped bacterium. What is the diagnosis?
Leptospirosis (Leptospira infection)
Teenager with rapid-onset headache, fever, altered mental status, nuchal rigidity, and petechial rash.
- Diagnosis: Meningococcal meningitis (due to Neisseria meningitidis).
- Route of transmission: Primarily aerosolized droplets (subsequently
colonizes the nasopharyngeal epithelium)
In patients with HIV, what CD4 count is a risk factor for each of the following opportunistic infections?
- Cryptococcus neoformans: CD4 <100/mm3
- Mycobacterium avium complex: CD4 <50/mm3
- Pneumocystis jirovecii: CD4 <200/mm3
- Toxoplasma gondii: CD4 <100/mm3
Name 4 viruses transmitted by Aedes mosquito:
- Chikungunya
- Dengue
- Yellow fever
- Zika
Simultaneous outbreaks and coinfections are common.
Patient with fever, nausea, jaundice, and abdominal pain. What serology results indicate an active hepatitis A virus (HAV) infection?
Anti-HAV IgM
Common causes of community acquired pneumonia in Children?
- Age < 1 month : Group B Strep , E.coli
- Age 1mo-5yrs: Streptococcus pneumonia, Non-typeable H. Influenza
- Age > 5yrs : Mycoplasma Pneumonia , Streptococcus pneumonia
Pseudomonas infections:
- Patient develops pruritic papules after swimming= Hot tub
folliculitis - Patient with neutropenia develops necrotic, ulcerated gluteal
plaques= Ecthyma gangrenosum - Patient with severe ear pain and granulation tissue in the ear
canal= Malignant otitis externa (often in elderly diabetic patients)
Chagas disease
Chagas disease is caused by infection with (Trypanosoma cruzi). Features of chronic disease include:
- Cardiac: cardiomyopathy
- Esophagus: megaesophagus (secondary achalasia)
- Colon: megacolon
In immunocompetent patients with a heterophile antibody-negative mononucleosis-like syndrome, the most likely diagnosis is?
Cytomegalovirus infection (CMV).
Name 4 clinical manifestations of Streptococcus pneumoniae infection?
(MOPS mnemonic).
- Meningitis
- Otitis media
- Pneumonia
- Sinusitis
Clinical manifestations of secondary syphilis:
- Diffuse maculopapular rash that typically involves palms & soles.
- Condylomata lata: painless, wart-like plaques on moist skin (eg,
scrotum, perineum) - Lymphadenopathy
- Alopecia
- Constitutional symptoms (eg, malaise, fever)
Patients with cystic fibrosis are at risk for pulmonary exacerbations due to which bacteria?
- Staphylococcus aureus
- Nontypeable Haemophilus influenzae
- Pseudomonas aeruginosa
- Burkholderia cepacia complex
Mumps
- Mumps typically presents with a self-limited syndrome
characterized by fever and parotid swelling/parotitis. - The most common end organ complication of mumps is orchitis.
Causes of meningitis in children
Age<1 month:
- Group B Streptococcus
- Escherichia coli & other gram-negative bacteria
- Listeria monocytogenes
- Herpes simplex virus
Age≥1 month:
- Streptococcus pneumoniae
- Neisseria meningitidis
Rocky Mountain spotted fever
Is caused by (Rickettsia rickettsii), which is transmitted by a (tick) (eg, American dog tick).
Symptoms include fever, headache, and a macular-petechial rash that classically originates on the ankles or wrists and spreads to the center of the body (eg, trunk), palms, and soles.
Rx: Doxycycline
Clostridium botulinum toxin
A preformed neurotoxin.
- Botulinum toxin blocks the presynaptic exocytosis of Ach vesicles,
causing impaired muscarinic and nicotinic neurotransmission. - Botulinum toxin causes disease by inhibiting nicotinic and
muscarinic motor neurons, - It has manifestations of both nicotinic blockade (eg, dysphagia,
ptosis) and muscarinic blockade (eg, dry mouth). - Botulism characteristically presents as a symmetric descending
paralysis that first manifests with cranial nerve abnormalities.[ 3Ds ]- Diplopia,
- Dysphagia,
- Dysphonia
Gonococcal Arthritis
- Caused by N. Gonorrhoeae
- Teenager
- Joint pain (Single joint but can move another joint)
- Sexually active
- Rx: Ceftraxone
Mycoplasma Pneumonia
- Community acquired pneumonia
- “Walking pneumonia”
- Patients experience a low-grade fever, malaise, and a chronic, dry
nagging cough. - A classic sign is a chest x-ray revealing findings that are much worse
than the clinical appearance of the patient - Organisms require cholesterol to grow.
How do you diagnose rheumatic fever?
Need at least 2 of the “specc”
S- subcutaneous nodules
P- polyarthritis
E- erythema marginatum
C- chorea (sydenham’s chorea)
C- Carditis (MS>AS>TS) “MAT”
Five organisms that cause heart infections?
“Don’t TeLL Chaga”
D- Diphtheria
T- Typhoid Fever (salmonella typhi)
L- Legionella
L- Lyme disease
C- Chaga’s disease (whipple’s)
What are IgA protease organisms?
- Strep pneumonia
- H. Influenza
- N. Saprophyticus
- Moraxella Catarrhalis
what are atypical (no cell wall) bacteria?
” CLUMsy “
C- Chlamydia
L- Legionella
U- Ureaplasma
M- Mycoplasma
what organism causes atypical pneumonia?
- 0-2 months: Chlamydia Pneumophilia
- 10-30 yrs: Mycoplasma Pneumonia
- > 40 yrs: Legionella Pneumophilia
- AIDS & Immunocompromised patients: Pneumocystis Carini
What are encapsulated gram negatives?
” Some Killers Have Pretty Nice Capsules “
S- Salmonella
K- Klebsiella
H- H. Influenza B
P- Pseudomonas
N- Neisseria
C- Citrobacter
What bugs causes Monocytosis?
” STELS “
S- Syphilis
T- TB
E- EBV
L- Listeria
S- Salmonella
What are Urease positive bugs?
” Urease Positive PUNCHS Back “
P- Proteus
P- Pseudomonas
U- Urea plasma
N- Nocardia
C- Cryptococcus
H- H. pylori
S- Staph Spp
B- Brucellosis
Mumps
Classically presents as:
- Parotidits
- Orchitis
- Meningitis
Caused by Paramyxovirus.
Roseola Infantosum
Aka Sixths Disease
- Caused by HHV6 (Human Herpes 6 Virus)
- High grade Fever upto 104°F for 3-5days
Followed by Maculopapular Rash - Spiking Fever followed by Rash
Rubeola
High Fever & 3Cs ( Cough, Coryza, Conjuntivitis)
Koplik Spots (2-3days after symptoms)
As fever abates a Maculopapular rash starts at head and descends to cover whole body (like rubella)
Neonatal Herpes
- Caused by HSV-2 infection
- Characterized by:
> Vesicular Rash
> Encephalitis ( Siezures, CN palsies, Lethargy) - Typically acquired during delivery.
- Usually occurs 2 weeks after birth no symptoms at birth.
Whipple disease
(Tropheryma whipplei)
Arthralgias, adenopathy, cardiac and neurological symptoms, diarrhea
Toxoplasmosis
Multiple ring enhanced lesions around pareital lobe, from cat feces
Congenital CMV
spastic diplegia of legs,
hepatosplenomegaly,
blinding,
Central calcifications
Congenital Rubella Syndrome
Classical Triad:
1- Cataracts
2- Sensoneural hearing loss
3- PDA (patent ductus arteriosis)
Blueberry muffin rash on face & spreads to trunk
Can be prevented by giving live attenuated vaccine to mother preconception.
Congenital Syphillis
Rhagades (lip fissures),
Saber shins (anterior bowing of the tibia), Hutchinson’s razor teeth,
Mulberry molars
