Microbiology - Systems

Question 1

Normal (dominant) flora

• Skin
• Nose
• Oropharynx
• Dental plaque
• Colon
• Vagina
• Neonates delivered by C-section

Answer 1

• Skin
  
  • S. epidermidis
• Nose
  
  • S. epidermidis
  • Colonized by S. aureus
• Oropharynx
  
  • Viridans group streptococci
• Dental plaque
  
  • S. mutans
• Colon
  
  • B. fragilis > E. coli
• Vagina
  
  • Lactobacillus
  • Colonized by E. coli and group B strep
• Neonates delivered by C-section
  
  • Have no flora but are rapidly colonized after birth

Question 2

Sources of infections of bugs causing food poisoning

• B. cereus
• C. botulinum
• C. perfringens
• E. coli O157:H7
• Salmonella
• S. aureus
• V. parahaemolyticus and V. vulnificus

Answer 2

• B. cereus
  
  • Reheated rice.
  • Starts quickly and ends quickly
  • “Food poisoning from reheated rice? Be serious!” (B. cereus)
• C. botulinum
  
  • Improperly canned foods (sign is bulging cans)
• C. perfringens
  
  • Reheated meat dishes
• E. coli O157:H7
  
  • Undercooked meat
• Salmonella
  
  • Poultry, meat, and eggs
• S. aureus
  
  • Meats, mayonnaise, custard; preformed toxin
  • Starts quickly and ends quickly
• V. parahaemolyticus and V. vulnificus
  
  • Contaminated seafood
  • V. vulnificus can also cause wound infections from contact with contaminated water or shellfish

Question 3

Bugs causing bloody diarrhea (7)

Answer 3

• Campylobacter
• E. histolytica
• Enterohemorrhagic E. coli
• Enteroinvasive E. coli
• Salmonella
• Shigella
• Y. enterocolitica

Question 4

Bugs causing bloody diarrhea

• Campylobacter
• E. histolytica
• Enterohemorrhagic E. coli
• Enteroinvasive E. coli
• Salmonella
• Shigella
• Y. enterocolitica

Answer 4

• Campylobacter
  
  • Comma- or S-shaped organisms
  • Growth at 42°C
• E. histolytica
  
  • Protozoan
  • Amebic dysentery
  • Liver abscess
• Enterohemorrhagic E. coli
  
  • O157:H7
  • Can cause HUS
  • Makes Shiga-like toxin
• Enteroinvasive E. coli
  
  • Invades colonic mucosa
• Salmonella
  
  • Lactose (-)
  • Flagellar motility
  • Has animal reservoir, especially poultry and eggs
• Shigella
  
  • Lactose (-)
  • Very low ID50
  • Produces Shiga toxin (human reservoir only)
  • Bacillary dysentery
• Y. enterocolitica
  
  • Day-care outbreaks
  • Pseudoappendicitis

Question 5

Bugs causing watery diarrhea (6)

Answer 5

• C. difficile
• C. perfringens
• Enterotoxigenic E. coli
• Protozoa
• V. cholerae
• Viruses

Question 6

Bugs causing watery diarrhea

• C. difficile
• C. perfringens
• Enterotoxigenic E. coli
• Protozoa
• V. cholerae
• Viruses

Answer 6

• C. difficile
  
  • Pseudomembranous colitis.
  • Caused by antibiotics.
  • Occasionally bloody diarrhea.
• C. perfringens
  
  • Also causes gas gangrene
• Enterotoxigenic E. coli
  
  • Travelers’ diarrhea
  • Produces heat-labile (LT) and heat-stable (ST) toxins
• Protozoa
  
  • Giardia
  • Cryptosporidium (in immunocompromised)
• V. cholerae
  
  • Comma-shaped organisms
  • Rice-water diarrhea
  • Often from infected seafood
• Viruses
  
  • Rotavirus, norovirus

Question 7

Common causes of pneumonia

• Neonates (<4 wk)
• Children (4 wk - 18 yr)
• Adults (18-40 yr)
• Adults (40-65 yr)
• Elderly

Answer 7

• Neonates (<4 wk)
  
  • Group B streptococci
  • E. coli
• Children (4 wk - 18 yr)
  
  • Viruses (RSV)
  • Mycoplasma
  • C. trachomatis (infants–3 yr)
  • C. pneumoniae (school-aged children)
  • S. pneumoniae
  • Runts May Cough Chunky Sputum
• Adults (18-40 yr)
  
  • Mycoplasma
  • C. pneumoniae
  • S. pneumoniae
• Adults (40-65 yr)
  
  • S. pneumoniae
  • H. influenzae
  • Anaerobes
  • Viruses
  • Mycoplasma
• Elderly
  
  • S. pneumoniae
  • Influenza virus
  • Anaerobes
  • H. influenzae
  • Gram-negative rods

Question 8

Causes of special groups

• Alcoholic/IV drug user
• Aspiration
• Atypical
• Cystic fibrosis
• Immunocompromised
• Nosocomial (hospital acquired)
• Postviral

Answer 8

• Alcoholic/IV drug user
  
  • S. pneumoniae, Klebsiella, Staphylococcus
• Aspiration
  
  • Anaerobes
• Atypical
  
  • Mycoplasma, Legionella, Chlamydia
• Cystic fibrosis
  
  • Pseudomonas, S. aureus, S. pneumoniae
• Immunocompromised
  
  • Staphylococcus, enteric gram-negative rods, fungi, viruses, P. jirovecii (with HIV)
• Nosocomial (hospital acquired)
  
  • Staphylococcus, Pseudomonas, other enteric gram-negative rods
• Postviral
  
  • Staphylococcus, H. influenzae, S. pneumoniae

Question 9

Common causes of meningitis

• Newborn (0-6 mo)
• Children (6 mo - 6 yr)
• Adults (6-60 yr)
• Elderly (60 yr+)
• Treatment
• Viral causes
• In HIV
• Incidence of H. influenzae meningitis

Answer 9

• Newborn (0-6 mo)
  
  • Group B streptococci
  • E. coli
  • Listeria
• Children (6 mo - 6 yr)
  
  • S. pneumoniae
  • N. meningitidis
  • H. influenzae type B
  • Enteroviruses
• Adults (6-60 yr)
  
  • S. pneumoniae
  • N. meningitidis (#1 in teens)
  • Enteroviruses
  • HSV
• Elderly (60 yr+)
  
  • S. pneumoniae
  • Gram-negative rods
  • Listeria
• Treatment
  
  • Give ceftriaxone and vancomycin empirically
  • Add ampicillin if Listeria is suspected
• Viral causes
  
  • Enteroviruses (esp. coxsackievirus), HSV-2 (HSV-1 = encephalitis), HIV, West Nile virus, VZV.
• In HIV
  
  • Cryptococcus, CMV, toxoplasmosis (brain abscess), JC virus (PML).
• Incidence of H. influenzae meningitis
  
  • Has decreased greatly with introduction of the conjugate H. influenzae vaccine in last 10–15 years.
  • Today, cases are usually seen in unimmunized children.

Question 10

CSF findings in meningitis

• For each
  
  • Opening pressure
  • Cell type
  • Protein
  • Sugar
• Bacterial
• Fungal / TB
• Viral

Answer 10

• Bacterial
  
  • Opening pressure: increased
  • Cell type: increased PMNs
  • Protein: increased
  • Sugar: decreased
• Fungal / TB
  
  • Opening pressure: increased
  • Cell type: increased lymphocytes
  • Protein: increased
  • Sugar: decreased
• Viral
  
  • Opening pressure: normal / increased
  • Cell type: increased lymphocytes
  • Protein: normal / increased
  • Sugar: normal

Question 11

Osteomyelitis

• Causes of risk factors
  
  • Assume if no other information is available
  • Sexually active
  • Diabetics and IV drug users
  • Sickle cell
  • Prosthetic joint replacement
  • Vertebral involvement
  • Cat and dog bites
• Most osteomyelitis occurs in…
• Diagnosis

Answer 11

• Risk factors & cause(s)
  
  • Assume if no other information is available
    
    • S. aureus (most common overall)
  • Sexually active
    
    • Neisseria gonorrhoeae (rare)
    • Septic arthritis (more common)
  • Diabetics and IV drug users
    
    • Pseudomonas aeruginosa
    • Serratia
  • Sickle cell
    
    • Salmonella
  • Prosthetic joint replacement
    
    • S. aureus
    • S. epidermidis
  • Vertebral involvement
    
    • Mycobacterium tuberculosis (Pott disease)
  • Cat and dog bites
    
    • Pasteurella multocida
• Most osteomyelitis occurs in children.
• Diagnosis
  
  • Elevated CRP and ESR observed but nonspecific.
  • Can be subtle on radiographs (arrow in [A])
  • Same lesion more easily seen on MRI [B].

Question 12

Urinary tract infections

• Cystitis
• Pyelonephritis
• Gender
• Predisposing factors
• Diagnostic markers

Answer 12

• Cystitis
  
  • Presents with dysuria, frequency, urgency, suprapubic pain, and WBCs (but not WBC casts) in urine.
  • Primarily caused by ascension of microbes from urethra to bladder.
  • Males— infants with congenital defects, vesicoureteral reflux.
  • Elderly—enlarged prostate.
• Pyelonephritis
  
  • Ascension to kidney results in pyelonephritis
  • Presents with fever, chills, flank pain, costovertebral angle tenderness, hematuria, and WBC casts.
• Gender
  
  • Ten times more common in women (shorter urethras colonized by fecal flora).
• Predisposing factors
  
  • Obstruction, kidney surgery, catheterization, GU malformation, diabetes, and pregnancy.
• Diagnostic markers
  
  • Leukocyte esterase test (+) = bacterial UTI
  • Nitrite test (+) = gram-negative bacterial UTI.

Question 13

UTI bugs

• Species & features (9)
• Diagnostic markers
  
  • (+) Leukocyte esterase
  • (+) Nitrite test
  • (+) Urease test
  • (-) Urease test

Answer 13

• Species & features
  
  • Escherichia coli
    
    • Leading cause of UTI.
    • Colonies show green metallic sheen on EMB agar.
  • Staphylococcus saprophyticus
    
    • 2nd leading cause of UTI in sexually active women.
  • Klebsiella pneumoniae
    
    • 3rd leading cause of UTI.
    • Large mucoid capsule and viscous colonies.
  • Serratia marcescens
    
    • Some strains produce a red pigment
    • Often nosocomial and drug resistant.
  • Enterobacter cloacae
    
    • Often nosocomial and drug resistant.
  • Proteus mirabilis
    
    • Motility causes “swarming” on agar
    • Produces urease
    • Associated with struvite stones.
  • Pseudomonas aeruginosa
    
    • Blue-green pigment and fruity odor
    • Usually nosocomial and drug resistant.
• Diagnostic markers
  
  • (+) Leukocyte esterase = bacterial.
  • (+) Nitrite test = gram-negative bugs.
  • (+) Urease test = urease-producing bugs (e.g., Proteus, Klebsiella).
  • (-) Urease test = E. coli, Enterococcus.

Question 14

Common vaginal infections

• For each
  
  • Signs and symptoms
  • Lab findings
  • Treatment
• Bacterial vaginosis
• Trichomoniasis
• Candida vulvovaginitis

Answer 14

• Bacterial vaginosis
  
  • Signs and symptoms
    
    • No inflammation
    • Thin, white discharge with fishy odor
  • Lab findings
    
    • Clue cells
    • pH > 4.5
  • Treatment
    
    • Metronidazole
• Trichomoniasis
  
  • Signs and symptoms
    
    • Inflammation
    • Frothy, grey-green, foul-smelling discharge
  • Lab findings
    
    • Motile trichomonads
    • pH > 4.5
  • Treatment
    
    • Metronidazole
    • Treat sexual partner
• Candida vulvovaginitis
  
  • Signs and symptoms
    
    • Inflammation
    • Thick, white, “cottage cheese” discharge
  • Lab findings
    
    • Pseudohyphae
    • pH normal (4.0–4.5)
  • Treatment
    
    • -azoles

Question 15

ToRCHeS infections

• Microbes
• Transmission
• Nonspecific signs common to many ToRCHeS infections
• ToRCHeS infectious agents
• Other important infectious agents

Answer 15

• Microbes
  
  • May pass from mother to fetus.
• Transmission
  
  • Transplacental in most cases, or via delivery (especially HSV-2).
• Nonspecific signs common to many ToRCHeS infections
  
  • Hepatosplenomegaly, jaundice, thrombocytopenia, and growth retardation.
• ToRCHeS infectious agents
  
  • Toxoplasma gondii, Rubella, CMV, HIV, Herpes simplex virus-2, Syphilis
• Other important infectious agents
  
  • Include Streptococcus agalactiae (group B streptococci), E. coli, and Listeria monocytogenes—all causes of meningitis in neonates.
  • Parvovirus B19 causes hydrops fetalis.

Question 16

ToRCHeS infections:
Toxoplasma gondii

• Mode of transmission
• Maternal manifestations
• Neonatal manifestations

Answer 16

• Mode of transmission
  
  • Cat feces or ingestion of undercooked meat
• Maternal manifestations
  
  • Usually asymptomatic
  • Lymphadenopathy (rarely)
• Neonatal manifestations
  
  • Classic triad: chorioretinitis, hydrocephalus, and intracranial calcifications

Question 17

ToRCHeS infections:
Rubella

• Mode of transmission
• Maternal manifestations
• Neonatal manifestations

Answer 17

• Mode of transmission
  
  • Respiratory droplets
• Maternal manifestations
  
  • Rash, lymphadenopathy, arthritis
• Neonatal manifestations
  
  • Classic triad: PDA (or pulmonary artery hypoplasia), cataracts, and deafness +- “blueberry muffin” rash

Question 18

ToRCHeS infections:
CMV

• Mode of transmission
• Maternal manifestations
• Neonatal manifestations

Answer 18

• Mode of transmission
  
  • Sexual contact, organ transplants
• Maternal manifestations
  
  • Usually asymptomatic
  • Mononucleosis-like illness
• Neonatal manifestations
  
  • Hearing loss, seizures, petechial rash, “blueberry muffin” rash

Question 19

ToRCHeS infections:
HIV

• Mode of transmission
• Maternal manifestations
• Neonatal manifestations

Answer 19

• Mode of transmission
  
  • Sexual contact, needlestick
• Maternal manifestations
  
  • Variable presentation depending on CD4+ count
• Neonatal manifestations
  
  • Recurrent infections, chronic diarrhea

Question 20

ToRCHeS infections:
Herpes simplex virus-2

• Mode of transmission
• Maternal manifestations
• Neonatal manifestations

Answer 20

• Mode of transmission
  
  • Skin or mucous membrane contact
• Maternal manifestations
  
  • Usually asymptomatic
  • Herpetic (vesicular) lesions
• Neonatal manifestations
  
  • Encephalitis, herpetic (vesicular) lesions

Question 21

ToRCHeS infections:
Syphilis

• Mode of transmission
• Maternal manifestations
• Neonatal manifestations

Answer 21

• Mode of transmission
  
  • Sexual contact
• Maternal manifestations
  
  • Chancre (1°) and disseminated rash (2°) are the two stages likely to result in fetal infection
• Neonatal manifestations
  
  • Often results in stillbirth, hydrops fetalis
  • If child survives, presents with facial abnormalities [A] (notched teeth [B], saddle nose, short maxilla), saber shins, CN VIII deafness

Question 22

Agents of red rashes of childhood (7)

Answer 22

• Coxsackievirus type A
• HHV-6
• Measles virus
• Parvovirus B19
• Rubella virus
• Streptococcus pyogenes
• VZV

Question 23

Red rashes of childhood:
Coxsackievirus type A

• Associated syndrome / disease
• Clinical presentation

Answer 23

• Associated syndrome / disease
  
  • Hand-foot-mouth disease
• Clinical presentation
  
  • Vesicular rash on palms and soles [A]
  • Vesicles and ulcers in oral mucosa

Question 24

Red rashes of childhood:
HHV-6

• Associated syndrome / disease
• Clinical presentation

Answer 24

• Associated syndrome / disease
  
  • Roseola
• Clinical presentation
  
  • A macular rash over body appears after several days of high fever
  • Can present with febrile seizures
  • Usually affects infants

Question 25

Red rashes of childhood: Measles virus * Associated syndrome / disease * Clinical presentation

Answer 25

* Associated syndrome / disease * Measles (rubeola) * Clinical presentation * A paramyxovirus * Beginning at head and moving down * Rash is preceded by cough, coryza, conjunctivitis, and blue-white (Koplik) spots on buccal mucosa

Question 26

Red rashes of childhood: Parvovirus B19 * Associated syndrome / disease * Clinical presentation

Answer 26

* Associated syndrome / disease * Erythema infectiosum (fifth disease) * Clinical presentation * “Slapped cheek” rash on face [B] * Can cause hydrops fetalis in pregnant women

Question 27

Red rashes of childhood: Rubella virus * Associated syndrome / disease * Clinical presentation

Answer 27

* Associated syndrome / disease * Rubella * Clinical presentation * Rash begins at head and moves down * --\> fine truncal rash * Postauricular lymphadenopathy

Question 28

Red rashes of childhood: Streptococcus pyogenes * Associated syndrome / disease * Clinical presentation

Answer 28

* Associated syndrome / disease * Scarlet fever * Clinical presentation * Erythematous, sandpaper-like rash with fever and sore throat

Question 29

Red rashes of childhood: VZV * Associated syndrome / disease * Clinical presentation

Answer 29

* Associated syndrome / disease * Chickenpox * Clinical presentation * Vesicular rash begins on trunk * Spreads to face and extremities with lesions of different ages

Question 30

Sexually transmitted diseases * For each * Clinical features * Organism * Aids * Chancroid * Chlamydia * Condylomata acuminata * Genital herpes * Gonorrhea

Answer 30

* AIDS * _Clinical features_: Opportunistic infections, Kaposi sarcoma, lymphoma * _Organism_: HIV * Chancroid * _Clinical features_: Painful genital ulcer, inguinal adenopathy * _Organism_: Haemophilus **_ducreyi_** * **It’s so painful, you “_do cry_”** * Chlamydia * _Clinical features_: Urethritis, cervicitis, conjunctivitis, reactive arthritis, PID * _Organism_: Chlamydia trachomatis (D–K) * Condylomata acuminata * _Clinical features_: Genital warts, koilocytes * _Organism_: HPV-6 and -11 * Genital herpes * _Clinical features_: Painful penile, vulvar, or cervical vesicles and ulcers * Can cause systemic symptoms such as fever, headache, myalgia * _Organism_: HSV-2, less commonly HSV-1 * Gonorrhea * _Clinical features_: Urethritis, cervicitis, PID, prostatitis, epididymitis, arthritis, creamy purulent discharge * _Organism_: Neisseria gonorrhoeae

Question 31

Sexually transmitted diseases * For each * Clinical features * Organism * Hepatitis B * Lymphogranuloma venereum * 1° syphilis * 2° syphilis * 3° syphilis * Trichomoniasis

Answer 31

* Hepatitis B * _Clinical features_: Jaundice * _Organism_: HBV * Lymphogranuloma venereum * _Clinical features_: Infection of lymphatics * Painless genital ulcers, painful lymphadenopathy (i.e., buboes) * _Organism_: C. trachomatis (L1–L3) * 1° syphilis * _Clinical features_: Painless chancre * _Organism_: Treponema pallidum * 2° syphilis * _Clinical features_: Fever, lymphadenopathy, skin rashes, condylomata lata * _Organism_: Treponema pallidum * 3° syphilis * _Clinical features_: Gummas, tabes dorsalis, general paresis, aortitis, Argyll Robertson pupil * _Organism_: Treponema pallidum * Trichomoniasis * _Clinical features_: Vaginitis, strawberry cervix, motile in wet prep * _Organism_: Trichomonas vaginalis

Question 32

Pelvic inflammatory disease * Top bugs * Manifestations

Answer 32

* Top bugs * Chlamydia trachomatis (subacute, often undiagnosed) * The most common bacterial STD in the United States. * Neisseria gonorrhoeae (acute). * Manifestations * Cervical motion tenderness (chandelier sign), purulent cervical discharge [A]. * PID may include salpingitis, endometritis, hydrosalpinx, and tubo-ovarian abscess. * Can lead to **Fitz- Hugh–Curtis syndrome**—infection of the liver capsule and “violin string” adhesions of peritoneum to liver [B]. * Salpingitis is a risk factor for ectopic pregnancy, infertility, chronic pelvic pain, and adhesions.

Question 33

Nosocomial infections * Candida albicans * Risk factor * CMV, RSV * Risk factor * E. coli, Proteus mirabilis * Risk factor * Notes * HBV * Risk factor * Legionella * Risk factor * Notes * Pseudomonas aeruginosa * Risk factor * Notes

Answer 33

* Candida albicans * _Risk factor_: Hyperalimentation * CMV, RSV * _Risk factor_: Newborn nursery * E. coli, Proteus mirabilis * _Risk factor_: Urinary catheterization * _Notes_: The 2 most common causes of nosocomial infections are E. coli (UTI) and S. aureus (wound infection). * HBV * _Risk factor_: Work in renal dialysis unit * Legionella * _Risk factor_: Water aerosols * _Notes_: Think Legionella when water source is involved. * Pseudomonas aeruginosa * _Risk factor_: Respiratory therapy equipment * _Notes_: Presume Pseudomonas “**_air_**uginosa” when **_air_** or burns are involved.

Question 34

Bugs affecting unimmunized children: Dermatologic: Rash * Findings / labs and associated pathogens (2)

Answer 34

* Beginning at head and moving down with postauricular lymphadenopathy * Rubella virus * Beginning at head and moving down; rash preceded by cough, coryza, conjunctivitis, and blue-white (Koplik) spots on buccal mucosa * Measles virus

Question 35

Bugs affecting unimmunized children: Neurologic: Meningitis * Findings / labs and associated pathogens (2)

Answer 35

* Microbe colonizes nasopharynx * H. influenzae type B * Can also lead to myalgia and paralysis * Poliovirus

Question 36

Bugs affecting unimmunized children: Respiratory * Epiglottitis * Findings / labs * Associated pathogen * Pharyngitis * Findings / labs * Associated pathogen

Answer 36

* Epiglottitis * Fever with dysphagia, drooling, and difficulty breathing due to edematous “cherry red” epiglottis; “thumbprint sign” on X-ray * H. influenzae type B (also capable of causing epiglottitis in fully immunized children) * Pharyngitis * Grayish oropharyngeal exudate (“pseudomembranes” may obstruct airway); painful throat * Corynebacterium diphtheriae (elaborates toxin that causes necrosis in pharynx, cardiac, and CNS tissue)

Question 37

Bug hints * Asplenic patient (due to surgical splenectomy or autosplenectomy, e.g., chronic sickle cell anemia) * Branching rods in oral infection, sulfur granules * Chronic granulomatous disease * “Currant jelly” sputum * Dog or cat bite * Facial nerve palsy * Fungal infection in diabetic or immunocompromised patient * Health care provider * Neutropenic patients

Answer 37

* Asplenic patient (due to surgical splenectomy or autosplenectomy, e.g., chronic sickle cell anemia) * Encapsulated microbes, especially **_SHiN_** (**_S_**. pneumoniae \>\> **_H_**. **_i_**nfluenzae type B \> **_N_**. meningitidis) * Branching rods in oral infection, sulfur granules * Actinomyces israelii * Chronic granulomatous disease * Catalase (+) microbes, especially S. aureus * “Currant jelly” sputum * Klebsiella * Dog or cat bite * Pasteurella multocida * Facial nerve palsy * Borrelia burgdorferi (Lyme disease) * Fungal infection in diabetic or immunocompromised patient * Mucor or Rhizopus spp. * Health care provider * HBV (from needle stick)

Question 38

Bug hints * Neutropenic patients * Organ transplant recipient * PAS (+) * Pediatric infection * Pneumonia in cystic fibrosis, burn infection * Pus, empyema, abscess S * Rash on hands and feet * Sepsis/meningitis in newborn * Surgical wound * Traumatic open wound

Answer 38

* Neutropenic patients * Candida albicans (systemic), Aspergillus * Organ transplant recipient * CMV * PAS (+) * Tropheryma whipplei (Whipple disease) * Pediatric infection * Haemophilus influenzae (including epiglottitis) * Pneumonia in cystic fibrosis, burn infection * Pseudomonas aeruginosa * Pus, empyema, abscess * S. aureus * Rash on hands and feet * Coxsackie A virus, Treponema pallidum, Rickettsia rickettsii * Sepsis/meningitis in newborn * Group B strep * Surgical wound * S. aureus * Traumatic open wound * Clostridium perfringens