Microbiology - Systems Flashcards
1
Q
Normal (dominant) flora
- Skin
- Nose
- Oropharynx
- Dental plaque
- Colon
- Vagina
- Neonates delivered by C-section
A
- 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
2
Q
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
A
- 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
3
Q
Bugs causing bloody diarrhea (7)
A
- Campylobacter
- E. histolytica
- Enterohemorrhagic E. coli
- Enteroinvasive E. coli
- Salmonella
- Shigella
- Y. enterocolitica
4
Q
Bugs causing bloody diarrhea
- Campylobacter
- E. histolytica
- Enterohemorrhagic E. coli
- Enteroinvasive E. coli
- Salmonella
- Shigella
- Y. enterocolitica
A
- 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
5
Q
Bugs causing watery diarrhea (6)
A
- C. difficile
- C. perfringens
- Enterotoxigenic E. coli
- Protozoa
- V. cholerae
- Viruses
6
Q
Bugs causing watery diarrhea
- C. difficile
- C. perfringens
- Enterotoxigenic E. coli
- Protozoa
- V. cholerae
- Viruses
A
- 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
7
Q
Common causes of pneumonia
- Neonates (<4 wk)
- Children (4 wk - 18 yr)
- Adults (18-40 yr)
- Adults (40-65 yr)
- Elderly
A
- 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
8
Q
Causes of special groups
- Alcoholic/IV drug user
- Aspiration
- Atypical
- Cystic fibrosis
- Immunocompromised
- Nosocomial (hospital acquired)
- Postviral
A
- 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
9
Q
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
A
- 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.
10
Q
CSF findings in meningitis
- For each
- Opening pressure
- Cell type
- Protein
- Sugar
- Bacterial
- Fungal / TB
- Viral
A
- 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
11
Q
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
A
- 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
- Assume if no other information is available
- 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].
12
Q
Urinary tract infections
- Cystitis
- Pyelonephritis
- Gender
- Predisposing factors
- Diagnostic markers
A
- 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.
13
Q
UTI bugs
- Species & features (9)
- Diagnostic markers
- (+) Leukocyte esterase
- (+) Nitrite test
- (+) Urease test
- (-) Urease test
A
- 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.
- Escherichia coli
- Diagnostic markers
- (+) Leukocyte esterase = bacterial.
- (+) Nitrite test = gram-negative bugs.
- (+) Urease test = urease-producing bugs (e.g., Proteus, Klebsiella).
- (-) Urease test = E. coli, Enterococcus.
14
Q
Common vaginal infections
- For each
- Signs and symptoms
- Lab findings
- Treatment
- Bacterial vaginosis
- Trichomoniasis
- Candida vulvovaginitis
A
- Bacterial vaginosis
- Signs and symptoms
- No inflammation
- Thin, white discharge with fishy odor
- Lab findings
- Clue cells
- pH > 4.5
- Treatment
- Metronidazole
- Signs and symptoms
- Trichomoniasis
- Signs and symptoms
- Inflammation
- Frothy, grey-green, foul-smelling discharge
- Lab findings
- Motile trichomonads
- pH > 4.5
- Treatment
- Metronidazole
- Treat sexual partner
- Signs and symptoms
- Candida vulvovaginitis
- Signs and symptoms
- Inflammation
- Thick, white, “cottage cheese” discharge
- Lab findings
- Pseudohyphae
- pH normal (4.0–4.5)
- Treatment
- -azoles
- Signs and symptoms
15
Q
ToRCHeS infections
- Microbes
- Transmission
- Nonspecific signs common to many ToRCHeS infections
- ToRCHeS infectious agents
- Other important infectious agents
A
- 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.
21
Q
ToRCHeS infections:
Syphilis
- Mode of transmission
- Maternal manifestations
- Neonatal manifestations
A
- 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
23
Q
Red rashes of childhood:
Coxsackievirus type A
- Associated syndrome / disease
- Clinical presentation
A
- Associated syndrome / disease
- Hand-foot-mouth disease
- Clinical presentation
- Vesicular rash on palms and soles [A]
- Vesicles and ulcers in oral mucosa
26
Q
Red rashes of childhood:
Parvovirus B19
- Associated syndrome / disease
- Clinical presentation
A
- Associated syndrome / disease
- Erythema infectiosum (fifth disease)
- Clinical presentation
- “Slapped cheek” rash on face [B]
- Can cause hydrops fetalis in pregnant women
32
Q
Pelvic inflammatory disease
- Top bugs
- Manifestations
A
- Top bugs
- Chlamydia trachomatis (subacute, often undiagnosed)
- The most common bacterial STD in the United States.
- Neisseria gonorrhoeae (acute).
- Chlamydia trachomatis (subacute, often undiagnosed)
- 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.
