Microbiology- Systems Flashcards
Normal flora: dominant
Skin Nose Oropharynx Dental plaque Colon Vagina
S epidermidis
S epidermidis; colonized by S aureus
Viridans group streptococci
S mutans
B fragilis > E coli
Lactobacillus; colonized by E coli and group B strep
Bugs causing foodborne illness
B cereus C botulinum C perfringens E coli O157:H7 L monocytogenes Salmonella S aureus V parahaemolyticus and V vulnificus
Bloody diarrhea
Campylobacter E histolytica Enterohemorrhagic Ecoli Enteroinvasive E coli Salmonella (nontyphoidal) Shigella Y enterocolitica
Watery diarrhea
C difficile C perfringens Enterotoxigenic E coli Protozoa V cholerae Viruses (Rotavirus, norovirus, enteric adenovirus)
Common causes of pneumonia
Children (4 weeks - 18 years)
“Runts May Cough Chunky Sputum”
Viruses (RSV) Mycoplasma C trachomatis (infants–3 yr) C pneumoniae (school-aged children) S pneumoniae
Common causes of pneumonia
Adults (18 - 40 years)
Mycoplasma
C pneumoniae
S pneumoniae
Viruses (eg, influenza)
Common causes of pneumonia
Adults (18 - 40 years)
Mycoplasma
C pneumoniae
S pneumoniae
Viruses (eg, influenza)
Common causes of pneumonia
Adults (40 - 60 years)
S pneumoniae H influenzae Anaerobes Viruses Mycoplasma
Common causes of pneumonia
Adults (more than 60 years)
S pneumoniae Influenza virus Anaerobes H influenzae Gram ⊝ rods
Common causes of pneumonia (Special groups)
Alcoholic
Klebsiella, anaerobes usually due to aspiration (eg, Peptostreptococcus, Fusobacterium, Prevotella,
Bacteroides)
Common causes of pneumonia (Special groups)
- IV drug users
- Aspiration
- S pneumoniae, S aureus
- Anaerobes
Common causes of pneumonia (Special groups)
Atypical
Mycoplasma, Chlamydophila, Legionella, viruses (RSV, CMV, influenza, adenovirus)
Common causes of pneumonia (Special groups)
Cystic fibrosis
Pseudomonas, S aureus, S pneumoniae, Burkholderia cepacia
Common causes of pneumonia (Special groups)
Immunocompromised
S aureus, enteric gram ⊝ rods, fungi, viruses, P jirovecii (with HIV).
Common causes of pneumonia (Special groups)
Nosocomial (hospital acquired)
S aureus, Pseudomonas, other enteric gram ⊝ rods
Common causes of pneumonia (Special groups)
Postviral
S pneumoniae, S aureus, H influenzae
Common causes of meningitis
- newborn (0- 6months)
- Children (6months- 6 years)
- 6-60 years
- +60 years
- Group B streptococci, E coli, Listeria
- S pneumoniae, N meningitidis, H influenzae type b
Enteroviruses - S pneumoniae, N meningitidis (#1 in teens), Enteroviruses, HSV
S pneumoniae, Gram ⊝ rods, Listeria
Viral causes of meningitis:
enteroviruses (especially coxsackievirus), HSV-2 (HSV-1 = encephalitis), HIV, West Nile virus (also causes encephalitis), VZV.
Cerebrospinal fluid findings in meningitis: opening pressure, cells, protein, glucose
- Bacterial
- Fungal/TB
- Virus
- high, PMNs, High, Low
- High, Lymphocytes, High, Low
- Normal/high, Lymphocytes, High/normal, Normal
Infections causing
brain abscess
Most commonly viridans streptococci and Staphylococcus aureus. If dental infection or extraction
precedes abscess, oral anaerobes commonly involved.
Multiple abscesses are usually from bacteremia; single lesions from contiguous sites: otitis media and mastoiditis temporal lobe and cerebellum; sinusitis or dental infection frontal lobe.
Toxoplasma reactivation in AIDS.
Osteomyelitis, Risk factor:
- Assume if no other information is available:
- Sexually active:
- Sickle cell disease:
- Prosthetic joint replacement:
- Vertebral involvement:
- Cat and dog bites:
- IV drug abuse:
- S aureus (most common overall)
- Neisseria gonorrhoeae (rare), septic arthritis more common.
- Salmonella and S aureus
- S aureus and S epidermidis
- S aureus, Mycobacterium tuberculosis (Pott disease)
- Pasteurella multocida
- S aureus; also Pseudomonas, Candida
Osteomyelitis Diagnosis
MRI is best for detecting acute infection and detailing anatomic involvement.
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.
Ascension to kidney results in pyelonephritis, which presents with fever, chills, flank pain, costovertebral angle tenderness, hematuria, and WBC casts.
Urinary tract infections Predisposing factors
Obstruction, kidney surgery, catheterization, GU malformation, diabetes, pregnancy.
Males—infants with congenital defects, vesicoureteral reflux.
Elderly—enlarged prostate.
Urinary tract infections Diagnostic markers:
⊕ Leukocyte esterase = evidence of WBC activity.
⊕ Nitrite test = reduction of urinary nitrates by bacterial species (eg, E coli).
⊕ Urease test = urease-producing bugs (eg, Ssaprophyticus, Proteus, Klebsiella)
Urinary tract infections Agents
- Escherichia coli
- Staphylococcus saprophyticus
- Klebsiella pneumoniae (3rd leading cause of UTI)
- Serratia marcescens (Some strains produce a red pigment)
- Enterococcus
- Proteus mirabilis ( causes “swarming” on agar; associated with struvite stones)
- Pseudomonas aeruginosa (Blue-green pigment and fruity odor)
Common vaginal infections
Bacterial vaginosis: No inflammation. Thin, white discharge with fishy odor. Clue cells. Metronidazole or clyndamicin.
Trichomonas vaginitis: Inflammation (“strawberry cervix”).
Frothy, yellow-green, foulsmelling discharge. metronidazole (treat sexual partner)
Candida vulvovaginitis: Inflammation. Thick, white, “cottage cheese” discharge. Pseudohyphae. Azoles
ToRCHeS infections
Transmission is transplacental in most cases, or via delivery (especially HSV-2).
Nonspecific signs common to many ToRCHeS infections include hepatosplenomegaly, jaundice, thrombocytopenia, and growth retardation.
Toxoplasma, Rubella, Cytomegalovirus, HIV, Herpes simplex virus-2, Syphilis
ToRCHeS infections:
Toxoplasma gondii
Classic triad: chorioretinitis, hydrocephalus, and
intracranial calcifications, +/−“blueberry muffin” rash.
*mother asymptomatic
ToRCHeS infections:
Rubella
Classic triad: abnormalities of eye (cataract) and ear
(deafness) and congenital heart disease (PDA); ± “blueberry muffin” rash.
*mother: Rash, lymphadenopathy, polyarthritis, polyarthralgia
ToRCHeS infections:
Cytomegalovirus
Hearing loss, seizures, petechial rash, “blueberry muffin” rash, chorioretinitis, periventricular calcifications
*mother: Usually asymptomatic; mononucleosis-like illness
ToRCHeS infections:
HIV
Recurrent infections, chronic diarrhea
ToRCHeS infections:
Herpes simplex virus-2
Meningoencephalitis, herpetic (vesicular) lesions
- mother: Usually asymptomatic; herpetic
(vesicular) lesions
ToRCHeS infections:
Syphilis
Often results in stillbirth, hydrops fetalis; if child survives, presents with facial abnormalities (eg, notched
teeth, saddle nose, short maxilla), saber shins, CN VIII
deafness.
*mother: Chancre (1°) and disseminated rash (2°)
Red rashes of childhood (pag 183)
Coxsackievirus type A: Hand-foot-mouth disease
Human herpesvirus 6: Roseola (exanthem subitum)
Measles virus: Measles (rubeola)
Parvovirus B19: Erythema infectiosum (fifth disease)
Rubella virus: Rubella
Streptococcus pyogenes: Scarlet fever
Varicella-Zoster virus: Chickenpox
Sexually transmitted infections Disease and Agent
- AIDS
- Chancroid
- Chlamydia
- Condylomata acuminata
- Genital herpes
- Opportunistic infections, Kaposi sarcoma, lymphoma. HIV
- Painful genital ulcer with exudate, inguinal adenopathy. Haemophilus ducreyi (it’s so painful, you “do cry”).
- Urethritis, cervicitis, epididymitis, conjunctivitis, reactive arthritis, PID. Chlamydia trachomatis (D–K)
- Genital warts, koilocytes. HPV-6 and -11
- Painful penile, vulvar, or cervical vesicles and ulcers; can cause systemic symptoms such as fever, headache, myalgia. HSV-2, less commonly HSV-1
Sexually transmitted infections Disease and Agent
- Gonorrhea
- Granuloma inguinale (Donovanosis)
- Hepatitis B
- Lymphogranuloma venereum
- Urethritis, cervicitis, PID, prostatitis, epididymitis, arthritis, creamy purulent discharge. Neisseria gonorrhoeae
- Painless, beefy red ulcer that bleeds readily on contact. Klebsiella (Calymmatobacterium) granulomatis;
cytoplasmic Donovan bodies (bipolar staining) seen on microscopy. - Jaundice. HBV
- Infection of lymphatics; painless genital ulcers, painful lymphadenopathy (ie, buboes). C trachomatis (L1–L3)
Sexually transmitted infections Disease and Agent
- Primary syphilis
- Secondary syphilis
- Tertiary syphilis
- Trichomoniasis
- Painless chancre. Treponema pallidum
- Fever, lymphadenopathy, skin rashes. condylomata lata
- Gummas, tabes dorsalis, general paresis, aortitis, Argyll Robertson pupil
- Vaginitis, strawberry cervix, motile in wet prep. Trichomonas vaginalis
Pelvic inflammatory disease
Top bugs—Chlamydia trachomatis (subacute, often undiagnosed), Neisseria gonorrhoeae (acute).
Signs include cervical motion tenderness, adnexal tenderness, purulent cervical discharge.
PID may include salpingitis, endometritis, hydrosalpinx, and tubo-ovarian abscess.
Can lead to perihepatitis (Fitz-Hugh–Curtis syndrome)—infection and inflammation of liver capsule and “violin string” adhesions of peritoneum to liver.
Nosocomial infections Risk factors:
- Antibiotic use
- Aspiration (2° to altered mental status, old age)
- Decubitus ulcers, surgical wounds, drains
- Intravascular catheters
- Clostridium difficile. Watery diarrhea, leukocytosis
- Polymicrobial, gram ⊝ bacteria, often anaerobes. Right lower lobe infiltrate or right upper/ middle lobe (patient recumbent); purulent malodorous sputum.
- S aureus (including MRSA), gram ⊝ anaerobes(Bacteroides, Prevotella, Fusobacterium). Erythema, tenderness, induration, drainage from surgical wound sites.
- S aureus (including MRSA), S epidermidis (long
term) , Enterobacter. Erythema, induration, tenderness, drainage from access sites
Nosocomial infections Risk factors:
- Mechanical ventilation, endotracheal, intubation
- Renal dialysis unit, needlestick
- Urinary catheterization
- Water aerosols
- Late onset: P aeruginosa, Klebsiella, Acinetobacter, S aureus. New infiltrate on CXR, sputum production; sweet odor (Pseudomonas).
- HBV, HCV
- Proteus spp, E coli, Klebsiella. Dysuria, leukocytosis, flank pain or costovertebral angle tenderness.
- Legionella. Signs of pneumonia, GI symptoms (diarrhea, nausea, vomiting), neurologic abnormalities
Bugs affecting unvaccinated children:
Rash
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
Bugs affecting unvaccinated children:
Meningitis
Microbe colonizes nasopharynx. H influenzae type b
Can also lead to myalgia and paralysis. Poliovirus
Bugs affecting unvaccinated children:
Respiratory
Epiglottitis. H influenzae type b
Pharyngitis. Corynebacterium diphtheriae
Bugs hints
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