Microbiology - Clinical Bacteriology Flashcards

Question

Haemophilus influenzae * Properties * Culture * Causes... * Treatment * Mucosal infections * Meningitis * Prophylaxis

Answer 1

* Properties * Small gram-negative (coccobacillary) rod. * Aerosol transmission. * Most invasive disease caused by capsular type B. * Nontypeable strains cause mucosal infections (otitis media, conjunctivitis, bronchitis). * Produces IgA protease. * Culture * Culture on **_chocolate_** agar requires factors **_V_** (NAD+) and **_X_** (hematin) for growth * Can also be grown with S. aureus, which provides factor V. * **When a child has “flu,” mom goes to five (_V_) and dime (_X_) store to buy some _chocolate_.** * Ha**_EMOP_**hilus causes... * **_E_**piglottitis [A] [B] (“cherry red” in children), **_M_**eningitis, **_O_**titis media, and **_P_**neumonia. * Does not cause the flu (influenza virus does). * Treatment * Treat mucosal infections with amoxicillin +/- clavulanate. * Treat meningitis with ceftriaxone. * Prophylaxis * Rifampin prophylaxis in close contacts. * Vaccine contains type B capsular polysaccharide (polyribosylribitol phosphate) conjugated to diphtheria toxoid or other protein. * Given between 2 and 18 months of age.

Answer 2

* Growth * Gram-negative rod. * Gram stains poorly—use **_silver_** stain. * Grow on **_charcoal_** yeast extract culture with **_iron_** and **_cysteine_**. * **Think of a French _legionnaire_ (soldier) with his _silver_ helmet, sitting around a campfire (_charcoal_) with his _iron_ dagger—he is no _sissy_ (cysteine).** * Detection * Detected clinically by presence of antigen in urine. * Lab shows hyponatremia. * Transmission * Aerosol transmission from environmental water source habitat (e.g., air conditioning systems, hot water tanks). * No person-to-person transmission. * Treatment * Macrolide or quinolone. * **Legionnaires’ disease** * Severe pneumonia, fever, GI and CNS symptoms. * **Pontiac fever** * Mild flu-like syndrome.

Answer 3

* Properties * Aerobic gram-negative rod. * Non-lactose fermenting, oxidase (+). * Produces pyocyanin (blue-green pigment [A]). * Has a grape-like odor. * Water source. * Produces endotoxin (fever, shock) and exotoxin A (inactivates EF-2). * ****_Aer_**uginosa—**_aer_**obic.** * **Think water connection and blue-green pigment.** * **_PSEUDO_**monas is associated with... * Wound and burn infections, **_P_**neumonia (especially in cystic fibrosis), **_S_**epsis, **_E_**xternal otitis (swimmer’s ear), **_U_**TI, **_D_**rug use and **_D_**iabetic **_O_**steomyelitis, and hot tub folliculitis. * **Think Pseudomonas in burn victims.** * Malignant otitis externa in diabetics. * Chronic pneumonia in cystic fibrosis patients is associated with biofilm * **Ecthyma gangrenosum** * Rapidly progressive, necrotic cutaneous lesions caused by Pseudomonas bacteremia. * Typically seen in immunocompromised patients. * Treatment * Aminoglycoside plus extended-spectrum penicillin (e.g., piperacillin, ticarcillin, cefepime, imipenem, meropenem).

Answer 4

* E. coli virulence factors * Fimbriae—cystitis and pyelonephritis * K capsule—pneumonia, neonatal meningitis * LPS endotoxin—septic shock. * E**_I_**EC * _Toxin and mechanism_: * Microbe invades intestinal mucosa and causes necrosis and inflammation. * Clinical manifestations similar to Shigella. * _Presentation_: **_I_**nvasive; dysentery. * E**_T_**EC * _Toxin and mechanism_: * Produces heat-labile and heat-stable entero**_T_**oxins. * No inflammation or invasion. * _Presentation_: **_T_**ravelers’ diarrhea (watery). * E**_P_**EC * _Toxin and mechanism_: * No toxin produced. * Adheres to apical surface, flattens villi, prevents absorption. * _Presentation_: * Diarrhea usually in children (**_P_**ediatrics). * E**_H_**EC * _Toxin and mechanism_: * O157:H7 is the most common serotype. * Produces Shiga-like toxin that causes **_H_**emolytic-uremic syndrome (triad of anemia, thrombocytopenia, and acute renal failure). * Also called STEC (Shiga toxin–producing E. coli). * Microthrombi form on endothelium damaged by toxin --\> mechanical hemolysis (schistocytes formed) and decreased renal blood flow; * Microthrombi consume platelets --\> thrombocytopenia. * _Presentation_: * Dysentery (toxin alone causes necrosis and inflammation). * Does not ferment sorbitol (distinguishes it from other E. coli).

Answer 5

* An intestinal flora that causes lobar pneumonia in alcoholics and diabetics when aspirated. * Very mucoid colonies caused by abundant polysaccharide capsules. * Red “currant jelly” sputum. * Also cause of nosocomial UTIs. * **4 _A_’s:** * **_A_**spiration pneumonia * **_A_**bscess in lungs and liver * **_A_**lcoholics * di-**_A_**-betics

Answer 6

* Flagella? * _Salmonella_: Yes (**salmon** swim) * _Shigella_: No * Transmission * _Salmonella_: Can disseminate hematogenously * _Shigella_: Cell to cell transmission; no hematogenous spread * Reservoirs * _Salmonella_: Have many animal reservoirs * _Shigella_: Only reservoirs are humans and primates * Produce hydrogen sulfide? * _Salmonella_: Yes * _Shigella_: No * Antibiotics... * _Salmonella_: May prolong fecal excretion of organism * _Shigella_: Shorten duration of fecal excretion of organism * Invades intestinal mucosa and causes... * _Salmonella_: A monocytic response * _Shigella_: PMN infiltration * Bloody diarrhea? * _Salmonella_: Can cause * _Shigella_: Often causes * Ferments lactose? * _Salmonella_: No * _Shigella_: No

Answer 7

* Causes typhoid fever. * Found only in humans. * Can remain in gallbladder and cause a carrier state. * Characterized by rose spots on the abdomen, fever, headache, and diarrhea.

Answer 8

* Causes... * Major cause of bloody diarrhea, especially in children. * Common antecedent to Guillain-Barré syndrome and reactive arthritis. * Transmission * Fecal-oral transmission through foods such as poultry, meat, unpasteurized milk. * Properties * Comma or S-shaped * Oxidase (+) * Grows at 42°C * **“**_Camp_**ylobacter likes the hot **_camp_**fire”**

Answer 9

* Causes... * Produces profuse rice-water diarrhea via enterotoxin that permanently activates Gs, increases cAMP. * Properties * Comma shaped * Oxidase (+) * Grows in alkaline media. * Found * Endemic to developing countries. * Treatment * Prompt oral rehydration is necessary.

Answer 10

* Transmission * Usually transmitted from pet feces (e.g., puppies), contaminated milk, or pork. * Causes... * Causes mesenteric adenitis that can mimic Crohn disease or appendicitis.

Answer 11

* Causes... * Causes gastritis and peptic ulcers (especially duodenal). * Risk factor for peptic ulcer, gastric adenocarcinoma and lymphoma. * Creates alkaline environment. * Properties * Curved gram-negative rod * Catalase, oxidase, and urease (+) * Diagnosis * Can use urea breath test or fecal antigen test for diagnosis. * Treatment * Most common initial treatment is triple therapy: proton pump inhibitor + clarithromycin + either amoxicillin or metronidazole.

Answer 12

* Properties * The spirochetes are spiral-shaped bacteria with axial filaments and include **_B_**orrelia (big size), **_L_**eptospira, and **_T_**reponema. * **_BLT_.** * **_B_ is **_B_**ig.** * Diagnosis * Only Borrelia can be visualized using aniline dyes (Wright or Giemsa stain) in light microscopy. * Treponema is visualized by dark-field microscopy.

Answer 13

* Causes leptospirosis * Flu-like symptoms, jaundice, photophobia with conjunctival suffusion (erythema without exudate). * Found... * Found in water contaminated with animal urine * Prevalent among surfers and in tropics (i.e., Hawaii). * **Weil disease (icterohemorrhagic leptospirosis)** * Severe form with jaundice and azotemia from liver and kidney dysfunction * Fever, hemorrhage, and anemia.

Answer 14

* Caused by... * Borrelia burgdorferi, which is transmitted by the tick Ixodes [A] (also vector for Babesia). * Reservoir * Natural reservoir is the mouse. * Mice are important to tick life cycle. * Found... * Common in northeastern United States. * Symptoms * Initial symptoms—erythema chronicum migrans [B], flu-like symptoms, +/- facial nerve palsy. * Later symptoms—monoarthritis (large joints) and migratory polyarthritis, cardiac (AV nodal block), neurologic (encephalopathy, facial nerve palsy, polyneuropathy). * **_FAKE_ a Key _Lyme_ pie:** * **_F_**acial nerve palsy (typically bilateral) * **_A_**rthritis * **_K_**ardiac block * **_E_**rythema migrans * Treatment * Doxycycline, ceftriaxone.

Answer 15

* Caused by... * Spirochete Treponema pallidum. * Treatment * Penicillin G. * 1° syphilis * Localized disease presenting with **painless** chancre [A]. * If available, use dark-field microscopy to visualize treponemes in fluid from chancre [B]. * Serologic testing: VDRL/RPR (non-specifc), confirm diagnosis with specific test (e.g., FTA-ABS). * 2° syphilis * Disseminated disease with constitutional symptoms, maculopapular rash (palms and soles), condylomata lata (also confirmable with dark-field microscopy). * ****_S_**econdary syphilis = **_S_**ystemic** * Serologic testing: VDRL/RPR (non-specific), confirm diagnosis with specific test (e.g., FTA-ABS). * Latent syphilis ((+) serology without symptoms) follows. * 3° syphilis * Gummas (chronic granulomas), aortitis (vasa vasorum destruction), neurosyphilis (tabes dorsalis, “general paresis”), Argyll Robertson pupil. * Signs: broad-based ataxia, (+) Romberg, Charcot joint, stroke without hypertension. * For neurosyphilis: test spinal fluid with VDRL or RPR. * Congenital syphilis * Saber shins, saddle nose, CN VIII deafness, Hutchinson teeth, mulberry molars. * To prevent, treat mother early in pregnancy, as placental transmission typically occurs after first trimester.

Answer 16

* Argyll Robertson pupil constricts with accommodation but is not reactive to light. * Associated with 3° syphilis. * “Prostitute pupil”—accommodates but does not react.

Answer 17

* VDRL detects nonspecific antibody that reacts with beef cardiolipin. * Inexpensive, widely available test for syphilis * Quantitative, sensitive but not specific. * Many false positives, including viral infection (e.g., mononucleosis [EBV], hepatitis), some drugs, and SLE. * **_VDRL_:** * **_V_**iruses (mono, hepatitis) * **_D_**rugs * **_R_**heumatic fever * **_L_**upus and leprosy

Answer 18

* Flu-like syndrome after antibiotics are started * Due to killed bacteria releasing pyrogens.

Answer 19

* Zoonosis * Infectious disease transmitted between animals and humans. * Anaplasma spp. * _Disease_: Anaplasmosis * _Transmission & source_: Ixodes ticks (live on deer and mice) * Bartonella spp. * _Disease_: Cat scratch disease, bacillary angiomatosis * _Transmission & source_: Cat scratch * Borrelia burgdorferi * _Disease_: Lyme disease * _Transmission & source_: Ixodes ticks (live on deer and mice) * Borrelia recurrentis * _Disease_: Relapsing fever * _Transmission & source_: Louse (recurrent due to variable surface antigens) * Brucella spp. * _Disease_: Brucellosis/undulant fever * _Transmission & source_: Unpasteurized dairy * Campylobacter * _Disease_: Bloody diarrhea * _Transmission & source_: Puppies, livestock (fecal-oral, ingestion of undercooked meat) * Chlamydophila psittaci * _Disease_: Psittacosis * _Transmission & source_: Parrots, other birds * Coxiella burnetii * _Disease_: Q fever * _Transmission & source_: Aerosols of cattle/sheep amniotic fluid * Ehrlichia chaffeensis * _Disease_: Ehrlichiosis * _Transmission & source_: Lone Star ticks * Francisella tularensis * _Disease_: Tularemia * _Transmission & source_: Ticks, rabbits, deer fly * Leptospira spp. * _Disease_: Leptospirosis * _Transmission & source_: urine * Mycobacterium leprae * _Disease_: Leprosy * _Transmission & source_: Humans with lepromatous leprosy; armadillo (rare) * Pasteurella multocida * _Disease_: Cellulitis, osteomyelitis * _Transmission & source_: Animal bite, cats, dogs * Rickettsia prowazekii * _Disease_: Epidemic typhus * _Transmission & source_: Louse * Rickettsia rickettsii * _Disease_: Rocky Mountain spotted fever * _Transmission & source_: Dermacentor ticks * Rickettsia typhi * _Disease_: Endemic typhus * _Transmission & source_: Fleas * Yersinia pestis * _Disease_: Plague * _Transmission & source_: Fleas (rats and prairie dogs are reservoirs)

Answer 20

* Properties * A pleomorphic, gram-variable rod that is involved in **_vagin_**osis. * Presents as a gray vaginal discharge with a **_fishy_** smell * Nonpainful (vs. vaginitis). * Associations * Associated with sexual activity, but not sexually transmitted. * Characterized by... * Bacterial vaginosis is also characterized by overgrowth of certain anaerobic bacteria in vagina. * **_Clue_** cells, or vaginal epithelial cells covered with **_Gardn_**erella bacteria, are visible under the microscope (arrow) [A]. * Treatment * Metronidazole or (to treat anaerobic bacteria) clindamycin. * **I don’t have a _clue_ why I smell _fish_ in the _vagina_ _garden_!**

Answer 21

* Treatment for all * Doxycycline. * Rash common dieases * Rocky Mountain spotted fever * Typhus * Rash rare dieases * Ehrlichiosis * Anaplasmosis * Q fever

Answer 22

* Rocky Mountain spotted fever * Properties * Rickettsiae are obligate intracellular organisms that need CoA and NAD+ because they cannot synthesize ATP. * Transmission * Rickettsia rickettsii, vector is tick. * Found... * Despite its name, disease occurs primarily in the South Atlantic states, especially North Carolina. * Findings * Rash typically starts at wrists and ankles and then spreads to trunk, palms, and soles [A]. * Classic triad—headache, fever, rash (vasculitis). * **_Palms_ and _soles_ rash is seen in **_C_**oxsackievirus _A_ infection (hand, foot, and mouth disease), **_R_**ocky Mountain spotted fever, and 2° **_S_**yphilis** * **You drive _CARS_ using your _palms_ and _soles_** * Typhus * Transmission * Endemic (fleas)—R. typhi. * Epidemic (human body louse)—R. prowazekii. * Findings * Rash starts centrally and spreads out, sparing palms and soles. * ****_R_**ickettsii on the w**_R_**ists, **_T_**yphus on the **_T_**runk.**

Answer 23

* Ehrlichiosis * Ehrlichia; vector is tick. * Monocytes with morulae [B] (berry-like inclusions) in cytoplasm. * Anaplasmosis * Anaplasma, vector is tick. * Granulocytes with morulae in cytoplasm. * Q fever * Coxiella burnetii; no arthropod vector. * Tick feces and cattle placenta release spores that are inhaled as aerosols. * Presents as pneumonia. * **_Q_ fever is **_Q_**ueer** because it has no rash or vector and its causative organism can survive outside in its endospore form. * Not in the Rickettsia genus, but closely related.

Answer 24

* Properties * Chlamydiae cannot make their own ATP. * They are obligate intracellular organisms that cause mucosal infections. * **Chlamys = cloak (intracellular)** * ****The chlamydial cell wall is unusual in that it lacks muramic acid. * 2 forms * **_E_**lementary body (small, dense) * “**_E_**nfectious” and **_E_**nters cell via **_E_**ndocytosis * Transforms into reticulate body. * **_R_**eticulate body * **_R_**eplicates in cell by fission * **_R_**eorganizes into elementary bodies. * Chlamydia trachomatis * Causes reactive arthritis (Reiter syndrome), follicular conjunctivitis [A], nongonococcal urethritis, and PID. * C. pneumoniae and C. psittaci * Cause atypical pneumonia * Transmitted by aerosol. * Chlamydophila psittaci—notable for an avian reservoir. * Treatment * Azithromycin (favored because one-time treatment) or doxycycline. * Lab diagnosis * Cytoplasmic inclusions seen on Giemsa or fluorescent antibody–stained smear.

Answer 25

* Types A, B, and C * Chronic infection, cause blindness due to follicular conjunctivitis in Africa. * **_ABC_ = **_A_**frica/**_B_**lindness/**_C_**hronic infection.** * Types D–K * Urethritis/PID, ectopic pregnancy, neonatal pneumonia (staccato cough), neonatal conjunctivitis. * D–K = everything else. * Neonatal disease can be acquired during passage through infected birth canal. * Types L1, L2, and L3 * **Lymphogranuloma venereum**—small, painless ulcers on genitals --\> swollen, painful inguinal lymph nodes that ulcerate (“buboes”). * Treat with doxycycline.

Answer 26

* Properties * No cell wall. * Not seen on Gram stain. * Bacterial membrane contains sterols for stability. * Grown on Eaton agar. * High titer of cold agglutinins (IgM), which can agglutinate or lyse RBCs. * Causes... * Classic cause of atypical “walking” pneumonia (insidious onset, headache, nonproductive cough, patchy or diffuse interstitial infiltrate). * Mycoplasmal pneumonia is more common in patients \<30 years old. * Frequent outbreaks in military recruits and prisons. * X-ray looks worse than patient. * Treatment * Macrolide, doxycycline, or fluoroquinolone (penicillin ineffective since Mycoplasma have no cell wall).

Microbiology - Clinical Bacteriology Flashcards

(50 cards)