Micro - Bacteriology (Part 2)

Question 1

A patient presents with septic shock and has the blood cultures shown here. What organism is this? What other organs should you worry about?

Answer 1

Staphylococcus aureus; bone and heart; S. aureus causes osteomyelitis and acute bacterial endocarditis

Question 2

A patient is found to have this histologic finding on biopsy of an upper lobe lesion. What is the most likely medical history?

Answer 2

An adult reinfected with tuberculosis

Question 3

All mycobacteria have what staining property seen in this image?

Answer 3

They are all acid-fast

Question 4

What bacteria causes syphilis?

Answer 4

Treponema pallidum

Question 5

Treponema pertenue causes what condition?

Answer 5

Yaws

Question 6

What tropical infection is not a sexually transmitted disease but results in a positive venereal disease research laboratory test?

Answer 6

Yaws

Question 7

What are the symptoms commonly associated with yaws?

Answer 7

Joint deformities following keloid healing of skin, bone and joint infection

Question 8

First-degree syphilis presents with what type of lesion?

Answer 8

A painless chancre at the site of infection (localized disease)

Question 9

Is second-degree syphilis a localized or disseminated disease?

Answer 9

Disseminated (remember: Secondary syphilis = Systemic)

Question 10

Second-degree syphilis presents with what type of skin manifestations?

Answer 10

A maculopapular rash on palms and soles and condylomata lata

Question 11

Third-degree syphilis presents with what signs and symptoms?

Answer 11

Gummas, aortitis, tabes dorsalis, and Argyll Robertson pupil

Question 12

Which stage of syphilis is characterized by broad-based ataxia, a positive Romberg sign, Charcot joints, and stroke-like symptoms?

Answer 12

Third-degree syphilis

Question 13

Third-degree syphilis can present with what neurologic defects?

Answer 13

Tabes dorsalis (resulting in broad-based gait, ataxia, and positive Romberg test) and Argyll Robertson pupil

Question 14

What signs and symptoms are associated with congenital syphilis?

Answer 14

Saber shins, saddle-nose deformity, neurological (cranial nerve VIII) deafness, Hutchinsons teeth, and mulberry molars

Question 15

What is the treatment of choice for syphilis?

Answer 15

Penicillin G

Question 16

Where can treponemes be found during primary and secondary syphilis?

Answer 16

In chancres during primary syphilis and in condylomata lata during secondary syphilis

Question 17

What causes aortitis in tertiary syphilis?

Answer 17

Destruction of the vasa vasorum

Question 18

Argyll Robertson pupil is associated with what disease?

Answer 18

Tertiary syphilis

Question 19

Describe the findings in a patient with an Argyll Robertson pupil.

Answer 19

The pupils constrict during accommodation but not in response to direct light.

Question 20

Which diagnostic test is most specific for treponemes, turns positive earliest during the course of disease, and remains positive for the longest time?

Answer 20

Fluorescent treponemal antibody absorption test (remember: FTA-ABS = Find The Antibody-ABSolutely)

Question 21

A positive venereal disease research laboratory test and a positive fluorescent treponemal antibody absorption test indicate what?

Answer 21

Active infection with a treponeme that causes syphilis

Question 22

If a venereal disease research laboratory test is positive but the fluorescent treponemal antibody absorption test is negative, what is the interpretation?

Answer 22

False-positive result for syphilis infection

Question 23

What do negative venereal disease research laboratory test and positive fluorescent treponemal antibody absorption test results indicate?

Answer 23

Successful treatment of syphilis

Question 24

Which conditions give biologic false-positive results for the venereal disease research laboratory test?

Answer 24

Viral infection, drugs, rheumatic fever, rheumatoid arthritis, systemic lupus erythematosus, and leprosy. (remember: VDRL = Viruses, Drugs, Rheumatic fever and arthritis, Lupus and leprosy)

Question 25

A positive venereal disease research laboratory indicates that antibodies have formed against what molecule?

Answer 25

Beef cardiolipin

Question 26

Name six medically important zoonotic bacteria.

Answer 26

**B**artonella henselae, **B**orrelia burgdorferi, **B**rucella spp, **F**rancisella tularensis, **Y**ersinia pestis, and **P**asteurella multocida, **E**lla (remember: **B**ig **B**ad **B**ugs **F**rom **Y**our **P**et named **E**lla)

Question 27

What organism transmitted by dairy products and contact with animals causes undulant fever?

Answer 27

*Brucella* spp (remember: **U**npasteurized dairy products give you *Undulant fever)*

Question 28

A dairy farmer presents with one week of fever that waxes and wanes without treatment. What is the diagnosis?

Answer 28

*Brucella* spp, which are found in dairy products or transmitted via contact with cows, sheep, and goats

Question 29

How is *Francisella tularensis* transmitted?

Answer 29

Tick bites

Question 30

What organism causes tularemia?

Answer 30

*Francisella tularensis*

Question 31

Name two animal reservoirs for ticks that transmit *Francisella tularensis*.

Answer 31

Rabbits and deer

Question 32

Which organism causes the plague?

Answer 32

*Yersinia pestis*

Question 33

What is the mode of transmission of the bubonic plague?

Answer 33

Flea bites

Question 34

What is the animal reservoir for ticks transmitting *Yersinia pestis*?

Answer 34

Rodents (especially prairie dogs)

Question 35

How is *Pasteurella multocida* transmitted?

Answer 35

Animal bite (cats, dogs)

Question 36

What infection is caused by *Pasteurella multocida*?

Answer 36

Cellulitis after cat and dog bites

Question 37

What is the disease caused by *Bartonella*?

Answer 37

Cat scratch fever

Question 38

What dermatologic finding can *Bartonella* cause in immunocompromised individuals?

Answer 38

Bacillary angiomatosis (can be mistaken for Kaposi sarcoma)

Question 39

What is the most common mode of transmission for the bacteria *Bartonella henselae*?

Answer 39

Cat scratch

Question 40

What kind of discharge is produced in vaginosis caused by *Gardnerella vaginalis*?

Answer 40

Off-white/gray vaginal discharge, fishy odor

Question 41

What is the treatment of choice for vaginosis caused by *Gardnerella vaginalis*?

Answer 41

Metronidazole

Question 42

What kind of cells (seen on a wet mount of vaginal discharge) are diagnostic of infection with *Gardnerella vaginalis*?

Answer 42

Clue cells (vaginal epithelial cells covered with bacteria)

Question 43

What are clue cells?

Answer 43

Vaginal epithelial cells covered with bacteria to the point where intracellular organelles are obscured

Question 44

Is *Gardnerella vaginalis* considered a sexually transmitted disease?

Answer 44

No, it is not a sexually transmitted disease, although it is more common in sexually active women

Question 45

What anaerobic bacteria other than *Gardnerella vaginalis* is frequently involved in vaginosis?

Answer 45

*Mobiluncus*

Question 46

A women presents with fishy gray vaginal discharge. What is the likely diagnosis and what will you prescribe?

Answer 46

Bacterial vaginosis caused by *Gardnerella*; treatment with metronidizole

Question 47

True or False? Rickettsiae are facultative intracellular parasites.

Answer 47

False; Rickettsiae are obligate intracellular parasites

Question 48

Rickettsiae are obligate intracellular parasites because they require which two cofactors?

Answer 48

Coenzyme A and nicotinamide adenine dinucleotide

Question 49

Rickettsiae are obligate intracellular parasites that are transmitted by what type of vector?

Answer 49

Arthropods (except *Coxiella*, which is transmitted by aerosol)

Question 50

Why is *Coxiella* considered an atypical rickettsia?

Answer 50

Because it causes pneumonia, instead of the classic triad of fever, headache, and rash, and it is the only one not carried by an arthropod vector

Question 51

What is the classic triad of symptoms caused by a rickettsial infection?

Answer 51

Fever, headache, and rash (vasculitis)

Question 52

What disease does *Rickettsia rickettsii* cause?

Answer 52

Rocky Mountain spotted fever

Question 53

The pathogen that causes Rocky Mountain spotted fever is carried by what vector?

Answer 53

Ticks

Question 54

Endemic typhus is caused by what bacterium?

Answer 54

*Rickettsia typhi*

Question 55

The pathogen that causes endemic typhus is carried by what vector?

Answer 55

Fleas

Question 56

Epidemic typhus is caused by what bacterium?

Answer 56

*Rickettsia prowazekii*

Question 57

The pathogen that causes epidemic typhus is carried by what vector?

Answer 57

Human body lice

Question 58

Q fever is caused by what bacterium?

Answer 58

*Coxiella burnetii*

Question 59

The pathogen that causes Q fever is carried by what vector?

Answer 59

*Coxiella burnetii* is an atypical *Rickettsia* in that it has no vector and is transmitted via aerosol

Question 60

What is the treatment of choice for all Rickettsial infections?

Answer 60

Tetracycline

Question 61

How could one distinguish between the rash of Rocky Mountain spotted fever and that of typhus?

Answer 61

Rocky Mountain spotted fever starts in the periphery and moves inward whereas typhus starts in the trunk and moves outward (remember: **R**ickettsia on the w**R**ists, **T**yphus on the **T**runk)

Question 62

Which rickettsial disease does not present with a rash?

Answer 62

Q fever is the only rickettsial infection that does not cause a rash

Question 63

Does Q fever have a positive or negative Weil-Felix reaction assay?

Answer 63

Negative; a Weil-Felix assay is usually positive for typhus and Rocky Mountain spotted fever but negative for Q fever

Question 64

True or False? *Coxiella burnetii* can survive outside of the body for a long time.

Answer 64

True; *Coxiella burnetii* is the only rickettsial pathogen that can survive outside the body for long periods of time

Question 65

*Ehrlichia* is carried by what type of vector?

Answer 65

Tick

Question 66

A child who was recently camping in Virginia presents with a rash moving up the arms and legs, headache, fever, and a very ill appearance. What is your diagnosis and how will you treat?

Answer 66

Rocky Mountain spotted fever; treatment with tetracycline

Question 67

Rocky Mountain spotted fever is endemic to what area?

Answer 67

The East Coast; despite its name it is not seen in the Rocky Mountains

Question 68

What three diseases start with a rash on the palms and soles?

Answer 68

**C**oxsackievirus **A** (hand-foot-and-mouth disease), **R**ocky Mountain spotted fever, and **S**yphilis (remember: you drive **CARS** with your **palms** and **soles**)

Question 69

The Weil-Felix reaction is used to test for what pathogens?

Answer 69

Rickettsiae (this reaction is an assay for antibodies)

Question 70

In a Weil-Felix reaction, antirickettsial antibodies in patient serum cross-react and agglutinate when mixed with antigens from what pathogen?

Answer 70

*Proteus*

Question 71

Which rickettsial infection will have a negative Weil-Felix reaction?

Answer 71

*Coxiella burnetii* (which causes Q fever)

Question 72

What are the two forms of Chlamydiae?

Answer 72

The elementary body and the reticulate body

Question 73

During their life cycle, what form of chlamydia is infectious (ie, enters host cells)?

Answer 73

The **E**lementary body (small, dense) **E**nters the body via **E**ndocytosis

Question 74

During their life cycle, what form of chlamydia replicates by fission?

Answer 74

The **R**eticulate (initial) body **R**eplicates in the cell by fission

Question 75

What diseases are caused by *Chlamydia trachomatis*?

Answer 75

Reactive arthritis, conjunctivitis, nongonococcal urethritis, cervicitis, and pelvic inflammatory disease

Question 76

Which two chlamydial species cause atypical pneumonia and how are they transmitted?

Answer 76

*Chlamydia pneumoniae* and *Chlamydia psittaci*; both are transmitted by aerosol

Question 77

*Chlamydia psittaci* has what animal reservoir?

Answer 77

Birds

Question 78

What are the treatments of choice for chlamydial infections?

Answer 78

Erythromycin or tetracycline

Question 79

How can chlamydial infection be diagnosed by microscopy?

Answer 79

By cytoplasmic inclusions seen on Giemsa or fluorescent antibody staining

Question 80

The chlamydial cell wall is unique in that is lacks _____ \_\_\_\_\_.

Answer 80

Muramic acid

Question 81

Why are *Chlamydia* intracellular organisms?

Answer 81

Because they cannot make their own adenosine triphosphate

Question 82

Which *Chlamydia trachomatis* serotypes cause chronic infection and blindness in Africa?

Answer 82

Types **A, B**, and **C** (remember: **A**frica, **B**lindness, **C**hronic infection)

Question 83

Which *Chlamydia trachomatis* serotypes cause urethritis, pelvic inflammatory disease, ectopic pregnancy, neonatal pneumonia, and neonatal conjunctivitis?

Answer 83

Types D through K

Question 84

Which *Chlamydia trachomatis* serotypes cause lymphogranuloma venereum?

Answer 84

Types **L**1, **L**2, and **L**3 (remember: **L**ymphogranuloma)

Question 85

What is the treatment of choice for neonatal disease caused by *Chlamydia trachomatis*?

Answer 85

Oral erythromycin

Question 86

What test is positive in lymphogranuloma venereum?

Answer 86

Frei test

Question 87

When is neonatal *Chlamydia* acquired?

Answer 87

As the infant passes through an infected birth canal

Question 88

What are the symptoms of lymphogranuloma venereum?

Answer 88

Acute lymphadenitis

Question 89

What other infection has similar symptoms to lymphogranuloma venereum?

Answer 89

Granuloma inguinale (donovanosis) caused by *Calymmatobacterium granulomatis*

Question 90

What bacteria is most commonly implicated in "walking pneumonia"?

Answer 90

*Mycoplasma pneumoniae*

Question 91

What are the classic symptoms of the pneumonia that is caused by *Mycoplasma pneumoniae*?

Answer 91

Insidious onset, headache, nonproductive cough, and diffuse interstitial infiltrates seen on chest x-ray

Question 92

What is a classic characteristic of chest x-ray findings in pneumonia caused by *Mycoplasma*?

Answer 92

The x-ray shows bilateral interstitial infiltrates, making the patient appear much sicker than he/she is

Question 93

*Mycoplasma pneumoniae* infection is associated with a high titre of what antibodies?

Answer 93

Cold agglutinins (immunoglobulin M)

Question 94

*Mycoplasma pneumoniae* can be grown on what medium?

Answer 94

Eatons agar

Question 95

What is the best treatment for *Mycoplasma pneumoniae* infection?

Answer 95

Tetracycline or erythromycin

Question 96

Why is *Mycoplasma pneumoniae* resistant to all penicillins?

Answer 96

Because it has no cell wall

Question 97

*Mycoplasma* cell membranes are distinct because they contain \_\_\_\_\_.

Answer 97

Cholesterol

Question 98

What age group is most commonly affected by *Mycoplasma pneumoniae* infection?

Answer 98

Individuals younger than 30 years of age

Question 99

A military recruit presents with a slow-onset, nonproductive cough with headache. Chest x-ray shows diffuse interstitial infiltrates, although the patient feels well. What is the likely diagnosis and how would you treat?

Answer 99

*Mycoplasma pneumoniae*; treatment with tetracycline or erythromycin

Question 100

Why are *Mycoplasma pneumoniae* not seen on gram stain?

Answer 100

No cell walls

Question 101

The tick *Ixodes*, which carries *Borrelia burgdorferi*, is also the vector for what other pathogen?

Answer 101

*Babesia*

Question 102

A child in Connecticut presents with Bells palsy. What infectious disease must be considered as a diagnosis?

Answer 102

Lyme disease

Question 103

Treponemes belong to what group of bacteria?

Answer 103

Spirochetes