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Vet Derm Review > Syke's infectious diseases - bacterial > Flashcards

Syke's infectious diseases - bacterial Flashcards

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1
Q

What specie(s) of tick(s) transmit Ehrlichia canis?

A

Rhipicephalus sanguineus (primary); Ixodes ricinus, Haemaphysalis spp. ticks, and Dermacentor spp. ticks; experimental transmission has been accom- plished with Dermacentor variabilis ticks

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2
Q

What specie(s) of tick(s) transmit Ehrlichia ewingii?

A

Amblyomma americanum

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3
Q

What infectious organism(s) does Rhipicephalus sanguineus transmit?

A

Ehrlichia canis, Babesia canis, Rickettsia ricketsii

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4
Q

What infectious organism(s) does Amblyomma americanum transmit?

A

Ehrlichia ewingii, Ehrlichia chafeensis, Francisella tularensis, Rickettsia ricketsii

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5
Q

What cells does Ehrlichia infect?

A

leukocytes – Ehrlichia canis (monocytes), Ehrlichia ewingii (granulocytes), Ehrlichia chafeensis (monocytes)

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6
Q

What are the phases of canine monocytic ehrlichiosis (CME)?

A

acute (8-20 days after infection); subclinical (months to years); chronic

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7
Q

Where does Ehrlichia canis multiply/replicate?

A

multiplies by binary fission within vacuoles of mononucear phagocytes –> rupture of infected host cells leads to infection of new cells

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8
Q

Why might a dog infected with Ehrlichia have a negative immunofluorescent antibody (IFA) test?

A

antibodies can only be detected 7-28 days after initial infection – false-negative may occur if tested too soon

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9
Q

T/F: A positive serum antibody titer for Ehrlichia indicates infection.

A

False - may reflect previous exposure and not necessarily disease

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10
Q

What test is more sensitive than immunofluorescent antibody or ELISA testing for acute canine monocytic ehrlichiosis?

A

whole-blood PCR assys for E. canis DNA

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11
Q

Why are fluoroquinolones not recommended for treatment of canine monocytic ehrlichiosis?

A

Ehrlichia canis appears to have intrinsic gyrase-mediated resistance to fluoroquinolones

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12
Q

What cutaneous signs have been associated with canine monocytic ehrlichiosis?

A

petechial and ecchymotic hemorrhages (occur d/t thrombocytopenia and platelet dysfunction)

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13
Q

What ticks are known to transmit Rickettsia ricketsii?

A

Dermacentor variabilis (american dog tick), Dermacentor andersoni (Rocky mountain wood tick), Rhipicephalus sanguineus, Amblyomma americanum, Amblyomma cajennense, Amblyomma aureolatum

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14
Q

What organism causes Rocky Mountain spotted fever? Characteristics of the organism?

A

Rickettsia rickettsii, an obligately intracellular bacteria

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15
Q

What is the characteristic clinical sign of Rocky Mountain spotted fever?

A

disseminated vasculitis –> cutaneous macules, papules, petecchia

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16
Q

What cells does Rickettsia ricketsii infect?

A

primarily infects endothelial cells (smooth muscles and monocytes may also be infected)

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17
Q

T/F: Rocky Mountain spotted fever has three phases: acute, subclinical, and chronic.

A

False - Ehrlichia has three phases, RMSF causes an ACUTE disease

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18
Q

What tests are used to aid in diagnosis of Rocky Mountain spotted fever?

A

convalescent antibody titers (2-3 weeks apart), PCR testing (during acute phase), biopsy – shows vasculitis and organisms around vessels – with direct IFA or Gimenez stain

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19
Q

What antibiotics can worsen the course of Rocky Mountain spotted fever?

A

trimethoprim sulfonamides

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20
Q

T/F: Staphylococcus spp. are strictly aerobic bacteria.

A

False - facultative anaerobes

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21
Q

What is coagulase?

A

enzyme that cleaves fibrinogen into fibrin –> results in coagulation of plasma

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22
Q

What is the mecA gene?

A

located on a large genetic element (staphylococcal casette chromosome) –> encodes an altered penicillin binding protein (PBP2a)

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23
Q

what are the members of the S. intermedius group?

A

Staph. Intermedius, Staph. Pseudintermedius, Staph. Delphini

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24
Q

Scalded skin syndrome has been reported in people with what organism? Pathogenesis?

A

Staph. Aureus –> strains that produce an exfoliative toxin, which hydrolyzes the intercellular glycoprotein desmoglein-1

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25
Q

How does inducible clindamycin resistance occur?

A

bacterial methylation of the ribosomal binding site for clindamycin

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26
Q

How can you test for inducible clindamycin resistance?

A

D-zone test – culture organism in the presence of erythromycin and clindamycin disks; organisms near the erythromycin disk express enhanced resistance to clindamycin –> results in a D shape to the zone of inhibition around the clindamycin disk

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27
Q

Staph strains that possess the tetracycline efflux protein tetK may still be susceptible to what tetracycline antibiotic?

A

minocycyline

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28
Q

Staph strains that posses tetM are resistant to which tetracyclines?

A

All tetracyclines (including minocycline) – tetM protects the ribosome from tetracycline binding

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29
Q

What layer of the cell membrane is much thicker in gram-positive bacteria than gram-negative bacteria?

A

peptidoglycan layer

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30
Q

What additional cell membrane structures are present in gram-negative bacteria?

A

complex outer membrane that contains lipopolysaccharide as well as porins (regulate transport of molecules in and out of the cell)

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31
Q

What are the components of lipopolysaccharide?

A

lipid A backbone, core oligosaccharide, O antigen side chain

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32
Q

What component of the cell membrane of gram negative bacteria is called endotoxin?

A

lipid A component - phosphorylated disaccharide to which long, hydrophobic fatty acid chains are attached (anchors LPS into the outer membrane); Is the biologically active portion of the molecule –> stimulates a potent host inflammatory response

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33
Q

Examples of gram-negative cocci? Where are they found on the body?

A

Moraxella, Neisseria – commensals of the oral cavity of dogs and cats

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34
Q

Two categories of gram-negative rods?

A

Enterobacteriaceae (E. coli, Proteus, Salmonella, Enterobacter, Citrobacter, Serratia, Klebsiella) and non-Enterobacteriaceae (Pasteurellaceae, Pseudomonas aeruginosa, Acinetobacter)

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35
Q

Virulence factors of Enterobacteriaceae?

A

capsule (K antigen), flagella (H antigen)

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36
Q

Virulence factors of Pseudomonas aeruginosa?

A

exotoxins, type III secretion system, LPS, pili, flagella, proteases, phospholipases, iron-scavenging mechanisms such as pyoverdin production, biofilms (almost every type of virulence factor!!!)

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37
Q

Mechanisms of resistance of Pseudomonas aeruginosa?

A

production of beta-lactamase enzymes (can include ESBLs), antibiotic efflux pumps, enzymes that modify aminoglycosides or later antibiotic binding sites (such as DNA gyrase for fluoroquinolones), and decreased bacterial permeability

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38
Q

Characteristics of actinomyces? Normal site of inhabitance?

A

anaerobic or microaerophilic, filamentous, gram-positive bacteria; tan to yellow colonies; normal inhabitants of mucous membranes

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39
Q

Typical route of infection with actinomyces?

A

inoculation into tissues with other bacteria, often as a result of deeply penetrating wound or foreign body migration

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40
Q

Differential diagnoses for actinomycosis?

A

mycobacterial infections, streptomycosis, nocardiosis, bartonellosis, fungal infections, neoplasia

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41
Q

Clinical signs associated with actinomycosis?

A

subcutaneous masses and draining skin lesions (cervicofacial and cutaneous-subcutaneous disease); pulmonary nodules/masses/effusion; abdominal effusion/masses

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42
Q

Appearance of Actinomyces on cytology?

A

filamentous rods; gram-postive, non-acid fast filamentous organisms that are occasionally branched – filaments are less than 1 um wide, vary in legnth, and can stain irregularly –> produces a “beaded” appearance

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43
Q

Gross characteristics of Actinomycosis

A

sulfur granules may be visible – white to tan gray granules

44
Q

T/F: Actinomyces spp. are difficult to grow on routine aerobic cultures.

A

False - most that cause disease are facultative anaerobes that will grow under aerobic conditions BUT a few are obligate anaerobes (A. bovis, A. israelii, A. meyeri); visible growth can occur within 48 hours but usually requires 5-7 days

45
Q

T/F: It is common to isolate up to five other associated bacteria along with Actinomyces spp.

A

True - most are also resident flora of the oral cavity or intestinal tract

46
Q

Histopathologic findings with Actinomycosis?

A

abscesses with a core of neutrophils encapsulated by granulation tissue; sulfur granules are generally in the center of microabscesses – granules are round, oval or scalloped amphophilic solid masses; often rimmed by partially confluent radiating eosinophilic club-shaped structures (Splendore-Hoeppli phenomenon)

47
Q

The Splendore-Hoeppli phenomenon has been reported with what infections?

A

Actinomycosis, Zygomycosis, sporotrichosis, parasitic infections, foreign body reactions, hypereosinophilic syndrome

48
Q

T/F: Acintomyces stain positive with acid fast.

A

False - they are NOT acid fast; will stain with Gram stain (gram positive), Giemsa, and silver stains

49
Q

What is the drug of choice for actinomycosis?

A

penicillins

50
Q

Characteristics of nocardia (gram +/-? Rods/cocci?)? Normal sites of inhabitance?

A

filamentous, branching (branch at right angles), gram positive bacteria; ubiquitous soil saprophytes, found in water, dust, and on decaying plants and fecal matter

51
Q

What is the most common form of nocardiosis in cats?

A

cutaneous-subcutaneous nocardiosis - slow and progressive circumferential spread of a nonhealing, draining wound

52
Q

What is the most common form of nocardiosis in people?

A

pulmonary nocardiosis (does occur in dogs and less commonly in cats) - resembles deep mycoses

53
Q

T/F: Nocardia stain positive with acid-fast stain.

A

True - often partially or weakly acid-fast

54
Q

T/F: Mycobacterium spp., like Nocardia, will often branch.

A

False - only Nocardia branches

55
Q

T/F: Nocardiosis is often associated with mixed infections.

A

False - Actinomycosis is associated with mixed infections, Nocardiosis is usually the only pathogen

56
Q

T/F: Nocardia grow aerobically under normal conditions.

A

True - colonies are usually visible within 2 days but sometimes can take 2-4 weeks of incubation

57
Q

Histopathologic findings with Nocardiosis?

A

central region of necrosis and suppuration, surrounded by macrophages, lymphocytes, and plasma cells; Nocardia filaments are usually present in abundance within regions of necrosis and suppuration

58
Q

T/F: Nocardia spp. are readily identified on biopsy specimens with H&E.

A

False - need Gram stain or methenamine silver, partially acid fast

59
Q

What are the first line antimicrobials for treatment of Nocardiosis?

A

sulfonamides, including trimethoprim-sulfonamides

60
Q

T/F: Wide surgical exicision is necessary for cure of both Actinomycosis and Nocardiosis.

A

False - not usually needed for Actinomycosis unless present for long periods of time with granulation tissue/fibrosis; usually needed for Nocardiosis

61
Q

Characteristics of mycobacterium spp. (gram +/-? Rods/cocci?)?

A

aerobic, nonmotile, non-spore-forming, GRAM POSITIVE, ACID-FAST pleomorphic bacilli

62
Q

What stains are useful to find Mycobacterium?

A

Ziehl-Neelson or Kinyoun stains (acid-fast stains)

63
Q

What species is the reservoir host for Mycobacterium tuberculosis?

A

humans, cats are RESISTANT to infection with M. tuberculosis

64
Q

What species is the reservoir host for Mycobacterium microti?

A

rodents (especially voles & shrews)

65
Q

What species is the reservoir host for Mycobacterium bovis?

A

cattle and other wildlife species

66
Q

What bacteria from the Mycobacterium tubeculosis complex infect dogs and cats?

A

Mycobacteria tuberculosis - dogs ONLY; Mycobacteria bovis & Mycobacteria microti - cats & rarely dogs

67
Q

What species of Mycobacterium are SLOWLY growing?

A

Mycobacterium tuberculosis complex (M. tuberculosis, M. bovis, M. microti); M. avium-intracellulare complex (M. avium subsp. Avium, M. avium subsp hominissuis); Slowly growing nontuberculosis mycobacteria (M. kansaii, M. ulcerans, M. genavense, M. malmoense, M. celatum, M. terrae, M. simiae, M. visibile)

68
Q

What species of Mycobacterium are RAPIDLY growing?

A

M. fortuitum, M. smegmatis, M. abscessus, M. chelonae, M. thermoresistibile, M. goodii, M. flavescens, M. alvei

69
Q

What species of Mycobacterium are unable to be cultured?

A

Mycobacterium lepraemurium, the Canine Leproid Granuloma organism

70
Q

Mycobacterium tuberculosis complex organisms can replicate inside of what cells inside of the host?

A

can replicate locally at site of inoculation (lungs, skin, GI tract) but are then ingested by macrophages and replicate within the cells –> macrophage destruction leads to recruitment of lymphocytes and additional monocytes –> tubercle formation

71
Q

Cats infected with M. bovis or M. microti have what clinical signs?

A

cutaneous nodular lesions +/- mandibular lymphadenopathy

72
Q

What findings on cytology are suggstive of mycobacterial tuberculosis complex infection?

A

mixed population of heavily vacuolated histiocytes, smaller numbers of neutrophils and small lymphocytes; intracytoplasmic, nonstaining bacilli inside of macrophages***; cholesterol crystals, caseous debris, concentrically laminated crystalline structures (calcospherite bodies)

73
Q

T/F: Routine aerobic, anaerobic, fungal, and mycoplasma cultures are negative from animals with mycobacterium tuberculosis complex infections.

A

True - require special medium to grow (7H11 agar or Lowenstein-Jensen media)

74
Q

Histopathologic findings with mycobacterium tuberculosis complex infections?

A

tubercles/granulomas composed of abundant epithelioid macrophages and lesser number of neutrophils; acid-fast stains reveal low numbers of acid-fast bacteria in the tubercle centers

75
Q

T/F: Both mycobacterium tuberculosis complex and mycobacterium avium complex bacteria have reservoir hosts.

A

False - only mycobacterium tuberculosis complex organisms have reservoir hosts – MAC bacteria are environmental saprophytes

76
Q

T/F: Pulmonary lesions are not common with Mycobacterium avium complex infections in dogs.

A

True - different from mycobacterium tuberculosis complex infections

77
Q

Infection with mycobacterium avium complex bacteria usually occurs under what conditions?

A

immunosuppression/immunocompromised animals

78
Q

Feline leprosy is caused by what organism?

A

Mycobacterium lepraemurium

79
Q

T/F: The causative organism of canine leproid granuloma syndrome has never been isolated in culture.

A

True - has only be partially characterized by PCR sequencing

80
Q

T/F: Cats with feline leprosy are usually systemically ill.

A

False - usually only have cutaneous/subcutaneous nodules

81
Q

What is the environmental reservoir of non-tuberculosis bacteria other than mycobacterium-avium

A

soil and water sources

82
Q

What type of mycobacterial infection has a predilection for infecting adipose tissue

A

rapidly growing mycobacteria - M. fortuitum and M. smegmatis –> develop mycobacterial panniculitis

83
Q

T/F: Infection with rapidly growing mycobacteria such as Mycobacterium fortuitum or Mycobacterium smegmatis is usually secondary to immunosuppression.

A

False - usually are inoculated by means of cat fight injuries (bites/scratches) or other penetrating wounds

84
Q

T/F: Disseminated infections with rapidly growing mycobacteria such as M. fortuitum or M. smegmatis are rare.

A

TRUE

85
Q

T/F: Disease caused by the non-tuberculoid slowly growing mycobacteria resemble disease caused by mycobacterium avium complex.

A

True - can cause ulcerative skin lesions or disseminated disease

86
Q

In cats, mycobacterial panniculitis is most likely to occur where on the body?

A

inguinal fat pad – subcutis becomes thickened and adheres to the dermis —> nodular and draining skin lesions develop

87
Q

T/F: Cats with mycobacterial panniculitis are usually systemically ill.

A

False - usually are otherwise well

88
Q

Histopathologic findings with mycobacterial panniculitis?

A

pyogranulomatous inflammation without tubercle formation or necrosis; large lipid vacuoles that contain acid-fast bacilli may be present

89
Q

T/F: Rapidly growing mycobacteria (M. fortuitum and M. smegmatis) grow readily on routine culture media.

A

TRUE

90
Q

What treatment options are recommended for mycobacterium avium complex or slowly growing mycobacterial infections?

A

combinations of clarithromycin, rifamycin, and a fluoroquinolone

91
Q

What are treatment options for rapidly growing mycobacterial infections?

A

doxycycline, fluoroquinolones, clarithromycin, aminoglycosides, sulfonamides, carbapenems

92
Q

Differential diagnoses for mycobacterial infection in the cat?

A

neoplasia (lymphoma), feline infectious peritonitis, tularemia, nocardiosis, actinomycosis, rhodococcosis, bartonellosis, leishmaniasis, fungal infections (crypto, blasto, etc.)

93
Q

Most common species of Bartonella in cats?

A

Bartonella henselae, Bartonella clarridgeiae

94
Q

Most common species of Bartonella in dogs?

A

Bartonella vinsonii subsp berkhoffii, Bartonella henselae

95
Q

Mode of transmission of Bartonella?

A

fleas (Ctenocephalides felis), other species of fleas (Pulex spp.) and vectors such as ticks, lice, biting flies

96
Q

Most frequent manifestation of bartonellosis in dogs

A

endocarditis – clinical signs include lethargy, fever, cardiac murmur, cough, tachypnea, lameness, neurologic signs

97
Q

Characteristics of bartonella spp?

A

Fastidious, intraerythrocytic GRAM-NEGATIVE bacteria

98
Q

What species is the reservoir host for Bartonella henselae?

A

cats

99
Q

What species is the reservoir host for Bartonella vinsonii subsp berkhoffi?

A

domestic and wild dogs

100
Q

After infection, where does Bartonella replicate?

A

in erythrocytes; can also infect endothelial cells and bone marrow progenitor cells

101
Q

T/F: Most dogs and cats infected with Bartonella show no clinical signs of illness when bacteremic.

A

TRUE- cats infected with B. henselae develop a small papule at the site of inoculation, transient fever and lymphadenopathy (may show no clinical signs)

102
Q

Histopathologic findings with Bartonella infections? In what tissue?

A

Chronic inflammation with fibrous tissue and extensive mineral deposits in the HEART; small bacilli may be seen within lesions with silver stains or IHC for B. henselae)

103
Q

Why might a blood culture be negative in an animal infected with Bartonella?

A

due to relapsing bacteremia (and may have a low level of bacteremia)

104
Q

Antibiotics recommended for treatment of Bartonellosis?

A

doxycycline; amoxicillin-clavulanic acid

105
Q

DDX?

A

Actinomyces, Nocardia spp., Corynebacterium spp., Mycobacterium spp.

106
Q

Describe changes present and give top ddx

A

Severe, necrotizing pyogranulomatous inflammation with intralesional, filamentous, branching, gram-positive bacteria;

Top DDX is Nocardiosis (less likely Actinomycosis)

Vet Derm Review (44 decks)

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