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Clinical Microbiology > Section 1: Aerobic Gram Negative Coccobacili > Flashcards

Section 1: Aerobic Gram Negative Coccobacili Flashcards

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Biology 101 flashcards
1
Q

What are the characteristics of Haemophilus sp.

A

Small

Normal flora of the upper respiratory tract

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2
Q

What are the growth requirements of Haemophilus

A

Heme, a building block of hemoglobin
X factor-component ofblood called hemin
V factor-either NAD or NADP
In lab Haemophilus is grown on chocolate blood agar

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3
Q

What are the two groups Haemophilus influenzae is split into

A

1: Encapsulated or typeable strains
2: Non encapsulated or nontypeable strains

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4
Q

What is the epidemiology of Haemophilus influenzae

A

Transmitted in respiratory secretions.
Usually non encapsulated strains are part of the normal flora
• However, a minority (3-7%) of healthy individuals harbor Hib in the upper respiratory tract

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5
Q

What is the pathogenesis of Haemophilus influenzae

A

Meningitis
Epiglottitis
Pneumonia

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6
Q

What is meningitis

A

Leading cause of acute meningitis in children (until widespread vaccination program began in 1985)
• Regional lymph nodes and meninges are infected • Bloodstream can be infected = bacteremia
• Serious neurologic sequelae (abnormal condition following or related to a previous disease) frequently develop and persist after recovery from meningitis

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7
Q

What is epiglottitis

A

Infection of the epiglottis characterized by swelling
• Pediatric illness which can be life-threatening emergency
• Symptoms include, rapid progression, high fever, drooling, inspiratory strider, and difficulty breathing when supine
• Since the advent of the Hib vaccine the disease is seldom seen

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8
Q

What is Pneumonia

A

Seen in adult debilitated, imrnunocompromised patients

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9
Q

How is Haemophilus influenzae diagnosed

A 
Microscopy
Serotyping
Culture on chocolate blood agar 
Agglutination testing 
Culture on blood agar with Staphylococcus aureus
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10
Q

How is Haemophilus influenzae prevented

A

Until 6 mos. of age infant is protected by maternal antibodies
In 1985 first Hib conjugate vaccines licensed for use
• All children should have vaccine approved for infants at 2 mos o Children older than 60 mos. and adults do not need to be vaccinated

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11
Q

What is Haemophilus ducreyi

A

Causative agent of the sexually transmitted infection (STI), chancroid
-After an incubation period of one day to two weeks, begins with a small bump on the genitalia that becomes an ulcer within a day of its appearance

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12
Q

How is Haemophilus ducreyi diagnosed

A

Obtain smear from genital ulcers and culture on chocolate blood agar
Rule out other STis

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13
Q

What is often seen in the inguinal regions of patients with Haemophilus ducreyi

A

Patients often have adenopathy (swollen lymph nodes) in the inguinal area

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14
Q

What is the characteristic of the Haemophilus ducreyi ulcer

A

The ulcer characteristically:
• is painful
• has irregular or ragged borders
• is soft and has a base that is covered with a yellowish-grey material
Men typically have 1 ulcer, while females have multiple ulcers

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15
Q

What is Haemophilus vaginalis

A

aka Gardnerella vaginalis
• Part of normal vaginal flora
• Sometimes causes mild infection

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16
Q

How is Haemophilus vaginalis diagnosed

A

Gram stain reveals “clue cells”
• Identified as numerous stippled or granulated epithelial cells
• Characteristic of H. vaginalis infection

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17
Q

What is Bordetella pertussis

A

Capsule

  • Three serotype based on capsular antigens have been identified
  • Nutritionally fastidious, cultivated on rich media supplemented with blood
  • Do not require X and V factors
  • Causative agent of pertussis (whooping cough)
18
Q

What are the virulence factors of Bordetella pertussis

A 
Pertussis Toxin 
Filamentous Hemagglutinin
extracellular adenylate cyclase 
endotoxin
Strain reversion
19
Q

What does the buildup of cAMP from Bordetella pertussis lead to

A

Increased insulin production, resulting in hypoglycemia
• Increased sensitivity to histamine, resulting in increased capillary permeability, hypotension, and shock
• Inhibition of monocytes migrating into tissue

20
Q

What is Filamentous Hemagglutinin

A

Large protein that forms filamentous structures on the cell surface that bind to the ciliated host cells allowing colonization of host tissue

21
Q

What is extracellular adenylate cyclase (TOXIN)

A

B. Pertussis secretes invasive adenylate cyclase which enters host cell and acts locally to reduce phagocytic activity, particularly of neutrophils

22
Q

What is Strain reversion

A

Transposon mutagenesis can result in a virulent strain (phase I) becoming non-virulent (phase IV)
• Phase N strain can revert (lose the transposon) and become virulent

23
Q

What is the epidemiology of Bordetella pertussis

A

Found worldwide
-Primarily infects children under 6 mos.
• Droplet transmission
• Incubation period is 7-10 days
-Pertussis once the most common disease of childhood
-Often fatal, particularly in infants

24
Q

What are the pathological stages of Bordetella pertussis

A

Catarrhal stage

Paroxysmal stage

25
Q

What occurs during the Catarrhal stage of Bordetella pertussis infection

A

Colonization of the upper respiratory system
• Characterized by fever, malaise and coughing
• B. pertussis is recovered in large numbers from pharyngeal cultures
• If diagnosed in this stage the severity and duration of the disease can be reduced by antimicrobial treatment

26
Q

What occurs during the Paroxysmal stage of Bordetella pertussis infection

A

-Follows relatively nonspecific symptoms of catarrhal stage

• Begins gradually with prolonged and paroxysmal coughing that ends in a characteristic inspiratory gasp

27
Q

How is Bordetella pertussis diagnosed

A

Swab nostrils
• Culture on selective media (Bordet-Gengou)
• Serum agglutination
• Fluorescent antibody testing

28
Q

How is Bordetella pertussis prevented

A

Whole cell vaccine

Acellular vaccin -fewer side effects

29
Q

How are Brucella species named

A

for the animal they infect

30
Q

What is the epidemiology of Brucella

A

Human brucellosis is a true zoonosis in that all infections are acquired from animals.

  • Brucella penetrates the skin and mucosa o In animals the microbe typically affects the reproductive organs and is contracted by humans via contaminated milk
  • Brucellosis is rare in the United States, 100 to 200 cases occur each year.
  • Brucellosis can be very common in countries where animal disease control programs have not reduced the amount of disease among animals
31
Q

What is the pathogenesis of Brucella

A
  • Microbes spread via lymphatic system and multiply in phagocytes (obligate intracellular)
  • Cause lesions in various organs including: liver, spleen, bone marrow, kidney
32
Q

What are the symptoms of Brucella

A

fever, unusually severe limb and back pain, marked fatigue

33
Q

How is Brucella diagnosed

A

Primarily Dependent on cllinical findings

-Grows poorly in culture and may need to be incubated for up to 4 weeks

34
Q

How is Brucella controlled

A

Immunize cattle sheep and goats.

  • Live attenuated vaccines have reduced brucellosis in domestic animals
  • Pasteurization of milk
  • Protective clothing for those occupationally exposed
35
Q

What are the characteristics of Francisella tularensis

A
  • small
  • Gram negative
  • Pleomorphic= rod, coccobacilli, filament-like
  • Non-motile
  • Very thin capsule composed of lipids
  • Pathogenic strains possess capsule, loss of or lack of capsule is associated with decreased virulence
  • Causative agent of tularemia (aka-glandular fever, rabbit fever, tick fever, and deer fly fever) •
36
Q

What are the 2 strains of Francisella tu/arensis

A

Type A strain= Francisella tularensis var tularensis causes tick-borne tularemia in rabbits, and produces classic disease in human beings
-Type B strain = found predominantly in Europe and Asia, rarely leads to fatal disease

37
Q

What is the epidemiology of Francisella tu/arensis

A

-Disease of mammals, fish, birds, and invertebrates
-Primary vector is infected ticks, sometimes deer flies
-Humans are infected by
• Direct contact with animal (hunters)
• Bite from infected tick or fly
• Contaminated food or water

38
Q

What is the pathology of Francisella tu/arensis

A
  • Initial symptoms oftularemia develop after 3-5 day incubation period
  • Fever, chills, malaise, fatigue
39
Q

How many microbes can cause Francisella tu/arensis

A

Highly infectious, as few as 10-50 microbes can cause disease

40
Q

What are the subtypes of Tularemia

A

Ulceroglandular tularemia
Pneumonic tularemia
Oculoglandular tularemia
Typhoidal tularemia

41
Q

How is Francisella tu/arensis diagnosed

A
  • Clinical history
  • Isolation in culture-must be grown on chocolate agar (sometimes blood agar). Requires incubation times of 1-2 weeks
  • Agglutination tests
  • Fluorescent antibody test
42
Q

How is Francisella tu/arensis prevented

A

-Avoid reservoirs and vectors of infection (rabbits, ticks, flies)
-Wear gloves when processing animals
-Prompt removal of ticks-F. tularensis present in feces, not saliva. Tick must feed for prolonged period to transmit infection -
Live attenuated vaccine is available
• Treatment
• Not completely effective in preventing disease, but can lessen severity of the disease
• Recommended for people at a significantly increased risk of exposure

Clinical Microbiology (6 decks)

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