Section 1: Aerobic Gram Negative Coccobacili Flashcards Preview

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Flashcards in Section 1: Aerobic Gram Negative Coccobacili Deck (42)
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What are the characteristics of Haemophilus sp.

Normal flora of the upper respiratory tract


What are the growth requirements of Haemophilus

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


What are the two groups Haemophilus influenzae is split into

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


What is the epidemiology of Haemophilus influenzae

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


What is the pathogenesis of Haemophilus influenzae



What is meningitis

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


What is epiglottitis

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


What is Pneumonia

Seen in adult debilitated, imrnunocompromised patients


How is Haemophilus influenzae diagnosed

Culture on chocolate blood agar
Agglutination testing
Culture on blood agar with Staphylococcus aureus


How is Haemophilus influenzae prevented

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


What is Haemophilus ducreyi

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


How is Haemophilus ducreyi diagnosed

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


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

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


What is the characteristic of the Haemophilus ducreyi ulcer

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


What is Haemophilus vaginalis

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


How is Haemophilus vaginalis diagnosed

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


What is Bordetella pertussis

-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)


What are the virulence factors of Bordetella pertussis

Pertussis Toxin
Filamentous Hemagglutinin
extracellular adenylate cyclase
Strain reversion


What does the buildup of cAMP from Bordetella pertussis lead to

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


What is Filamentous Hemagglutinin

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


What is extracellular adenylate cyclase (TOXIN)

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


What is Strain reversion

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


What is the epidemiology of Bordetella pertussis

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


What are the pathological stages of Bordetella pertussis

Catarrhal stage
Paroxysmal stage


What occurs during the Catarrhal stage of Bordetella pertussis infection

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


What occurs during the Paroxysmal stage of Bordetella pertussis infection

-Follows relatively nonspecific symptoms of catarrhal stage
• Begins gradually with prolonged and paroxysmal coughing that ends in a characteristic inspiratory gasp


How is Bordetella pertussis diagnosed

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


How is Bordetella pertussis prevented

Whole cell vaccine
Acellular vaccin -fewer side effects


How are Brucella species named

for the animal they infect


What is the epidemiology of Brucella

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