Bacterial Infections: Haemophilus Overview

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Questions and Answers

Which of the following conditions is associated with invasive strains of Haemophilus influenzae?

Pneumonia (correct)

Sinusitis

Conjunctivitis

Otitis Media

What percentage of invasive H. influenzae infections in the United States is caused by non-typeable strains (NTHi)?

70% (correct)

10%

30%

50%

What condition can occur as a result of epiglottitis caused by Haemophilus influenzae?

Chancroid

Septicemia

Airway obstruction (correct)

Pneumonia

Which serotype of Haemophilus influenzae is most significantly linked to invasive infections before widespread vaccination?

Serotype b Signup and view all the answers

Which of the following diseases is characterized by high mortality and includes symptoms such as conjunctivitis and septicemia?

Brazilian Purpuric Fever Signup and view all the answers

Haemophilus ducreyi primarily causes which type of condition?

Chancroid Signup and view all the answers

In children, which of the following symptoms is commonly associated with meningitis caused by H. influenzae?

Stiff neck Signup and view all the answers

What is a common risk factor that may exacerbate localized infections caused by NTHi strains?

Chronic obstructive pulmonary disease Signup and view all the answers

Which type of Haemophilus influenzae is primarily associated with chronic middle ear infections?

Non-typeable strains Signup and view all the answers

What type of morphology is observed in colonies of Haemophilus influenzae?

Smooth, convex colonies Signup and view all the answers

Which of the following conditions is NOT typically caused by Haemophilus influenzae?

Tuberculosis Signup and view all the answers

In which demographic is the prevalence of chancroid particularly common?

Adults in Latin America, Africa, and Asia Signup and view all the answers

What is a common acute conjunctivitis caused by Haemophilus species?

Acute, contagious "pinkeye" Signup and view all the answers

Which of the following statements about developing countries regarding Haemophilus influenzae infections is accurate?

Serotype b is still a significant cause of mortality. Signup and view all the answers

What type of specimen is preferred for diagnosing respiratory infections associated with Haemophilus species?

Bronchial washing Signup and view all the answers

What is the microscopic characteristic of Haemophilus species?

Small, gram-negative coccobacilli or filaments Signup and view all the answers

Which of the following treatments is effective against non-life-threatening H. influenzae?

Amoxicillin-clavulanate Signup and view all the answers

What is the primary virulence factor associated with Aggregatibacter actinomycetemcomitans?

Leukotoxin Signup and view all the answers

Which test is utilized for detecting β-lactamase production?

Chromogenic cephalosporin test Signup and view all the answers

What type of growth medium does HACEK require for optimal growth?

High CO2 concentration Signup and view all the answers

Which organism is commonly linked to endocarditis and periodontitis?

Eikenella corrodens Signup and view all the answers

What is the colony morphology of Haemophilus species on SBA after 48 hours?

Star shape with four to six points Signup and view all the answers

Which statement about Kingella species is true?

They are resistant to erythromycin. Signup and view all the answers

Which of the following is NOT a treatment option for H. ducreyi infections?

Trimethoprim-sulfamethoxazole Signup and view all the answers

What type of pathogen is B. neotomae classified as?

Facultative intracellular pathogen Signup and view all the answers

Which symptom is NOT associated with the acute stage of brucellosis?

Undulating fevers Signup and view all the answers

What is the primary transmission route for brucellosis?

Foodborne transmission through unpasteurized milk Signup and view all the answers

Which of the following is typically used to help diagnose brucellosis?

Serology in conjunction with disease status Signup and view all the answers

What is the proper growth condition required for the culture of Brucella?

Requires CO2 Signup and view all the answers

Which risk group is NOT typically associated with exposure to brucellosis?

Office workers Signup and view all the answers

What is the typical yield of positive blood cultures in chronic cases of brucellosis?

5% Signup and view all the answers

Which biochemical test result would help differentiate Brucella from similar organisms?

Positive urease test Signup and view all the answers

What is the primary clinical form associated with Francisella tularensis when contracted through inhalation?

Pneumonic Signup and view all the answers

What is the biosafety level recommended for handling Brucella spp. in laboratory settings?

Biosafety level 3 Signup and view all the answers

What are the common symptoms of tularemia?

Ulcer formation and swollen lymph nodes Signup and view all the answers

Which type of Francisella tularensis is known to cause the most severe disease?

Subsp. tularensis Signup and view all the answers

What type of agar is typically NOT recommended for culturing Francisella tularensis due to aerosol risk?

Thioglycollate broth Signup and view all the answers

Which of the following media does NOT support the growth of Francisella tularensis?

Eosin methylene blue agar Signup and view all the answers

What is the case fatality rate associated with tularemia in the United States?

2% to 9% Signup and view all the answers

Which of the following characteristics is NOT true regarding Francisella spp.?

They are gram-positive bacteria Signup and view all the answers

Study Notes

Haemophilus influenzae

Historically, Haemophilus influenzae was named during the 1898-1890 influenza pandemic due to its frequent isolation from patients.
Invasive disease is caused by encapsulated strains.
Non-typeable strains (NTHi) cause localized disease.
Serotype b (Hib) was the primary cause of bacterial meningitis before widespread vaccination.
In the United States, 70% of invasive H. influenzae infections are caused by NTHi strains.
Serotype f accounts for 18% of invasive infections.
Annual estimates suggest 6,100 invasive cases and 1,015 deaths in the United States.
Serotype b remains a significant cause of bacterial pneumonia and meningitis deaths in children in developing countries due to lack of vaccination.

Haemophilus aegyptius

Causes acute, contagious conjunctivitis known as "pinkeye".

Haemophilus ducreyi

Causes chancroid, a highly communicable genital ulcer disease.
Characterized by nonindurated, painful lesions and inguinal lymphadenopathy.

Haemophilus parainfluenzae

Low pathogenicity; may cause otitis media, acute sinusitis, and rare endocarditis, often post-dental procedures.

Haemophilus parahaemolyticus

Rarely causes pharyngitis.

Aggregatibacter aphrophilus

Previously classified as Haemophilus aphrophilus, Aggregatibacter segnis, and H. paraphrophilus.
Involved in endocarditis and bone/joint infections.

Aggregatibacter actinomycetemcomitans

Previously classified as Actinobacillus actinomycetemcomitans.
Linked to periodontitis and endocarditis.
Produces collagenase and a leukotoxin toxic to polymorphonuclear cells and monocytes.

Cardiobacterium hominis

Gram-negative bacilli often associated with endocarditis.

Kingella spp.

Causes endocarditis, bacteremia, and other infections, often in immunocompromised or debilitated individuals.
Commonly associated with dental procedures.

Laboratory Diagnosis of Haemophilus spp.

Common specimens include blood, CSF, middle ear exudate, joint fluids, respiratory tract specimens, conjunctivae swabs, vaginal swabs, and abscess drainage.
Bronchial washing is preferred for respiratory specimens.
H. influenzae colonies exhibit smooth, convex morphology with a distinct odor.
H. ducreyi colonies are small, flat, tan or yellow with a "clumpy" appearance.
H. aegyptius colonies resemble H. influenzae but require enriched media.
Microscopic morphology reveals small, gram-negative cocco-bacilli or filaments.

HACEK Organisms

HACEK is an acronym for a group of gram-negative bacilli known for their fastidious growth requirements and association with endocarditis.
The group includes Haemophilus spp. (e.g., H. paraphrophilus), Aggregatibacter actinomycetemcomitans (formerly Actinobacillus actinomycetemcomitans and A. aphrophilus), Cardiobacterium hominis, Eikenella corrodens, and Kingella spp.

Brucella spp.

Facultative intracellular pathogens residing within mononuclear phagocytic cells.
Considered a category B select biological agent due to its ease of dissemination and moderate morbidity.
Risk groups include veterinarians, hunters, laboratory workers, and individuals exposed to animals or animal products.
Transmission routes include aerosols, percutaneous exposure, and oral ingestion of unpasteurized milk.
The disease is reportable with approximately 100 cases reported annually in the United States.
Acute stage symptoms include fever, malaise, headache, anorexia, arthralgia, myalgia, and back pain.
The subchronic/undulant stage is characterized by undulating fevers, arthritis, and epididymoorchitis.

Francisella tularensis

The primary species causing human infections.
Subspecies include:
- F. tularensis subsp. tularensis (Type A): Causes the most severe disease.
- F. tularensis subsp. holarctica (Type B): Produces a similar disease but is less fatal.
- F. tularensis subsp. mediasiatica: Less commonly associated with human disease
Other species are less commonly associated with human infections.
The disease is known as Tularemia, rabbit fever, deerfly fever, lemming fever, and water rat trappers' disease.
Transmission occurs via ingestion, inhalation, arthropod bites (ticks, biting flies), or contact with infected tissues.
Case fatality rate is 2% to 9% in the U.S.
Symptoms vary by form but may include fever, ulcer formation, swollen lymph nodes, pneumonia, and systemic symptoms.

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Description

This quiz covers key aspects of the Haemophilus genus, including Haemophilus influenzae, H. aegyptius, and H. ducreyi. Learn about the diseases they cause, notable strains, and their impact on public health. Test your knowledge on the history and clinical significance of these bacteria.