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Questions and Answers
What is the primary habitat for Bartonella baciliformis?
Which symptom is associated with Carrion's disease caused by Bartonella baciliformis?
What is a significant virulence factor of Bartonella species?
How is Bartonella henselae primarily transmitted?
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What is the characteristic appearance of colonies from the Bartonella genus when cultured?
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Which of the following factors is essential for the growth of Haemophilus species?
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What is the primary agar used to cultivate Haemophilus species due to its nutritional components?
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Which diseases are commonly associated with Haemophilus ducreyi?
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What unique phenomenon allows Haemophilus species to grow on blood agar plates?
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How is Haemophilus ducreyi primarily transmitted among individuals?
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What type of cellular morphology do members of the Haemophilus genus exhibit?
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Which identification medium for Haemophilus ducreyi includes vancomycin to suppress gram-positive bacteria?
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What characteristic of Staphylococcus aureus causes the satellite phenomenon?
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What is the primary characteristic of Haemophilus ducreyi colonies?
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Which factor is required for the growth of Haemophilus ducreyi?
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What is the recommended treatment for infections caused by Haemophilus ducreyi?
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What differentiates Haemophilus haemolyticus from Haemophilus influenzae in identification?
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Which virulence factor is associated with encapsulated strains of Haemophilus influenzae?
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What fermentation activity is NOT observed in Haemophilus ducreyi?
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What infection is commonly associated with encapsulated strains of Haemophilus influenzae?
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What is one characteristic of Haemophilus influenzae unencapsulated strains?
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What is a common resistance pattern found in Haemophilus influenzae?
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What is the primary mode of transmission for Haemophilus influenzae?
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What is the primary route of human infection by Brucella species?
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Which of the following diseases is mainly caused by Legionella pneumophila?
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What characteristic distinguishes Brucella species from other organisms?
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Which antimicrobial is NOT recommended for the treatment of Legionella pneumophila infections?
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What is the result of the urea breath test when Helicobacter pylori is present?
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Which of the following is NOT a preferred animal host for Brucella species?
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What type of media is essential for the growth of Legionella pneumophila?
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How is Helicobacter pylori typically identified in biopsy specimens?
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Which of the following is true about the virulence factors of Brucella species?
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Which of the following symptoms is NOT commonly associated with brucellosis?
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Which test can be used for the direct identification of Legionella pneumophila in respiratory specimens?
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Which of the following is NOT an effective treatment regimen for Helicobacter pylori?
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What is the primary form in which tularemia presents when associated with lymphadenopathy and ulcers?
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Which antibiotic is considered the drug of choice for treating tularemia?
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What is a common transmission route for Streptobacillus moniliformis to humans?
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What characteristic morphology can Streptobacillus moniliformis exhibit under a microscope?
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Which type of tularemia is considered the most serious form, often acquired through inhalation?
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Which statement about the antimicrobial susceptibility of Francisella tularensis is true?
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Which symptom is typically associated with rat-biter fever caused by Streptobacillus moniliformis?
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What characteristic of Francisella tularensis colonies can be observed during isolation?
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What complicating condition can arise from a Streptobacillus moniliformis infection?
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Which of the following accurately describes the epidemiology of Streptobacillus moniliformis?
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In the context of bioterrorism agents, which bacteria is classified as a Category A agent?
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Study Notes
Haemophilus Species
- Small, nonmotile, gram-negative bacilli
- Typically coccobacillary or short rods
- Need X factor (hemin) and/or V factor (NAD or NADP) to grow
- Chocolate agar is the best medium for Haemophilus species, BAP lacks V factor
- Satellite phenomenon when Staphylococcus aureus grows alongside Haemophilus on BAP: Staphylococcus breaks down red blood cells releasing X and V factors for Haemophilus to utilize
Haemophilus ducreyi
- Not part of normal human flora
- Transmitted person-to-person through sexual contact
- Causes chancroid: genital lesions progress from papules to painful ulcers
- Regional lymphadenitis is common
- Grow on Mueller Hinton, BHI, and chocolate agar
- Colonies are small, smooth and can be pushed intact across the agar surface ("hockey puck")
- Requires X factor, but not V factor
- Non-hemolytic, catalase negative, variable glucose fermentation, negative xylose, sucrose, and mannose fermentation
Haemophilus haemolyticus
- Part of the normal human flora of the upper respiratory tract
- Transmitted by patient's own strain
- Colonies resemble H.influenzae on CAP, but beta-hemolytic on rabbit or horse blood agar
- Requires both X and V factor for growth
- Beta-hemolytic, catalase positive, glucose fermentation positive, variable xylose fermentation, negative sucrose and mannose fermentation
Haemophilus influenzae
- Part of the normal human flora of the upper respiratory tract
- Transmitted person to person contact, respiratory droplets, patient's own strain
- Encapsulated strains are antiphagocytic and cause serious infections like: meningitis, epiglottitis, cellulitis, septic arthritis, and pneumonia.
- Unencapsulated strains cause localized infections like: otitis media, sinusitis, and conjunctivitis.
- Haemophilus influenzae type b causes the most serious infections.
- Unencapsulated strains are small, smooth, and translucent, while encapsulated strains are larger and mucoid
- Colonies have a distinct mouse nest odor
- Requires X and V factors to grow
- Non-hemolytic, catalase positive, glucose and xylose fermentation positive, sucrose and mannose fermentation negative
Bartonella Species
- Grow on CAP but very slowly on BAP, do not grow on MAC
- Colonies appear after 12 to 14 days, sometimes up to 45 days.
- Short, gram-negative, pleomorphic rod-shaped
- Oxidase and catalase negative
Bartonella bacilliformis
- Only found in humans
- Transmitted via sandflies
- Causes Oroya fever: acute hemolytic bacteremia or a chronic vasoproliferative disease
- Causes Carrion's disease: Produces a wart-like lesion called a verrugo.
- Mortality rate is 40-90% dependent on the host and disease presentation
Bartonella henselae
- Found in domestic cats
- Transmitted by cat bites or scratches, fleas, and ticks
- Causes bacteremia, endocarditis, bacillary angiomatosis
- Causes Cat Scratch Disease (CSD), rheumatic manifestations, bacillary peliosis hepatitis
- 22,000 cases of CSD, 80% in children
- Associated with infection beginning as a papule or pustule at the primary inoculation site, developing into regional tender lymphadenopathy in 1-7 weeks.
Helicobacter pylori
- Found in the stomach
- Transmitted person-to-person through fecal-oral route (Most common)
- Transmitted by saliva (Less common)
- Infects and persists in the gastric epithelium
- Causes gastritis, peptic ulcers, gastric cancer, and MALT lymphoma
- Positive for oxidase and urease
Campylobacter jejuni
- Transmitted through consumption of contaminated food or water
- Causes gastroenteritis, severe gastroenteritis, and bacteremia
- Susceptible to many antimicrobial agents, including macrolides, tetracyclines, aminoglycosides, and quinolones
- Increasing resistance to fluoroquinolones
Legionella pneumophila
- Obligate aerobe, grows best between 20-45°C
- Faintly staining, thin gram-negative bacilli
- Does not grow on routine media, requires iron and L-cysteine for growth
- Utilizes proteins for energy instead of carbohydrates
- Found in aquatic habitats, primarily in warm water and man-made facilities
- Survives up to 14 months in water
- Transmitted through inhalation of aerosols from contaminated sources, NOT person-to-person
- Legionella can multiply within amoebae and certain host cells, as well as within biofilms
- Causes Legionnaires’ disease: Severe pneumonia with 10-20% fatality rate
- Causes Pontiac Fever: Mild, self-limited, nonfatal, influenza-like respiratory infection
- Can also cause extra-pulmonary infections
- Definitive identification requires specialized laboratory testing
- Growth is presumptively identified by growth on BCYE with L-cysteine
- Direct immunofluorescent antibody (DFA) can be used on respiratory secretions to detect Legionella pneumophila
Brucella Species
- Small, facultative intracellular, nonmotile, aerobic, gram-negative coccobacilli
- Require CO2 for growth
- Potential bioterrorism agents
- Grow on BAP and CAP, require special media and conditions for optimal recovery
- Blood culture systems are used to facilitate growth
Brucella abortus
- Found in cattle and buffalo
- Infects humans through consumption of unpasteurized milk, inhalation of infected aerosols, direct contact, and mucosal inoculation
- Causes brucellosis: Systemic infection that can involve any organ in the body
- Symptoms: Fever, chills, weight loss, night sweats, headache, muscle aches, fatigue, depression, lymphadenopathy, and splenomegaly
- Small, convex, smooth, translucent, gamma hemolytic, slightly yellow colonies that brown with age after 48 hours of incubation
- Catalase positive, urease positive, oxidase positive, 2 hours for positive urease, H2S produced, inhibited by thionine, not inhibited by fuchsin
Brucella melitensis
- Found in sheep, goats, and camels
- Most virulent Brucella species in humans
- CO2 not required for growth
- 2 hours for positive urease, H2S negative, not inhibited by any stains
Brucella suis
- Found in swine and wild animals
- CO2 not required for growth
- 15 minutes for positive urease, variable H2S production, not inhibited by thionine, inhibited by fuchsin
Brucella canis
- Found in dogs
- CO2 not required for growth
- 15 minutes for positive urease, H2S not produced, not inhibited by thionine, inhibited by fuchsin
- Colonies are rough instead of smooth
Bordetella Species
- Nonmotile and infect only humans
- Do not grow on MAC
- Bordetella pertussis and Bordetella parapertussis
Tularemia
- Lymph nodes near the inoculation site are enlarged and necrotic.
- Patients become ill systemically once the organism enters the bloodstream.
- Tularemia varies in severity from mild and self-limiting to fatal.
- There are six distinct types of Tularemia.
Types of Tularemia
- Ulceroglandular tularemia: Common with ulcers and lymphadenopathy.
- Glandular tularemia: Common with lymphadenopathy.
- Oculoglandular tularemia: Conjunctivitis and lymphadenopathy.
- Oropharyngeal tularemia: Ulceration in the oropharynx.
- Systemic (typhoidal) tularemia: Acute with septicemia. It does not involve ulcers or lymphadenopathy.
- Pneumonic tularemia: Acquired by inhaling infectious aerosols or spreading from the bloodstream - the most serious form of tularemia.
Identification of Francisella tularensis
- Colonies appear transparent and mucoid.
- Isolates should be sent to a reference lab for confirmatory testing and characterization.
- Possible indications of a Francisella tularensis isolate:
- Unusual gram stain with small, poorly staining gram-negative rods. These rods might appear as single cells or an amorphous gram-negative mass without distinct cell forms.
- Subcultures mainly yield pinpoint colonies on cysteine-heart agar (CAP). It grows better on CAP than blood agar (BAP).
- Oxidase negative.
- Weak catalase positive.
- Small gram-negative rods observed in a positive blood culture where detection time exceeds 24 hours.
Antimicrobial Susceptibility Testing for Francisella tularensis
- No standardized susceptibility test exists.
- Streptomycin is the primary treatment.
- Gentamycin is a potential alternative.
- Fluoroquinolones show promise for treating severe tularemia.
- Antibiotic resistance development is rare.
Streptobacillus moniliformis: General Characteristics
- It is a gram-negative bacillus that requires media containing blood, serum, or ascites fluid.
- It also needs incubation under CO2 for isolation.
- Considered a facultative anaerobe, exhibiting high pleomorphism.
Epidemiology of Streptobacillus moniliformis
- Its natural habitat is the upper respiratory tract of wild and laboratory rats.
- It has been isolated from other animals, including mice, gerbils, squirrels, ferrets, and weasels, after these animals have consumed rodents.
- Isolated from cats and dogs that fed on rodents.
- It is pathogenic to humans and is transmitted through two routes:
- Rat bite, or direct contact with rat feces or saliva.
- Ingestion of contaminated food, such as unpasteurized milk.
- It occurs globally.
Virulence Factors and Spectrum of Disease for Streptobacillus moniliformis
- While the virulence factors are unknown, it is known to spontaneously develop L forms, which are bacteria without cell walls, allowing them to persist.
- The disease state is called rat-bite fever or Haverhill fever.
- Patients develop acute onset of chills, fever, headache, vomiting, and often severe joint pains.
- Symptoms typically occur within 3-10 days after exposure.
- Patients may develop a rash on the palms, soles of the feet, and other extremities.
- Other complications can include endocarditis, septic arthritis, pneumonia, pericarditis, brain abscesses, prostatitis, and pancreatitis.
Identification of Streptobacillus moniliformis
- Streptobacillus moniliformis is a pleomorphic gram-negative rod
- Cells can appear straight, variable in size, or as long, tangled chains and filaments with bulbar swellings.
- It can resemble a string of pearls.
- Growth on BAP can occur after 48 hours of incubation at 37°C.
- Colonies embed in the agar, exhibiting a “fried egg” appearance with a dark center and a flattened, lacy edge.
- These colonies typically transform into the L form, and a gram-stain will reveal bi-polar staining coccoid forms.
- Acridine orange might be used to confirm the presence of bacteria, as a gram-stain heavily relies on the bacterial cell wall.
- Indole Negative.
- Catalase Negative.
- Oxidase Negative.
- Nitrate reduction Negative.
- Nonmotile.
- Urea Negative.
- Lysine decarboxylase Negative.
- H2S is not produced in triple sugar iron agar (TSIA) but can be detected using lead acetate paper.
Antimicrobial Susceptibility Testing for Streptobacillus moniliformis
- No standard methods are established.
- Penicillin is regarded as the drug of choice.
- Aminoglycosides or tetracycline can be used to eliminate the L forms or for patients allergic to penicillin.
Bioterrorism Agents
- Category A – Highest priority agents
- Certain bacteria are categorized as bioterrorism agents due to their:
- Ease of dissemination or person-to-person transmission.
- High mortality rates.
- Potential for public panic and social disruption.
- Requirement for special public health preparedness actions.
- Bacillus anthracis
- Clostridium botulinum toxin
- Yersinia pestis
- Variola major (smallpox)
- Franciscella tularensis
- Ebola
Category B Bioterrorism Agents
- Second highest priority agents
- Category B agents are:
- Moderately easy to disseminate.
- Associated with moderate morbidity rates and low mortality rates.
- Require specific enhancements of the CDC’s diagnostic capacity and enhanced disease surveillance.
- Brucella species
- Epsilon toxin of Clostridium perfringens
- Food safety threats: Salmonella, E. coli, Shigella
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