Hemophilus, Bordatella, Legionella (Ch3) Flashcards
1
Q
What are the characteristics of Haemophilus Influenzae?
A
- Small gram-negative pleomorphic coccobacilli
- Facultative anaerobe
- No flagella
- Non-motile
- Non-spore forming
- Can be divided into 17 subspecies depending on nutritional requirements like Factor X (hemin) and factor V (NAD)
- Must be grown on chocolate agar (Fastidious organism)
- Can be encapsulated (Type a—> Type f) or non-encapsulated (Most cases)
2
Q
What are the species of Haemophilus?
A
• H. influenzae
• H. ducreyi (soft chancre)
• H. aegypticus (purulent conjunctivitis)
3
Q
What is the reservoir for Haemophilus influenzae type b?
A
Human reservoir. Some can be asymptomatic carriers.
4
Q
How is Haemophilus influenzae transmitted?
A
Via respiratory droplets
5
Q
What is the temporal pattern for the emergence for H. influenzae type b?
A
Sept-Dec and March-May
6
Q
What are the risk factors for H. influenzae type b?
A
- Crowded houses
- Childcare (hygiene)
- Low socioeconomic status (hygiene/crowding)
- Low parental education
- School-age siblings
7
Q
What are the virulence factors of Haemophilus influenzae type b?
A
- Capsule: composed of Polyribitol phosphate (PRP)
- Lipid A (endotoxin released into bloodstream)
- IgA proteases: inhibits opsonization by IgA which is present in paranasal mucosal secretions
8
Q
What are the two strains of Haemophilus influenzae that particularly cause infections? Compare their features.
A
-
Nontypeable strains
• More common (in infants)
• Unencapsulated
• Cause local mucosal infections (Otitis media, sinusitis, exacerbation of COPD)
• No vaccine available -
Type b strains
• Uncommon
• PRP capsule
• Cause invasive infections (Meningitis, epiglottis) in children
• Has highly effective PRP conjugate vaccines
9
Q
What is the pathogenesis of Hib?
A
- Haemophilus influenzae enters via respiratory secretions
- The LOS and glycoprotein of the bacteria impair the ciliary function of the oropharynx (usually pushes bacteria out of respiratory tract)
- Bacteria passes across the endothelial and epithelial cells and enters the blood
- If the person is immunocompromised, bacteremia causes meningitis
10
Q
What clinical manifestation is a major indicator of Hib?
A
Epiglottitis (since it is rarely seen in other infections)
11
Q
What are the manifestations of Hib associated cellulitis?
A
- Fever
- Warm, raised, tender reddish areas most often located on one check or in periorbetal region (around eyes)
12
Q
What skin complications could occur to unvaccinated pediatric populations due to Hib?
A
- Severe vasculitis with DIC and gangrene
- Swollen skin
13
Q
What are the diseases associated with Hib? What are their associated symptoms?
A
- Epiglottitis: sore throat, fever, dysphagia (difficulty swallowing), difficulty breathing, drooling, difficulty talking
- Bacteremia: fever, anorexia, lethargy
- Meningitis: headache, altered mental status, difficulty waking up, fever, drowsiness, photophobia, neck stiffness, seizures and coma
- Cellulitis: raised tender areas of violaceous kind
- Osteomyelitis: pain and swelling in affected area, fever
- Septic Arthritis: pain in joints, swelling, decreased mobility
14
Q
What are the diseases associated with nontypeable Haemophilus influenzae?
A
• Otitis Media
• Conjunctivitis
• Sinusitis
• Exacerbation of chronic Obstructive Pulmonary disease
• Community Acquired Pneumonia
• Acute respiratory tract infections in children
• Neonatal and Maternal sepsis (50% mortality)
• Bacteremia and invasive infections
15
Q
Symptoms: headache, altered mental status, difficulty waking up, fever, drowsiness, photophobia, neck
stiffness, seizures and coma
A
Meningitis (Hib)
16
Q
Symptoms: sore throat, fever, dysphagia (difficulty swallowing), difficulty breathing, drooling,
difficulty talking
A
Epiglottis (Hib)
17
Q
Symptoms: runny nose, cough at night, swelling around the eyes, headache, fever.
A
Sinusitis (Nontypeable H. influenzae)
18
Q
Symptoms: runny nose, cough at night, swelling around the eyes, headache, fever.
A
Sinusitis (Nontypeable H. influenzae)
19
Q
Which Hib manifestation was the most common in cases prevaccine?
A
Haemophilus influenzae type b Meningitis accounted for approximately 50%-65% of cases in the prevaccine era
20
Q
What of the treatment of Hib?
A
After hospitalization, treatment with an effective 3rd generation cephalosporin
21
Q
What is the purpose of active immunization with purified capsular polysaccharide (PRP)?
A
The purpose is to provide protection against Haemophilus influenzae type b (Hib) disease using active immunization with purified capsular PRP
22
Q
What is the recommended schedule for administering the vaccine against Hib disease?
A
The recommended schedule is three doses before the age of 6 months, followed by booster doses at 2 months, 4 months, 6 months, and 12-15 months of age.
23
Q
What are the benefits of the PRP conjugate vaccine?
A
- Stimulates T-dependent immunity
- Enhanced antibody production, especially in young children
- Repeat doses elicit booster response
24
Q
What is the causative agent of chancroid?
A
Haemophilus ducreyi is the causative agent of chancroid.
25
What is the hallmark symptom of chancroid?
The hallmark symptom of chancroid is genital ulceration.
26
How does chancroid typically present?
Around **5 to 7 days after exposure**, a *tender papule with an erythematous base* develops on the genitalia or perianal area. Within 2 days, the lesion ulcerates, becomes **painful, and may be accompanied by inguinal lymphadenopathy**.
27
How is chancroid diagnosed?
The diagnosis of chancroid is generally made based on the clinical presentation. A soft, very painful chancre (ulcer) in the genital area is characteristic of chancroid.
28
What are some Haemophilus species and the conditions they are associated with?
H. aegyptius is associated with conjunctivitis, H. ducreyi is associated with chancroid, H. parainfluenzae is associated with bacteremia, endocarditis, and opportunistic infections, H. haemolyticus is associated with opportunistic infections, and H. parahaemolyticus is also associated with opportunistic infections.
29
What are some specimen types used for diagnosing Haemophilus infections?
Specimens used for diagnosing Haemophilus infections include direct needle samples from sinusitis or otitis, sputum, blood, cerebrospinal fluid (CSF), and samples from the base or margin of the ulcer in the case of Haemophilus ducreyi.
30
How do Haemophilus species typically appear under microscopy?
Haemophilus species typically appear as Gram-negative rods ranging in shape from coccobacilli to long, pleomorphic filaments.
31
What are the culture conditions required for Haemophilus species?
• Aerobic or facultative anaerobic
• Grow well in 5-10% CO2 at 35-37oC for 24- 72 hours
• H.influenza require X and V factors
• Grow better on chocolate agar than on blood agar
• For H.aegyptius and H. ducreyi: Chocolat agar supplemented with enrichment media
and antibiotics
32
What are the different Bortadella species?
– B. pertussis
– B. parapertussis
– B. bronchoseptica
– B.holmesii
33
What are the characteristics of Bortadella pertussis?
• Gram negative coccobacillus
• Nonmotile
• Do not ferment carbohydrates
• Fastidious microorganisms.
34
What is the emergence pattern of Pertussis?
Pertusis is cyclic (like influenza) and epidemics occur every 3-5 years
35
What is the route of transmission of Pertussis?
• Spread through direct contact of respiratory secretions.
—> Very contagious
36
Where does the Bortadella pertussis bacteria reside upon colonization?
Resides in upper airway pathways, mostly the trachea and
bronchi.
37
When is pertussis the most contagious?
Most contagious during first few stages of infection (Cattarhal stage)
38
What are the adhesion factors used by Pertussis?
• Filamentous hemagglutinin (FHA)
• Pertactin
> *Pertactin and Filamentous hemagglutinin is an
adhesin that allows the bacterium to adhere to
galactose residues of the glycolipids on the membrane
of ciliated epithelial cells of the respiratory tract.*
• Fimbriae
• Pertussis toxin *also functions as an adhesin. One
subunit of the pertussis toxin remains bound to the
bacterial cell wall while another subunit binds to the
glycolipids on the membrane of ciliated epithelial
cells of the respiratory tract.*
39
What are the virulence factors of Pertussis?
• PT: Pertussis toxin: toxin *inhibits phagocytic killing and monocyte migration*
• Bacterial adenylate cyclase: Increases intracellular level of *adenylate cyclase*
*inhibits phagocytic killing and monocyte migration*
• Dermonecrotic toxin –causing strong *vasoconstrictive* effects.
• Tracheal cytotoxin: A peptidoglycan fragment that *kills ciliated* respiratory cells and stimulates the release of *interleukin-1 (fever)*
• Lipopolysaccharide associated with the surface of the bacteria and has *endotoxin activity.* It *activates alternate complement pathway and stimulates cytokine release.*
40
How does the progression of Pertussis (Whooping cough) go on?
• Incubation period **7-10 days**
• 3 Stages
1st Stage- **Catarrhal Stage** 1-2 weeks
• runny nose, sneezing, low fever, and a mild cough (common mistaken for cold)
2nd Stage- **Paroxysmal Stage** 1-6 weeks
• whooping cough, which consists of bursts or paroxysms of numerous, rapid coughs, severity of the infection is at its greatest
3rd Stage- **Convalescent Stage** weeks-months
• gradual recovery starts
41
What are the complications of Pertussis in both adults and children?
• Adults:
- Pneumonia
- Rib Fracture
- Weight Loss
• Children:
- Hypoxia
- Apnea
- Pneumonia
- Seizures
42
What specimen is taken for Bortadella pertussis isolations?
Nasopharyngeal specimen
43
What clinical finding is a diagnostic factor for Pertussis?
An elevated white blood cell count with a lymphocytosis
44
What culture media is used for the isolation of Bortadella pertussis? How is the media incubated?
– Media: Bordet-Gengou,
• contain blood, potato extract, and glycerol, with an antibiotic such as cephalexin or penicillin and sometimes nicotinamide
• The media should be incubated in air at 35° C and in a humidified chamber. **Prolonged incubation (e.g., 7 to 12 days) is necessary**
45
What other diagnostic tests are used for Pertussis?
• Direct fluorescent antibody (DFA)
• Antibody detection (serology)
• Polymerase Chain Reaction PCR
46
What antibiotics are used to treat Bortadella pertussis?
• Antibiotic Therapy: Macrolide
– Erythromycin
– Azithromycin
– Clarithromycin
Trimethoprim-sulfamethoxazole or fluoroquinolones can be
used in patients unable to tolerate macrolides
47
What are the control measures taken for pertussis?
Sanitary: This very contagious disease requires quarantine for a period of 4-6 weeks
Immunological: Pertussis vaccine is a part of the required "DPT" schedule
Chemotherapeutic: Antibiotic prophylaxis (erythromycin) may be used for contacts
48
What is the pertussis vaccine? How many times is it administered?
• Acellular vaccine
• Inactivated pertusis toxin, filamentous hemagglutinin and pertactin
• 5 doses: 2m, 4m, 6m, 15 to 18 months and 4 to 6 years
• Adult: 11-12 years and between 19 and 65
• Combination vaccines (dpt vaccine)
49
What are the drawbacks to Pertussis vaccine?
• Complications/Safety
• Immunity
• Strain Variability
50
What are the benefits and disadvantages of Pertussis vaccine?
• Pertusis vaccine protects from severe disease better than carriage
• Promotes little immunity and little protection from transmission
• Immunization does not yield life long immunity which may account for more frequent occurrence in teenagers and adults today
51
How are pertussis cases developing? Are there decreased cases due to vaccination?
No. The incidence of disease is increasing, even with high vaccination rates
52
What are the characteristics of other Bortadella species (B. Parapertussis, B. Bronchoseptica, B. holmesii)?
B. Parapertussis : causes a mild form of whooping cough
B. Bronchoseptica : Occasionally causes respiratory or wound infections
B. holmesii: is primarily associated with septicemia.
53
What is legionella?
• A naturally occurring bacterium
• Found in most water systems
• Easily colonises most
domestic water systems – hot and cold
• More than 50 species (most common: **L. pneumophila**)
54
What are the characteristics of Legionella?
- A thin and flagellated gram- negative bacterium.
- Non-capsulated rod-like bacteria.
- Obligate aerobes
- Nutritionally fastidious (require cysteine and iron)
- **Facultative intracellular parasites **
- weakly staining
55
When does legionellosis most commonly occur?
Usually occur in the summer and early fall, but cases may occur year-round.
56
What is the mortality rate of Legionnaires disease?
About
5% to 30% of people who have Legionnaires' disease die.
57
How is legionellosis spread?
• Legionella are typically associated with **aerosolized** water (central air conditioning, cooling towers, showers, whirlpool spars).
• Disease is generally **waterborne; transmission occurs via airborne droplets.**
58
Where is the Legionella bacterium found?
• The organisms exist in many types of water systems in nature; humans are an accidental host.
• The bacteria are commonly present in natural bodies of water such as lakes and streams, as well as in air conditioning cooling towers and condensers and in water systems (hot tabs, showers)
59
What is the emergence pattern of Legionellosis?
Sporadic occurrences
60
What is the pathogenesis of Legionellae?
Legionellae are facultative intracellular parasites that multiply in free-living amoebae in nature and in alveolar macrophages, monocytes, and alveolar epithelial cells in infected hosts
The organisms proliferate in their intracellular vacuole and produce proteolytic enzymes, phosphatase, lipase, and nuclease that eventually kill the host cell when the vacuole is lysed
61
What are the risk factors for infection with legionella?
- Opportunistic Disease: underlying illness/weak immune
system.
- Nosocomial infections are major concerns.
- Middle-aged, elderly, COPD, smokers, alcoholic and other
genetic susceptible patients such as persons with chronic
lung are primary targets
62
Can L.pneumophilia be spread from human-human interaction?
No
63
What are the two clinical manifestations of Legionella infection?
1. Pontiac fever: Influenza like illness
2. Legionnaire disease: Severe pneumonia
64
What are the two clinical diseases of Legionella infection?
1. Pontiac fever: Influenza like illness
2. Legionnaire disease: Severe pneumonia
65
What are the early symptoms of legionella infection?
Neurological symptoms like Malaise, muscle aches, lethargy and slight headaches.
High Fever, non-productive cough, abdominal pain,
diarrhea.
66
What are the symptoms of Pontiac fever?
Symptoms: fever, chills, myalgia and headache, absence of pneumonia
> Self limited
67
What are the symptoms of Legionnaires disease?
Legionnaires disease: Complication of Pontiac fever
High morbidity
Symptoms: fever and chills, a dry nonproductive cough, headache
Lung tissue inflammation
Microabscesses in lung tissues
68
What clinical findings are used to forebode Legionella infections?
- Symptoms include headache, malaise, rapid fever, nonproductive cough,
- Chest X-rays show pneumonia
69
What specimens are taken to isolate Legionella?
Sample: BAL (bronchoalveolar lavage), sputum, lung biobsy, urine, plasma
70
What culture media and conditions are used for growth of Legionella?
Buffered charcoal yeast extract (BCYE) agar: supplemented with l-cysteine and iron for primary isolation
Growth at 5% CO2 and 35 C for 4 day
71
Prevention techniques for legionellosis?
• Regular maintenance of air conditioning or the inclusion of biocidal compounds into water cooling towers reduces the reservoir.
• Similarly, hyperchlorination of the water supply eliminates the source.
