Medical Microbiology

Haemophilus and Bordetella

Chapter 31

551-564

Haemophilus and Bordetella Small, Gram-negative coccobacillary shape.

Exclusively found in humans

The major species are Haemophilus influenzae, the cause of acute purulent meningitis

Bordetella pertussis, the cause of whooping cough.

BordetellaGeneral Characteristics

Gram –negative coccobaccili (rod-shaped) single or paired

Obligate aerobe – Requires O2 to live

Colonizes the respiratory tract

Specific to human hosts

7 species, The main species

1. B. pertussis: Whooping Cough (Pertussis)

1. B. parapertussis

2. B. bronchiseptica

EPIDEMIOLOGY Pertussis is a major health problem worldwide,

Bordetella pertussis is spread by airborne droplet nuclei and remains localized to the trachobronchial tree.

It is highly contagious, infecting more than 90% of exposed susceptible persons.

Virulence Factors Adhesions

1. Filamentous hemagglutinin

(FHA)

2. Pertactin

3. Agglutinogen

Anchor Bordetella to epithelium

Colonization of tracheal epithelial

cells by Bordetella pertussis

Virulence Factors Toxins

1. Tracheal Cytotoxin (TCT)

Direct toxicity to tracheal epithelium

Paralysis of the cilli…mucous build up….trigger violent cough reflex to clear airway

Although considerable local inflammation

and exudate are produced in the bronchi, B pertussis does not directly

invade the cells of the

respiratory tract or spread to deeper tissue sites

Virulence Factors Toxins

1. Pertussis Toxin (PTX)

Anchoring it to epithelial surface

Increase level of lymphocytes in blood (T-cells)

Stimulate T cell to divide and inhibit it from leaving

the blood

Increase sensitivity of respiratory tissue to

histamine…. Fluid enter airway

tissue…swelling….hard to breath….classic

whooping sound

Virulence Factors Toxins

1. Adenylate Cyclase Toxin (CYA)

Invasive toxin

Activated by host cell calmodulin

Apoptosis, inhibit cell signal, inhibit immune cells

Inhibit phagocytes to get to site of infection and kill

bacteria

Pathogenesis Attached to tracheal epithelium

After attachment: bacteria immobilize cilia: destroy ciliated cell

Produce epithelium devoid the ciliary blanket

Persistent coughing

Clinical Presentation:

Whooping Cough

Incubation period 4-21 days

3 Stages

1. Catarrhal Stage 1-2 weeks

2. Paroxysmal Stage 1-6 weeks

3. Covalescent Stage weeks-months

Clinical Presentation:

Whooping Cough

Catarrhal Stage 1-2 weeks nose, sneezing, low fever, and a mild cough (common mistaken for cold)

Runny nose

Nasal congestion

Red, watery eyes

Fever

Cough

The disease is most communicable at this stage

because large numbers of organisms are present in the

nasopharynx and the mucoid secretions.

Clinical Presentation:

2. Paroxysmal Stage 1-6 weeks

whooping cough, which consists of uninterrupted fit of

coughing followed by an inspiratory whooping noise

End with a high-pitched "whoop" sound during the next

breath of air (closed swollen epiglottis)

up to 50 times

a day for 2 to 4 weeks

Severe and prolonged coughing attacks may:

Provoke vomiting

Collapsed lung

Tiny petechial in the face

Hernias

Cause extreme fatigue

Children

In infants — especially those under 6 months of age — complications from

whooping cough are more severe and may include:

Pneumonia (superinfecting

organism such as Streptococcus pneumoniae)

Slowed or stopped breathing

Dehydration or weight loss due to feeding difficulties

Seizures

Brain damage

related to the venous pressure effects of

the paroxysmal

coughing and the anoxia produced by

inadequate ventilation and apneic spells.

Clinical Presentation:

Whooping Cough

1. Covalescent Stage weeks-months

Gradual recovery starts

Airway heal

Laboratory Diagnosis

Gram stain

Isolation by culture

(nasopharyngeal specimens)

Regan-Lowe Agar

charcoal agar incubated at 35/37 °C

for at least 3 days

Growth required special medium with supplement nicotinamide ,additive charcoal to Slow growth 3-7 days

Throat swabs are not suitable because the

cilia to which the organism attaches are not

found there

Specimens collected early in the course of disease

(during the catarrhal or early paroxysmal stage) provide the greatest chance of

successful isolation.

Laboratory Diagnosis

Polymerase Chain Reaction (PCR)

Direct fluorescent antibody (DFA)

Bordettela antibodies detection by

ELISA

Treatment Once the paroxysmal coughing stage has been reached, the treatment of

pertussis is primarily

supportive.

Antimicrobial therapy is useful at earlier stages

macrolides are preferred for both treatment and prophylaxis.

Treatment and Prevention

Antibiotic Therapy

Erythromycin

Azithromycin

Clarithromycin

Pertussis vaccine

Diphtheria, Tetanus, and Pertussis

(DTP) vaccine as early as 6 weeks

but no later than 6 y/o

Haemophilus - General Characteristics

Short (1.0-1.5 m) coccobacilli

Aerobic

Non motile

During late 19th century believed to cause influenza

Severe bacterial infection, particularly among infants

Major pathogens for which humans are natural hosts

1. Haemophilus influenzae

2. Haemophilus ducreyi-

H ducreyi Induce sexually transmitted diseases (chancroid)

Africa and southeast Asia

Tender papule in the external genetalia that erode and cause painful ulcer

Haemophilus influenzae

H. influenza has a polysaccharide capsule

Six different serotypes (a-f) of polysaccharide capsule

95% of invasive disease caused by type b (Hib) which contain polyribose-ribitol phosphate (PRP) capsule

Require to use the culture media enriched with blood or blood product

Need exogenous hematin (X factor)

Need nicotinamide adenine dinucleotide NAD (V factors)

Epidemiology Transmitted via respiratory droplets, or direct contact

with contaminated secretions.

Normal flora of the human respiratory tract and oral cavity, nasphyarunx (20-80%) non tybable Hi,capsulated strai are not rare

Incidence of invasive disease in children

0

5

10

15

20

25

1990 1992 1994 1996 1998 2000 2002 2004

Inc

ide

nc

e

Incidence of Invasive Hib Disease

*Rate per 100,000 children

Virulent Factors

Antiphagocytic polysaccharide capsule is the major

pathogenesis factor

Lipopolysaccharide lipid A component from the cell

wall (major role in non capsule strains) ntiphagocytic

effect

All virulent strains produce neuraminidase and an

IgA protease

Lipooligosaccharide (LOS) : toxic to cilli and

respiratory epi

No exotoxins

Pathogenesis

Organism colonizes nasopharynx followed by:

1. Local invasion: otitis media and sinusitis (90% NTHi)(OM, sinusitis, chronic bronchitis)

2. Systemic invasion: blood – bacteremia –meningitis, bone, joint

Cellulitis

6%

Arthritis

8% Bacteremia

2%

Meningitis

50%

Epiglottitis

17%

Pneumonia

15%

Osteomyelitis

2%

*prevaccination era

Hib Clinical Presentations Pre-vaccination

Meningitis

Accounted for approximately

50%-65% of cases in the prevaccine era

Hearing impairment or neurological sequelae in

15%-30%

Case-fatality rate 2%-5% despite of effective

antimicrobial therapy

Laboratory Diagnosis Gram stain

Requires 2 erythrocyte factors for growth:

X (hemin) and V (NAD). X & V factors

are released following lysis of RBCs

Culture:

IsoVitaleX-enriched chocolate agar

Small cooci-bacilli gram negative grow on

chocolate agar but not in blood agar

that grow on chocolate agar but not blood agar strongly suggest Haemophilus

Laboratory Diagnosis Biochemical tests:

Catalase, oxidase, nitrate reduction

and glucose fermentation all positive

Serological tests for serotyping (anti-a, b..)

Treatment and Prevention

Hospitalization required

Treatment with an effective 3rd generation

cephalosporin, or chloramphenicol plus

ampicillin

Prevention by vaccination and reduce risk

factors