Haemophilus

Allied Guru

Introduction

  • Haemophilus ek genus hai jo small, pleomorphic, Gram-negative bacteria ka hota hai, jo commonly human upper respiratory tract mein paya jata hai.
    Is genus ke members normal commensals ke roop mein bhi exist kar sakte hain ya phir suitable conditions mein pathogenic organisms ki tarah act kar sakte hain.
  • Is genus ka sabse important pathogenic species Haemophilus influenzae hai, jo respiratory aur invasive infections ki wide variety ke liye responsible hota hai.
  • Haemophilus species fastidious organisms hote hain, jinko laboratory mein grow karne ke liye special growth factors ki requirement hoti hai.
  • Haemophilus ke dwara hone wale infections infants, young children, elderly individuals aur immunocompromised patients mein zyada common hote hain.
  • Capsulated strains, especially type b, severe systemic infections jaise meningitis aur septicemia se associated hote hain.
  • Haemophilus infections mainly respiratory droplets ke through spread hote hain.
  • Apni clinical importance ki wajah se, Haemophilus medical microbiology ka ek important organism hai, khas taur par MLT aur blood bank students ke liye.
  • Early diagnosis, appropriate antibiotic therapy aur effective vaccination Haemophilus infections ke prevention aur control ke liye essential hain.

 

General Character

  • Family: Pasteurellaceae
  • Gram reaction: Gram-negative
  • Morphology:
    Small, pleomorphic bacilli
    Aksar coccobacilli ke roop mein appear karte hain
  • Arrangement:
    Single cells
    Pairs ya small groups
  • Motility: Non-motile
  • Spore formation: Non-spore forming
  • Oxygen requirement:
    Facultative anaerobes
  • Growth nature:
    Fastidious organisms
    Enriched media ki requirement hoti hai
  • Special growth factors:
    X factor (Hemin)
    V factor (NAD / NADP)
  • Capsule:
    Kuch strains mein present hota hai (H. influenzae type b)
    Important virulence factor hota hai
  • Biochemical nature:
    Oxidase positive
    Catalase positive
  • Habitat:
    Upper respiratory tract ka normal flora (kuch species)

 

Morphology

  • Gram reaction:
    Gram-negative
    Gram staining par pink color mein dikhai dete hain
  • Shape:
    Small pleomorphic bacilli
    Aksar coccobacilli ke roop mein dekhe jate hain
  • Size:
    Bahut chhote bacteria (tiny rods)
  • Arrangement:
    Single cells ke roop mein paye jate hain
    Pairs ya small groups mein bhi dikh sakte hain
  • Capsule:
    Kuch species mein present hota hai (jaise Haemophilus influenzae type b)
    Capsule ek important virulence factor hai
  • Motility:
    Non-motile
  • Spore formation:
    Non-spore forming
  • Pleomorphism:
    Shape aur size mein variation dikhate hain, especially clinical specimens mein

 

Cultural Characteristics

  • Growth requirement:
    Fastidious organism (enriched media ki requirement)
  • Essential growth factors:
    X factor (Hemin) – heme synthesis ke liye required
    V factor (NAD / NADP) – growth aur metabolism ke liye required
  • Ordinary media:
    Simple media jaise nutrient agar par grow nahi karta
  • Chocolate agar:
    Growth ke liye best medium
    Heating se X aur V factors release hote hain
    Small, smooth, moist, translucent colonies produce karta hai
  • Blood agar:
    H. influenzae akela grow nahi karta
    Staphylococcus aureus ke around satellite phenomenon show karta hai
    Staphylococcus V factor provide karta hai
  • Selective media:
    Chocolate agar with antibiotics (jaise bacitracin) throat specimens ke liye use hota hai
  • Colony morphology:
    Small, convex, grayish, dew-drop jaise colonies
    Capsulated strains larger aur mucoid colonies form karte hain
  • Atmosphere:
    5–10% CO₂ mein best grow karta hai (capnophilic)
  • Temperature:
    35–37°C par optimal growth hoti hai

 

Biochemical Reactions

  • General Biochemical Characteristics
  • Oxidase test: Positive
    Catalase test: Positive (most species)
    Indole test: Variable (species dependent)
    Urease test: Negative
    Nitrate reduction: Positive
  • Carbohydrate Fermentation
  • Fermentation gas production ke bina hota hai
  • Species Glucose Sucrose Lactose Indole
    H. influenzae + – – Variable
    H. parainfluenzae + + – +
    H. ducreyi – – – –
    H. aegyptius + – – –
  • Other Important Tests
  • Porphyrin test (ALA test):
    H. influenzae → Negative (X factor require karta hai)
    H. parainfluenzae → Positive (X factor require nahi karta)
  • ONPG test: Negative

 

Pathogenicity

  • Virulence Factors
  • Capsule
    Capsulated strains mein present hota hai (especially H. influenzae type b – Hib)
    Phagocytosis ko prevent karta hai
    Major virulence factor hai
  • Lipooligosaccharide (LOS)
    Endotoxin ki tarah act karta hai
    Inflammation aur tissue damage cause karta hai
  • IgA protease
    Secretory IgA ko destroy karta hai
    Respiratory mucosa ki colonization mein help karta hai
  • Fimbriae (Pili)
    Epithelial cells se adherence mein madad karte hain
  • Outer membrane proteins (OMP)
    Attachment aur immune evasion mein help karte hain
  • Pathogenesis
  • Respiratory ya genital mucosa ke through entry
    Pili ki madad se epithelial cells se adherence
    Local multiplication
    Bloodstream mein invasion (mainly capsulated strains)
    Distant organs tak spread → meninges, lungs, joints
  • Diseases Caused
  • Haemophilus influenzae
  • Upper respiratory tract infections
    Otitis media
    Sinusitis
    Epiglottitis
  • Lower respiratory tract infections
    Pneumonia
  • Invasive diseases
    Meningitis (Hib)
    Septicemia
    Septic arthritis
  • Haemophilus ducreyi
  • Chancroid
    Painful genital ulcer
    Soft, non-indurated edges
    Painful inguinal lymphadenitis (bubo)
  • Haemophilus aegyptius
  • Acute conjunctivitis (pink eye)
  • Host Factors
  • Zyada common hota hai:
    Children mein
    Immunocompromised individuals mein
    Unvaccinated persons mein

Laboratory Diagnosis

1. Specimen Collection

  • Haemophilus influenzae

    Sputum

    Throat swab

    Blood

    Cerebrospinal fluid (CSF)

  • Haemophilus ducreyi

    Genital ulcer se pus ya exudate

  • Haemophilus aegyptius

    Conjunctival swab

2. Direct Microscopy

  • Gram staining

    Small Gram-negative pleomorphic bacilli / coccobacilli

  • CSF examination

    Meningitis cases mein Gram-negative bacilli dikhte hain

3. Culture

  • Chocolate agar

    Medium of choice

    35–37°C, 5–10% CO₂ par incubation

  • Blood agar

    Staphylococcus aureus ke around satellite phenomenon show karta hai

  • Selective media

    Chocolate agar with bacitracin (respiratory specimens)

4. Identification Tests

  • X aur V factor requirement

    H. influenzae → dono X & V require karta hai

  • Porphyrin (ALA) test

    H. influenzae mein negative

  • Biochemical tests

    Oxidase: Positive

    Catalase: Positive

    Sugar fermentation pattern species identification ke liye

5. Serological Tests

  • Capsular antigen detection

    Latex agglutination test (CSF)

    Hib meningitis mein useful

6. Molecular Methods

PCR
Rapid aur sensitive detection
Culture-negative cases mein useful

7. Antimicrobial Sensitivity Testing

Isliye kiya jata hai kyunki:
β-lactamase producing strains hote hain
Therapy guide karne mein madad karta hai

Antibiotic Resistance

  • Mechanisms of Resistance
  • β-lactamase production
    Sabse common mechanism
    Ampicillin aur penicillin ke against resistance cause karta hai
    Enzyme β-lactam ring ko tod deta hai
  • Altered Penicillin-Binding Proteins (PBPs)
    β-lactamase–negative ampicillin-resistant (BLNAR) strains mein dekha jata hai
    β-lactam antibiotics ke liye affinity kam ho jati hai
  • Efflux pumps
    Macrolides aur tetracyclines ke against resistance mein contribute karte hain
  • Target site modification
    Fluoroquinolones ke against resistance cause karta hai (rare but reported)
  • Commonly Resistant Antibiotics
  • Ampicillin
    Penicillin
    First-generation cephalosporins
    Macrolides (kuch strains mein)
  • Usually Effective Antibiotics
  • Amoxicillin + clavulanic acid
    Second aur third-generation cephalosporins
    Cefuroxime
    Ceftriaxone
    Fluoroquinolones (adults)
    Azithromycin (variable sensitivity)
  • Detection of Resistance
  • β-lactamase test
    Nitrocefin test (rapid)
  • Antibiotic sensitivity testing
    Disk diffusion / MIC methods

 

Prevention

1. Vaccination

Hib vaccine (Haemophilus influenzae type b)
Sabse effective preventive measure
Meningitis, pneumonia, epiglottitis, septicemia ko prevent karta hai
Infancy mein routine immunization ke part ke roop mein diya jata hai
Pentavalent / hexavalent vaccines ke form mein available

2. Chemoprophylaxis

Rifampicin
Hib meningitis cases ke close contacts ko diya jata hai
Secondary spread ko prevent karta hai

Indicated for:
Household contacts
Daycare contacts

3. Infection Control Measures

Proper hand hygiene
Respiratory etiquette (cough/sneeze cover karna)
Zarurat padne par infected patients ka isolation

4. Early Diagnosis and Treatment

Time par identification aur appropriate antibiotic therapy
Transmission aur complications ko reduce karta hai

5. Public Health Measures

Routine childhood immunization programs
Antibiotic resistance ki surveillance
Health education aur awareness

6. Sexually Transmitted Infection ki Prevention (H. ducreyi)

Safe sexual practices
Chancroid ka early diagnosis aur treatment
Partner notification aur treatment