HEAMOPHILUS; BORTEDELLA AND BRUCELLA

• gram-negative, plemorphic bacteria that require enriched media

• hemophilus unfluenza (major one), h ducreyi (sexual transmitted), aggregatibacter aphrophilus (h aphrophilus + h paraphrophilus)

• found on mucous membranes in upper respiratory tract

• causes menigitis in unvaccinated children

• causes upper and lower respiratory tract infections

A. Typical organism

• short, coccoid bacilli, in pairs or short chains

B. Culture

• chocolate agar, flat grayish, translucent colinies

• 1-2 mm after 24 hours incubation; IsoVitaleX enhances growth

• does not grow on blood agar from sheep, except around colonies of staphylococci (satellite phenomenon; release of NAD from staphylococcus)

C. growth characteristics

• need for X or V growth factor (X= hemin; V= nicotinamide adenine dinucleotide NAD)

• H influencae and h para influencae can be biotyped on basis of production of indole, ornithine, decarboxylase and urease

• encapsulated h influencae contains capsular polyssacharides (six types)

• type B is polyribitol ribose phosphate (PRP)

• encapsulated can be typed by slide agglutination, coagglutination with staphylococci or agglutination of latex particles

• most h influencae are uncapsulated and present in the upper respiratory normal microbiota and referred as nontypeable (NTHi)

• somatic antigens of H influencae consists of outer membrane proteins. Lipooligosaccharides (endotoxins) share structures with those of neisseriae

• produces no endotoxin

• nonencapsulated organism is normal respiratory microbiota of humans

• capsule is antiphagocytotic

• major virulence factor is polyribose phosphate capsule of type B H influencae

• type B causes: meningitis, pneumonia, empysema, epiglottitis, cellulitis, septic arthritis and invasive infections

• NTHi causes: chronic bronchitis, otitis media, sinusitis and conjunctitis

• type B enters by respiratory tract

• h influencae and pneumococci are more common etiologic agents for bacterial otitis emdia and sinusitis

• lower respiratory tract infections (bronchitis, penumonia) in patients with reduced mucociliary clearance (smoking, COPD, cystic fibrosis)

• encapsulated organism may reach blood stream (septic arthritis)

• fulminating obstructive laryngotracheitis in young children

• pneumonia and epiglottitis by young and old patients

• bronchitis and penumonia by adults

B. Direct identification

• gram stain

C. Culture

• grown on IsoVitaleX-enriched chocolate agar

• needs X and V factor and lack of hemolysis on blood agar

• Test for X requirement: h influencae inable to synthetise heme from delta-aminolevulinic acid; the ones that dont need X produce porphysins, porphobilinogen, protoporphyrin IX and heme - under ultraviolett light visible if test positive

• routine vaccination with protein-polysaccharide conjugated vaccine (Hib)

• significant reduction of serious, life-thereatining infection in children

• recommended at 2 month of age