Module 9 Lecture

  • gram negative bacilli

  • Haemophilus

    • Domain: bacteria

    • Phylum: proteobacteria

    • Class: gamma-proteobacteria

    • Order: pasteurellales

    • Family: Pasteurellaceae

    • Genus: Haemophilus

    • Species: Haemophilus influenzae, H. ducreyi, H. aegyptius

      • genome — total genome size 1.9 megabases, 38% GC content, about 1,800 genes total

  • general characteristics

    • gram negative, small polymorphic (can appear bacilli or coccobacillus)

    • nonmotile

    • non-spore-forming

    • facultative anaerobes

    • catalase positive (mostly)

    • oxidase positive (mostly)

    • found in mucus membranes; in animals & humans because they are fastidious

    • blood lovers & require growth factors that are present in the blood

      • X-factor (hematin)

        • available in BAP; add sheep blood to TSA media or chocolate agar

      • V-factor (nicotinamide adenine dinucleotide; NAD | vitamin)

        • not available in BAP; only in chocolate agar because RBCs must be lysed for V-factor to be available

          • must release NAD from RBC and inactive NADases (heat up)

      • identify Haemophilus through paper strips with hematin or NAD soaked within

        • put on Muller Hinton plate with pathogens, chemicals will diffuse; bacteria will only growth in the region where the pathogen requires which factor

        • Haemophilus parainfluenzae requires only V factor

        • if species name has para — indicates only V factor requirement

      • satellitism (tricky V factor production)

        • BAP with Staphylococcus aureus (lyses RBC & produces NAD) growing with Haemophilus streaked, it will grow where S. aureus is growing

          • growth in delayed before Staph produces NAD

        • one bacteria is producing something that is required of the other bacteria or one bacteria breaks down something to inhibit the growth of the other bacteria

  • Haemophilus influenzae

    • requires X and V factor

    • colony morphology

      • small, tanned, translucent, + capsule

        • if capsule the colonies will look mucoid / snotty looking; mucosy if picked up

        • no capsule, creamy & less mucoid

      • odor — mousy or bleach like

      • carriage in the nasopharynx, about 75% are healthy adults & children (no capsule)

      • has a bad reputation because it was mistakenly causes the influenza virus/flu due to epidemics of influenza flu

        • 1889-1890: people got the flu & were carriers; become immunocompromised due to flu, H. influenzae accquired as secondary infection travelling from upper to low resp tract

        • causes pneumonia & kills

        • in nasopharynx of those who died, the pathogen was found because it caused secondary infection

    • virulence factors

      • capsule — most significant factor because they block phagocytosis and promote invasiveness; six serotypes (a-f); most prevalent serotype is b

      • IgA protease — degrades sIgA which wards off pathogens that wish to live in the mucus membranes

      • fimbriae / outer membrane proteins that promote adhesion

      • modified LOS - lipooligosaccharide

        • lipid A is endotoxic part that causes endotoxic shock if dissemination occurs

    • invasive disease

      • transmission by direct contact w/respiratory secretion (no fomites)

        • acquired by carrier or ill person

          • moves from nasopharynx to lungs for endogenous infection

        • fastidious & picky; not tolerant to environmental conditions

      • found in unvaccinated (kids) pediatric population

        • mostly encapsulated bacteria; capsule required for dissemination

      • meningitis — dissemination & pathogen travels to meninges of brain and cerebral spinal column

      • pneumonia — nasopharynx to lungs

      • bacteremia — crosses nasopharyngeal epithelial and disseminates into the blood

      • epiglottitis (inflammation of epiglottis)

        • cartilage tissue that covers tracheae

        • infected & swells; blocks airway

        • requires tracheoscopy for proper breathing

    • non-invasive disease / localized

      • unencapsulated

      • assocaited with infection near the respiratory tract

      • otitis media — moves from nasopharynx through eustachian tubes into middle ear (secondary infection)

        • H. influenza is second most cause of inner ear infections

      • conjunctivitis — bacterial infection of the eye

    • lab ID

      • specimen sample typically upper or lower respiratory tract, ear exudate, CSF, blood

        • can do direct gram stains in some cases

      • might be able to see capsule (‘halo’)

      • cultured on chocolate agar only

        • would not grow on MAC or BAP

      • use Mueller Hurton plate growth between the strips

      • colony morphology — small, tanned, translucent, non-mucoid/mucoid; can smell like bleach

        • susceptible to drying out; should be plated with urgency

        • incubate at 35-37 degrees C & 5-10% CO2

          • human body temp

    • treatment & prevention

      • produce B-lactamases (breaks down B-lactam; resistant to penicillin)

      • for life-threatening diseases, use B-lactamase R B-lactam like cefotaxine or ceftriaxone

      • for localized use amoxicillin, usually combined with clavulanate (B-lactase inhibitor)

      • for prevention — vaccine that targets H. influenzae serotype b (Hib)

        • very effective! children get Hib vaccine series

        • in developing countries still an issue

      • between 1990 and 2000 number of serotype b cases dropped by 99.7%

  • Haemophilus aegypticus

    • common cause of bacterial conjunctivitis or pink eye (virulent discharge / pus in eye)

      • Koch ID in eyes of Egyptians who had the disease

    • lab ID - eye exudate

      • very picky!

      • when culturing, requires chocolate + IsoVital X (additional amino acids and growth factors)

      • slow growth observed, can take four days for bacteria to grow

        • 35-37 degrees C w/ CO2 5-10%

      • catalase positive

      • oxidase positive

      • gram negative coccobacillus

  • Haemophilus ducreyi

    • very picky

    • known for grouping of bacteria & some filament formation

      • schools of fish / railroad tracks

    • gram negative coccobacillus

    • culture on chocolate + IsovitalX

    • catalase negative

    • oxidase negative

    • colony morphology — small, flat, non-mucoid, opaque, tan to yellow color

    • found in mucosal epithelium, mostly genital

    • disease

      • a STD chancroid (GUD)

      • symptoms are painful ulcers on genitalia & enlarged inguinal lymph nodes

    • lab ID

      • swab from base of ulcer; plated to chocolate agar + IsoVitalX

        • does not grow on MAC or BAP

        • potential skin flora with swab so adding vancomycin will inhibit growth of normal genital flora

      • requires high humidity, 5-10 CO2, 33 degrees C

      • can take seven days for colony formation

    • treat with antibiotic erythromycin