Haemophilus and Other Fastidious Flashcards
Pasteurellaceae (Pasteurella and Haemophilus)
- gram-negative coccobacilli
- non-motile, aerobic to facultative
- reduce nitrate to nitrite
- oxidase + and catalase +
- obligate parasites of mucous membranes
- require X and V factor
- grow on chocolate agar
- part of normal flora of upper respiratory tract
Haemophilus
Haemophilus means _______
blood loving
X factor
hemin (hematin)
V factor
nicotinamide-adenine dinucleotide (NAD)
only require V factor
para- Haemophilus species
Hemolysis on 5% horse or rabbit blood agar
- H. hemolyticus and H. ducreyi
- can’t use SBA because it doesn’t have V factor
Growth patterns
- satellitism around S. aureus (and species that release V factor)
- exceptions: H. aphrophilus and H. ducreyi
H. influenzae
- often a secondary infection (was in a pandemic)
- can test for beta-lactamase
H. influenzae (virulence factors)
- capsule (A-F types)
- IgA protease
- outer membrane proteins and lipopolysaccharide (LPS)
- adherence (pili)
H. influenzae capsule
- antiphagocytic molecules (ribose, ribitol, and phosphate)
- nontypable strains cause localized infections (pneumonia, otitis media, sinusitis)
Haemophilus influenzae serotype b (Hib)
- primarily in children
- bacteremia can spread to tissues
- # 1 cause of meningitis in unvaccinated children
Clinical disease of Hib
- meningitis (children under 6)
- epiglottitis (can cause airway obstruction)
- bacterial tracheitis
- cellulitis, pharyngitis, pneumonia
Non-encapsulated H. influenzae (diseases)
otitis media, bronchitis, sinusitis, pneumonia
H. aegyptius is the causative agent of _________
pinkeye (conjunctivitis)
H. aegyptius (clinical infections)
- conjunctivitis
- Brazilian purpuric fever (BPF): has a high mortality rate
H. ducreyi
- sexually transmitted infection
- chancroid (soft chancre)
- incubation up to 14 days
- painful legion, enlarged lymph nodes, buboes
H. parainfluenzae (clinical infections)
endocarditis
H. aphrophilus/Aggregatibacter aphrophilus (clinical infections)
bite wound infections, endocarditis
Culturing Haemophilus
- must plate immediately, they die rapidly
- BAP for those that don’t require V factor
- DON’T GROW ON MAC
- transluscent, moist, smooth colonies
Culturing H. influenzae
chocolate agar with bacitracin (to inhibit other respiratory flora)
Culturing H. ducreyi
- extremely fastidious (7 days to grow)
- “school of fish” morphology on gram stain
Lab ID of Haemophilus
- place colonies in nutrient broth, then streak Mueller-Hinton agar plate, use X and V strips and incubate
- Quad plate to ID factors needed (X, V, X & V, horse blood)
Porphyrin test
- differentiates species that require X factor
- Positive: organism converts delta-aminolevulinic acid to porphyrin (intermediate of X factor)
- positive result means organism doesn’t need X factor
- positive result on Wood lamp fluoresces
H. influenzae negative identification
- from respiratory or CSF specimen
- gram-neg. bacilli that have colonies >1mm on chocolate
- no growth on SBA, except satellitism
- negative porphyrin
Haemophilus that require both X and V factors
H. influenzae, H. ageyptius, H. hemolyticus
Haemophilus that requires only X factor
H. ducreyi
HACEK
- Haemophilus (Aggregatibacter aphrophilus)
- Actinobacillus/Aggregatibacter actinomycetemcomitans
- Cardiobacterium hominis
- Eikenella corrodens
- Kingella species
HACEK (general characteristics)
- none grow on Mac
- requires CO2 for growth
- usual flora of oral cavity (human bite wounds)
- significant cause of endocarditis
- requires V factor
- associated with dental plaque
A. aphrophilus
- animal pathogen usually; gram-negative coccobacilli
- distinctive star in center of colony
- normal oral flora (causes peridontitis)
- catalase +, oxidase variable
- urease, indole, esculin, citrate -
Aggregatibacter actinomycetemcomitans
- non-motile, sometimes gram variable
- “rosette” morphology
- normal flora of nose, mouth and throat
- may cause pitting on agar plates
Cardiobacterium hominis
Cardiobacterium hominis
- infects aortic valve
- causes endocarditis
- capnophilic, requires X factor
- bleach-like odor
- pitting in the agar
- no growth on Mac or EMB
Eikenella corrodens
Eikenella (clinical infections)
- “clenched fist” bacteria (human bite/fight wounds)
- pneumonia, meningitis, osteomyelitis, arthritis
- cellulitis (when needles are licked clean - drug users)
- endocarditis (least of HACEK group)
- non-motile, but may twitch
- oxidase +, catalase -
- found in upper respiratory tract
Kingella species
Kingella kingae
- grows on MTM, resembles gonhorrea
- may pit on agar
- catalase -, oxidase -
- affects bones and joints of children
Kingella dentrificans
- catalase -, superoxol -
- differentiates it from Neisseria
Capnocytophaga
- resemble HACEK
- gram-negative, fusiform, capnophilic
- have gliding motility
- dental problems, septicemia (if gets into blood)
Pasteurella multocida
- five serogroups (A-F)
- bipolar staining (safety-pin appearance)
- grow on BAP and Chocolate, no growth on MAC
- zoonosis (dog or cat bites/scratches)
- non-motile, catalase +, oxidase +
- weak acid production
Brucella
- strict aerobes, non-spore forming, non-encapsulated
- fine sand morphology (Brucella melitensis)
- oxidase +, catalase +, H2S production, UREASE +
- blood and bone marrow specimens typically
Brucella (clinical infections)
- Brucellosis and UNDULANT FEVER (long infection)
- systemic infection with multi-organ involvement
- zoonotic (animal contact, animal products)
- infection via penetration of ocular or oral mucosa
- lab-acquired infection
undulant fever
fever recurring at regular intervals
Francisella
- require CYSTEINE for growth, grow on CAP, MTM, BCYE
- strict aerobes, don’t grow on MAC, SBA
- zoonotic infections
- category A select agent
organism that cause zoonotic infection
Pasteurella multocida, Brucella, Francisella
F. tularensis
- type A
- transmitted by rabbits, sheep, ticks
- rabbit fever
- tularemia
Other Francisella species
F. holarctica (type B), F. mediasiatica, F. novocida
Legionella
- acquired through inhalation (not zoonotic)
- isolation on special media, identified by serologic testing
- community-acquried pneumonia, nosocomial infections
- environmental water sources, air conditioning systems
L. pneumophilia
- primary Legionella pathogen (16 serogroups)
- virulence: ability to invade and survive in macrophages
- results from inhalation of aerosols (not person-to-person)
- Legionnaires’ disease
- Pontiac fever
Legionnaires’ disease
- epidemic outbreaks usually from air conditioners
- nosocomial infections (respiratory equipment and aerosol)
- community-acquired pneumonia
- cough, fever, headache, myalgia, dissemination via circulatory system
- can have high mortality rate; hard to ID
Pontiac fever
- inhalation of Legionella
- no pulmonary involvement
- mild form of Legionnaires disease
Legionella sources
- aquatic sources
- air conditioning systems
- survive at large range of temps
- adherence to pipes, rubber, plastics
- can live intracellularly in protozoa
Legionella specimens
predominantly respiratory specimens
Legionella (characteristics)
- difficult to ID
- thin, weakly staining gram-negative rods; small colonies
- blue-green colonies, ground-glass look
- found within macrophages and neutrophils
- aerobic, require Cysteine for growth
- grow well on BCYE
Bordetella (major pathogens)
Bordetella pertussis and Bordetella parapertussis
Bordetella (minor pathogen)
Bordetella bronchiseptica - opportunistic, pneumonia and wound infections
Bordetella (virulence)
Pertussis toxin - interferes with signal transduction
Bordetella (infection)
- acquired from breathing in aerosols (adheres to cells)
- highly contagious, vaccine available
- causes Whooping cough
Whooping cough
- presents with flu-like symptoms
- highly contagious
- severe repetitious coughing
- can be followed by vomitting
- serious in young children
- causes hypoxia
Culturing Bordetella
- specimens from nasopharynx
- MUST USE calcium alginate or Dacron swab
- use Regan-Lowe transport medium or Bordet-Gengou potato infusion agar
- incubates for 7 days
Bordetella (characteristics)
- gram-negative rod
- obligate aerobe
- smooth silver pinpoint colonies resembling mercury droplets
