Haemophilus, HACEK, etc.

Legionella, Bordetella, and other fastidious GN Bacilli

What does the acronym HACEK stand for?

• Haemophilus

• Aggregatibacter

• Cardiobacterium

• Eikenella

• Kingella

What makes the HACEK group unique?

• they are the only genera of gram negative fastidious bacilli that are associated with endocarditis

• slow growing

• enhanced with increased CO2 and humidity

Fastidious GN bacilli typically do NOT grow on what type of agar?

MacConkey

Key characteristics of Haemophilus:

oxidase and catalase POSITIVE

capnophilic

requires hemin (X) and NAD (V) for in vitro growth

"mousy" odor

GN coccobacilli

What 2 compounds are needed for Haemophilus to grow in vitro?

hemin (factor X) and NAD (factor V)

Haemophilus is normal microbiota of the __________________.

URT (the unencapsulated strains)

What species displays satellitism when plated with S. aureus on SBA?

Haemophilus

(grows around S. aureus because X factor is released due to lysis of red cells)

What methods are used for haemophilus identification?

ALA porphyrin test

• detects the organism’s ability to produce heme

Quad plates

biochemical

• fermentation, indole, urease

What is the ALA porphyrin test?

• a test that detects if an organism can produce heme

• disk method

  • a disk is moistened and inoculated with the organism

• tube method

  • organism is grown in a medium containing ALA, then Kovac’s reagent is added

• agar method

  • organism is streaked on a porphyrin test agar that contains ALA

• result interpretation

  • positive: red fluorescence in tube method, indicates porphyrin synthesis and the ability to grow without heme

  • negative: no fluorescence, organism requires heme for growth

How is H. influenzae transmitted and what types of infections is is associated with?

• direct contact with respiratory droplets from symptomatic or asymptomatic carriers

• meningitis, epiglottitis, bacteremia, ear infections, pneumonia.

Characteristics of the encapsulated strains of H. influenzae

• inhibits phagocytosis

• more pathogenic

• causes disease in infants, kids, and IC adults

H. influenzae has ___________ serotypes based on ___________antigen.

6; capsular (a, b, c, d, e, f)

lab characteristics of H. influenzae

• requires X and V factors

• nonhemolytic on HBA

• ALA negative

What species should be suspected if there is growth of GN coccobacilli on chocolate agar with no growth on SBA or MAC?

Haemophilus

What group of Haemophilus is responsible for "pink eye" and Brazilian purpuric fever?

H. aegyptius

Key characteristics of H. ducreyi:

STD

"school of fish" in direct genital gram stain

chancroid (ulcer) on the genitals

not a part of normal flora

What Haemophilus species may be confused with Group A Streptococcus?

H. hemolyticus (because it is B hemolytic on HBA)

What does HACEK stand for?

Haemophilus

Aggregatibacter

Cardiobacterium

Eikenella

Kingella

What are key characteristics of the HACEK group?

colonize the oropharynx

capnophilic

rare causes of ENDOCARDITIS

slow growth

Aggregatibacter aphrophilus and Aggregatibacter paraphrophilus

adheres to the walls of broth cultures

normal oral flora but can cause endocarditis, abscesses, and skin infection

on SBA, colonies are rough, pinpoint, and grow best in increased CO2

Cardiobacterium key characteristics:

alpha-hemolytic

catalase negative

may pit agar surface

C. hominis and C. valarum

What causes clenched fist wounds?

Eikenella corrodens

Key characteristics of Eikenella corrodens:

"corroding bacterium" =pits surface of the agar

requires hemin for growth

bleach like odor

human bite wounds, meningitis, and endocarditis

E. corrodens infections

• human bite wounds

• meningitis

• endocarditis

• clenched fist infections

• infections are often polymicrobic

Kingella genus

• short coccobacilli

• requires blood for growth, may pit the agar

• catalase negative

• normal URT flora

• may cause endocarditis or invasive infections in young kids

What organisms are an endogenous cause of periodontitis, endocarditis, and bacteremia in immunosuppressed patients?

Capnocytophaga gingivalis, Capnocytophaga hominis, Capnocytophaga sputigena

What genus demonstrates a fusiform shape on gram stain and a gliding motility on SBA?

Capnocytophaga

Legionella is found in and is transmitted by:

• found in natural and artificial water sources

• transmitted via inhalation of aerosolized water droplets, NOT person to person

Characteristics of Legionella:

aerobic

fastidious

narrow GNB

motile

gram stains poorly

Legionella pneumophilia causes what 2 disease states?

Legionnaire's disease

• acute pneumonia, bacteremia, fever, headache, diarrhea, and dry cough

Pontiac fever

What type of media is used to isolate L. pneumophilia?

BCYE=buffered charcoal yeast extract

How is L. pneumophilia detected in the lab?

• DFA (detects antigen in lung tissue or resp secretions)

• Legionella antigen testing

• PCR and MALDI-TOF MS

Bordetella characteristics:

aerobic

oxidative INTRACELLULAR GNB

binds to ciliated epi cells in the respiratory tract

Pertussis is transmitted by

person to person contact with respiratory droplets

Pertussis can last up to 12 weeks with what 3 stages?

Catarrhal

• 1-2 weeks, flu-like symptoms, highly contagious

Paroxysmal

• 1-6 weeks, lymphocytosis, coughing with a whoop

Convalescent

• 4-8 weeks, some coughing, secondary bacterial infections may occur

What is the isolation procedure for B. pertussis?

collect 2 nasopharyngeal swabs (Dacron swabs)

plate one on either Bordet Gengou or Regan-Lowe media

second swab used for DFA or PCR

What organism produces shiny mercury like colonies in 7-10 days on BG media?

B. pertussis

Virulence factors of B. pertussis

• fimbriae

• filamentous hemagglutinin

• pertussis toxin (induced lymphocytosis, inhibits chemotaxis and phagocytosis)

• adenylate cyclase

• tracheal cytotoxin

• dermonecrotic toxin

• endotoxin

What infection does Brucella cause? Who is most susceptible? What are the routes of infection?

• causes Brucellosis (Undulant Fever)

• dairy farmers, livestock handlers, and vets are most susceptible

• routes of infection

  • ingestion of contaminated milk or cheese

  • inhalation of aerosolized particles

  • penetration of oral mucosa or direct inoculation

Characteristics of Brucella

• small gram negative bacilli or coccobacilli

• stains poorly with gram stain

• strict aerobe

• nonsaccharolytic

• BSL 3 pathogen

isolation and ID of Brucella

• isolated from blood, BM, or other tissue

  • grows on blood or chocolate agar or Brucella agar with serum

• ID

  • serum agglutination test

What is the carrier of Pasteurella and what infections does it cause in humans?

• carried by

  • cats, dogs, rodents, birds, and rabbits

• human infection

  • Pasturellosis

    • wound infections following bites or scratches or respiratory infections following inhalation

  • meningitis, osteomyelitis, and joint infections

gram stain and lab ID of Pasturella

• gram stain

  • small gram negative bacilli with bipolar staining

• oxidase, catalase, and indole pos

• ferments glucose, sucrose, and mannose

• SBA isolation

  • mushroom smell, smooth, gray, nonhemolytic

Francisella tularensis

• associated with rabbits

• fastidious, small, nonmotile, pleomorphic GNB

• Tularemia

  • animal bites and scratches or ingestion of animal products

Streptobacillus moniliformis

rat bite fever and Haverhill fever

Bartonella species (2)

• B. henselae

  • cat scratch disease

• B. quintana

  • Bacillary angiomatosis, peliosis, trench fever