Special Pathogens

Question 1

Pseudomonas Clinical Significance

Answer 1

• Illness
  
  • UTI
  • Septicemia - [hematologic disorders]
  • Respiratory disease – [CF patients]
  • Now COPD (4th leading cause of death in US)
  • Wounds/sepsis – [thermal injuries]
  • Pulmonary disease – [intubation, immunocompromised]
  • Osteomyelitis – [heroin addicts, long-term iv therapy, previous surgery]
• Sources
  
  • Sinks, traps
  • Soaps, solutions
  • Water faucets, aerators
  • Inhalation equipment
  • Catheters
  • Sponges, mops
  • Hospital food
  • Flowers
  • Personnel: hands
  • Antiseptic creams
  • Iodine solutions
  • Ophthalmic solutions

Question 2

Pseudomonas ID

Answer 2

• Produces a grape-like or tortilla odor on BAP
• Elaborates strong β-hemolysin
• Produces many different pigments:
• Pyocyanin (blue)
• Pyoverdin (yellow)
• Pyorubin (red, brown)
• Produces many different colony types on BAP or common basal media:
• Classic or typical
• Rough or rugose
• Coliform-like
• Mucoid
• Dwarf
• P. Aeruginosa only produces pyocyanin a way to separate
• Biochem
  
  • Indole -
  • Glucose, OFBM +
  • Fructose, Xylose, Mannitol +
  • Lactose, Sucrose, Maltose -
  • H2S-
  • Urease +
  • ADH +
  • ODC, LDC -
  • ONPG -
  • Lipase, gelatinase +
  • DNase -
  • K/NC-
  • oxidizer

Question 3

Pseudomonas Species ID

Answer 3

• Ps. stutzeri
  
  • Maltose +
  • ADH -
• Ps. mendocina
  
  • Maltose -
  • ADH +

Question 4

Acinetobacter Clinical Significance

Answer 4

• Illnesses
  
  • Pneumonia
  • Bloodstream infections
  • Wounds
  • UTI
  • Meningitis
• Risk Factors
  
  • Prolonged stay in ICU
  • Prior antibiotic exposure
  • Mechanical ventilation
  • Use of a CVC (Central Venous Catheter)
  • Hemodialysis
  • Medical treatment practices
  • Indwelling devices
  • Hydrotherapy (burns)
  • Exposure to contaminated medical equipment
• Ac. baumannii – Pneumonia
• Ac. baumannii - Septicemia

Question 5

Acinetobacter ID

Answer 5

• Characteristic
  
  • Smooth, sometimes mucoid, grayish white colonies
  • Non-pigmented; some strains produce a “fish-like” odor
  • Ac baumannii cplx grows well on common laboratory media @ 37°C
  • Other species produce translucent colonies; growth variable on media
  • Biochemically a unique organism not easily confused with other NFGNR
  • Can be extremely pleomorphic and not presenting as a gram-negative rod
  • Sometimes appears as cocci
  • Can stain Gram-variable
• Reactions
• Oxidase
  
  • -
• Indole
  
  • -
• Motility
  
  • -
• Glucose
  
  • V
• Lactose, Xylose
  
  • V
• Mannitol, Sucrose
  
  • -
• Urease
  
  • V
• Nitrate reduction
  
  • -
• LDC, ODC, ADH,
  
  • -
• ONPG
  
  • -
• DNase
  
  • -

Question 6

Acinetobacter Species ID

Answer 6

• Trait for Ac. baumannii Cplx from Other
  
  • ​Other Grps
• Growth at 41°C
  
  • +
    
    • -
• Gelatinase
• -
  
  • V
• Hemolysin
• -
  
  • V
• Glucose, acid
• +
  
  • V
• L-phenylalanine
• +
  
  • -
• trans-Aconitate
• +
  
  • -
• Suscp: Pen, Chl
• -
  
  • V

Question 7

Oxidative-Fermentative (OF) test

Answer 7

• Increased acid detection over broth media
• semisolid agar (0.2 – 0.3%), enhances acid visualization
• Basal medium contains 1% CHO, 0.2% peptone (1:5 ratio)
• low peptone, decreases oxidative products from a.a. that may neutralize acids
• increased carbohydrate = increase acid

Question 8

Hugh-Leifson (OF Difco MDL)

Answer 8

• bromothymol blue
• yellow = acid
• blue = alkaline

Question 9

King’s OF

Answer 9

• phenol red
• yellow = acid
• red = alkaline

Question 10

Yersinia Clinical Significance

Answer 10

• Pneumonic plague
• Bubonic plague
• Septicemic plague

Question 11

Yersinia ID

Answer 11

• Characteristics
  
  • “Large” Gram negative rod
  • Safety Pin Gram stain
  • fried egg on SBA
  • Will grow on routine culture media SBA, CHOC, and MAC
  • Resembles other Enterobacteriaceae EXCEPT grows faster at 25 o C or RT than at 37 o C
• KEY BIOCHEMS
  
  • Oxidase NEG
  • Urease NEG
  • Indole Neg
  • Catalase POS
  • Non Lactose fermenter on MAC

Question 12

Francisella tularemia Clinical Significance

Answer 12

• “Rabbit Fever” & “Deer fly
• F. tularensis : causative agent of tularemia, acute & fatal illness in animals & humans
• HIGHLY infectious (10 organisms can cause disease!)
• Notorious reputation for lab acquired infections
• Human infections caused by:
  
  • Arthropod bite
  • Handling infected animals
  • Inhalation of infectious aerosols
• Ingestion of contaminated food or water
• Tularemia symptoms depend on virulence of bacterial strain & route of infection.
• Symptoms of all forms of tularemia typically include fever, headache, body aches, and malaise.
• Symptoms usually develop within 3 to 5 days of infection
• Incubation period can be 1 14 days.

Question 13

Francisella tularemia ID

Answer 13

• Very tiny Gram-negative coccobacilli (counterstain poorly - safranin)
• Strict aerobes
• Weakly catalase +
• Urease –
• Oxidase -
• Non-motile
• Non-spore forming
• Metabolize limited number of sugars (acid produced w/o gas)
• Glucose, maltose, sucrose, glycerol
• Unique cellular fatty acids
• In vitro growth enhanced by cysteine supplementation
• A few key differences separate species
  
  • Oxidase, growth in NB w 6% NaCl , optimum growth temps, sugar
    utilization, virulence

Question 14

Stenotrophomonas maltophilia Clinical Significance

Answer 14

• Illnesses
  
  • Septicemia
  • Respiratory tract
  • Urinary tract
  • Skin and soft tissue
  • Bone and joint
  • Endocarditis
  • Meningitis
  • Gastrointestinal
• Risk Factors
  
  • Neutropenia or cytotoxic chemotherapy
  • Presence of a central venous catheter (CVC)
  • Prolonged hospitalization; admission to ICU
  • Mechanical ventilation or tracheotomy
  • Previous exposure broad-spectrum antibiotics
• Extremely resistant bacteria to antimicrobials

Question 15

S. maltophilia ID

Answer 15

• Laboratory Characteristics
  
  • Colonies develop a lavender-green color on BAP
  • Produces a brown – tan pigment
  • Growth on BAP accompanied by strong odor of ammonia
  • Grows on most common media: MacConkey
  • Biochemically a unique organism not easily confused with other NFGNR
• Reaction
  
  • Oxidase
  • -
  • Indole
  • -
  • Glucose, Fructose, Lactose, Maltose
  • +
  • Mannitol
  • -
  • H₂S, urease
  • -
  • LDC
  • +
  • ODC, ADH
  • -
  • ONPG
  • +
  • Lipase, gelatinase
  • +
  • DNase
  • +

Question 16

Elizabethkingia Clinical Significance

Answer 16

• E. meningoseptica (Chryseobacterium meningosepticum)
  
  • neonatal meningitis
  • neonatal septicemia
• Elizabethkingia miricola
  
  • septicemia
• Elizabethkingia anophelis
  *

Question 17

Elizabethkingia ID

Answer 17

• General Properties
  
  • Gram-negative aerobic rods
  • Non-motile
  • Growth range 28 - 37°C
  • Catalase and oxidase-positive
  • Casein, esculin, and gelatin are hydrolyzed
• E. anophelis
  
  • Gram-negative aerobic non-fermentative rods
  • Some strains exhibit slight yellow pigmentation
  • Non-motile
  • Biochemicals:
  • Oxidase +
  • Catalase +
  • Indole +
  • Cannot be biochemically separated from E. meningoseptica

Question 18

BRUCELLA Significance

Answer 18

• Major human pathogens
  
  • B. abortus (cattle, cow, bison)
  • B. canis ( Dog)
  • B. melitensis (goat and sheep)
  • B. suis ( Swine)
• Other Brucella species
  
  • B. neotomae (wood rat)
  • B. ovis ( Ram)
  • “B. maris ” (marine animals), “B. pinipediaepinipediae”, “ B. cetaceae ”
• Clinical Syndromes
• Systemic
• CardioCardio-vascular
• Cutaneous
• GastroGastro-intestinal
• Neurological
• OsteoOsteo-articular
• Reproductive
• Respiratory
• Acute
  
  • Fever, malaise, headache, anorexia, arthralgia, myalgia , and back pain
  • Within 1 to 4 weeks after exposure
• Subchronic (undulant)
  
  • Low temperature in morning followed by rising
  • temps in the afternoon and evening
  • Within 1 year after exposure
  • Arthritis and epididymoorchitis may occur
• Chronic
  
  • Depression, arthritis, and chronic fatigue syndrome
  • Around 1 year after exposure
• Transmission
  ◦ Direct contact thru broken skin, eyes
  ◦ Inhalation
  ◦ Ingestion
  ◦ Approximately 2% of all reported cases are acquired
  in the laboratory (chances of acquiring from lab
  exposure varies 30 30-100% and depends on various
  factors)

Question 19

Brucella ID

Answer 19

• Characteristics
  
  • Strict aerobes (oxidizers), some require CO 2
  • Grows on SBA and CHOC, do not grow on MAC or EMB
  • Smooth, raised, non-hemolytic, and translucent colonies
  • Nonspore
  • Nonspore-forming, gram gram-negative coccobacilli
  • Nonmotile, non-encapsulated, intracellular pathogens (can reside in mononuclear phagocytic cells)
  • Gram -
  • Intracellular
  • Nutritionally fastidious
  • -Very slow grower (plates should be beheld for 4 days before reported negative)
  • coccobacillus
  • faintly staining
  • small
• Biochemical tests
  
  • Oxidase—positive
  • Catalase—positive
  • Nitrate reduction reduction-positive
  • Urease—positive within 2 hours
  • Hydrogen sulfide (H H2S) production
  • X and V factor testing maybe helpful in ID (negative for X and V
  • Serologic testing preferred along with history and disease status to diagnose brucellosis.

Question 20

*Burkholderia spp.
Mellioidosis/ Glanders*

Significance

Answer 20

• Major respiratory pathogen in cystic fibrosis patients (B. cepacia complex)
• CDC Category B potential bioterrorism agents (B. mallei, B. pseudomallei)
• Respiratory disease - CF patients
• Septicemia
• Soft tissue infections
• Ocular infections
• Infection with BCC often occurs after lengthy colonization with
  Ps. aeruginosa

Question 21

Burkholderia mallei

Answer 21

• Glanders is an infectious disease that is caused by the bacterium Burkholderia mallei. Glanders is primarily a disease affecting horses, but it also affects donkeys and mules and can be naturally contracted by goats, dogs, and cats.
• Direct skin or mucous membrane contact with infected animal
  tissues
  • Inhalation of infectious aerosols – laboratory-acquired infection
  • The incubation period = 1 to 14 days
  • Occupational Infections
  • Individuals who work with horses, mules, donkeys
  • Laboratory workers
• • Often manifests as:
  • pneumonia,
  • bronchopneumonia
  • Lobar pneumonia with or without bacteremia

Question 22

Burkholderia – Laboratory

Characteristics

Answer 22

• Smooth and convex in early growth, with some species
• developing umbonate wrinkled colonies with age
• Pigmentation varies ranging from non-pigmented species
• (mallei) to noted yellow pigmentation in others (cepacia, gladioli)
• Burkholderia grows well on BAP or MacConkey agars; variable to
• no growth on SS and cetrimide
  *

Question 23

B. cepacia & B. gladoioli: Biochemical

Properties

Answer 23

Question 24

B. pseudomallei Technical
Clues

Answer 24

• Gram-negative aerobic rods
• Characteristic slow to moderate growth on SBA and MAC
• Oxidase positive
• Motile
• Catalase positive

Question 25

B. mallei Technical Clues

Answer 25

• • Gram-negative coccobacilli
• • Characteristic very slow growth on SBA and little if any growth
• MAC
• • Oxidase variable
• • Non-motile
• • Catalase positive

Question 26

Bordetella pertussis ID

Answer 26

• B. pertussis is small GNCB
• B. parapertussis and B. bronchiseptica are more rod shaped
• Bordetella species do not gram stain well
• Safranin counterstain should be extended for better visualization
• Bordet-Gengou (BG) is a potato-based agar with sheep blood and glycerol
• Starch neutralizes toxic materials present in specimen
• Does not contain peptones because these may be inhibitory
• Cephalexin, methicillin, or oxacillin may be added for selectivity
• oShelf life 5 days
• Regan-Lowe media contains charcoal and horse blood
• Available as semisolid transport/enrichment media and solid media
• for isolation
• May contain cephalexin and/or amphotericin B for selectivity
• Shelf life 4-8 weeks

Question 27

Bordetella pertussis Significance

Answer 27

• Whooping cough
• Respiratory infection characterized by paroxysmal cough, posttussive vomiting, and inspiratory whoop
• Incubation period: 7-10 days; range 5-28
• 3 stages of disease
• 1.Catarrhal: nonspecific cold symptoms (1-2 weeks)
• 2.Paroxysmal: severe coughing spells that end in an inspiratory whoop (2-6 weeks)
• 3.Convalescent: decreasing frequency of coughs, though viral infections can trigger paroxysms (1-12 weeks)
• Cough may last more than 10 weeks
• Complications include pneumonia, rib fractures, incontinence, syncope

Question 28

Haemophilus ID

Answer 28

• Small GNRs or coccobacilli, pleomorphic, X factor independent spp. appear as long filaments
• Facultative anaerobes
• Non motile and non spore formers
• Oxidase positive (in contrast to Enterobacteriaceae
• Catalase and nitrate positive
• All require preformed growth factors found in blood
• X factor heme/hemin (protoporphyrin IX) or
• V factor NAD or NADP or
• X and V both
• With the exception of H. ducreyi and H. aphrophilus,
• all need V factor
• On BAP grow as satellite colonies around S. aureus
• β-hemolytic on horse, bovine or rabbit blood but
• NOT on she
• ep blood (H. hemolyticus, H.
• parahemolyticus and H. pittmaniae)
• Growth produces pungent or “mouse-nest” smell
• Increased CO2 (5-10%)
• Capsule Virulence factor
  
  • Serotypes a-f
• Haemophilus influenzae serotype b (Hib)

Question 29

Haemophilis General Characteristics

Answer 29

• H. influenzae type b (meningitis, cellulitis
• epiglottitis, pneumonia, septic arthritis)
• H. aegyptius (Koch-Weeks bacillus, pink eye)
• H. influenzae biotype aegyptius (Brazilian purpuric fever)
• H. parainfluenzae (endogenous)
• H ducreyi (chancroid)
• H. aphrophilus (HACEK, endocarditis)
• Haemophilus – Blood loving
  
  • Require X and V factors found in blood X factor is hemin, hematin
  • V factor is nicotinamide-adenine dinucleotide (NAD)
• All para species – require only V factor
  
  • Haemophilus parainfluenzae
  • Produces X factor, requires V factor
• H. aegyptius causes conjunctivitis

Question 30

Virulence Factors:
H. influenzae

Answer 30

• Capsule
• Serotypes a a-f
• IgA protease
• Cleaves IgA on mucous membranes
• Outer membrane proteins and lipopolysaccharide ( Not well defined
• Antibody to these proteins is somewhat protective
• LPS paralyzes the cilia
• Can’t clear the lungs
• Adherence
• Pili and other structures

Question 31

Legionella General Characteristics

Answer 31

• Legionnaire’s Disease
  
  • Route of infection: aerosol
  • Symptoms: Cough, shortness of breath, fever, muscle aches, headaches
  • Onset: 2 -10 days post- exposure
  • Disease: Pneumonia
  • Isolation of agent: Possible
  • Outcome: 5% - 40% mortality
• Pontiac Fever
  
  • Route of infection: aerosol
  • Symptoms: Fever, muscle aches
  • Onset: 24 – 72 h post-exposure
  • Disease: Flu-like illness
• Pathogenicity Factors
  
  • Biofilms
  • Replication within host phagocytic cells
  • Others: iron acquisition, cytotoxins
• Monoclonal subtyping of L. pneumophila
• serogroup 1
• MLST – flaA, pilE, asd, mip, mompS, proA genes
• AFLP

Question 32

Legionella ID

Answer 32

• Motile, gram-negative rods
• Asaccharolytic, amino acids used as energy source
• Obligate aerobe
• Nutritionally fastidious, L-cysteine dependent
• Optimal growth @ 35
• Growth enhanced by iron, humidity
• If you pretreat sample, use low pH KCL-HCL buffer, 4 mins, at room temperature or heat at 50°C for 30 mins
• Use selective and non-selective media:
• VAP or BMPA
• BCYEα
• Incubate at 35°C, humidity, CO2
• (2-5%)
• Read days 1-5 and day 14

Question 33

Moraxella catarrhalis General Characteristics

Answer 33

• Causes acute, localized infections such as otitis media, sinusitis, and bronchopneumonia
• Causes a large amount of lower RT infections in elderly patients with COPD

Question 34

Moraxella catarrhalis ID

Answer 34

• Cultured on blood and chocolate agar
• White/grey colonies, waxy surface
• Hockey puck test – able to push the colony across the plate
• Specimen types include: inner ear fluid, sputum, and blood
• Key
  
  • Not able to ferment glucose, sucrose, maltose, and lactose
  • Positive DNase
  • Oxidase Positive
  • Nitrate Positive
• M. catarrhalis is often mistaken for N.catarrhalis
• M.catarrhalis strains can tolerate lower temperatures and will grow well at 28˚C

Question 35

GENUS NEISSERIA ID

Answer 35

• GN coccal or diplococci, aerobic, non-motile
• Growth optimal at 35° with humidity, CO, stimulates growth or maybe obligate for initial isolation
• Oxidase positive
• Difficult to separate. Usually ID as “Nesseria species” unless isolated from systemic source or pure culture
• Choc or BA if sample sterile
• Modified Thayer-Martin if non sterile sample

Question 36

Neisseria General Characteristics

Answer 36

• Neisseria Gonorrhea
• Neisseria Menigiditis

Question 37

Bacillus Anthracis General Characteristics

Answer 37

• Colony on SBA at 35°C, 18-24hr
• Flat or slightly raised, grey to white
• Undulate edge may show curling resembling a “Medusa head”
• Surface has “ground glass” appearance
• “Tenacious” or “sticky”
• Non-hemolytic
• Large Gram-positive rod
• Usually non-encapsulated, often in long chains
• Cells are more easily decolorized with age
• Oval spores, central to sub-terminal, with no swelling of cell
• Rapidly growing, flat, “ground-glass” colonies on SBA
• Large Gram-positive, aerobic rods
• Non-hemolytic
• Non-motile
• (Catalase positive)

Question 38

Bacillus ID

Question 39

Bacillus Anthracis Diseases

Answer 39

• Inhalation
• Gastrointestinal
• Cutaneous

Question 40

Listeria monocytogenes General Characteristics

Answer 40

• 32% Neonatal sepsis and meningitis
• 31% Febrile gastroenteritis
• 26% Sepsis in compromised hosts
• Motility described as tumbling end over end is viewed microscopically in a hanging drop preparation and umbrella like when viewed in tube cultures grown at room temperature
• Facultative anaerobes
• Optimum growth temperature
• 30-37°C
• Can grow at 4°C

Question 41

Listeria Monocytogenes ID

Answer 41

• Gram positive, nonsporeforming, short rods
• Rod shaped seen individually or in short chains or may appear as coccobacilli
• Difficult to stain and may even appear as gram-negative
• Motile at 28C by peritrichous flagella, not very motile at 37C
• Buffered Listeria Enrichment Broth
• Supplements
• Nalidixic acid: inhibits Gram negative spp.
• Does not ininhibit Pseudomonas or Proteus spp.
• Acriflavine: inhibits many other Gram (+) bacteria, parasites, and fungi
• Cycloheximide: inhibits yeasts and molds
• Very toxic
• Can be substituted by pimaricin (a.k.a. matamycin)
• Umbrella Motility
• Although all are considered to be potentially virulent, serovars 4b, 1/2b, and 1/2a account for 96% of human disease.

Question 42

Corynebacterium General Characteristics

Answer 42

• For C. diphtherias to cause diphtheria an exotoxin must be produced.
• It is a heat-labile polypeptide produced during lysogeny of a β phage that carries the “tox” gene.
• Alkaline pH of 7.8- 8.0, aerobic conditions, and a low
• environmental iron level are essential for toxin production
• (occurs late in the growth of the organism).
• The toxin inhibits protein synthesis
• C. ulcerans toxigenic strains may produce a disease
• similar to, but less severe than diphtheria.
• J-K Group commonly cause infections in those with
• underlying disease.
• Diseases include bacteremia, meningitis, peritonitis, wound
• infections, etc.
• It is becoming more and more of a problem.
• C. pseudotuberculosis found in those with exposure to
• animals.
• Can cause pneumonia or lymphadenitis.
• Produces a different exotoxin than C. diphtheriae.

Question 43

Corynebacterium ID

Answer 43

• Gram positive rods
• Catalase positive
• Non-acid fast
• Non-spore forming
• Aerobic or facultative anaerobic
• Fastidious
• Corynebacterium diphtheriae and diphtheroids (look like C. diphtheriae) are Gram positive club shaped rods.
• Loeffler‘s agar slant contains serum and
  egg that enhance the formation of metachromatic granules (polymerized polyphosphoric acid) in C. diphtheriae. Also called Babes-Ernst granules.
  They are visualized by staining with methylene blue.
• A medium containing tellurite should be used to select for Corynebacterium and other gram positive organisms while it inhibits gram negative organisms. Two kinds are used: Cystine tellurite which has a longer shelf life.
• Elek plate: To prove that an isolate can cause
  diphtheria, one must
  demonstrate toxin production.
• Tinsdale medium helps to differentiate amongst the Corynebacterium. Colonies on either appear black or gray due to tellurite reduction.
• 3 morphological types of C. diphtheriae are found on tellurite containing media:
  
  • Mitis – black colonies with a gray periphery
  • Gravis – large, gray colonies
  • Intermedius – small, dull gray to black.
• All produce an immunologically identical toxin.
• Incubation -35-370 C for 24 hours.
• They prefer a pH of 7.8-8.0 for good growth.
• They require access to oxygen (poor AnO2 growth).
• Biochemistry
• Catalase +
• Non-motile
• C. ulcerans is urease + vs C. dphtheriae which is -; C. pseudotuberculosis is usually +

Question 44

Pasteurella sp

Answer 44

• Gram-negative coccobacilli or rods; bipolar staining
• Nonmotile; Facultatively anaerobic
• related to Actinobacter and Haemophilus
• Exist in the upper respiratory and GI tract of cats, dogs, domesticated and wild animals
• Species of importance : P. multocida, P.haemolytica, P.
• pneumotropica, P.ureae
• Pasteurella multocida: causative agent in human infection

Question 45

Pasteurella Medical Significance

Answer 45

• Zoonosis, virulent to animals and birds
• Fowl Cholera in Poultry
• Atrophic rhinitis in Pigs
• Shipping fever
• Bovine hemorrhagic septicemia
• human infections
• Local abscess
• Meningitis
• RT infections
• Animal Bites

Question 46

Pasteurella ID

Answer 46

• Specimens
• Swabs from bite wounds
• CSF in case of meningitis
• Secretions or sputum in case of RT infections
• Culture
• Blood agar
• Chocolate agar
• Microscopy Gram staining reveals GNCB
• Identification
• Cultural and Biochemical tests
• Catalase, oxidase +
• Indole +
• Urease -
• ODC +
• Growth on MacConkey -
• Acid from sucrose, mannitol +

Question 47

*The Genus
Capnocytophaga*

Answer 47

• Thin to slender gram-negative bacilli
• Tapered ends
• Cytochrome oxidase-variable; gliding motility
• “Capnocytophaga” [eater of CO2]
• Found as oropharyngeal flora in humans and other primates
• Pathogenic for humans
• rRNA superfamily V (“Cytophaga – Flavobacterium - Bacteroides” group

Question 48

Capnocytophaga medical significance

Answer 48

• Risk Factors (all)
• Dog ownership or contact
• Snoggling
• Underlying disease
• Asplenia
• Physician Awareness
• Patient Awareness
• Laboratory ID
• Conventional methods: SLOW

Question 49

Streptobacillus moniliformis General Characteristics

Answer 49

• Pleomorphic, facultatively anaerobic, gram-negative bacterium
• Causes two diseases
• Haverhill fever (rare)
• Associated with consumption of contaminated milk, water
• High incidence of pharyngitis with vomiting
• Rat-bite fever (common)
• Abrupt onset of high fever, headaches, arthralgia
• Rashes develop over extremities (palms, soles)
• Diagnosis is dependent upon:
• A good medical history (rat or animal exposure)
• Using optimal culture conditions to recover bacteria from blood, aspirates, or wounds

Question 50

S. moniliformis – Laboratory Identification

Answer 50

• Requires 10% - 20% serum for growth
• GNB in chains, filaments, sometimes with bulbous swellings
• Growth in thioglycollate broth producing “puff balls”
• Positive DFA test with polyclonal ab to S. moniliformis
• Rapid ID:
• PCR/ESI – MS
• 16S rRNA

​

Question 51

Erysipelothrix rhusiopathiae General Characteristics

Answer 51

• ‘Erysipelas’ [a disease] and ‘thrix’ [a hair or thread]; ‘rhusius’ [reddish] and ‘pathus’ [disease]: ‘erysipelas thread of red disease’
• Gram-positive rods [can decolorize easily]
• Slender rods with rounded ends; can form long filaments, short chains or in pairs in a “V” formation
• Non-motile
• Oxidase and catalase-negative
• Ecologic habitat: marine fish, molluscs, birds, and farm animals incl. swine, sheep, cattle, and horses
• Member of the Fimicutes, family Erysipelothricaceae

Question 52

E. rhusiopathiae Infections

Answer 52

• Causes three major syndromes:
• Erysipeloid (cutaneous form) resembling cellulitis
• Usually on hands or fingers
• Well-defined lesion, slightly raised, violaceous zone
• Diffuse cutaneous form
• More generalized than cutaneous; bullae may form
• Fever common plus joint pain
• Blood cultures are often negative
• Septicemia w/wo endocarditis

Question 53

*E. rhusiopathiae –
Laboratory ID*

Answer 53

• Facultatively anaerobic
• On TSA, colonies are very small after 24-48h incubation
• Can produce α-hemolysis on BAP
• Produces H2S on TSI
• “Test tube brush” growth in gelatin stab [no gelatinase]
• Most often confused with Listeria

Question 54

Streptococcus Iniae Significance

Answer 54

• Cellulitis
• Endocarditis, meningitis, arthritis
• aquaculture in south east asia

Question 55

S. iniae – Laboratory Identification

Answer 55

• Gram-positive, β-hemolytic
• Non-motile cocci
• PYR, CAMP, ADH, and Esc+
• Often mis-ID by conventional/rapid systems
• Rapid ID:
• 16S rRNA
• Cpn60

Question 56

HACEK

Answer 56

• Fastidious, Gram-negative bacilli
• • Require an increased CO2 (5%-10%) environment
• • Indigenous to the oral cavity / upper respiratory tract
• • Opportunists in immunocompromised hosts

Question 57

Aggregatibacter aphrophilus

Answer 57

• Capnophilic, fermentative, non-motile, gram-negative coccobacillus
• • Some strains require “V” factor (NAD)
• • Oxidase-negative, catalase-negative
• • Acid produced from: glucose, maltose, sucrose, lactose, and trehalose
• • ONPG-positive
• • ADH, LDC, and ODC-negative; urea-negative

Question 58

Aggregatibacter actinomycecomitans

Answer 58

• Capnophilic, gram-negative, non-motile coccobacilli
• • Fermentative, fails to grow on MacConkey or enteric media
• • Oxidase-negative, catalase-positive
• • Does not require “X” or “V” factor for growth
• • ONPG-negative
• • ODC, LDC, and ADH-negative; urea-negative

Question 59

Cardiobacterium hominis

Answer 59

• Capnophilic (5%-7% CO2), gram-negative but can be gram-variable; non-motile
• • Highly pleomorphic, cells may appear swollen with a tteardrop, dumbbell and lollypop-shap)ed cells. Can form rosettes from blood cultures.
• • Oxidase-positive, catalase-negative; indole-positive
• • Pitting variable on chocolate agar; often requires 48 – 72 hrs growth
• • Grows on chocolate agar but not on MacConkey agar

Question 60

Eikenella corrodens

Answer 60

• Fastidious coccobacilli
• Gram negative
• Grow best with increased CO2 and hemin
• Non-motile
• Oxidase positive
• Nonsaccharolytic
• Resemble Moraxella sp.
• Catalase-negative
• Often produce yellow pigment
• 45% of isolates pit or corrode the surface of the agar
• In broth media, they may adhere to sides of the tube
• and produce granules
• Bleach-like odor given off from agar surface

Question 61

Kingella kingae

Answer 61

• Coccobacillary to short rods appearing
• in pairs and short chains
• • Nonmotile
• • Nutritionally fastidious
• • Oxidase positive, catalase-negative
• • Ferments glucose, maltose not sucrose
• • May produce yellow-brown pigment
• • May pit the agar
• • Isolated from blood, bone, joint fluid, urine and wounds
• • Most isolates from children <5 years
• • Susceptible to penicillin and most antibiotics

Question 62

HACEK CHART

Answer 62