Lecture |Bacilli Flashcards
Spore formers
- Bacillus anthracis
- Bacillus cereus
Non-spore formers
- Corynebacterium
- Listeria
- Erysipelothrix
- Gardnerella
Branching, non-spore- formers
- Nocardia
- Aerobic actenomycetes
is Bacillus spp. aerobic, anaerobic, or facultative anaerobic?
aerobic & facultative anaerobic
Is Clostridium aerobic, anaerobic, or facultative anaerobic?
anaerobic
- Gram positive
- Aerobic or facultative anaerobic bacilli
- Endospores
- Catalase positive
Bacillus spp.
Clostridium spp. form endospores–
anaerobically
Bacillus spp. form endospores—
aerobically and anaerobically
causative agent of antrax.
Bacillus antracis
a disease of wild and domestic animals including sheep, goats, horses, and cattle.
Anthrax
Types of Anthrax
- Cutaneous Anthrax
- Gastrointestinal/Ingestion Anthrax
- Inhalation Anthrax (wool sorter’s disease)
- Injectional Anthrax
Causes a typical presentation of the ulceration is a black, necrotic lesion known as an
eschar
accounts for most human infections and is associated with contact with infected animal products.
Cutaneous Anthrax
results from ingestion of endospores
Gastrointestinal/Ingestion Anthrax
Gastrointestinal/Ingestion Anthrax presents in two forms:
oral or oro pharyngeal
Usually attributed to toxemia and sepsis.
Gastrointestinal/Ingestion Anthrax
Most fatal; previously referred to pulmonary anthrax, Woolsorters’ disease and ragpickers’ disease
Inhalation Anthrax (wool sorter’s disease)
Bacillus antracis virulence factor
- Lethal toxin (LT)
- Edema toxin (ET)
Each of virelence toxins consists of proteins such as
protective antigen (PA), lethal factor (LF) and edema factor
associated with food borne illness.
B. cereus group
organisms are often associated with infections in immunocompromised patients who have debilitating disease such as cancer or diabetes.
B. cereus
most common type of non gastrointestinal infection caused by B. cereus
endophthalmitis
also referred to as hemolysin IV
cytotoxin K
B. cereus group Virulence factors
- hemolysin BL (HBL)
- Nonhemolytic enterotoxin (Nhe)
- cytotoxin K (Cytk) (hemolysin IV)
- Cereulide
believed to act synergistically
hemolysin BL, nonhemolytic enterotoxin, and cytotoxin (hemolysin IV)
heat-stable, proteolysis, and acid-resistant toxin
cereulide
Specimen procession for Bacillus spp.
heat or alcohol shock
heat specimen 70°C for
30 minutes
heat heat specimen 80°C for
10 minutes
heat specimen 62°C to 65°C for
15-20 minutes (B. anthracis only)
only clinically relevant aerobic organisms capable of producing endospores in the presence of oxygen.
Bacillus spp.
inhibited by high concentrations of CO2
Sporulation
production of spores may be induced by
growth in triple sugar iron (TSI), urea, or nutrient agar containing 5 mg/L manganese sulfate.
a stain required to visualize endospores.
malachite green
appear pink from the secondary stain, safranin
vegetative cells
stains green
endospore
attributed by the fact that the endospores may appear as intra cellular or extracellular clear oval structures upon Gram staining.
Box car or bamboo rod appearance
selective agar for gram-positive organisms that isuseful for the removal of contaminating organisms and the isolation of Bacillus spp.
Phenylethyl alcohol agar (PEA),
used for selection and isolation from fecal contamination
Polymyxin-lysozyme-EDTA-thallous acetate (PLET)
used to induce B. anthracis capsule formation
Bicarbonate agar
an agar that should be incubated in increase carbon dioxide environment
Bicarbonate agar
in this agar, colonies of B. anthracis are nonhemolytic, large (2 to 5 mm), gray, and flat with an irregular margin because of outgrowths of long, filamentous projections.
SBA
has been used to describe the colony morphology of B. anthracis.
Medusa head
colonies of B. anthracis have what type of consistency
tenacious consistency
bacteria having the appearance or characteristic of beaten egg whites.
B. anthracis
ferments glucose
B. anthracis
produces lecithinase
B. anthracis
grows in 7% NaCl and pH<6
B. anthracis
susceptible to penicillin (10 U/mL)
B. anthracis
B. anthracis does not ferment ?
mannitol, arabinose or xylose
Grow on Egg Yolk Agar
B. anthracis
opaque zone around colonies
Lecithinase
oily sheen
Lipase
The hydrolyzed tube remain liquid even after freezing at 4°C
Gelatin Hydrolysis test
clearing of the x ray film
Gelatin Hydrolysis test
nonmotile bacterias
B.anthracis & B. mycoides
motility can be tested by either
- wet mount preparation
- inoculation into motility test medium.
Capsule production by B. anthracis can be detected by
- India ink staining on blood or CSF specimens
- on cells isolated in media supplemented with sodium bicarbonate
penicillin susceptibility of B. anthracis
susceptible
penicillin susceptibility of B. cereus
resistant
Lecithinase +
B. anthracis
Lecithinase -
B. cereus
motile -
B. anthracis
motile +
B. cereus
B. anthracis Hemolysis on BAP
none
B. cereus Hemolysis on BAP
Beta-hemolysis
B. anthracis gelatin hydrolysis
negative
B. cereus gelatin hydrolysis
postive
negative growth on PEA
B. anthracis
positive growth on PEA
B. cereus
Serodiagnosis of B. anthracis is typically available for the detection of the
PA antigen or toxin protein, LF, and EF
immunochromatographic test that presumptively identifies B. anthracis from blood agar within 15 minutes
Red Line Alert Test
most rapid detection method and differentiation of B. anthracis
PCR
recommended vaccine after aerosol exposure to B. anthracis, such as in a bioterrorist event.
Chemoprophylaxis with ciprofloxacin or doxycycline
gram positive “club-shape”
corynebacteria
- nonlipophilic/lipophilic
- catalase +
- Nonmotile
corynebacteria
type of corynebacteria often considered fastidious and grow slowly on standard culture media
Lipophilic corynebacteria
Disease caused by C. diphtheriae is referred to as
diphtheria.
2 Forms of Diptheria
- Respiratory
- Cutaneous
Humans are the only natural hosts of this bacteria
C. diphtheriae.
Respiratory Diptheria are carried in the upper respiratory tract and spread by
droplet or hand-to-mouth contact.
C. diphtheriae most common site of infection
tonsils or the pharynx
C. diphtheriae produce toxin that requires infection with
bacteriophage
causes tissue necrosis and exudate formation triggering an inflammatory reaction.
C. diptheria
combination of cell necrosis and exudate forms this which attaches to the tissues
a tough gray-to white pseudomembrane
consists of nonhealing ulcers with a dirty gray membrane
Cutaneous diphtheria
major virulence factor associated with C. diphtheriae.
Diphtheria toxin
Diphtheria toxin s produced by strains of C. diphtheriae infected with a
lysogenic β-phage
- one of the Corynebacterium species most frequently recovered from human specimens.
- It is part of the normal skin microbiota
- Often been misidentified by clinical laboratories as C. striatum, C. xerosis, and C. minutissimum.
- Opportunist
C. amycolatum
named after Johnson and Kaye
C. jeikeium
most common cause of Corynebacterium-
associated prosthetic valve endocarditis in adults
C. jeikeium
also causes septicemia, meningitis, prosthetic joint infections, and skin complications, such as rash and subcutaneous nodules.
C. jeikeium
veterinary pathogens .
C. pseudotuberculosis & C. ulcerans
Human infections typically have been associated with contact with sheep and are rare.
C. pseudotuberculosis
- Causes a granulomatous lymphadenitis in humans.
- The organism produces a dermonecrotic toxin that causes death of various cell types, and it can produce diphtheria toxin.
C. pseudotuberculosis
- most commonly associated with UTIs
- Up and incoming cause of cystitis
C. urealyticum
- Cause skin ulcers and oxidative pharyngitis
- isolated from humans with diphtheria-like illness, and a significant number of isolates produce the diphtheria toxin
C. urealyticum
a veterinary pathogen That causes mastitis in cattle and other domestic and wild animals
C.ulcerans
- gram positive bacillus
- appears in palisades
- “V” and “L” formations
- club-shaped swellings
- Babès-Ernst granules.
C. diphtheriae
C. diphtheriae often stain irregularly, also giving a beaded appearance with the stain?
methylene blue
In C. diphtheriae, The metachromatic areas of the cell, which stain more intensely than other parts
Ernst granules or Volutin granules
The presence of this in C. diphtheriae indicates the accumulation of nutrient reserves and differs with the type of medium and the metabolic state of the individual cells.
Babès-Ernst granules
Corynebacterium spp. usually grow on what type of agars
5% sheep blood and chocolate agars
produce much larger colonies when cultured on 5% sheep blood agar supplemented with 1% Tween 80
- C. jeikeium
- C. urealyticum
- C. afermentans subsp. lipophi lum
- C. accolens
- C. macginleyi
lipophilic coryneform bacteria demonstrate better growth in broths supplemented with
rabbit serum
is corynebacterium facultatively anarobe?
YES
medias to be used if diphtheria is suspected.
Selective and differential media for C. diphtheriae
medium that can promote production of metachromatic granules because it contains egg yolk
Loeffler medium
medium C. diptheria shows brown-black colonies with a gray-brown halo
Tinsdale medium
a modification of Tinsdale medium, contains sheep red blood cells, bovine serum, cystine, and potassium tellurite.
Cystine-tellurite blood agar (CTBA)
inhibits many noncoryneform bacteria
potassium tellurite
When grown on CTBA, corynebacteria form – ? –(color) colonies from the reduction of tellurite
black or brownish
On Sheep Blood Agar, corynebacteria can display what type of hemolysis
very small zone of beta-hemolysise
useful for differentiating corynebacteria because only C. diphtheriae, C. ulcerans, and C. pseudotuberculosis form a brown halo as a result of cystinase activity.
Cystine-tellurite blood agar (CTBA)
- urease negative
- ferments glucose and maltose (w/o gas
production - reduces nitrate to nitrite
C. diptheriae
produces urease and on SBA forms small, yellowish-white colonies.
C.pseudotuberculosis
colonies of this are flat and dry, have a matte or waxy appearance, and are nonlipophilic. It does not produce any halo in Tinsdale medium; negative for urease; is only able to produce acid from glucose
C. amycolatum
produce acid from starch and is gelatin hydrolysis positive, does not reduce nitrate, urease positive
C.ulcerans
- pinpoint, nonhemolytic, white colonies 2. lipophilic
- coryneform morphology
- nitrate -
- catalase +
- urease +
C. urealyticum
urease positive within minutes after inoculation on a Christensen urea slant.
C. urealyticum
test whether diphtheria antitoxin neutralizes the lethal effect of a cell-free suspension of the suspect organism
Guinea pig lethality test
test utilizes the principle of immunodiffusion.
ELEK test
only effective control of diphtheria
immunization with a multidose diphtheria toxoid
in ELEK test, the presence of this indicates that the strain produced toxin that reacted with the homologous antitoxin.
fine precipitin lines
only effective control of diphtheria is through immunization with
multidose diphtheria toxoid
a preparation of antibodies capable of toxin neu tralization before its entry into the patient’s cells.
Hyperimmune antiserum produced in horses, diphtheria anti toxin (DAT)
- facultative anaerobe
- catalase-positive
- nonbranching,
- oxidase-negative
- gram-positive rod
Listeria monocytogenes
a common cause of meningitis in neonates and immunocompromised individuals especially those who undergone renal transplantation and cancer patients.
Listeria monocytogenes
Contaminated ice cream, hot dogs, and luncheon meats have served as vehicles for this foodborne disease.
L. monocytogenes
a common cause of meningitis in neonates and immunocompromised individuals especially those who undergone renal transplantation and cancer patients
L. monocytogenes
the major virulence factor of L. monocytogenes
Listeriolysin O
a pore- forming toxin that reduces T-cell responsiveness.
Listeriolysin O
This toxin-induced unresponsiveness, in combination with phospholipases, enables the organism to escape from the phagosome of white blood cells, avoid intracellular killing, and spread to the bloodstream
Listeriolysin O
forms pseudopod-like projections that are then ingested by neighboring cells. This provides a means of cell-to-cell spread of the organism. The bacterium eventually reaches the central nervous system and the placenta, resulting in disease (listeriosis).
Actin polymerization
organism produces a bacterial surface protein that induces host cell actin polymerization
Actin polymerization or Act A
short, gram-positive rod that may occur singly or in short chains, resembling streptococci
L. monocytogenes
The colonies are small, round, smooth, and translucent. They are surrounded by a narrow zone of β-hemolysis, which may be visualized only if the colony is removed. The colonies and hemolysis resemble those seen with S. agalactiae
L. monocytogenes
The optimal growth temperature for L. monocytogenes
30° to 35° C
L. monocytogenes grows at 4° C and this technique may be used to isolate the organism from polymicrobial clinical specimens.
cold enrichment
also called a refrigerator bacilli
L. monocytogenes
- Motile
- Ferments salicin
- Hydrolyzes esculin
L.monocytogenes
- Non motile
- Does not ferment salicin
- Do not hydrolyzes esculin
Corynebacterium
- hippurate hydrolysis positive
- catalase positive
- bile esculin hydrolysis positive
- motile at room temperature
L.monocytogenes
exhibits tumbling motility (end-over-end motility)
In wet mount
In motility semi-solid medium “umbrella” pattern is seen when the organism is incubated at temperature?
22° to 25° C but not at 35° C
Block type
CAMP +
Confirmatory findings of L.monocytogenes include
acid production from glucose and positive Voges-Proskauer and methyl red reactions.
Anton’s test–ocular test
Keratoconjuctivitis
The organism may be transmitted through direct contact or ingestion of contaminated water or meat.
Erysipelothrix rhusiopathiae
- gram-positive
- catalase-negative
- non–spore-forming, pleomorphic rod that has a tendency to form long filaments
Erysipelothrix rhusiopathiae
the most common infection caused by E. rhusiopathiae in humans, and a localized skin infection
Erysipeloid
Erysipelas =
S. pyogenes
ssociated with individuals employed in occupations such as fish handlers, farmers, slaughterhouse workers, food preparation workers, and veterinarians
Erysipelothrix infections
Erysipeloid =
Erysipelothrix
make use of Tissue biopsy of the skin lesion
E. rhusiopathiae
- Gram positive
- Short rods/long filaments
- Singly, in short chains, or in “V” shape
E. rhusiopathiae
grows on standard culture media, including SBA and chocolate agar. The colonies often appear α-hemolytic after a few days of growth.
E. rhusiopathiae
- Catalase negative
- Nonmotile
- VP negative
- Hydrogen sulfide production positive
E. rhusiopathiae
Growth of E. rhusiopathiae in a gelatin stab culture yields a highly characteristic “test tube brush– like” pattern at a temperature of
22° C
short, pleomorphic gram-positive rod or coccobacillus that often stains gram variable or gram negative
Gardnella vaginalis
primarily known for its association with bacterial vaginosis (BV) in humans.
G.vaginalis
characterized by a malodorous discharge (fish-like odor) and vaginal pH greater than 4.5 (alkaline)
bacterial vaginosis
BV generally results from a reduction in the
Lactobacillus population in the vagina
Gram staining of vaginal secretions is generally regarded as the
reference method for diagnosing BV.
aids the diagnosis of BV
- “clue cells,”
- large squamous epithelial cells with gram positive
- gram- variable bacilli and coccobacilli clustered on the edges
- Lactobacillus rods are absent in the wet mount.
low lactobacillus in vagina gives this bacteria the chance to grow
Gardnella
Culture Media of Gardnella
- Human blood bilayer Tween (HBT( agar
- 5% to 7% CO2 at a temperature of 35C to 37C
G. vaginalis also produces what type of hemolysis
β-hemolytic
G. vaginalis also produces β- hemolytic colonies on media made with
rabbit or human blood
AEROBIC ACTINOMYCETES
- Nocardia
- Rhodococcus
- Gordonia
- Tsukamurella
- Streptomyces
- Actinomadura
- aerobic, branched, beaded, gram-positive bacilli
- Catalase positive
- partially acid fast, meaning they are able to retain the primary stain only when a weak acid is used as the decolorizer during the acid-fast staining process
Nocardia spp.
decolorizer used in Nocardia spp.
0.5-1% H2SO4 Sulfuric acid
Generally, infections caused by Nocardia occur in
immunocompromised patients.
Nocardia infection begins as a localized subcutaneous abscess that is invasive and quite destructive of the tissues and underlying bone that is termed as
actinomycotic mycetomas
Nocardia infection occurs by two routes:
pulmonary and or other disseminated infections
In Nocardia infection, the pus may be pigmented and contain
“sulfur granules”
“sulfur granules” appear color
yellow or orange
These granules contain masses of filamentous organisms with pus materials
“sulfur granules”
Nocardia spp. grow well on
selective laboratory media
Nocardia spp. grow well on most common nonselective laboratory media incubated at temperatures between
22° and 37° C
days before Nocardia spp. growth is seen
3 to 6 days or more
may enhance recovery of Nocardia spp. by inhibiting the growth of contaminating organisms.
modified Thayer-Martin agar
Nocardia spp. grow on nonselective BCYE agar. what is BCYE agar
buffered charcoal–yeast extract agar.
Colonies have a chalky, matte, velvety, or powdery appearance and may be white, yellow, pink, orange, peach, tan, or gray pigmented.
Nocardia spp.
grow at the presence of enhanced 10% CO2 and in 48 hours but colonies typically appear in 5 to 10 days. They can have a dry, crumbly appearance similar to breadcrumbs
Nocardia spp.
Unique Characteristic of Nocardia spp.
Lysozyme Resistant
- partially acid fast or acid fast
- On SBA, the colonies resemble Klebsiella and can form a salmon pink pigment
- diphtheroid gram-positive rods with traces of branching
Rhodococcus equi
- agent of Whipple disease
- gram-positive actinomycete
- A facultative intracellular pathogen (culture is useless)
TROPHERYMA WHIPPLEI
The presence of characteristic periodic acid–Schiff staining is strongly suggestive of
Whipple disease.
