Aerobic Gram-Positive Bacilli Part II

Aerobic Gram-Positive BacilliPart II

Division of Medical TechnologyCarol Larson MSEd, MT(ASCP)

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• Gram stain– Morphology– Arrangement

• Formation of spores• Catalase reaction

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Differentiation ofMajor GPR Genera

• Spore-forming GPR, catalase positive– Bacillus species– Bacillus anthracis– Bacillus cereus

• Nonspore-forming GPR, catalase positive– Listeria monocytogenes– Corynebacterium species (diphtheroids)– Corynebacterium diphtheriae– Corynebacterium jekeium


GPR Discussed in Student Lab

• Nonspore-forming GPR, catalase negative– Gardnerella species– Erysipelothrix species– Lactobacillus species

• Branching Nocardioform GPR– Nocardia species– Streptomyces species


GPR Discussed in This Lecture

• Pleomorphic gram-variable bacilli• Non-sporulating• Specimen gram

stain:– Clue cells


Gardnerella vaginalis Gram Stain

GPR, pleomorphic, Non-spore forming, Catalase negative

• Does not grow on sheep blood agar• Human Blood Agar (V-agar, HBT-

agar)– Small colonies with diffuse zone of

beta-hemolysis


Gardnerella vaginalisColony Morphology


• Catalase negative• Oxidase negative• Sodium hippurate usually positive• SPS sensitive


Gardnerella vaginalisIdentification


• Normal vaginal flora• Bacterial vaginosis

– Polymicrobic infection with Mobiluncus and Bacteroides

– Diagnosis• Homogeneous, gray discharge• Clue cells• Amine or fishy odor when add 10% KOH• Culture not necessary for diagnosis


Gardnerella vaginalisClinical Significance


What are the key identification characteristics to determine if Gardnerella vaginalis is the cause of bacterial vaginosis?

Examine vaginal specimen for presence of a homogeneous, gray discharge, clue cells on the Gram stain, and an amine or fishy odor when adding 10% KOH. A culture is not recommended, but if done, G. vaginalis grows on V-agar/HBT-agar and it beta hemolytic.

• Two types– Short GPR– Long, filamentous

GPR• Non-sporulating


Erysipelothrix rhusiopathiae Gram Stain


Erysipelothrix rhusiopathiae Colony Morphology

• Grows on BAP– Nonhemolytic or

alpha hemolytic• Microaerophilic



• Catalase negative• Motility

– Nonmotile– Test-tube brush growth pattern in

semisolid motility tube at 48 hours

• H2S positive in KIA/TSI (only GPR)• Sucrose non“F”


Erysipelothrix rhusiopathiae Identification


• Zoonotic– Swine erysipelas (fatal to pigs)

• Man – skin disease– Erysipelas– Direct contact with infected animal– Rarely disseminates causing septicemia

with arthritis or endocarditis


Erysipelothrix rhusiopathiae Clinical Significance


What are the key biochemical reactions that identify Erysipelothrix rhusiopathiae?

Two gram stain morphologies (GPR), two colony types on SBA, catalase negative, H2S positive, test-tube brush pattern in motility tube, sucrose non“F”

• Two types– Long slender GPR in chains– Short GPCB

• Non-sporulating


Lactobacillus speciesGram Stain


• Grows on BAP– Multiple colony morphologies– Nonhemolytic or alpha hemolytic

• Microaerophilic


Lactobacillus speciesColony Morphology


• Catalase negative• Sucrose “F”• Vancomycin “R”


Lactobacillus speciesIdentification


Lactobacillus speciesClinical Significance

• Normal flora– Mouth– GI tract– Female vaginal tract

• Rarely pathogenic– Endocarditis– Meningitis



What is the clinical significance of Lactobacillus species?

It is considered normal flora of the mouth, gastrointestinal tract, and female genital tract



Review

• Actinomycetes– Nocardia species– Streptomyces species


Branching Nocardioform GPR

Nocardia speciesGram Stain

• Pleomorphic, branching, fine, delicate filaments with fragmentation GPR

• Often appears beaded



• Grows on SBA, Mycology media and LJ media

• Aerobic growth appears at 3-30 days

• Waxy, bumpy or velvety rugose forms, yellow to orange colonies


Nocardia species Colony Morphology


Nocardia species Identification

• Partially acid-fast positive• Presence of granules in specimen• Catalase

positive



Nocardia species Clinical Significance

• Habitat: soil and water• Mycetoma (actinomycetoma)

– Tissue swelling– Draining sinus tracts– Presence of granules

• Immunocompromised patients– Pulmonary and disseminated infections



What is the key characteristic in identifying Nocardia species?

Branching GPR that is partially acid fast positive

What primary disease does Nocardia cause and what 3 symptoms are seen?

Mycetoma (aka actinomycetoma). Triad of symptoms: tissue swelling, draining sinus tracts, and the presence of granules

• GPR with extensive branching, chains and spores

• Does not fragment easily


Streptomyces speciesGram Stain


Streptomyces species Colony Morphology

• Grows on SBA, Mycology media and LJ media

• Aerobic growth appears at 3-30 days• Waxy, bumpy or velvety

rugose forms, yellow to orange colonies



• Acid-fast negative


Streptomyces species Identification


Streptomyces species Clinical Significance

• Habitat: soil and decaying vegetation• Mycetoma (actinomycetoma)• Rarely:

– Pericarditis– Bacteremia– Brain abscess



How can you differentiate Streptomyces from Nocardia?

Streptomyces is acid-fast negative and Nocardia is partially acid-fast positive


• Branching Nocardioform GPR– Nocardia species– Streptomyces species


Aerobic GPRSummary

Who am I?HBT media shows

beta-hemolysis

GramStain

Gardnerella vaginalisCauses Bacterial Vaginitis

Who am I?

BAP, growth at 2 days Gram Stain

Erysipelothrix rhusiopathiaeMotility Tube: “test-tube brush” pattern of growth

TSI

Who am I?

LJ agar at 1 week Gram Stain

Nocardia species

Causes Actinomycetoma

Acid Fast Stain

Aerobic Gram-Positive Bacilli Part II

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