ZYRAH BLES F. NEMIS BSN-1 MIDTERM REVIEWER (LAB)
GRAM POS. BACTERIA & TEST
1. Catalase Test:
Principle: Catalase enzyme breaks down
hydrogen peroxide (H₂O₂) into water and
oxygen gas (O₂).
Result Interpretation:

(+) Catalase: Presence of
bubbles indicates catalase
production.


Example: Staphylococci
(-) Catalase: No bubbles
observed.

Example: Streptococci
2. Coagulase Test:
Principle: Detects the ability of bacteria to
clot plasma by producing coagulase enzyme.
Result Interpretation:

(+) Coagulase: Clot formation.

(-) Coagulase: No clot
formation.
3. Hemolysis Patterns:
1. Alpha-Hemolytic:
 Incomplete hemolysis, green or brown
discoloration around colonies.
2. Beta-Hemolytic:
 Complete hemolysis, clear zone around
colonies.
 Example: Streptococcus pyogenes
(Group A Strep)
3. Gamma-Hemolytic:
 No hemolysis, no change in color.
 Example: Enterococcus spp.
4. Additional Identification Tests:
Optochin Sensitivity:
 Sensitive: Streptococcus
pneumoniae

Resistant: Viridans streptococci
Bacitracin Sensitivity:
 Sensitive: Streptococcus
pyogenes (Group A Strep)

Resistant: Streptococcus
agalactiae (Group B Strep)
Novobiocin Sensitivity:
 Sensitive: Staphylococcus
epidermidis

Resistant: Staphylococcus
saprophyticus
ZYRAH BLES F. NEMIS BSN-1 MIDTERM REVIEWER (LAB)
Staphylococcus aureus
Characteristics:
 Gram-positive cocci in clusters.
 Colonies: Beta-hemolytic, yellow or
golden on blood agar.
 Catalase positive, Coagulase positive.
 Salt-tolerant (halotolerant) on mannitol
salt agar.
 Produces a "gold" color due to
staphyloxanthin pigment.
Habitat and Transmission:
 Normal skin flora.
 Transmission via autoinfection and
direct contact (hands).
Disease Entities:
Known for its ability to adhere to artificial
materials in the body:
Habitat and Transmission:
 Found in human nose (anterior nares)
and skin.
 Transmission via direct contact (hands),
fomites, and contaminated food.

Infected indwelling
catheters

Prosthetic heart valve
endocarditis
Staphylococcus saprophyticus
Characteristics:
Disease Entities:

Gram-positive cocci in clusters.
Causes diseases via exotoxin release:

 Gastroenteritis
 Toxic shock syndrome
 Scalded skin syndrome
Colonies: Whitish, nonhemolytic on blood agar.

Catalase positive, Coagulase
negative.

Novobiocin resistant.
Staphylococcus epidermidis
Characteristics:
 Gram-positive cocci in clusters.
 Colonies: Whitish, non-hemolytic on
blood agar.
 Catalase positive, Coagulase negative.
 Novobiocin-sensitive.
ZYRAH BLES F. NEMIS BSN-1 MIDTERM REVIEWER (LAB)
Group A Streptococci
Streptococcus pyogenes
Characteristics:

Gram-positive cocci in chains.

Catalase negative, betahemolytic.
Diseases:

Pyogenic diseases:

Pharyngitis

Skin and soft tissue
infections (Impetigo
contagiosa, Erysipelas,
Cellulitis)



Necrotizing fasciitis
Toxigenic diseases:

Scarlet fever

Streptococcal toxic
shock syndrome
Immunologic diseases:

Acute rheumatic fever

Glomerulonephritis
Group B Streptococci
Streptococcus agalactiae
Characteristics:

Gram-positive cocci in chains.

Catalase negative, betahemolytic.

Bacitracin resistant.

CAMP test positive (arrowheadshaped zone of hemolysis).
Diseases:

Urinary tract infection in
pregnant women.

Neonatal pneumonia, sepsis,
and meningitis.
Group C Streptococci
(e.g., Streptococcus equisimilis, Streptococcus
zooepidemicus, Streptococcus dysgalactiae)
Characteristics:

Gram-positive cocci in chains.

Catalase negative, betahemolytic.
Diseases: Generally associated with various
infections.
Group D Streptococci
(Enterococci, Streptococcus bovis)
Characteristics:

Gram-positive cocci in chains.

Catalase negative, gamma
hemolytic.

Growth in bile, hydrolyzes
esculin in bile-esculin agar (BEA).
Habitat and Transmission:

Found in human colon, urethra,
and female genital tract.

May enter bloodstream during
gastrointestinal or
genitourinary tract procedures.
Diseases:
ZYRAH BLES F. NEMIS BSN-1 MIDTERM REVIEWER (LAB)

Urinary tract infections.

Biliary tract infections.

Endocarditis.
Streptococcus pneumoniae
GRAM POSITIVE RODS
Bacillus anthracis
Characteristics:

Aerobic, gram-positive, box-carshaped rods.

Nonmotile, spore-forming.

Medusa head morphology on
culture.
Characteristics:



Gram-positive "lancet-shaped"
cocci in pairs or chains.
Catalase negative, alphahemolytic.
Optochin sensitive, bile soluble.
Diseases: Pyogenic diseases:

Pneumonia

Otitis media, sinusitis,
meningitis

Septic shock
Habitat and Transmission:

Found in soil.

Transmitted through contact
with infected animals or
inhalation of spores
(woolsorter's disease).
Bacillus cereus
Characteristics:
Viridans Streptococci

Aerobic, gram-positive, sporeforming rods.

Motile.

Spores survive on grains like
rice, leading to foodborne
illness when rice is reheated.
Representative Species:

Includes S. mutans, S. mitis, S.
sanguis, S. salivarius, S.
anginosus.
Habitat and Transmission:

Found in the oropharynx.

Enters bloodstream during
dental procedures.
Spectrum of Disease:

Food poisoning:

Emetic form (short
incubation, vomiting,
abdominal cramps).

Diarrheal form (longer
incubation, diarrhea,
abdominal cramps).
Diseases:

S. mutans: Dental caries.

S. sanguis: Subacute bacterial
endocarditis (SBE).

S. intermedius: Brain abscesses.
ZYRAH BLES F. NEMIS BSN-1 MIDTERM REVIEWER (LAB)
Clostridium tetani
Characteristics:
Clostridium perfringens
Characteristics:

Anaerobic, gram-positive,
spore-forming rods.

Anaerobic, gram-positive,
spore-forming rods.

Terminal spore gives it a tennis
racket-like appearance.

Double hemolysis on blood agar.
Habitat and Transmission:

Found in soil.

Transmission occurs through
traumatic implantation into
tissues, leading to spore
germination and toxin
production.
Clostridium botulinum
Characteristics:

Anaerobic, gram-positive,
spore-forming rods.

Often associated with bulging
cans.
Pathogenesis:

Produces botulinum toxin,
causing flaccid paralysis
(foodborne botulism, infant
botulism, wound botulism).
Spectrum of Disease:

Foodborne botulism, infant
botulism, wound botulism.
Habitat and Transmission:

Found in soil and human colon.

Causes myonecrosis in wounds
and food poisoning through
ingestion of contaminated food.
Clostridioides difficile
(formerly Clostridium difficile)
Characteristics:

Anaerobic, gram-positive,
spore-forming rods.
Habitat and Transmission:

Colonizes the colon, particularly
in hospitalized patients.

Transmission via the fecal-oral
route.
Spectrum of Disease:

Causes pseudomembranous
colitis with non-bloody diarrhea
and toxic megacolon.
ZYRAH BLES F. NEMIS BSN-1 MIDTERM REVIEWER (LAB)
Corynebacterium diphtheriae
Characteristics:

Aerobic, gram-positive, nonspore-forming rods.

Club or comma-shaped,
arranged in V or L shapes.

Metachromatic granules visible.
Habitat and Transmission:

Colonizes the human throat.

Transmission via respiratory
droplets.
Spectrum of Disease:

Causes diphtheria with
prominent gray
pseudomembranes over tonsils
and throat, potentially leading
to airway obstruction and
systemic complications.
Listeria monocytogenes
Characteristics:

Gram-positive rods.
Habitat and Transmission:

Colonizes the gastrointestinal
tract of animals and humans.

Transmission through ingestion
of contaminated food,
particularly unpasteurized milk
products.
Spectrum of Disease:

Can cause serious infections,
especially in
immunocompromised
individuals and pregnant
women (crosses the placenta).
ZYRAH BLES F. NEMIS BSN-1 MIDTERM REVIEWER (LAB)
Gram-Negative Bacteria:
Neisseria Species
Shape: Diplococci (kidney bean-shaped
individual cocci)
Aerobic: Yes, generally. N. gonorrhea can grow
anaerobically.
Motility: Nonmotile
Oxidase Test: Positive
Carbohydrate Oxidation: Yes
Culture Medium
 Thayer-Martin or Modified Thayer
Martin agar
Oxidase Test
 Identifies organisms with cytochrome c
in their respiratory chain.
 Positive test turns the reagent
blue/purple.
1. Neisseria gonorrhea
Colonies: Small, mucoid, oxidas positive
Fermentation: Glucose only
Culture Appearance: Opaque colonies
Habitat: Human genital tract
Transmission: Sexual contact or passage
through birth canal
Specimens:
 Urethra, cervix, rectum, conjunctiva,
throat, synovial fluid
Diagnostic Tests
Gram Stain: Many diplococci within
PMNs (presumptive diagnosis)
Gold Standard Test: NAAT
Diseases
Gonococcal Urethritis:
Urethritis and epididymitis in men
Most common cause of urethritis
2. Neisseria meningitidis
Capsule: Encapsulated with large
polysaccharide capsule
Fermentation: Glucose and maltose
Colonies: Oxidase-positive on chocolate agar
Habitat: Upper respiratory tract (URT)
Transmission: Respiratory droplets
High Risk Areas: Close quarters like dormitories,
camps, and during travel
Diseases Meningitis:
 Most common in 2-18 year olds
 Symptoms: Fever, headache, stiff neck,
increased PMNs in spinal fluid
Meningococcemia:
 Dissemination into the bloodstream
 Symptoms: Multiorgan disease,
consumptive coagulopathy, petechial
or purpuric rash (purpura fulminans)
ZYRAH BLES F. NEMIS BSN-1 MIDTERM REVIEWER (LAB)
Coccobacilli
1. Haemophilus influenzae
Shape: Non-motile, small Gram negative
coccobacillary rods
Growth Requirements: Fastidious, requires
factor X (hemin) and V (NAD)
Culture:
Chocolate agar with flat, grayish,
translucent colonies
IsoVitaleX-enriched chocolate agar
Satellite phenomenon around
Staphylococcus aureus colonies (hemolysis by S.
aureus releases factor V)
Quellung Test
 Positive (antibodies bind to the
bacterial capsule)
Habitat: Upper respiratory tract
Diseases
 Sinusitis, otitis media, pneumonia
 Meningitis
 Epiglottitis
 COPD exacerbations
2. Haemophilus ducreyi
Shape: Small Gram-negative rods in strands
Growth Requirements: Requires factor X
(hemin) but not factor V (NAD)
Disease: Causes chancroid
3. Bordetella pertussis
Shape: Minute, Gram-negative coccobacilli
resembling H. influenzae
Culture:
 Bordet-Gengou agar
 Regan-Lowe charcoal medium
Habitat: Upper respiratory tract
Transmission: Respiratory droplets
Disease: Pertussis (Whooping Cough)
 Symptoms: Hacking coughs with
copious mucus, ending with an
inspiratory "whoop"
 Prevention: Acellular vaccine (DTaP,
combined with diphtheria and tetanus
toxoids)
4. Legionella pneumophila
Growth: Poorly Gram staining, silver stain,
charcoal yeast agar
Habitat: Found in water systems like airconditioning units
Disease: Legionnaires' disease
ZYRAH BLES F. NEMIS BSN-1 MIDTERM REVIEWER (LAB)
Gram-Negative Bacilli: Spectrum of Disease
3. Salmonella spp.
1. Pseudomonas aeruginosa
Characteristics:
Skin and Soft Tissue Infections:
 Burn wound infections
 Hot tub folliculitis
 Green nail syndrome
Ear Infections:
 Otitis externa (Swimmer's ear)
 Chronic suppurative otitis media
Pneumonia:
 Ventilator-acquired pneumonia
 High-risk community-acquired
pneumonia (CAP) in
immunocompromised patients
Urinary Tract Infection:
 Common cause of nosocomial UTIs
2. Shigella spp.
Characteristics:
 Slender, non-motile Gram negative rods
 Facultative anaerobes
 Oxidase negative, non-lactose
fermenter, H2S non-producer
Culture Media: XLD (Xylose Lysine
Deoxycholate)
 Convex, circular, transparent colonies
with intact edges
Diseases
 Intestinal Infection: Causes dysentery
 Facultative anaerobes
 Non-lactose fermenter
 Motile, produces H2S (black centers on
XLD medium)
Tests:
 Widal test (detects antibodies
inpatient's serum)
Habitat:
 S. typhi: Human colon only
 S. enteritidis: Enteric tract of humans
and animals (e.g., chickens, livestock)
Transmission: Fecal-oral route
Diseases:
 Intestinal Infection
 Typhoid Fever: Caused by S. typhi
4. Proteus mirabilis
Characteristics:
 Facultative anaerobic Gram negative
rods
 Non-lactose fermenting, urease positive
 Swarming motility
Urease Test:
Determines the ability to split urea,
producing ammonia and increasing urine pH
ZYRAH BLES F. NEMIS BSN-1 MIDTERM REVIEWER (LAB)
Diseases Complicated UTI:
 Associated with nephrolithiasis
(struvite stones or staghorn calculi)
5. Escherichia coli
Characteristics:
 Lacose fermenter with green sheen
Diseases:
 UTI: Most common cause
 Intestinal Infections: Four strains (ETEC,
EPEC, EHEC, EIEC)
 Neonatal Meningitis: Second most
common cause
 Hemolytic Uremic Syndrome:
 Triad of hemolytic anemia,
thrombocytopenia, and renal failure
 Pyogenic Liver Abscess
Diseases
 Lobar Pneumonia
 UTI
COMMA SHAPED
1. Campylobacter jejuni
Shape : Comma-, or S-shaped, seagull wing
appearance
Growth Requirements: Microaerophilic
Tests: Positive oxidase and catalase tests
Optimal Growth : 42°C on Skirrow agar
Habitat
 Human and animal feces (cattle,
chickens, and dogs)
Transmission: Fecal-oral route
Diseases Bacterial Gastroenteritis:
 Watery, foul-smelling diarrhea followed
6. Klebsiella pneumoniae
Characteristics:
 Lactose fermenter, urease positive
 Facultative, non-motile Gram negative
rods with a large polysaccharide capsule
Habitat
 Upper respiratory tract (URT) and
gastrointestinal tract (GIT)
Transmission
 Aspiration/inhalation or ascending
spread of fecal flora
by bloody stools, fever, and severe
abdominal pain
Disease Associations:
 Guillain-Barré syndrome (most
commonly identified cause)
 Reactive arthritis (Reiter syndrome)
ZYRAH BLES F. NEMIS BSN-1 MIDTERM REVIEWER (LAB)
2. Vibrio cholerae
3. Helicobacter pylori
Shape: Comma-shaped Gram-negative rods
Motility: Motile with shooting star motility
Tests: Oxidase-positive, ferments sucrose and
mannose but not arabinose
Shape: Spiral, curved, or fusiform rodshaped
Motility: Motile
Tests: Oxidase-positive, catalasepositive,
urease-positive
Growth Requirements: Microaerophilic
Culture: TCBS (thiosulfate citrate bile salts
sucrose) agar, producing yellow colonies
(sucrose fermented)
Habitat: Found in aquatic environments
Transmission: Contaminated water or food
Diseases:
 Cholera: Profuse watery diarrhea (rice
water stools), severe dehydration, and
electrolyte imbalance
Habitat: Human stomach
Transmission: Ingestion
Diseases
Peptic Ulcer Disease:
 Recurrent pain in the upper abdomen,
often accompanied by bleeding into the
gastrointestinal tract
Disease Associations:
 Gastric carcinoma
 MALT lymphomas