Aerobic Gram-Positive Rods (3 important genera)
Bacillus, Corynebacterium, and Listeria
Two medically important genera that produce spores
Bacillus and Clostridium
Bacillus anthracis (Morphology, Spore Production, Motility, Unique Properties)
Large: end-to-end chains, Yes, No, Poly-D-glutamic acid capsule; spores
Bacillus cereus (Morphology, Spore Production, Motility, Unique Properties)
Large, Yes, Yes; 50% of strains, Spores
Corynebacterium diphtheriae (Morphology, Spore Production, Motility, Unique Properties)
Small and narrow, No, No, Pleomorphic; Chinese Characters (divides via snapping fission)
Listeria monocytogenes (Morphology, Spore Production, Motility, Unique Properties)
Small, No, Yes; tumbling motion, Grows at 3-4 degrees C; grows intracellulaly
Anaerobic Spore-Forming Gram-Positive Rods
Clostridium (only genus)
- Produce endospores to survive adverse conditions
e. g. C. botulinum, C. tetani, C. perfringens, C. difficile
Clostridium botulinum
- Fastidious spore-forming gram-positive rod shaped organism
- Production of a NEUROTOXIN results in disease (i.e. flaccid paralysis)
- Commonly isolated in SOIL and WATER
Clostridium tetani
- Tennis rackt/drumstick appearance due to terminal ENDOSPORE
- Difficult to grow in vitro due to extreme OXYGEN SENSITIVITY
- Production of a NEUROTOXIN (tetanospasmin) causes spastic paralysis (i.e. lockjaw, arching of back, and respiratory muscle spasms)
- Commonly found in SOIL
Clostridium perfringens
- Hemolytic and produces several toxins (alpha, beta, epsilon, and iota)
- Grows rapidly in tissue and in culture
- NOT motile (unlike other Clostridia)
- Cellulitis, suppurative myositis, gas gangrene, food poisoning
Clostridium difficile
- Associated with prior antibiotic use and other chemotherapies
- Extremely sensitive to oxygen
- WATERY DIARRHEA
Gram-Positive Cocci
Staphylococcus, Streptococcus, and Enterococcus
Staphylocci
Catalase POSITIVE and grow in large clusters
- Grow in media with up to 10% salt
- Aerobic or anaerobic
- Found on skin and mucous membranes
Streptococci
Catalase NEGATIVE and grow in chains
Enterococcus
Catalase NEGATIVE and is in the Lancefield D group
Staphylococcus aureus (Hemolysis, Catalase, Coagulase/Mannitol fermentation, Novobiocin)
Beta or gamma, Positive, Positive/Positive, Sensitive
Staphylococcus epidermidis (Hemolysis, Catalase, Coagulase/Mannitol fermentation, Novobiocin)
Gamma, Positive, Negative/Negative, Sensitive
Staphylococcus saprophyticus (Hemolysis, Catalase, Coagulase/Mannitol fermentation, Novobiocin)
Gamma, Positive, Negative/Negative, Resistant
S. aureus
- Coagulase POSITIVE
- Most pathogenic and causes several diseases (e.g. food poisoning, toxic shock syndrome, scalded skin syndrome, impetigo/bullous impetigo, folliculitis, furuncles or boils, carbuncles, bacteremia and endocarditis, pneumonia and empyema, osteomyelitis, and septic arthritis)
- Produces a golden pigment
S. epidermidis
- Coagulase NEGATIVE
- ubiquitous inhabitant of human skin
- forms biofilm on implanted medical devices (catheters, prosthetic joints, and heart valves)
S. saprophyticus
- Coagulase NEGATIVE
- novobiocin resistant
- Second most common cause of UTI in sexually active young women (ages 13 to 40 y.o.) following E. coli
Streptococcus pyogenes (Lancefield grouping, Hemolysis, Biochemical tests)
A (GAS), Beta, Sensitive to Bacitracin (A disc)
Streptococcus agalactiae (Lancefield grouping, Hemolysis, Biochemical tests)
B (GBS), Beta usually; sometimes Gamma, CAMP test positive; hippurate hydrolysis
Streptococcus pneumoniae (Lancefield grouping, Hemolysis, Biochemical tests)
Nongroupable, Alpha; Viridians group, Soluble in bile; Sensitive to Optochin (P disc)
Streptococcus pyogenes
Uniquely sensitive to Bacitracin compared to other beta hemolytic streptocci
Wide variety of diseases:
-Pharyngitis “strep throat”, Scarlet fever, Impetigo, erysipelas, cellulitis, necrotizing fasciitis, Streptococcal Toxic Shock Syndrome, Bacteremia, Sepsis, Cross-reactive antigen or immune complex disease (e.g. Rheuamtic fever, Acute glomerulonephritis)
Streptococcus agalactiae
Produces diffusible heat stable factor (CAMP factor)
Early onset disease, Late onset disease, Adult diseases (UTIs and compromised adults)
Streptococcus pneumoniae
LANCET-SHAPED or bull-shaped diplococcus
Enterococcus
Catalase NEGATIVE
Enterococcus faecalis and faecium
Both found in the GI or GU tract commonly
-Cause UTI, bacteremia, endocarditis, intra-abdominal abscesses
Gram-Negative Bacteria: Gram-Negative Cocci
Neisseria
- Two important species (N. meningitidis and N. gonorrhoeae)
- Kidney bean-shaped; look like a coffee bean when two are lined up with their flattened sides
Neisseria gonorrhoeae (Shape, Oxidase reaction, Acid via oxidation of carbohydrate, Media Requirements)
Diplococcus, Positive, Glucose only, Chocolate and Thayer-Martin agar
Neisseria meningitidis (Shape, Oxidase reaction, Acid via oxidation of carbohydrate, Media Requirements)
Diplococcus, Positive, Glucose and Maltose, Blood or chocolate agar
Enteric Gram-Negative Rods
Enterobacteriaceae:
- Eschericia (rod shaped)
- Salmonella (rod shaped)
- Shigella (rod shaped)
- Yersinia (rod shaped)
Non-Enterobacteriaceae:
- Vibrio (comma shaped rod)
- Campylobacter (comma shaped rod or S-shaped rod or corkscrew)
- Helicobacter (spiral shaped rod)
- Bacteroides (rod shaped; ONLY OBLIGATE ANAEROBE)
Non-Enteric Gram-Negative Rods
Klebsiella (found in GI tract)
Haemophilus and Legionella (respiratory pathogens)
Francisella (ticks, black flies, rabbit skinning)
Pasteurella (animal bites)
Brucella (unpasteurized/imported dairy products)
Yersinia pestis (flea bites)
Rickettsia (tick bites)
What two Non-Enteric Gram-Negative Rods are opportunistic infections (require a defect in the patients’ immune functioning)?
Pseudomonas and Kelbsiella