Microbiology Review (Ch 4)

Question 1

Gram Positive Cocci (GPC):

Major subgroups? (3)

Major pathogens?

Less common pathogens? (in italics)

Answer 1

Gram Positive Cocci (GPC):

Staphylococci, Streptococci, Enterococci

Staph: Staph Aureus, S. epidermidis

Strep: Strep pneumoniae (“pneumococcus”), Viridans strep, Group A Strep (“pyogenes”), Group B Strep (S agalactiae), Group C, Group G

Enterococci: E. faecalis, E. faecium

Question 2

Gram-Negative Rods (GNR):

Major subgroups?

Major pathogens?

Less common pathogens (in italics)?

Answer 2

Gram-Negative Rods (GNR):

(Aerobes) Enterobacteriacae, Vibrios

Enterobacteriaceae: E Coli, Klebsiella, Enterobacter, Proteus, Salmonella, Shigella, Yersinia, Serratia, Citrobacter, Morganella

Vibrios: Vibrio cholerae, Vibrio parahaemolyticus

Also: Pseudomonas, H influenza, Legionella, Moraxella cararrhalis, Acinetobacter, Campylobacter, Helicobacter, Bartonella, Pasturella, Bordetella, HACEK group

Question 3

Gram-Negative Cocci (GNC):

Major subgroups? (1)

Major Pathogens? (2)

Answer 3

Gram-Negative Cocci (GNC):

Neisseria: Neisseria meningitidis (“meningococcus”), Neisseria gonorrhoeae (“gonococcus”)

Question 4

Anaerobes

Major Subgroups? (3)

Major Pathogens? (2)

Less common pathogens?

Answer 4

Anaerobes

Oral anaerobes, Bowel anaerobes, Clostridium spp

Oral anerobes: Anaerobic strep, Bacteroides, Fusobacterium, Prevotella, Actinomyces

Bowel anaerobes: Bacteriodes fragilis, Anaerobic strep

Clostridium spp: Clostridium difficile, C. perfringens, C. tetani, C. botulinum

Question 5

Gram Positive Rods (GPR)

Major subgroups? (4)

Major pathogens? (0)

Less common pathogens? (5)

Answer 5

Gram Positive Rods (GPR):

Listeria, Corynebacterium, Bacillus, Nocardia

Listeria: Listeria monocytogenes

Corynebacterium: Non-diphtheria Corynebacterium, C diphtheriae

Bacillus: B anthracis (Anthrax), B cereus

Question 6

Lack a typical cell wall so don’t gram stain!

Major subgroups? (5)

Major Pathogens? (4)

Less common pathogens? 6)

Answer 6

Lack a typical cell wall so don’t gram stain!

Mycobacteria, Spirochetes, Mycoplasma, Chlamydia, Rickettsia

Mycobacteria: M tuberculosis, Non-tuberculous mycobacteria

Spirochetes: Treponema pallidum (syphilis), Borrelia burgdorferi (Lyme)

Mycoplasma: M. pneumoniae

Chlamydia: C. trachomatis, C. pneumonia

Rickettsia: Rickettsia rickettsii (RMSF), Ehrlichia, Anaplasma

Question 7

Pneumococcus (Strep pneumonia)

• gram stain and shape?
• most common cause of what?
• common cause of what? (2)
• part of normal flora where?
• treatment?
• what structure is impt for virulence?

Answer 7

Pneumococcus (Strep pneumonia)

• Gram positive cocci, lancet shaped
• Most common cause of bacterial pneumonia
• Common cause of meningitis and otitis
• part of normal throat flora (mixed w other bugs)
• Tx = penicillin – but emerging resistance means we have to use Vanco, others
• Capsule is impt for virulence

Question 8

Group A streptococcus (Strep pyogenes)

• why called “beta-hemolytic” strep?
• gram stain and shape?
• Causes what (2)
• Late sequelae are what? (2)
• Sensitive to what drug?
• Presence in what flora suggests disease?
• Various types of Group A strep are based on what?

Answer 8

Group A streptococcus (Strep pyogenes)

• “beta hemolytic: causes complete hemolysis on blood agar plates
• Gram positive cocci (GPC) in chains
• Causes pharyngitis, wound infections
• late sequelae: rheumatic fever, acute glomerulnephritis
• sensitive to PCN G (except enterococci)
• NOT usually part of normal throat flora: presence there -> disease
• Types of Group A strep based on differences in the “M” protein, within the cell wall

Question 9

Group B Strep (Strep agalactiae)

• sensitive to what?
• normal flora of what?
• impt cause of what conditions? (2)
• are they beta hemolytic?

Answer 9

Group B Strep (Strep agalactiae)

• mostly sensitive to PCN G
• inhibit female genital tract
• cause neonatal septicemia and meningitis
• many strains (not all) are beta hemolytic

Question 10

Viridans streptococci

• gram stain and shape?
• predominant organism where?
• most common cause of what?
• usual treatment?
• a few species?

Answer 10

Viridans streptococci

• Gram Positive Cocci in chains or pairs
• Predominant org in normal oral cavity
• most common cause of subacute bacterial endocarditis on damaged valves
• usual treatment for SBE: penicillin may be sufficient
• Species: S mutans, S sanguis, S salivarius, S mitis

Question 11

Enterococcus faecalis (Strep faecalis)

• Gram stain and shape?
• normal where?
• causes what? (2)
• resistant to what?
• sensitive to what?
• what are VRE?

Answer 11

Enterococcus faecalis (Strep faecalis)

• Gram Positive coccus, pairs and chains
• normal fecal flora
• causes UTIs (10%)
• # 2 cause of endocarditis (less common than Viridans strep)
• “resistant” streptococcus because resistant to PCN
• Ampicillin is used (with exceptions)
• VRE = Vancomycin Resistant Enterococcus

Question 12

What are the 3 GPCs?

Answer 12

Staph, Strep, Enterococci

Question 13

What are the 2 GNCs?

Answer 13

Neisseria meningitidis, Neisseria gonorrhoeae

(meningogoccus, gonococcus)

Question 14

5 that don’t gram stain because they lack a cell wall?

Answer 14

Mycobacteria

Spirochetes

Mycoplasma

Chlamydia

Rickettsia