Week 1: Basics of Bacteriology Flashcards
The ratio of cellular domains in the human body
10x more prokaryotic cells than eukaryotic
Bacterial functions in the human body
- physiological
- nutritional
- protective functions
What are some things that can affect the normal flora of the human body
- antibiotics
- tissue damage
- medical procedures
- changes in diet
- introduction of new pathogens
Potential clinical implications of human microbiome

Types of relationships between microbes and humans
- Mutualism
- Commensalism
- Parasitic
- Pathogenic
Describe a mutualism
Both the host and the microbe benefit
Describe a commensalism
One partner of the relationship benefits (usually the microbe) and the other partner (usually the host) is neither benefited nor harmed
Decribe a parasitic relationship
The microbe benefits at the expense of the host
Describe a pathogenic relationship
The microbe causes damage to the host
Describe the relationships between microbes and humans and what they mean

What are opportunistic pathogens?
- Only cause disease in those with a compromised immune defense
- Often organisms that are typically normal flora or can normally be controlled by a competent immune system
Examples of opportunistic pathogens
T-cell immune compromise:
- Pneumocystis jerovecii pneumonia
- Cytomegalovirus
Patients receiving broad-spectrum antibiotics
- Clostridium difficile colitis
Patients with intravenous catheters
- Staphylococcus epidermidis bacteremia
Compromised T-cell opportunistic pathogens
- Pneumocystis jerovecii pneumonia
- Cytomegalovirus
Broad-spectrum antibiotics opportunistic pathogens
- Patients receiving broad-spectrum antibiotics
- Clostridium difficile colitis
Intravenous catheters opportunistic pathogens
Staphylococcus epidermidis bacteremia
What are frank pathogens?
Always associated with disease
Examples of frank pathogens
- Neisseria gonorrhoeae
- Shigella
- Human Immunodeficiency Virus
What are facultative pathogens?
Fall between the two extremes (opportunistic and frank) and the majority of organisms that cause disease fall into this group
Examples of Facultative pathogens
- Staphylococcus aureus
- Escherichia coli
Size of prokaryotes
0.2-2.0 um
size of eukaryotes
typically 10-100 um
Nucleus of prokaryotes
no nuclear-bound nucleus
Nucleus of Eukaryotes
True nucleus with nuclear membrane and nucleoli
Prokaryote membrane-wrapped organelles
Absent
Eukaryote membrane-wrapped organelles
Present (Golgi, lysosome, ER, mitochondria, chorplast)
Cell wall of prokaryotes
Usually present and complex
Cell wall of Eukaryotes
When present is chemically simple
Ribosomes of prokaryotes
70S Ribosome
Eukaryotes Ribosomes
80S
DNA of prokaryotes
- Single circular chromosome
- smaller
Eukaryotes DNA
Multiple linear chromosomes
Cell division of prokaryotes
Binary Fission
Cell division of eukaryotes
Mitosis
Sexual reproduction of prokaryotes
- No meiosis
- transfer of DNA fragments only
Sexual reproduction of eukaryotes
Meiosis
Gram stain reaction

Clinically relevant exceptions of the gram stain
- Mycobacterium
- Nocardia
- Mycoplasma
- Ureaplasma
- Chlamydia
E coli gram stain
Negative
Klebsiella gram stain
Negative
Bacteriodes gram stain
Negative
Staphylococcus gram stain
Positive
Streptococcus gram stain
Positive
Listeria gram stain
Positive
Gram stain process
Fixation
crystal violet
decolorization
counter stain safranin

Describe the structural differences between gram-negative and gram-positive bacteria
Gram-positive bacteria
- have a thick peptidoglycan layer
- 3D crosslinking
- degraded by lysozyme
- Teichoic Acid
- links peptidoglycan too lipids in the cell membrane
Gram-negative bacteria
- thin peptidoglycan layer
- 3D cross-linking
- degraded by lysozyme
- Outer membrane
- maintains bacterial structure
- permeability barrier
- Lipopolysaccharide (LPS)
- endotoxin

Describe the features of Gram-positive bacteria

Describe the features of Gram-negative bacteria

List of organisms with poor or no gram-staining
5 listed
- Mycobacteria
- Nocardia
- Mycoplasma/Ureaplasma
- Chlamydia/Rickettsia
- Treponema
Cause of Mycobacteria gram-stain appearance
Contain many mycolic acids and lipids in the cell wall that do not allow the gram stain to penetrate completely
Cause of Nocardia gram-stain appearance
contain mycolic acid and lipids but fewer than mycobacteria
Cause of Mycoplasma/Ureaplasma gram-stain appearance
No cell wall layer (contain a tri-layered cell membrane)
Cause of Chlamydia/Rickettsia gram-stain appearance
Obligate intracellular organisms, gram reaction does not perform well for intracellular organisms, technically they are gram-negative
Cause of Treponema gram-stain appearance
organisms are very small (<1 um), dark-field microscopy is used to visualize, technically, they are gram-negative
Describe the different forms of bacteria propagation

Describe Bacterial division

Describe Bacterial sporulation

Describe the bacterial association with disease

Mechanisms of bacterial pathogenesis
- Adhesion
- Invasion
- Evasion
- Disruption
- Destruction
- Induction
Describe adhesion as a mechanism of bacterial pathogenesis
(host cell surface binding)
Describe Invasion as a mechanism of bacterial pathogenesis
invasion to host cell or physical barrier
Describe Evasion as a mechanism of bacterial pathogenesis
of immune surveillance
Describe Disruption as a mechanism of bacterial pathogenesis
disruption of host cell function
Describe destruction as a mechanism of bacterial pathogenesis
destruction of host cell
Describe Induction as a mechanism of bacterial pathogenesis
induction of host immune response leading to
- inflammation
- anaphylaxis
- autoimmune
Routes of bacterial infection
Respiratory tract
Gastrointestinal tract
Genitourinary tract
Unnatural routes opened up by breaks in mucous membranes or skin
different levels of hos degree mechanisms are enlisted depending on the number of organisms entering and their virulence
Examples of diarrheal pathogens

General characteristics

Streptococcus pyogenes
Clinical syndromes of streptococcus pyogenes
- Tonsillopharyngitis
- Scarlet fever
- Toxic shock syndrome
- Skin & soft tissue infections
Virulence factors of Streptococcus pyogenes (GAS)
8 listed
- M protein
- Hyaluronic acid capsule
- Pyogenic exotoxins
- Streptokinase
- Proteinkinase
- C5a petidase
- Streptolysin S and Streptolysin O
- DNase
Describe M protein
- Key virulence factor
- anti-phagocytic
- may act as an adhesin
- may play a role in invasiveness
Describe hyaluronic acid capsule
anti-phagocytic
Describe pyrogenic exotoxins
- associated with invasive disease and streptococcal toxic shock syndrome
- can act as a superantigen
Describe streptokinase
Can dissolve fibrin clots
Describe proteinase
can damage a variety of cell types
Describe C5a peptidase
Can inactivate complement component C5a adversely affecting chemotaxis
Describe Streptolysin S and Streptolysin O
Hemolysins that can damage a variety of cell types
Describe DNase
Degrades DNA
Describe the general characteristics of Staphylococcus aureus

Clinical syndromes of Staphylococcus aureus
- Skin & soft tissue infections
- Bone & Joint infections
- Bacteremia
- Hospital-acquired pneumonia

Staphylococcus aureus Virulence factors
10 listed
- Nuclease
- Cytotoxins
- Lipases
- Enterotoxins
- Adhesins
- Leukocidins
- immunoglobulin binding proteins
- Autolysins
- Superantigens
- Proteases
Describe S. aureus nuclease
Cleaves DNA and RNA
Describe S. aureus cytotoxins
toxic for many cell types
Describe S. aureus lipases
hydrolyzes lipids
Describe S. aureus Enterotoxins
Superantigens (TSST-1)
Describe S. aureus Adhesins
- Bind cell surface receptors on host tissues, host cells and soluble factors in the blood
- Bind to complement factors to inhibit complement activation cascade
Describe S. aureus Leukocidins
Secreted virulence factors, including toxins and peptides
Selectively target and kill key classes of host immune cell
Describe S. aureus Immunoglobulin binding proteins
- Bind IgGs via Fc
- Immobilize IgGs and inhibit engagement of host immune factors
Describe S. aureus Autolysins
Highly immunogenic cell wall transglycosylases that facilitate invasion of non-professional phgocytes
Describe S. aureus Superantigens
- Potent immunostimulatory exotoxins
- Activate T cells and trigger cytokine release
Describe S. aureus Proteases
- Surface-bound and secreted forms of target host immune factors and tissues
- GluV8 cleaves IgGs via hinge and inactivates effector functions
E. Coli general characteristics

Clinical syndromes of E. coli

Clinical presentations of E. coli

Clinical presentation of S. aureus

Clinical presentation of S. pyogenes

E. Coli virulence factors
- Endotoxin
- Fimbriae
- K-1 capsule
- Toxigenic E. coli
- ETEC
- EHEC
- EPEC
- EIEC