Block I: General Flashcards
(158 cards)
1
Q
sterile areas in the body (no association with bacteria)
A
-CSF, blood, lung, deep tissue
2
Q
general mechanisms of antibiotic resistance
A
- de novo mutations causing antibioitc resistant traits
- transfer of preexisting resistant genes from the environment
- transver between bacteria (mobile DNA elements & horizontal DNA transfer)
3
Q
Peptidoglycan
A
major feature of cell walls of bacteria
- gram-positives: thick peptidoglycan layers
- gram-negatives: thin peptidoglycan layers
**target for many abx because humans do not have peptidoglycans
- gives osmostic stability to cell (when acted on by abx, cells lose osmotic stability & lyse)
- consists of polysaccarhide chains crosslinked by peptide bridges
- subunit: disaccharide with peptide tail; peptide crossbridge attaches to peptide tail
- synthesized in cytoplasm, then transferred to membrane to rane, then to the cell wall
4
Q
bacteria classification: presence of specific enzymes
A
- ex) catalase: if a bacteria has catalase, it will create bubbles when treated with peroxide (as it detoxifies reactive oxygen species)
- can also look for presence of: oxidase, urease, coagulase, hemolysin
**enzyme presence is diagnostic/identifying for a bacteria (but not used to classify virulence)
5
Q
nomenclature of bacteria
A
genus species
(genus then species in italics)
6
Q
Gram-negative rods
A
pseudomonas
vibrio
enteric: escherichia coli
obligate intracellular parasites: rickettsia, chlamydia
7
Q
characteristics of the “perfect antibiotic”
A
- selective (for bacteria)
- specific
- lethal
8
Q
AB Toxins
A
(exotoxins that act intracellularly)
- A subunit: active subunit that is responsible for enzymatic activity that affects host physiology
- B subunit: binding subunit that delivers the A subunit & determines which cell types are affected (binds to cell surface receptors)
Ways to distinguish AB toxins:
- potency (very toxic)
- ability to mimic infection
ex) Anthrax toxin is a model of AB toxin translocation
9
Q
gram stain
A
1- stain with crystal violet (purple)
2- fix stain with potassium iodide
3-decolorize with alcohol (gram positives remain purple)
4- counterstain with safranin (gram negatives become pink)
10
Q
benefits of the normal flora
A
- provide nutrients
- stimulate the immune system (espeically in the gut)
- compete with pathogens
(germ-free animals are much more susceptible to colonization by intestinal pathogens)
11
Q
How do macrophages recognize LPS?
A
- LPS receptor complex (CD14, Toll-like receptor 4, MD2)
- -CD14= LPS binding portion (protein on surface, grabs LPS out o fsystem)*
- **if antibodies to CD14 inhibit inflammation induced by LPS and gram-negative bacteria*
12
Q
(immune mediated tissue disease) acute local tissue damage
A
- local inflammation impairs tissue function
- edema
- neutrophil recruitment & activation
-
13
Q
exotoxins that act on ECM
A
(extracellular)
- attack/bind to ECM rather than to host cell itself
- Staphylococcal scalded skin syndrome (SSSS)– toxin disrupts epithelial tight junctions by degrading desmosome components
- also: collagenases, elastases, hyaluronidases, DNAses, streptokinase
14
Q
transpeptidation of peptidoglycan in bacterial cell wall
A
- when glycan chains are crosslinkjed to each other, losing the terminal D-alanine
- transpeptidation occurs in both gram positives and negatives, although the gram negative peptidoglycan structure differes soemwhat
**B-Lactam abx inhibit transpeptidation
15
Q
synergy
A
when 2 antibiotics work better together than separately
(often bactericidal)
16
Q
current therapy for sepsis
A
- immediate stabilization (ABCs)
- obtain initial database
- obtain appropriate cultures
- prompt use of antimicrobial agents (consider drainage/surgical drainage)
- idtenify & manage organ dysfunction
FLUIDS
17
Q
monoclonal
A
cultured bacteria that consist of genetically identical individuals descended from a single ancestor
18
Q
minimum bactericidal concentration (MBC)
A
minimum concentration of drug that kills the bacteria
19
Q
Bacteria Capsule Histo
A
20
Q
major factors that contribute to antimicrobial resistance epidemic in bacteria
A
1-non-prescription antibiotic use (creates strong environmental selection pressure)
-animal feeds, easy access to abx in developing countries, antibacterials present in household cleaners
2- misuse of abx
-lack of stewardship, noncompiance in patients
3-poor santiation (puts bacteria into environment)
4-lack of new abx in drug development pipeline
21
Q
how bacteria overcome the innate defense of phagocytosis
A
- thick polysaccharide capsules
- resist lysosomal killing by growing within the phagolysosome
- prevent phagolysosome fusion, so that can’t be degraded
- escape from phagosome
-
22
Q
transposition
A
(process of gene transfer within an organism)
- via transposons: small DNA elements that can cut themselves out of sequence and add themselves in elswehere
- transposons often carry additional genes to ensure their survivial– leading to abx resistance
23
Q
critical microbial products involved in sepsis
A
gram negative: LPS, DNA
gram positive: protein toxins, lipotheichoic acid, lipoproteins, peptidoglycan
**gram positive and gram negative sepsis can not be distinguished clinically
24
Q
elements of antimicrobial therapy
A
- selective toxicity of the agent
- susceptibility of the pathogen to the agent
- effective concentration at the site of infection
- maintenance of effective concentration for sufficient time
- side effects
25
phagocytosis as an innate defense in deep tissue/blood
- neturophils, monocytes, macrophages are all involved in phagocytosis
- phagocytes are recrutied during the inflammatory response
26
influx and efflux of gram negative bacteria
- in gram negatives, there is the inner membrane and outer membrane (serving as 2 checkpoints for any influx or efflux\_
- outer membrane has porins: semi-selective energy-independent channels
- inner membrane has transporters/pumps
\*\*these checkpoints control drug uptake & efflux into bacteria (effectiveness of abx)
27
chemotaxis
- important function of motility
- movement in response to chemical stimulus (attractants are bacteria that swim up concentration gradients, repellents swim down gradients)
28
Superantigens
(exotoxins that work extracellularly)
- bind to TCR and MHC outside of peptide-binding grooves, resulting in activation of all T-cells with a certain domain --\> causing massive release of cytokines
ex) staphylococcal TSS
29
macrophage vs monocyte
- both are phagocytes
- longer-lived than neutrophils
- macrophages: in tissues
- monocytes: in circulation
30
(immune mediated tissue disease) chronic local tissue damage
-chronic inflammation eventually results in displacement of tissue cells with leukocytes & fibrin
31
what is a bacterium?
- microscopic
- haploid
- anucleate
- prokaryotic
32
mechanisms of bacterial pathogen damage to host
-either immune-mediated (collateral damage resulting from immune activation by bacteria; can be due to either innate or adaptive immune responses)
OR
-toxin-mediated damage (damage resulting from product of bacteria)
33
the human microbiome(s)
- composition of microbiome varies in different areas of the body
- mouth, skin, colon, esophagus, stomach, vagina
34
selective toxicity of an antimicrobial
STRATEGIES:
- lack of target in human host
- difference in target sensitivity
- differential concentration of antibiotic by bacterial & human cells
35
steps required of a bacterium to cause disease
1- encounter & enter host
2-establish an infectious niche
3- multiply, cause tissue damage
4-spread to other tissues, hosts, or both
36
blood agar
- medium containing RBCs
- frequently used for throat cultures
- hemolysins present (lyse RBCs) in host, and type of hemolysis seen in the blood agar is useful for distinguishing different species of streptococci
37
minimum inhibitory concentration (MIC)
-mimimum concentration of a drug that inhibits a bacteria
38
SOS response
- if a cell is exposed to DNA damage, it triggers RecA protein to be active, which induces mutations (under stress)
39
AB toxins that modulate cAMP levels intracellularly
- cholera & pertussis toxins: ADP-ribosylate G proteins--\> actiavtion of adenylate cyclase
- anthrax EF toxin & pertuss AC toxins: adenylate cyclase enzymes
- **increase cAMP:** increases fluid secretion from epithelial cells, inhibits phagocyte chemotaxis & effector functions
40
Gram negative cocci
neisseria
& others
41
How to categorize microbes?
- phylogeny (based on 16S RNA)
- structure (shape & stain)
- nature of interaction with host (symbiosis, commensalism, parasitism)
- pathogenic strategies
42
sedementation coefficients (refers to molecular weight) of bacteria bacterial ribosomes
70S
-made of 2 subunits; in bacteria: 30S and 50S
43
direct detection method of diagnosing infection
- DNA or microbial antigen detection
- very specific & sensitive
- tests not always available
44
replisome
origin of DNA replication in bacteria
45
Phase Variation
-phase variation results in phenotypic heterogeneity in an organism
\*\*important to vary antigens in host
-*evade host defenses, adapt to different niches*
**mechanisms:**
slipped strand mispairing
site-specific recombination
epigenetic regulation mediated by DNA methylation
46
therpeautic index
- ratio of the minimum toxic dose to the minimum effective dose
- this ratio must be \>1 for an abx to be of use
\*\*high therapeutic index= not generally toxic to patients
47
Gram-Negative Bacteria (structure)
- inner membrane (inside cell wall, consists of phospholipid)
- outer membrane (outside cell wall, consists of phospholipis & lipopolysaccharide LPS)
- LPS is the endotoxin of gram negative baceria (pathogenesis)
- 2 types of protein in outer membrane: porin & lipoprotein
48
how many toll-like receptors do humans have?
10
49
gram-positive cocci
staphylococcus
streptococcus
enterococcus
50
epidemiology of sepsis
- more common among men
- more common among nonwhite
- gram-positive more positive than gram-negative
51
colloquial name for *streptococcus pneumoniae*
pneumococcus
52
sepsis
formal definition: alterations in physiology (fever, respiratory rate, blood pressure, organ function)
**accompanied by an infection**
-life-threatening condition that arises when the body's response to an infection injures its own tissues & organs
(local infection with profound systemic response)
-sepsis can be mimicked by other non-infectious disorders
53
transduction
(process of horizontal gene transfer between organisms)
- agent: phage (viruses that infect bacteria)
- **virulent phages:** replicate within host cell, then destory host, releasing infectioius virions
- **temperate phages:** replicate lytically or go latent
**generalized transduction:** phages with nonspecific DNA encapsulation package host DNA instead of phage DNA during lytic growth-- then can inject DNA into new cell
**specialized transduction:** when bacterial genes transferred from one cell to another by becoming incorporated into a phage chromosome (phage uses SOS response to induce replication, then find a new host after excising itself)
54
teichoic acid
- polymer of ribitol-phosphate or glyercol-phosphate
- part of gram positive cell walls, confers stability of the peptidoglycan
- not yet used as target for abx
55
what kind of growth is characteristic of microbial growth?
- exponential growth: every cell takes the same amount of time to complete a binary fission event
- a limitation of exponential growth is having enough nutrition for this growth
- log phase cells show most consistent physiological parameter (so are the standard for most experiments in microbio)
56
why are bacitracin and vancomycin's mechanisms unique?
they both bind to microbial metabolites rather than inhibiting an enzyme
57
gyrase & topoisomerase
- maintain the supercoiling of bacterial DNA
- recognize improperly coiled DNA and fix it
\*\*protein-bound DNA is good target for antibioics (quinolones & fluoroquinolones)
58
EARLY GOAL-DIRECTED THERAPY (EGDT) for sepsis
-administration of IV fluids within the first 6 hours of presentation
59
bacteria classification: interaction with oxygen
- anaerobic: grow in oxygen-free environment
- obligate anaerobe: killed by oxygen (often form spores so that they can spread in environment)
- facultative anaerobe: can live in aerobic or anaerobic environment
- aerobic: grow in oxygen-containing environment
- obligate aerobe: need oxygen to grow
- some are "microaerophilic"- they ferment (metabolism without oxygen) for energy, but can grow in contact with oxygen at less than atmospheric pressure
60
4 categories of Immune-mediated tissue disease after bacterial infection
1- acute local damage
2-chronic local damage
3-acute systemic disease
4-chronic systemic disease
61
How do bacteria resist B-lactam antibiotics?
-they produce beta lactamase, which breaks down the B-lactam ring in the abx, making it ineffective
62
Spirochetes
treponema
borrelia
63
shapes of bacteria
- bacillus: rod
- coccus: sphere
- coccobacillus (oval)
- comma (vibrio)
- helical (spirochete)
64
autoclave
procedure for sterilizing solutons (especially those that form spores)
- invovles a chmaber into which high pressure steam is injected
- kills spores
65
Bacterial Flagella
- promote motility
- variable between bacteria
- not essential for growth, but important for infection
66
Sulfonoamides mechanism of action
- interfere with folate synthesis
- block the action of dihydropteroate synthase (DPS) (competitive inhibition)
- DPS not found in humans
67
(immune mediated tissue disease) chronic systemic disease examples
**Reactive Arthritis:** chronic inflammation secondary to many bacterial infections
-doesn't require direct infection of joints (symtpoms are due to immunological response & persist after abx treatment)
**Cachexia (wasting):** can result from chronic inflammation
**Immune Complex Disease:** circulating antigen-antibody complexes become depositied in glomeruli or joints, triggering local complement activation & inflammation
68
fastidious bacteria
-bacteria with many growth requirements
(have evolved in nutrient-rich environments so have lost many biosynthetic pathways required for growth on a simple media)
also called obligate pathogens/non-culturable
69
6 general mechanisms for antibiotic resistance in bacteria
1- target site absent
2-enzymatic inactivation (\*most common mechanism of transmissable resistance)
3-target site modification (high level resistance)
4-drug efflux (low level resistance)
5- altered cell wall permeability
6- bacteria present excessive binding sites that are decoys
70
Innate defenses in deep tissue & blood
- iron starvation
- complement
- phagocytosis
- confinement of infection (abscess or granuloma)
71
differential media
-lab media that permits visual distinction of different types of bacteria due to differences in coloring or colony morphology
72
adjusting drug dosing based on pharmacokinetic parameters
- **clearance** is most important parameter
- loading dose will be the same for all patients, but following doses have to be adjusted based on weight & other factors
73
Classes of Exotoxins
(secreted by bacteria)
ACT INSIDE HOST CELLS
-AB toxins
ACT EXTRACELLULARLY
- membrane-disrupting toxins
- superantigens
- extracellular matrix degrading enzymes
74
enzymes that lead to lysis of peptidoglycan in cell wall
lysozyme
endopeptidase
amidase
75
drugs that target peptidoglycan vs drugs that target membranes of bacteria
=drugs that target the membranes are less selective
76
McConkey Agar
- classified as both selective and differential media
- selective media designed specifically for selective growth of gram negative enteropathogens
- made with crystal violet & bile salts (preventing the growth of gram positives)
- lactose & pH indicator used to identify if lactose-utilizing organisms are present
--\> result: selective identification of gram negative enteric organisms
77
(immune mediated tissue disease) acute systemic responses
- septic shock= most dramatic
- caused by overwhelming systemic innate immune response to bacteria
- symptoms: result from systemic stimulation of innate immunity & cytokine release
78
what is the effect of the vast majority of bacteria on humans?
-either beneficial or non-harmful (normal flora/microbiome)
\*only a small minority are pathogens (causing disease)
79
which bacteria can undergo transformation to incorporate other DNA into their genome?
(horizontal gene transfer)
-naturally competent bacteria: streptococcus, hemophilus, neisseria
80
immunologic assays for diagnosis of infection
- presence of antibodies or T cells specific for a microbial antigen
- diagnosiing active infection requires seroconversion, increase in titerm or IgM test
81
heavily colonized ares of the body
-large bowel, mouth, skin, vagina
82
what is the toxic moiety of endotoxin?
- Lipid A (lipid A inserts LPS onto the outer membrane of gram negative bacteria)
- LPS administration into humans mimics sepsis
83
c. difficile
- most common cause of pseudomembranous colitis in humans
- most commonly seen after normal flora is eradicated by antibioitcs (shows importance of normal microbiome)
84
bacterial secretion systems, to establish infection in host
- type III & IV secretion systems
- span from bacterial cytosol to host cytosol
- bacteria inject effector proteins that alter host physiology
\*\*only occurs in gram negative bacteria
85
culture method of diagnosing infection
- must be followed by additional microscopic/biochemical/molecular or immunological assays
- common
- can be difficult/impossible for some pathogens
86
what is an antibiotic?
antimicrobial agent of microbial origin
87
Bacteria Capsule
- loosely-associated polysaccaride; gel-like layer of polymers that surround some bacteria
- not essential for bacterial growht
- variable (not seen in all bacteria)
- important for resisting immunity (inhibit phagocytosis by host cells)
88
common diagnostic methods of infections
-microscopic, culture, direct detection of microbial products, immunologic assays
89
Therapeutic Inhibition of Exotoxins
- **active immunization:** vaccines containing inactivated toxin protein (toxoid); producing protective antibodies
ex) diphtheria, tetanus, botulism
**-passive immunization:** therapeutic administartion of anti-toxin antibodies raised in animals
**-small molecule inhibitors** (being developed)
90
where is DNA located in bacteria?
condensed in the nucleoid
91
microscopic method of diagnosing infection
- i.e. gram stain, acid fast stain
- useful & quick, but not specific
92
why do people with sepsis sometimes present with normal vital signs?
- elderly/malnourished patients may not have fever: don't have normal cytokine release
- people on beta-blockers may not show tachycardia
- WBC may be changing and could appear in normal range when lab work done
93
features of bacteria that can be used to identify a bacterium
- size, shape, staining
- interactions with oxygen
- nutritional requirements
- presence of particular enzymes
- antigens
- molecular methods
94
complement system
- innate defense in deep tissue/blood
- microbe recognized, induces proteolytic signaling cascade, which leads to covalent deposition of complement components on the surface of the microbe & the generation of pro-inflammatory peptides
95
cultivation of bacteria
-can be cultured on liquid and semisolid media (agar)
96
Periplasmic space
aqueous compartment between inner and outer membranes in gram-negative bacteria
97
bacterio-static drugs
inhibit bacterial growth
98
iron starvation in deep tissue/blood
- innate defense against bacteria
- transferrin system keeps free iron levels low
- iron-binding proteins are induced during inflammaition
- bacteria secre siderophores to try to traph free iron
99
components of outer envelopes of bacteria
capsule, pili, flagella --\> not essential for growth; important for infection
outer membrane, cell wall, inner membrane --\> essential for growth; targets for antibiotics
100
Bacteria fimbriae and pili
- adhesive structures that extend away from surface
- major antigens
- variable between bacteria
- not essential for growth
101
Acid-Fast Bacteria (structure)
(primaroly Mycobacteria)
- structure is basically gram-positive organization (inner membrane, cell wall)
- differ: large amounts of lipid in outer envelope & mycolic acid
--\> thought to be responsible for acid-fast stain
102
septicemia
lots of bacteria in the blood
sepsis: speticemia plus evidence of a systemic response
103
bacteria classification: nutritional requirements
- non-culturable (obligate pathogens): have co-evolved with host for so long that they are unable to be cultured in lab
- auxotroph: able to grow in lab, but need specific pathogens to grow
- prototroph (facultative pathogens): bacteria can make everything they need to grow; all they need is P, N, C in environment
104
bacteria have some different biochemical pathways than humans
-ex) bacteria can provide essential vitamins to humans (ex biotin, vitamin K)
\*\*these unique biochemical pathways are good targets for antibiotics (antimicrobials)
105
gram-negative vs gram-positive bacterial cell envelopes
GRAM-NEGATIVES: thin, densely woven cell wall, plus an outer membrane attached to cell wall
GRAM-POSITIVES: thicker, less dense cell wall , with no outer membrane
106
LB media
- most widely used medium in bacteria labs
- main ingredients; casein, yeast extract, NaCl
107
Koch's Postulates
*rigorous way to demonstrate causation between microbe and infection*
1-find agent in diseased population/tissue
2-isolate agent & grow it in pure culture
3-cause disease by inoculating purified agent into animals
4-reisolate agent from experimentally infected animals
108
Gram-positive rods
spore formers: bacillus, clostridium
corynebacterium
listeria
109
Growth/Division of Bacteria
- bacteria multiply by binary fission
- extraordinary metabolic efficiency (achieved by tight control & coordination of enzymatic activities & gene expression)
e coli grows by elongation, then septation, then binary fission
110
transformation
(process of horizontal gene transfere between organisms)
- agent: DNA
- organism takes up naked DNA from its environment & integrates it into its genome
\*\*this only occurs in naturally competent bacteria
111
major routes that bacteria take to encounter/enter a host:
- via contaminated water supplies \*fecal/oral transmission)
- infectious aerosols \*from nasal cavity to oral cavity)
- arthropod vectors
112
Systemic Inflammatory Response Syndrome (SIRS)
alteration in pulse, temp, respiratory rate, WBC
SIRS+ infection --\> sepsis
113
granuloma
confinement of infection initiated by macrophages
114
surface antigens of gram negative enteric bacteria
- K-antigen found in capsule
- O-antigen
- H-antigen found in flagellum
\*\*these variable surface structures are helpful for classification of bacteria
115
clinical sequelae of sepsis
1-edema: lowers BP, reduces perfusion of heart
2-disseminated IV coagulation, resulting in hemorrhage-- reducing blood volume & further contributing to shock
116
how does vancomycin affect bacterial cell walls?
- inhibits the growth of the glycan chain of peptidoglyan in the cell wall
- rather than inhibiting an enzyme, it binds to the terminal D-alanine and inhibits growth of the bacteria
117
what mechanisms facilitate horizontal gene transfer?
transposition
recombination
118
horizontal gene transfer in bacteria
-method that antibiotic resistance can arise
**processes to move DNA WITHIN an organism**
- homologous recombination
- transposition
**processes to move DNA between organisms**
- transformation
- conjugation
- transduction (generalized & specialized)
119
profile of an ideal antibiotic
- high therapeutic index
- acid-stable (so can take it PO)
- absorbed in gut
- penetrates all body compartments
- not metabolized rapidly
- slowly excreted
- no side effects
- B-lactams are closest to perfect: high therapeutic index, low toxicity
120
what is the first host defense that bacteria encounter?
innate immunity
(every pathogen has to overcome innate immunity)
121
how does bacitracin affect bacterial cell walls
- bacitracin inhibits recycling of bactoprenol (lipid carrier) to the monophosphate in peptidoglycan frowth
- bacitracin binds to the metabolite, inhibiting further bacterial growth
122
lipopolysaccharide (LPS)
- forms the outer leaflet of the outer membrane of gram negative bacteria
- not found in animal cells
- aka "endotoxin" because it activates immunity
- structure: polysaccharide (O-antigen), attached to core oligosaccharide, with Lipid A tails
123
normal flora
-microbes which normally colonize healthy humans
(whereas pathogens are microbes which cause disease)
- some members of normal flora can cause disease
- most of normal flora bacteria are starved for nutrients at any given time
124
molecular methods used to ID DNA from bacteria
- MALDI-TOF: matrix assisted laser desorption ionization time of flight mass spec (uses presence of small molecule metabolites for identification, can only be used with cultured isolate)
- PCR: polymerase chain reaction; can identify species, does not require culture, used to amplify nucleic acids
- deep sequencing (next-gen & others)--looks at DNA sequence of many fragments
125
conjugation
(process of horizontal gene transfer between organisms)
- agent: plasmid
- plasmids are DNA molecules that replicate separately from bacterial chromosome (often circular)
- transfer of plasmids between bacteria, which encode functions require for transfer & replication
- then, transposition or recombination of plasmid occurs, passing the plasmid along
126
septic shock
sepsis + shock
(SIRS + infection + shock)
shock: organ hypoperfusion
- systemic manifestation of the local inflammatory response
127
how do mycoplasmas differ from other bacteria?
they lack peptidoglycan
-have sterols in cytoplasmic membranes to help strengthen membrane (partially compensating for lack of cell wall)
128
Bacteria Capsule Histo
129
sterilization
the killing of all organisms and infectious agent s in a preparation
130
important sites of tranlsation in bacteria
A site: aminoacyl-tRNA site
P site: peptidyl-tRNA site
E site: exit site
131
pili and fimbriae
protein protrusions from the surface of bacteria
-function: adherence, allowing bacterium to adhere to surfaces
132
harmful effects of normal flora
- antibiotic resistance
* -resistance determinants can be carried on single plasmids or transposons*
* -enteric bacteria exchange genes continually with each other & environment*
* -pathogens can acquire resistance determinants via occasional contact with enterics or environment*
- corrosive metabolic products
- ptoential to cause disease (opportunistic pathogens that get to a site where they shouldnt be)
133
resistance genes (generally originating in the environemnt) are transferred to pathogesn by three mechanisms...
transformation
conjugation
transduction
134
what is the most important factor to beat germs?
sanitation
(then vaccination, then antimicrobial therapy)
135
IgA Protease
-some bacteria secrete IgA protease, which cleaves IgA that is part of the adaptive immunity in sMALT cells
136
presenting signs of sepsis
- temp greater than 38C or less tahn 36C
- HR \> 90bpm
- Respiratory Rate \>20bpm
- WBC: \>12k or \<4k
- signs of infection
137
what staining procedure is used for visualizing mycobacteria?
acid-fast
138
Beta Lactam Antibiotics
- inhibit transpeptidation of peptidoglycan in bacterial cell wall
- classified because they contain a B-lactam ring
- irreversible inhibitors by covalently bonding; serve as a substrate mimick
139
how is drug resistance to mycobacterium tuberculosis caused?
ALL by mutation (because m. tuberculosis does not acquire DNA from its environment)
-therefore, TB treated with a cocktail of abx
140
predominant mechanism of how antibiotic resistnace occurs
spontaneous mutation
-mutation that makes a drug bind less strongly (disrupts the drug binding site but not the activation site)
141
spores
formed by sepcies of Clostridium & Bacillus (gram positive rods)
- single spore produced within parent cell
- spores have NO metabolic activity
- resistant to: heat, radiation, toxic chemicals, dessication
142
what mediates transcription in bacteria?
RNA polymerase
143
2 generalizations about metabolic requirements of bacteria
- all require reduced carbon & nitrogen for growth
- all derive energy from organic substrates by fermentation or oxidation with oxygen
(they are chemoheterotrophs)
144
membrane disrupting toxins
(exotoxins that act extracellularly)
- can kill phagocytes
- used by some intracellular bacteria to escape from phagosome & enter host cytoplasm
- often obligate anaerobes, trying to create anaerobic environment by digesting tissue
ex) alpha toxin of c. perfringens (gas gangrene)
145
abscess
-confinement of infection initiated by neutrophils
146
selective media
-lab media that contains (in addition to nutrients) cmpds that specifically inhibit the growth of one set of organisms, permitting detection of another set)
147
when treating a patient with bacterial infection, what are the 2 main lab science questions ?
1- which bacterium is it?
2- to which antibiotics is it susceptible?
148
bacterio-cidal drugs
-kills the bacteria (reduces the viability of the culture)
149
bacteremia
bacteria in th eblood
150
homologous recombination
(process that moves DNA within an organism)
-2 homologous pieces of DNA "cross over"
151
how bacteria overcome mucosa defense
- flagellae: promote motility
- fimbriae & pilli: adhesive structures so that bacteria can adhere to epithelium
- sloughing epithelium (*bordetella pertussis)*
152
chocolate agar
-sheep RBCs heat to 56 degree C a+ standard agar
153
areas of the body where some bacteria is present
-small bowel, trachea, stomach
154
Gram positive bacteria (structure)
- teichoic acid is principal structural component of layers beyond the cell wall (mostly linked to peptidoglycan)
- lack of outer membrane makes gram positives more susceptible to many abx (especially glycopeptides and lipopeptides)
155
exotoxin vs endotoxin
- endotoxin: intrinsic bacterial structure that can induce immunopathology (ex LPS)
- exotoxin: other secreted bacterial products that induce pathology (can cause disease in the absence of infection; symptoms can persist after abx treatment)
156
5 main categories of germs
bacteria
viruses
fungi
protozoa
helminths
157
biofilms
- population of bacteria embedded in an adherent layer of glycocalyx (often important to infectious processes)
- facilitates spread of infection & protects embedded bacteria from antibodies & phagocutes
158
host defenses at epithelial surfaces
- skin: physical barrier, inhospitable environment, salt
- mucosa: clearance of bacteria by physical flow, barrier, antibacterial secretions, mucosa-associated lymphoid tissue (MALT) produces secretory IgA (part of adaptive immune ressponse)
