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Intro, Overall Divisions, and Staphylococcus


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5 groups of human infectious diseases
Bacteria, fungi, protozoa, helminthes, viruses
3 Shapes of Bacteria
Cocci, bacilli, spirochetes
Arrangements of Cocci, ex.
Diplococci: Neisseria, chains: Strep, clusters: Staph
Smallest cell
Difference btw pro and euk cell wall
General dif btw Gram – cell wall and Gram + cell wall
-: Thin peptidoglycan layer, periplasmic space, outer membrane. + thick peptidoglycan layer, no outer membrane, (lipo)teichoic acid
Dif btw lipo- and teichoic acid
Lipo goes down to cell membrane, teichioic in wall
Gram – cell wall characteristics
Endotoxin LPS (Lipid A), periplasmic space (beta-lactamases), porins, O specific side chains
How does Lipid A cause shock
Released from dying bacteria, induces release of cytokines
LPS is to gram – as ______ is to gram +
Teichoic acid. (both can induce TSS)
Parts of LPS and what they do
Lipid A (induces fever/hypotension), O antigen: used for lab ID
Functions of peptidoglycan
Rigid support, protects against osmotic pressure
Detailed morphology of Staph, strep, strep pneumoniae, Neisseria Bacillus, Salmonella, Corynebacterium, Fusobacterium, Vibrio, Borrelia, Treponena
Clusters, chains, pairs w/pointed ends, kidney bean pair, rod w/square ends, rod w/rounded ends, club shaped, fusiform, comma-shaped, relaxed coil, tightly coiled
Enzyme in peptidoglycan formation. Drug interaction?
Transpeptidase, penicillins and cephalosporins inhibit this
Describe mycobacterium cell wall and staining characteristics
Mycolic acid à acid-fast stain. Don’t stain in gram stain
What human enzyme kills bacteria, where is it, how does it work?
Lysozymes: tears, secretions. Cleaves peptidoglycan
Difference btw human/bact cell membrane
Sterols in humans
Gram + color, - color
Purple. Pink.
Steps in gram staining
Thin film of suspension. Fix w/methanol. Flood w/crystal violet. Add iodine. Decolorize with alcohol. Flood w/counterstain. Rinse excess stain off
Describe bacterial chromosome(s)
Single, circular chromosome + plasmids
What info do plasmids carry? Transposons?
Plasmids: Antibiotic resistance, exotoxins, Transposons: antibiotic resistance genes
What are plasmids?
Extrachromosomal DNA
Role of capsule, composition (w/exception)
Antiphagocytic, polysaccharide, exception: anthrax (D-glutamic acid)
Describe 2 fxns of pili
Attachment, sex (conjugation)
Describe fimbraie
Adhesion protein
Dif btw flagella and fimbraie/pili
Flagella have directed movement
How to flagella move. Define: monotrichous, amphitrichous, peritrichous, lophotrichous
Rotate. One flagella, two. Flagella coming out all over. Tuft of flagella
Describe motility of spriochete
Flagella-like structure interwoven in spiral. Undulating motion
What is glycocalyx. 2 kinds. What does it do?
Gel like coating outside cell. Capsule and slime layer. Attaches bacteria to cells and prostheses
Function of: inclusion bodies, nucleoid, ribosomes, mesosome
Stored nutrients for later use. Location of bacterial chromosomes. Site of protein synthesis. Plasma membrane that fold into cytoplasm to increase surface area
Why do spores form? How does form change? Killed by boiling? Any way to kill? Metabolically active?
Lack of nutrients. Thick keratin-like coat. Survive for many years. No. Only at 121 degrees for at least 15 min. no.
How do bacteria reproduce?
Binary fission
Fastest replicating bactera
Clostridium perfringens
#1 cause of diarrhea in US
Dif btw exotoxin and endotoxin
Exotoxins are extraceullar proteins
4 phase of bacterial growth cycle. describe
Lag (incorporation of nutrients), log (exponential growth), stationary (equil btw death and new bacteria), death
Dif btw aerobes, anaerobes, facultatives, microaerophilic in terms of enzymes. What do enzymes do
Aerobes and facultatives have superoxide dismutase and catalase (break down toxic products of O2 use)
T or F bacteria are haploid
2 processes to transfer DNA WITHIN bacteria
Transposons and programmed rearrangements
Medical importance of transposons. and programmed rearrangments
Transposons: carry antibiotics resistance genes. Programmed rearrangments: evade immune system by putting new proteins (antigens on cell surface)
3 processes to transfer DNA btw bacteria
Conjugation, transduction, transformation
Describe conjugation. What is required?
Donor sex pilus attaches to recipient. DNA moves along sex pilus. Requires F plasmid. At the end, both have a copy of transferred genetic material
Describe transduction. What is lysogenic conversion
DNA transferred via bacteriophage. If new protein made: lysogenic conversion
Describe transformation. 2 ways it can happen.
DNA itself transferred: via dying cells or experimentally
Normal flora of skin
S. epidermidis, Propionibacterium, Peptococcus, Candida
How can candida cause disease
IV drug use, gets into bloodstream. Endocarditis
How can S. epidermidis cause disease
It gets on prostethic devices: heart valves, joints
Major normal flora of the nose
Staph aureus
3 normal flora of throat and bacteria they inhibit
Viridans strep (Strep pyogenes), Neisseria spp (N. meningitides), S. epidermidis (S. aureus)
Normal flora of mouth – what problem do they cause.
Viridans (Strep mutans): dental caries. Most common cause of subacute infective endocarditis. Anaerobes (Bacteriodes, Fusobacterium, Clostridium, Peptostreptococcus): cause lung abscess if aspirate
Major site of bacteria in the body
What is the normal role of E. coli, aberrant role
Normal GI flora, leading cause of UTI
Normal flora of GI
E. coli, Bacteriodes fragilis, Enterococcus faecalis, Pseudomanas aeruginosa
What extraintestinal disease to these case: B. fragilis. E. faecalis. P. aeruginosa
Peritonitis following trauma, appendicitis, diverticulitis. UTI, endocarditis. Various nosocomial infections
Role of antibiotics in normal GI flora
Can wipe out normal flora and allow rare bacteria to overrun (clostridium difficile)
Major normal flora of GU tract, what happens when it’s suppressed
Lactobacillus – keeps pH low.. Candida infection
Bacteria on skin around GU tract
S. saprophyticus
Bacteria that can infect urine as it comes out urethra
S. epidermidis, coliforms, diphtheroids, nonhemolytic streptococci
Bacteria around urethra of women and uncircumcised men
Mycobacterium smegmatis
Female urethra can get bacteria from what area
Fecal flora
Define colonization resistance and give an example
Normal flora take up receptor sites so pathogens can’t attach. Ex. Viridans strep on throat prevent GAS from binding
Does E. coli produce a vitamin. If yes, what
Yes, vitamin A
Diseases caused by Staphlyococcus aureus
Abscesses, various pyogenic infections (endocarditis, septic arthritis, osteomyelitis), food poisoning, TSS, nosocomial pneumonia, septicemia, surgical-wound infection. Meningitis, UTI, abscess formation of any organ
T or F. gram + cocci are motile
T or F. gram + cocci do not form spores
Gram, catalase, coagulase status of staph spp
Staph aureus: all +, S. epidermidis, saprophyticus: coagulase -
What is catalase, why is it good for bacteria
Degrades H2O2 into O2 and H2O, prevents peroxide from microbicidal activity of letting neutrophils kill
What is coagulase
Causes plasma to clot by activating prothrombin à thrombin
T or F. s. aureus ferments mannitol
T of F. s. aureus is beta hemolytic
90% of what bacteria have beta-lactamase. What is that?
s. aureus. Degrades many penicillins
How can s. aureus be resistant to beta-lactamase resistant penicillin
Changes in penicillin binding protein
6 important cell wall components and antigens
Protein A, teichoic acids, polysaccharide capsule, phage surface receptors, microcapsule, peptidoglycan
Describe protein A
Bind Fc portion of IgG, antiphagocytic
Describe teichoic acid in staph
Adherence to mucosal cells + play a role in septic shock
Describe role of peptidoglycan in strep
Endotoxin-like properties
Role of staph as normal flora (3 kinds of staph)
s. epidermidis: skin + hair follicles. S. aureus: nose. S. saprophyticus: skin around GU tract
T or F. S. aureus disease thrives in heavily contaminated environment and immunocompromised people.
Typical lesion of s. aureus
What happens to abscesses
Central necrosis and drain to the outside
Important predisposing factor in s. aureus infection
Foreign bodies (sutures, IV catheters)
3 clinically important exotoxins in s. aureus
Enterotoxin, toxic shock syndrome toxin, exfoliatin
Describe what enterotoxin does and clinical manifestations
Superantigen: release of IL-1 from macros, IL-2 from T helper cells. food poisoning. Prominent vomiting (signals enteric n.s. to stimulate vomiting center in brain) + watery, non-bloody diarrhea.
Heat resistance, stomach acid, jejunum enzymes - reaction of enterotoxin
Fairly heat resistant, resistant to stomach acid, jejunum enzymes
Describe toxic shock syndrome toxin
Causes toxic shock, esp in women w/tampon, nose tampon. Superantigen à IL-1, IL-2, TNF released
Describe exfoliatin
Causes “scalded skin syndrome”. Epidermolytic.
What is alpha toxin?
Kills leukocytes à skin necrosis and hemolysis.
Name some virulence enzymes in s. aureus
Coagulase, fibrinolysin, hyaluronidase, proteases, nucleases, lipases
Proteins that disable host immunity in s. aureus
Protein A, coagulase, hemolysins, penicillinase
Proteins tunneling through tissue in s. aureus
Hyaluronidase, staphylokinase, lipase
Pathogenic mechanisms of s. aureus
Toxins and inflamm due to multiplying in tissues
T of F. All spp of staph produce exotoxin
F: S. epidermidis and S. saprophyticus don’t – also means no food poisoning or septic shock
What are 2 divisions of clinical manifestations of s. aureus
Pyogenic and toxin-mediated
Pyogenic diseases of s. aureus
Skin infections, septicemia, endocarditis (esp R. sided tricuspid in IV drug uses), osteomyelitis, arthritis, postsurgical wound infection, pneumonia, abscesses
What does staph pneumonia often lead to?
Empyema and lung abscess
Toxin-mediated diseases of s. aureus
Food poisoning – ingest enterotoxin. TSS, scalded skin syndrome
Clinical manifestation of TSS
Hypotension; macular, sunburn like rash, 3+ organ involvement
Clinical manifestation of scalded skin syndrome. Age group often affected
Fever, large bullae, erythematous rash, skin slough, serous fluid exudes, electrolyte imbalance, skin and hair loss. Recovery takes 7-10 d. young children
Diseases caused by S. epidermidis
Infect protheses, neonatal sepsis, peritonitis in renal pts with catheter, cerebrospinal fluid shunt infection
What is the most common cause of cerebrospinal fluid shunt infection
s. epidermidis
What determines if S. epidermidis adheres well to prostheses?
Presence of glycocalyx
Diseases caused by S. saprophyticus
Top two causes of community acquired UTI
E. coli, S. saprophyticus
Lab Dx: gram, culture, coagulase, mannitol
+. golden-yellow, beta hemolytic. +. +
Lab dx: culture of coagulase - staph
White colonies, non hemolytic
Role of novobiocin in staph
s. epidermidis sensitive, s. saprophyticus not
Bacteriophages and lab dx for staph
Staph can be divided into groups based on their lysis
T or F. 90% of s. aures resistant to penicillin
Why are most s. aureus resistant to penicillin?
Contain beta lactamase
what meds are some s. aureus resistant to?
Penicillin, methicillin, nafcillin, partial vancomycin
Tx of staph toxic shock syndrome
Correct hypotension w/fluids. Pressor drugs, inotropes, beta lactamase resitant penicillin.
Topical antibiotic for staph
Definition of tolerance
Bacteria can’t grow but not killed by med
Treatment of abscesss
Surgical drainage
T or F. S. epidermidis is highly resistant to antibiotics
T. use vancomycin +/- another drug. Remove prosthesis
Prevention of staph infections
Hygiene!!!, remove shedders from high-risk areas, peri-op antibiotics
Are viruses cells
What is the only group that has a nucleus
Which group has DNA or RNA
Describe chromatin of euk, arch, pro and viruses
Many, complexed w/histones. Single loop. single, circular chromatin + plasmids, none
Describe ribosomes of euk, arch, pro, viruses
80S, 70S, 70S, none
Which group has mitochondria
Euks only
Outer surface of euk, arch, pro, viruses
Euk: cell membrane w/sterols. Chitin wall, ergosterol. Arc: glycerol/isoprene derivatives. Pro: peptidoglycan + cell membrane, maybe capsule. Viruses: naked protein capsid + lipoprotein envelope
Motility: euk, arc, pro, viruses
Flagella, cilia, pseudopods. Flagella, flagella. None
Difference btw bacteriostatic and bactericidal
Inhibits bacterial growth (host defenses need to kill). Kill bacteria.
Reasons for antibiotic failure
Delay in dx, tx. Wrong dx. Errors in susceptibility testing. Inadequate concentration of bacteria at infection site. other factors at site. immunocompromised pt. superinfection. resistance.
How can you distinguish btw N. gonorrhea and N. meningitidis
Fermentation of glucose or maltose
How you distinguish E. coli from Shigella and Salmonella
Fermentation of lactose

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