Bacteriology Flashcards
Peptidoglycan
Gives rigid support
Protects against osmotic pressure
Composed of sugar backbone with peptide side chains cross linked by transpeptidase
Cell wall
Gram positive organisms only
Major surface antigen
Peptidoglycan for support
Lipoteichoic acid within induces TNF and IL-1
Outer membrane
Gram negative organisms only
Major surface antigen
Site of endotoxin (lipopolysaccharide LPS)
Contains lipid A, which induces TNF and IL-1
Periplasm
Space between the cytoplasmic membrane and the outer membrane in gram-negative bacteria
Contains many hydrolytic enzymes including beta lactamases
Capsule
Protects against phagocytosis
Contains polysaccharide or D-glutamate in Bacilius anthracis
Pilus/fimbria
Mediate adherence of bacteria to cell surface
Sex pills forms attachment between 2 bacteria during conjugation
Contains glycoprotein
Spore
Resistent to dehydration, heat, and chemicals
Contains keratin-like coat, dipicolinic acid, and peptidoglycan
Plasmid
Contains a variety of genes for antibiotic resistance, enzymes, and toxins
Contains dsDNA
Glycocalyx
Mediates adherence to surfaces, especially foreign bodies such as indwelling catheters
Contains polysaccharides
Gram stain
Gram positive: purple/blue
Gram negative: red/pink
Limitations: These Microbes May Lack Real Color Treponema: too thin Mycobacteria: high lipid content Mycoplasma: no cell wall Legionella: intracellar Rickettsia: intracellar Chlamydia: intracellar
Giesma stain
Certain Bugs Really Try my Patience
Chlamydia Borrelia Rickettsiae Trypansomes Plasmodium
PAS stain
Stains glycogen, mucopolysaccharides
Used to diagnose Whipple’s disease (Troperyma whipplei)
Ziehl-Nellsen stain
Acid fast stain
Norcadia, Myobacterium
India ink stain
Cryptococcus neoformans
Silver stain
Fungi (pneumocystis)
Legionella
Helicbacter pylori
Obligate aerobes
Use an O2 dependent system to generate ATP
Nagging Pests Must Breathe
Nocardia
Pseudomonas aeruginosa
MycoBacterium tuberculosis
Obligate anaerobes
Lack catalase and/or superoxide dismutase and are thus susceptible to oxidative damage
Generally foul smelling, difficult to culture, and produce gas in tissue (CO2 and H2)
Anaerobes Cant Breath Air
Clostridum
Bacteriodes
Actinomyces
Anaerobes are normal flora in GI tract but pathogenic every where else
AminOglycosides are ineffective against anaerobes because these antibiotics require O2 to enter ingot he bacterial cells
Obligate intracellular bugs
Cannot make own ATP
Stay inside when it is Really Cold
Rickettsia
Chlamydia
Facultative intracellular
Some Nasty Bugs May Live FacultativeLY Salmonella Neisseria Brucella Myobacterium Listeria Francisella Legionella Yersinia
Encapsulated bacteria
Capsules serve as an antiphagocytic virulence factor
Capsule + protein conjugate often serves as an antigen in vaccine
Often opsonized and then cleared by spleen, aslplenics have a decreased opsonizing ability and are at risk for severe infection by encapsulated organisms
SHiNE SKiS Streptococcus pneumoniae Haemophilus influenzae type B Neisseria menigitidis Escherichia coli Salmonella Klebsiella pneumoniae group B Strep
Catalase-positive organism
Catalase degrades H2O@ before it can be converted to microbicidal products by the enzyme myeloperoxidase
Patients with chronic granulomatous disease (NADPH oxidase deficiency) have recurrent infections with catalase positive organisms
You need PLACESS for your "cat"s Pseudomonas Listeria Aspergillus Candida E. coli S. aureus Serratia
Urease-positive bugs
Can digest urea
CHuck norris hates PUNKSS Cryptococcus H. pylori Proteus Ureplasma Nocardia Klebsiella S. epidermidis S. saprophyticus
Pigment-producing organisms
Actinomyces israelii: produces yellow “sulfur” granules which are composed of filaments of bacteria: Israel has yellow sand
S. aureus: yellow pigment, aureus == gold (Latin)
Pseudomonas aeruginosa: blue/green pigment, Aeurgula is green
Protein A
Virulence factor
Binds Fc region (immunoglobulin region binding to cell surface receptors) of IgG
Prevents opsonizaiton (mark by antibody for ingestion) and phagocytosis
Ex: S. aureus
IgA protease
Virulence factor
Enzyme that cleaves IgA
Ex: S. pnemoniae, H. influenza B, Neisseria, (SHiN)
M protein
Virulence factor
Helps prevent phagocytosis
Ex: group A Strep
Exotoxin
Secreted by certain species of gram positive and gram negative bacteria
Composed of polypeptide
Genes located on plasmid or bacteriophage
High toxicity (fatal dose on the order of 1 microgram)
Induces high-titer antibodies called antitoxins
Toxoids can be used as vaccines
Heat unstable, destroyed at 60C, except for staph enterotoxin
Ex: tetanus, botulism, diphtheria
Endotoxin
Present on outer cell membrane of most gram negative organisms
Composed of lipopolysaccharide (LPS), structural part of bacteria when lysed
Genes located on bacterial chromosome
Low toxicity (fatal dose on the order of hundred of micrograms)
Clinically demonstrate fever, shock, DIC
Induces TNF, IL-1, and IL-6
Poorly antigenic and thus no vaccines available
Heat stable at 100C for 1 hr
Ex: menigococcemia, sepsis by gram-negative rods
Transformation
Ability to take up naked DNA (i.e. from cell lysis) from environment (also know as competence)
Feature of many bacteria especially SHiN (IgA protease +)
Any DNA can be used
Adding deoxyribonuclease to environment will degrade naked DNA and therefore preventing transformation
Conjugation
F+ x F-:
F+ plasmid contains genes required for sex pills and conjugation
Bacteria without this plasmid are termed F-
Plasmid (dsDNA) is replicated and transferred through pious from F+ cell to F- cell
No transfer of chromosomal genes
Hfr x F-:
F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high frequency recombination cell
Replication of incorporated plasmid DNA may include some flanking chromosomal DNA
Transfer of plasmid AND chromosomal DNA
Transduction
Generalized:
A “packaging” event
Lytic phages infect bacterium, leading to cleavage of bacterial DNA
Parts of bacterial DNA may become packaged in viral capsid and phage subsequently infect another bacterium and transfer these bacterial genes
Specialized:
An “excision” event
Lysogenic phage infects bacterium
Viral DNA becomes incorporated into bacterial DNA
When phage DNA is excised, flanking bacterial gene may be excised as well
Bacterial DNA then packaged into phage capsid and phage infects new bacterium after lytic cycle
Novobiocin
On the office’s “staph” retreat, there was NO StRESs
S.saprophyticus is resistant to novobiocin while S.epidermidis is sensitive
Optochin
OVRPS(overpass)
S.viridin is resistant to optochin while S.pneumoniae is sensitive
Bacitracin
B-BRAS
Group B strep is resistant to bacitracin while group A strep is sensitive
Alpha hemolytic
Partial hemolysis: green appearance in blood culture
S.pneumoniae, S.viridin
Beta hemolytic
Complete hemolysis: clear appearance in blood culture
S. aureus, S. pyogens (GAS), S agalciae (GBS), Listeria
Gamma hemolytic
No hemolysis: no change
Enterococcus, group D strep
Staphylococcus aureus
Gram-positive cocci in Clusters
Protein A producing (binds Fc-IgG), inhibiting complement activation and phagocytosis
Causes:
Inflammatory disease: skin infections, organ abscesses, pneumonia (often after influenza virus), endocarditis, and osteomyelitis
Toxin mediated disease: toxic shock syndrome (TSST, superantigen that binds to MHC II and T-cell receptor, resulting in polyclonal T cell activation and presents as fever, vomitting, and eventually shock and end organ failure), rapid onset food poisoning (due to ingestion of preformed toxin not destroyed by cooking)
MRSA: nosocomial and community acquire infections
Staphylococcus epidermidis
Gram positive cocci
Infects prosthetic devices and intravenous catheters by producing biofilms
Component of normal skin flora
Contaminates blood cultures
Staphylcoccus saprophyticus
Gram positive cocci
Second most common cause of uncomplicated UIT in young women
Streptococcus pneumoniae
Gram positive, lancet shaped diploccoci
Most common cause of MOPS
Meningitis, Otitis media (children), Pnemonia, Sinusitis
Strepcocci viridins (s. mutans, s.sanguinis)
Gram positive
Normal flora of the oropharynx and cause dental caries (mutans) and subactue bacterial endocarditis at damaged valves (sanguinis)
Streptococcus pyogenes (GAS)
Gram positive
Secrete streptolysin O, a protein that degrades cell membranes that leads to lyses of RBCs
Secrete exotoxin A that bring MHCII and TCR in proximity outside of antigen binding site to cause overwhelming release of IFN and IL and leave to toxic shock syndrome (fever, rash, shock)
Causes:
Pyogenic: pharyngitis, cellulitis, impetigo
Toxigenic: scarlet fever, toxic shock-like syndrome, NEC
Immunologic: rheumatic fever, acute glomerulonephritis
Antibodies against toxins (ASO) titer detects recent S. progenies infection for rheumatic fever
JONES criteria for rheumatic fever Joints: polyarthritis Oheart: carditis Nodules: subcutaneous Erythema marginatum (pink rings on trunk and inner surfaces of limbs) Sydenham chorea (movement disorder)
Streptococcus agalacitae (GBS)
Gram positive
Group B for Babies
Mostly colonizes vagina
Causes meningitis, pnemonia, and sepsis
Screen pregnant women at 35-37 weeks and treat patients with positive results w/ intrapartum penicillin prophylaxis
Enterococci (GDS)
Gram positive
Normal colonic flora that are penicillin G resistant and causes UIT, biliary tract infection, and subacute endocarditis (usually following GI/GU procedures)
VRE (vancomycin resistant enterococci) are an important cause of nosocomial infection
Streptococcus bovis
Gram positive
Colonizes the gut
Can cause bacteremia and subacute endocarditis in colon cancer patients
Corynebacterium diphtheria
Gram positive rods w/ metachromatic granules
Causes diphtheria via exotoxin encoded by beta-prophage
Diphtheria toxin inactivate elongation factor 2 and can lead to pharyngitis with pseudomembranes in throat and severe lymphadenopathy (bull neck)
Toxoid vaccine prevents diphtheria
Clostridia tetani
Gram positive spore forming
Produces tetanospasmin, an exotoxin causing tetanus.
Toxin is a protease that cleaves releasing proteins for neurotransmitters (SNARE) and subsequently blocks GABA release from Renshaw cells in spinal cord, causing spastic paralysis
Clostridia botulinum
Gram positive spore forming
Produces a preformed, heat labile toxin that inhibits ACh release at the neuromuscular junction by cleaving SNARE, causing botulism
In adults, disease is caused by ingestion of preformed toxin
In babies ingestion of spores in honey causes disease –> floppy babe syndrome (floppy paralysis)
Clostridia perfringens
Gram positive spore forming
Produces alpha toxin, a phosphlipase that degrades tissue and cell membranes, leading to myonecrosis (necrosis of muscle), gas gangrene, and hemolysis
Clostridia difficile
Gram positive spore forming
Produce 2 toxins
Toxin A, binds to the brush border of the gut
Toxin B, cytotoxin, causes cytoskeletal disruption via actin depolymerization
Often 2ndary to antibiotic use, especially clindamycin or ampicillin
Diagnosed by detection of one or both toxins in stool
Treatment: metronidazole or oral vancomycin. Fecal transplant for recurring cases
Bacillus anthracis
Gram positive spore forming
Only bacterium with a polypeptide capsule (D-glutamate)
Produce toxin anthrax that mimics adenylate cyclase
Cutaneous anthrax:
Boil like lesions, ulcer with black eschar (painless, necrotic) with surround edema, uncommonly progress to bacteremia and death
Pulmonary anthrax:
Inhalation of spores, flu like symptoms that rapidly progresses to fever, pulmonary hemorrhage, mediastinitis, and shock
Woolsorter’s disease
Inhalation of anthrax spores from contaminated wool
Bacillus cereus
Gram positive spore producing
Causes food poisoning as spore survives cooking and enterotoxin formation occurs–> reheated rice syndrome
Listeria monocytogenes
Gram positive
Only gram positive organism to produce LPS
Acquired by ingestion of unpasteurized dairy products and deli meats, via transplacental transmission, or by vaginal transmission during birth
Can cause amnionitis, septicemia, and spontaneous abortion in pregnant women
Can cause granulomatosis, neonatal meningitis, meningitis in immunocompromised patients
Treatment: ampicilin in infants and immunocompromised patients
Actinomyces
Gram positive anaerobe forming long branching filaments resembling fungi
Not acid fast
Normal oral flora
Causes oral/facial abscesses that drain through sinus tracts, forms yellow “sulfur” granules
Treat with penicillin
Norcardia
Gram positive anaerobe forming long branching filaments
Weakly acid fast
Found in soil
Causes pulmonary infections in immunocompromised and cutaneous infections after trauma in immunocompetent
Treat w/ sulfonamides
Myobacterium tuberculosis
Acid fast
Resistant to multiple drugs
TB symptoms include fever, night sweats, weight loss, and hemoptysis
Cord factor in virulent strains inhibits macrophage maturation and induces release of TNFalpha
Sulfatides (surface glycolipids) inhibit phagolysosomal fusion
Primary TB:
Infection –> nonimmue host (usually children) –> TB resides in hilar nodes –> heals by fibrosis, progressive lung disease, severe bacteremia, and/or pre allergic lymphatic or hematogenous dissemination –> dormant tubercle bacilli in several organs –> extra pulmonary TB (CNS meningitis, vertebral Pott disease)
Secondary TB:
Infection –> partially immune hyper sensitized host (usually adult) –> reinfection/2ndary TB –> fibrocaseous cavitary lesions (usually upper lobes) –> reactivation of TB in lung –> extra pulmonary TB
Myobacterium avium
Acid fast
Causes disseminated non-TB disease in AIDS, often resistant to multiple drugs
Prophylactic treatment w/ azithromycin
Myobacterium leprae
Acid fast
Causes leprosy/Hensen disease, reservoir in US in armadillos
Lepromatous form: presents diffusely over the skin, with leonine (lion-like) facies and ins communicable, characterized by low cell-mediated immunity with a humoral Th2 response, “glove and stocking” loss of sensation due to skin and superficial nerve infection
Tuberculoid form: limited to a few hypoestehtic, hairless skin plaques, characterized by high cell-mediated immunity with a largely Th1 type immune response
Treatment: multiple drug therapy consisting of dapsone and rifampin for 6 months for tuberculoid form, dapsone and rifampine for 2-5 years for lepromatous form
Neisseria gonococci
Gram negative diplococci, ferment glucose
No polysaccharid capsule
No maltose fermentation
No vaccine (due to rapid antigenic variation of pilus proteins)
Sexually transmitted
Causes gonorrhea, septic arthritis, neonatal conjunctivitis, PID, and Fitz-Hugh-Curtis syndrome (complication of PID w. RUQ 2ndary to referred pain)
Condoms prevent sexual transmission
Erythromycin ointment prevents neonatal transmission
Treatment: ceftriaxone + azithromycin or doxycyclin for possible co-infection w/ chlamydia
Neisseria Meningococci
Gram negative diplococci, ferment glucose
Polysaccharid capsule
Maltose fermentation
Vaccine available (not for type B)
Transmitted through respiratory and oral secretions
Causes menigococcemia and meningitis, Waterhouse-Friderichsen syndrome (adrenal failure due to hemorrhage)
Prevention w/ rifampin, ciprofloxain, or ceftriaxone for close contacts
Treatment w/ ceftriaxone or penicillin G
Haemophilus influenzae
Gram negative, small rod
Aerosol transmission
Most invasive disease caused by capsular type B
Nontypable strains cause mucosal infections (otitis media, conjunctivitis, bronchitis)
Culture on chocolate agar requires factor V (NAD+) and X (hematin) for growth
HaEMOPhilus causes: Epiglottis (cherry red in children) Meningitis Otitis Media Pnemonia
Dose not cause flu
Treat mucosal infection w/ amoxicillin or augmenting
Treat meningitis w/ ceftriaxone
Rifampin prophylaxis in close contacts
Legionella pneumophila
Gram negative rod
Gram stains poorly, use silver stain
Grow on charcoal yeast extract culture w/ iron and cysteine
Detected clinically by presence of antigen in urine
Aerosol transmission from environmental water source (air conditioning, hot water tanks)
Labs often show hyponatremia
Treat w/ macrolide or quinolone
Causes Legionnaires’ disease and Pontiac fever
Pseudomonas aeruginosa
Gram negative rod
Blue green pigment w grape like odor
Produces exotoxin A, which inactivates EF2 and leads to host cell death
PSEUDOmonas associated with would and burn infections, Pneumonia Sepsis External otitis (swimmer's ear) UTI Drug use Diabetic Osteomyolitis
Chronic pneumonia caused by pseudomonas in cystic fibrosis patients is associated w/ biofilms
Ecthyma gangreosum
Caused by pseudonomas
Rapidly progressive, necrotic cutaneous lesions
Typically seen in immunocompromised patients
Treatment: amioglycosides + piperacillin
Enteroinvasive E. coli EIEC
Gram negative
Microbe invade intestinal mucosa and causes necrosis and inflammation, leading to dysentery (diarrhea w/ blood)
Clinical manifestation similar to shigella
Enterotoxigenic E. coli ETEC
Gram negative
Produces heat-labile (overactive adenylate cyclase, increased secretion) and heat-stable (overactive guanylate cyclase, decreased resorption) enterotoxins
No inflammation or invasion
Causes traveler’s diarrhea (watery)
Enteropathogenic E. coli EPEC
Gram negative
No toxins produced
Adheres to apical surface, flattens villi, prevents absorption
Causes pediatric diarrhea
Enterohemorrhagic E. coli EHEC
Gram positive
O157:H7 most common serotype
Produces shiga-like toxin (SLT) that inactivates 60S ribosome by removing adenine from rRNA. SLT also enhances cytokine release, causing HUS (triad of anemia, thrombocytopenia, and acute renal failure due to micro thrombi formed on endothelium damaged by toxin)
Unlike shigella, EHEC does not invade host cells
Klebsiella
Gram negative
Intestinal flora that causes 4As
Aspiration pneumonia in Alcholics and diabetics leading to Abscess in lungs and liver
Also causes nosocomial UTIs
Very mucoid colonies w/ red “currant jelly” sputum
Salmonella
Gram negative
Have flagella (salmon swim)
Can disseminate hematogenously
Have many animal reservoirs
Produce hydrogen sulfide
Antibiotics may prolong fecal excretion of organism
Invade intestinal mucosa and causes a monocytic response
Can cause bloody diarrhea
Does not ferment lactose
Shigella
Gram negative
Produces shiga toxin (ST), which inactivate 60s ribosome by removing adenine from rRNA, leading to GI mucosal damage and dysentary, ST also enhances cytokine release leading to HUS
No flagella
Cell to cell transmission; no heamtogenous spread
Only reservoirs are humans and primates
Does not produce hydrogen sulfide
Antibiotics shorten duration of fecal excretion of organisms
Invades intestinal mucosa and causes PMN infiltration
Often causes bloody diarrhea
Does not ferment lactose
Salmonella typhi
Gram negative
Causes typhoid fever
Found only in human
Characterized by rose spots on the abdomen, fever, headache, and diarrhea
Can remain in gallbladder and cause a carrier state
Campylobacter jejuni
Gram negative, comma or S-shaped
Major cause of bloody diarrhea, especially in children
Fecal-oral transmission through food such as poultry, meat, and unpasteurized milk
Common antecedent to Guillina-Barre syndrome and reactive arthritis
Virbrio cholerae
Gram negative, comma shaped
Produce profuse rice-water diarrhea via enterotoxin that permanently activates GCPR
Grows in alkaline media
Endemic to developing countries: Cholera
Yershina enterocolitica
Gram negative
Usually transmitted from pet feces such as puppies, contaminated milk, or pork
Causes mesenteric adenines that can mimic Crohns or appendicitis
Helicobacter pylori
Gram negative rod
Causes gastritis and peptic uclers (especial duodenal)
Risk factor for peptic ulcer, gastric adenocarcinoma, and lymphoma
Triple therapy: PPI + clarithromycin + amoxcilin/metronidazole
Leptospira interrogans
Gram negative spirochetes
Found in water contaminated w/ animal urine
Causes leptospirosis: flu like symptoms, jaundice, photophobia with conjunctival erythema, prevalent in surfers
Weil disease
Caused by leptospira, AKA icterohemorrhagic leptospirosis
Severe jaundice and azotemia from liver and kidney dysfunction, fever, hemorrhage, and anemia
Borrelia burgdorferi
Gram negative spirochetes
Causes Lyme disease
Transmitted by the tick Ixodes, natural reservoir is the mouse
Common in northeastern US Present as FAKE a key lyme pie Facial nerve palsy (typically bilateral) Arthritis Kardiac block (AV nodal block) Erythema migrans (targetoid)
Treatment: doxycycline, ceftriaxone in children
Treponema palldium
Gram negative spirochetes
Visualized w/ dark-field microscopy
Primary syphilis:
Localized disease presenting w/ painless chancre
Secondary syphilis:
Disseminated disease w/ constitutional symptoms, maculopapular rash, condylomata lata
Tertiary syphilis:
Gummas (chornic granulomas), aortitis, neurosyphilis (tabes dorsalis, general paresis), Argryll Robertson pupil
Serologic testing: VDRL/RPR, confirm w/ FTA-ABS
Treatment: penicillin G
Congenital syphilis:
Saber shins, saddle nose, CN VIII deafness
To prevent, treat mother w/ penicillin G in first trimester
Argyll Robertson pupil
Constricts w/ accommodation but is not reactive to light
“Prostitute pupil”: accommodates but does not react
VDRL false positives
VDRL nonspecific
False positives: Viruses (mononucelosis, hepatitis) Drugs, Rheumatic fever Lupus and leprosy
Gardnerella Vaginalis
Gram negative, pleomorphic rod
Causes bacterial vaginitis
I don’t have a clue why i smell fish in the vagina garden
Gray discharge w/ fishy smell
Associated w/ bacterial overgrowth, sexual activity, but not transmitted sexually
Clue cells, or vaginal epithelial cells covered w/ bacteria are visible under microscope
Treatment: metronidazole or clindamycin
Rickettsia rickettsii
Vector is tick
Causes Rocky Mountain Spotted Fever, occurs mostly in South Atlantic states
Classic triad of headache, fever, and rash (typically start at wrists and ankles and then spread to trunk, palm, and soles
Treat w/ doxycycline
Rickettsia typhi
Rash starts centrally and spreads out, sparing palm and soles
Treat w/ doxycycline
Coxiella burnetti
No anthropoid vector
Tick feces and cattle placenta release spores that are inhaled as aerosols causing Q fever and presents as pneumonia
Q fever is Queer in it it has no rash or vector
Treat w/ doxycycline
Chlamydia trachomatis
Gram negative
Cannot make own ATP, obligate intracellular organism causes mucosal infection in two forms: Elementary body (small, dense), Reticulate body
Causes reactive arthritis (Reiter syndrome), follicular conjunctivitis (type ABC), nongonococcal urethritis, and PID (type D-K)
Cytoplasmic inclusions seen on Giemsa or fluorescent antibody stained smear
Treatment: azithromycin or doxycyclin
Mycoplasma pneumoniae
No cell wall, not seen on gram stain
Atypical “walking” pneumonia (insidious onset, headache, nonproductive cough, patchy or diffuse interstitial infiltrate), more common in patients < 30 yrs old, frequent outbreaks in military recruits and prisions
Xray looks worse than patients
High titer of cold agglutinins (IgM)
Grow on Eaton agar
Treat w/ macrolide, doxycycline, or fluoroquinolone
