Bacteria Flashcards
define pathogen
micoorganism capable of causing disease
define opportunistic
rarely causes disease in immunocompetent individuals but can cause severe disease in those with weakened immune response
define bacteremia
bacteria in the bloodstream
define sepsis
systemic immune response to the infection
define septic shock
hypotension, organ dysfunction
- common deadly response to gram positive & negative infections
- high mortality rate
Define gram results
purple/blue = gram positive
- thick 2 layer cell wall
- no porin channel or endotoxin
- vulnerable to lysozyme & PCN
pink/red = gram negative
- thin 3 layer cell wall envelope with porin channel
- endotoxin-Lipid A
- resistant to lysozyme & PCN
Describe the coverage & MOA of Beta-Lactams
PCN, cephalosporins (3-5 gen), carbapenems
- inhibit cell wall synthesis
- cover gram negative bacteria
What are the 4 major morphologies of bacteria
- cocci: spherical
- bacilli: rod shaped
- spiral
- pleomorphic: lack distinct shape
can organize together to form pairs, clusters, chains, single bacteria with flagella
Describe some bench tests
used to further differentiate species
- coagulase test: differentiates staph species
- catalase tests: distinguishes staph v strep v enterococci
- oxidase: differentiates gram negative bacilli
- lancefield grouping: used for strep species
Describe some gram positive bacteria
Describe some gram negative bacteria
cocci
- neiserria
- moraxella diplococcus
spirochetes
- treponema pallidum
- borrelia
- leptospira
pleomorphic
- chlamydia
- rickettsia
bacilli/rods
- pretty much everything else (enterics & others)
Which bacteria is neither gram positive or negative?
Mycoplasma, no cell wall
What is referred to as walking pneumonia
mycoplasma pneumonia
- MC cause of atypical pneumonia
- low grade F, dry non-productive cough
- Tx with Azithromycin, doxy, or fluoroquinolone
What are some AEs of fluoroquinolones
QT prolongation, cartilage issues
Describe the difference between aerobic vs anaerobic bacteria
Obligate Aerobes
- uses oxygen
- breaks down oxygen with enzymes
Obligate anaerobes
- hates oxygen
- no enzymes to defend against oxygen
Facultative anaerobes
- aerobics
- ability to be anaerobic but don’t prefer it
Describe endotoxins
proteins released by some Gm+ and Gm- bacteria
describe neurotoxins
acts on nerves (paralysis
- tetanus, botulinum
describe enterotoxins
acts on GI tract (diarrhea)
- vibrio, e coli, campylobacter, shigella
describe pyrogenic endotoxins
lead to rash, fever, toxic shock
- staph aureus, GABHS
Describe tissue evasive endotoxins
allow bacteria to destroy tissues (GABHS)
Which abx lower seizure thresholds
cephalosporins
Describe a sterile site vs non-sterile site for cultures
differentiates if this is a true pathogen or part of the normal flora
- sterile: CSF, pleural fluid, pericardial fluid, synovial fluid, peritoneal fluid (where bacteria is not present usually)
- non-sterile: skin, oropharynx, nose, ears, eyes, throat, perineum
What to consider when interpreting a culture result
- coag negative staph (usually just staph epidermidis - skin contaminant from procedure)
- assess for WBCs, nitrites, leukocyte esterase in UA along with culture
- sputum culture with poor sensitivity & specificity
- squam epithelial cells present reduces likelihood that bacteria is pathogenic
What is the most common organism that causes UTIs
e coli
What are the 3 types of gram+ cocci
streptococcus chains, enterococcus chains, staphylococcus clusters
Describe the types of hemolysis in streptococci (classifications)
- Alpha-hemolytic: incomplete destruction of RBC (strep pneum, strep viridans)
- Beta-hemolytic: complete destruction of RBC (strep pyogenes, GABHS, GBBHS, GDBHS)
- gramma-hemolytic: no destruction of RBC