Normal Flora Flashcards
what is true resident flora
strains with established niche at body sites where they stay indefinitely
what is transient flora
flora acquired from environment that establish briefly, but then are excluded by competition from residents or host immune systems
what is a carrier state
organisms known to be potentially pathogenic transiently growing
what flora can be found in the throats of 5-40% of people
strepococcus pneumoniae and neisseria meningitidis
function of normal flora
- barrier to infection and colonization by pathogenic bacteria
- synthesize some vitamins we need
- stimulates immune system
how much bacteria does the body have?
1.2kg of bacteria on and in their body
what is antagonism
where normal flora prevents colonization of GI tract and respiratory tract by pathogens
how do normal flora prime the immune system?
primes to PAMP and raises basic level of tolerance to some common pathogens, so host responds to invading pathogens
what causes opportunistic infections
- injury - break in skin or mucosa
- physical destruction - peritonitis, burns
- immunosuppression
what causes normal flora to become pathogenic
- opportunistic infections
- ecological disruptions (aka overgrowth of bacteria – BV)
- conversion of non carcinogens to carcinogens (h pylori to GI and breast cancer)
where is normal flora found
skin, nails, eyes, oropharynx, genitalia, GI
is there flora in a fetus at birth?
no, is sterile, but acquired during and immediatly after birth
where do babies encounter their first flora
- normal flora from mothers genital tract and skin
2. respiratory tract of people present at birth
what influences what bacteria colonize where?
pH, redox potential, oxygen, water, nutrient level, resistance to local antibacterial substances
what flora live on the skin?
- staph aureus
2 staph epidermidis - propionibacerium acnes
what flora live in the mouth/throat?
strepococci, anaerobic bacteria, candidia albicans
what flora live in the large intestine?
coliforms like E coli (10^11 per gram)
what flora live in the female genital tract?
lactobacilli which lower pH by producing lactate
3 main regions of flora on skin
- axilla, perineum, toe webs
- hand, face, trunk
- upper arms, legs, scalp
why is skin unfavorable for most bacteria?
- too dry
- too acidic (5.5)
- rapid turnover of epithelial cells
most important factor limiting number and kinds of bacteria on skin
dryness of skin
what substance produced on skin inhibit gram negative flora?
unsaturated fatty acids produced by gram positive bacteria
how is the skin acidic
sweat glands excrete lysozyme which inhibits gram positive bugs by hydrolyzing NAG/NAM
what type of microbes live in axilla, perineum and toes?
gram negatives
where do staphylococcus aureus live
- nose
- perineum
- vulvar tissue
what is the major inhabitant of the skin
staphylococcus epidermidis
what flora is common on patients with atopic dermatitis?
staph aureus
what bacteria are commonly found in acne lesions
propionibacterium acnes
what are propionibacterium
gram positive
what are staphylococcus
gram positive
where are propionibacterium avidum found?
axilla
where do anaerobes live?
within ducts of hair follicles and sebaceous glands - what is why antiseptic tx or washing cannot remove them
does the stomach contain any resident organisms when healthy
little or few resident organisms except H pylori
flora in upper small intestine
scanty except in the lower ileum
flora in the duodenum
VOID of natural flora
flora in jejunum
streptococcus ssp, corynebacterium ssp, lactobacillus ssp.
what indicates abnormality in small intestine?
people with 10^5 - 10^7 bacteria/mL
what is associated with increased bacteria in small intestine?
achrlohydria malabsorption syndrome where lack of HCl in stomach
flora in ileum
lactobacillus ssp, streptococcus spp, enterobacteriaceae ssp, bacteroide ssp – contains 10^5 - 10^8 bacteria/mL
what place carriers the most abundant and diverse microbiota in the body
colon
what flora in colon
mostly anaerobes, bacteroides, fusobacterium, eubacterium, clostridium and facultative organisms like E coli, enterococci and yeasts
what impacts species composition in the colon?
diet! increased meat means increased bacteroides and other anaerobic gram negative rods
top 6 species in the colon
- bacteroids thetaiotaomicron
- bacteroids vulgatus
- fusobacterium prausnitzii
- bifidobacterium adolescentis
- eubacterium acrofaciens
- peptostreptococcus productus (anaerobic)
what do the top 6 species in the colon produce
acetic, butyric and lactic acid which inhibit other bacteria
what is included in the top 20 speies in the colon?
bacteroides fragilis
clostridum ramosum
what is included in the lower 50 species in the colon
enterococcus faecalis
e coli
benefits of gut microbiota
- maintains GI tract peristalsis and integrity
- synthesizes vitamin K and B complex
- convert dietary carcinogens and precarcinogens to noncarcinogens
what does the layer of bacteria in the gut secrete?
bacteroicins that inhibit other bacteria and prevent certain bacteria from colonizing, and protects basement epithelial cells from pathogenic bacteria by blocking adhesion
which organs are sterile in healthy humans?
kidneys, ureters, and urinary bladder
what indicates a contaminated urine sample?
10^4 bacteria
what does female normal flora depend on ?
age, pH and hormone levels
what bacteria predominate in adult women?
- lactobacillus acidophilus
- bacteroides ssp
- clostridium ssp
- peptostrepococcus
what bacteria predominate in young women (1 month old to puberty) and post menopausal women?
- staphylococcus epidermidis
- streptococcus ssp
- e coli
why does flora change with age?
estrogen causes an increase in glycogen, so lack of estrogen makes glycogen stop being secreted, and causes a rise in pH
benefit of lactobacillus in women
maintains acidic environment and inhibits gram negative bacterial growth (bacterial antagonism)
what is grade I
only lactobacillus present
what is grade II
both lactobacillus and gardnerella or bacteroides present
what is grade III
bacterial vaginosis, lactobacillus are absent and only gardnerella, bacteroides-prevotella or mobiluncus cell types present
what is grade IV
gram positive cocci predominantly present
what upper respiratory organs are free of normal flora/
larynx, trachea, bronchi, lungs
URT normal flora:
- staphylococcus epidermidis
- corynebacterium ssp
- lactobacillus ssp
- p acnes
URT transient flora which are asymptomatic
- strep pneumoniae
- staph aureus
- h influenzae
- neisseria meningitidis
describe flora of external 1 cm of anterior nares
similar to skin, mostly staph aureus
describe flora of naspharynx
similar to mouth, also pneumococci, meningococci and haemophilus
flora of respiratory tract below larynx
only transiently inhaled organisms bc free of flora due to epithelial cilia and muco-ciliary blanket
normal flora in mouth
facultative and anaerobic bacteria
flora on buccal mucosa
streptococci
flora in oropharynx
streptococci and neisseria
flora in depths of gingival crevices around teeth?
strict anaerobes and microaerophilic organisms
describe oral flora in a newborn 1 day old baby
sterile
describe oral flora in 1 week old baby
strep salivarius, strep mitis, veillonella and other anaerobes
describe oral flora in infants with no teeth
streptococcus!!
describe oral flora in infants with teeth
obligate anaerobes aka fusobacterium and bacteroides and facultative anaerobes like strep mutans on teeth surfaces
when is normal oral flora present?
1 year old
what is the primary producer of dental caries?
streptococcus mutans
when can normal flora become pathogenic?
- when misplaced
- overgrown (immunocompromised)
- enhanced virulence
what causes acute UTI
E coli
what causes peritonitis and intra abdominal abscesses?
gram positive and negative bacteria that is from perforation of the colon
which microorganism is found in gingival crevices at puberty
treponema sp
3 body locations where gram stain alone will not be diagnostic
- nose
- oropharynx
- vagina
because residence of normal flora which resemble pathogens
