Normal Flora Flashcards
Skin Flora
Coagulase-negative Staphylococci
S. epidermidis (opportunistic infections)
Skin "diphtheroids" Corynebacterium species (opportunistic) Propionibacterium acnes (acne, opportunistic infections) ** most skin bacteria are anaerobic cus they're usually down the sebum
Acne
An inflammatory disease of the skin involving abnormal keratin production and commensal skin bacteria
Propionibacterium acnes
Gram-positive club-shaped bacilli, anaerobic (some strains aerotolerant)
Important component of normal skin flora after puberty
Disease: acne
Inflammation of the pilosebaceous unit (hair follicle and sebaceous gland)
Pathogenesis
Increase in sebum production induced by androgen hormones
Colonization of glands by P. acnes which utilizes fatty acids in sebum as carbon source
Abnormal keratin production and sloughing of keratin-producing cells in the follicle causes blockage and accumulation of sebum
Bacteria and products of bacterial metabolism induce inflammation
Acne-associated strains differ from strains isolated from normal skin
Therapy
Suppress bacteria: topical benzoyl peroxide, topical and oral antibiotics
Suppress keratin formation: topical retinoids
Suppress sebum production: oral isotretinoin, combined oral contraceptives
Oral Microbiota
-Streptococcus species (Gram positive cocci in chains)
“Viridans” streptococci (endocarditis)
S. mutans (dental caries)
-Actinomyces (Gram positive branching bacilli)
A. israelii (cervicofacial abscesses)
-Anaerobic Gram negative bacilli (gingivitis, lung abscess)
Porphyromonas gingivalis
Nasopharyngeal microbiota
-Staphylococci
S. epidermidis (opportunistic)
S. aureus (skin and wound infections, pneumonia, bacteremia, endocarditis, toxic shock syndrome)
-Streptococci
S. pyogenes (Group A Streptococcus) (skin and wound infections, pharyngitis, toxic shock syndrome, pneumonia, sinusitis, otitis)
S. pneumoniae (pneumonia, meningitis, sepsis, otitis, sinusitis)
Viridans streptococci (endocarditis)
-Haemophilus influenzae (meningitis, sepsis, pneumonia, otitis, sinusitis)
-Neisseria meningitidis (meningitis, sepsis, pneumonia)
Moraxella catarrhalis (sinusitis, otitis)
Stomach Microbiota
Helicobacter pylori (Gram – curved bacilli)
gastritis, gastric and duodenal ulcers
gastric adenocarcinoma, gastric lymphoma
protective against esophageal reflux disease, esophageal cancer
negative association with (protection against?) asthma, inflammatory bowel diseases, obesity
Microbiota of the Colon
Site of most dense microbial microbiota
***Obligate anaerobic bacteria predominate
Beneficial effects: Protection from pathogens Stimulation of gut maturation Stimulation of innate and adaptive immune systems Expansion of nutritional diversity Digestion of complex carbohydrates
Deleterious effects of microbiota of the colon
Deleterious effects
Source of pathogens
Association with inflammatory bowel diseases (IBD: ulcerative colitis, Crohn’s disease)
Hypotheses:
IBD may result from dysregulation of immune responses to normal microbiota in genetically susceptible host
Composition of gut microbiota may presdispose towards or protect against development of IBD
Bugs of the colon
Anaerobic bacteria
Bacteroides fragilis (peritoneal abscesses)
Clostridium species (gas gangrene, antibiotic-associated colitis)
Fusobacteria (abscesses)
Enteric bacteria (Family Enterobacteriaceae) (urinary tract infections, sepsis, pneumonia)
Escherichia coli
Proteus
Enterobacter & Klebsiella-include CRE strains
Enterococcus (urinary tract infections, endocarditis, sepsis)
incl. VRE strains
Microbiota of the Vagina
Least diverse bugs. Mostly facultative anaerobe-will ferment only, no respiration
Lactobacillus crispatus, Lactobacillus iners. Keep pH low to ward off other bugs
Gram-positive bacilli
predominant bacterial flora in healthy vagina
Gardnerella vaginalis (vaginosis) Gram-variable coccobacilli
Anaerobic Gram-negative bacilli
Bacteroides, Prevotella, Porphyromonas (vaginosis, abscesses, pelvic inflammatory disease)
Group B Streptococci (neonatal meningitis, sepsis)
Gram-positive cocci in chains
E.coli (urinary tract infections, neonatal meningitis)
Gram-negative bacilli, members of Enterobacteriaciae
Bacterial Vaginosis (BV)
The disease: abnormal vaginal odor and discharge
Complications: BV is a risk factor for pelvic inflammatory disease, premature labor and delivery, low birth weight, increased susceptibility to HIV infection
Epidemiology:
Common (most common vaginal infection)
~30% of women show microbiological evidence of BV, ~50% of these are symptomatic
Risk correlates with number of sex partners, Black race
High prevalence (35-50%) in WSW (women who have sex with women) with concordance between partners
Epidemiology suggests sexual transmission of a pathogen, but the component of BV microbiota capable of transmitting the disease remains a mystery
BV pathogenesis
Pathogenesis: abnormal vaginal microbiota
association with absence of Lactobacillus species (L. crispatus and L. iners)
lactic acid is broadly bactericidal at low pH and anaerobic conditions of vagina, inhibits growth of other bacteria
elevated vaginal pH
predominance of Gardnerella vaginalis (minor component bug usually)
Gram-variable facultative coccobacilli (Gram positive structure)
predominance of a variety of anaerobic bacteria
production of amines (trimethylamine) induces transudation and exfoliation of epithelial cells
degradation of mucins producing thin homogenous discharge
increased production of cervical cytokines (IL1, IL8, TNF)
in pregnancy, inflammation of amnion
BP Dx
Diagnosis
Amsel criteria: any 3 of the following
1. observation of “clue cell” on microscopic examination of vaginal smear wet mount
2. adherent grayish discharge,
3. production of volatile malodorous amines on addition of KOH (whiff test)
4. vaginal pH > 4.5 (e.g. Femexam pH and amine test card)
Nugent criteria (“gold standard”): quantitative scoring of Gram stain based on:
- Absence of large Gram-positive rods (Lactobacilli)
- Presence of small Gram variable coccobacilli (Gardnerella vaginalis) and Gram-negative rods
- Presence of small Gram-variable curved rods
BV Therapy
Therapy: oral or topical antibiotics active against anaerobes (clindamycin, metronidazole)
Recurrence is frequent
