Normal Flora What’s growing on us?

Normal Flora (mostly bacteria) In past Medical Microbiology focus on pathogenic MOs Realize MOs that normally colonize humans without harm can play role in disease Many innocuous NF now known to be potentially pathogenic under certain circumstances (what circumstances?) Therefore, important to acquire knowledge about our NF

Knowledge of Normal Flora Understanding of NF found at specific body location provides insight into possible infections that result from injury Knowledge of NF at a body site gives clinician perspective on possible source and/or significance of MOs isolated from site of infection

Origin of Normal Flora Healthy fetus, in utero, is essentially free of MOs Infant exposed immediately to MOs when passing through mom’s vaginal tract and then to MOs in environment Within few hours, oral and nasopharyngeal flora of neonate established Within one day, resident flora of lower intestinal tract established

Adult Normal Flora MOs that normally live on or in any part of the body without causing disease Two basic types of NF: Resident NF – normally GROW on/in indicated body site, presence fixed in well defined distribution patterns Transient NF – only TEMPORARILY PRESENT on/in indicated body site, usually don’t become firmly entrenched but simply die within hours

Skin Normal Flora Staphylococcus epidermidis Staphylococcus aureus Propionibacterium acnes Corynebacterium Streptococcus species Candida albicans Clostridium perfringens

Skin Normal Flora Most skin NF found on superficial squamous epithelium, colonizing dead cells or closely associated with sebaceous and sweat glands Secretions from these glands provide environmental conditions and nutrients for growth of numerous skin NF

Skin: Hostile Environment Subject to periodic drying Certain parts (folds, areas near orifices) sufficient moisture support resident MOs Slightly acidic pH due to organic acids ( sebaceous & sweat glands, Staphylococcus) prevents colonization of many MOs Sweat contains high NaCl, producing hypertonic condition on skin surface that osmotically stresses many MOs

Skin: Inhibitory Substances Help control colonization, overgrowth, production of disease by resident MOs Remember - colonization not necessarily mean infection and disease Lysozyme – produced by sweat glands and lyse G(+) MOs Complex lipids – metabolized by Propionobacterium acnes to unsaturated fatty acids that have antimicrobial activity (produce strong odor) Use of deodorants with antibacterial substances, inhibit growth of G(+), may lead to growth of G(-) MOs and infection

Skin Normal Flora Staphylococcus epidermidis Staphylococcus aureus C+, clusters

Skin Normal flora Propionibacterium acnes B+, anaerobic Diphteroids (club shaped) Branching bacilli

Propionibacterium acnes Harmless, but associated with acne during adolescence and overproduction of sebum by sebaceous gland Provides ideal environment for growth of P. acnes and substances produced trigger inflammatory response leading to acne Tetracycline (antibiotic) or accutane (prevents sebum secretions, some severe side effects) may be used for acne treatment

Skin Normal Flora Corynebacterium B+, aerobic Diphtheroids

Skin Normal Flora Streptococcus species C+, pairs, chains

Skin Normal Flora Candida albicans Yeast, budding Soil & air

Skin Normal Flora Clostridium perfringens B+, anaerobic spore former Soil & air

Nose & Nasopharynx (NP) Normal Flora Nasopharynx (part of pharynx above soft palate) Staphylococcus aureus* Staphylococcus epidermidis Diphtheroids Streptococcus pneumoniae* Haemophilus influenzae* Neisseria meningitidis* * may be causing disease if in large numbers (relative numbers important)

Nose & NP Normal Flora Haemophilus influenzae B-, short cocobacilli Fastidious

Nose & NP Normal Flora Neisseria meningitidis C-, in pairs “coffee bean”

Oral & Oropharynx (OP) Normal Flora Resist mechanical removal by adhering to various surfaces such as gums and teeth MOs that can’t resist mechanical flushing of oral cavity, swallowed, destroyed by HCl in stomach Comfortable environment for MOs due to availability of water and nutrients

Oral & OP Normal Flora Viridans group – α hemolytic Streptococcus sp. Streptococcus pyogenes* Diphtheroids Staphylococcus epidermidis Staphylococcus aureus* Neisseria meningitidis* Other Neisseria species Haemophilus influenzae* Other Haemophilus sp.

Oral & OP Normal Flora Candida albicans* Actinomycetes sp.* Lactobacillus sp. Bacteroides sp. Fusobacterium sp. Enterobacteriaceae* * probably causing infection if predominant organism found or in large numbers

Oral & OP Normal Flora Some Streptococcus species (sanguis, mutans, salivarious) adhere to teeth and contribute to formation of dental plaques and caries

Oral & OP Normal Flora Actinomyces B+, branching Forms granules

Oral & OP Normal Flora Lactobacillus B+, anaerobe

Oral & OP Normal Flora Bacteroides sp. B-, anaerobe

Oral & OP Normal Flora Fusobacterium sp. B-, anaerobe

Oral & OP Normal Flora Fusobacterium nucleatum B-, anaerobe Enlongated

Oral & OP Normal Flora Escherichia coli Family Enterobacteriaceae B-, short, coccobacilli

Gastrointestinal (GI) Tract Normal Flora: Stomach Because of high acidic content very few MOs Candida sp. Lactobacilli A few Streptococcus sp. (mainly Enterococcus faecalis)

GI Tract Normal Flora: Small Intestine Few MOs because inhibitory effects of stomach acid, bile, and pancreatic secretions Enterococcus faecalis Lactobacilli Diphtheroids Candida sp.

GI Tract Normal Flora: Large Intestine Largest microbial population in human body ~1012 MOs/gram feces Over 300 different species of bacteria The anaerobic/facultatively anaerobic bacteria ratio is 300/1

GI Tract Normal Flora: Large Intestine Bacteroides sp. Fusobacterium sp. Lactobacillus Clostridium sp. Peptostreptococcus sp. Staphylococcus sp. Enterococcus faecalis Other Streptococcus sp. Pseudomonas species Enterobacteriaceae Candida sp.

GI Tract Normal Flora Pseudomonas species B-, soil & water

GI Tract Normal Flora Peptostreptococcus species C+, anaerobe

GI Tract Normal flora Normal physiological processes move MOs through colon, adult excretes 3x1013 daily Under normal conditions resident NF self-limiting Competition of MOs ( i.e. colicin by E. coli) Mutualism with host (i.e. E. coli produces vitamin K and B for host) Maintains status quo

GI Tract Normal flora Anything disturbs intestinal environment (stress, altitude change, starvation, diarrhea, antibiotics) can alter NF leading to GI disease Yeast infections Antibiotic associated pseudomembraneous colitis)

Genitourinary (GU) Tract Normal Flora: Urethra Staphylococcus epidermidis Enterococcus faecalis Diphtheriods Neisseria sp. (NOT N. gonorrhoeae) Enterobacteriaceae

GU Tract Normal Flora: Vaginal Changes over lifetime ( i.e. menstrual cycle) Lactobacillus (probiotic “friendly bacteria”) Bacteroides Enterococcus sp. Staphylococcus epidermidis Diphtheroids Streptococcus agalactiae Clostridium perfringens Peptostreptococcus Enterobacteriaceae Candida albicans

GU Tract Normal Flora: External Genitalia Streptococcus sp. Staphylococcus sp. Diphtheroids Bacteroides Candida sp.

Class Assignment Textbook Reading: Chapter 2 Host-Pathogen Interaction A. The Role of the Usual Microbial Flora Key Terms Learning Assessment Questions