Normal Microbial Flora

Eric Stanbridge PhD

September 11th Lecture

Medical Microbiology 507

2007

Tel 824-7042ejstanbr@uci.edu

Sites of normal microbial colonization

TABLE 7-2. Microorganisms Found on the Skin

Staphylococcus epidermidis (albus)

(coagulase negative)

85-100

Staphylococcus aureus

(coagulase positive)

5-25

Streptococcus pyogenes (Group A) 0-4

Propionibacterium acnes

(anaerobic corynebacteria)

45-100

Aerobic corynebacteria (diphtheroids) 55

Candida albicans Uncommon

Other Candida species, particularly

C. parapsilosis

1-15

Gram negative bacteria, e.g.,

Enterobacteriaceae or Pseudomonas species

Uncommon

Microorganism Range of Incidence (Per Cent)

STAPHYLOCOCCUS

STREPTOCOCCUS

Mixed Flora, including YEAST (Candida)

TABLE 7-3. Microorganisms Found in the Nose and Nasopharynx

Staphylococcus aureus 20-85

Staphylococcus epidermidis 90

Aerobic corynebacteria (diphtheroids) 5-80

Streptococcus pneumoniae 0-17

Streptococcus pyogenes (Group A) 0.1-5

Alpha-and nonhemolytic streptococci Uncommon

Neisseria catarrhalis 12

Haemophilus influenzae 12

Haemophilus parainfluenzae 20-35

Gram negative bacteria (Enterobacteriaceae) Uncommon

Microorganism Range of Incidence (Per Cent)

Neisseria meningitidis

HEMOPHILUS

COLIFORMS (Escherichia coli)

TABLE 7-4. Microorganisms Found in the Oropharynx

Staphylococcus aureus 35-40

Staphylococcus epidermidis 30-70

Aerobic corynebacteria (diphtheroids) 50-90

Streptococcus pyogenes (Group A) 0-9

Streptococcus pneumoniae 0-50

Alpha-and nonhemolytic steptococci 25-99

Neisseria catarrhalis 10-97

Neisseria meningitidis 0-15

Haemophilus influenzae 5-20

Haemophilus parainfluenzae 20-35

Gram negative bacteria, e.g., Klebsiella pneumoniae Uncommon

Microorganism Range of Incidence (Per Cent)

TABLE 7-5. Microorganisms Found in the Mouth (Saliva-Tooth Surfaces)

Staphylococcus epidermidis 75-100

Staphylococcus aureus Common

Streptococcus mitis and other alpha-hemolytic steptococci 100

Streptococcus salivarius 100

Peptostreptococci (anaerobic) Prominent

Veillonella alcalescens (anaerobic) 100

Lactobacilli 95

Actinomyees israeli Common

Enterobacteriaceae 65

Haemophilus influenzae 25-100

Bacteroides fragilis (anaerobic) Common

Bacteroides melaninogenicus (anaerobic) Common

Bacteroides oralis (anaerobic) Common

Fusobacterium nucleatum (anaerobic) 15-90

Candida albicans 6-50

Treponema dentium and Borellia refringens Common

Microorganism Range of Incidence (Per Cent)

ViridansGroup

Gillies & Dodds, Bacteriology Illustrated, R.R. Gillies, 5th Edtion, p125

ACTINOMYCES

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Treponema

TABLE 7-6 Microorganisms Found in the Stomach and Small Intestine

Microorganism

Stomach - Usually sterile or transient small numbers, owing to gastric pH of 2-3, and rapid transit time of food (but remember Helicobacter pylori).

Jejunum - Small numbers of Gram positive facultative bacteria

(Enterococci, lactobacilli, diphtheroids)

Candida albicans

Ileum - Distal portion may show small numbers of

Enterobacteriacae and anaerobic gram negative bacteria

H. pylori survives in the submucosal layer

Mixed Flora- Fecal Material

Mixed Flora- Abscess

TABLE 7-9. Microorganisms Found in the Genitourinary Tract

Kidneys and urinary bladder normally sterile, Female and male urethra usually sterile except for short anterior segment

Microorganism

Vagina and Uterine Cervix

Lactobacilli 50-70

Bacteroides species 60-80

Clostridium species 15-30

Peptostreptococcus 30-40

Bifidobacterium 10

Eubacterium 5

Aerobic corynebacteria (diphtheroids) 45-75

Staphyloccus aureus 5-15

Staphyloccus epidermidis 35-80

Enterococci (Group D Streptococcus) 30-80

Streptococcus species (usually Group B) 5-20

Enterobacteriaceae 18-40

Candida albicans 30-50

Trichomonas vaginalis 10-25

Range of Incidence (Per Cent)

Dynamics of Lifetime VAGINAL COLONIZATION

micrococcienterococcidiphtheroidslactobacilli (DÖderlein’s bacillus)

No Doderlein’s bacillus micrococci- plus non hemolytic streptococcicoliforms (E. coli)diphtheroids

Includes DÖderlein’s bacillus+ yeast + bacteroides (anaerobes)

No DÖderlein’s bacillus

Birth STERILE

24 hours Mixed Flora:

Several weeks Mixed Flora:

Puberty Mixed Flora:

Menopause Mixed Flora persists

Acidic pH

Maternal glycogen deposited

Glycogen decreased

Alkaline pH

Glycogen redeposited

Acidic pH

Glycogen decreased

Alkaline pH

Lactobacillus species