Normal FloraNormal FloraWhat’s growing on us?What’s growing on us?

Normal flora (mostly Normal flora (mostly bacteria)bacteria) In the past Medical Microbiology was largely focused In the past Medical Microbiology was largely focused

on those organisms that were frankly pathogenic. on those organisms that were frankly pathogenic. It is now known that those microorganisms that It is now known that those microorganisms that

normally colonize the human host without disease normally colonize the human host without disease production can play an important role in the disease production can play an important role in the disease process. process.

Many of those once considered to be innocuous Many of those once considered to be innocuous members of the normal flora are now known to be members of the normal flora are now known to be potentially pathogenic under certain circumstances potentially pathogenic under certain circumstances (what circumstances?).(what circumstances?). Therefore, it’s important to Therefore, it’s important to acquire knowledge about our normal flora because:acquire knowledge about our normal flora because:

Normal FloraNormal Flora An understanding of the different normal An understanding of the different normal

flora (NF) found at specific body locations flora (NF) found at specific body locations provides greater insight into the possible provides greater insight into the possible infections that might result from injury to infections that might result from injury to those body sites.those body sites.

A knowledge of the native organisms in the A knowledge of the native organisms in the infected part of the body gives the clinician infected part of the body gives the clinician perspective on the possible source and/or perspective on the possible source and/or significance of microorganisms isolated significance of microorganisms isolated from the site of infection.from the site of infection.

Normal FloraNormal Flora Before a discussion of adult NF begins, a Before a discussion of adult NF begins, a

discussion of how or when NF is acquired discussion of how or when NF is acquired is essential.is essential. A healthy fetus, in utero, is essentially free of A healthy fetus, in utero, is essentially free of

microorganisms.microorganisms. The infant is exposed to NF from the mom’s The infant is exposed to NF from the mom’s

vaginal tract during the delivery process and to vaginal tract during the delivery process and to microorganisms in the environment almost microorganisms in the environment almost immediately thereafter.immediately thereafter.

Normal FloraNormal Flora Within a few hours, the oral and Within a few hours, the oral and

nasopharyngeal flora of the neonate are nasopharyngeal flora of the neonate are established.established.

Within one day the resident microflora of Within one day the resident microflora of the lower intestinal tract are established.the lower intestinal tract are established.

Adult NF refers to microorganisms that Adult NF refers to microorganisms that normally live on or in any part of the normally live on or in any part of the body without causing disease. There body without causing disease. There are two basic types of NF:are two basic types of NF:

Normal FloraNormal Flora Resident organismsResident organisms – these are organisms – these are organisms

that normally that normally GROWGROW on or in the indicated on or in the indicated body site. Their presence becomes fixed body site. Their presence becomes fixed in well defined distribution patterns.in well defined distribution patterns.

Transient organismsTransient organisms – These organisms – These organisms are only are only temporarily presenttemporarily present on or in the on or in the indicated body site. They usually don’t indicated body site. They usually don’t become firmly entrenched, but simply die become firmly entrenched, but simply die within a few hours.within a few hours.

Normal FloraNormal Flora NF of the skin NF of the skin

The actual physiology of the skin varies from one The actual physiology of the skin varies from one part of the body to another and the resident part of the body to another and the resident microflora reflect these variations. microflora reflect these variations.

The skin, itself, is not a very favorable The skin, itself, is not a very favorable environment for the colonization of environment for the colonization of microorganisms. microorganisms.

Therefore, there are few resident microorganisms, Therefore, there are few resident microorganisms, but many transient microorganisms. Why is the but many transient microorganisms. Why is the microenvironment hostile?:microenvironment hostile?:

Normal FloraNormal Flora The skin is subject to periodic drying. However, in The skin is subject to periodic drying. However, in

certain parts of the body (body folds or areas near certain parts of the body (body folds or areas near orifices), there is sufficient moisture to support the orifices), there is sufficient moisture to support the growth of resident microorganismsgrowth of resident microorganisms

Skin has a slightly acidic pH due to organic acids Skin has a slightly acidic pH due to organic acids produced by normal secretions from the sebaceous produced by normal secretions from the sebaceous and sweat glands and by and sweat glands and by Staphylococcus Staphylococcus epidermidisepidermidis that normally resides there. This that normally resides there. This prevents the colonization by many organisms. prevents the colonization by many organisms.

Sweat contains a high content of NaCl, thus Sweat contains a high content of NaCl, thus producing a producing a hypertonic conditionhypertonic condition on the skin surface on the skin surface that osmotically stresses many microorganisms.that osmotically stresses many microorganisms.

Normal FloraNormal Flora The skin surface contains many inhibitory substances The skin surface contains many inhibitory substances

that help control colonization, overgrowth, and that help control colonization, overgrowth, and production of infectious disease by resident production of infectious disease by resident microorganisms. Remember that microorganisms. Remember that colonization does colonization does not necessarily mean infection and disease.not necessarily mean infection and disease. Lysozyme – is produced by the sweat glands and acts to lyse Lysozyme – is produced by the sweat glands and acts to lyse

G+ organisms, including G+ organisms, including Staph. epidermidisStaph. epidermidis Complex lipids – are metabolized by Complex lipids – are metabolized by Propionobacterium Propionobacterium

acnesacnes to unsaturated fatty acids that have antimicrobial to unsaturated fatty acids that have antimicrobial activity. These produce a strong odor. Use of deodorants activity. These produce a strong odor. Use of deodorants that have antibacterial substances to inhibit the growth of that have antibacterial substances to inhibit the growth of these G+ organisms may lead to the growth of a these G+ organisms may lead to the growth of a preponderance of G- organisms and the subsequent preponderance of G- organisms and the subsequent development of infection.development of infection.

Normal FloraNormal Flora Most skin NF are found on the Most skin NF are found on the

superficial squamous epithelium superficial squamous epithelium colonizing dead cells or closely colonizing dead cells or closely associated with the sebaceous and associated with the sebaceous and sweat glands. The secretions from sweat glands. The secretions from these glands provide the these glands provide the environmental conditions and environmental conditions and nutrients for the growth of:nutrients for the growth of:

Skin Normal FloraSkin Normal FloraStaph. epidermidis and Staph. aureusStaph. epidermidis and Staph. aureus

Skin NFSkin NFPropionibacterium acnesPropionibacterium acnes – this is an – this is an

anaerobic G+ branching bacillusanaerobic G+ branching bacillus

Skin NFSkin NF P. acnesP. acnes is usually harmless, but has been is usually harmless, but has been

associated with acne vulgaris (acne), associated with acne vulgaris (acne), particularly during adolescence when there is an particularly during adolescence when there is an overproduction of the fluid secreted by the overproduction of the fluid secreted by the sebaceous glands (sebum). sebaceous glands (sebum). This provides the ideal environment for the growth of This provides the ideal environment for the growth of

P. acnesP. acnes and substances produced by the organisms and substances produced by the organisms may trigger an inflammatory response leading to the may trigger an inflammatory response leading to the production of acne. production of acne.

Tetracycline or accutane (prevents sebum secretions, Tetracycline or accutane (prevents sebum secretions, but has some severe side effects) may be used for but has some severe side effects) may be used for treatment of acne.treatment of acne.

Skin NFSkin NFDiphtheroids (aerobic Diphtheroids (aerobic

corynebacteriumcorynebacterium))

Skin NFSkin NFStreptococcus speciesStreptococcus species

Skin NFSkin NFClostridium perfringensClostridium perfringens

Skin NFSkin NFCandida albicansCandida albicans

Normal FloraNormal Flora Normal flora of the nose and nasopharynx Normal flora of the nose and nasopharynx

(part of the pharynx above the soft palate)(part of the pharynx above the soft palate) Staph aureus*Staph aureus* Staph epidermidisStaph epidermidis DiphtheroidsDiphtheroids Streptococcus pneumoniae*Streptococcus pneumoniae* Haemophilus influenzae*Haemophilus influenzae* Neisseria meningitidis*Neisseria meningitidis* * may be causing disease if found in large * may be causing disease if found in large

numbers (relative numbers are important)numbers (relative numbers are important)

Nose/nasopharynx NFNose/nasopharynx NFNeisseria meningitidisNeisseria meningitidis

Nose/nasopharynx NFNose/nasopharynx NFHaemophilus influenzaeHaemophilus influenzae

Normal FloraNormal Flora Normal flora of the oral cavity and Normal flora of the oral cavity and

oropharynxoropharynx Organisms found are those that are able to resist Organisms found are those that are able to resist

mechanical removal by adhering to various mechanical removal by adhering to various surfaces such as the gums and teeth. surfaces such as the gums and teeth. Those bacteria that can’t resist the mechanical flushing Those bacteria that can’t resist the mechanical flushing

of the oral cavity are swallowed and destroyed by the of the oral cavity are swallowed and destroyed by the HCl in the stomach. HCl in the stomach.

This is a comfortable environment for This is a comfortable environment for microorganisms due to the availability of water microorganisms due to the availability of water and nutrients. The most common NF in this area and nutrients. The most common NF in this area includes:includes:

Normal oral floraNormal oral flora viridans group viridans group Streptococcus speciesStreptococcus species Strep. pyogenes*Strep. pyogenes* DiphtheroidsDiphtheroids Staph. epidermidisStaph. epidermidis Staph. aureus*Staph. aureus* Neisseria meningitidis*Neisseria meningitidis* Other Other NeisseriaNeisseria species species Haemophilus influenzae*Haemophilus influenzae* Other Other Haemophilus speciesHaemophilus species

Normal oral floraNormal oral flora Candida albicans*Candida albicans* Actinomycetes sp.*Actinomycetes sp.* Lactobacillus sp.Lactobacillus sp. Bacteroides sp.Bacteroides sp. Fusobacterium sp.Fusobacterium sp. Enterobacteriaceae*Enterobacteriaceae* * these organisms are probably causing * these organisms are probably causing

infection if they are the infection if they are the predominant predominant organismorganism found in this area or they are found in this area or they are found in large numbers.found in large numbers.

Normal oral floraNormal oral floraActinomycetesActinomycetes

Normal oral floraNormal oral floraGranules of ActinomycetesGranules of Actinomycetes

Normal oral floraNormal oral floraBacteroides sp.Bacteroides sp.

Normal oral floraNormal oral flora

Fusobacterium sp.Fusobacterium sp.

Normal oral floraNormal oral flora

Fusobacterium nucleatumFusobacterium nucleatum

Normal oral floraNormal oral flora

LactobacillusLactobacillus

Normal oral floraNormal oral floraE. coliE. coli (a member of the (a member of the

Enterobacteriaceae)Enterobacteriaceae)

Normal oral floraNormal oral flora

Some of the Some of the Strep. speciesStrep. species that adhere to the that adhere to the teeth (teeth (sanguis, mutans, salivarious)sanguis, mutans, salivarious) contribute to the formation of dental plaques contribute to the formation of dental plaques and cariesand caries

Normal FloraNormal Flora Normal flora of the alimentary tractNormal flora of the alimentary tract

Because of the high acidic content of the Because of the high acidic content of the stomach, very few organisms are found there. stomach, very few organisms are found there. They include:They include: Candida sp.Candida sp. LactobacilliLactobacilli A few Strep. sp. (A few Strep. sp. (mainlymainly Enterococcus faecalis) Enterococcus faecalis)

The small intestine also has few The small intestine also has few microorganisms because of the combined microorganisms because of the combined inhibitory effects of stomach acid, bile, and inhibitory effects of stomach acid, bile, and pancreatic secretions. Normal flora include:pancreatic secretions. Normal flora include:

Normal intestinal floraNormal intestinal flora Enterococcus faecalisEnterococcus faecalis LactobacilliLactobacilli DiphtheroidsDiphtheroids Candida sp.Candida sp.

The large intestine has the largest The large intestine has the largest microbial population in the body. There microbial population in the body. There are 10are 1012 12 organisms excretedorganisms excreted per gram of per gram of wet weight feces.wet weight feces.

Over 300 Over 300 differentdifferent species of bacteria species of bacteria are normally found in the large intestineare normally found in the large intestine

Normal intestinal floraNormal intestinal flora The anaerobic/facultatively anaerobic The anaerobic/facultatively anaerobic

ratio of organisms is 300/1 and includes ratio of organisms is 300/1 and includes the following:the following: Bacteroides sp.Bacteroides sp. Fusobacterium sp.Fusobacterium sp. LactobacillusLactobacillus Clostridium sp.Clostridium sp. Peptostreptococcus sp.Peptostreptococcus sp. Staph. sp.Staph. sp. Enterococcus faecalisEnterococcus faecalis

Normal intestinal floraNormal intestinal flora Other Other Strep. sp.Strep. sp. Pseudomonas speciesPseudomonas species EnterobacteriaceaeEnterobacteriaceae Candida sp.Candida sp.

Normal intestinal floraNormal intestinal floraPseudomonas speciesPseudomonas species

Normal intestinal floraNormal intestinal floraPeptostreptococcus speciesPeptostreptococcus species

Normal intestinal floraNormal intestinal flora Normal physiological processes move Normal physiological processes move

the microorganisms through the colon the microorganisms through the colon so that a normal adult excretes 3X 10so that a normal adult excretes 3X 101313 microorganisms daily.microorganisms daily.

Under normal conditions the resident Under normal conditions the resident flora are self-limiting. Competition( for flora are self-limiting. Competition( for example, colicin produced by example, colicin produced by E. coliE. coli) ) and mutualism between them and the and mutualism between them and the host (host (E.coliE.coli produces vitamin K and B for produces vitamin K and B for the host) maintains the status quo. the host) maintains the status quo.

Normal intestinal floraNormal intestinal flora Anything the disturbs the intestinal Anything the disturbs the intestinal

environment (stress, altitude change, environment (stress, altitude change, starvation, diarrhea, antibiotics) can starvation, diarrhea, antibiotics) can serve to greatly alter the normal flora serve to greatly alter the normal flora leading to gastrointestinal disease such leading to gastrointestinal disease such as yeast infections and antibiotic as yeast infections and antibiotic associated pseudomembraneous colitis.associated pseudomembraneous colitis.

Normal floraNormal flora NF of the genitourinary tractNF of the genitourinary tract

NF of the urethra include:NF of the urethra include: Staph. epidermidisStaph. epidermidis Enterococcus faecalisEnterococcus faecalis DiphtheriodsDiphtheriods Neisseria sp.Neisseria sp. ( (NOTNOT N. gonorrhoeaeN. gonorrhoeae)) EnterobacteriaceaeEnterobacteriaceae

NF of the vaginal tract – the microflora present NF of the vaginal tract – the microflora present on this large, moist surface area changes with on this large, moist surface area changes with the menstrual cycle. Organisms include:the menstrual cycle. Organisms include:

Normal genitourinary floraNormal genitourinary flora LactobacillusLactobacillus BacteroidesBacteroides Enterococcus sp.Enterococcus sp. Staph. epidermidisStaph. epidermidis DiphtheroidsDiphtheroids Strep. agalactiaeStrep. agalactiae Clostridium perfringensClostridium perfringens PeptostreptococcusPeptostreptococcus EnterobacteriaceaeEnterobacteriaceae Candida albicansCandida albicans

Normal genitourinary floraNormal genitourinary flora NF of the external genitalia include:NF of the external genitalia include:

Strep. sp.Strep. sp. Staph. sp.Staph. sp. DiphtheroidsDiphtheroids BacteroidesBacteroides Candida sp.Candida sp.