Classification of Bacteria

MICROBIOLOGY -TAXONOMY

• Taxonomy is the system to classify living

organisms

• Seven groups –kingdom, phylum or div, class,

order, family, genus, species

• Binomial system of nomenclature –genus name

followed by spp name

TAXONOMY

• Systemic classification & categorization of

organisms in to ordered groups

• Bacterial classification according to –

• phenotypic features

a) Morphology –( cocci, bacilli, spirochaetes, )

b)Staining properties –( Gram +ve, Gram –ve ,)

• Cultural requirements –(aerobic, facultative

anaerobe,, anaerobe )

• Biochemical reaction –sugar fermentation reaction

• Antigenic structure –(serotypes)

• Genotypic taxonomy – DNA homology –guanine &

cytosine content (GC )

GRAM STAINING

Classification of Gram positive bacteria

• Cocci – aerobes –

clusters – staphylococcus

chains/pairs – streptococcus

- anaerobes –

chains/clusters -

peptostreptococcus

Classification of Gram positive bacteria

• Bacilli– aerobes –

sporing –Bacillus –B. anthracis

non –sporing –Corynebacterium, Lactobacillus, Nocardia,

- anaerobes –

sporing –Clostridium –

non –sporing –Actinomyces, Propionibacterium

Classification of Gram negative bacteria

• Cocci– aerobes –

Neisseria,

- anaerobes –

Veillonella

Classification of Gram negative bacteria

• Bacilli– aerobes or facultative anaerobes–

a .Parvobacteria –

Haemophilus, Brucella, Bordetella, Yersinea, Pasteurella

b .Enterobacteria –

Escherichia, Klebsiella,Proteus, Serratia,Salmonella, Shigella,

c. Vibrio – Vibrio, Campylobacter

d. Legionella -

Classification of Gram negative bacteria

• Bacilli–anaerobes–

Bacteroides, Porphyromonas,

Prevotella

BACTERIAL IDENTIFICATION

• Macroscopic morphology

• Microscopic morphology

• Physiological/ biochemical characteristics

• Chemical analysis of cell wall

• Serological analysis

• Genetic & molecular analysis

NORMAL FLORA

• Definition: Bacteria & fungi which are

permanent residents of certain body sites.

They are not harmful when present in that

location, but most of them become

serious pathogens when transferred to

deeper tissues. Many are therefore

considered opportunistically pathogenic.

• The establishment of resident bacteria

begins during birth

• Commensals = Normal flora

• Colonizers = Acquisition of a new organism . After the

new organism colonizes (i.e., attaches and grows,

usually on a mucosal mem brane), it may cause an

infectious disease or it may be eliminated by our host

defenses.

• Carrier = An individual harbors a potential pathogen and

therefore can be a source of infection of others

NORMAL FLORA – DISTRIBUTION

• Common sites – in contact with outside world

• Skin, eye,mouth,upper resp tract, GIT,

urogenital tract

• Sterile sites – internal organs & systems –

spleen, pancreas, liver, bladder, CNS

NORMAL FLORA ANATOMIC SITE

• Bacteroides

• Candida albicans

• Clostridium sp.

• Corynebacterium sp.

• Haemophilus sp.

• Lactobacillus sp.

• Neisseria sp.

• S. aureus

• S. epidermidis

• Colon,throat,vagina

• Mouth,colon,vagina

• Colon

• Nasopharynx,skin, vagina

• Nasopharynx,conjunctiva

• Mouth, colon,vagina

• Mouth, Nasopharynx

• Nose, skin

• Skin,nose,mouth,vagina,

urethra

Normal Flora of Skin

• Staphylococcus aureus, and Staph.

epidermidis, Micrococci

• Propionibacterium acnes,

Diphtheroids (Coryneforms)

Respiratory Tract Flora

• Hostile to most bacteria because of mucous

• The upper respiratory tract Staphylococcus aureus, Staph. epidermidis, Streptococcus pneumoniae, Strept. mutans, Strept. viridans, Haemophilous influenzae, Moraxella catarrhalis, Neisseria sicca, Corynebacterium sp.

Teeth • Gingival Crevice - Fusobacterium sp. (G-,

anaerobic, elongated)

• Borrelia sp. (G--, anaerobic, spirillum)

• B. vincentii causes trench mouth (Vincent's

Disease) in predisposed individuals)

• Surface - Leptotrichia buccalis (G-, anaerobic,

filamentous) Lactobacillus sp. (G+ bacilli)

• Streptococcus (G+, cocci)

Dental Caries (Decay Sites)

• Compacted food and bacteria is called Dental

Plaque

• Streptococcus mutans produces glucan

(glycocalyx, Dextran)

• Lactobacillus sp. ferment sucrose inside the

plaque into lactic acid

• Anaerobes-

Bacteroides,Fusobacterium,actinomyces

•

Gastrointestinal Tract Flora

• Mouth - Viridans streptococci 50%

Spirochaetes –borrelia, treponema, Anaerobes

–bacteroides spp,fusobacterium, lactobacillus

spp, prevotella spp, Actinomyces

• Esophagus, Stomach, Duodenum, Jejunem,

Ileum (last part), Colon(1011) : Bacteroides sp.

, Peptostreptococcus sp., Clostridium sp.

enterobacteriaceae,Pseudomonas, protozoa

• Newborns: A. Breast-fed babies -

Bifidobacterium, Lactobacillus

B. Formula-fed babies - Mixed flora

Urogenital Flora

• First month of life -Lactobacillus spp,

• From I month of age to puberty --diphtheroids,

S epidermidis, streptococci, and E coli

• At puberty -- Lactobacillus spp, L.acidophilus,

corynebacteria, peptostreptococci,

staphylococci, streptococci, and Bacteroides

• Menopause --prepubescent flora, Yeasts

(Torulopsis and Candida)

• Gp B Strept,

NORMAL FLORA – UROGENITAL

TRACT

• Adult women -Lactobacillus spp,

• Before puberty & after menopause –lactobacilli

rare

In the anterior urethra

• S epidermidis, enterococci, and

diphtheroids --frequently 102-104

• E coli, Proteus, and Neisseria

(nonpathogenic species) --occasionally

Conjunctival Flora

• corynebacteria, neisseriae, and moraxellae,

Staphylococci, streptococci & Haemophilus

spp.

• Tears contain lysozyme, help limit bacterial

population of conj

Diseases due to normal flora

NORMAL FLORA –BENEFICIAL

FUNCTIONS

• 1-Due to increased no in lower GIT & mouth

compete for nutrients with invading pathogens

• 2- Some bacteria of bowel produce antibacterial

subs

• 3- Bacterial colonization of newborn infant acts

as a powerful stimulus for development of

immune system

• 4- Bacteria of gut produce vit K

NORMAL FLORA –harmful effects

• When org are displaced from normal site in

body to abnormal site

eg: skin flora - Endocarditis

Urethral flora - UTI

Gut flora - Peritonitis

Mouth flora – Fascial soft tissue

infection

When individual are immunocopromised,

normal flora can overgrow & become pathogenic

Death of normal flora

• diminished population of normal flora due to

antibiotic therapy cause overgrowth of C.

difficile - Psuedomembranous colitis