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Module: BIOM - 1009

Lecturer: Dr Martin

Date: 24/10/16

Medically Important Gram Positive Bacteria: Non-Spore Forming

Staphylococcus
o

Staphylococcus is a class of Gram-positive, cocci bacteria of the Staphylococcaceae family



These can then be divided up into ~40 species
They are usually found in grape-like clusters

o

Most species of Staphylococcus are harmless and reside normally on the skin and mucous membranes of
humans and other organisms, some more virulent strains include:
 S
...
aureus on their skin
 The species is spread by direct contact and can often be found in the nose and on the skin
 S
...
such as IV lines and catheters
 This makes infection of S
...
An example of this is during AIDS

o

The structure of this particular genus of bacteria is interesting as it can be quite dangerous with its products:
 Staphylococcus have the ability to synthesize the enzyme catalase
...
This allows the bacteria to hide in
blood clots
 It can also hide from them by producing slime layers which enable them to remain unseen
 The production of toxins

o

Staphylococcus can cause a number of diseases such as:
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

o

Food poisoning by the ingestion of enterotoxin-containing food
Scalded skin syndrome
Impetigo
Toxic shock syndrome
 Caused by the TSS toxin which is absorbed into the blood

A separate table shows the diagnosis, treatment and prevention of this bacteria

Streptococcus
o

Streptococcus is another genus of Gram-positive, cocci bacteria and is of the Streptococcaceae family



Currently, there are over 50 species recognised in this genus
They are usually found in chains or pairs

o

Like Staphylococcus, Streptococcus are non-motile due to their lack of exterior movement-producing
structures such as a flagellum
 Again, like Staphylococcus, this genus is a facultative anaerobe

o

Species of Streptococcus can be separated into groups A-F
 Group A contains a specifically pathogenic species known as Streptococcus pyogenes
 S
...
pyogenes typically infects the pharynx or the skin as it is spread through respiratory
droplets
 They can also be found where other, normal skin flora have been depleted
 This particular bacterium can cause a number of diseases:
 Pharyngitis
o This is the inflammation of the pharynx
 Scarlet Fever
o This can occur following pharyngitis and can cause a rash on the chest that
spreads across the body
 Necrotizing fasciitis
o This occurs following a co-infection with S
...
The Streptococcus
enters the body and spreads along the muscle tissue
o Enzymes are then secreted that destroy the surrounding tissue

Mycobacterium
o

Finally, Mycobacterium, another Gram-positive bacterium happens to be another non-spore forming
genus of bacteria, of the family Mycobacteriaceae

o

This genus of bacteria can be identified due to its particularly slow growth
 This genus is quite special as it can become protected from lysis once it has been
phagocytosed
 It is also resistant to Gram stains, detergents, and many antimicrobial drugs

o

The main species associated with this genus is M
...
tuberculosis
 Reactivated/Secondary tuberculosis
 This is the reestablishment of an active infection after a period of dormancy
 Disseminated tuberculosis
 This results when the infection spreads throughout the body
 The symptoms arise when there are complications at the various sites involved



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