Gram positive bacteria are bacteria which appears blue when stained by gram staining technique; reflecting the colour of primary stain (either gentian violet, crystal violet or methyl violet)

Examples of gram positive bacteria of medical importance include, Staphylococci aureus, Staphylococcus epidemidis, Staphylococcus saprophyticus, Streptococci pyogenes, Streptococcus agalactiae, Streptococcal pneumoniae, Clostridium and Bacillus species

General Characteristic

They are gram positive cocci bacteria in clusters

They are round shaped

All are catalase positive (produce enzyme, catalase that resists the effect of hydrogen peroxide.)

They produce beta lactamase enzyme making it resistant to penicillin

Staphylococcus aureus is coagulase positive (they cause clotting of plasma, hence they are resistant to phagocytosis

Septicemia is a serious bloodstream infection. It’s also known as bacteremia, or blood poisoning. Septicemia occurs when a bacterial infection elsewhere in the body, such as in the lungs or skin, enters the bloodstream

is an infection in a bone. Infections can reach a bone by traveling through the bloodstream or spreading from nearby tissue.

In most cases, a bacteria called Staphylococcus aureus, a type of staph bacteria, causes osteomyelitis…. Bone surgery, including hip and knee replacements, also increase the chance of bone infection.

Neonatal sepsis is a type of neonatal infection and specifically refers to the presence in a newborn baby of a bacterial blood stream infection (BSI) (such as meningitis, pneumonia, pyelonephritis, or gastroenteritis) in the setting of fever. Older textbooks may refer to neonatal sepsis as “sepsis neonatorum”

is a form of endocarditis. It is an inflammation of the inner tissues of the Prosthetic valve endocarditis is commonly caused by Staphylococcus epidermidis as it is capable of growing as a biofilm on plastic surfaces.

General Characteristics

Gram positive cocci in short and long chains

All are catalase negative

Two methods are used to classify Streptococci, which are

According to their level of haemolysis in blood agar

Alpha haemolytic streptococci (partial hemolysis) for example S. pneumoniae,

Beta haemolytic streptococci (complete haemolysis) for examples S. pyogenes

According to lancefield grouping (based on antigenic differences in their cell walls)

Streptococci are arranged into lancefield groups A to U denoting the antigenic mark. Example of lancefield group A is S. pyogenes and lancefield group B S. agalactiae

The rest of lancefield groups ‘C’ to ‘U’ will not be discussed at this point

inflammation of the pharynx, causing a sore throat.

Otitis media (OM) is any inflammation of the middle ear, without reference to etiology or pathogenesis. Acute otitis media with purulent effusion behind a bulging tympanic membrane. Chronic suppurative otitis media is a persistent ear infection.

Sinusitis is an inflammation or swelling of the tissue lining the sinuses…. Acute sinusitis usually starts with coldlike symptoms such as a runny, stuffy nose and facial pain…. Chronic inflammation symptoms last 12 weeks or longer.

Botulism is a rare and potentially fatal illness caused by a toxin, produced by the bacterium Clostridium botulinum.

a swollen area within body tissue, containing an accumulation of pus

Mastitis is a condition which causes a woman’s breast tissue to become painful and inflamed. It’s most common in breastfeeding women,

Conjunctivitis is a common condition that causes redness and inflammation of the thin layer of tissue that covers the front of the eye

General Characteristics of Clostridium Bacteria

Contain species of gram positive anaerobic spore forming rods

Few are aero tolerant (Aerobic)

They are widely distributed in soil and in the gut of man and animals

They are saprophytic bacteria

The spores are resistant to environmental conditions

The major diseases associated with these species are tetanus, gangrene, botulism food poisoning, and pseudo membranous colitis

In each of these, the production of potent protein exotoxins is an important course of pathology. Example clostridium tetani, clostridium perfringens, clostridium botulinum, clostridium difficile

Tetanus is a serious but rare condition caused by bacteria getting into a wound. Read about the symptoms, how it’s treated, and the tetanus vaccination.

Gas gangrene (also known as clostridial myonecrosis and myonecrosis) is a bacterial infection that produces gas in tissues in gangrene. This deadly form ofgangrene usually is caused by Clostridium perfringens bacteria. It is a medical emergency.

Gastroenteritis is a very common condition that causes diarrhoea and vomiting. It’s usually caused by a bacterial or viral tummy bug…. Cases in adults are usually caused by norovirus (the “winter vomiting bug”) or bacterial food poisoning.

colitis, is inflammation of the colon associated with an overgrowth of the bacterium Clostridium difficile

Meningitis is an inflammation (swelling) of the protective membranes covering the brain and spinal cord known as the meninges. This inflammation is usually caused by an infection of the fluid surrounding the brain and spinal cord. Meningitis is usually caused by bacteria or viruses…‎Fungal Meningitis · ‎Bacterial Meningitis · ‎Viral Meningitis

General Characteristic of Bacillus Group

Widely distributed in nature

Most of them live as saprophytes in the soil, dust, water and vegetation

They are able to form resistant spores

Their spores are centrally located

Spores are formed only after the organism is shed from the body

They are strictly aerobes

Bacillus anthracis is a major pathogen of cattle, sheep, goats, and pigs

The bacilli are excreted in the feaces, urine, and saliva of infected animals

Bacilli can also be found in pastures which have been contaminated by anthrax spores form bodies of dead animals, and can remain the source of infection for many years

The size of the spore is the same as the size of the width of the bacteria

Cutaneous anthrax is the most common form of anthrax infection, and it is also considered to be the least dangerous. Infection usually develops from 1 to 7 days after exposure. Without treatment, up to 20% of people with cutaneous anthrax may die

Gram positive bacteria are determined by gram staining when they retain the colour of primary stain.

There is a large group of gram positive bacteria but only some causes diseases to man.

These including staphylococcus species, streptococcus species, clostridium species and bacillus species.

Most of these bacteria are detected or diagnosed by gram staining of the direct sample however, most of clostridium species requires culture of the tissue or sample before staining.

What are Gram positive bacteria?

What are the examples of gram positive organisms of medical importance?

What are the morphological differences of staphylococci and streptococci groups?

What are the diseases caused by staphylococci aureus?

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Monica, C. (1987). Medical Laboratory Manual for Tropical Countries (2nd ed.) Volume 1 Oxford: ELBS Butterworth, Heinemann Ltd.

Monica, C. (1998). District Laboratory Practice in Tropical Countries. Part 1. Tropical Health Technology. Noida, India: Gapson Papers Ltd.

Monica, C. (2000). District Laboratory Practice in Tropical Countries. Part 2. Tropical Health Technology. UK: Cambridge University Press.

Satish, G. (1982). The short Handbook of Medical Microbiology. New Delhi. India: Jaypee Brothers Medical Publishers PVT Ltd.