25 Pathogenic Bacteria Examples: Detailed Explanations

Pathogenic bacteria cause diseases in humans as well as in animals.

The pathogenic bacteria can cause many diseases in humans. In nature many types of pathogenic bacteria are there.

Pathogenic bacteria examples

Escherichia Coli:

E.Coli is a gram negative facultative anaerobic colini form bacteria. Most of the E.coli are not pathogenic but some of them are more pathogenic. E.Coli is usually found in intestine. They cause urimary tract infections, bacteremia, cholecystitis, vomiting, diarrhea, stomach clumps. This is transmitted from contaminated food. It can be cured by using antibiotics like sulfamethoxazole or trimethoxazole.

Mycobacterium tuberculosis:

Mycobacterium tuberculosis is an aerobic gram positive rod shaped bacteria. Tuberculosis is caused by mycobacterium species. It is easily treated in early stages but in later stage the prolonged treatment is required as it develops multidrug resistance.

Streptococcus Pneumonia:

Streptococcus pneumonia is a gram positive aero tolerant anaerobic spherical bacteria. The main source of transmission of it is nasal drops of an infected person. It can cause pneumonia with the symptoms like throat pain, fever and headache, red and swollen tonsils. It is treated by using antibiotics.

Staphylococcus aureus:

Staphylococcus aureus is a gram positive round shaped bacteria. It is commonly known as normal flora which is present on skin. It causes soft tissue diseases. It can be cured by using antibiotics like penicillin.

Clostridium botulinum:

Clostridium botulinum is an anaerobic gram positive rod shaped bacteria. It produces toxins and causes botulism it is a serious disease in humans. The usual source of transmission of this disease is contaminated food. It can be treated by using antibiotics.

Vibrio cholerae:

Vibrio cholerae is a facultative anaerobic gram negative comma shaped bacteria. It is transmitted through the contaminated food. It causes cholera in humans which results in diarrhea.

Bacillus anthrax:

Bacillus anthrax is gram positive bacilli (rod shaped). It is transmitted from soil/ drainage / diseased animals but not through the man to man contact. It causes Anthrax disease, the symptoms include fever, sore throat, nausea, diarrhea and headache.

Yersinia pestis:

Yersinia pestis is a non-spore forming bacterium. It causes plague disease in humans and most commonly in animals. It is transmitted by the bites of animals like rats, mouse, squirrels which are infected earlier.

 Salmonella entrica:

Salmonella entrica is a gram negative, facultative anaerobic bacilli. It causes typhoid fever and usually transmitted through contaminated food (raw meat, egg) and water.

Camphylobacter jejuni:

Camphylobacter jejuni is a microaerophilic and gram negative bacterium. It causes diarrhoea in humans and transmitted through contaminated food or raw food items like meat, poultry items.

Listeria monocytogenes:

Listeria monocytogenes is a facultative anaerobic bacterium. It grows mostly in wet environment even under refrigeration. The diseases caused by this are intrauterine infections, meningitis and sometimes there is a chance of abortions in pregnant women.

Vibrio parahaemolyticus:

Vibrio parahaemolyticus is gram negative, facultative anaerobic bacilli. It is most commonly found in sea water, sea food. It causes diarrhoea, vomiting, nausea, fever, stomach pain. It is transmitted through the consumption of sea water.

Coronobacter sakazakii:

Coronobacter sakazakii is a gram negative bacilli. It usually grow in dry environment. On dry food items like milk powder, herbal teas etc. It commonly infects the adults and infants too.

In infants the symptoms include fever, poor feeding and faint or dullness.

Actinomyces israelii:

Actinomyces israelii is a gram positive bacilli. It causes actinomycosis which may results in sinus problem. It infects commonly lungs, liver, neck parts. It is usually seen on the skin and mouth parts.

Bacteroids fragilis:

Bacteroids fragilis is a gram negative anaerobic bacteria. It is commonly present at human colonal parts. It causes diarrhoea, abdominal pain. It usually non- pathogenic but it can be infectious if it enters the blood stream while surgeries, trauma.

Borrelia garinii:

Borrelia garinii is a gram negative spirochete and can be found in sea bird ticks. It causes lyme disease which include skin complications.

Clostridium perfingens:

Clostridium perfingens is a gram positive, anaerobic bacilli. It is transmitted through contaminated and unprocessed or raw food items like meat, poultry. It may cause fever, diarrhea and stomach-ache.

Clostridium tetani:

Clostridium tetani is an anaerobic gram positive rod shaped bacteria. It is mostly present in soil. It causes jaw pain, muscle pain and difficulty in swallowing. As it is a spore forming bacteria the spore can be found everywhere.

Enterococcus faecalis:

Enterococcus faecalis is a gram positive, facultative anaerobic bacilli. It is transmitted in poor hygienic conditions from person to person. The symptoms include fever, diarrhea, vomiting,  nausea.

Haemophilus influenza:

Haemophilus influenza is a gram negative facultative anaerobic bacterium. It is transmitted through nasal droplets from the infected persons. It causes influenza in humans. The symptoms include difficulty in breath, fever, diarrhea etc.

Helicobacter pyroli:

Helicobacter pyroli is a gram negative, spherical bacteria. It is transmitted through the contaminated food items and raw food items like meat, salty food and dried food. It causes abdominal pain, nausea, gastritis.

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Klebsiella pneumonia:

Klebsiella pneumonia is gram negative, non-motile bacteria. It is transmitted from person to person and contaminated medical equipment which are used to clean wounds. It causes meningitis, pneumonia, surgical or wound infections.

 Leptospira species:

Leptospira species are gram negative, spriochetes. It causes leptospirosis which is also known as Weir’s disease. It infects both humans and animals. Usually it is transmitted through mice, cattle and pigs.

Mycoplasma pneumonia:

Mycoplasma pneumonia is a gram negative bacteria. It causes pneumonia. The symptoms include fever, dry cough and difficulty in breath. It is transmitted from nasal droplets of the infected persons.


Neisseria is a gram negative cocci bacterial species. It is commonly known as a normal flora and present on the upper respiratory part of human beings. It causes meningococcal disease. The symptoms include blood infection, damage of spinal card.


Shigella is an anaerobic bacteria. The main source of transmission is contaminated food and water. It causes diarrhea, fever and stomach-ache. It can be treated by using antibiotics. This commonly infects toddlers rather than adults.

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