Microbiology Term

Streptococcus agalactiae

• A gram-positive, beta-hemolytic bacterium that commonly colonizes the gastrointestinal and genitourinary tracts of healthy adults

• It grows in chains and is classified as Group B streptococcus.

• Major cause of neonatal infections, including sepsis, pneumonia, and meningitis 

• It also causes urinary tract infections, bloodstream infections, and skin and soft tissue infections in adults, particularly those with weakened immune systems.

• The bacterium is primarily spread through direct contact and from mother to infant during labor and delivery

• Not transmitted through casual contact

Streptococcus mutans

• Gram-positive, facultative anaerobic bacterium commonly found in the human mouth

• part of the normal oral microbiota and grows in chains

• The primary bacterium associated with dental caries

• The acid it produces can erode tooth enamel, leading to cavities.

• Commonly transmitted through saliva, such as sharing utensils, kissing, or from parent to children

Streptococcus pneumoniae

• Gram-positive, alpha-hemolytic bacterium that typically appears as lancet-shaped diplococci

• Commonly found in the upper respiratory tract of healthy individuals, it has a protective polysaccharide capsule that increases its virulence

• Major cause of community-acquired pneumonia, meningitis, sinusitis, otitis media, and bloodstream infections

• Spreads through respiratory droplets produced when an infected person coughs, sneezes, or talks

• Close contact increases the risk of transmission 

Streptococcus pyogenes

• Gram-positive, beta-hemolytic bacterium that grows in chains

• Causes a variety of infections, ranging from mild illnesses such as strep throat and impetigo 

• To severe cases like necrotizing fasciitis, scarlet fever, rheumatic fever, and streptococcal toxic shock syndrome

• Spreads through respiratory droplets from coughing or sneezing and through direct contact with infected wounds or skin lesions

Treponema pallidum

• Gram-negative, spiral-shaped bacterium known as a spirochete

• Causative agent of syphilis, a sexually transmitted infection that progresses through primary, secondary, latent, and tertiary stages if left untreated

• Can affect the skin, mucous membranes, cardiovascular system, and nervous system.

• Primarily transmitted through sexual contact with an infected person

• Can also be passed from a pregnant mother to her fetus, causing congenital syphilis

• Transmission occurs through direct contact with syphilitic sores

Vancomycin-resistant Enterococcus (VRE)

• Gram-positive cocci that normally live in the human intestines and female reproductive tract

• Developed resistance to vancomycin 

• Causes urinary tract infections, bloodstream infections, wound infections, and endocarditis. 

• Spreads through direct contact with infected or colonized individuals, contaminated surfaces, medical equipment, or the hands of healthcare workers

Vancomycin-resistant Staphylococcus aureus (VRSA)

• Gram-positive coccus that typically appears in clusters under a microscope

• Can cause a variety of infections, including skin and soft tissue infections, pneumonia, bloodstream infections, surgical site infections, and endocarditis

• Resistant to vancomycin

• Spread through direct contact with infected wounds, contaminated surfaces, medical equipment, or the hands of healthcare workers. 

Vibrio cholerae

• Gram-positive, comma-shaped bacterium commonly found in contaminated water sources 

• Causes cholera, an acute diarrheal illness characterized by profuse watery diarrhea, vomiting, and rapid dehydration.

• Spread through the consumption of contaminated water or food

Creutzfeldt-Jakob disease (CJD)

• Rare, fatal neurodegenerative disorder caused by abnormal proteins called prions

• contain no genetic material and cause disease by inducing normal proteins in the brain to become misfolded.

• Leads to rapid brain deterioration, causing symptoms such as memory loss, personality changes, difficulty walking, impaired coordination, vision problems, and dementia

• Progresses quickly and is almost always fatal

• Occurs spontaneously, while others are inherited through genetic mutations 

• Rarely, CJD can be transmitted through contaminated medical instruments, tissue transplants, or certain medical procedures involving infected nervous system tissue

Trichomonas vaginalis

• Single-celled protozoan parasite that causes sexually transmitted infection trichomoniasis

• One of the most common nonviral sexually transmitted infections worldwide

• In women, it can cause vaginal itching, burning, redness, discomfort during urination, and a frothy yellow-green vaginal discharge

• Men are often asymptomatic but may experience irritation inside the penis, burning during urination, or discharge

• Primarily transmitted through sexual contact with an infected person

Blastomyces dermatitidis

• Dimorphic fungus, meaning it exists as a mold in the environment and transforms into a yeast form in human tissue

• Commonly found in moist soil and decaying organic matter, particularly near rivers, lakes, and wooded areas

• Causes blastomycosis, an infection that primarily affects the lungs but can spread to the skin, bones, genitourinary system, and central nervous system. 

• Symptoms may include cough, fever, chest pain, fatigue, weight loss, and skin lesions

• Infection occurs when a person inhales airborne fungal spores released from disturbed soil

• Not spread from person to person

Candida albicans

• Yeast-like fungus that normally lives on the skin and in the mouth, gastrointestinal tract, and vagina as a part of the body's normal microbiota

• The most common cause of candidiasis, which can range from mild infections such as oral thrush and vaginal yeast infections to severe systemic infections affecting the bloodstream and internal organs

• Most infections result from the overgrowth of the organism already present in the body, rather than transmission from another person

• Occasionally spread through direct contact or contaminated medical devices 

Coccidioides

• Dimorphic fungus that lives in dry, sandy soil, particularly in the southwestern United States, Mexico, and parts of central and South America

• Causes Valley Fever

• Infection occurs when fungal spores become airborne and are inhaled, often after soil is disturbed by wind, construction, farming, or excavation 

• Not spread from person to person

Histoplasma capsulatum

• Dimorphic fungus that exists as a mold in the environment and as a yeast in human tissues

• Commonly found in soil contaminated with bird or bat droppings

• Causes histoplasmosis, a fungal infection that primarily affects the lungs

• Infection occurs when fungal spores become airborne and are inhaled

• Not spread from person to person

Pneumocystis jirovecii

• A fungus that primarily affects the lungs

• Causes Pneumocystis pneumonia, a serious lung infection

• Common in people with HIV/AIDS, cancer patients undergoing chemotherapy, organ transplant recipients, and others who are immunocompromised

• Spread through airborne transmission when a person inhales infectious particles 

• Many people may be exposed during childhood without developing the illness

• Disease typically occurs when the immune system becomes weakened. 

Acinetobacter

• Gram-negative, aerobic coccobacillus commonly found in soil, water, and healthcare environments

• known for its ability to survive on surfaces for extended periods and for developing resistance to multiple antibiotics

• a major cause of healthcare-associated infections, particularly in ICUs

• Can cause pneumonia, bloodstream infections, UTI, wound infections, and surgical site infections

• Spread through direct contact with contaminated surfaces, medical equipment, or the hands of healthcare workers

Bacillus Anthracis

• Gram-positive, rod shaped bacterium that forms highly resistant endospores

• Can survive in soil for many years and are capable of causing infection when they enter the body

• Causative agent of anthrax, a serious infectious disease that can affect the skin, lungs, or gastrointestinal tract

• Become infected through contact with infected animals or animal products, inhalation of spores, or consumption of contaminated meat

• Not spread from person to person

Bacteroides Fragilis

• Gram-negative, anaerobic, rod-shaped bacterium that is part of the normal microbiota of the human gastrointestinal tract.

• can cause serious infections when it escapes the gastrointestinal tract through surgery, trauma, or intestinal perforation

• Commonly associated with intra-abdominal abscesses, wound infections, bloodstream infections, and pelvic infections

• Infections are usually endogenous, meaning they arise from the patient’s own normal intestinal flora rather than being spread from person to person

Bartonella

• Gram-negative, rod-shaped bacterium that primarily infects red blood cells and the cells lining blood vessels

• Commonly causes cat scratch disease, which typically presents with swollen lymph nodes, fever, fatigue, and a small bump or blister at the site of a scratch or bite

• Most commonly transmitted through scratches, bites, or saliva from infected cats especially kittens

Bordetella Pertussis

• Small, Gram-negative coccobacillus that infects the respiratory tract

• Causative agent of pertussis, commonly known as whooping cough

• Spreads through respiratory droplets when an infected person coughs, sneezes, or talks

• Highly contagious, especially among individuals who are not vaccinated

Campylobacter Jejuni

• Gram-negative, curved or spiral-shaped bacterium that is highly motile due to its flagella

• Causes bacterial gastroenteritis worldwide

• Causes campylobacteriosis, an intestinal infection characterized by diarrhea, abdominal cramps, fever, nausea, and vomiting

• In rare cases, infection can lead to complications such as reactive arthritis or Guillain-Barre Syndrome

• Usually transmitted through the consumption of undercooked poultry, unpasteurized milk, contaminated water, or cross-contaminated foods

• Contact with infected animals can also spread the infection

Chlamydia Trachomatis

• Gram-negative, obligate intracellular bacterium, meaning it can only grow and reproduce inside living host cells

• Most common cause of STIs worldwide

• Causes Chlamydia

• Transmitted through sexual contact, including vagina, anal, and oral sex with an infected person

Clostridium Botulinum

• Gram-positive, anaerobic, spore-forming, rod-shaped bacterium

• Causes botulism, a rare but serious illness that affects the nervous system

• Can occur through the ingestion of improperly canned or preserved foods

Clostridium Difficile

• Gram-positive, anaerobic, spore-forming, rod-shaped bacterium

• A major cause of antibiotic-associated diarrhea and colitis

• Occurs after the use of broad-spectrum antibiotics

• Spreads through the fecal-oral route

• Can become infected by touching contaminated surfaces, medical equipment, or the hands of healthcare workers and then touching their mouth

Clostridium Perfringens

• Gram-positive, anaerobic, spore-forming, rod-shaped bacterium commonly found in soil, sewage, and the intestines of humans and animals

• Known for causing gas gangrene, a rapidly progressing infection that destroys muscle tissue

• Common cause of food poisoning

• Can occur when spores enter wounds contaminated with soil or fecal material

Clostridium Tetani

• Gram-positive, anaerobic, spore-forming, rod-shaped bacterium commonly found in soil, dust, and animal feces

• The causative agent of tetanus, a serious disease characterized by muscle stiffness and painful spasms

• Enters the body through contaminated wounds, puncture injuries, burns, or cuts

• Not spread from person to person

Corynebacterium Diphtheriae

• Gram-positive, club-shaped, non-spore-forming bacterium

• Causes Diphtheria, a serious infection that primarily affects the upper respiratory tract

• Spreads through respiratory droplets from coughing or sneezing and through direct contact with infected individuals or contaminated objects

Enterococcus

• Gram-positive cocci that typically occur in pairs or short chains

• They are part of the normal intestinal microbiota, enterococci can cause opportunistic infections, particularly in hospitalized patients

• Can spread through direct contact with contaminated surfaces, medical equipment, or the hands of healthcare workers

Escherichia Coli

• Gram-negative, rod-shaped bacterium that normally lives in the intestines of humans and animals

• Common cause of urinary tract infections, bloodstream infections, and gastrointestinal diseases

• Commonly transmitted through contaminated food or water, particularly undercooked ground beef, unpasteurized milk, raw vegetables, and person-to-person contact through poor hygiene practices

Gardnerella Vaginalis

• Gram-variable, facultative anaerobic bacterium that is commonly found in the female genital tract

• Primary bacterium associated with bacterial vaginosis, the most common vaginal infection in women of reproductive age

• Sexual activity can increase the risk of developing it

Haemophilus Influenzae

• Small, Gram-negative coccobacillus that commonly inhabits the human respiratory tract

• Can cause a variety of infections, including meningitis, pneumonia, epiglottitis, sinusitis, otitis media, and bloodstream infections

• Spreads through respiratory droplets produced when an infected person coughs or sneezes

Helicobacter Pylori

• Gram-negative, spiral-shaped bacterium that colonizes the stomach lining

• Major cause of chronic gastritis and is strongly associated with peptic ulcers of the stomach and duodenum

• Thought to spread through oral-oral or fecal-oral routes, often through contaminated food, water, or close personal contact with infected individuals

Klebsiella Pneumoniae

• Gram-negative, rod-shaped bacterium

• Can cause pneumonia, UTIs, bloodstream infections, wound infections, and meningitis

• Spreads through direct contact with contaminated surfaces, medical equipment, or the hands of healthcare workers

• Can also spread from person to person in healthcare settings

Lactobacillus

• Gram-positive, rod-shaped bacteria

• Generally considered beneficial bacteria because they help maintain a healthy balance of microorganisms

• Help prevent the growth of harmful bacteria and yeast

• Naturally acquired from the environment, food, and contact with other individuals

• Commonly found in fermented foods such as yogurt, kefir, and certain cheeses

Legionella Pneumophila

• Gram-negative, aerobic, rod-shaped bacterium commonly found in freshwater environments

• Causative agent of Legionnaires’ disease, a severe form of pneumonia

• Can also cause a milder illness known as Pontiac fever, resembles the flu

• Transmitted through the inhalation of contaminated water droplets or aerosols

• Not spread from person to person’

Listeria Monocytogenes

• Gram-positive, facultative intracellular, rod-shaped bacterium

• Causes listeriosis, a serious foodborne illness

• Primarily transmitted through contaminated foods such as unpasteurized milk and cheese, deli meats, hot dogs, smoked seafood, and raw vegetables

• Pregnant women can also transmit the infection to their unborn babies, potentially causing miscarriage, stillbirth, or neonatal infection