Bacteria to Know Bio 251

Mycobacterium tuberculosis

• Blood sputum and cottage cheese like clumps

• Slow growing colonies

• Distinctive colorless granulated colonies 

• Waxy appearance

• Mycolic acid coat (protects bacteria from pathogens and blocks gram stain reagents)

• Needs acid fast stain test to be seen

• Causes TB

Mycobacterium leprae

• Hansen’s disease

• Found in peripheral body regions (cooler areas)

Corynebacterium

• Found in environment (soil, water, plant surfaces), human skin, and mucous membranes

• Often harmless (unless toxin producing)

• Generally facultative anaerobes

• Gram + rods (form v shape)

Corynebacterium diphtheriae

• Cause of diphtheria (respiratory tract)

• Produces toxin

Clostridium

• Gram + rods

• Obligate anaerobes

• Endospore former

• Found in soil and aquatic sediments rich in organic nutrients

• Produce toxins

Clostridium botulinum

• Gram +

• Causes food poisoning

• Produces toxin

• Endospores found in soil

• May infect infants

• Colonization of intestinal tract after spore ingestion (honey, improper home canning)

Clostridium perfringens

• Gram +

• Myonecrosis (gas gangrene)

• Food poisoning

• Wound infections (anaerobic environment)

Clostridium tetani

• Gram +

• Produces toxin

• Found in soil 

• May contaminate deep wounds 

• Causes tetanus

Clostridium difficile

• Gram +

• Causes severe form of colitis

• Most severe cases are often deadly

Streptococcus

• Gram + cocci

• Obligate fermenters (Lactic acid bacteria)

• Grow in chains (cocci in chains or pairs)

• Some species are a major part of normal microbiota

• Many species cause infectious diseases in humans

• There are greater than 50 recognized species in this genus

• Usually classified by serotypes called Lancefield groups and their ability to lyse red blood cells when grown on blood agar

Streptococcus pyogenes

• Gram +

• Beta-hemolytic group A

• Pyogenic pathogen (pus production)

• Nonpyogenic - commensals in human mouth 

• S.mutans - dental caries

• Occasionally  normal flora (upper respiratory tract, <15% of population)

• Common cause of bacterial pharyngitis

• Skin infections, lesions (impetigo)

• Necrotizing fasciitis (serious; flesh eating)

Streptococcus pneumoniae

• Gram +

• Cocci in pairs

• Virulent strains produce a capsule 

• Less virulent strains or nonvirulent don’t produce a capsule

• Alpha-hemolytic

• A non-Lancefield group

• Vaccine made from capsular polysaccharides

• Can also cause Meningitis, Septicemia, osteomyelitis, Endocarditis (especially in newborns, the elderly, and patients with immunodeficiency)

Lactobacillus

• Gram +

• Most aerotolerant anaerobes

• Fermentative 

• Not killed by oxygen 

• Have probiotic potential and therefore applied in dairy (cheese, yogurt, fermented milk) and nondairy products like sausages, juices, as well as in animal feed

• Very diverse

• Not pathogenic

• Part of normal microbiota - GI tract, vagina (contribute to acidity of vagina)

• Inhibit growth of pathogenic yeast (Candida albicans)

• Antibiotics can disrupt normal microbiota and may lead to secondary infections (i.e yeast infection)

Bacillus (genus)

• Gram + rods

• Form endospores 

• Obligate aerobes or facultative anaerobes 

• Found in environment (soil), animals 

• 100’s of name species

• Source of some antibiotics

• Important pathogenic species

• Opportunistic infections 

• Food poisoning (B. cereus)

• Anthrax (B. anthracis)

Bacillus cereus

• Gram + rods (forms chains)

• Common soil bacterium 

• Often found in milk 

• A pathogen that may cause food poisoning

• Colonies appear milky white with irregular shapes when cultured on blood agar

Bacillus anthracis

• Gram +

• Disease that affects wild and domestic animals 

• In humans: charcoal-black ulcers on the skin, severe enterocolitis, pneumonia, and brain damage due to swelling

• Often fatal if untreated

Staphylococcus

• Gram +

• 2 species associated with humans

Staphylococcus aureus

• Gram +

• Various locales (nasal membranes)

• Pathogenic

• Skin infections that produce boils, carbuncles, cellulitis, or impetigo

• Dome strains produce enterotoxin - staph food poisoning

• Enterotoxin that causes toxic shock - can be fatal

• Many strains have developed resistance to antibiotics (these can be hard to treat; resistant to nearly all available antibiotics) (Methicillin resistant and Vancomycin resistant)

Staphylococcus epidermidis

• Gram +

• Skin, mucous membranes

• Rarely pathogenic (except for immunocompromised)

• Skin wounds, artificial joints, intravenous catheters

• Problematic in hospital settings

Pseudomonas

• Gram -

• Aerobic; do not ferment

• Found widespread in soil and water 

• Motile, polar flagella 

• Able to form biofilms 

• Produces pigments

• Cause diverse infections in many body locations (infects wounds and burns)

• Urinary tract infections; often chronic

• Nosocomial pneumonia, Septicemia (immunosuppressed patients and infants), Chronic lung infection (cystic fibrosis patients, patients on ventilators), eye infections, swimmer’s ear

Vibrio

• Gram - rods; often curved 

• Facultative anaerobes 

• Found in aquatic environment, more alkaline; water and food

• Transmission: water contact; ingestion of contaminated water or food (especially seafood)

• Not common in the U.S (people who travel are more susceptible)

Vibrio cholerae

• Gram - 

• Causes hypersecretion of electrolytes and water in the large intestine

• Leads to watery diarrhea and dehydration

• Toxin is produced

Legionella pneumophila

• Gram - 

• Aquatic environment

• Often reside in Protozoa

• Obligate aerobes

• Causes respiratory disease

• Difficult to culture; Charcoal-containing media

• Thrives in warm water

Escherichia coli

• Gram - rod

• Habitat: intestinal tract of humans and animals

• Most strains mutualistic with humans

• Often used as indicator for fecal contamination 

• Some strains are highly pathogenic (O157:H7)

• Foodborne infections, intestinal tract infections, urinary tract infections

• Shiga toxin - potent toxin (inhibits protein synthesis)

• Hemorrhagic colitis, inflammation of intestinal tract, blood diarrhea

• Hemolytic uremic syndrome in severe cases

Salmonella

• Gram - 

• Many species (unclear how many); lots of serotypes

• Identify using antisera

• Inflammation of intestine, fever, vomiting, diarrhea

• Food poisoning

• Gastroenteritis

• Typhoid fever is caused by the species (serovar typhi, enterobacteria)

Mycobacterium

• is neither gram + or -

• has mycolic acid

• Obligate aerobe

• Widespread in nature

• Rods (variable)

• Waxy lipid (mycolic acid coat)

• Acid fast

• Hard to kill with some antibiotics and disinfectants

Mycoplasma

• is neither gram + or -

• lacks a cell wall

• Causing walking pneumonia

Mycoplasma pneumoniae

• causes walking pneumonia

• mild/moderate

• dry cough

• no capsule

Streptococcus pneumonia

• causes pneumonia

• has a polysaccharide capsule (important virulence factor)

• rust color sputum

• more severe