Gram + Flashcards
Staphylococcus aureus
Coagulate +, penicillin sensitive. Resistant statins reported. Beta hemolysis.
Found on nasal membrane, skin, gastrointestinal and urinary tracts.
Causes: boils,abscesses, wound infection, pneumonia, toxic shock syndrome,food poisoning and other diseases.
Staphylococcus
Cocci in grape like clusters, aerobic or facultative anaerobes, salt tolerant, inhibit skin, nose, mouth of humans. Most are commensals, pathogens are indicated by production of coagulase.
Staphylococcus epidermidis
Common skin resident, sometimes responsible for Endocarditis and for infection of patients with lowered resistance like wound infection, surgical infection, urinary tract infection.
Antibiotic resistant staphylococcus
Resistance to Methicillin : methicillin resistant staphylococcus aureus (MRSA) obtained from genetic elements received from other organism.
Resistant to Vancomycin : the drug of last resort
Important Streptococci
Streptococcus pyrogens : streptococcal sore throat, acute glomeruli nephritis, rheumatic fever
Streptococcus pneumoniae: lobar pneumonia and otitis media, meningitis infections with heigh fatality rates.
Hemolytic A type streptococcus known as “flesh eating” bacterium.
Streptococcus mutants: dental caries
Penicillin sensitive , resistant strains reported.
Important Enterococci
Enterococcus faecalis : opportunistic pathogen, urinary tract infection and endocarditis
Important Lactococci
Lactococcus lactis: production of buttermilk and cheese
Streptococci features
Non-motile, Aerotolerant and strict anaerobes, homolactic fermentation, Lancefield grouping system: based on polysaccharide and techoic acid antigen in cell walls or between cell walls and plasma membrane. Cocci in chains.
Found in mouth, intestine and genital tracts of humans and animals. Highly fermentative, produces a variety of exotoxins and hydrolytic enzymes. Differentiated by hemolysis on blood agar and by serotyping(Lancefield grouping A-M)
Mollicutes ( Mycoplasmas)
Low G+C Gram +
Lack cell walls, pleomorphic, cannot synthesize peptidoglycan precursors, penicillin resistant, sterols may stabilize plasma membrane, most nonmotile, some have gliding motility, have very small genome, most facultative anaerobics, found in animals, colonize mucous membrane and joints.
Important pathogen of Gram positive Mycoplasma
Mycoplasma mycoides : bovin pleuropneumonia in cattles
Mycoplasma gallisepticum : chronic respiratory disease in chickens
Mycoplasma hyopneumoniae: pneumonia in swine
Mycoplasma pneumoniae: primary atypical pneumonia in humans
Mycoplasma hominis and Ureaplasma urealyticum : human pathogens
Spiroplasmas: pathogenic in insects, ticks, and variety of plants.
Important Species of Bacillus
B. subtilis: important experimental organism.Various species produce antibiotics
B. cereus : food poisoning
B. anthracis: anthrax
B. thuringiensis and B. sphaericus : used as insecticide, they have parasporal body ( solid protein crystal that contains toxin)
Clostridium
Low G+C Gram +
Fermentative metabolism, ferment amino acids using Strickland reaction ( oxidation of one amino acid and using another as electron acceptor), fermentation products responsible for unpleasant odors associated with putrefaction. Obligate anaerobic, spore forming bacilli (terminal spores). Distributed widely in soil and fecal matter. Human pathogen responsible for anaerobic infections and intoxications. Oxygen sensitive, prefer high protein medium. May produce lethal intoxications.
Important Colstridium
C. Botulinum: food spoilage ( specially canned food); botulism
C. tetani: tetanus (lethal intoxications)
C. Perfringnes: gas gangrene ( produces necrotizing infections)
C. Acetobutylicum: manufacture of butanol
C. Dificile: pseudomembranous colitis.
Sensitive to penicillin and vancomycin
Listeria
Short rods, motile by peritrichous flagella, aerobic and facultative anaerobes, catalase +, common on decaying matter like L. Monocytogens- listeriosis, food-borne disease
Lactobacillus
Sometimes coccobacilli, grow optimally in slightly acidic conditions( pH 4.5-6.4), carry out either homolactic fermentation ( via glycolysis pathway) or heterolactic fermentation ( via pentose phosphate pathway), widely distributed in nature, on plants surfaces, in dairy products, meat, water, sewage, beer, fruits, and other, normal flora of mouth and intestinal tract and vagina. Usually non pathogenic. Nonsporeforming