Gram +

Question 0

Staphylococcus aureus

Answer 0

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.

Question 1

Staphylococcus

Answer 1

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.

Question 2

Staphylococcus epidermidis

Answer 2

Common skin resident, sometimes responsible for Endocarditis and for infection of patients with lowered resistance like wound infection, surgical infection, urinary tract infection.

Question 3

Antibiotic resistant staphylococcus

Answer 3

Resistance to Methicillin : methicillin resistant staphylococcus aureus (MRSA) obtained from genetic elements received from other organism.
Resistant to Vancomycin : the drug of last resort

Question 4

Important Streptococci

Answer 4

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.

Question 5

Important Enterococci

Answer 5

Enterococcus faecalis : opportunistic pathogen, urinary tract infection and endocarditis

Question 6

Important Lactococci

Answer 6

Lactococcus lactis: production of buttermilk and cheese

Question 7

Streptococci features

Answer 7

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)

Question 8

Mollicutes ( Mycoplasmas)

Low G+C Gram +

Answer 8

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.

Question 9

Important pathogen of Gram positive Mycoplasma

Answer 9

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.

Question 10

Important Species of Bacillus

Answer 10

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)

Question 11

Clostridium

Low G+C Gram +

Answer 11

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.

Question 12

Important Colstridium

Answer 12

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

Question 13

Listeria

Answer 13

Short rods, motile by peritrichous flagella, aerobic and facultative anaerobes, catalase +, common on decaying matter like L. Monocytogens- listeriosis, food-borne disease

Question 14

Lactobacillus

Answer 14

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

Question 15

Importance of Lactobacillus

Answer 15

Fermented vegetable ( sauerkraut, pickles and silage),Fermented beverages ( wine, beer, juices),Sour dough bread,Swiss cheese and other hard cheeses,Yogurt, sausages
Spoilage of beer, milk and meat

Question 16

Leuconostoc

Answer 16

Carry out heterolactic fermentation via phosphoketolase pathway

Question 17

Importance of Leuconostoc

Answer 17

Wine production, sauerkraut and pickles production, buttermilk, butter and cheese, synthesis of dextrans ( L. mesenteroides), involved in food spoilage, tolerate high sugar concentration, grow in heavy syrups

Question 18

Corynebacterium

Answer 18

Harmless soil and water saprophytes, pleomorphic, many are animal and human pathogens, C. Diphtheriae : diphtheria
Catalase +, fermentative, metachromatic granules
Penicillin sensitive,toxin is unaffected, DPT shots to immunize against toxin.
Often found on human skin occasionally in mucous membanes

Question 19

Propionibacterium

Answer 19

In Skin and in digestive tract of animals, also in dairy products such as cheese, used in products of Swiss cheese.
P.acne: involved in development of body odor and acne vulgaris.
Fermentation produces propionate and acetate and often gas, catalase +, anaerobic to aero tolerant , pleomorphic, nonmotile rods, nonsporing, may be bifid or branched.
Sensitive to Tetracycline and oxidizing compounds(e.g. Benzoyl peroxide)
Often found on human skin occasionally in mucous membanes

Question 20

Mycobacterium

Answer 20

Straight or slightly curved rods, sometimes branched, Acid Fast, nonmotile, nonsporing, aerobic, catalase +, can form filaments that are readily fragmented, walls have high lipid content ( waxes with 60-90 carbon “mycolic acids”), in soil and water, some parasite.

Question 21

Important species of Mycobacterium

Answer 21

M. Bovis: tuberculosis in cattle and other ruminants
M. Tuberculosis: tuberculosis in humans
M. Leprae : leprosy
M. Avium: infections seen in immunocompromised hosts.

Question 22

Nocardia

Answer 22

Gram +, acid fast, isolated from soil, Rudimentary to extensive vegetative hyphae that can fragment into rod shaped and coccoid forms, Aerobic, Aerial hyphae formed, catalase +, Type IV cell wall, widely distributed in soil.

Question 23

Impact of Nocardia

Answer 23

Most are free living saprophytes, can degrade many molecules,(e.g. Petroleum hydrocarbons, detergents, benzene), involved in biodegradation of rubber joints in water and swage pipes, some are opportunistic pathogens causing Nocardiosis. Nocardia asteroides usually infect lungs, can infect central nervous system.

Question 24

General properties of Actinomycetes

Answer 24

Gram +, straight or slightly curved rods and form branching filaments or hyphae with true branching, may have swollen clubbed or clavate ends,form asexual spores ( withstand desiccation but not heat), usually nonmotile ( spore may be motile by flagella), Aerobic, require co2 for best growth, normal flora of mucosal surfaces(specially oral cavity) of humans and other animals,
Conidiophores : conidia , sporangiophores : spores form within sporangium, thallus: tissue like mass formed by some actinomycetes , aerial hypha, form mycelia

Question 25

Practical importance of actinomycetes

Answer 25

Widely distributed in soil, degrade wide variety of organic compounds, important in mineralization process, produce most of medically important natural antibiotics, some are pathogenic in humans, other animals and plants.

Question 26

Actinomycetes e.g.

Answer 26

A. Bovis : lumpy jaw in cattle

A. Israeli : most important human pathogen, actinomycoses- ocular disease and periodontal disease in humans.

Question 27

Micrococcus

Answer 27

Cocci in pairs, tetrads, or irregular clusters, usually nonmotile,Aerobic, colonies usually yellow or red, catalase +, with respiratory metabolism, primarily on mammalian skin and in soil, nutritionally very flexible, can degrade some herbicides and pesticides, important in mineralization process,very resistant to desiccation and nutrient deprivation. Aerobic inhabitants of skin in mammals.

Question 28

Arthrobacter

Answer 28

Young cells are irregular rods, older cells are small cocci, usually nonmotile, Aerobic, have rod-coccus growth cycle, metabolism respiratory catalase +, mainly in soil,
nutritionally very flexible, can degrade some herbicides and pesticides, important in mineralization process,very resistant to desiccation and nutrient deprivation

Question 29

Streptomyces ( soil bacteria)

Answer 29

Vegetative mycelium extensively branched, Aerial mycelium forms chains of three to many spors, Aerobic, form discrete lichenoid, leathery, or butyrous colonies that often are pigmented, use many different organic compounds as nutrients, soil organisms (1-20% of culturable soil microbiota), produce Geosmin ( volatile substance that is source of moist earth odor), important in mineralization process, aerobically degrade many resistant substances(e.g. Pectin lignin, and chitin), produce vast array of antibiotic, most are nonpathogenic saprophytes
Produces streptomycin

Question 30

Pathogenic Streptomyces

Answer 30

Streptomyces scabies: scab disease in potatoes and beets
Streptomyces somaliensis: actinomycetoma, infection of subcutaneous tissues in humans, lead to swelling abscesses and bone destruction

Question 31

Bifidobacterium

Answer 31

Rods of varied shapes, usually nonmotile, Anaerobic, cells can be clubbed or branched, pairs often in V arrangement, ferment carbohydrates to acetate and lactate, but no CO2, catalase negative, found in intestinal and reproductive tracts of humans and animals, probiotic

Question 32

Bifidobacterium e.g.

Answer 32

Bifidobacterium bifidus : pioneer colonizer of human intestinal tract, does not appear to be major cause of disease

Question 33

Frankia

Answer 33

Vegetative hyphae with limited to extensive branching and no aerial mycelium, multilocular sporangia formed, Aerobic to microaerotolerant, sporangiospores, nonmotile, usually fixes nitrogen, lives In association with plant roots.

Question 34

E.g. Of Actinobacterium (High G+C Gram Positive)

Answer 34

Actinomycetes, Micrococcus, Corynebacterium, Mycobacterium, Propionobacterium, Streptomyces, Frankia, Bifidobacteria, Nocardia

Question 35

Bacillus

Low G+C Gram +

Answer 35

Aerobic/facultative anaerobic, spore forming bacilli, widely distributed in nature.
Sensitive to penicillin and vancomycin

Question 36

Listeria e.g. Gram+

Answer 36

L. Monocytogenes : pathogenic and produces a serious condition known as listeriosis, specially harmful to fetuses and young children. Acquired by ingesting unpasteurized or improperly pasteurized milk. recently found in processed beet and pork frankfurters. Nonsporforming