Gram Positive Cocci and Gram Negative Cocci Flashcards
Which genera are in the Micrococcaeceae Family?
Staphylococcus, Micrococcus, and Stomatococcus
Staphylococci characteristics:
Part of normal skin flora and mucous membranes; facultative anaerobic GPC that tend to form clusters on gram stain
Micrococcus characterisitics:
Often appear as tetrads and produce lemon-yellow colonies; normal on skin and mucous membranes; rarely cause disease
Stomatococcus mucilaginosus
Rarely causes disease; normal oral cavity flora; catalase negative, modified oxidase negative, resistant to bacitracin, susceptible to furazolidone, and encapsulated
How are Staphylococcus and Micrococcus differentiated from each other?
Both are catalase positive unlike Stomatococcus; Staphylococcus is susceptible to furazolidone and lysostaphin but resistant to bacitracin; whereas, Micrococcus is the opposite. Micrococcus is also modified oxidase positive while the other two are negative.
Mannitol Salt Agar (MSA)
a selective and differential media used for staph (the high salt concentration inhibits most GNRs and other GPs). When mannitol is fermented, the pH indicator (phenol red) turns from red to yellow.
Staphylococcus aureus diseases:
- Invasive diseases: skin infections (folliculitis), abscesses, wound infections, osteomyelitis, pneumonia, and endocarditis
- Toxigenic: Food poisoning, Scalded Skin Syndrome, Toxic Shock Syndrome
Coagulase Negative Staph Diseases:
- Associated with indwelling medical devices
- UTIs (S. saprophyticus is a leading cause of UTIs in young, sexually active females)
- Immunocompromised individuals
Staphylococcus aureus biochemicals
Tube coagulase positive and mannitol salt agar positive (yellow); Subspecies aureus is D-mannose positive while subspp. anaerobius is negative
Coagulase Negative Staphylococcus biochemicals
S. saprophyticus- Resistant to novobiocin
S. lugdunesis- ODH positive
S. schleiferi- DNase positive
Streptococcus Characteristics:
Catalase negative, facultative anaerobic GPC that form chains; four naming systems for species
Four naming systems for streptococci
- Serogrouping/ Lancefield grouping: based on cell wall antigens (group A, B, etc)
- Physiological properties: based on biochemical reactions
- Hemolytic activity: alpha, beta, and gamme hemolysis groups
- Common names: ex- B strep or pneumococci
Group A Streptococcus (GAS)/ S. pyogenes Diseases
Not part of the normal flora for humans although some may be asymptomatic carriers; suppurative (pus forming); pharyngitis (strep throat), scarlet fever, bacteremia, skin infections (cellulitis, erypsipelas, pyoderma), toxic shock syndrome
Group B Streptococcus (GBS)/ S. agalactiae Diseases
normal genitourinary tract flora; most common cause of neonatal sepsis and meningitis; can cause UTIs, skin and soft tissue infections, postpartum fever, and sepsis
Group C, F, and G Streptococci Diseases
normal respiratory, gastrointestinal, and vaginal flora; can cause bacteremia, endocarditis, and wound infections
Group D Streptococcus/ S. bovis Diseases
normal GI tract inhabitant; associated with colon cancer (Biotype 1) and gall bladder disease (Biotype 2); can cause bacteremia and endocarditis;
Streptococcus pneumoniae Diseases
normal habitat is the upper resp. tract; causes pneumonia (most common cause of community bacterial pneumonia), bacteremia, meningitis, and otitis media
Viridans Streptococci Diseases
inhabit resp. tract, GI tract, and skin; cause endocarditis in patients with artificial heart valves, dental carries, wound infections, and brain abscesses
Streptococcus-Like Bacteria Diseases
found on mucous membranes; infections are rare, but includes endocarditis, bacteremia, osteomyelitis, and wound infections
Which Streptococcus species has a rapid antigen test?
GAS has a rapid antigen detection test for pharyngitis
GAS Identification
large B hemolytic zone, susceptible to bacitracin, resistant to SXT, PYR positive;
B hemolysis is caused by two toxins (Streptolysin S and streptolysin O) - SLS is oxygen stable and SLO is not, so organisms with only SLO will not be Beta aerobically unless the agar is stabbed to create an anaerobic environment
GBS Identification
small zone of B hemolysis (some are nonhemolytic), CAMP positive, hippurate positive, carrot broth positive, and resistant to both bacitracin and SXT
Large colony vs small colony Group C and G
Large colony are VP negative whereas small colony are part of the S. anginosus group and are VP positive
Group D Identification
alpha or gamma hemolytic, bile esculin positive, NaCl negative, PYR negative, resistant to bacitracin; Biotype 1 produces glucan and ferments mannitol (Biotype 2 does not)
S. pneumoniae Identification
alpha hemolytic, bile soluble, susceptible to optochin at low concentrations (P disk)
Viridans Streptococci Identification
Resistant to optochin, not bile soluble, bile esculin negative
1. S. mitis group: VP negative, urease negative and S. oralis/mitis are ADH negative, while others in the group are positive
2. S. anginosus group: VP positive, ADH positive, urease negative, PYR negative
3. S. mutans: VP positive, ADH negative, mannitol positive, urease negative
4. S salivarius group: VP positive, ADH negative, mannitol negative, S. vestibularis is urease positive while S. salivarius is negative
Enterococcus Characteristics
GPC in pairs or chains, bile esculin positive, NaCl positive, PYR positive, catalase negative; can be resistant to vancomycin
Enterococcus Species Identification
E. faecalis: Arabinose negative, nonmotile, lactose positive
E solitarius: Arabinose negative, nonmotile, sucrose positive
E. seriolicida: Arabinose negative, nonmotile, sucrose negative
E. faecium: Arabinose positive and nonmotile
E. gallinarum: Arabinose positive, motile, ADH positive
E. casseliflavus: Arabinose positive, motile, ADH negative
Aerococcus Characteristics
microaerophilic, cause UTIs, endocarditis, peritonitis, and lymphodenitis; all species can grow in NaCl and are susceptible to vancomycin and catalase negative
Aerococcus Species Identification
A. urinae: LAP positive and PYR negative
A. sanguicola: LAP positive and PYR positive
A. viridans: LAP negative and PYR positive
A. christensenii: LAP negative and PYR negative
Staph-Like GPC Identification (all catalase negative)
Pediococcus: Resistant to vancomycin, LAP positive, glucose negative, PYR negative, esculin variable
Dolosigranulum: PYR positive, susceptible to vancomycin, LAP positive, NaCl negative, esculin positive
Helococcus: susceptible to vancomycin, PYR positive, LAP negative, esculin positive
Gemella haemolysans: susceptible to vancomycin, PYR positive, esculin negative, LAP positive, NaCl positive
Strep-like GPC Identification (all catalase negative)
Leuconostoc: resistant to vancomycin, ADH negative, glucose positive
Weissella: resistant to vancomycin, ADH positive, glucose positive
Abiotrophia: susceptible to vancomycin, LAP negative, does not grow at 10C, a-galactosidase and b-galactosidase positive
Dolosicoccus: susceptible to vancomycin, LAP positive, NaCl negative
Globicatella: susceptible to vancomycin, LAP positive, NaCl positive
Granulicatella: susceptible to vancomycin, LAP negative, does not grow at 10C, galactosidase negative
Lactococcus: susceptible to vancomycin, LAP negative, grows at 10C, nonmotile
Vagococcus: susceptible to vancomycin, LAP negative, grows at 10C, motile
Neisseria spp. Characteristics
oxidase positive, nonmotile, nitrate negative, GN diplococci that have a kidney bean shape, commonly found in PMNs, catalase positive, and part of normal human flora, typically mucous membranes
Which Neisseria spp. is not normal flora?
N. gonnorrhoeae
Culture conditions for Neisseria
aerobic, grows at 35C with increased CO2 and humidity; N. gonnorrhoeae and meningitidis require CHOC
Neisseria gonnorrhoeae diseases
causes gonorrhea (STD): first infects mucosal membranes in the pharynx, anus, or urogenital tract
It can spread to the bloodstream and lead to septic arthritis and skin leasions
Symptoms of gonorrhea in men
acute urethritis (urethral discharge and painful urination), can spread to the prostate and epididymis
Symptoms of gonorrhea in women
can be asymptomatic; cervicitis, vaginal discharge, dysuria, fever, pain, endometritis, urethral infection, and pelvic inflammatory disease (can lead to infected fallopian tubes and ovaries)
Specimen transport for N. gonnorrhoeae
- Collect on a Dacron or rayon swab instead of cotton or calcium alginate
- Should not refrigerate because it is sensitive to cold
- Gonococci become nonviable when incubated for prolonged periods (similar to STREPN; it has autolytic enzymes)
Neisseria meningitidis diseases
normal upper respiratory flora; can cause meningococcemia (blood), meningitis (with petechiae-skin lesions), Waterhouse-Friderichsen syndrome (characterized by shock, large lesions, and internal bleeding), death
Diseases caused by other Neisseria species
cause endocarditis, meningitis, bacteremia, osteomyelitis, and other opportunistic infections
Moraxella catarrhalis diseases
can cause respiratory tract infections, bacteremia, and endocarditis; normal upper respiratory flora
N. gonorrhoeae Identification
glucose positive, nitrate negative, DNase negative, hydroxyprolyl aminopeptidase positive, superoxyl positive
Moraxella catarrhalis Identification
glucose, maltose, lactose, and sucrose negative; nitrate, butyrate esterase, and DNase positive
N. meningitidis Identification
glucose, maltose, and y-glutamyl aminopeptidase positive; lactose sucrose, nitrate, and DNase negative
N. lactamica Identification
glucose, maltose, lactose, and B-galatosidase positive; sucrose, nitrate, and DNase negative
N. sicca Identification
glucose, maltose, sucrose positive; lactose, DNase negative
N. flavescens Identification
negative to everything
N. mucosa Identification
fructose positive while others are negative
Haemophilus spp. Characteristics
normal flora of the upper respiratory tract except H. ducreyi and H. influenzae biogroup aegyptius; small, nonmotile, pleomorphic GNRs, facultative anaerobes, oxidase positive
H. influenzae Diseases
meningitis, bacteremia, epiglottitis, otitis media, sinusitis, and pneumonia; biogroup aegyptius causes pinkeye and Brazilian purpuric fever
Types of H. influenzae
- Typeable - 6 types with polysaccharide capsules
- Untypeable - unencapsulated strains
H. ducreyi Diseases
STI characterized by a painful chancroid (“soft chancre”) that can progress to regional lymphadenitis; associated with poverty, prostitution, and drug use
H. influenzae Identification
Requires X and V Factor, nonhemolytic, ferments glucose
H. ducreyi Identification
Requires X factor; “schools of fish” or “railroad track” staining; GS-HgS agar should be used for isolation
H. parainfluenzae Identification
Requires V Factor, nonhemolytic, and glucose, sucrose, and mannose positive
H. haemolyticus Identification
Requires X and V Factor, B hemolytic, and glucose positive
H. parahaemolyticus Identification
Requires V Factor, B hemolytic, and glucose and sucrose positive
H. aegyptius Identification
Requires X and V Factor, nonhemolytic, and glucose positive
H. pittmoniae Identification
Requires V Factor, glucose, sucrose, and mannose positive
H. paraphrohaemolyticus Identification
Requires V Factor, glucose and sucrose positive
