Post on 27-Oct-2014
GRAM POSITIVE COCCI
STREPTOCOCCI
STREPTOCOCCI
• Gram (+) spherical cells, arranged in chains or pairs
• Grayish pinpoint translucent to slightly opaque colonies
• Catalase (-), oxidase (-)• Growth is enhanced by
blood, serum or glucose incorporated in agar plate
STREPTOCOCCI
• Behave-like facultative anaerobe, some species require increased CO2 for growth
• Aerotolerant anaerobe (peptostreptococci – obligate anaerobe
STREPTOCOCCI
• ALL streptococci EXCEPT the viridans group have a layer of C carbohydrate – serological classification
• Young cultures are characterized by the presence of capsule
• Are commonly found as part of normal human flora.
STREPTOCOCCI
• However, when these organism gain access to normally sterile sites they can cause life threatening infection.• S. pyogenes and S. pneumoniae - notorious pathogens• Aerococcus, Lactobacillus, Leuconostoc and
Pediococcus – resemble streptococci
STREPTOCOCCI
• Colony variationa.Mucoidb.Matte or rough – large amount of CHONc.Smooth/glossy – little amount of CHON
CLASSIFICATION OF STREPTOCOCCI
A. ACADEMIC/BERGEY’S CLASSIFICATION• BASED ON TEMPERATURE
1. PYOGENIC GROUP
•Will not grow neither on 10°C or 45°C•Produce pus; mostly β-hemolytic•Species: Streptococcus pyogenes
2. VIRIDANS GROUP
• Will grow at 45°C• NOT part of the lancefield group• Alpha hemolytic OR Non hemolytic• Species: S. salivarius, S. mutans, S. mitis, S.
sanguis
3. ENTEROCOCCUS
•Will grow both at 10°C and 45°C•Normal flora of human intestine•Species: E. faecalis
4. LACTIC GROUP
• Will grow on 10°C• Non hemolytic organism• Often found in dairy products• Species: S. lactis
CLASSIFICATION OF STREPTOCOCCI
B. SMITH AND BROWN’S CLASSIFICATION•BASED ON HEMOLYTIC PATTERN
1. ALPHA-HEMOLYTIC STREPTOCOCCI
• Partial/incomplete hemolysis of RBC around colony
• Green discoloration around colony
• Species: • S. pneumoniae
(green streptococci)
2. BETA-HEMOLYTIC STREPTOCOCCI
• Complete hemolysis of RBCs around the colony
• Clear area/zone around colony
• Yellow discoloration• Species: S. pyogenes, S. agalactiae
3. GAMMA-HEMOLYTIC STREPTOCOCCI
• NO lysis of RBCs around colony/red cells immediately surrounding the colony are unaffected (no change)
• Species: E. faecalis (GROUP D)
CLASSIFICATION OF STREPTOCOCCI
C. LANCEFIELD•BASED ON THE ANTIGENIC NATURE OF CELL WALL CARBOHYDRATES – C POLYSACCHARIDE•Rebecca Lancefield – found out that C carbohydrate can be extracted from the streptococcal cell wall by placing the organism in dilute acid and heating for 10 min.
GROUP A STREPTOCOCCI
• Pathogenic to man• Not considered part of the normal flora• Acquired thru contaminated droplets by
cough or sneeze• Species: S. pyogenes – “fever producing
bacteria,” flesh eating bacteria (involves deeper tissues and organs)
GROUP A STREPTOCOCCI
• Principal virulence factor: M-protein (type specific; anti-phagocytic)• Other virulence factor:
a.Protein F – mediates epithelial cell attachment
b.Lipoteichoic acid – bacterial adherence to the respiratory epithelium
ENZYMES AND TOXINS PRODUCED BY S. pyogenes
1. HEMOLYSINSA. STREPTOLYSIN O - “Oxygen labile”; highly antigenic - responsible for subsurface hemolysis on BAP - cause lysis of WBC, platelets, tissue cells - ASO test – detects recent infection w/ S. pyogenes
ENZYMES AND TOXINS PRODUCED BY S. pyogenes
B. STREPTOLYSIN S - “Oxygen stable”; non antigenic - responsible for surface hemolysis on BAP - it causes lysis of WBCs
2. DEOXYRIBONUCLEASES
ENZYMES AND TOXINS PRODUCED BY S. pyogenes
3. STREPTOKINASE - a protein that binds to plasminogen and activates the production of plasmin - it allows the bacteria to move from clotted area - it activates a host blood-factor that dissolves fibrin clots
ENZYMES AND TOXINS PRODUCED BY S. pyogenes
4. HYALURONIDASE - to separate the tissue and spread the organism
5. PYROGENIC (ERYTHROGENIC) TOXINS - serotypes A, B, C - exotoxin B (cysteine protease) – degrades proteins
INFECTIONS AND DISEASES
1. PHARYNGITIS OR TONSILITTIS – “STREP THROAT”
2. SCARLETT FEVER (SCARLATINA)
• Results from a throat infection with a strain of S. pyogenes that carries a lysogenic bacteriophage.• Acquired through respiratory droplet• Cardinal signs: diffused red rash on the upper
chest and spreads to the trunk and extremities and strawberry colored-tongue• Caused by the release of erythrogenic
toxin/strep pyrogenic exotoxin
2. SCARLETT FEVER (SCARLATINA)
2. SCARLETT FEVER (SCARLATINA)
• DICK’S TEST (ERYTHROGENIC TOXIN) - susceptibility test for scarlet fever - (+) erythema – redness• SCHULTZ CHARLTON REACTION - diagnostic test for scarlet fever - used to diagnostic present scarlet fever - (+) “blanching phenomenon” – rash fade
3. SKIN INFECTIONS
• CELLULITIS - is a diffuse, spreading
infection of subcutaneous skin tissue characterized by a defined area of redness (erythema) and accumulation of fluid (edema)
3. SKIN INFECTIONS
• ERYSIPELAS - is an acute infection
and inflammation of the dermal layer of the skin characterized by painful reddish patches that enlarge and thicken with sharply defined edges
- may also lead to necrotizing fasciitis and myositis – “galloping gangrene”
3. SKIN INFECTIONS
• RHEUMATIC FEVER
• ACUTE GLOMERULONEPHRITIS OR BRIGHT’S DISEASE
- inflammatory disease of the renal glomeruli; results from the deposition of antigen-antibody complexes.
DIAGNOSTIC TESTS
BACITRACIN DISK TEST
• Differentiates S. pyogenes from other β-hemolytic group
• Result: (+) any zone of inhibition
• Group C and G are also susceptible
SULFAMETHOXAZOLE-TRIMETHOPRIM TEST
• Positive: Any zone of inhibition
• Negative: No Zone of inhibition
• (Group A and Group B)
SXT
SXT
L-pyrrolidonyl-β-napththylamide (PYR) TEST
• Specific than Bacitracin test
(+) bright/cherry red color (β-napththylamide) upon adding 0.01% cinnamaldehyde reagent
(-) no color changeOther PYR test positive
organisms: Enterococcus, Aerococcus, Gemella
GROUP B STREPTOCOCCI
• Part of the normal flora of female genital tract and lower GIT
• Nosocomially transmitted by unwashed hands of mother or healthcare personnel.
• Infection of fetuses and infants – infection during passage through the colonized birth canal, and premature rupture of mother’s membranes
GROUP B STREPTOCOCCI
• On culture, it is grayish white mucoid w/ small zone of beta hemolysis
• Species: S. agalactiae• Virulence factor: capsule (sialic acid –
signifiant component of the capsule)• Enzymes: hemolysin, CAMP factor,
neuraminidase, deoxyribonuclease, hyaluronidase and protease
DISEASES AND INFECTIONS
• Pneumonia• Neonatal Meningitis• Neonatal sepsis• Postpartum infection• Osteomyelitis• UTI• endocarditis
DIAGNOSTIC TESTS
CAMP TEST
• To differentiate S. agalactiae from other β-hemolytic streptococci
• It uses β-lysin – producing strain of S. aureus or disk impregnated w/ β lysin
• Result (+) arrow-head β-hemolysis near S. aureus growth / (+) bowtie appearance
HIPPURATE HYDROLYSIS TEST
• S. agalactiae possesses the enzyme hippuricase
• Reagent: sodium + ninhydrin
• Results (+) Purple color after
adding Ninhydrin rgt (indicates hippurate hydrolysis)
(-) no color change
GROUP C STREPTOCOCCI
• Main source of streptokinase; animal pathogen
• Species: S. equi, S. equisimilis, S. dysagalactiae, S. zoopedimicus
GROUP D STREPTOCOCCI
• Enterococci: E. faecalis, E. faecium, E. avium, E. gallinarium
• Non enterococci: S. bovis, S. equinus
Enterococci are not highly pathogenic; cocci in pairs and long chains
DIAGNOSTIC TEST
GROWTH IN BILE ESCULIN MEDIUM
• Reagent: Esculin + 1-4% bile salt
Result:(+) Black color(BOTH enterococci and
non enterococci)
6.5% NaCl (nutrient broth base) test
• Result:(+) turbididty –
enterococci (also PYR +)
(-) non enterococci
LAP Test
• Detects for the ability of the bacteria to hydrolyze Leucine-β-naphthylamide by enzyme leucine aminopeptidase to β-naphthylamide. Positive: Development of a red color within
1 minute after adding cinnamaldehyde reagent (S. Pneumoniae and S. pyogenes, Enterococcus, Pediococcus )
Negative: No color change or development of slight yellow color(Aerococcus and Leuconostoc)
NOTES
• Enterococci – (+) bile esculin, growth in 6.5% NaCl. PYR test and LAP test; vancomycin resistant
• Leuconostoc, Pediococcus, Globicatella, S. urinalis, Lactococcus – (+) growth in bile esculin and 6.5% NaCl
• All enterococci isolated from human hydrolyze PYR
NOTES
• Isolation of S. bovis from a blood culture may be the first indication that the patient has an occult tumor in the GI tract (GI cancer)• 85% of Group B streptococci is (+) w/ growth
in 6.5% NaCl but (-) in bile esculin test• E. faecalis requires cyanocobalamin (B12) as
growth factor.
GROUP F and G
• Minute streptococci w/ wide zone of beta hemolysis
• Species: S. anginosus
VIRIDANS STREPTOCOCCI
• Alpha hemolytic streptococci that lack the lancefield group antigens and do not fall on the criteria for S. pneumoniae, can be non-hemolytic.
• Oropharyngeal commensals• Opporunistic pathogens of low virulence• Glucans and dextrans – enhance attachment
to host cell surfaces
VIRIDANS STREPTOCOCCI
• Laboratory tests: bile insoluble, optochin resistant, no growth in 6.5% NaCl, (-) inulin fermentation and PYR (-)
• Species: S. mutans, S. salivarius, S. mitis• Infections: subacute endocarditis, dental
carries (S. mutans)
ABIOTROPHIA
• Pyridoxal-dependent or Vit B6 dependent and symbiotic streptococci
• Formerly known as nutritionally variant streptococci (NVS)
• Thiol compounds – cystein, Vit B6 and pyridoxal
• This group of organism were found as satellites around an organism that produces pyridoxal – E. coli, Klebsiella spp.,Enterobacter spp., yeasts
ABIOTROPHIA
• They produce satellatism w/ Staphylococcus• Opportunistic pathogens of low virulence• Variable morphology – gram (+) to gram (-) to
gram variable; pleomorphic forms• It causes 5-6% endocarditis
LABORATORY DIAGNOSISSTREPTOCOCCUS SPP.
1. Gram Stain2. Culture – BAP, PEA, CNA, CAP
• For isolation of Group A streptococci from throat swab, BAP w/ SXT is used to suppress the growth of normal flora.
• To detect genital carriage of Group B streptococci during pregnancy, Todd Hewitt broth w/ antibiotics (gentamicin, nalidixic acid or colistin and nalidixic acis) is used to suppress vaginal flora.
• Visualization of beta hemolysis is enhanced by anaerobic condition (BAP should be inoculated by stabbing the inoculating loop into the agar several times)
• CAP is incubated w/ 5-10% CO2• Abiotrophia will not grow on BAP or CAP
unless pyridoxal (B6) is supplied.• Streptococci has tendency to produce
increase amount of lactic acid and other organic acid from fermentation of sugar resulting to acidic medium and eventually their growth is inhibited.
3. Susceptibility Test – bacitracin disk test SXT test4. CAMP and Hippurate test5. Bile Esculin and Salt Tolerance Test6. Serological Test
a.Latex agglutinationb.ASO titer testc.ELISAd.Co-agglutination
Streptococcus pneumoniae
• Diplococcus/pneumococcus• Gram (+) cocci in pairs, oval or lancet shape;
facultatively anaerobe• Causative agent of lobar pneumonia• Considered part of the normal flora (25-50%)
of the URT of preschool children• Most common bacterial pneumonia in elderly
as well as in patients w/ underlying disease.
Streptococcus pneumoniae
• Most common cause of bacterial meningitis in adults• Common isolate both as a pathogen and as a
member of the normal respiratory tract.• Principal virulence factor: antiphagocytic
capsular polysaccharide – type 3 strains• Opsonization of the capsule renders the
organism non virulent
Streptococcus pneumoniae
• The capsule is antigenic and can be identified w/ appropriate antiserum; it is composed of hyaluronic acid.
• Alpha hemolytic colonies, mucoid, flattened with depressed center.
• “dome-shaped,” glistening, wet, mucoid – young colonies
• “coin w/ a raise rim” – old colonies (due to autolytic changes)
Streptococcus pneumoniae
• Dimple-shaped/donut-shaped colonies• Enzymes: hemolysin, immunoglobulin A
protease, neuraminidase and hyaluronidase
INFECTIONS/DISEASES PRODUCED
1. Pneumonia - pneumonia due to S. pneumoniae is
not usually a primary infection but rather a result of disturbance of the normal defense barriers.
2. Meningitis3. Otitis media4. Bacteremia5. Endocarditis6. Peritonitis
Differential Test Result
1. Optochin Susceptibility/P disk Test
• Presumptive test• Ethylhydroxycuprein
hydrochloride• BAP (sensitivity media)
> Or = 14mm
2. Bile Solubility•Confirmatory test•Differentiates pneumococcus from viridans streptococci•Sodium desoxycholate•When a heavy suspension of pneumococcus is added to bile salt, the cloudiness of the broth clears after 3 hrs incubation.
(+) soluble
Differential Test Result
3. Neufeld Quellung Reaction•The antipnemococcal serum is mixed w/ sputum, CSF and other sources along w/ methylene blue•Examined under OIO
SWELLING CAPSULE
4. Mouse Virulence Death of the animal
5. Inulin Fermentation Test (+) Fermentation