MILAGROS YAMAMOTO, M.D, FPCP, FPCC SECTION OF CARDIOLOGY USTH
P B Valenzuela, MD, FPCP Internal Medicine – Infectious Diseases.
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Transcript of P B Valenzuela, MD, FPCP Internal Medicine – Infectious Diseases.
P B Valenzuela, MD, FPCPInternal Medicine – Infectious Diseases
Classify the gram-positive organisms and enumerate their member-species of medical importance
Describe the gram positive organisms by their growth, colonial and morphologic characteristics
Correlate clinical findings with the organisms’ antigenic and virulence determinants
Offer treatment options
The Gram-positive cocci◦ Staphylococci◦ Streptococci
The Gram-positive bacilli ◦ Spore-forming◦ Non-spore-forming
2 medically important genera◦ Staphylococci◦ Streptococci
Non-motile, non-spore-formers
2H202 2H2O + O2 Hydrogen Peroxide
Staphylococci: Catalase +Streptococci: Catalase -
Catalase bubbles
Gram-positive, spherical, in grape-like irregular clusters
Gray to golden-yellow colonies (S. aureus)
Gray to white (S. epid)
Staphylococcus aureus
Coagulase-negative staphylococci
Staphylococcus epidermidis
Staphylococcus saprophyticus
Gram Stain + coccus + coccus + coccus
Alpha Toxin + — —
Mannitol fermentation + — +/-
coagulase + — —
Novobiocin senstivity + + —
Cell wall◦ Peptidoglycan
Elicits production of interleukin -1, opsonic antibodies Chemoattractant for PMNs Activates complement
◦ Teichoic acids - antigenic◦ Protein A (in many S. aureus strains)
Binds to the Fc region of IgG Decreases the efficiency by which S aureus are
opsonized and phagocytosed
Capsule◦ Present in some strains◦ Inhibit phagocytosis by PMNs
Surface ProteinsAdhesins◦ Coagulase
Considered synonymous with invasive pathogenic potential Binds to prothrombin thrombin fibrinogen fibrin..... attaches to surface of staph Alters ingestion/destruction by phagocytic cells
◦ Clumping factors Bind to fibrinogen and fibrin Produces the typical clusters of staphylococci when mixed
with plasma Aid in adherence to traumatized skin
Toxins◦ α toxin: hemolysis of erythrocytes, necrosis of
skin, and release of cytokines and eicosanoids that may produce shock
◦ β toxin: sphingomyelinase; act on lipid membranes
◦ γ toxin: three proteins that interact with the two proteins of PVL --- form 6 toxins WBC lysis by causing pore formation in the cellular
membranes◦ δ toxin: disrupts biologic membranes
*All 4 are also called hemolysins
◦ Panton-Valentine Leukocidin (PVL) Synergistic with γ toxin Pore-forming cytotoxin; lysis of WBCs,
◦ Exfoliative toxins: dissolves the mucopolysaccharide matrix of the epidermis desquamation, seen in staphylococcal scalded skin syndrome (SSSS); promotes spread of staph under the statum corneum. Epidermolytic toxin A: chromosomal gene product;
heat stable Epidermolytic toxin B: plasmid-mediated; heat labile
Both are superantigens
◦ Toxic Shock Syndrome Toxin (TSST) In ~20% of S. aureus isolates Associated with fever, shock, multisystem involvement,
desquamation◦ Enterotoxins
~50% of S. aureus strains can produce >/= 1 enteroroxin Produced when S. aureus grows in CHO and CHON foods Heat –stable; resistant to gut enzymes Important cause of food poisoning – vomiting and diarrhea toxin acts on the gut neural receptors stimulation of
the vomiting center
Natural reservoir: Humans and other mammals
S. epidermidis: part of the normal flora of the skin, respiratory tract and the GI tract
S. saprophyticus: UTI in young women Colonization of the anterior nares with S.
aureus : 20-50%; also found on the axilla, perineum, vagina
Prototype lesion: furuncle/localized abscess
Coagulase fibrin formation of abscess wallAccumulation of inflammatory cellsLiquefaction of necrotic tissue in the center of lesionDrainage Slow filling of the cavity with granulation tissue
healing
Skin and soft tisssue infections Invasive infections Device-related infections
Toxin-mediated syndromes
Skin/Soft tissue Impetigo Cellulitis Abscess Bullous impetigo Wound infection
Disseminated Infection Endocarditis Osteomyelitis Pulmonary infections
Secondary localization Focal suppuration
Toxin-mediated◦ Toxic Shock Syndrome
Abrupt onset of fever, vomiting, diarrhea, myalgia, rash, hypotension
Multiorgan failure Background of infected wound, tampon use, localized infections
◦ SSSS fever widespread tender erythema that quickly forms thin-walled,
fluid-containing bullae that rupture, leaving a moist base of skin
◦ Food poisoning Short incubation period: 1-8 hours No fever Nausea, vomiting, diarrhea Rapid recovery
Drainage◦ For abscesses
Antimicrobial therapy◦ S. aureus
90 % Penicillin-resistant 35% methicillin-resistant; correlates with (+) mecA
Mueller-hinton agar with 6 ug/mL oxacillin/ commercial assay/ PCR
DOC: Beta lactamase resistant penicillins: Nafcillin/methicillin/ Oxacillin/Dicloxacillin/ Cloxacillin
IV antibiotics for severe infections Vancomycin, for MRSA Linezolid, Daptomycin, quinopristin-dalfopristin
Antimicrobial therapy◦ S. epidermidis
75% are resistant to nafcillin/oxa/methicillin DOC: Vancomycin
◦ S. saprophyticus DOC: Amoxicillin-clavulanic acid, cephalosporins
2H202 2H2O + O2 Hydrogen Peroxide
Staphylococci: Catalase +Streptococci: Catalase –
Note: Nonstreptococcal Catalase-negative Gram-positive cocci and coccobacilli (Aerococcus, Gemella, Leuconostoc, Pediococcus, Lactobacillus)
Catalase
bubbles
Gram +, spherical, in pairs and chains
Gram stain of sputum (X1000)
Colony morphology and hemolytic reactions Serologic specificity of the cell wall
◦ group-specific substance (Lancefiled classification)◦ Other cell wall and capsular antigens
Biochemical reactions◦ Sugar fermentation reactions; tests for the
presence of enzymes; susceptibility ◦ Used for species that typically do not react with
antibody tests for the group-specific substances Ecologic features
Beta-hemolysis: complete lysis of RBCs; clear zone around colonies
Alpha-hemolysis: incomplete lysis of RBCs; green/brownish zone
Gamma-hemolysis: no hemolysis
Basis of serologic grouping: A-H, K-U Group specific carbohydrate determined by an
amino sugar:◦ Group A rhamnose-N-acetylglucosamine◦ Group B rhamnose polysacharide◦ Group C rhamnose-N-acetylgalactosamine◦ Group D glycerol teichoic acid containing D-alanine and glucose◦ Group F glucopyranosyl-N-
acetylgalactosamine◦ Group G◦ Non- groupable
Groupable Groups A, B, D – frequent Groups C,G, F – less frequent
Non-Groupable S. pneumoniae Viridans streptococci
Hemolytic reactions Hemolytic reactions Groups A and B Groups A and B
◦β Group D Group D
◦ α or or γ S. pneumoniaeS. pneumoniae and viridans and viridans
◦α
32
Name Lancefield Group
Hemolysis Other features
S . pyogenes A Beta Colonies >0.5 mmBacitracin susceptible;
PYR+
S. agalactiae B Beta CAMP +, Na hippurate +
Bacitracin-resistant
E. faecalis D Alpha, Gamma
(V)
Bile-esculin +; grow on 6.5% NaCl
S. bovis D Alpha, Gamma
(V)
Bile-esculin +; no growth in 6.5% agar
S. pneumoniae
NA Alpha Optochin Susceptible
S. viridans NA Alpha, Gamma
Optochin resistant
S. anginosus group (milleri group)
F (A,C,or G)
Beta, Alpha,Gamma
Small colonies (< 0.5 mm); Grp A
Bacitracin-resistant, PYR -
Peptostreptococcus
NA Alpha, Gamma
Obligate anaerobes
Org Habitat Mode of transmission
S pyogenes Skin, upper respi tract Direct contact, droplets
S agalactiae Female genital tract, lower GIT
Acquired by neonates in utero or during delivery
S pneumo Nasopharynx Contaminated secretions
Viridans strep Oral cavity Usually endogenous strains gaining access to normally sterile sites; dental manipulations
Enterococcus Soil, food, waterGIT, female GUT
Usually endogenous strains gaining access to normally sterile sites; nosocomia
Virulence factors Lipoteichoic acid
◦ fimbriae◦ binds to epithelial cells
Capsule ◦Hyaluronic acid
M protein ◦ antigenic◦ anti-phagocytic
Toxins and enzymes
37
fibronectinfibronectin
lipoteichoic acidlipoteichoic acidF-proteinF-protein
epithelial cellsepithelial cells
Toxins and enzymes
Suppurative◦ Wound Infections, with spread to tissues/bloodstream
Erysipelas Cellulitis Necrotizing fasciitis; “flesh-eating bacteria” Puerperal fever Bacteremia/sepsis
◦ Local infection Pharyngitis –most common infection due to S. pyogenes Pyoderma
◦ Invasive Streptococcal Toxic Shock Syndrome Scarlet Fever
Non-Suppurative or Poststreptococcal diseases
Post-streptococcal Glomerulonephritis 3 wks after skin infection; <0.5% incidence Majority recover completely
◦ AGN CGN Kidney failure Nephritogenic strains
◦ M type 12, 4 , 2, 49, 59-61 Antigen-antibody complexes Hematuria, proteinuria, edema,
hypertension Low complement levels
Rheumatic Fever most serious sequela of S. pyogenes;
important cause of valvular heart dse in the young
Preceded by infection 1-4 weeks earlier◦ Higher incidence with patients with severe
pharyngitis Cross reaction of M-protein with myosin Reactivated by recurrent strep infections
(GN does not) need for prophylaxis
Streptococcus Disease entity Tx
Group B – S. agalactiae
Neonates: meningitis, RDS, sepsis
Pen, ampi
Group D - Enterococci UTI, wound, biliary tract/abdominal, blood infections, endocarditis; Important nosocomial pathogen
Ampi, Pen, +aminoglycosides (synergistic)Intrinsically resistant to cephalosporins, penicillinase resistant pen (i.e. cloxacillin), monobactams
- S. bovis Endocarditis, bacteremia in the background of colon cancer
Pen, ampi
Viridans streptococcus
Endocarditis Pen
S. pneumoniae Pneumonia, endocarditis
Pen
Bacillus sp Clostridium sp
Square ends Long chains Central location of spores
Aerobic Saprophytic; soil, water, air,
vegetation; from carcasses of dead animals
Gray to white colonies B. anthracis: (-) hemolysis,
non- motile other bacilli: (+) hemolysis,
motile
B cereus
B anthracis
Virulence◦ Capsule
Determined by the capsule gene on the plasmid Poly-D-glutamic acid; Antiphagocytic
◦ Anthrax Toxin Toxin genes on plasmid Protective antigen (PA) – binds to receptors
facilitate entry of EF and LF Edema factor (EF)- adenylyl cyclase; together with
PA forms edema toxin Lethal factor (LF) – Together with PA forms lethal
toxin
Injured skin (Cutaneous anthrax; 95%)
Ingestion mucous membranes (Gastrointestinal anthrax; rare)
Inhalation (Pulmonary anthrax; 5%)
Sepsis can occur
Localized and systemic infection: endocarditis, meningitis, pneumonia, osteomyelitis
Eye infections: associated with trauma Device-related infections
Toxins – produced during sporulation or during log-phase growth
Emetic form◦ fried rice, pasta◦ Incubation of 1-5 hours◦ Nausea, vomiting, abdominal cramps,
occasionally diarrhrea◦ Self-limiting
Diarrheal type◦ meat dishes and sauces◦ Incubation of 1-24 hours◦ Profuse diarhea
≥ 105 per gram of food = diagnostic May be present in normal stool specimen
Spores◦ Wider than the bacilli◦ Central/subterminal or
terminal
Colony◦ Anaerobic conditions◦ C. pefringens : large, raised◦ C. tetani : small, raised
Soil, animal feces Wound infections C botulinum toxin
Toxin types A-GReleased during growth and during autolysis◦ Toxin type A and E – cleave SNAP 25◦ Toxin type B cleaves synptobrevinProteolysis of SNARE proteins in neurons inhibition
of acetylcholine release at the synapse paralysis
◦ Destroyed by heating x 20 mins, 100 deg C.
SNARE proteins
• Spiced/smoked/vacuum packed/ canned alkaline food eaten without cooking; honey
• Incubation: 18-24 hrs• Visual disturbances, swallowing dificulty, speech
difficulty, respiratory paralysis
• Dx: demonstration of toxin in the serum/leftover food. Radioimmunoassay Passive hemeagglutination
◦ Tx: supportive, ventilatory support : antitoxin (trivalent)
Infection – strictly localized Toxin Tetanus
◦ Incubation: 4-5 days, up to several weeks◦ Tetanospasmin
Binds to receptors on the presynaptic membranes of motor neurons migrate to spinal cord, brain via retrogarade axonal transport blocks release of glycine and GABA (inhibitory) hyperrefelexia, spasms
◦ Spasms of ms in the area of injury, trismus, lockjaw, respiratory compromise .... Death
◦ Dx: clinical; anaerobic culture◦ Tx: wound debridement, anti toxin, toxoid, antibiotic
(pen G/ Metronidazole)
Typically do not form spores when grown on laboratory media
Food Poisoning – meat dishes Enterotoxin – in some strains; producing
diarrhea; nausea/vomiting less frequent; self-limiting
Invasive◦ Toxins and enzymes: hemolytic and nectrotizing
effects Alpha toxin (lecithinase): Splits lecithin (component of cell wall)
into phosphorylcholine and diglyceride Theta toxin Dnase Hyaluronidase: digests collagen of subcutaneous tissue and
muscle
Contamination from soil/feces or from GIT Vegetative cells multiply, ferment CHO
+gas tissue distention+ compromised blood supply
+ toxins, enzymes Rapid spread; crepitation in the subcutaneous
tissue/muscle, foul smelling discharge, fever, shock... Death
Tx: early surgery, antibiotic Tx, antitoxins
In gas gangrene (clostridial myonecrosis)◦ Usually mixed infection: + g + cocci, g- bacilli
Spread of infection
Background of ◦ antibiotic therapy (commonly clindamycin,
ampicillin)◦ diarrhea (bloody or watery)◦ Fever, abdominal cramps, leukocytosis
Dx Detection of toxin/s
Toxin A (entrotoxin) Toxin B (cytotoxin)
Endoscopic findings od pseudomembranes Microabscesses in the bowelTx D/C antibiotic/s Oral Vancomycin or Metronidazole
Corynebacterium Propionibacterium Listeria Erysipelothrix Actinomycetes
Coryneforms: Short, slightly curved rods, rounded ends
Matachromatic granules – beaded appearance
Aerobic Small, granular, gray,
irregular borders on Blood agar
Enhanced growth on Loeffler medium
Pleomorphic morphology
4 biotypes: gravis, mitis, intermedius, belfanti
Respiratory tract, skin, wounds Can produce toxin Diphtheria Toxin
◦ Absorbed into the mucus membranes necrosis of epithelium and superficial inflammation pseudomembrane Fragment A : abrupt arrest of protein synthesis in the
epithelial cells Fragment B : required for the transport of fragment A
into the cell◦ Also produces paralysis
Sore throat Fever Dyspnea Difficulties with vision,
speech, swallowing, movement of limbs
Heart involvement Attempt to remove the
pseudomembrane bleeding
Dx◦ Modified Elek method
(WHO Diphtheria reference Unit)
◦ PCR◦ ELISA◦ Immunochromographic
strip Tx
◦ Antitoxin◦ Antibiotics
(Penicillin/erythromycin)
Elek method
Anaerobic corynebacteria P acnes is aerotolerant Part of normal flora of skin Common contaminant in blood culture
Produces lipases split free fatty acids off from skin lipids inflamacne
Occasionally, device related infections
Short rods, singles or in short chains
Facultative anaerobe +hemolytic motile Enhanced isolation if
tissue is kept at 4 deg C for a few days
Listeria monocytogenes motility test in semisolid medium showing the typical "umbrella" growth
Entry thru the GIT; ingestion of contaminated dairy products, meat, vegetables
Internalin (cell wall protein) interacts with E cadherin receptor on epithelial cells promotes phagocytosis into epithelial cells
Listeriolysin O Toxin - lyses membrane of phagolysosome org escapes into cytoplasm proliferate, cell actin proliferation induced by actA (a cell wall protein) propelled to form filopods
Filopods are ingested by adjacent cells organism is released new cycle
Iron
Perinatal◦ Early-onset (granulomatosis infantiseptica): result
of infection in utero; sepsis, pustular lesions and granulomas in multiple organs
◦ Late-onset: meningitis between birth and 3rd week Adult
◦ Bacteremia◦ Meningoencephalitis◦ Focal infections (rare)Non-specific clinical presentation
Dx◦ Culture of blood and CSF
Tx◦ Ampicillin◦ Erythromycin◦ Cotrimoxazole
Either ◦ short rods ◦ Small, smooth coloniesOR◦ long filaments◦ Large, rough colonies
May show alpha hemolysis
Direct inoculation 2-7 days incubation Pain and swelling at the site of
infection Resolve in 3-4 weeks
Tx: PenG
Actinomyces Nocardia Rhodococcus Streptomyces Actinomadura
Bacilli with tendency to form chains/filaments
Bcilli, coccobacillary, branching filaments
Cell wall contain mycolic acid- Partially acid-fast
Extensive branching, with aerial filaments; fragment after formation
Mostly, an opportunistic infection Sub acute to chronic pulmonary infection; may
disseminate to brain/skin Fever, weight loss, chest pain
Dx◦ Culture, biopsy
Tx◦ Cotrimoxazole
/amikacin/imipenem/minocycline/linezolid/cefotaxime
Mycetoma (‘Madura foot’)◦ Localized, slowly progressive chronic infection
that begins in the subcutaneous tissue◦ Destructive◦ Painless◦ May be fungal
Actinomycetoma◦ Nocardia asteroides, N brasiliensis/ Streptomyces
somaliensis / Actinomadura madura◦ Tx: Cotrimoxazole, streptomycin, dapsone
A israelii, A naeslundii, others Part of Normal oral flora Facultative anaerobes Heaped up “molar tooth” colonies Yellowish sulfur granules in infected tissue
Initiated by trauma Chronic, suppurative and granulomatous
infection that produces pyogenic lesions with interconnecting sinus tracts
Contains granules, containing microcolonies of orgs
Concomittant bacteria present Commonly affects
◦ Cervicofacial area◦ Thoracic◦ abdominal
Dx◦ Exam for the presence of sulfur granules
Tx◦ Penicillin/erythromycin