Gram positive and Gram Negative Flashcards by Shyralei Sumadsad

encapsulated, ferments maltose and glucose- Gram Negative cocci

Neisseria meningitidis

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insignificant capsule, ferments glucose only- Gram Negative cocci

Neisseria gonorrhoeae

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gram-negative “kidney-bean” diplococci

Neisseria gonorrhoeae

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aerobic, nonmotile
Fastidious, capnophilic–grows best at 35-37C

Neisseria gonorrhoeae

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Neisseria gonorrhoeae are oxidase positive in what medium

Thayer-Martin medium

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detects prolylaminopeptodase produced by gonoccoci

Gonochek test

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Habitat of Neisseria gonorrhoeae

human genital tract

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transmission of N. gonorrhoeae

sexual

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contactor during passage through birth canal

Neisseria gonorrhoeae

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N. Gonorrhoea- promote adherence and invasion into epithelial cells; expression results inopaquecolonies

Opa Proteins

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N. Gonorrhoea- complement deficiencies in the___________ predispose to illness

late-acting complement components (C6–C9)

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N. gonorrhoea usual co-infection with_______

Chlamydia trachomatis

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promote adherence to epithelial cells, antigenic variation, anti-phagocytosis (binds bacteria tightly to host cell protecting it from phagocytosis)

pili

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Pathogenicity of N. gonorrhoea

lipo-oligosaccharide (LOS)
IgA protease
pili
Outer membrane protein porins
Opa proteins
late-acting complement components (C6–C9)

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Localized spectrum of disease
-Ophthalmia Neonatorum
-Gonococcal Urethritis
-Pelvic Inflammatory Disease

Neisseria gonorrhoeae

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purulent conjunctivitis in newborns

Ophthalmia Neonatorum

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-urethritis and epididymitis in men
-most common cause of urethritis

Gonococcal Urethritis

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most common= cause of PID
complications:
Sterility
ectopic pregnancy
chronic pelvic pain
Dyspareunia
Fitz-Hugh-Curtis syndrome(perihepatitis):violin-string adhesions

Pelvic Inflammatory Disease

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Complications of Pelvic Inflammatory Disease

-Sterility
-ectopic pregnancy
-chronic pelvic pain
-Dyspareunia

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SPECTRUM OF DISEASE:DISSEMINATED-Neisseria gonorrhoeae

Septic Arthritis

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Neisseria gonorrhoeae- Gram stain of urethral specimens is accurate for

symptomatic males only

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Laboratory diagnosis where agar for Neisseria gonorrhoeae is?

enriched media (Chocolate blood agar)

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Selective medium of Neisseria gonorrhoeae

Thayer Martin medium (Chocolate blood agar + VCN)

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Colony morphology on modified Thayer-Martin (MTM) agar
-Small, beige-gray
-Translucent, smooth

Neisseria gonorrhoeae

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Fresh growth must be used for testing, because N. gonorrhoeae produces ______

autolytic enzymes

Treatment for N. gonorrhoeae

Ceftriaxone with azithromycin or doxycycline

Treatment for N. gonorrhoeae for neonate

prophylaxis with 1% silver nitrate

ophthalmia neonatorum treatment for N. gonorrhoeae

ceftriaxone

prevention of N. gonorrhoeae

use of condoms or spermicides with nonoxynol-9

Is there a vaccine for N. gonorrhoeae

none

gram-negative "kidney-bean" diplococci * large polysaccharide capsule oxidase-positive colonies on chocolate agar

NEISSERIA MENINGITIDES

Habitat of Neisseria meningitidis

URT

-transmission via respiratory droplets -humans are the only natural hosts -high carriage rate in close quarters

NEISSERIA MENINGITIDES

Pathogenicity of NEISSERIA MENINGITIDES

-antiphagocytic polysaccharide capsule -endotoxin (LPS) -IgA protease -late-acting complement components (C6–C9)

-most common cause among aged 2-18 yrs -fever, headache, stiff neck, and an increased level of PMNs in spinal fluid

Meningitis

dissemination of meningococci into the bloodstream omultiorgan disease, consumptive coagulopathy, petechial or purpuric rash (purpura fulminans)

Meningococcemia

most severe form of meningococcemia high fever, shock, widespread purpura, disseminated intravascular coagulation, thrombocytopenia, and adrenal insufficiency

Waterhouse-Friderichsen Syndrome

bilateral hemorrhagic destruction of the adrenal glands

Waterhouse-Friderichsen Syndrome

Spectrum of diseases NEISSERIA MENINGITIDES

-Waterhouse-Friderichsen Syndrome -Meningococcemia -Meningitis

purpuric rash

purpura fulminans

Treatment of N. Meningitidis

-penicillin G (no significant resistance) -rifampin chemoprophylaxis to close contacts

N. Meningitidis- vaccine contains capsular polysaccharide of strains _________

A, C, Y, and W-135

aerobic, non-spore-forming, non-motile gram-positive rods with club/coma shape rods arranged in V or L shape. Chinese characters

Coryebacterium diphtheriae

culture for Coryebacterium diphtheriae

Potassium tellurite: dark black colonies

metachromatic granules

Coryebacterium diphtheriae

for detection of toxigenicity of Coryebacterium diphtheriae

modified Elek test

Reddish metachromatic (Babes-Ernst / Volutin) granulescan be seen

Coryebacterium diphtheriae

Habitat of Coryebacterium diphtheriae

throat and transmission via respiratory droplets

PATHOGENESIS of Coryebacterium diphtheriae

-exotoxin -subunit A -subunit B -pseudomembranes

inhibits protein synthesis by adding ADP-ribose to elongation factor-2 (EF-2)

exotoxin

binds the toxin to cell surface o exotoxin encoded by b-prophage

subunit B

result from death of mucosal epithelial cells

pseudomembranes

Spectrum of disease of Coryebacterium diphtheriae

prominent thick, gray, pseudomembranes over tonsils and throat

-airway obstruction -Myocarditis - A-V conduction block, dysrhythmia -Neural involvement: peripheral nerve palsies, GBS, palatal -paralysis, neuropathies, cranial nerve and/or muscle paralysis

complications of pseudomembranes

Treatment of Coryebacterium diphtheriae

antitoxin and penicillin G

Prevention of Coryebacterium diphtheriae

toxoid vaccine, usually in combination with tetanus toxoid and pertussis vaccine (DTaP)

gram positive cocci in clusters catalase positive, coagulase positive

Staphylococcus aureus

gram positive cocci in clusters catalase positive, coagulase negative, novobiocin sensitive

Staphylococcus epidermidis

gram positive cocci in clusters catalase positive, coagulase negative, novobiocin resistant

Staphylococcus saprophyticus

Gram-positive cocci in grape-like clusters

Staphylococcus aureus

Staphylococcus aureus on blood agar

β-hemolytic, yellow or golden colonies

salt-tolerant on mannitol salts agar

Staphylococcus aureus

gold color of Staphylococcus aureus is due to the pigment

staphyloxanthin

habitat of S. aureus

human nose (anterior nares) and skin

Transmission of Staphylococcus aureus

-direct contact (hands) -fomites -contaminated food

Staphylococcus aureusVIRULENCE FACTORS: Immunomodulators

-Protein A -Coagulase -Hemolysins -PV Leukocidin -Catalase -Penicillinase

Staphylococcus aureus- VIRULENCE FACTORS: Tissue Penetrance

-Hyaluronidase -Fibrinolysin (staphylokinase) -Lipase

Staphylococcus aureus- VIRULENCE FACTORS: Toxins

-Exfoliatin -Enterotoxins (heat-stable): -Toxic shock syndrome toxin (TSST-1): -Alpha toxin

virulence factor that prevents complement activation

Protein A

virulence factor that builds an insoluble fibrin capsule

Coagulase

toxic to hematopoietic cells

Hemolysin

specific for white blood cells

PV Leukocidin

detoxifies hydrogen peroxide

Catalase

inactivates penicillin derivatives

Penicillinase

hydrolyzes hyaluronic acid

Hyaluronidase

dissolves fibrin clots

Fibrinolysin (staphylokinase)

spread in fat-containing areas of the body

Lipase

toxin that causes epidermal separation

Exfoliatin

toxins that are superantigens causing food poisoning

Enterotoxins (heat-stable)

toxins that are superantigen leading to toxic shock syndrome

Toxic shock syndrome toxin (TSST-1)

toxins that causes marked necrosis of the skin and hemolysis

Alpha toxin

Pyogenic diseases of S. Aureus

-SKIN and SOFT TISSUE INFECTIONS -ACUTE ENDOCARDITIS -PNEUMONIA -OSTEOMYELITIS and SEPTIC ARTHRITIS

toxigenic diseases of S. Aureus

-GASTROENTERITIS -SCALDED SKIN SYNDROME (Ritter Disease) -TOXIC SHOCK SYNDROME -

antimicrobials Factors that cause emergence of resistant pathogens

-Misuse -Over-prescription -Poor diagnostics

Why antimicrobial resistance has become a global concern

-Leads to death and disability -Hampers the control of infectious diseases -Increases the cost of healthcare -Jeopardizes healthcare gains to society

SKIN and SOFT TISSUE INFECTIONS bullous impetigo, folliculitis, furuncles, carbuncles, cellulitis, hidradenitis suppurativa, mastitis, surgical site infections

S. aureus

most common cause of acute endocarditis native valve (tricuspid valve) in IV drug abusers

S. aureus

PNEUMONIA nosocomial pneumonia, necrotizing pneumonia, complicated by empyema, abscess or pneumatocele post-viral pneumonia

S. aureus

OSTEOMYELITIS and SEPTIC ARTHRITIS

S. aureus

native valve (tricuspid valve) in IV drug abusers

ACUTE ENDOCARDITIS- S.aureus

what toxin cause gastroentritis by s. aureus

preformed heat-stable enterotoxin

cleaves desmoglein in desmosomes

exfoliatin

exfoliatin cleaves desmoglein in desmosomes. Scalded skin syndrome

Ritter desease- S. aureus

-fever, hypotension, strawberry tongue, desquamating rash and multi-organ involvement (>3) -usually no site of pyogenic inflammation; blood CS negative -usual scenario: tampon-using menstruating women or in patients with nasal packing for epistaxis

toxic shock syndome

morphology of staphylococcus epidermidis on blood agar

Whitish, non-hemolytic

habitat of S. epidermidis

normal skin flora

transmission of S. epidermidis

-autoinfection -direct contact (hands)

glycocalyx adheres well to foreign bodies and form ______

biofilms

most common cause of -prosthetic valve-associated endocarditis -septic arthritis in prosthetic joints -ventriculoperitoneal shunt infections

S. epidermidis

treatment of S. epidermidis

-removal of prosthetic device -over 50% are methicillin-resistant and thus require vancomycin

2nd most common cause of UTIs in sexually active women

Staphylococcus saprophyticus

treatment of Staphylococcus saprophyticus

TMP-SMX and quinolones

catalase negative, alpha hemolytic, bile-optochin-sensitive

Streptococcus pneumoniae

catalase negative, alpha hemolytic, bile-optochin-resistant

viridans streptococci

catalase negative, beta hemolytic, bacitracin sensitive

Streptococcus pyogenes

catalase negative, beta hemolytic, bacitracin resistant

Streptococcus agalactiae

catalase negative, gamma hemolytic

group D streptococci

Lancefield group A positive PYR test

Streptococcus pyogenes

habitat of Streptococcus pyogenes

human throat (oropharynx) and skin

transmission of S. pyogenes

respiratory droplets

Virulence enzymes of S. pyogenes

Hyaluronidase Streptokinase DNase C5A peptidase

toxins of S. pyogenes

Erythrogenic toxin Streptolysin O Streptolysin S Pyogenic exotoxin A Exotoxin B

Streptococcus pyogenes: Evidences of Infection

anti-streptolysin O (ASO) anti-DNAse B anti-streptokinase

SKIN and SOFT TISSUE INFECTIONS of S. pyogenes

impetigo contagiosa, Erysipelas, Cellulitis and Necrotizing fasciitis

perioral blistered lesions with honey-colored crust

impetigo contagiosa

what toxin facilitates Necrotizing fasciitis

Exotoxin B

superficial infection extending into dermal lymphatics

Erysipelas

what enzymes help cellulitis by S. pyogenes

hyaluronidase (spreading factor)

deeper infection involving subcutaneous/dermal tissues

Cellulitis

rapidly progressive infection of deep subcutaneous tissues

Necrotizing fasciitis

most common bacterial cause of sore throat

Streptococcus pyogenes

PHARYNGITIS pyogenic complications of S. pyogenes

peritonsillar and retropharyngeal (quincy)

what toxin facilitates scarlet fever

erythrogenic toxin

fever, strawberry tongue, centrifugal rash (sandpaper-like), Pastia’s lines, desquamation

scarlet fever

-clinically similar but milder than S. aureus TSS due to pyogenic exotoxin A -blood cultures are often positive

streptococcal toxic shock syndrome

-postpharyngitic -cross-reacting antibodies to M proteins and antigens of joint, heart, and brain tissue -caused by pyogenic

ACUTE RHEUMATIC FEVER

-post-impetigo OR postpharyngitic -M protein incites immune complex deposition on the glomerular basement membrane -hematuria

GLOMERULONEPHRITIS

DOC of S. pyogenes

Penicillin G

-Lancefield group B -hydrolyze hippurate -CAMP test–positive -grow using Lim broth

Streptococcus agalactiae

habitat of Streptococcus agalactiae

Vagina

neonatal pneumonia, sepsis and meningitis most common cause

Streptococcus agalactiae

Gram positive and Gram Negative Flashcards

(131 cards)