Bacterial Diseases

Vocabulary flashcards covering key bacteria, virulence factors, diagnostics, and treatments from the notes.

Gram Pos Cocci

staph aureus

staph epidermidis

strep pyogenes

Gram Pos Rods

cutibacterium acnes

bacillus anthracis

clostridium perfringens

Gram Neg Cocci

neisseria gonorrhoeae

Gram Neg Rods

eikenella corrodens

pasturella multocida

bartonella henslae

pseudomonas aeruginosa

vibro vulnificus

Reportable infections

anthrax

gonorrhea

lyme disease

spotted fever rickettsiosis

vibriosis

vancymycin intermediate/resistant staph aureus

Staphylococcus aureus biochemical properties

catalase positive

coagulase positive

ferments mannitol

Staphylococcus aureus reservoir

human only (nasopharynx and skin)

Staphylococcus aureus risk factors

hospitalization and healthcare settings

skin and soft tissue injury

Staphylococcus aureus skin infections

folliculitis

carbuncles and furuncles

cellulitis

scaled skin syndrome (infants)

impetigo

abscesses

Staphylococcus aureus MSK infections

top cause of septic arthritis

top cause of osteomyelitis

Staphylococcus aureus virulence factors

protein A

hemolysins, coagulase, catalase

pantone-valentine leucocidin

exfoliative toxin

MecA

mecA

alternative PBP that is resistant to beta-lactams

Beta Lactams

target PBPs that link proteins in cell wall

Exfoliative toxin

loss of cell to cell contact in skin epithelia

seen in scaled skin syndrome and impetigo

Panton-Valentine leukocidin (PVL)

causes leukocyte destruction and tissue necrosis

seen in CA-MRSA

Protein A

binds the Fc region of antibodies, preventing complement activation

Coagulase

converts fibrinogen to fibrin, encasing the bacteria in a clot to hide from the immune system

CA-MRSA

young, healthy, crowded setting, sports, skin trauma

HA-MRSA

hospital exposure, invasive devices, recent antibiotics

MSSA Treatment

cephalexin, cefazolin, nafcillin

MRSA Treatment

vancomycin

linezolid

Vancomycin MoA

binds peptidoglycan peptides and prevents synthesis

Linezolid MoA

binds ribosomes and stops protein synthesis

Staphylococcus epidermidis biochemical properties

catalase positive

coagulase-negative

mannitol fermentation negative

Staphylococcus epidermidis transmission

human only

endogenous spread

Staphylococcus epidermidis risk factors

foreign material or bodies (prosthetics, catheters)

Staphylococcus epidermidis infections

prosthetic joint or bone infections (artificial joints, orthopedic implants)

catheter infections

Staphylococcus epidermidis virulence factors

slime layer/glycocalyx formation

biofilms

Staphylococcus epidermidis treatment

cephalexin, cefazolin, nafcillin

Streptococcus pyogenes biochemical properties

Group A Streptococcus (lancet group A surface antigens)

beta-hemolytic

catalase negative

bacitracin sensitive

Streptococcus pyogenes transmission

respiratory droplets (pharyngitis)

direct contact (impetigo)

endogenous spread

Impetigo risk factors

contact with sores

Necrotizing fasciitis risk factors

diabetes, kidney disease, cirrhosis, cancer

Cellulitis risk factors

IV drug use, chronic skin conditions

Streptococcus pyogenes suppurative infections

scarlet fever

impetigo

erysipelas

cellulitis

necrotizing fasciitis

Streptococcus pyogenes suppurative infections

seen in patients not receiving antibiotic therapy

Scarlet Fever

strawberry tongue, sandpaper like rash, skin peeling, sore throat

Impetigo

honey colored crusted skin lesions

Toxic Shock Syndrome

Streptococcus pyogenes

fever, rash, skin peeling AFTER rash

Streptococcus pyogenes virulence factors

hyaluronic acid capsule

M protein

streptolysin O

pyogenic ectotoxin

Erysipelas

well defined skin rash

usually face or legs

bright red

Cellulitis

poorly defined borders, diffuse spread

Necrotizing Fasciitis

rapidly spreading

soft tissue infection with severe pain

Hyaluronic Acid Capsule

inhibits phagocytosis

M protein

inhibits complement activation

Streptolysin O

punches holes in membranes of RBCs and WBCs

Pyogenic exotoxin

superantigen

can cause scarlet fever or toxic shock

Streptococcus pyogenes treatment

most: amoxicillin

necrotizing fasciitis and toxic shock: penicillin G and clindamycin, possible debridement

Cutibacterium acnes characteristics

Gram-positive rod

anaerobic

no spores

Cutibacterium acnes reservoir

commensal in low levels on the skin

endogenous infection (sebum in follicles)

Cutibacterium acnes infections

ance vulgaris

surgical wounds

implant associated

Acne vulgaris

secretes digestive enzymes causing cellular damage, metabolic byproducts, and bacterial debris

triggers blackheads, whiteheads, pimples, oily skin, and scarring

Cutibacterium acnes surgical infections

abscesses, sinus tracts, osteomyelitis

in areas with many sebaceous glands

more common if prosthetic is involved

Cutibacterium acnes treatment

benzoyl peroxide

salicylic acid

retinoids

antibiotics

Bacillus anthracis characteristics

Gram-positive rod

spore-former

non-motile

non-hemolytic

unique capsule

Bacillus anthracis capsule

poly-d-gamma-glutamic acid

Bacillus anthracis reservoir

spores in environment

Bacillus anthracis cutaneous transmission

spore inoculated directly into skin and germinate

Bacillus anthracis epidemiology

zoonotic (herbivores)

Cutaneous Anthrax

painless black eschar only at inoculation site

massive edema

necrotic ulceration

Bacillus anthracis virulence factors

spores

protective antigen

lethal toxin (AB)

edema toxin (AB)

capsule

Anthrax Diagnosis

cutaneous dx based on clinical symptoms

culture and gram stain

PCR

Bacillus anthracis treatment

ciprofloxacin

doxycycline

Clostridium perfringens characteristics

Gram-positive rod

obligate anaerobe

forms spores

Clostridium perfringens transmission

spores enter wound or surgical site

Gas Gangrene Symptoms

bad vitals

crepitus

purple bullae

necrotic destruction of muscle

fast progression

Gas Gangrene Toxins

alpha toxin

beta toxin

hyaluronidase and collagenase

Clostridium perfringens diagnosis

double hemolysis

egg yolk agar

Clostridium perfringens prevention

clean wounds thoroughly

antibiotics before, during, and after abdominal surgery

Clostridium perfringens treatment

immediate: high dose penicillin, beta lactams, clindamycin

may need surgery or hyperbaric oxygen therapy

Neisseria gonorrhoeae characteristics

Gram-negative diplococci

oxidase positive

glucose fermenter

Neisseria gonorrhoeae transmission

human only

sexual contact or secretions

perinatal

Neisseria gonorrhoeae epidemiology

second most common STI

Disseminated Gonorrheal Infection

septic arthritis of joint (usually knee)

Neisseria gonorrhoeae virulence factors

pili for adherence and antigenic variation

Neisseria gonorrhoeae diagnosis

grows on chocolate agar and thayer martin agar

Neisseria gonorrhoeae treatment

ceftriaxone

HACEK group

fastidious, slow growing, gram neg organisms in the oral-pharyngeal flora

associated with poor dentition, periodontal disease, or oral trauma

Eikenella corrodens

Gram-negative short coccobacillus; non-motile; oxidase positive; part of HACEK group; associated with bites and dental infections; smell of bleach on culture.

Pasturella multocida

Gram-negative coccobacillus; zoonotic from cats and dogs; bite wounds; rapid-onset cellulitis; treated with beta-lactam plus beta-lactamase inhibitor.

Bartonella henselae

Gram-negative rod; cat-scratch fever; bacillary angiomatosis in immunocompromised; silver staining (Warthin-Starry); treated with macrolides or doxycycline.

Pseudomonas aeruginosa

Gram-negative rod; oxidase positive; non-fermenter; thrives in moist environments; exotoxin A; biofilm; multiple antibiotic resistances; green pigment.

Vibrio vulnificus

Gram-negative curved rod; halophilic; wound infections from seawater or seafood; TCBS agar shows yellow for sucrose fermentation; treat with doxycycline ± ceftriaxone.

Borrelia burgdorferi

Spirochete transmitted by Ixodes ticks; causes Lyme disease; erythema migrans; diagnosed by two-tier testing; treated with doxycycline.

Rickettsia rickettsii

Obligate intracellular bacterium; causes Rocky Mountain spotted fever; tick-borne; endothelial cell infection leading to vasculitis; treated empirically with doxycycline.

OspA

Outer surface protein A of Borrelia; facilitates transmission by helping bacteria attach to tick gut.

Thayer-Martin agar

Selective culture medium for Neisseria gonorrhoeae; contains antibiotics to suppress normal flora.

TCBS agar

Thiosulfate citrate bile salts sucrose agar used to culture Vibrio species; Vibrio vulnificus ferments sucrose yielding yellow colonies.

HACEK group

Fastidious Gram-negative bacteria from oral flora associated with culture-negative endocarditis; includes Haemophilus spp, Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella kingae.

Erythrogenic toxin

Pyrogenic exotoxin produced by GAS; superantigen; causes scarlet fever and toxic shock syndrome.

M protein

GAS surface protein that inhibits phagocytosis and protects against complement-mediated killing.

Streptococcus pyogenes virulence factors

M protein, streptolysins, hyaluronic acid capsule; factors that inhibit phagocytosis and promote tissue damage.

Erythema migrans

Bull's-eye rash that is an early sign of Lyme disease.

GAS treatment (general)

Penicillin G with clindamycin for necrotizing fasciitis or toxin-mediated disease; amoxicillin for non-NF infections.