Gram-Positive Bacteria: Staph

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Gram-Positive Bacteria

Staph

• Non-motile and non-spore-forming
• Catalase-positive
• Facultative aerobe/anaerobe
• Mesophilic, thrives in high salt concentrations
• Forms irregular clusters

S. aureus

• Causes pyogenic infections such as abscesses, furuncles/carbuncles, and bullous impetigo
• Produces toxins leading to toxemia, including SSS, TSST-1, and food poisoning (SEA/SEB toxin)
• Identifiable in the lab by its golden appearance on agar, ability to ferment mannitol, beta-hemolysis, and coagulase-positive reaction
• Protein, FnBP, hemolysin/leukocidin, hyaluronidase, and staphylokinase contribute to its virulence
• Methicillin is used to treat penicillin-resistant strains (PRSA) because it is not destroyed by B-lactamase
• MRSA strains have the mec A gene of S. aureus that codes for PBP2a, treat with vancomycin
• VRSA treat with linezolid

S. epidermidis

• Associated with prosthetic infections
• Capsule/slime layer (biofilm) contribute to virulence, novobiocin-positive and produces gamma-hemolysis
• MSSE treated with nafcillin
• MRSE treated with vancomycin and rifampin

S. saprophyticus

• Causes UTIs, particularly honeymoon cystitis
• Normal flora in the GI tract, vagina, and perineum
• Biofilm formation and urease production (increasing pH) contribute to its virulence, novobiocin-negative and produces gamma-hemolysis
• Treat with TMP-SMX (blocks folic acid bacteria growth)

Strep

• Non-motile and non-spore-forming
• Catalase-negative
• Facultative anaerobe
• Short or long chains
• Pyrogenic exotoxin (SpeA/SpeB) leads to hemolysis
• Can be classified into Brown groupings (a, B, y hemolysis) and Lancefield groups (A, B, D) based on the carb cell wall

S. pyogene (GAS, B-hemolysis)

• Virulence factors: hyaluronic acid capsule, M protein, streptolysin O and S
• Invasive due to streptokinase (dissolves blood clots), streptodornase (DNase), C5a peptidase, protein F, and hyaluronidase production
• Causes suppurative infections: pharyngitis and soft tissue infections
• Can lead to autoimmune diseases: rheumatic fever and glomerulonephritis (hematuria, proteinuria)
• Causes scarlet fever, impetigo (S. pyoderma), erysipelas, necrotizing fasciitis, and puerperal fever
• Lab identification: bacitracin sensitive, PYR positive, and ASO titer

S. agalactiae (GBS, B-hemolysis)

• Causes neonatal meningitis, pneumonia, and bacteremia; treat with intrapartum penicillin
• Lab identification: bacitracin resistant, CAMP positive (arrowhead), and hippurate positive

S. bovis + enterococcus faecalis (GDS, Y-hemolysis)

• S. bovis is associated with colorectal cancer
• Lab identification: gram stain, 6.5% salt inherently vancomycin resistant

S. pneumoniae (no group, a-hemolysis)

• Antigenic capsule, pneumolysin production (attacks lung tissue, degrades hemoglobin), and IgA protease contribute to virulence
• Treat with MOPS/OPSI, antibiotics, and prevention with vaccine (prevnar/pneumovax)
• Lab identification: green around colony, optochin sensitive, quellung reaction (capsular swelling test, omnisera)

Viridans Strep (no group, a-hemolysis)

• S. Mutans (serotypes c, e, f) is associated with caries
• Survive in acid by glycolysis, repair enzymes, and produce long fatty acid chains (unsaturated)
• Adhesin Agl and Agll, along with glucan binding protein, contribute to adherence
• S. Sanguinis causes subacute bacterial endocarditis

Bacillus

• Aerobic and spore-forming

B. anthracis

• Causes anthrax (woolsorter's disease)
• Capsule made of poly-D-glutamic acid → establish infection
• Edema/lethal toxins cleave protective antigen w/ furin
• Lethal factor cleaves MAPKK while edema factor increases cAMP
• Virulence factors: pX01 toxin plasmid and pX02 capsule plasmid
• Ames/sterne strain used for vax
• Lab identification: non-motile, non-hemolytic, and fast growth

B. cereus

• Produces heat-stable enterotoxin, cereolysin (degrades RBCs), and PLC (lecithinase)
• Causes food poisoning/gastroenteritis: emetic (heat-stable) from rice and diarrheal (heat-labile) from meat/veggies
• Treat with antibiotics, but NOT penicillin/cephalosporin (B-lactamase)
• Lab identification: motile, hemolytic, uses citrate

Clostridium

• Found in soil, water, and sewage
• Anaerobic and spore-forming
• Lab identification: enzymatic digestion on egg yolk agar plate

C. tetani

• Virulence factors: tetanospasmin (HL neurotoxin, blocks glycine → spasms) and tetanolysin (HS hemolysin)
• Symptoms of tetanus: lockjaw, fixed smile, seizure, auditory hyperacuity, and neck/jaw pain

C. botulinum

• Found in soil and canned food
• Produces nerve toxin
• Blurred vision, difficulty swallowing, and flaccid paralysis
• Virulence factor: type A, B, E (HL neurotoxin) that blocks Ach @ NMJ; botox is type A

C. perfringens

• Causes gas gangrene/myonecrosis: tissue damage (blood flow stops), fermenting muscle, and putrefying proteins
• Virulence factors: exotoxins like protease, lipase, and collagenase
• Treatment: amputation/hyperbaric oxygen chamber, antibiotics not recommended

C. difficile

• Causes PC (pseudomembranous colitis)
• Consequence of eliminating normal intestinal flora due to antibiotic therapy, abdominal pain, and watery diarrhea
• Virulence factors: exotoxin A (enterotoxin) and B (cytotoxin)
• Lab identification: exotoxin A (immunoassay) and B (cytotoxicity assay)

Corynebacterium

• Aerobic/non-spore-forming and non-acid-fast
• Non-motile and associated with whooping cough

C. diptheriae

• V and Y configuration, club shaped rods, mycolic acid
• DtxR (diphtheria toxin repressor gene, active in high iron)
• Virulence factors:
  • dipthin (IgA protease)
  • Diphtheria toxin:
    • A subunit: catalytic domain (disrupts protein synthesis → cell death)
    • B subunit: receptor binding
    • T subunit: translocation
• Causes diphtheria: muscle weakness, sore throat, low fever, pseudomembrane on tonsils/pharynx
• Lab identification: elek test, jet black colonies on media, metachromatic granules at terminal ends (salt deposition)

Listeria

• Facultative aerobic/non-spore-forming
• Found in water, deli meat, and produce
• Motile at room temperature but not at 37°C, can grow at 4°C

L. monocytogenes

• Attaches to macrophages, replicates in cytoplasm → actin tail
• Produces exotoxin: hemolysin + Zn++ dependent protease
• Causes sepsis and meningitis (stiff neck, headache, coma in adults)

Actinomyces

• Anaerobic
• Gram-positive branching filamentous bacteria
• Found in the oral cavity
• Penicillin is the treatment

Actinomycosis

• Cervicofacial infections (poor OH, dental procedure, oral trauma)
  • Swelling or hard red/purple lump on face/upper neck, draining sores, minimal to no pain
  • Pyogenic (suppurative) and granulomatous
• Treatment involves surgical removal of tissue, prophylactic measures, and good oral hygiene
• Lab ID: molar tooth appearance on agar, presence of sulfur granules

A. viscosus

• Provide succinate growth factor to promote adhesion of P. gingivalis to plaque

Nocardia

• Aerobic
• Gram-positive non-branching filamentous bacteria
• Found in the environment
• Sulfonamide is the treatment
• Can cause mycetoma and nocardiosis (pulmonary infection)

CMN Group

• Contains mycolic acids (Corynebacterium, Mycobacterium, Nocardia)

Mycobacterium

• Aerobic, slow growth
• Lab ID: acid fast, Ziehl-Neelsen stain targets mycolic acid killed by pasteurization

M. avium complex: MOTT/NTM

• M. avium, M. intracellulare, and M. chimaera
• Infection leads to lymphadenitis (young kids) and Lady Windermere syndrome (from cough suppression)
• NOT contagious

M. tuberculosis complex

• M. tuberculosis
  • Non-motile, non-spore-forming, grows on LJ medium (brown granular colonies)
  • Syndemic with HIV, T-lymphocytes depleted in HIV are needed for immune control of Tb
  • Immune activation by Tb enhances HIV replication through NF-kB
  • Virulence: LAM/PIM prevents phagosome maturation
  • Activation of macrophages by T cells producing IFNy, then TNF production which causes weight loss
  • Treatment: DOT therapy, RIPE; treat latent Tb with INH
    • RIF inhibits RNA synthesis, INH/EMB inhibits cell wall synthesis and PZA destroys plasma membrane
  • Diagnosis: PPD test (+ could be latent) / TST skin tests, chest x-ray (Ghon complex), IGRA (can distinguish BCG immunity from Tb infection)
    • Ghon focus shows lesion in lung
    • Primary Tb at base of lung, secondary reactivated Tb at apex of lung, miliary Tb (anoxia)

M. leprae

• Causes leprosy with skin lesions/nerve damage; infectious but curable
• Reservoir: nine-banded armadillo
• Paucibacillary (5 or less lesions) or multibacillary (6 or more symmetrical lesions, leonine facies)
• Tuberculoid vs lepromatous leprosy, Th1 (mild) vs Th2 (severe, high infectivity)

M. bovis

• From cattle
• Use vax (BCG, Bacille of Calmette Guerin)

Lactobacillus

• Not mycobacterium
• G+, produce lactate/acetate
• Involved in the progression of caries (root)

Gram negative

Veillonella parvula

• Consumes lactic acid but helps strep grow (caries)
• Asaccharolytic (does not metabolize sugars)

Enterobacteriaceae

• Catalase+, oxidase-, ECA (antigen), facultative
• Lactose fermenting:

E. Coli

• Virulence factors: pili, enterotoxin, siderophores, capsule
  • Leads to UTI (uropathogenic- use P fimbriae to reach kidney), neonatal meningitis (MNEC– virulence factor K1 in capsule) and gastroenteritis (ETEC and EHEC/shiga)
• ETEC: watery diarrhea, colonization factor I and II, small intestine
• EHEC / shiga: bloody diarrhea, O157: H7 strain, large intestine, reservoir in cattle
  • Hemolytic uremic syndrome (HUS): damage of glomerular cells, acute renal failure, mostly in children
  • Doesn’t ferment sorbitol; treat with fluid/salt replacement

Klebsiella pneumoniae

• Primary or secondary infection in people with impaired pulmonary
• Carbapenem resistant (NDM-1, B-lactamase)

Enterobacter

• Yersinia pestis = plague
  • Bubonic (zoonosis, fleas/rodents), pneumonic (aerosol spread, high mortality), septicemic (progressed form of disease, high mortality)
  • Capsule, V antigen (T3SS), F1
  • Treat with oral (tetracycline) or IV antibiotics, vax

Non-lactose Fermenting

• Shigellosis: nonmotile, non-H2S
• S. sonella and S. dysenteriae produce shiga toxin, invade M cells
  • Stain for PMN leukocytes.

Salmonella

• Motile, H2S
• Kaufman-White scheme (Vi antigen = capsule)
• S. typhi (typhoid fever): replicates in Peyer's patches and intestinal cells; rose spots, enteric fever
• S. enteritidis/typhimurium (food poisoning): needs a large dose for infection because it is acid labile

Proteus mirabilis

• Antibiotic resistant, swarmer leading to renal stones
• MacConkey Medium
  • Selective: to halt gram+ w/ bile salts, crystal violet
  • Diff: neutral red turns pink in acid means lactose fermenting
• Oxidase Test: Identify bacteria that produce cyt c (blue/purple color)
• IMViC: indole, methyl red, VP, citrate (differentiate coliforms)
• Agglutination: Detect O (LPS), K (capsule), H (flagella) antigens

P. gingivalis

• Strict anaerobes, non-motile rods
• Asacchrolytic
• Pleiomorphic rods
• Gingipains (activate MMPs, cleave Arg-X and Lys-X)
  • Black colonies on BAP, vit K and hemin need to be added

T. forsythia

• No pigment, spindle shape

Prevotella

• ANUG (punched out, crater-like lesion at interdental papillae, painful ulcer), also associated w/ T. denticola + fusobacterium
• Saccharolytic
• P. intermedia (pregnancy-associated gingivitis)

T. denticola

• Strict anaerobe, motile spirochete
• Proteolytic
• Periplasmic flagella (btwn outer sheath and cell cylinder) for motility
• Virulence: MSP, Dentisilin, leucine-rich peptide for adherence, LOS (bone resorption, inflammation)

Aggregatibacter actinomycetemcomitans (Aa)

• Facultative anaerobe, non-motile
• Capnophilic (like CO2)
• Rapid progressive form of perio disease
• Leukotoxin (Ltx) and cytolethal distending toxin (Cdt) – DNase, block cell division cause apoptosis

Vibrio

V. cholerae

• Curved rods, facultative anaerobe, motile
• Watery diarrhea
• AB5 tox (dehydration, electrolyte imbalance); tcp (avirulent, resist flushing, adherence)

V. parahaemolyticus

• Seafood-associated enteritis
• Kanagawa hemolysin

V. vulnificus

• Sea water
• Watery diarrhea/septicemia (antibiotics essential)

Campylobacter

• Microaerophilic, motile
• S-shaped, flagella, LOS antigen
• Poultry

C. jejuni

• Acute → gastroenteritis, treat with fluid/electrolyte
• Chronic → reiter syndrome, reactive polyarthritis, and Guillain-Barre syndrome, neuromuscular paralysis (demyelinating)
• Achlorhydria: lack of acid in stomach, makes you more susceptible

C. fetus

• S-layer protein: capsule-like, inhibit C3b binding
  • Gull-wing on gram stain, darting motility in fresh stool
  • Treat with IV antibiotics

Helicobacter

• Motile, microaerophilic

H. pylori

• Duodenal ulcers and stomach cancer (gastric MALT B-cell lymphoma), adenocarcinoma, gastritis
• Mucus and gastric adaptation (urease)
• Cag PAI: CagA protein injected T4SS, inflammation/cell damage
• VacA: produce vacuoles to affect mitochondria, apoptosis
  • Urease breath test, PCR
  • Treat with 2 different antibiotics at once to prevent resistance
  • Treat gastritis: proton pump inhibitor, macrolide, B-lactam

Haemophilus

H. influenzae

• Pleomorphic coccobacillus
• A-f capsule type, type b (Hib) most virulent
  • Hib cause meningitis, epiglottitis, bacteremia
• Nontypeable (NTHi) means no capsule, cannot use Hib vaccine
• Cause otitis media, sinusitis, tracheobronchitis, pneumonia
• X (hemin) factor and V (nicotinamide-adenine-dinucleotide) factor, released after lysis of RBCs

H. aegyptius

• Pink eye (acute purulent conjunctivitis, contagious)

H. ducreyi

• Chancroid (STD, males) ulcerated lesions, inguinal lymphadenopathy
• Culture CSF, blood, or pus on chocolate agar, or use X/V factor to detect growth around S. aureus

Bordetella

B. pertussis

• Whooping cough (most deaths in infants)
• Virulence:
  • FHA (bind to RBCs)
  • PTx (a subunit inactivates adenylate cyclase)
  • Adenylate cyclase toxin (AC): inhibit chemotaxis, phagocytosis.
  • Tracheal cytotoxin (TCT): ciliostasis, induce IL-1 fever
  • Catarrhal → paroxysmal → convalescent stage
  • Treat with acellular vaccines: DTaP (kids, high dose) or Tdap (teens/adults, low dose)
  • NAD + antibiotics in charcoal culture

B. parapertussis

• Mild form of B. pertussis

B. bronchiseptica

• Cause bronchopneumonia
• Nasal swab, NAAT, direct fluorescent antibody

Neisseria

• Pyogenic diplococci, LOS antigen
• Virulence: porins, OPA (binding), Rmp/OMP3 (block bactericidal killing), IgA protease

N. gonorrhoeae

• PorB
  • Treat with penicillin initially, intramuscular ceftriaxone, eye ointment for baby (no vax)

N. meningitidis

• Capsule
• PorA and PorB
• Fulminant meningococcal sepsis (FMS): cause DIC and shock
• URI/sore throat, sensitive to light, purpura, petechiae
  • Quadrivalent vaccine against serogroup A, C, W-135, Y
• MenB
• Gram stain urethral, cervical discharge, NAAT

Pseudomonas

P. aeruginosa

• Produce pyocyanin/pyoverdin (fruity odor), non-lactose (MacConkey), B-hemolysis, oxide
• Diseases: PSEUDOMNA (pneumonia, sepsis, ecthyma, UTI, dermatitis, osteomyelitis, malignant otitis externa, nosocomial, alimentary tract)
• Virulence: flagella, pili (adhesion), endotoxin, exotoxin A (inactivate EF-2), rhamnolipids (surfactant), alginate (biofilm)
• Invasion thru T2SS/T3SS
• Quorum sensing (enhance gene expression)
• Intraspecies communication: AHL – acyl homoserine Lactone, G-
• Interspecies communication: Al-2, G+/-
• Cetrimide agar + MgCl + KS (stimulate pigment)

Mycoplasma

• Smallest living organism, no cell wall, membrane has cholesterol
• Fried egg colony, needs sterol/lipid for growth

M. pneumoniae

• Atypical, walking pneumonia
  • Can produce auto-antibodies (IgM) against RBC, brain/lung/liver cell → hemolytic anemia
  • No penicillin/cephalosporin because no cell wall
  • Virulence: hydrogen peroxide, Ciliostasis., P1 adhesion protein

M. hominis

• Transmitted vertically or sexual contact (found in genital tract and oral cavity)
• Cause pelvic inflammatory disease, postpartum fever, spontaneous abortion, chorioamnionitis

M. genitalium

• Urethritis in men, cervicitis women
• ~20% of NGU cases

Ureaplasma

• T-strains (tiny small colonies)

U. urealyticum

• Cause NGU, produce urease; treat with azithromycin.

Legionella

L. pneumophilia

• Pneumophilia (mostly found in the lung)
• Infection by binding to receptors on phagocytes
• Risk factors: smoking, elderly, airborne transmission
• Legionellosis: pontiac fever (mild flu-like), legionnaire's disease (severe pneumonia)
  • dieterle stain, BYCE agar (charcoal), sputum DFA stain, antigen in urine

Rickettsia

• Transmitted by arthropod, binary fission, obligate intracellular, exchange ADP for ATP, weak LPS
• Degrade phagosome with PLA after endocytosis

R. rickettsii

• Rocky Mountain spotted fever (rash, headache, DIC), reservoir and vector thru tick (NO person to person)

R. prowazekii

• Louse borne epidemic typhus; rash on trunk → periphery, delirium/coma (meningoencephalitis), human body louse, person to person, brill-zinsser disease (recurrent form of epidemic typhus)
• By clinical symptoms, hazardous in culture

Erlichia

Erlichia chaffeensis

• Human monocytic ehrlichiosis (fever, NO rash) – infects mononuclear leukocytes, primary tick vector; amblyomma americanum, mulberry inclusion body)

Coxiella

C. burnetti

• Q fever (treat with doxycycline), can be due to combo pneumonia/hepatitis -rash is rare, Aerosol transmission, Remains in phagolysosome (produce acid phosphate for survival)

Chlamydia

• No ATP, cell wall, tropism
• Infectious elementary body (EB) to reproduce reticulate body (RB)
• Lab ID: McCoy mouse fibroblasts, ELISA, FA test (show blood vessel of eye)

C. trachomatis

• Iodine stain, treat sulfonamide
• A-C serotype for trachoma (blindness, chronic conjunctivitis)
• D-K serotype for bacterial STD (NGU, PID, urethritis, cervicitis)
• L1-L3 serotype for LGV (lymphogranuloma venereum-inguinal adenitis, regional lymph nodes enlarge)

C. psittaci

• Inhalation of dust (bird feces), lower respiratory tract

Spirochetes

• Anaerobic, fastidious, slow growth

T. pallidum

• Darkfield microscopy, pointed straight ends
• Virulence: OMP (binding), hyaluronidase, corkscrew motility
• Primary syphilis: hard chancre, intimate contact, no pus/pain, infectious
• Secondary syphilis: flu-like, diffuse rash, condylomata lata, oral lesions, infectious
• Tertiary syphilis: gumma on hard palate, NOT infectious
• Congenital syphilis: hutchinson's triad (peg teeth/mulberry molar, deaf, blind)
• Treat with penicillin (but can cause Jarisch-Herxheimer reaction, flu-like).
• Non-specific- non-treponemal: VDRL/RPR test
• Specific- treponemal: FTA-ABS/TP-PA test (anti T. pallidum antibodies)

Borrelia burgdorferi

• Lyme disease; transmission from bite of immature tick (nymph)
• Primary Lyme: erythema migrans (bull's-eye rash)
• Secondary Lyme: cardiac abnormal, Bell's palsy, joint/muscle pain
• Tertiary Lyme: encephalopathy, arthritis (occurs months later)
• Treat with amoxicillin, doxycycline, and cefuroxime
• ELISA + western blot, giemsa stain

Leptosira interrogans

• Hooked ends
• Leptospirosis, weil's disease: renal/hepatic failure

Oral treponemes

• Mostly in animals
• T. denticola(perio)
• T. socranskii