mb w 5 (bact infect + pathogenic cocci)

(recap)

gram-pos > purple

• usually aerobic (need O2)

• its thicker walls are dehydrated by application of decolorizer, pores get smaller

gram-neg > pink

• typically anaerobic (no O2)

• walls too thin to retain crystal violet-iodine complex

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Pathogenic Cocci (gram pos)

Streptococci = easily bent/twist, div along 1 axis

• streptos = easily bent/twist

• grow in chain/pair

• common in oral cav

• can be pathogenic (caries/infect)

Staphylococci = bunch of grapes, div in mult planes

• grow in clusters

• prod toxins

• assoc w skin infect + food poison (heat stable toxins)

Hemolysis (blood agar) - bact growth medium

• for identifying bact based on ability to lyse RBC

• important for streptococci classif

• caused by hemolysins (toxins)

3 types of hemolysis (based on cell wall antigen)

1. Alpha (α) = partial breakdown (of rbc)

• narrow zone of partial hemolysis

• greenish discoloration around colony

• ex: pneumonia

2. Beta (β) (4 types) = complete breakdown

• complete hemolysis

• clear/translucent zone of complete hemo around colonies

• more developed in liquid than solid media

• ex: pyogenes

group A = Streptococc pyogenes (GAS)

Common infects

• strep throat (pharyngitis)

• scarlet fever

• necrotizing fascitis

Post-infect complication

• rheumatic fever

• acute glomerulonephritis

group B = Streptococcus agalactiae (GBS)

Neonatal infects*

• meningitis

• sepsis

• colonize fem reprod tract

• screening for GBS 35-37 weeks preg*

• intrapartum antibiotics prev transmit when labour

group C

• primarily animal pathogens* (rare in human)

group D = Enterococcus*

• usually gamma hemolytic (no hemolysis)

• common species = enteroccocus faecalis, faecium

clinical relev of group D

• opportunistic infects

• often antibiotic resist

• important in hospital-acquired infects

3. Gamma (γ) = no breakdown

• no hemolysis

• ex: nonhaemolytic strept

note that β (complete) & γ (none) for hemolysis

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clinical relev

• opportunistic infects

• often antibiotic resist

• important in hospital-acquired infects

review

1. clear zone, which condition?

A. Dental caries

B. Neonatal meningitis (group B of beta show clear)

C. Infective endocarditis from oral flora

D. Vitamin K production in the gut

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2. which statement best explain why enteroccocus species clinical signif?

A. They produce a green discoloration on blood agar and commonly cause pneumonia

B. They are β-hemolytic organisms responsible for post-streptococcal complications

C. They are γ-hemolytic organisms associated with opportunistic and hospital-acquired infections (enterococcus is group D of beta, assoc w opportunistic & hosp infect)

D. They are primarily animal pathogens with minimal relevance in humans

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3. Student isolates a Streptococcus species that shows green discoloration on blood agar and is part of the normal oral microbiota. Which of the following is the most likely organism?

green = partial hemo = alpha

oral = alpha

A. Streptococcus pyogenes

B. Streptococcus agalactiae

C. Viridans streptococci caries

D. Enterococcus faecalis

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Hemolytic Anemia = increased breakdown of RBC

• RBC die faster than body can prod them

• RBC live 90-120 days

• balance between rbc prod (bone marrow) & removal (spleen)

2 types hemolysis

1. intravascular = within BVs

2. extravascular = mainly in spleen

what happen in hemolysis?

• inc RBC destruct = anemia

• inc hemoglobin breakdown = bilirubin

clinical signs

• jaundice

• dark urine

Streptococcal diseases (S. pyogenes - group A)

direct effects (infects/exotoxins)

• scarlet fever (toxin mediated)

• strep throat (pharyngitis)

• skin infect (impetigo, necrotizing fascitis)

• streptococcal toxic shock syndrome

delayed immune-mediated complics

• (due to immun resp from initial infect)

• rheumatic fever

• post-streptococcal glomerulonephritis

compare of bacterial protein toxins

1. Endotoxins (LPS)

source = outer mem of gram-neg bact (released on cell death (lysis)

chem comp = lipopolysaccharide (LPS) (lipid A = toxic compenent)

effect on host = systemic, nonspecific (fever, inflam, shock)

conversion > toxoid = not possible

lethal dose = large

2. Exotoxins

source = secrete by gram pos & neg bact

chem comp = protein

effect on host = specif targets (partic cells/tissues)

conversion > toxoid = possible (use in vaccines)

lethal dose = small (highly potent/powerful)

group A = Streptococc pyogenes (GAS) EXAMPLES

scarlet fever = upper resp infection

etiology (cause origin)

• group A (GAS) β-hemolytic (complete hemo) Streptococcus

• erythrogenic exotoxin-producing strain

transmission

• respiratory droplets

• direct contact

clinical feature

• acute pharyngitis (strepthroat)

• red sandpaper rash (start on neck, spread)

• orally = erythematous oral mucosa (strawb tongue)

strep throat = streptococcal pharyngitis

PRECEDES

cause

• group A β-hemolytic streptococc pyrogenes

transmit (highly contagious)

• resp droplets (cough sneeze)

• direct contact w infected person

clinical

• severe sore throat

• fever

• tonsillar exudates (PUS)

• pharynx inflam

• cough absence

• delayed immune resp concern

• common in children

• precede (before) complics (like rheumatic fever)

may spread to

• middle ear, sinus, blood stream (bacteremia)

can lead to

• rheumatic fever

• post-streptococcal glomerulonephritis)

diagnosis + duration

• throat swab (rapid antigen test or culture)

• duration: ~3–7 days

• symptoms improve faster with treatment

treatment

• penicillin (firstline/preferred)

• some allergic so = cephalexin ect…

• reduce symtpoms & prev complics

rheumatic fever= post-streptococcal disease (after strep)

• immune-mediated (antibody cross-rxn where antibody can bind to diff antigen w similar culture)

• NOT due to active infect

pathogenesis (biological origin)

• heart valve inflam (carditis)

• subsequentially, abnorm growth of CT > scarring of valve > rheumatic heart disease

clinical

• fever, malaise (gen discomfort)

• polyarthritis (migrating joint pain)

• carditis > valve damage

late effects

• breath shortness

• enlarged heart, congestive heart fail (CHF)

• inc risk of infective endocarditis

dental

• damage valve > risk infective endocarditis

• prophylactic antibiotic

treatment**

• penicillin/amoxicillin to eradicate pyogenes

• if allergic > erythromycin

prevent

• promptly treat strep throat

epidemiology

• common age 5-15 (less as u age)

• reccurent attack = cumulative valve damage

glomerulonephritis

• antibody-mediated inflam of glomeruli (kidney)

• 1-3 weeks after streptococcal infect (pharyngitis/skin infect)

pathogenesis

• immune complex deposition (complex buildup) > kidney damage

clinical sign

• edema (face/eye swell)

• hematuria (urine blood)

• proteinuria

• hypertension

skin infections

common types

• folliculitis (follicle infect)

• cellulitis (deep dermal infect)

• impetigo (superf infect - vesicles, blisters) PHOTO of crusty lesions around mouth common in children

common pathogens

• staphylococc aureus

• streptococc pygoenes

treatment

• dicloxacillin (covers staph & strep)

cellulitis

• bact infect of skin & subcutaneous tissue

common cause

• group A streptococcus (pyogenes particularly)

• staphylococc aureus

• occur when bact enter thru broken skin

signs symptoms

• redness, swell, warm, tender, pain

• can become serious/systemic (bacteremia, sepsis)

necrotizing fasciitis

• severe rapid spread infect of fascia + soft tissue

type 1 = polymicrobial (mixed bacteria)

type 2 = monomicrobial - usually pyogenes (group A strep)

common pathogens

• strept pyogenes (most important)

• staphylococcus aureus

rapid tissue destruct due to…

• exotoxins (potent) = ex: streptococ pyrogenic exotocins

• ischemia = reduced blood supply

• pyrogenes produces superantigens = massive immune resp (cytokine release)

• medical emergency immed treat

• enter thru break in skin

clinical signs

• rapid spread of redness, swell, heat

• sever pain

treatment

• emergency surgical debridement

• antibiotics (penicillin target pyogenes / clindamycin inhib toxin prod)

• high mortality rate (despite treat)

viridians streptococcus

• alpha-hemolytic bacteria

• part of normal flora of oral cav

• major cause of subacute infective endocarditis (esp in patients w damaged valves)

• can enter blood stream during invasive dental procedure (bacteremia = bact presence in blood)

infect risk depend on…

• host factor (immune status)

• presence of damaged valves

• degree of bacteremia

streptococcus pneumoniae

• gram-pos lancet-shaped diplococci

• alpha hemolyitic

• encapsulated (MAJOR VIRULENCE FACTOR)

key identif

• optochin sensitive

• bile soluble

• quellung rxn pos (test capsule present)

transmission + pathogenisis

• spread via respiratory droplets

• can be asymptomatic carrier (nasopharynx)

risk

• age extremes (old + children)

• immunocompromised (HIV, chronic ill)

• chronic disease (COPD restricted airflow, alc/smoke

• hosp/debilitated ppl

clinical presentation

• sudden onset fever/cjhills

• chest pain (pleuritic)

• productive cough > rust color sputum

• may involve 1 lung lobe (lobar pneumonia)

pathophysiology + complics

• cause lobar pneumonia (localized inflam)

• often follow viral infect (ex: influenza)

• 
  

can lead to…

• meningitis

• sepsis

• otitis media (ear infect) in children

---

role of oral flora

• oral bact can be aspirated into lungs

• risk inc with poor oral hygiene + hosp/nursing patient

prevention

• good hygiene

• biofilm control

• standard precaution

• antimicrobial rinse

treatment for pneumoniae

• penicillin (impact cell wall integrity)

• perform antibiotic susceptibility testing

• if restistant > cephalosporins, macrolides, fluoroquinolones

• vaccine!

further prev (vaccine)

• pneumococcal vaccine = targets substative polysacc capsule

• recc adults 65+

• high risk = ppl w chronic disease/immunocompromised

review

Which patient is at highest risk for severe infection with Streptococcus pneumoniae?

A. Healthy 25-year-old with no medical history

B. 30-year-old with mild gingivitis

C. 70-year-old with chronic lung disease (chronic disease copd + 65+)

D. 18-year-old athlete

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Why are immunocompromised individuals more susceptible to severe Streptococcus pneumoniae infections?

A. The bacteria only infects damaged heart valves

B. They produce excessive inflammatory responses

C. Their immune system is less able to clear encapsulated bacteria

D. The bacteria becomes resistant only in these patients

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A sputum culture from a patient with pneumonia grows alpha-hemolytic colonies. The organism is optochin sensitive and bile soluble. Which feature is most critical for its ability to cause disease? (wont ask smt like this)

A. Production of endotoxin (LPS)

B. Presence of a polysaccharide capsule (virulence factor)

C. Ability to form spores

D. Production of superantigens

group B = Staphylococcus aureus) EXAMPLES

• gram-pos cocci in clusters

• beta hemolytic (complete breakdown rbc)

• common opportunistic pathogen

can cause…

• skin infect

• pneumonia (esp severe case)

• ^rare cause of pneumonia in healthy adult

more common in

• hosp patients

• post-viral infect (influenza)

• young children (under 2)

risk factor & pathogenesis = opportunistic patients with…

• surgery, burns, invasive procedure

• immunocomp state

• antibiotic therapy

• hospital environment = major resevoir

• often involve multidrug-resistant strains (MRSA)

infect may follow

• colonization (can persist for months)

• cean lead to abscess form + sever inflam/rapid progression

treatment & clinical notes

• methicillin historically used

• MRSA strains > vancomycin (or other alts)

• can also cause infective endocarditis

• (note viridans streptococ is most common cause of endocarditis, not so much aureus in gen dental context

• ^wont test deeply

importance of carriers

• they transmit pathogens w/o symptoms

• inc risk for immunocompromised

• common orgs = streptococc pyogenes + staphylococc aureus

• ex: typhoid mary (spread thru stool fecal-oral transmit)

infective endocarditis

• inflam of endocardium of valves (sometimes around congenital defects from infect)

• usually bacterial (ex: viridans stretococc, s. aureus)

• rarely fungal

***

carrier = harbour pathogen w/o symptom

bacteremia = bact in blood stream

transient bacteremia = short-term presence (temp after procedure)

septicemia = systemic infect of blood stream

bacteremia = dental procedures can cause

examples

• scale/floss, extraction, perio procedure, endodontic treat

risk in

• immunocomp ppl

• ppl w heart valve disease

• predisposing conds (valve prostheses, septal defect, atheroma of valve, ect…)

can lead to

• infective endocarditis (in suscept patients)

endocarditis

infective endocarditis (IE) = broad

• any infect of endocardium/valves

causes = bacteria (common) fungi (rare)

bacterial endocarditis = subset of IE

• ONLY caused by BACT

• inflam of endocard tissue

• life threatening

treatment = bactericidal (not static), parenterally delivered (inject/infuse), prolonged up to 4 weeks

pathogenesis

• req bacteremia (bact in stream)

• occur when organisms attach to damaged endocardium

bacteremia may arise from

• dental procedure

• spont entry from oral flora

• infections (UTI, pneumonia, skin infect)

higher risk in

• structural heart defects

• prosthetic valves

• immunocomps

endothelial tissue

normal endocard = smooth simple squamous epith

damaged to it = turbulent flow, defects, prosth valves

• exposes underlying tissue

• lead to platelet + fibrin deposition

• create surface for bacterial adherance > vegetation formation

abnormal tissue = simple squamous forms epithelial ridges/extension as the tissue break down > allow adhere of bact clusters

symptoms of endocarditis

• fever

• malaise

• weight loss

• anemia

• splinter haemorrhages

types of endocarditis

1. acute bacterial endocarditis (ABE)

• rapid onset (severe)

• usually high virulent orgs

• common = staphylococc aureus

2. subacute bacterial endocarditis (SBE)

• gradual onset (week>months)

• less virulent

• common = viridans streptococc

• often follow transient bacteremia

• typically affect abnormal valves

moreso read?

antibiotic before cleaning

prevention of infective endocarditis = as DH

• identidy high-risk patient (med hist + consult their physician)

• confirm need for antibiotic prophylaxis (if indic)

primary prev = oral health

• maintain optimal hygiene, remove biofilm at home

important clarif

• antibiotics not given routinely (only high risk patients undergoing invasive procedure

1. if have prosthetic valve

2. previous infective endocarditis

3. CHD = congenital heart disease

infective endocarditis prophylaxis******

• 30-60 min before procedure

• for standard (able to take oral med)

• AMOXICILLIN

adult = 2g PO (mouth)

children = 50mg/kg PO

calculate dosage

ex: 45 yo need antibiotic prophy and can take oral med; correct dose of amoxycillin

2g PO

ex: child weight 20kg need oral amoxicillin

50mg/kg = 20 × 100 = 2,000

2,000 ÷ 2 = 1,000

ex: if 50 kg, 50×50 = 2500

ex if 30 kg, 50×30 = 1500

ex if 35kg, 35×50 = 1750

review

Which of the following best describes infective endocarditis (IE)?

A. Inflammation of the myocardium caused only by bacteria

B. Infection of the endocardium or heart valves caused by microorganisms

C. Autoimmune inflammation of heart valves following infection

D. Infection limited to the pericardial sac

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Which organism(s) is/re most commonly associated with subacute bacterial endocarditis (SBE) following dental procedures?

A. Staphylococcus aureus

B. Group A Streptococcus

C. Viridans streptococci

D. Escherichia coli

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Which patient requires antibiotic prophylaxis before dental procedures?

A. Patient with controlled hypertension

B. Patient with mitral valve prolapse without regurgitation

C. Patient with previous infective endocarditis

D. Patient with a pacemaker

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What is the initial event that allows infective endocarditis to develop?

A. Viral infection of the myocardium

B. Formation of emboli in the lungs

C. Bacteremia with microorganisms entering the bloodstream

D. Autoimmune destruction of heart valves

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Autoimmune destruction of heart valves Which dental procedure is most likely to cause bacteremia?

A. Taking dental radiographs

B. Applying topical fluoride

C. Scaling and root planing with bleeding

D. Oral hygiene instruction

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A 62-year-old patient presents for a professional cleaning. Their medical history reveals: • Previous infective endocarditis • No known drug allergies • Able to take oral medications What is the most appropriate prophylactic antibiotic regimen?

A. No antibiotic needed; proceed with treatment

B. Amoxicillin 500 mg orally 1 hour before procedure

C. Amoxicillin 2 g orally 30–60 minutes before procedure

D. Azithromycin 500 mg orally after the procedure