ID Week 1

tetracyclines

doxycycline, demeclocycline, minocycline, tigecycline

macrolides

erythromycin, clarithromycin, azithromycin, roxithromycin, spiramycin, telithromycin (to remember: teli-RACES)

streptogramins

quinupristin-dalfopristin

lincosamides

lincomycin, clindamycin

oxazolidinones

linezolid, tedizolid

aminoglycosides

gentamicin, amikacin, netilmicin, sisomicin, neomycin, kanamycin, tobramycin, streptomycin

sulfonamides

sulfadiazine, sulfadoxine, sulfamethoxazole

fluoroquinolones

norfloxacin, ciprofloxacin, gatifloxacin, levofloxacin

beta lactams

penicillins, cephalosporins, monobactams, carbapenems`

glycopeptides

vancomycin, tiecoplanin, telavancin, dalbavancin, oritavancin

polypeptides

polymyxin B, colistin, bacitracin

lipopeptide

daptomycin

other cell wall active agents

fosfomycin, clycloserine

agars allow for

Agars allow for assessment of purity!

chocolate agar

boiled blood so nutrients are released from RBCs

what bacteria grow on chocolate agars

- Neisseria, Haemophilus, and other ‘ellas’

MacConkey agar

crystal violet kills G+

Lactose fermentation (P = Positive = Pink)

- You’ll only find G- here!

Mannitol Salt Agar

Depending on the kind of agar used, it can help you differentiate what colonies are present!

Positive = Yellow = Staphylococcus aureus

Negative = coagulase negative Staph

Blood Agar!!!

DIFFERENTIAL: HEMOLYSIS

Gram Negative Lab Algorithm

Gram Positive Lab Algorithm

actinomyces colony

Gram Stain!!! order/steps

If you’re Gpositive cocci → whats next

catalase is always next

If Gram negative rod → what’s next

oxidase is next!

Streptococci all catalase ______

Strep Pneumoniae: spread

Human only pathogen; colonizes oropharynx (endogenous, hematogeous spread)

Strep Pneumoniae: can cause

Can cause: sinusitis, otitis media, pneumonia (#1 cause), meningitis, sepsis

Strep Pneumoniae: VF

VF: Polysaccharide capsule, IgA protease

Strep Pneumoniae: shape and gram status

Lancet-pairs (diplococci); Gram positive

Strep Pneumoniae: hemolysis and optochin and bile

Alpha hemolytic → sensitive to optochin → bile soluble

Strep Pneumoniae: treatment

Penicillin, 3rd gen cephalosporin

- Ceftriaxone, Levofloxacin, Clindamycin

Strep Pneumoniae: prevention

Prevention: vaccination (capsules)

Viridans group Streptococci: transmission

Human only; oral normal flora (endogenous, hematogenous spread)

Viridans group Streptococci: epi

Dental hygiene/work + abnormal (mitral) heart valve!

Viridans group Streptococci: symptoms

Slow infective endocarditis

Viridans group Streptococci: virulence factors

VF: no capsule, biofilm production

Viridans group Streptococci: hemolysis and optochin and bile

Alpha hemolytic → resistant to optochin → bile insoluble

Viridans group Streptococci: treatment and prevention

Tx: Penicillin, 3rd gen cephalosporin, vancomycin

Prevention: prophylactic abx before dental work

Strep pyogenes: transmission

Human only, oropharynx colonizer (endogenous spread; respiratory droplets - strep throat)

Strep pyogenes: diseases

pharyngitis, impetigo, scarlet fever (spares face), cellular, acute rheumatic fever (M protein- antiphagocytic, molecular mimicry), Glomerulonephritis (2wks post-infection)

Strep pyogenes: body parts affected

- Joints, <3, Nodules, Erythema marginatum, Sydenham chorea

Strep pyogenes: VF

VF: M protein, Streptolysin O, hyaluronic acid capsule, streptokinase

Strep pyogenes: hemolysis and bacitracin

Beta hemolytic → sensitive to bacitracin

Strep pyogenes: Tx

Tx: Penicillin, Vancomycin, Clindamycin, 3rd gen cephalosporin

Strep pyogenes: SpeA, B, C

Strep agalactiae - Group B Strep - Galactic Baby: transmission

Human only (GI, GU); vertical during birth to infant (ingested/aspirated)

Strep agalactiae - Group B Strep - Galactic Baby: epi

Epi: prenatal screening; prophylactic treatment at time of vaginal birth

Strep agalactiae - Group B Strep - Galactic Baby: diseases

Neonatal meningitis (#1 cause), sepsis, pneumonia

Strep agalactiae - Group B Strep - Galactic Baby: VF

VF: polysacc Capsule

Strep agalactiae - Group B Strep - Galactic Baby: hemolysis and bacitracin

Beta hemolytic → resistant to bacitracin

Strep agalactiae - Group B Strep - Galactic Baby: treatment

Tx: Penicillin/Ampicillin (give to mother if GBS+) Vancomycin, Clindamycin, 3rd gen cephalosporin

Strep agalactiae - Group B Strep - Galactic Baby: prevention

Prevention: prenatal screening or If colonized, either abx prophylaxis or C-section

Strep gallolyticus: transmission

Human colon flora (endogenous, hematogenous spread)

Strep gallolyticus: diseases

Linked to colon cancer Infective endocarditis, bacteremia

Strep gallolyticus: gram and hemolysis

Gram + , nonhemolytic (y-hemolytic)

Strep gallolyticus: PYR, NaCl?

No growth on 6.5% NaCL; PYR negative

Strep gallolyticus: treatment

Tx: ampicillin (+ gentamicin if invasive); vancomycin

Enterococcus spp. (ex: faecalis, faecium): transmission

Human and animal (ex: cow); oropharynx, GI, GU

Enterococcus spp. (ex: faecalis, faecium): disease

Common cause of HAIs → UTIs especially with catheters , wound infections, bacteremia

Enterococcus spp. (ex: faecalis, faecium): VF

VF: Biofilm formation, bile resistant

Enterococcus spp. (ex: faecalis, faecium): present in

Present in pairs or short chains

Enterococcus spp. (ex: faecalis, faecium): NaCL, PYR

Growth on 6.5% NaCL; PYR Positive

Enterococcus spp. (ex: faecalis, faecium): treatment + prevention

Tx: Ampicillin (+ gentamicin or ceftriaxone for invasive); Vanc, if resistant, linezolid Prevention: clean the hospital lol and reduce invasive devices

PYR Test L-Pyrrolidonyl -b-Naphthylamide (PYR) Test

Staphylococci - all Catalase POSITIVE: after catalase

Do coagulase test! Positive = Staph aureus

What does coagulase do?

S. aureus: body parts, symptoms, consequences

S. epidermidis: body parts, symptoms, consequences, treatment

A. Gram-positive cocci in clusters

A 4-day-old full-term newborn is brought to the emergency department for increasing lethargy, refusal to eat, and rapid breathing. The infant was born by normal vaginal delivery after an uncomplicated pregnancy. Vital signs are a heart rate of 145/min, a blood pressure of 70/30 mm Hg, a respiratory rate of 70/min, and oxygen saturation of 92% in room air. On physical examination, the infant is lethargic, capillary refill is delayed, and there are mild intercostal retractions. A chest x-ray reveals diffuse infiltrates. A CBC shows a WBC of 30,000/mm3 (normal 9,000-13,000/mm3 for newborns) with 10% band forms and a markedly elevated C-reactive protein. A lumbar puncture is performed, and CSF values are normal. Blood cultures are drawn, and antibiotics are started. The infant is admitted to the neonatal intensive care unit and supported with nasal CPAP and oxygen. The following day, the blood culture is reported as positive for gram-positive cocci. Which of the following organisms is most likely to be causing the infection?

E. Streptococcus agalactiae

Clostridioides difficile:

G+ rod; obligate anaerobe; spore former

Clostridioides difficile: transmission

Found in soil, feces (intestines) of humans → easily spread person to person (ingestion of spores)

Clostridioides difficile: Risk factors

65+, broad-spectrum antibiotics, stay in hospitals/nursing homes for long period pf time, gastric acid suppression, ppl with weakened immune system, previous C.diff infection

Clostridioides difficile: symptoms

Pseudomembranous Colitis: watery diarrhea (can have blood, mucus), abd distention, cramps, fever, dehydration

Clostridioides difficile: VF

VF: spores, toxin AB (inactivates GTP-binding proteins)

Clostridioides difficile: diagnosis

Diagnosis via colonoscopy, psuedomembranes

Clostridioides difficile: treatment

Tx: oral Vancomycin or Fidaxomicin; fecal transplant (after 3 infections no bueno)

Clostridium perfringens:

G+ rod, obligate anaerobe, spore former

Clostridium perfringens: found in

nature, human/animal intestinal microbiota

Clostridium perfringens: what on what agar

Double hemolysis on blood agar

Clostridium perfringens: spores

Spores can contaminate food - gravy, poultry, meat, or traumatic entry of spores in wounds (ex: deep puncture wound after accident, gas gangrene)

Clostridium perfringens: vomiting?

No vomiting!!

Clostridium perfringens: onset and symptoms

Fast onset; watery diarrhea and ion loss; resolves within a couple days Gas gangrene (myonecrosis): spores in deep wound, alpha toxin (lecithinase activity) - progresses fast → crepitus under skin, purple bullae with discoloration

Clostridium perfringens: prevention

Prevention: cook ur food fr; GG: clean wounds thoroughly ASAP!!

Clostridium tetani:

G+ rod; obligate anaerobe; spore former

Clostridium tetani: how does infection occur

Traumatic introduction of spores in wound; found in soil and some feces

Clostridium tetani: risk factors

RF: deep puncture wound, crush injuries, IVDU, septic abortion

Clostridium tetani: symptoms

Tetanus: spores in wound = starts with ‘lockjaw’ → arched back → respiratory paralysis

Clostridium tetani: treatment

Tx: toxoid vaccination; clean ur wounds, human tetanus shot

Tetanospasmin (tetanus) toxin

Cutibacterium acnes:

G+ rod; obligate anaerobe; non-spore former

Cutibacterium acnes: found in

Part of skin flora, commensal ; lives on fatty acids in sebum (follicles)

Cutibacterium acnes: symptoms

Acne Vulgaris: pimpols

Actinomyces Israelii:

G+ branching filamentous rods; anaerobe; opportunistic pathogen

Actinomyces Israelii: reservoir/transmission

R/T: normal flora of skin, mouth gut, vagina - most infections are endogenous

Actinomyces Israelii: RF

RF: oral infection - infection in erupting teeth, dental caries, gingivitis, dental extraction

Actinomyces Israelii: symptoms

Commonly forms abscesses, ‘lumpy jaw’ - develops slowly and drains pus through sinus tract Hard, yellow granules (sulfur granules) = composed of pus!! Not sulfur