Common bacterial infections Flashcards

Question

How is botulism prevented?

Answer 1

Prevention - Avoiding suspicious foods (canned foods improperly preserved) - Heat all canned foods to 85C for >5min - Avoid honey until 1 yo - Continue BF

Answer 2

- Gram (+) aerobic bacteria, coagulase (+) - Most common cause of pyogenic infections of the skin and soft tissues Transmission: Autoinoculation or direct contact

Answer 3

CM: 1. Osteomyelitis, suppurative arthritis, abscesses, pyomyositis, empyema, IE 2. Toxin-mediated: food poisoning, scalded skin syndrome, toxic shock syndrome 3. Pyogenic skin infections: impetigo, ecthyma, cellulitis, necrotizing fasciitis 4. Sepsis 5. Respi: tracheitis, PNA (empyema, pneumatoceles) 6. Renal abscesses 7. Acute endocarditis of native valves 8. Meningitis Dx: 1. CBC 2. C/S of focus/blood

Answer 4

Mgt: 1. Abscess: I&D 2. Abx: MSSA: Oxacillin 100-200 mkd IV q4/6 co-amox 20-40 mkd q8/12 po/IV MRSA: vancomycin 40-45 mkd IV q6/8 Clindamycin 30mkd IV/po q6/8

Answer 5

Transmission: - Sexual contact or perinatal (via contact with cervical canal during delivery or with contaminated amniotic fluid) - Intracellular diplococcus - Often with co-infection with Chlamydia

Answer 6

Patho - Infects primarily columnar epithelium à local inflammatory response that produces a purulent exudate consisting of PMN leukocytes, serum, and desquamated epithelium à endotoxin is cytotoxic causing ciliostasis and sloughing of ciliated epithelial cells

Answer 7

CM 1. Asx’c (80% F, 10% M) 2. Uncomplicated: purulent exudate (urethritis cervicitis, vulvovaginitis, ophthalmitis) 3. Disseminated gonococcal infection (DGI): polyarthralgia + fever + pustular lesions - From hematogenous dissemination - Sx begin 7-30d after infection, within 7d of mens - Asymmetric arthralgia, petechial or pustular acral skin lesions, tenosynovitis, suppurative arthritis - Most common initial sx is acute onset polyarthralgia with fever - Painful, discrete, 1-20mm pink/red macules that progress to MP, vesicular, bullous, pustular, or petechial lesions. Typical necrotic pustule on an erythematous base distributed unevenly over the ext (incl palmar and plantar surface) spacing face and scalp. - 2 clinical syndromes: a. Tenosynovitis-dermatitis syndrome: F, chills, skin lesions, polyarthralgia (wrists, hands, fingers). Synovial fluid Cx (-) b. Suppurative arthritis syndrome: monoarticular arthritis (knee) 4. Neonatal infections: Ophthalmia neonatorum: 2-5d after birth 5. Gonococcal arthritis 6. Amniotic fluid syndrome: PROM, inflammation of placenta and umbilical cord 7. Sepsis and meningitis 8. Scalp abscess 9. Pelvic inflammatory disease (PID) – ascending infection from the urogenital tract causing urethritis, epididymitis (M), edometritis, salphingitis, peritonitis (F) - Fitz-Hugh-Curtis syndrome: dissemination to fallopian tube through peritoneum to the liver capsule

Answer 8

Dx 1. DischargeGS/CS – any exudate, eye discharge, nasopharynx, OGT, anorectal area, blood 2. Lumbar puncture with spinal fluid studies 3. C/S for concomitant Chlamydia 4. CBC – elev WBC 5. Nucleic acid amplification test (NAAT) – Sn and Sp

Answer 9

Mgt: 1. Nondisseminated infection, ophthalmia neonatorum: ceftriaxone 250mg IM single dose or cefotaxime 100-200mkd IV q6/8 or Cefixime 400mg po single dose or Single dose cephalosporin IM Plus Azithromycin 1g po SD or doxycycline 100mg po BIDx7d Ceftriaxone remains the empiric abx for gonococcal infections 2. Arthritis and septicemia: ceftriaxone, cefotaxime x7d 3. Meningitis: ceftriaxone or cefotaxime x 10-14d 4. All infants: contact isolation until effective IV abx x 24h

Answer 10

CH 199: SHIGELLOSIS - Dysentery - Acute invasive enteric infection - Ingestion of contaminated water or food - Most common in 2-3 yo Transmission: - Person to person (fecal-oral route) - Requires very small inocula to cause illness IP: 12h-7d

Answer 11

Patho - Bacteria invade intestinal epithelium through M cells causing death and sloughing of invaded epithelial cells and potent inflammatory response - Shiga toxin is a potent exotoxin that inhibits protein synthesis --> injure vascular endothelial cells --> HUS

Answer 12

CM: 1. HG fever + severe abdominal pain + painful defecation (tenesmus) 2. Diarrhea: watery large volume à small frequent volume, bloody, mucoid stool 3. Abdominal distention, tender rectum, HABS, emesis, anorexia, generalized toxicity 4. CNS (40%): seizure – most common extraintestinal manifestation 5. Dehydration – most common complication

Answer 13

Dx: 1. Stool exam: >50-100 PMNs/hpf, fecal blood (presumptive dx), leukocytosis 2. Stool C/S: gold standard 3. BCS: very young, malnourished 4. CBC: inconsistent WBC, shift to the left (inc bands), leukopenia or leukemoid reactions. HUS shows anemia and thrombocytopenia

Answer 14

Tx: 1. Ciprofloxacin 25mkd BID x 3d – for bloody diarrhea 2. Ceftriaxone 100mkd x 5d 3. Cefixime 8mkd OD po 4. Azithromycin 10mkd po x 3d 5. Increasing resistance to fluoroquinolones

Answer 15

Transmission - Person to person - Fecal-oral route (contaminated food & water) IP: 10h to 6d Communicability: as long as the person excretes the bacteria (1-4 wks)

Answer 16

Patho - After ingesting E.coli 0157:H7, the bacteria bind to the intestinal mucosa and release Shiga toxin --> disrupt protein synthesis in the epithelial cells lining the intestinal mucosa --> cell death, mucosal sloughing, bloody diarrhea

Answer 17

ETEC: most common cause of traveler's diarrhea patho: adherence factors; heat-labile and heat stable enetrotoxins watery diarrhea manifestations: abdominal pain, nausea, vomiting, little or no fever; usually self-limited EIEC: >1yr old patho: adherence; invasion and inflammation of large intestine diarrhea: watery diarrhea or dysentery manifestations: fever, systemic toxicity, crampy abdominal pain, *tenesmus, often with positive leukocytes EPEC: <2yrs old patho: adherence; effacement of intestines watery, nonbloody diarrhea with mucus vomiting and low grade fever EHEC or Shiga-toxin-producing or verotoxin producing E.coli 6mos-10yrs old; elderly; poorly cooked hamburger is a common cause of outbreaks patho: shiga-toxin production, large bowel attachement; E.coli 0157:H7 is the most virulent serotype and most frequently associated with HUS Diarrhea: initially watery but becomes bloody Fever is not commonly present; 5-10% develop systemic complications such as HUS Enteroaggressive E. coli (EAEC) <2yo; HIV patients, travelers patho: small and large intestine adherence; enterotoxin and cytotoxin production diarrhea: watery, mucoid diarrhea; some patients may have bloody stools low grade fever; little to no vomiting Diffusely adherent (DAEC) >1yr old; travelers patho: adherence factors; toxin production diarrhea: watery abdominal pain and fever

Answer 18

Dx: 1. Serotype O157:H7 – isolation of E.coli that fails to ferment sorbitol on McConkey sorbitol medium 2. Tissue C/S 3. CBC – leukocytosis with left shift 4. Stool exam – leukocyte (+) with EIEC 5. FOBT – (+) in some strains

Answer 19

Mgt: 1. Supportive – fluid and electrolyte tx 2. Early refeeding: with 6-8h from starting rehydration 3. Antimicrobials – not given for STEC or EHEC due to inc risk of HUS - For ETEC, EPEC, severe watery diarrhea – cotrimoxazole 8-12mkd IV/po q12 For resistant strains: Ciprofloxacin 20-30mkd q12 po/IV Azithromycin 10mkd po x 3d 4. zinc supplements – for malnourished children prevention 1. proper food and water handling, handwashing

Answer 20

- Syphilis - Spirochete

Answer 21

Transmission: - Vertical via transplacental or SVD - Sexual contact Patho - Bacteria rapidly penetrates intact mucus membranes/abrasions --> primary lesion --> CNS -->What delayed type hypersensitivity in tertiary syphillis

Answer 22

CM: 1. Primary syphilis (4-6 wks) - Painless chancre: ulcer with raised border at entry site (genital area) + regional lymphadenitis - Firm, round, small - Highly infectious - 10-90d after infection - Heals spontaneously with thin scar (3-6 wks) 2. Secondary - Highly infectious - Syphilitic roseola: few weeks after the chancre heals a. Nonpruritic maculopapular rash in palms and soles b. Wart-like growth c. Heals spontaneously (2-6wks to 12wks) - If untreated: spirochetenemia - Condyloma lata: wart-like plaques in anus or vagina, axilla, groin, buccal mucosa - Mucus patches 3. Latency stage - Infected person is asx’c but continues to have the infection a. Early latent stage - Potentially infectious - Seroreactive w/in 1 year of infection - No sx b. Late latent stage § Not infectious § Seroreactive more than 1 yr after infection § No sx 4. Tertiary/late - Not infectious - Gumma: skin and musculoskeletal - Internal organs - Plus neurologic (neurosyphilis) and CV - Paralysis, numbness, blindness, dementia, death 5. Congenital syphilis - Vertical transmission 100% - Transmission to fetus: as early as 9wks aog - The longer the interval between infection and pregnancy, the more benign the outcome in the infant - Asymptomatic to fatal - Early: 1st 2 yrs a. abortion, stillbirth, hydrops b. osteochondritis, periostitis c. Mucocutaneous rash: erythematous, MP or vesiculobullous followed by desquamation of hands and feet, mucous patches (white plaques) d. Condylomatous lesions e. persistent rhinitis (snuffles) f. Pseudoparalysis of Parrot – painful osteochondritis, refusal to move affected limb g. Congenital neurosyphilis: encephalitis h. Consumptive coagulopathy: thrombocytopenia, splenomegaly i. MOF: hepatosplenomegaly, jaundice, elev LFT, Coomb’s negative hemolytic anemia j. Renal: nephritis, nephrotic syndrome, hypertension, hematuria, proteinuria, hypoproteinemia, hypercholesterolemia - Late: >2yo a. chronic granulomatous inflammation b. Osteitis of the long bones, maxillofacial and dental malformation c. Keratitis, hearing loss d. Hutchinsons teeth: peg-shaped upper central incisors e. Mulberry molars: excessive # of cusps of molars f. Saddle nose: depression of nasal roof g. Rhagades: spokelike linear scar at mouth, anus, genitalia h. Neuropsychological deficits i. Olympian brow: bony prominence of forehead j. Clavicular/Higoumenakia sign – thick clavicle k. Saber shins: anterior bowing of mid-tibia l. Scaphoid scapula: convex midscapula m. Juvenile paresis: latent CNS infection, focal sz, behavioral changes, MR n. Juvenile tabes: SC, aortitis o. Hutchinson triad: Hutchinson teeth, interstitial keratitis, CN8 deafness p. Clutton joint: painless joint swelling q. Interstitial keratitis: leads to blindness r. CN8 deafness - Blood and lesions: highly infectious until 24h or tx

Answer 23

Dx: 1. Darkfield microscopy – for early ds - Definitive dx - Serous transudate from moist lesions a. Primary chancre, condyloma latum, mucus patch, placenta - Consider a suspicious lesion to be nonsyphilitic a. After 3 competent examinations with negative findings - Oral cavity specimen a. Cannot be used b. Nonpathogenic treponemes are part of the oropharyngeal flora 2. Non-treponemal test: screening test a. RPR (rapid plasma reagin) b. VDRL (venereal disease research laboratory) - Detects Ab against Ag on the treponemal surface - Elevated in: active ds, re-infection, tx failure 3. Treponemal tests: confirmatory a. TP-PA: treponema pallidum particle agglutination b. FTA-ABS: fluorescent treponemal Ab absorption c. TP-EIA: pallidum enzyme immunoassay d. MG-TP: microhemagglutination test of Ab to Tpallidum - Useful to confirm dx of 1st episode of syphilis - (+) for life - Measures specific treponeme Ab 4. All pxs should be tested for HIV

Answer 24

1. Primary, secondary, early latent: - Benzathine pen G 50,000 U/kg IM SD 2. Late latent, tertiary - Ben Pen 50,000-2.4M U IU IM weekly x 3 wks (3 doses) 3. Neurosyphilis - Aqueous crystalline pen G 18-24 M U/d administered as 3-4 M U IV q4h or continuous infusion x 10-14d 4. Congenital Syphillis - Proven: Aqueous Crystalline Penicillin G 100,000- 150,000 U/k/d administered as 50,000 U/k/dose q12 IV on d1-7 then q8h thereafter for a total of 10-15d or Procaine Penicillin G 50,000 U/kg SD x 10-15d - Possible: Aq Penicillin G or Procaine Pen as above for 10d or Benzathin Penicillin G 50,000 U/kg SD IM - Less likely: Ben Pen G 50,000 U/kg IM SD then f/u q2-3 mos for 6 mos

Answer 25

CH 194: HAEMOPHILUS INFLUENZAE B - Humans are the only natural host - Normal respiratory flora in healthy children - Invasive ds in <5yo - Transmission - Direct contact/ extension from nasopharynx - Inhalation of respi droplet Patho - Polysaccharide capsule major factor in virulence. Encapsulated organism can penetrate the epithelium of the nasopharynx and invade the blood capillaries directly.

Answer 26

76 Mgt 1. Primary, secondary, early latent: - Benzathine pen G 50,000 U/kg IM SD 2. Late latent, tertiary - Ben Pen 50,000-2.4M U IU IM weekly x 3 wks (3 doses) 3. Neurosyphilis - Aqueous crystalline pen G 18-24 M U/d administered as 3-4 M U IV q4h or continuous infusion x 10-14d 4. Congenital Syphillis - Proven: Aqueous Crystalline Penicillin G 100,000- 150,000 U/k/d administered as 50,000 U/k/dose q12 IV on d1-7 then q8h thereafter for a total of 10-15d or Procaine Penicillin G 50,000 U/kg SD x 10-15d - Possible: Aq Penicillin G or Procaine Pen as above for 10d or Benzathin Penicillin G 50,000 U/kg SD IM - Less likely: Ben Pen G 50,000 U/kg IM SD then f/u q2-3 mos for 6 mos CH 194: HAEMOPHILUS INFLUENZAE B - Humans are the only natural host - Normal respiratory flora in healthy children - Invasive ds in <5yo - Transmission - Direct contact/ extension from nasopharynx - Inhalation of respi droplet Patho - Polysaccharide capsule major factor in virulence. Encapsulated organism can penetrate the epithelium of the nasopharynx and invade the blood capillaries directly. CM 1. Non-invasive: otitis media (most common cause), sinusitis, conjunctivitis 2. Invasive: bacteremia, meningitis, sepsis 3. Respi: epiglottitis, PNA 4. Cellulitis: preseptal, orbital 5. Suppurative arthritis, osteomyelitis

Answer 27

Dx: 1. GS, C/S 2. Serotyping by agglutination

Answer 28

Mgt 1. Ampicillin 100-200 mkd IV q6 or ceftriaxone 50-75 mkd IV q12/24 2. Amoxicillin 25-50 mkd po q8/12 – for OM, sinusitis 3. Meningitis: cefotaxime 100-200 mkd IV q6/8, ceftriaxone, ampicillin x 14d for uncomplicated cases 4. High rate of resistance to amipicillin 5. Recommended empiric tx = B-lactam inhibitor combinations, extended spectrum oral cephalosporin

Answer 29

Prophylaxis: - For unvaccinated <48mos child with close contact: - Rifampicin OD 10mkdose x 4d @0-1 mos 20mkdose @ >1mo - Hib conjugate vaccine

Answer 30

Streptococcus pneumonia (pneumococcus) - Gram (+), lancet shaped polysaccharide encapsulated diplococcus - Encapsulated strains cause most serious disease in humans - Important cause of secondary bacterial PN in px with influenza - Major cause of life-threatening PN, meningitis, septicemia

Answer 31

otitis media, sinusitis, pneumonia and sepsis diagnosis: culture; identification of the organism from the site of infection, blood, or sterile body fluid Management: Meningitis: in px >1month old: Vancomycin IV 60mg/kg/day q6hrs and high-dose Cefotaxime IV 300mg/kg/day q8hrs OR Ceftriaxione IV 100mg/kg/day q12hrs Otitis media: High doses of Amoxiciliin 80-100 mg/kg/day Allergic to Pen: Macrolide or Cotrimoxazole Control measures: use of PCV 13 and PCV 23 vaccines - Tx: penicillin

Answer 32

Group A streptococcus (GAS)/ Streptoccocus pyogenes - MC site of infection = pharynx > skin (pyoderma, impetigo) - Nonsuppurative complications: c. ARF (sequela of pharyngitis, NOT skin infections) d. AGN (sequela of pharyngitis OR skin infections) - CM: acute pharyngitis, impetigo (pyoderma)

Answer 33

GBS Streptococcus agalactiae: gram (+) aerobic diplococci - 95% of strep infection in infants - Major cause of neonatal bacterial sepsis Group D Streptococcus/Enterococcus - Hospital acquired infection - Gram (+) - N flora of GIT - High abx resistance (ceph, nafcillin, oxacillin, methicillin)

Answer 34

CM 1. Sepsis, UTI, peritonitis, meningitis, endocarditis 2. Early-onset: <7d - Milder GBS-like sx, usually full term - 6% mortality 3. Late-onset: >7d - Assoc with extreme PT, IVC, NEC - Severe toxic sx - RD, apnea, bradycardia, deteriorating respiratory function, meningitis - mortality 15% 4. older child: UTI (indwelling catheter)

Answer 35

Dx 1. CBC – leukocytosis, elev neu 2. BCS

Answer 36

Mgt: 1. Pen G 100K- 400K ukd IV q4/6 or Ampicillin 100-200mkd IV q6 + Amik 15-22.5 mkd IV q8 2. Vancomycin 40-45 mkd IV q6/8 – if with pen allergy

Answer 37

CH 202: CAMPYLOBACTER JEJUNI - Ingestion of contaminated poultry, milk, water; pets or farm animals IP: 1-7d Patho - Host conditions assoc with reduced gastric acidity (PPI use), or foods capable of shielding org in transit through the stomach allow Campylobacter to reach intestines à invade and direct damage to mucosal cells through motility (flagellae) à lumen fluid accumulation

Answer 38

CM 1. AGE: acute bloody LBM - Fever, headache, myalgia - Watery or bloody mucoid stools - Crampy abdominal pain - Persistent AGE = fecal shedding 2-3w 2. Bacteremia 3. Focal extraintestinal infection - Meningitis, PN, UTI, arthritis, endocarditis, pericarditis 4. Perinatal infection

Answer 39

Dx: 1. Stool CS - >90% sn, DxOC 2. Fecalysis – (+) leukocytes and fecal blood 3. Rectal swab Mgt 1. Erythromycin 40 po q6 x 5d 2. Azithromycin 10mkd po x3d Complic 1. Reactive arthritis 2. GBS

Answer 40

CH 203: YERSINIA ENTEROCOLITICA - Ingestion of contaminated water/meat, undercooked pigs - Contact of infected animals and blood products - Reservoir: pigs Patho - Ability to form biofilms on surfaces, establish close contact and hijack eukaryotic target cells, and control cellular processes CM: 1. Acute enteritis with mesenteric lymphadenitis - Pseudoappendicitis: Abdominal pain, fever, diarrhea 2. Septicemia Dx: 1. Stool CS, BCS 2. Stool exam – (+) leukocytes Mgt 1. Self-limited: healthy children 2. Ceftriaxone 50-75mkd IV q12/24 + amikacin 15-20mkd IV OD: systemic infection TMP-SMX 8-12 mkd IV/po q12 x 5d is recommended

Answer 41

CH 226: CHLAMYDIA TRACHOMATIS

Answer 42

Patho - infects columnar epithelial cells à humoral response --> inc IgA, IgG, IgM --> unique biphasic life cycle allows adaptation to both intracellular and extracellular envt CM 1. trachoma: conjunctivitis à scarring à blindness - most important cause of preventable blindness in the world 2. STD - 75% asx’c - Mucoid d/c, PID (20-25%) - May present with urinary sx 3. NB: conjunctivitis, PN Dx: 1. Tissue C/S 2. Fluorescent Ab staining, NAAT, PCR of genital swab or urine Mgt 1. Recommended - Azithromycin 1g po SD - Doxycycline 100mg BID x 7d 2. Alternative - Erythromycin 500mg qid x7d - Levofloxacin 500mg od x7d - Ofloxacin 300mg bid x 7d 3. No sex for 7d after SD azithromycin or until 7d completed regimen and until all partners are treated to minimize reinfection DDx: TB (p. 36) Pertussis (p.46) Pneumonia (p.29) Salmonella (p. 92) Neisseria meningitides (p. 98)