Microbiology - Block 3 - Part 1

davidwurbel7's version from 2015-08-03 05:00

Clostridium botulinum

Question Answer
Anaerobic gram positive spore-forming rods. Reservoir: soil, aquatic sediments. Produces neurotoxin. Causes botulismClostridium botulinum
Ingestion of pre-formed toxin. Home-canned vegetablesFoodborne Botulism
Ingestion of spores or honeyInfant Botulism
Traumatic implantation of spores. Common with drug users. Toxin produced invivoWound Botulism
A-B polypeptide toxin. Highly toxic. Heat labile (destroyed at 60⁰C for 10 minutes)Botulinum Neurotoxin
Toxin absorbed by gut and carried by blood to peripheral nerve synapses. Blocks release of acetylcholine at the myoneuronal junction producing flaccid paralysisBotulinum Neurotoxin
1-2 days after consuming food (pre-formed toxin). Blurred vision, drooping eyelids, dry mouth, slurred speech. Diarrhea/constipation, abdominal pain, No feverFoodborne Botulism
Babies are lethargic, feed poorly, weak cry, constipated, poor muscle toneInfant Botulism (Floppy Baby Syndrome)
Similar symptoms, incubation period is longer, fever presentWound Botulism
If untreated these symptoms progress - cause paralysis of respiratory muscles, arms, legs and trunk. Recovery - may take months to years – until the affected nerve endings regrow. Early treatment is very importantBotulism
Detection of toxin activity in serum. Culture of bacteria from stool. Isolation from suspected foodClostridium botulinum Diagnosis
Treatment include adequate ventilatory support. Antitoxin - Trivalent antitoxin – to A, B and E toxins which binds and neutralizes toxin circulating in bloodBotulism Treatment
Antibiotics - Metronidazole or penicillinWound Botulism Treatment
Preventing spore-germination. Maintaining food in acid pH. Storage at 4OC or colder. Destroying preformed toxin in canned foods. Heating foods at 60 C to 100 C for 10 minutes. Infants below 1 year – not allowed to eat honeyBotulism Prevention

Clostridium perfringens

Question Answer
Anaerobic Gram positive rods. Gram-variable in tissues. Spore-forming. Double-zone of beta-hemolysis. Nagler reaction on egg-yolk agar. Stormy clot fermentation in litmus milk medium. Reservoir: soil and human colon. Transmission by foodborne,traumatic implantation, infects woundsClostridium perfringens
Food poisoning, Necrotizing enteritisGastroenteritis
Cellulitis, Suppurative myositis, Myonecrosis (Gas gangrene)Soft Tissue Infection
Phospholipase C (Lecithinase). Degrades lecithin in mamallian cell membranes. Damages RBCs, WBCs, platelets, endothelial cellsClostridium perfringens Alpha-Toxin
Heat-labile (destroyed by heating). Disrupts ion-transport (ileum) → watery diarrheaClostridium perfringens Enterotoxin
Reservoir in soil, colon (humans & animals). Raw meat and poultry. Beef, poultry, gravies, pre-cooked foodsClostridium perfringens Food Poisoning
Self-limiting, watery diarrhea (1 or 2 days). Starts 8-18 hours after ingestion of contaminated food. Diagnosis is mostly clinical. Lab diagnosis helps establish diagnosisClostridium perfringens Food Poisoning
Common cause of foodborne illness - 1 million cases in the US every yearClostridium perfringens Food Poisoning
Also called - Enteritis necroticans, pig-bel. Acute, necrotizing destruction of jejunum. Abdominal pain, vomiting, diarrhea & peritonitis. Rarely seenClostridium perfringens Necrotizing Enteritis
Localized edema and erythema. Gas formation in soft tissue. Generally non-painfulClostridium perfringens Cellulitis
Accumulation of pus (suppuration) in the muscle planes. No muscle necrosis, no systemic symptomsClostridium perfringens Suppurative Myositis (Fasciitis)
Rapid destruction of muscle tissue. Gas formation in soft tissue – crepitus. Necrotic bullae. Extremely painful. Systemic spread. High mortality, rapidly fatal (within 48 hours of onset)Myonecrosis (Gas Gangrene)
Acute & increasing pain swelling at wound site. Brownish skin discolouration, bullae. Edema, gas, exudates. Gas formation. Fermentation of tissue carbs, lipids, amino acids → gas accumulates → crepitus (can be felt under skin). Systemic signs → fever, tachycardia. Untreated – 100% fatalMyonecrosis (Gas Gangrene)
Lab tests - confirmatory. Gram stain: GPRods+ no WBCs * + other bacteria. Culture: anaerobically on Blood agar – double-zone hemolysis of coloniesClostridium perfringens
Debridement of wounds, delayed closure. Clindamycin and penicillin. Hyperbaric chamber – sometimes usefulClostridium perfringens Treatment

Neisseria meningitidis

Question Answer
Gram negative diplococci (pairs). Oxidase positive, catalase positive. Some species are normal flora on mucosal surfaces (oropharynx, genital tract)Neisseria
Gram negative encapsulated, diplococcus. Oxidase + , catalase + . Breaks down maltose & glucose. Common cause of meningitis. Most common cause in age group 2 – 18 yrsNeisseria meningitidis
Metabolizes maltose and glucoseNeisseria meningitidis
Virulence factors include polysaccharide capsule which is antiphagocytic. IgA protease. Endotoxin composed of lipooligosaccharide (LOS) which can cause Endotoxic shockNeisseria meningitides
Risk factors for severe infection are complement deficiency (C5-C8) and aspleniaNeisseria meningitides
Outbreaks in institutions, schools, military barracks, dormitoriesNeisseria meningitides
Vaccine for Neisseria meningitides is derived fromPolysaccharide Capsule
High fever (rapid onset). Nuchal rigidity (stiff neck). Photophobia (sensitivity to light), confusion, headache, vomitting. Petechia (purpural rash). Rapidly fatalMeningococcal Meningitis
Neisseria meningitides bloodstream infectionMeningococcemia
Failure of adrenal gland function due to bleeding into glandWaterhouse-Friderichsen Syndrome
Bilateral adrenal hemorrhage. Ecchymoses (large purple skin haemorrhages). DIC (disseminated intravascular coagulation). Hypotension & ShockWaterhouse-Friderichsen Syndrome
Empiric treatment in adultsCeftriaxone
Empiric treatment in infants for Neisseria meningitidesCefotaxime
Once antibiotic sessepibitiy test (AST) report shows susceptibility to penicillin then switchAmpicillin/Penicillin G
Prophylaxis for all close contacts should be given theseRifampin or Ciprofloxacin
Contains capsular polysaccharides from A, C, Y & W-135 serogroups. CDC recommends 11-12 year olds be vaccinated and a booster dose at 16 yearsConjugate Meningococcal Vaccine (MCV4)
New vaccine in US approved by FDA. Recommended for ages 10 -25 years of ageMeningococcal Serogroup B Vaccine

Neisseria gonorrhoeae

Question Answer
Gram negative diplococcus. Oxidase +, catalase + . Breaks down only glucoseNeisseria gonorrhoeae
Virulence factors include Pili, Outer membrane proteins, IgA protease, Lipooligosaccharide (LOS) which is antigenic and phase variationNeisseria gonorrhoeae
Each bacterium has the ability to express numerous different pili, it can change the pili at any time. The amino acid sequences of the pili vary, therefore the pili are antigenically distinct. Occurs with pili, OMP and LOSAntigenic and Phase Variation
Mucous membrane infection. Site of infection is dependent on type of sexual contact & sexual practices. Both asymptomatic and symptomatic persons may transmit disease. Untreated and repeated infections can cause scarring which may lead to infertility in both sexes. Predispose women to ectopic pregnancyGonorrhea
Urethritis, Epididymitis, ProstatitisMale Gonorrhea
Urethritis. Endocervicitis, Pelvic inflammatory disease (PID)Female Gonorrhea
Rectal infections, PharyngitisBoth Sexes Gonorrhea
Ophthalmia neonatorumNeonatal Eye Gonorrhea
Thick, yellow purulent exudate (gram stain shows numerous PMNs +GN diplococci). Frequent, painful urination. Complications include epidydimitis and prostatitisUrethritis (Male)
Purulent discharge (examine cervix). Frequent, painful urination, lower abdominal pain. Approx. 50% cases go undetected. Complications include salpinigitis, Pelvic inflammatory disease (PID) and sterilityUrethritis (Female)
Prevalent in men who have sex with men (MSM), painful defecation, discharge, constipation, proctitisRectal Infections
Due to oral-genital contact. Mild to severe infection. Purulent exudate. Resembles “Strep” throatGonorrhoeaic Pharyngitis
Also known as Neonatal conjunctivitis. Contracted by newborns during delivery. Redness, swelling of eye, purulent discharge. Rapidly leads to blindness if not immediately treatedOphthalmia neonatorum
Prophylactic antibiotic drops/ointment includes 1% silver nitrate, 1% tetracycline, or 0.5% erythromycinOphthalmia neonatorum
The most common STDs that cause septic neonatal conjunctivitisChlamydia and N. gonorrheae
Disseminated infection - untreated infection which has invaded bloodstream. Rarely occurs (as most strains do not multiply in blood). Also produces necrotic skin lesions on a erythematous base. Most commonly results in septic arthritisGonococcemia
MCC of septic arthritis in the sexually active age groupN. gonorrhoeae
MCC of septic arthritis in pediatric age group and those over 50 yrsStaph aureus
Collecting sample from urethral dischargeMale
Collecting sample from endocervical swabFemale
Gram stain of diagnostic value only inMale
This is not diagnostic for endocervial, throat and other specimensGram Stain
Chocolate agar with antibiotics to suppress other bacteria – normal flora with 5-10% CO2Thayer Martin Media
Patients with gonorrhea should be tested for this infection also (concurrent infection)Chlamydia trachomatis
Drug of choice for GonococcusCeftriaxone
This antibiotic should be added to treat for co-existing infection with C. trachomatisDoxycycline

Moraxella catarrhalis and Acinetobacter baumanii

Question Answer
Gram negative diplococcus. Reservoir - Upper respiratory tract normal flora. Transmission - Respiratory dropletsMoraxella catarrhalis
Treatment includes Amoxicillin + clavulanate or CefuroximeMoraxella catarrhalis
Gram negative coccobacillus. Reservoir: soil, water. Nosocomial pathogen: hospitalized pts at risk are those - In ICUs on ventilators with invasive devices (urinary catheters)Acinetobacter baumannii
Can cause pneumonia (ventilator associated pneumonia). Wound infections (high incidence in Army personnel injured in Iraq and Afghanistan)Acinetobacter baumannii

Gram Negative Rods

Question Answer
Pseudomonas, Haemophilus, Bordetella pertussis, LegionellaRespiratory tract GNB
Yersinia pestis, Pasteurella, Brucella, Francisella, BartonellaZoonotic GNB
Gram negative rod, Oxidase + *, NLF on MA. Aerobic *(non-fermentative). Produces pigments - Pyocyanin – blue-green. Grape-like / fruity aromaWidely distributed in nature - water, soil, plants. Has minimal nutritional requirements, grows - In hot tubs, sinks, vases. In hospitals – contaminates intravenous tubing, respiratory therapy equipmentPseudomonas aeruginosa
Pseudomonas aeruginosa in those with neutropenia, cystic fibrosis and immunocompromised patientsOpportunistic
Major cause of Nosocomial infectionsPseudomonas aeruginosa
Immunocompromised hospitalized patients on broad-spectrum antibiotics. Burn wounds / surgical wounds. Ventilator-associated pneumonia (VAP)Pseudomonas aeruginosa
Virulence factors include Alginate capsule, Exotoxin A, Pyocyanin, Phospholipase C and Endotoxin (LPS)Pseudomonas aeruginosa
Skin & soft tissue infections include hot tub folliculitis, Cellulitis, abcesses and infect burn wounds/surgical woundsPseudomonas aeruginosa
Otitis externa “swimmer’s ear”, necrotizing otitis externa and OsteochondritisPseudomonas aeruginosa
Pulmonary infections include Ventilator-Associated pneumonia (VAP) and patients with COPDPseudomonas aeruginosa
Burn wound/surgical wound infections (presents with green color discharge or green pus)Pseudomonas aeruginosa
UTI in catheterized patientsPseudomonas aeruginosa
Uncommon cause of endocarditis that is associated with IV drug abusers. Commonly involves the tricuspid valvePseudomonas aeruginosa
Septicemia and Ecthyma gangrenosumPseudomonas aeruginosa
Rare but characteristic of Pseudomonas sepsis hemorrhagic pustule with surrounding erythema necrotic ulcer (black center)Ecthyma gangrenosum
Positive oxidase test, blue-green pigmentation with a fruity smellLab Diagnosis
Pseudomonas aeruginosa altered porin proteins, beta-lactamases multi-drug efflux pumpsDrug Resistance Mechanisms
Treatment includes Piperacillin + Tobramycin, Piperacillin + Tazobactam, and CeftazidimePseudomonas aeruginosa
Septicemia, pneumonia in immunocompromised patients previously exposed to broad-spectrum antimicrobial therapyStenotrophomonas maltophila


Question Answer
Pleomorphic GNB with long filamentsHaemophilus
Typeable Haemophilus influenzae have thisCapsule
PRP (polyribitol phosphate) capsuleHaemophilus influenzae Type b (Hib)
Meningitis, Epiglottitis and Cellulitis are caused byTyped Haemophilus influenzae
Otitis media, Sinusitis and BronchopneumoniaNon-Typeable Haemophilus influenzae (NTHi)
Pleomorphic GNB. Fastidious requiring Hemin (factor X) and NAD (factor V) for growth. Can grow on chocolate agarHaemophilus influenzae Type b (Hib)
Vaccine for this is composed for subunit of the capsleHaemophilus influenzae Type b (Hib)
Haemophilus influenzae Type b (Hib) can be grown on blood agar but requires the presence ofStaph aureus
Otitis media, Sinusitis, Bronchitis, and Pneumonia is caused byNon-Typeable Haemophilus influenzae (NTHi)
Meningitis seen in unvaccinated childrenH.influenzae type b
Seen in unvaccinated toddlers. Obstruction of airway due to swelling of epiglottis. Accompanied with pharyngitis, fever, difficulty breathingEpiglottitis
Treatment for H. Influenzae meningitisCeftriaxone or cefotaxime
Treatment for H. Influenzae sinusitis and otitis mediaAmpicillin
Given at 6 months; booster at 15 months; 95% effective. Polyribitol capsule conjugated with proteinHaemophilus influenzae Type b (Hib) Vaccine
Acute purulent conjunctivitisHaemophilus aegyptius
Genital ulcers – Soft, painful ulcer. Slow to heal without treatmentChancroid
Chancroid is cause byHaemophilus ducreyi