Block III Gram (-) Bacteria

ptheodore's version from 2015-11-09 14:19

Clostridium Botulinum


Question Answer
what is the name of the toxic of Clostridium BotulinumBotulinum neurotoxin
How food borne botulism is acquired?ingestion of preformed toxin from home-canned vegetable, smoked fish, or carrot juice
How infant botulism is acquired?Ingestion of spores from honey, corn syrup or soil
How wound botulism is acquired?Wounds, or drug users
Heat labile (destroyed at 60⁰C for 10 minutes) Clostridium Botulinum Neurotoxin
Blocks release of acetylcholine at the myoneuronal junction and leads to flaccid paralysis Clostridium Botulinum Neurotoxin
Which Toxin absorbed by gut and then carried by blood to peripheral nerve synapsesBotulinum Neurotoxin
1-2 days after consuming food (preformed 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”)
Treatment for Clostridium BotulinumBotulinum antitoxin & Adequate ventilatory support
How do you prevent spore-germination of Clostridium botulinum?Maintaining food in acid pH & Storage at 4 degrees C or colder
How can you Destroy preformed toxin of Clostridium botulinum in canned foods?Heating foods at 60 degrees C to 100 degrees C for 10 minutes
Infants below 1 year is not allowed to eat honey

Clostridium Perfringens

Question Answer
Spore-forming, dbl-zone of beta-hemolysis, Nagler reaction on egg-yolk agar & Stormy clot fermentation in litmus milk medium are characteristics of which bacteriaClostridium Perfringens
Suppurative myositis & Myonecrosis (Gas gangrene)Clostridium Perfringens
Gastroenteritis (enterotoxin) of Clostridium Perferingens is caused byFood poisoning
Phospholipase C (Lecithinase), Degrades lecithin in mamallian cell membranes, Damages RBCs, WBCs, platelets, endothelial cells Alpha-toxin (from Cl. Perfringens)
Heat-labile (destroyed by heating), Disrupts ion-transport (ileum) causes watery diarrheaEnterotoxin
Specifically targets lecithin and destroys membraneAlph-toxin (Lecithinase) (Cl. Perfringens)
Disrupts tight cell junctions & Causes food poisoning with diarrheaC.perfringens Enterotoxin (CPE)
Sources of food borne illness for Cl. PerfringensBeef, poultry, gravies, pre-cooked foods
Starts 8-18 hours after ingestion of contaminated food Cl. perfringnes Food-poisoning
Lab diagnosis helps establish diagnosis for Cl. Perfringens byCulture of bacteria from stool & Detection of toxins
Fermentation of tissue carbs, lipids, amino acids → gas accumulates → crepitus (can be felt under skin) Cl. Perfringens
Testing for LecithinaseAntitoxin is bound to alpha-toxin
Double zone of hemolysisGas gangrene (Cl. Perfringens)
Drugs use to treat Cl. PerfringensClindamycin and penicillin

Neisseria Meningitis

Question Answer
MCC of meningitis in childrenNeisseria Meningitis
use maltose & glucoseNeisseria meningitidis
use only glucoseNeisseria gonorrhoeae
What is the hallmark feature of Meningococcal meningitis?petechial rash
Encapsulated gram negative diplococcus , Oxidase + catalase & Breaks down maltose & glucose Neisseria meningitidis
MOT of Neisseria meningitidisinhalation of respiratory droplets
Which age group MC affected by Neisseria Meningitidis2-18 yrs
Polysaccharide capsule, IgA protease, endotoxin (LOS) & pilli are the virulences factors for which bacteria?Meningococcus meningitis
Complement deficiency (C5-C8) & Asplenia are the risk factors for severe infection of which bacteria?Meningococcus
Outbreaks in institutions, schools, military barracks, dormitories are mostly correlated with which bacteria? Meningococcus
High fever (rapid onset), Nuchal rigidity (stiff neck), Photophobia (sensitivity to light), confusion, headache, vomitting, Petechia (purpural rash), & Rapidly fatal are the key features of which bacteriaMeningococcus Meningitis
Failure of adrenal gland function due to bleeding into gland. Bilateral adrenal hemorrhage Waterhouse-Friderichsen syndrome
Gram stain in CSF, increase proteins, decrease sugar, capsulated antigen & utilization of Maltose & glucose are characteristics features of lab diagnosis for which bacteria?Neisseria meningitidis
Treatment for Neisseria meningitidisampicillin/ Penicillin G & if resistant use Ceftriaxone/Cefotaxime
All close contacts to Neisseria Meningococcal should be given what type of prophylaxis?Rifampin or Ciproflaxin
Is there a vaccine for Neisseria meningitidisConjugate meningococcal vaccine (MCV4)
What does the Neisseria meninditidis vaccine made of ?Capsular polysaccharides

Neisseria Gonorrhoeae

Question Answer
Neisseria gonorrhoeae pili undergo?antigenic variation
reservoir for Neisseria gonorrhoeaeHuman genital tract
Causes Neisseria Gonorrhoeaea sexually transmitted disease (STD)
The IgA protease virulence factor of gonococcus is important forcolonization
The Pili virulence factor of gonococcus is important foradherence & colonization
Two major virulence factors of Gonococcus areLipooligosaccharide (LOS) & Antigenic and Phase variation
During an infection Gonococcus can evade detection by the hosts’ immune system by changing the pili it expresses. This phenomenon is calledAntigenic and Phase variation
Antigenic variation accounts forchronicity of infections
Which part of the vagina does Neisseria Gonorrhea affect?endocervix
genito-urinary tract infection in men due gonococcusUrethritis
genito-urinary tract infection in women due gonococcus infectionEndocervicitis & Pelvic inflammatory disease (PID)
MCC of septic arthritis in sexually active individuals is caused byNeisseria Gonorrhea
Ophthalmia neonatorum aka Neonatal conjunctivitis is caused byNeisseria Gonococcus
Chlamydia and N.gonorrhea are the most common STDs that causeOphthalmia neonatorum aka septic neonatal conjunctivitis
The most common cause of septic arthritis in the sexually active age groupGonococcus
The most common cause in children and adults over 50yrsStaph Aureus
How do you diagnose Gonococcus genital disease in male?urethral discharge
How do you diagnose Gonococcus genital disease in female?endocervical swab
Gram stain diagnosis of Gonococcus value only inMale patients
Patients with gonorrhea should be tested forChlamydia trachomatis infection
gram stain of Gonococcus is of diagnostic value forgenital infections (in males)
Thayer Martin media is useful for culturing which bacteria?Neisseria Gonococcus
Thayer Martin medium (CA + VCNT antibiotics) is selective for Neisseria Gonococcus
Suppress normal flora Gram positive and gram negative bacteria and fungi & Allow gonococci to growth out in large numbers Vancomycin, colistin, nystatin and trimethoprim
Gonococci a very exacting in nutritional requirements and need highly enriched mediaChocolate agar
Drug of choice to treat Neisseria GonorrheaCeftriaxone + Doxycycline
Otitis media *, Sinusitis *, Bronchitis and pneumonia (in elderly pts with COPD) are diseases of which bacteria?Moraxella Catarrrhalis
Treatment for Moraxella catarrhalisAmoxicillin + Clavulanate, Cefuroxime & TMP-SMX
Pneumonia (ventilator associated pneumonia), Wound infections (high incidence in army personnel injured in Iraq and Afghanistan) are important diseases forAcinetobacter
In the case of Gonococcus infection why do we use empirical treatment (Ceftriaxone + Doxycline) ?Use Doxycycline along with Ceftriaxone to prevent Chymedia

Respiratory Gram Negative Rods


Question Answer
Produces Pyocyanin a blue-green & has Grape-like / fruity aromaPseudomonas aeruginosa
In hot tubs, sinks, vases, in hospitals, contaminates intravenous tubing, respiratory therapy equipment Pseudomonas Aeruginosa
Immunocompromised patients, Cystic fibrosis patients and neutropenia patients are always at high risk toPseudomonas aeruginosa
constitute 10% of all nosocomial infectionsPseudomonas aeruginosa
is a leading cause of nosocomial infectionsStaph. Aureus
Immunocompromised hospitalized patients on broad-spectrum antibiotics* , Burn wounds / surgical wounds*, Ventilator-associated pneumonia (VAP) are major causes ofNosocomial infections
Which virulence factor of Pseudomonas aeruginosa where Mucoid strains cause significant respiratory tract infections in Cystic fibrosis patients?Alginate capsule
What does the exotoxin A of Pseudomonas aeruginosa do?blocks protein synthesis at EF-2
Mechanism of action of Phospholipase C in Pseudomonas aeroginosatissue damage (Breaks down lipids and lecithin)
Mechanism of action of Pyocyanin in Pseudomonas aeroginosatissue damage (catalyzes production of H2O2 and superoxide)
Otitis externa (swimmer’s ear), Malignant otitis externaPseudomonas aeruginosa
Ecthyma gangrenosumskin lesion associated with pseudomonas sepsis
P. aeruginosa identified withpositive oxidase test *, blue-green pigmentation *, Fruity smell
Drug resistance mechanisms for Pseudomonas aeruginoasAltered Porin proteins, Beta-lactamases & Multi-drug Efflux pumps
Drug of choice to treat Pseudomonas aeruginosaPiperacillin + Tobramycin/ Piperacillin + Tazobactam, Ceftazidime
is ubiquitous soil/water organismPseudomonas aeruginosa
Septicemia, pneumonia in immunocompromised patients previously exposed to broad-spectrum antimicrobial therapy causes opportunistic infectionsStenotrophomonas maltophila
Pleomorphic GNBHaemophilus
Meningitis, Epiglottitis & Cellulitis are seen in which type of Haemophilus influenzae?Tapeable -HIb (Encapsulated)
Otitis media, Sinusitis & Bronchopneumonia are seen in which type of Haemophilus influenza?Non-Tapeable-NTHi (No-capsule)
Hemin (factor X) and NAD (factor V) are nutritional growth requirements forHaemophilus influenza
Homophiles influenza grows inChocolate agar (heated blood agar)
Where can you observe Satelllite colonies?When Haemphilus influenzae growing near Staph aureus
Which encapsulated strains of Heamophilus influenza use in vaccine production? Type b → polyribitol phosphate (PRP)
Function of IgA protease virulence of Heamophilus influenzaDegrades secretory IgA facilitating colonization of upper respiratory mucosa
The most common bacterial causes of acute otitis media, sinusitis AND bacterial conjunctivitis in childhood areStreptococcus pneumoniae, Nontypable Haemophilus influenzae & Moraxella catarrhalis ( in that order)
Drug of choice for tapeable Haemophilus influenzaAmpicillin/Cefuroxime, Amoxicillin + Clavulonate
Acute purulent conjunctivitis, “pink eye"Haemophilus aegyptius
Genital ulcers – “Chancroid”, an STD Haemophilus ducreyi
Respiratory disease characterized by paroxysmal coughPertussis/Whooping cough
Pertussis vaccine for everyone 11 years and older, including pregnant womenTdap
Pertussis vaccine for children 2 months through 6 years of ageDTaP
Why then are there increasing cases & outbreaks of the Pertussis disease in the US ? Immunity in vaccinated individuals wanes over time
Gram negative coccobaccilus, strict aerobeGram negative coccobaccilus, strict aerobe
Highly infectious/contagious * & Infects ciliated respiratory epithelium Bordetella pertussis
How does Bordetella pertussis adhere to respiratory mucosa?Filamentous hemagglutinin
How does Bordetella pertussis damage respiratory mucosa?Adenylate cyclase toxin & Tracheal cytotoxin
Mechanisms of action of Adenylate cyclase toxinIncrease in cAMP which then increase respiratory secretions & impairs leukocyte chemotaxis which then inhibits phagocytosis
Mechanism of action of Tracheal cytotoxinInterferes with ciliary action, kills ciliated cells & Inhibits regeneration of damaged cells
Mechanism of action of PERTUSSIS TOXINincrease in resp. secretions
Pertussis toxin promotesLymphocytosis
Who is at high risk for pertussis aka Whooping cough?Unvaccinated babies – severe disease & Vaccinated individuals in whom immunity has waned
What appears in pharyngeal cultures of diagnosis of pertussis?Bordet-Genou medium / Regan-Lowe medium
Drug of choice for PertussisErythromycin / TMP-SMX
The primary mode of prevention of pertussisVaccination (DTaP/TDaP)
Which group should receive vaccine during 27-36 weeks?Expectant mothers
Hot-tub, air-conditioning, portable water system & cooling towers are the common sources forLegionella
MOT of LegionellaINHALATION of Aerosols (no person-to-person transmission)
Individuals over 55 yrs who smoke and drink alcohol, Elderly debilitated & Chronic lung disease, immunocompromised are high risk-group forLegionella pneumophila
Inside the phagosome, Legionella uses ..................into the cytosol to burst the phagosomal membraneDOT Type 4 secretion system (T4SS)
Facultative intracellular bacterium*, Able to infect and replicates inside macrophages * & Inhibits phagolysosome fusionLegionella
Immunity to Legionella is primarilyCell mediated
Fever, chills, headache, dry, NON-PRODUCTIVE COUGH* & Gram stain of sputum – neutrophils but no bacteriaAcute lobar pneumonia + major confusion + diarrhea
The triad can help you ID Legionnaire’s diseaseAcute lobar pneumonia, Major confusion & Diarrhea
BCYE (buffered charcoal yeast extract) & Urine Antigen detection use to diagnoseLiegionnaires disease
Drug of choice for Legionella pneumophilaMacrolide – Azithromycin, clarithromycin