Micro / Bacteriology 📚 Flashcards
Cases
Case No. (1)
18 day-old female was brought to the ER by her mother with the initial complain of bouts of coughing.The mother reported that she spits up more than usual and sometimes vomit and had episodes of tachypnea.
Her pulse was 168 per min respiratory rate 32 per min
O2 saturation was 92%.
She had marked lymphocytosis.
2 days later the her RR exceeded 100 per min and O2 saturation was less than 80% during coughing episodes.
She was transfered to pediatric ICU, where she was supported and discharged after 10 week hospital stay.
1⃣ What is your diagnosis?
2⃣ Mention the clues aided you in reaching this diagnosis?
3⃣ How can you confirm it?
4⃣ What are the virulence factors of this organism? (Mention the role of each).
5⃣ How is this disease treated?
6⃣ How is it prevented?
Answers
📝Answer for Case No. 1
1⃣ Whooping cough caused by Bordetella pertussis
2⃣ Clues: bouts of coughing, spitting, vomiting and lymphocytosis
3⃣ Nasopharyngeal swab is taken and allow for growth in bordet-Gengou ager (selective Media for Bordetella pertussis ) or charcoal blood ager ( give characteristic Mercury droplets appearance)
fluorescent-antibody staining of the nasopharyngeal specimens or Polymerase chain reaction (PCR) can be used to be used for diagnosis
4⃣ Virulence factors;
(1) Pili: contain protein know as filamentous hemagglutinin that mediate attachment of the organism to the cilia of the epithelial cells of the upper respiratory tract
(2) pertussis toxin: Cause ADP-ribosylation—to the inhibitory subunit of the G protein complex that result in:- A/ edema: inhibitions of Gi protein cause prolonged stimulation of adenylate cyclase and a consequent rise in cAMP causing edema.
B/ lymphocytosis: ADP- ribosylation of the Gi protein causes inhibition of signal transduction by chemokine receptors, resulting in a failure of lymphocytes to enter lymphoid tissue (spleen and lymph nodes) so their level increase in the blood causing lymphocytosis.
(3) Tracheal Cytotoxin: induce nitric oxide, which kills the ciliated epithelial cells of the respiratory tract
(4) Adenylate cyclase: synthesized and exported by the bacteria, when taken up by phagocytic cells can inhibit their bactericidal activity.
5⃣ Treatment:
1/ Supportive care (e.g., oxygen therapy and suction of mucus) during the paroxysmal stage
2/ antibiotics: Macrolides ( Azithromycin or erythromycin) is very effective during the early stages of the disease, their effectiveness deceased during “prolonged cough” stage because the toxins have already damaged the respiratory mucosa.
6⃣ Prevention;
(1) vaccination via acellular pertussis vaccine
(2) Azithromycin is useful in prevention of disease in exposed, unimmunized individuals
Case No. (2)
54 yrs old female was transferred from the hospital ward to the ICU for respiratory support because of worsening dysnea that didn’t respond to common medications.
CT scan was later done and showed irregular consolidations with interspersed lucent areas in both lungs.
Sputum was sent for culture.
1⃣ What culture media do you recommend and what do you expect to find?
2⃣ What is the most important virulent factor in this presentation?
3⃣ How will you treat this patient?
📝 Answers for case No. 2
⏺ Diagnosis: necrotizing pneumonia caused by MRSA
⏺ Clues:
nosocomial (she was in the ward), no response to common medications, CT appearance (consolidation -pneumonia) with interspersed lucent areas (cavities)
1⃣ Cultured media: first we isolate the organism using 7-10% Nacl which is selective media for isolation of staphylococcus aureus.then we can Cultured it in
(1) Blood ager: complete zone of hemolysis is blood ager (bete Hemolytic) , colonies are moderate size, round, smooth, convex and golden in color
(2) MacConkey agar: the color of the media is changed from colorless to pink
(3) Mannitol salt agar: the color of the media is changed from red to yellow.
2⃣ Virulence factor:
Panton Valentin Leukocidin (PVL) which kill leukocytes and causes severe necrotizing pneumonia
3⃣ Treatment:
Antibiotics treatment using Vancomycin or Daptomycin
Case No. (3)
One years old boy is presented with fever for two days and sore throat with drooling of saliva, his mother is not sure about his vaccination. On examination, he looked toixc, febrile and his was crying.
1⃣ What is most likely diagnosis
2⃣ what is the causative agent ?
3⃣ How can you manage this patient
4⃣ Can you prevent this disease
📝 Answers for case No.3
1⃣ Diagnosis: Epiglotitis
2⃣ Heamophilus linfluenze type B
3⃣ Management:
Respiratory support and maintenance of airways
Antibiotic: 3th generation cephalosporin (e.g. Ceftriaxone)
4⃣ Prevention:
Vaccination via vaccine contains the capsular polysaccharide of H. influenzae type B conjugated to diphtheria toxoid
Case No. (4)
22y old female come to hospital c/o of fever , general weakness, tachycardia ,pain in different joints also she said that she had heavy menstruation last month .on examination skin lesions in hand and forearm are seen The most causative agent?
📝 answer for case No. 4
it’s Neisseria gonorrhea
This condition is called Arthritis dermatitis syndrome which characteristics by fever, skin lession and inflammation of multiple joints
Case No. (5)
25 years man is refered to Soba University hospital, the patient gives a 3 mouth history of productive cough and steady weight of 10 Kg, his sputum had initially been yellow, but of the past week he has noticed strikes of blood. He also compiles of sweating at night and sometimes he had to change his bed clothes. On examination a harsh of respiratory sounds was heard over the left apex.
1⃣ What is the most likely diagnosis ?
2⃣ How can the lab help you in diagnosis ?
3⃣ Name the five characteristic of the causative agent ?
4⃣ Mention other clinical presentation of the causative agent ?
5⃣ How you can manage this patient ?
6⃣ How you can prevent this disease ?
📝 Answer for case No. 5
1⃣ Post Primary Pulmonary Tuberculosis
2⃣
🔸Specimen: sputum
🔸Macroscopic examination: bloody sputum
🔸Microscopy: sputum for acid fast stain(red bacilli in blue background)
🔸Culture:
Lowenstein Jensen agar
Radioactive Bactic meduim
🔸Biochemical tests:
Niacin +
Catalase +
🔸PCR
3⃣
Acid fast bacilli
Obligate aerobe
Facultative intracellular
Slow grower
Catalase +, Niacin +
4⃣
🔸extra pulmonary tuberculosis
Scrofula
GIT Tb
Orophangeal TB
Renal Tb
🔸Miliary Tuberculosis
Chronic osteomylitis
Meningitis
5⃣
Do antibiotics sensitivity test to select the effective line
1st line
4 drugs are INH (Isoniazid), Rifampin,
pyrazinamide and ethambutol for 2 months
2 drugs are INH & Rifampin for 4 months
If the strain was MDR then move to the second line
2nd line drugs are ciprofloxacin,
cycloserine, amikacin, and ethionamide
6⃣
BCG vaccine
Milk pasteurization
Treatment of patients and carriers
Case No. (6)
71 year old M with hx of smoking and recent flu like illness present with fever,chill’s,productive cough, pleuratic chest pain ,and dyspnea that began 2 days ago .x ray reveals lobar consolidation of the right middle lobe most causative agent is ?
📝 answer for case No. 6
Streptococcus pneumoniae which is the most common cause of community-acquired Pneumonia
Case No. (7)
An 8 years old boy presented to the emergency department suffering from generalized edema and hypertension, investigations relieve low-complement protein and hematuea, history relieved that before 3 week he had suffered from superficial vesicles in his left arm that then broke down and purulent exudate is released and spread then it disappeared after the use of muciprin as a topical medication, based on the above scenario answer the following :-
1⃣ what is your diagnosis?
2⃣ what is the pathology of this disease ?
3⃣ what are the virulent factors that are involved ?
4⃣ How could you manage the situation ?
5⃣ what was the disease he complained of in the preceeded 3 weeks ?
6⃣ what is the causative agent for that disease ?
📝 Answer for case No. 7
1⃣ Acute Glomerulonephritis (AGN) - PostStreptococcal Disease
2⃣ exaggerated response of the immune system due to precipitation of streptococcus M protein on the glomeruli , complement system (C5a) attracts leukocytes, immune reactions and ang-AB complexes deposite , leading to the disease manifestations
3⃣ Virulence Factors : M protein
4⃣ management : ( supportive treatment : steroids to supress immunity + dialysis) NO Antibiotics administration
5⃣ previous disease : impetigo
6⃣ streptococcus group A ( pyogenes)
Case No. (8)
A 4-year old girl presents at the emergency room with bloody diarrhea, fever and vomiting. The child’s mother reports that the child has had these symptoms for about 24 hours and she has not passed any urine for about 12 hours. The child is enrolled in a day care center and the group had recently made a field trip to a MacDoodles fast food restaurant to learn about different jobs. The children had a lunch of hamburgers, fries and cola after meeting with different workers. This field trip was 4 days earlier on Friday. The child had a temperature of 39°C and showed physical signs of dehydration. Blood samples drawn showed evidence of greatly reduced kidney function and lysed red blood cells what is the most causative agent?
📝answer for case No 8
Entero-hemorrhagic O-157 H7 transmitted mainly by ingestion of undercooked meat (hamburger) and cause bloody diarrhea.
Case No. (9)
10 month year old boy bought by his mother because of difficulty in opening his mouth , constipation , on exam. he was tachycardic and hypotonia was remarkable.
1⃣ diagnosis ?
2⃣ Pathogenesis behind this disease ?
3⃣ Treatment ?
4⃣ Prevention ?
5⃣ What are the other clinical variant of this infection ?
📝 Answers for case No. 9
1⃣ diagnosis:
floppy infant syndrome (Infant botulism)
2⃣ Pathogenesis behind this disease:
Following ingestion of contaminated food containing the Cl. Botulinum the bacteria grows in the gut and produces botulinum toxin, The toxin is absorbed by the intestine and carried by the blood into peripheral nerve synapses where it blocks the release of acetylcholine at the neuromuscular junction resulting in paralysis
3⃣ Treatment:
- Respiratory support and maintenance of the airway
- give bivalent antitoxin to neutralize the toxin
- give penicillin G
4⃣ Prevention
Don’t allow neonate to eat honey
5⃣ What are the other clinical variant of this infection ?
- classical (food-born) botulism and wound botulism
Case No. (10)
5 years old child suffered from congestion of nose , mucous secretions and he complained of inability to smell well , his mother noticed a maloderous smell from his mouth , they tried traditional treatment . yet later after days reddish - blue cheek which was painful and tender on touch developed priorbitally and pain in many joints . The mother took him to the ER , history relieved that he is a sickler ( sickle cell anemia victim) , the doctor thought about certain organism and he administered some lab tests
Based on the above scenario :-
1⃣ what is he suffering from ?
2⃣ what are the noticed complications
3⃣ what is the causative agent ?
4⃣ Clues that lead you to the diagnosis
5⃣ pathogenecity behind the infection ?
6⃣ what was the lab tests prescribed by the doctor ?
7⃣ Suggest a treatment
📝 Answers for case No. 10
1⃣ diagnosis: Sinusitis
2⃣ Complication: Cellulitis, Arthritis
3⃣ Causitive agent: Haemophilus Influanzae
4⃣ Clues:
Mucous Secretion + Congestion + Inability to Smell => sinusitis
child with sickle cell anaemia + facial cellulitis ( mainly paraorbital ) following sinusitis => H.Influanzae
5⃣ Pathogenesis:
invasiveness is the main pathogenic mechanism , attachment through pilli and being protected from phagocytosis by its PRP( polyribitol phosphate) capsule ( Hi type b) , then it invade deeper tissues and enter the blood stream ( bacteremia) ,seeking many organs with many systemic manifestations, causing cellulitis and arthritis as here
6⃣ Lad diagnosis:
Specimen : skin swab
smear : G-ve coccobacilli capsulated and pilliated
culture : choclate blood agar ( X;hematin , V;NAD , IsoVitalex , lysed or heated blood; no inhibitory fatty acids) => smooth greyish colonies
biochemical tests :
catalase :+ve
oxidase : +ve
Serology :
slide or latex agglutination for capsular polysaccharides
7⃣ Treatment: amoxicillin-clavullonic acid / Co-trimoxazole
🔻N.B : Sickle cell anaemia => autosplenectomy ( and as the spleen disposes from capsulated organisms , sicklers and splenectomized have higher chance of infections by capsulated organisms - S.Pneumoniae, H.influanzae)
Case No. (11)
A 45-year-old man presents to the emergency room after stepping on a nail resulting in a puncture wound on his right foot. He was given a tetanus booster and he left against medical advice refusing antibiotics. Two days later, he returned to the emergency room for increasing pain in his right foot. Physical exam reveals dark purple and black discoloration of the right sole with multiple ruptured bullae oozing serous drainage.
1⃣ Diagnosis ?
2⃣ Mentioned 2 chemical test to confirm your diagnosis ?
3⃣ How to management this condition ?
📝 Answers for case No. 11
1⃣ Diagnosis : gas gangrene
2⃣ Biochemical test:
1/ The Nagler’s test:
used to differentiate Clostridium perfringens from other bacteria in the same species by using an antitoxin to the alpha toxin which prevents the hydrolysis of phospholipids on the side of the plate that contains it, but allows hydrolysis on the side without the antitoxin.
2/ litmus milk test:
if the organism is present, it clots the milk and the gas produced break the clots forming a stormy clot.
3⃣ Management:
1/Surgical debridement of the affected tissue until bleeding occur
2/ anti-toxin is given to neutralize the toxin
3/ Penicillin G or metronidazole is the antibiotic of choice.
Case No. (12)
A 58 years old homeless man is brought in to the emergency room by police. His temperature is 101.8 F rectally and he smells of cheap wine.Physical examination is remarkable for dullness to percussion, increased vocal fremitus, and decreased breath sounds and crackles on the right. Chest X-ray reveals consolidation of right upper lobe. One of the nurses notes the production of thick bloody sputum, when the man coughs.
1⃣ What is the diagnosis and causative agent?
2⃣ What is the most important virulence factor?
3⃣ What other diseases may be caused by this organism?
4⃣ What are the predisposing factors?
5⃣ How you diagnose this patient?
6⃣ What is the drug of choice?
📝 Answers for case No. 12
1⃣ Diagnosis: Typical pneumonia with hemoptysis .. Causative organism: Klebsiella Pneumoniae.
2⃣ Virulence Factor: Its large antiphagocytic capsule.
3⃣ Other Infections: Urinary tract infections (UTI), Bacteremia, meningitis, wound infections (beside nosocomial infections)
4⃣ Advanced age and alcoholism (seen in this patient) .. other predisposing factors: diabetes, chronic respiratory disease.
5⃣ Diagnosis
a .Clinical Suspision (mentioned in case -consolodation, dullness to percussion .. etc + results of X-ray)
b.Specimen: sputum (make sure that it is a sputum and saliva is not predominating).
c.Microscopy: stain sputum smear with India ink 》large capsule is demonstrated.
- Culture:
a. Blood agar: large mucoid colonies.
b. MacConkey agar: pink (lactose fermenter) very mucoid colonies (large capsule) [you can use other cultures to demonstrate lactose fermentation, like EMB]
Serology is not useful, and no need for PCR or other genetic tests.
Biochemical tests are also not needed; however if you performed them it is:
oxidase: negative.
catalse: positive.
indole: negative.
citrate: positive
urease: poorly positive.
motility test: negative
- Klebsiella is known for its resistance to antibiotics ,so drug of choice depends on the results of antibiotic sensetivity tests, however the emperical therapy consists of aminoglycosides (eg, amikacin or gentamicin) plus third generation cephalosporin (eg, cefotaxime).
Case No. (13)
A 40-year-old man presents to a local emergency room. He is currently on a medical mission in India. He reports sudden-onset nausea, vomiting, and copious amounts of watery diarrhea. His blood pressure is 93/65 mmHg and pulse is 114/min. On physical exam, he has sunken eyes, decreased skin turgor, and dry mucous membranes.
1⃣ Diagnosis ?
2⃣ What are the serotype that can cause this condition ?
3⃣ Pathogenesis ?
4⃣ Management ?
5⃣ Vaccination ?
📝 Answers for case No. 13
1⃣ Cholera
2⃣ Ogawa, Inaba, and Hikojima
3⃣ following ingestion of contaminated food or water, the bacteria reachs the intestine, it secrets the bacterial enzyme Mucinase, which dissolves the protective glycoprotein layer over the intestinal cells, then attached to the brush border of the gut cells via pilli then secrete the cholera toxin.
The toxin cause inserted into the cytosol, where it catalyzes ADP-ribosylation Gs protein causing the persistent stimulation of adenylate result in overproduction of cAMP which will activates cyclic AMP–dependent protein kinase, an enzyme that phosphorylates ion transporters in the cell membrane, resulting in the loss of water and ions from the cell.
The watery efflux enters the lumen of the gut, resulting in Massive watery diarrhea
4⃣ adequate replacement of water and electrolytes, either orally or intravenously. Glucose is added to the solution to enhance the uptake of water and electrolytes
Antibiotics aren’t necessary, but we can use tetracycline
5⃣ two vaccine;
(1) Shanchol is a killed whole cell vaccine contains bothO-1 and O-159 strains
(2) Dukoral contains killed whole cells of the O-1 strain plus recombinant cholera toxin subunit B
Case No. (14)
A newborn baby born from a mother with preexisting STI, after two weeks his eye became red with discharge from it. After few days he devel
oped cough, difficulty in breathing and pneumonia.
1⃣ What is the most likely causative organism?
2⃣ What is this type of pneumonia called?
3⃣ How you diagnose this patient?
4⃣ How would you treat him?
📝 Answers for case No.14
1⃣ Chlamydia trachomatis , biovar trachoma, any of serovars (D-K).
2⃣ Afebrile Pneumonia Syndrome (APS) -chlamydial pneumonitis-
3⃣ Diagnosis:
I- Clinical suspicion: conjunctivitis at 2nd week of birth associated with pneumonia.
II- Serologic finding of IgM titer = 1:32 or more with this clinical picture is considered diagnostic.
▪️Systematic laboratory diagnosis:
1) Specimen: respiratory secretions + (conjunctive scraping -to get the cells- as the organism is intracellular).
2) microscopy: poorly stain with gram, can stain with giemsa (purple inclusion bodies in blue cytoplasm) or iodine (brown inclusion bodies due to presence of glycogen) however it has poor sensetivity.
3) Direct cytology: Direct flourescent [species specific] or Enzyme Linked Immunoassay (EIA) [genus specific] are useful but have poor sensetivity.
4) Culture: centrifuge the inoculum then culture in McCoy cell line treated with cycloheximide and antibiotics (growth takes three days , then you can do: direct immunoflourescence , ELISA, Complement fixation to detect LPS -genus specific- or outer membrane proteins-species specific-).
5) Serology: IgM titer of 1:32 with this clinical presentation is considered diagnostic.
6) Molecular methods:
A) Nucleic acid hybridization (Nonamplified probe assay).
B) Nucleic Acid Amplification Tests (NAAT) using PCR, LCR, TMA .
Molecular methods (specifically NAAT) are highly specific and sensetive, however they are expensive .
4⃣ Treatment:
Supportive: he may need ventilator or respiratory support (the need will be assessed depending on the difficulty of breath he experiences)
Antibiotics: ORAL erythromycin for 14 days.
Case No. (15)
A 23-year-old woman presents to the emergency department with fever, chills, and watery diarrhea. Her symptoms began approximately 1 day after menstruation began. Her temperature is 102°F (38.9°C), blood pressure is 75/50 mmHg, pulse is 125/min, and respirations are 20/min. Physical examination is notable for a diffuse erythematous rash and desquamation of the palms and soles.
1⃣ Diagnosis ?
2⃣ What is the Pathogenesis behind this condition ?
3⃣ Mention the most probable causative agent of this condition ?
4⃣ How to manage this condition ?
5⃣ Mention another causative agent ? How to differentiate between it and the agent in question number 2 ?
📝 Answers for case No 15
1⃣ Toxic Shock Syndrome
2⃣ Staphylococcus aureus is found in the vagina of approximately 5% of women and can over-grow in the presence of a blood-soaked tampon vaginal tampons, the bacteria produce toxin calld TSST-1 which is super antigen, causes toxic shock by stimulating the release of large amounts of IL-1, IL-2, and TNF These cytokines will increase the permeability of the cell wall and cause vasodilation of the blood vessel
3⃣ Staphylococcus aureus
4⃣ Management:
1) removal of the cause (in this case most probably vaginal tampon)
2) Correction of the shock by giving I.V fluids, adrenaline, antibodies against the TSST
3) Give antibiotics (vancomycin)
5⃣ Streptococcus pyogenes
We can differentiate between S. Aureus and S. Pyogenes by using catalase test, S. Aureus is catalase +ve while S. Pyogenes is catalase -ve
