Micro 6: Examples of Bacteria Flashcards
Case 1: A 24 y/o female has sexual intercourse with her fiancé. She usually urinates right after sex, but is too tired and goes to sleep instead. About 24-36 hours later she experiences dysuria (painful urination), urinary frequency and malodorous urine. She goes to her PCP and gives a urine sample which shows a lot of WBCs and grows Escherichia coli. She is placed on Ciprofloxacin for treatment.
Case 1: A 24 y/o female has sexual intercourse with her fiancé. She usually urinates right after sex, but is too tired and goes to sleep instead. About 24-36 hours later she experiences dysuria, urinary frequency and malodorous urine. She goes to her PCP and gives a urine sample which shows a lot of WBCs and grows Escherichia coli. She is placed on Ciprofloxacin for treatment.
Where did the E. coli come from?
Her GI tract. E. Coli is the second most common normal flora in the GI
How did the E. coli reach her urinary tract and
bladder?
Translocation to the urinary tract and entered the bladder through the urethra by swimming because uropathogenic E. Coli (UPEC) are motile
Would it be unusual to detect some E. coli in her urine?
No, the diagnosis of a UTI is based not the simple presence of flora but the elevated NUMBER.
Did it make a difference that she did not urinate after sex?
Yes, it flushes the area
Is there a downside to treating with Cipro?
she could get a yeast infection and gram negative rods like E. Coli can develop multi-drug resistance (mechanism: efflux pump)
C
What are some possible side-effects of Cipro (and Fluoroquinolones in general)
spontaneous tendon rupture (like Achilles tendon) and spontaneous retinal detachment. These drugs should be used sparingly because of these side effects and the potential for multi-drug resistance to develop
What is cystitis?
Cystitis is the result of the ascension of normal flora bacteria from the urethra to the bladder. Because the urethra is shorter in women and near the vagina and anus, UTIs are more common in women
What bacteria are the major causes of UTIs in women?
E. coli cause 90% of UTIs in women, but Klebsiella, Proteus, Enterococci, and Staph saprophyticus also cause UTIs.
UTIs keep slutty sorority pledges engaged
T or F. In elderly men and women, bacteriuria occurs more equally.
T. NOT UTIs, just the presence of bacteria
What are some common symptoms of bacteriuria?
pain while urinating (dysuria), frequent but low volume urination, suprapubic pain, and blood in the urine (hematuria). Most patients are afebrile
What does febrile mean?
showing a fever
What is pyelonephritis?
it basically means that the bacteria have made their way to the kidney
What should you suspect is a patient presenting with symptoms of a UTI are febrile?
if febrile, an upper UTI (pyelonephritis) should be considered.
T or F. The bladder has normal flora.
F. The bladder is normally sterile
In WOMEN, what density of bacteria per ml is needed to diagnose UTI?
greater than 10^5/ml
In MEN, what density of bacteria per ml is needed to diagnose UTI?
greater than 10^3/ml
What are two alternatives for UTI treatment?
Cipro is the go-to but resistance is rising. an alternative is Cotrimoxazole (Trimethoprim-Sulfamethoxazole) OR third-generation cephalosporins
When you see a UTI what should your first thought be in terms of bacteria?
E. Coli BUT Staph saprophyticus (if its gram-positive) is common!!
What are some characteristics of uropathogenic E. Coli (UPEC)?
- they are facultative gram negative rods
- they grow aerobically and ferment lactose (i.e. positive on an EMP plate)
- found normally in the gut GI
What can uropathogenic E. Coli (UPEC) do in relation to nitrate? Why is this important?
convert it to nitrite. This is important because urine dipstick can detect the presence/ratio of nitrate to nitrite as a potential diagnosing factor
T or F. Only E. Coli that pick up a PAI are going to cause disease
T. Symptom presentation depends on what kinds of virulence factors are picked up
What kinds of virulence factors do UPEC bugs have?
- Flagella that allow for movement
- Type 1 fimbriae mediate attachment in lower UTI-bladder- (regulated by phase variation)
- P fimbriae mediate attachment in upper- kidney and ureter- UTI (receptor is same as P blood group antigen)
Case 2
• A 70 y/o female presents to the ED with shortness of breath and wheezing. She has been hospitalized 5 times in the last 2 years with similar presentations. PMH includes COPD. She smokes 2 ppd and has for 50 years. Admission vitals: T 98.6°F, BP 120/76, HR 100, RR 30, O2 saturation 85% on RA. Her labs are unremarkable and chest x ray was clear.
• She is admitted and placed on oxygen by nasal cannula and nebulizer treatments for a COPD exacerbation, however she soon develops worsening respiratory failure and has to be intubated and placed on a ventilator. Her oxygenation initially improves over the next few days.
On day 5 of hospitalization, she develops increased O2 requirements, thick tracheal secretions, and a fever to 102°F. Labs show a WBC count of 15,000. CXR shows infiltrates. She is started on Vancomycin but does not improve.
- A sputum sample is sent to the lab. You are notified that there is growth on the agar plate, so you go down to look at it. You notice that it has a fruity odor. Here is what the plate looks like:
- Sputum culture grows Pseudomonas aeruginosa.
Case 2
• A 70 y/o female presents to the ED with shortness of breath and wheezing. She has been hospitalized 5 times in the last 2 years with similar presentations. PMH includes COPD. She smokes 2 ppd and has for 50 years. Admission vitals: T 98.6°F, BP 120/76, HR 100, RR 30, O2 saturation 85% on RA. Her labs are unremarkable and chest x ray was clear.
• She is admitted and placed on oxygen by nasal cannula and nebulizer treatments for a COPD exacerbation, however she soon develops worsening respiratory failure and has to be intubated and placed on a ventilator. Her oxygenation initially improves over the next few days.
On day 5 of hospitalization, she develops increased O2 requirements, thick tracheal secretions, and a fever to 102°F. Labs show a WBC count of 15,000. CXR shows infiltrates. She is started on Vancomycin but does not improve.
- A sputum sample is sent to the lab. You are notified that there is growth on the agar plate, so you go down to look at it. You notice that it has a fruity odor. Here is what the plate looks like:
- Sputum culture grows Pseudomonas aeruginosa.
What is the normal WBC count?
~3000-8000
What is the normal respiratory rate (RR)?
12-16. RR is the breaths taken in a minute
In general terms, what type of infection is this?
i?
opportunistic, nosocomial
How would you know this is a good sputum sample and not just saliva?
FYI: sputum is a mixture of saliva and mucus coughed up from the respiratory tract, typically as a result of infection or other disease and often examined microscopically to aid medical diagnosis.
you want to see few epithelial cells from saliva and more PMNs as a sign of infection
Nosocomial pneumonias are most often caused by G- rods or Staph. How might Pseudomonas (a G- rod) be distinguished from E. coli?
lactose fermentation (pseudomonas does not!!), oxidase positive vs negative
Why was the patient immediately started on Vancomycin? Why didn’t she improve?
Vancomycin was administered assuming they were treating the Staph (a gram positive strain- and a very common cause of nosocomial infection- so this isn’t the worst assumption but wrong here).
So she didn’t improve because Vanco doesn’t cover gram-neg (which it probably will), or anaerobes
T or F. Nosocomial pneumonia (aka HAI pneumonia) is the leading cause of death among hospital- acquired infections.
T. The greatest risk for infection occurs when the patient is placed on a ventilator. Infection occurs through micro-aspiration of oropharyngeal tract or GI tract bacteria, or from the introduction of bacteria from the hospital setting.
What are the most common pathogens that cause Nosocomial pneumonia (aka HAI pneumonia)?
The most common pathogens are Gram-negative rods (E. coli, Klebsiella, Enterobacter, Ps. aeruginosa, or Acinetobacter) and Gram-positive cocci (Staph aureus and Streptococci).
Two MOST common are: Staph. aureus and Ps. aeruginosa
Multidrug resistance is common among isolates, which is typical of HAI infections.
What are some common symptoms of Nosocomial pneumonia (aka HAI pneumonia)?
May be characterized by a patient that comes in and is placed on a ventilator, gets better, and then gets worse and develops more symptoms such as fever.
Symptoms include fever, purulent sputum, and decline in oxygenation, cough if not on ventilator. Infiltrates will be seen on lung x-ray.
What is the appropriate treatment for Nosocomial pneumonia (aka HAI pneumonia)??
Treatment starts with empiric therapy (like Vanco?) to cover most possible organisms but should be narrowed when a definitive diagnosis is made.
However, nosocomial pneumonias can be polymicrobial requiring broad spectrum coverage.
What are some characteristics of Psuedomonas aeruginosa?
- aerobic, gram-negative rod
- releases a fruity odor
- Produces pyocyanin (blue) and fluorescin (yellow) to produce blue-green color
- Some strains produce a slime layer commonly seen in CF patients
Is Pe. aeruginosa ever found normally in the body? If so, where?
Yes, in 10% of the population it is found in the GI tract.
Most it is mostly found in the environment- e.g. soil, water, vegetation
T or F. Pse. aeruginosa is a frank pathogen
F. it is opportunistic
Where do Pse. aeruginosa infections usually occur in the body?
They can infect a wide range of places including pulmonary, urinary, and soft tissue sites
The vast majority of Pse. aeruginosa infections impact what types of patients?
burn victims, HAI infections, and CF patients
What kinds of antibiotic are currently used in treating Pse. aeruginosa infections?
3rd and 4th generation cephalosporins, carbapenems, some beta- lactams with beta lactamase inhibitors, and newer aminoglycosides are used in treatment
What is an antibiogram?
A machine at hospitals that log the effectiveness of certain antibiotics to certain bacteria over a time period (say in the past year)
Case 3
• A 49 y/o male presents to the ED with cough and shortness of breath x 1 week’s duration and a one-day history of severe headache and vomiting. His spouse reports that he has been acting funny over the last 24 hours, and what actually brought them in was she witnessed him having what she thinks was a seizure earlier that day. He has been having fevers up to 102°F, rigors, and night sweats for the past 5 days as well.
• PMH: splenectomy after splenic injury from car accident 10 years ago. Has not seen a primary care provider ever.
Has never received any vaccinations.
• Social history: smokes 1 ppd, drinks a 6 pack of beer every 1- 2 days.
Vital signs: T 101.6oF, BP 90/60, HR 125, RR 28, O2 saturation 88% on RA. Patient appears toxic. Eye exam is abnormal.
• Antibiotics (Vancomycin and Ceftriaxone) plus dexamethasone (steroid) are administered for suspected bacterial meningitis.
• Head CT is done immediately. No acute abnormalities are found.
• Lumbar puncture is then done. Sample Gram stains of the CSF and diagnosis is made as Streptococcus pneumoniae meningitis
• The doctor discontinues the Vancomycin but continues the Ceftriaxone and Dexamethasone.
• However, the patient’s condition deteriorates even further over the next 48 hours and he dies.
Case 3
• A 49 y/o male presents to the ED with cough and shortness of breath x 1 week’s duration and a one-day history of severe headache and vomiting. His spouse reports that he has been acting funny over the last 24 hours, and what actually brought them in was she witnessed him having what she thinks was a seizure earlier that day. He has been having fevers up to 102°F, rigors, and night sweats for the past 5 days as well.
• PMH: splenectomy after splenic injury from car accident 10 years ago. Has not seen a primary care provider ever.
Has never received any vaccinations.
• Social history: smokes 1 ppd, drinks a 6 pack of beer every 1- 2 days.
Vital signs: T 101.6oF, BP 90/60, HR 125, RR 28, O2 saturation 88% on RA. Patient appears toxic. Eye exam is abnormal.
• Antibiotics (Vancomycin and Ceftriaxone) plus dexamethasone (steroid) are administered for suspected bacterial meningitis.
• Head CT is done immediately. No acute abnormalities are found.
• Lumbar puncture is then done. Sample Gram stains of the CSF and diagnosis is made as Streptococcus pneumoniae meningitis
- The doctor discontinues the Vancomycin but continues the Ceftriaxone and Dexamethasone.
- However, the patient’s condition deteriorates even further over the next 48 hours and he dies.
What feature of the Gram stain distinguishes S. pneumoniae from other streptococci?
diplococci (all other streps are chains) and they have a characteristic ‘lancid’ shape where their ends are pointed
Why was the vancomycin dropped? Did that likely cause the patient’s death?
The doctor assumed that the Strep. peumn was susceptible to ceftriaxone, as to has been for years in practice. ONLY RECENTLY, has resistance been developed
You can no longer assume that Strep. pen meningitis are susceptible to third generation cephalosporins
The recommendation is to continue the Vanco and Ceftrixaone until susceptibility testing returns
If not, what is a possible reason the patient died?
the lack of a spleen makes a patient more susceptible to infection from bacteria with CAPSULES such as Strep. pneumo
Was there anything significant in his history that could have contributed to this severe infection?
– If so, which virulence factor was responsible?
the lack of a spleen makes a patient more susceptible to infection from bacteria with CAPSULES such as Strep. pneumo
Can you think of a way this infection might have been prevented?
Vaccination is needed with a splenectomy
