Block 2: Gram Negative Bacteria - Diagnosis, Tx, & Prevention Flashcards
In terms of diagnosis for Legionnaires Disease, what are the 3 staining techniques?
And which is best?
- Gram negative but poorly staining
Gram stain of sputum = neutrophils, no GNB
- DFA (direct fluorescent antibody) staining of specimens
3. Dieterle silver-stain - visualized best with this method
What is the Tx for Burkholderia cepacia?
TMP-SMX
What additional test could be used in the diagnosis of N. meningitidis/M**enin**Gococcus?
A sugar utilization test:
(increased) protein
(decreased) sugar
Breaks down Maltose and Glucose
The Hib vaccine is highly effective in preventing its disease. What is the vaccine composed of?
It is a polyribitol capsule conjugated with protein
What is the Tx for Pertussis?
Newer Macrolides
(clarithromycin, azithromycin)
Tx for H. influenza?
- For encapsulated/typeable strains causing invasive infections:
Ceftriaxone or Cefotaxime
- For non-encapsulated/non-typeable strains causing otitis media and sinusitis:
Ampicillin, Cefuroxime (2nd gen cephalosporins)
Amoxicillin-Clavulanate combo
*Non-typeable can be commonly resistant to ampicillin, due to beta-lactamase production
How do you treat N. meningitidis?
Don’t start with Ampicillin/Penicillin, wait for AST report to confirm susceptibility
But since many strains of it are resistant to them, add:
Cefotaxime – empirical therapy for neonates and young infants
Ceftriaxone – empirical therapy for other age groups
•Note: once AST report is received and the strain shows susceptibility to penicillin/ampicillin then use this and stop empirical drugs
- What test can be used to diagnose H. influenza - meningitis? (which test)
- Can you confirm this with a culture?
- CSF Gram stain
GN coccobacilli and numerous PMN’s/neutrophils will be seen on stain.
- Yes, on chocolate agar ( will have Factor X and V)
Pseudomonas aeruginosa can be intially treated with_______________, if multi drug-restance is not apparent.
Anti-pseudomonal beta-lactams:
–Extended spectrum penicillins
ex. Piperacillin,and to a lesser extent, Ticarcillin and Carbenicillin
OR
–3rd generation cephalosporin – Ceftazidime
Let’s say someone isn’t affected by N. meningitidis. What should be administered has a future Tx/Prevention?
•Conjugate meningococcal vaccine (MCV4)
- Contains capsular polysaccharides* from A, C, Y & W-135 serogroups
- CDC recommends 11-12 year olds be vaccinated and a booster dose at 16 years*
•New vaccine in US for serogroup B approved by FDA
Ages 10 through 25 years of age
Besides staining, what other ways can be used to diagnose Legionnaire’s Disease?
Culture – BCYE (buffered charcoal yeast extract) -w/ iron and L-cysteine
Urine Antigen Detction - Detects only one serotype of Legionella – the most common – if another serotype is causing the disease then a negative test is misleading
Macrolides, Azithromycin and Clarithromycin can be used to treat which bacterial strain; that also causes a milder form of illness known as Pontiac Fever?
Legionella pneumophila
(Legionnaire’s Disease)
Pertussis has a developed vaccine against its strains. There are two types. What are they called and what age groups are categorized as?
–DTaP: for children 2 months through 6 years of age
♦ (5 Doses)
–Tdap: for everyone 11 years and older, including pregnant women (between 27 to 36 weeks)
What is the most reliable and rapid indicator in the diagnois of N. meningitidis?
And, what else would you see in abundance when viewing the results of this method?
Gram stain CSF
You would see many GN diplococci and PMNS (neutrophils)
What is the DOC for Gonoccocus Tx?
DOC: Ceftriaxone (intramuscular) + Azithromycin/Doxycycline
*Ceftriaxone for N.gonorrhoeae
*Azithromycin/Doxycycline for Chlamydia trachomatis (to eradicate concurrent infection)
Chlamydia trachomatis can be a common co-infection with it.
How do you prevent pertussis in a newborn baby?
***Expectant mothers - should receive Tdap vaccine during each pregnancy (at 27-36 weeks)***
- How can you diagnose N. Gonorrheae?
Note: There is a difference in technique between men and women.
- And what can be used as an overall diagnosis technique?
1.
Gram stain of specimens
–Diagnosis of genital infection in males ONLY
-Gram stain of penile discharge showing neutrophils with intracellular gram-negative diplococci is diagnostic
–No value for other specimens
Culture on Thayer Martin medium (selective)
–Chocolate agar with added antibiotics (VCNT) to suppress commensal microbiotia in specimens
–VCNT = vancomycin, colistin, nystatin and trimethoprim
–For female genital specimens – ONLY endocervical
2.
Nucleic acid amplification techniques (NAATs)
–NAATs are very sensitive, recommended for all specimens being tested for N.gonorrhoeae
What should be given to all close contacts to treat N. meningitidis?
Close contacts should be given prophylaxis. This is necessary because it was spread through respiratory droplets.
Mainly: Rifampin or Ciprofloxacin
There are two main techniques to diagnose Pertussis. What are they?
•Direct Fluorescent Antibody (DFA) test
using nasal secretions*
•_Nasopharyngeal culture_s
–Bordet-Genou medium / Regan-Lowe medium (charcoal-containing)*
How is Pseudomonas diagnosed/cultured?
There are 3 ID’s that can be used.
P. aeruginosa identified with*
–positive oxidase test
– blue-green pigmentation
–Fruity smell
If there is drug resistnance apparrent with a strain of Pseudomonas aeruginosa, what would be given in terms of antibiotics?
Due to common drug resistance – use 2-drug combinations
–Antipseudomonal beta-lactam + aminoglycoside
•eg.Piperacillin + Tobramycin
–Anti-pseudomonal beta-lactam + fluoroquinolone
–Antipseudomonal penicillin + beta-lactamase inhibitor
•eg.Piperacillin + Tazobactam
•Eg. Ticarcillin + clavulanate
What is the DOC for Hemophilus ducreyi - Chancroid STD?
Erythromycin
What are the reasons that N. meningitidis has become pencillin resistant?
The mechanism is due to:
•Production of beta-lactamases (rare)
•Production of altered PBPs (penicillin binding proteins) – emerging
- What other test can be used in the diagnosis of N. meningitidis?
- Is this method as reliable as a Gram stain CSF?
- What other bacterial pathogens causing meningitidis, could use this technique?
-
CSF Bacterial Antigen Detection Test
* -Latex agglutination test detects capsular antigen (rapid test)* - No, the Gram stain CSF is the better method
- S. pneumoniae, H.influenzae type b, N.meningitidis, Group B Streptococcus, E.coli K1
