Questions about CF

Question

Hello,

I live in Morocco and I am the mother of a 10-year-old CF child. I would like to ask some general questions related to its illness:

Regarding sputum analysis
We had analyzed the same sputum sample in 2 different establishments (private laboratory and a laboratory in a university hospital); the results of the private laboratory are positive (Pseudomonas) while those in the hospital are negative twice.
According to the private laboratory, analyzes are done in four Petri dishes containing 4 different culture media: fresh blood, ANC, cooked blood Sabouraud. The seeds that grow former are staphylococci, then the yeast, and finally Pseudomonas which generally can occur after the 4th day and incubation lasts until the 10th day.
Regarding the public laboratory, they do not exceed 48 hours since according to them the Pseudomonas is a bacterium that grows rapidly ie within 24 hours that follow their culture and they do not require incubation for 10 days.
Can you please give me your opinion on the reliability of each method?

Concerning the use of antibiotics
1. In the presence of bronchitis, can the use of the single antibiotic Augmentin (amoxicillin and clavulaic acid) for 15 days can lead to a general improvement despite the presence of Pseudomonas?
2. Can the treatment with the antibiotic Ciprofloxacin orally several times (3 times) contribute to the resistance of Pseudomonas to Ceftazidime?
3. If there is a resistance to Ceftazidime, can then a course of antibiotics (Ceftazidime and Amikacin for 21 days followed by 3 months of colomycin in aerosol) be effective?

Answer

Hello,
1 Reliability of culturing methods:
Conventionally, Pseudomonas aeruginosa grows in 24-48 hours. But because of specific CF factors, the French Society of Cystic Fibrosis recommend (since 2015) seeding 7 minimum culture media (including selective Pseudomonas aeruginosa) and incubation for 5 days minimum to allow the demonstration of slow-growing bacteria such as certain forms of P. aeruginosa.
2 In the presence of bronchitis, can the use of the single antibiotic Amoxicillin-Clavulanic acid (Augmentin) for 15 days lead to a general improvement despite the presence of Pseudomonas?
It is difficult to answer the question without bacteriological results with the sensitivity of the organisms to various antibiotics. In practice, in case of bronchitis, and in the absence of bacteriological results it is conventional to aim the seeds of the mouth and pharynx frequently responsible (eg Haemophilus influenzae or Branhamella catarrhalis) by an antibiotic such as amoxicillin- clavulanic acid (Augmentin) usually active on this organisms. The treatment can be secondarily modified if it proves to be not effective enough and if the bacteriological results show greater sensitivity to another antibiotic.

3 Can the treatment with the antibiotic Ciprofloxacin orally several times (3 times) contribute to the resistance of Pseudomonas to Ceftazidime?
Treatment with Ciprofloxacin preferentially induces resistance to Ciprofloxacin.
4- If there is resistance for Ceftazidime, can a course of antibiotics (Amikacin and Cefatzidim for 21 days followed by 3 months of colymicin in aerosol) be effective?
Yes, as other mechanisms unexplored by the antibiogram techniques may be involved (including the effect on inflammation, biofilm ...). Furthermore, a bacterial strain can be rendered resistant to Ceftazidime (Fortum) but having a low resistance which allows nevertheless the use of this antibiotic provided to the appropriate dosages. Finally, dual therapy with Amikacin provides a synergistic action that is stronger than the sum of the effects of two antibiotics.

Hoping to have answered your question and wishing you a Happy New Year 2016

Gilles RAULT, MD, Roscoff CF Center
and
Geneviève HERY-ARNAUD, Microbiology, University Hospital Brest

27.02.2016