Casciaro, R.

Cirilli, N.

D'Aprile, A.

Gagliardini, R.

Gioffrè, F.

Manno, G.

Melioli, G.

Mentasti, M.

Morelli, P.

Scuteri, D.

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5. Microbiology S35
135 Pseudomonas aeruginosa (PA) resistant to colistin (CL) in Italian
cystic ﬁbrosis (CF) patients
G. Manno1, P. Morelli1, M. Mentasti1, R. Casciaro1, N. Cirilli2, R. Gagliardini2,
A. D’Aprile3, F. Gioffre`4, D. Scuteri4, G. Melioli1. 1G.Gaslini Institute, Genova,
Italy; 2CF Centre, Ancona, Italy; 3CF Centre, Cerignola, Italy; 4CF Centre,
Soverato, Italy
Background: CL has emerged as a relevant therapeutic option for the treatment of
PA pulmonary infection in CF. The development of resistance to this agent under
selective pressure is not unexpected, even if it may occur at lower extend. Objective:
Monitoring the susceptibility to CL of a collection of PA from Italian CF pts.
Methods: 295 PA strains (151 non-mucoid, 113 mucoid and 31 SCV) from 178
pts from 4 Italian CF Centres, were tested by CLSI disk diffusion method for 12
antipseudomonal drugs and CL using a 10 mcg disk. Isolates with resistance to CL
disk were re-tested by Etest in MH agar, after at least 10 repeated sub-culture in
blood agar. The genetic relatedness of all isolates was determined by BOX-PCR.
Results: Four PA isolates (1 mucoid, 1 non-mucoid and 2 SCV) from 4 patients
showed resistance to CL by disk diffusion and conﬁrmed by Etest. The resistance
level was high, with The MIC ranging from 12 to 32 mcg/ml. The 2 SCV strains
were multi-drug-resistant, while the mucoid isolate was susceptible to the other anti-
pseudomonal drugs tested. The CL-resistant PA isolates showed different genetic
proﬁles by BOX-PCR. 3/4 patients chronically colonized by CL-resistant PA had
several previous antibiotic treatment with aerosolized CL.
Conclusions: This is the ﬁrst description of PA CL-resistance in Italian CF patients.
Although in very low percentage (2.2%) this emergence need concern in the
extensive and prolonged use of this important therapeutic option. Moreover, in
the CF microbiology workout, seems to be mandatory the CL (or polimixin B)
routinely testing in all PA isolates.
Supported by: Italian Cystic Fibrosis Foundation.
136 Evolution of antibiotic resistance in Pseudomonas aeruginosa
isolates from cystic ﬁbrosis patients: results from a longitudinal
study
S. Campana1, S. Tekle1, N. Ravenni1, C. Braggion1, G. Taccetti1. 1Cystic Fibrosis
Center, University of Florence, Florence, Italy
Pulmonary infection is the main cause of morbidity and mortality in cystic ﬁbrosis
(CF) patients. Patients who are subject to P. aeruginosa are treated with parenteral
combination antibiotic therapy on a routine basis (three times per year) and although
this approach has notably improved the quality of life and longevity of CF patients,
it favors the selection of highly resistant strains. We evaluated the percentage of
resistance to commonly used antimicrobials against P. aeruginosa isolates from
200 CF patients referred to the Tuscan Regional Cystic Fibrosis Center between
1996–2006. The chemosensitivity proﬁle was created by including P. aeruginosa
strains isolated every 6 months from each CF patient, for a total of 1715 strains.
The table illustrates the prevalence of resistance to the principal antimicrobials used
during the observation period. These data demonstrate a dramatic increase in the
percentage of P. aeruginosa strains resistant to the main classes of antimicrobial
agents. This increased resistance of P. aeruginosa strains emphasizes the urgent
need to optimize therapeutic protocols for the treatment of infections due to this
important opportunistic pathogen in order to limit the selection and occurrence of
highly resistant strains to the currently used antimicrobial agents.
Percentage of resistant P. aeruginosa strains from 1996–2006
Percentage of resistant strainsa
A
nt
ib
io
ti
c
19
96
(9
3)
19
97
(9
3)
19
98
(1
08
)
19
99
(1
02
)
20
00
(1
50
)
20
01
(1
57
)
20
02
(1
63
)
20
03
(2
20
)
20
04
(2
13
)
20
05
(2
16
)
20
06
(2
00
)
MEP − − 16 17 13 10 23 22 21 21 23
IMP 14 22 25 24 23 15 25 22 24 26 24.5
CAZ 3 19 20 16 19 7 21 18 14 17 19
TIC 8 14 27 24 25 18 23 27 24 27 53
NN 11 14 19 7 13 11 23 36 26 32 27
CIP 16 14 24 12 23 16 37 32 34 33 36.5
aTotal numbers of strains are listed in parentheses after the year.
137 The sensibility of Ps. aeruginosa isolates in children with
cystic ﬁbrosis
E. Chioroglo1, S. Sciuca1, O. Turcu1. 1Pediatry, State Medical and Pharmaceutical
University, Chisinau, Moldova
Aim: to study the sensibility of Ps.aeruginosa isolates in children with cystic
ﬁbrosis (CF).
Materials and Methods: study included 13 children with CF at the age of 2−18
year with chronic Ps. aeruginosa infection. 43 probes of sputum were evaluated
microbiologically in exacerbation of bonhopulmonary disease. Antibiogram was
appreciated by method of diffusion in Muller-Hinton agar with antibiotics from
standard disks. Diagnosis was conﬁrmed in all children based on the clinical
data, positive sweat test and/or positive molecular diagnostic. DF508 mutation
was revealed in 10 children, 1 child – G542X/N1303K mutation, 2 cases –
unidentiﬁed mutation. Bronchopulmonary system affecting was characterized by
bronchiectasis in children (61.5%), infectious bronchiolitis, pulmonary ﬁbrosis,
chronic bronchitis – in all children.
Results: Ps. aeruginosa was determined in all children with chronic infection in
diagnostic concentration. Study showed high sensibility to imipenem – 95.8%,
ﬂuoroquinolones (ciproﬂoxacin – 92.6%), cephalosporin’s II−III generation (cef-
operazon – 96.3%, ceftazidim – 83.8%, ceftriaxone – 66.6%); aminoglycosides
(tobramycin – 93.5%, gentamicin – 74.4%), penicillines antipseudomonas also
presented marked sensibility to piperacillin – 86.3%, piperacillin/tazobactam –
95%. There was an evident resistance of examined isolates to ampicillin – 100%,
amoxicillin – 100%, doxycycline – 100%, cefazolin – 86.7%, cefuroxime – 90.8%,
cefotaxime – 54.3%, macrolides (clarithromycin – 100%, azithromycin – 95.5%).
Conclusions: Chronic airways colonization with Ps. aeruginosa in children with CF
manifests high sensibility in vitro to ciproﬂoxacin, cefoperazon, ceftazidime and
antipseudomonas penicillines, tobramycin, which could be recommended in the
therapeutic programs of Ps. aeruginosa infection.
138 The effect of incubation of sub-minimum inhibitory concentration
of antibiotics on strains of Pseudomonas aeruginosa (PA) in a
desiccation survival model
I. Clifton1, M. Denton2, F. M’Zali2, D. Peckham1. 1Regional Adult CF Unit,
Leeds, United Kingdom; 2Department of Microbiology, Leeds General Inﬁrmary,
Leeds, United Kingdom
Introduction: Prior to modern genetic typing methods cross-infection of PA
between patients with cystic ﬁbrosis (CF) was felt to be rare. Recently a number of
studies have been undertaken that demonstrate the presence of clonal strains of PA
infecting patients with CF. The aim of this study was to determine whether clonal
strains of PA demonstrated differences in resistance to desiccation, and whether
pre-incubation with sub-minimum inhibitory concentrations (MICs) of antibiotics
affected desiccation resistance.
Methods: Strains of PA pre-incubated with or without antibiotics were studied in a
dessication survival assay with controlled conditions of temperature and humidity.
The survival curves were modelled to a Weibull curve using least squares error
method using GraphPad Prism. Differences between curves were determined using
the F-Test. P< 0.05 was taken to be signiﬁcant.
Results: Pre-incubation with antibiotics did not have a consistent effect on the
strains of PA. All of the non-clonal strains and two of the clonal strains demon-
strated signiﬁcant reduction in desiccation resistance following pre-incubation with
tobramycin. Meropenem signiﬁcantly reduced desiccation resistance in most of the
strains and ceftazidime had the least effect on the strains studied.
Conclusions: Promoting bacterial survival through antibiotic exposure could have
important clinical consequences by potentiating the risk of cross infection between
patients with CF. Further studies are needed to investigate the impact of sub-MIC
concentrations of different antibiotics have on promoting or inhibiting patients
with CF.


Pseudomonas aeruginosa (PA) resistant to colistin (CL) in Italian cystic fibrosis (CF) patients 

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Pseudomonas aeruginosa (PA) resistant to colistin (CL) in Italian cystic fibrosis (CF) patients

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