Efficacy and Pharmacokinetic/Pharmacodynamic Parameters of Cefoxitin in Women With Acute Pyelonephritis Without Severity Symptoms Due to Extended-spectrum β-lactamase Producing Escherichia Coli
Efficacy and Pharmacokinetic/Pharmacodynamic Parameters of Cefoxitin in Women With Acute Pyelonephritis Without Severity Symptoms Due to Extended-spectrum β-lactamase Producing Escherichia Coli
Escherichia coli is the primary cause of urinary tract infections and Gram-negative
 bacteremia worldwide. Since the early years of the 21st century, E.coli has acquired a new
 mechanism of resistance to antibiotics: extended spectrum β-lactamase (ESBL), type CTX-M.
 These ESBL inactivate most β-lactams, the preferred class of antibiotics for the treatment of
 severe E.coli infections. Moreover, the strains that produce these ESBL are often resistant
 to other classes of antibiotics. Their rapid spread constitutes a major public health concern
 because of a serious risk of therapeutic impasse. Treatment options in cases of infection
 with ESBL-producing E.coli are often limited to carbapenems, a class of more recently
 developed β-lactams. Carbapenems have a very wide spectrum of activity but their
 effectiveness is threatened by the emergence of strains producing carbapenemases. The
 development of therapeutic alternatives to treat ESBL-producing E.coli infections is
 therefore essential. Cephamycins, including cefoxitin, are β-lactams marketed in the
 seventies but their use was practically abandoned when wide spectrum antibiotics became
 available. They are distinguished by the presence of an α-methoxy group in position 7 which
 interferes with the action of the extended-spectrum β-lactamase and renders it ineffective
 against cephamycins. Cefoxitin is therefore active in vitro against ESBL-producing E.coli and
 offers the advantage of a narrower antibacterial spectrum, thus reducing the selection
 pressure and the emergence of resistance. However, the in vivo activity of cefoxitin for the
 treatment of ESBL-producing E.coli infections has never been measured. Furthermore, available
 pharmacokinetic and pharmacodynamic (PK/PD) data for cefoxitin are dated and incomplete,
 which raises many questions concerning the optimal dosage regimen. We have shown in a mouse
 model of ESBL-producing E. coli CTX-M pyelonephritis that cefoxitin efficacy is comparable to
 that of carbapenems without selecting resistant mutants. Cefoxitin could thus constitute an
 alternative to carbapenems for the treatment of pyelonephritis caused by ESBL-producing
 E.coli.
Clinical Study:

 This is a prospective, multicentric, non-comparative, proof of concept study evaluating the
 efficacy of cefoxitin in women with acute ESBL-producing E. coli pyelonephritis without
 severity symptoms. This antibiotic is already commercially available and its tolerability
 profile is well known, but it has never been previously evaluated to treat this particular
 type of infection.

 The primary objective of this study is to assess the clinical and microbiological response to
 treatment with cefoxitin in women with acute pyelonephritis without severity symptoms due to
 ESBL-producing E. coli.

 The secondary objectives are:

 In women with pyelonephritis caused by ESBL-producing E.coli:

 -  Gain a better understanding of the current epidemiology of ESBL-producing E. coli
 associated with febrile UTI

 -  Assess the impact of cefoxitin use on the emergence of resistance in the colonising
 bacteria of the gastrointestinal tract in women with pyelonephritis treated with
 cefoxitin and identify the associated mechanisms

 -  Characterise the PK/PD parameters for cefoxitin in order to optimise the dosage strategy
 for that antibiotic

 -  Assess the tolerance profile of cefoxitin

 Determination of sample size, feasibility of enrolment No determination of the minimal sample
 size could be calculated in this proof of concept study but a total enrolment of 40 patients
 in the 8 participating centers seems adequate to evaluate the efficacy of cefoxitin for
 treating uncomplicated acute pyelonephritis and to study its impact on the emergence of
 resistance. Half of enrolled women will have repeated measurement of serum concentration of
 cefoxitin: 6 blood samples collected within 6 hours following the injection of one of the
 doses received between the 3rd and the last day of treatment. A security assessment by an
 independent committee will be conducted on the first five patients enrolled.

 The precise incidence of ESBL-producing E.coli acute pyelonephritis without severity symptoms
 in the 8 participating centers is unknown. At BICHAT hospital, the incidence of
 ESBL-producing E.coli in 2008 was 0.66/100 admissions (57 778 admissions/year). It was
 0.46/1000 hospitalisation days at BEAUJON in 2009 with 36.5% from urine samples. The same
 year, Saint-Louis hospital recorded 18 bacteremias secondary to infection with ESBL-producing
 E.coli with 6% originating from a UTI. Those last numbers underestimate the actual incidence
 of ESBL-producing E coli pyelonephritis at that hospital, only taking into account the UTI
 associated with bacteremias. We estimate that there are approximately 10 cases of
 ESBL-producing E.coli pyelonephritis in these centers each year.

 Outline and conduct of the study/investigations performed by the CIC As soon as the
 antibiogram is available, confirming diagnosis of an ESBL-producing E. coli and after
 verification of the inclusion criteria, information and obtention of the the written consent,
 cefoxitin (2 grams intravenous perfusion of 30 minutes every 6 hours) will be given for 10
 days. A control visit and urine culture will be performed at day 2, day 7 and at the end of
 treatment, day 10. A rectal swab will be performed at enrolment before the first dose of
 antibiotic, at the end of treatment (day 10) and at day 40. The inclusion period will be 2
 years and each patient's participation will last 40 days.

 The PK study will be performed on 20 patients enrolled at one of the 4 CIC at hospital
 Saint-Louis, BICHAT, HENRI-MONDOR and HEGP. Measurement of serum concentration of cefoxitin
 will be done on the 3rd day of treatment, or between the 9th and 12th dose of antibiotic.
 Samples will be taken as follows: t0 (immediately before beginning infusing cefoxitin); t30
 min (at the end of infusion); t45 min ; t1h ; t3h ; t6h (before the next dose) for a total of
 6 samples.

 Evaluation criteria for the primary objective Clinical and microbiological response defined
 at the end of cefoxitin treatment by the presence of the 3 following criteria: (i) afebrile
 (temperature > 36° and < 38°C), (ii) resolution of urinary symptoms present at the time of
 diagnosis: dysuria, urgency, frequency, cloudy urine, pain on urination, pelvic or lumbar
 pain (iii) sterile urine culture.

 Evaluation criteria for the secondary objective (i) Clinical and microbiological response at
 48h after beginning treatment with cefoxitin; (ii) Early relapse at day 40; (iii) PK/PD
 parameters; (iv) side effects of cefoxitin.

 Statistics, PK/PD modelling, cefoxitin dosing regimen optimisation Qualitative variables will
 be reported in percentage of the studied subjects and quantitative variables by a median.
 Comparisons will use non-parametric tests. The tests will be bilateral and use a significance
 threshold of 5%. The rate of clinical and microbiological response at the end of treatment
 with cefoxitin will be reported as a percentage with an estimate of the confidence interval
 (CI) of 95% (using a binomial distribution). PK analysis will be conducted using a population
 approach and average PK parameters for cefoxitin will be estimated as well as interpatient
 variability. The PK population analysis will examine different demographic and clinical
 covariables in order to weigh their influence on PK/PD parameters; the studied covariables
 will be: age, weight, BMI, blood pressure and creatinine clearance. In order to study the
 relationship between pharmacokinetics and clinical response at H48 and at the end of
 treatment as well as at J40±5, the patients' PK parameters will be compared using the
 Wilcoxon and Mann-Whitney non-parametric tests.

 ESBL-producing E.coli strains responsible for pyelonephritis in women: typing and
 identification of subtype

 ESBL-producing strains will be screened with the synergy method, using a disk containing a
 3rd generation cephalosporin, like cefotaxime, and another disk containing a β-lactamase
 inhibitor, clavulanic acid, according to the recommendations of the competent authorities of
 antibiogram. The isolated strains will then be analysed further on three main aspects: (i)
 the phylogenetic group will be determined by multiplex PCR (ii) the strains' sequence-typing
 will be done using Multiple Sequence Typing (iii) the presence of 46 genes associated with
 extra-intestinal virulence factors will be identified through multiplex PCR.

 The determination of ESBL type will also be done by PCR.

 Detection of cefoxitin resistant strains colonising the gastrointestinal tract of women with
 pyelonephritis before treatment with cefoxitin ; emergence of resistance under treatment and
 determination of associated mechanisms of resistance to cefoxitin

 Screening for enterobacteriaceae with reduced-sensitivity to cefoxitin will be done by
 plating a rectal swab (or a stool sample) on DRIGALSKI media containing 10 mg/l of cefoxitin.
 Acquired resistance mechanisms in species normally sensitive to cefoxitin (E. coli,
 Klebsiella spp.) will be characterised: hyperproduction of Amp C in E. coli, hyperexpression
 of efflux pumps and changes in purines in E. coli et K. pneumoniae. If comparing strains is
 necessary, it will be done using ERIC2 PCR as previously described in literature.

 Ethical aspects

 The research protocol will be presented to the ethics committee, once consent from the
 promoter is obtained (with proof of the required insurance and payment of fees). The opinion
 of the committee will be included in a form delivered by the promoter to the competent
 authorities before beginning the study. All enrolled patients will be required to sign an
 informed consent before any investigation or treatment is performed. The consent forms will
 be kept for 30 years by the CIC. Patients will be informed of the results after completion of
 the study.

 Expected public health impact of study

 The expected benefits of using cefoxitin in women with uncomplicated acute ESBL-producing
 E.coli pyelonephritis are (i) an clinical and microbiological effectiveness similar to that
 of carbapenems;(ii) a decrease in the selection pressure on bacteria colonising the
 gastrointestinal tract, thus contributing to prevent the emergence of carbapenemase-producing
 Enterobacteriaceae (iii) a decrease in drug-associated cost.
Inclusion Criteria:

 -  Inclusion Criteria: Acute pyelonephritis without severity symptoms with a positive
 urine culture for ESBL-producing E. coli (cefoxitin-sensitive); antibiotic treatment
 should have been prescribed before inclusion for the empirical treatment of
 pyelonephritis, providing it is not active in vitro against ESBL-producing E. coli
 strain.

 -  Presenting at least a functional sign of urinary infection (dysuria, cloudy urine,
 pain on urination, pelvic or lumbar pain)

 -  Temperature >38 ° or < 36° during the infectious episode

 -  Imaging of the urinary ways realized within (echography) 72 hours preceding the
 inclusion.

 Exclusion Criteria:

 -  Pregnant women

 -  β-lactam allergy;

 -  antimicrobial therapy active in vitro against ESBL-producing E.coli pyelonephritis
 instituted prior to enrolment;

 -  life expectancy <30 days;

 -  creatinine clearance <30 ml/min;

 -  patient under guardianship or without healthcare coverage.

 -  Sign of sepsis severe or septic shock

 -  Major cognitive confusions

 -  Patients having refused to give her consent form in writing

 -  Not membership in a national insurance scheme or in the Universal Health Coverage
 (CMU).