Comparative efficacy of trovafloxacin in experimental endocarditis caused by ciprofloxacin-sensitive, methicillin-resistant Staphylococcus aureus

The new fluoroquinolone trovafloxacin was tested against a ciprofloxacin-sensitive, methicillin-resistant Staphylococcus aureus strain in the rabbit model of endocarditis. Trovafloxacin was more effective than vancomycin (CFU/g of vegetation, 2.65 +/- 1.87 versus 4.54 +/- 2.80 [mean +/- standard deviation]; P < 0.05) or ampicillin-sulbactam plus rifampin (4.9 +/- 1.1 CFU/g). The addition of ampicillin-sulbactam to trovafloxacin tended to reduce titers further.

Single-dose ciprofloxacin at 100 versus 250 mg for treatment of uncomplicated urinary tract infections in women

Two single-dose regimens of ciprofloxacin, 100 and 250 mg, were compared in the treatment of uncomplicated urinary tract infections in women. Cure rates 5 days after therapy did not significantly differ, being 16 of 19 (84%) with the 100-mg dose and 17 of 19 (89%) with the 250-mg dose. Ciprofloxacin was well tolerated.

Ciprofloxacin-induced hematuria

We used ciprofloxacin, a quinolone-derivative, to treat a lung infection due to Pseudomonas aeruginosa in an adult cystic fibrosis patient. On three different occasions the use of ciprofloxacin was associated with the development of an asymptomatic hematuria with red blood cell casts. The mechanism responsible for this hematuria is presently unknown, but clinicians should be aware of this potential adverse effect of ciprofloxacin.

Acinetobacter baumannii isolates from pets and horses in Switzerland: molecular characterization and clinical data

OBJECTIVES: We investigated whether Acinetobacter baumannii isolates of veterinary origin shared common molecular characteristics with those described in humans. METHODS: Nineteen A. baumannii isolates collected in pets and horses were analysed. Clonality was studied using repetitive extragenic palindromic PCR (rep-PCR) and multilocus sequence typing (MLST). PCR and DNA sequencing for various beta-lactamase, aminoglycoside-modifying enzyme, gyrA and parC, ISAba1 and IS1133, adeR and adeS of the AdeABC efflux pump, carO porin and class 1/2/3 integron genes were performed. RESULTS: Two main clones [A (n = 8) and B (n = 9)] were observed by rep-PCR. MLST indicated that clone A contained isolates of sequence type (ST) ST12 (international clone II) and clone B contained isolates of ST15 (international clone I). Two isolates of ST10 and ST20 were also noted. Seventeen isolates were resistant to gentamicin, 12 to ciprofloxacin and 3 to carbapenems. Isolates of ST12 carried bla(OXA-66), bla(ADC-25), bla(TEM-1), aacC2 and IS1133. Strains of ST15 possessed bla(OXA-69), bla(ADC-11), bla(TEM-1) and a class 1 integron carrying aacC1 and aadA1. ISAba1 was found upstream of bla(ADC) (one ST10 and one ST12) and/or bla(OXA-66) (seven ST12). Twelve isolates of different STs contained the substitutions Ser83Leu in GyrA and Ser80Leu or Glu84Lys in ParC. Significant disruptions of CarO porin and overexpressed efflux pumps were not observed. The majority of infections were hospital acquired and in animals with predisposing conditions for infection. CONCLUSIONS: STs and the molecular background of resistance observed in our collection have been frequently described in A. baumannii detected in human patients. Animals should be considered as a potential reservoir of multidrug-resistant A. baumannii.

The increase of methicillin-resistant Staphylococcus aureus (MRSA) and the presence of an unusual sequence type ST49 in slaughter pigs in Switzerland

Background: In years past, methicillin-resistant S. aureus (MRSA) has been frequently detected in pigs in Europe, North America and Asia. Recent, yet sporadic studies have revealed a low occurrence of MRSA in Switzerland. In 2009, a monitoring survey of the prevalence and genetic diversity of methicillin-resistant S. aureus (MRSA) in slaughter pigs in Switzerland was conducted using methods recommended by the EU guidelines, and using a sampling strategy evenly distributed throughout the year and representative of the Swiss slaughter pig population. Monitoring should determine if the overall prevalence of MRSA in the entire country is increasing over the years and if specific multi-resistant MRSA clones are spreading over the country.;Results: In 2009, the nasal cavities of eight out of 405 randomly selected pigs were positive for MRSA, representing a prevalence of 2.0% (95% CI 0.9-3.9). The following year, 23 out of 392 pigs were positive for MRSA [5.9% prevalence (95% CI 3.8-8.7)]. Three multilocus sequence types (ST), four spa types and two types of staphylococcal cassette chromosome mec (SCCmec) elements were detected. The most frequent genotypes were ST398 (MLST)-(spa)t034-V (SCCmec) (n = 18) and ST49-t208-V (n = 7), followed by ST398-t011-V (n = 4), ST398-t1451-V (n = 1), and ST1-t2279-IVc (n = 1). The isolates displayed resistance to beta-lactams [mecA, (31/31); blaZ, (19/31)]; tetracycline [tet(M), (31/31); tet(K), (30/31)] (n = 31); macrolides and lincosamides [erm(C) (4/31) or erm(A) (18/31)] (n = 22); tiamulin [vga(A)v (9/31) or unknown mechanism (18/31)] (n = 27); trimethoprim [dfr(G) (18/31); spectinomycin [ant(9)-Ia (19/31) or unknown mechanism (3/31)] (n = 22); streptomycin [str(19/31)]; sulphamethoxazole (7/31) and ciprofloxacin (n = 1) (mechanisms not determined).;Conclusions: This study is the first to describe the presence of MRSA ST49 in slaughter pigs, and to demonstrate a significant and nearly three-fold increase of MRSA prevalence in pigs within two years. The presence of a specific clonal lineage of MRSA from Switzerland suggests that it has been selected in Swiss pig husbandry. Effective hygiene measures should be enhanced within the entire pig production chain to suppress the spread of these pathogens into the community.

Characterisation and clinical features of Enterobacter cloacae bloodstream infections occurring at a tertiary care university hospital in Switzerland: is cefepime adequate therapy?

Despite many years of clinical experience with cefepime, data regarding the outcome of patients suffering from bloodstream infections (BSIs) due to Enterobacter cloacae (Ecl) are scarce. To address the gap in our knowledge, 57 Ecl responsible for 51 BSIs were analysed implementing phenotypic and molecular methods (microarrays, PCRs for bla and other genes, rep-PCR to analyse clonality). Only two E. cloacae (3.5%) were ESBL-producers, whereas 34 (59.6%) and 18 (31.6%) possessed inducible (Ind-Ecl) or derepressed (Der-Ecl) AmpC enzymes, respectively. All isolates were susceptible to imipenem, meropenem, gentamicin and ciprofloxacin. Der-Ecl were highly resistant to ceftazidime and piperacillin/tazobactam (both MIC₉₀≥256 μg/mL), whereas cefepime retained its activity (MIC₉₀ of 3 μg/mL). rep-PCR indicated that the isolates were sporadic, but Ecl collected from the same patients were indistinguishable. In particular, three BSIs initially due to Ind-Ecl evolved (under ceftriaxone or piperacillin/tazobactam treatment) into Der-Ecl because of mutations or a deletion in ampD or insertion of IS4321 in the promoter. These last two mechanisms have never been described in Ecl. Mortality was higher for BSIs due to Der-Ecl than Ind-Ecl (3.8% vs. 29.4%; P=0.028) and was associated with the Charlson co-morbidity index (P=0.046). Using the following directed treatments, patients with BSI showed a favourable treatment outcome: cefepime (16/18; 88.9%); carbapenems (12/13; 92.3%); ceftriaxone (4/7; 57.1%); piperacillin/tazobactam (5/7; 71.4%); and ciprofloxacin (6/6; 100%). Cefepime represents a safe therapeutic option and an alternative to carbapenems to treat BSIs due to Ecl when the prevalence of ESBL-producers is low.

Genetic diversity in fluoroquinolone and macrolide-resistant Campylobacter coli from pigs

The genetic diversity of 115 Campylobacter coli strains, isolated from pigs of 59 geographical distant farms in Switzerland, were characterized on the basis of their DNA fingerprints and resistance to macrolides and fluoroquinolones. Sequence analysis showed that the macrolide-resistant isolates had a point mutation in the 23S ribosomal RNA (rRNA) genes (A2075G) and that the fluoroquinolone-resistant isolates had a point mutation in the gyrase gene gyrA (C257T). One fluoroquinolone-resistant strain had an additional transition mutation in the gyrB gene (A1471C). The flaA restriction fragment length polymorphism (RFLP) genotyping revealed that 57% of the isolates were genetically different. Point mutations in the 23S rRNA and gyrA genes could be found in both genetically distant and genetically related isolates. Additionally, isolates with and without point mutations were found within individual farms and on different farms. This study showed that the ciprofloxacin and erythromycin-resistant C. coli population present on the pig farms is not issued from a common ancestral clone, but individual Campylobacter strains have most likely mutated independently to acquire resistances under the selective pressure of an antibiotic.

T cell-mediated hypersensitivity to quinolones: mechanisms and cross-reactivity

BACKGROUND: Quinolones are widely used, broad spectrum antibiotics that can induce immediate- and delayed-type hypersensitivity reactions, presumably either IgE or T cell mediated, in about 2-3% of treated patients. OBJECTIVE: To better understand how T cells interact with quinolones, we analysed six patients with delayed hypersensitivity reactions to ciprofloxacin (CPFX), norfloxacin (NRFX) or moxifloxacin (MXFX). METHODS: We confirmed the involvement of T cells in vivo by patch test and in vitro by means of the lymphocyte proliferation test (LTT). The nature of the drug-T cell interaction as well as the cross-reactivity with other quinolones were investigated through the generation and analysis (flow cytometry and proliferation assays) of quinolone-specific T cell clones (TCC). RESULTS: The LTT confirmed the involvement of T cells because peripheral blood mononuclear cells (PBMC) mounted an enhanced in vitro proliferative response to CPFX and/or NRFX or MXFX in all patients. Patch tests were positive after 24 and 48 h in three out of the six patients. From two patients, CPFX- and MXFX-specific CD4(+)/CD8(+) T cell receptor (TCR) alphabeta(+) TCC were generated to investigate the nature of the drug-T cell interaction as well as the cross-reactivity with other quinolones. The use of eight different quinolones as antigens (Ag) revealed three patterns of cross-reactivity: clones exclusively reacting with the eliciting drug, clones with a limited cross-reactivity and clones showing a broad cross-reactivity. The TCC recognized quinolones directly without need of processing and without covalent association with the major histocompatability complex (MHC)-peptide complex, as glutaraldehyde-fixed Ag-presenting cells (APC) could present the drug and washing quinolone-pulsed APC removed the drug, abrogating the reactivity of quinolone-specific TCC. CONCLUSION: Our data show that T cells are involved in delayed immune reactions to quinolones and that cross-reactivity among the different quinolones is frequent.

Influence of secondary infection on amputation in chronic critical limb ischemia

OBJECTIVES: To evaluate the influence of secondary infection on major amputation in chronic critical leg ischemia (CLI). DESIGN: Prospective, controlled observational study. MATERIALS AND METHODS: Sixty-seven patients with CLI and ischemic lesions participated in the study. Presence of infection was defined by clinical, laboratory and radiological criteria. Patients were categorized as having no local infection, soft tissue infection or osteomyelitis treated without antibiotics, amoxicillin/clavulanacid for 1 month or ciprofloxacin and clindamycin for 3 months, respectively. Clinical outcome was assessed at 2, 6 and 12 months. Study endpoints were major amputation and mortality. Analyses were performed using the Kaplan-Meier method. RESULTS: Forty-seven of 67 patients had a local infection. Major amputation was lower in patients with successful revascularization as compared to patients unsuitable for or with failed (without) revascularization (0% vs 26%, p<0.01). In patients with successful revascularization the probability of complete healing was lower with secondary infection (23% vs 71%, p=0.03). In patients without revascularization complete healing was rare (<10%), but secondary infection did not influenced major amputation, mortality or serious adverse events. CONCLUSION: Secondary infection reduces the likelihood of successful healing following revascularisation of CLI.

Antimicrobial resistance in bacteria from Swiss veal calves at slaughter

Bacteria with antimicrobial resistance can be transferred from animals to humans and may compromise antimicrobial treatment in case of infection. To determine the antimicrobial resistance situation in bacteria from Swiss veal calves, faecal samples from 500 randomly selected calves originating from 129 farms were collected at four big slaughterhouses. Samples were cultured for Escherichia coli, Enterococcus sp. and Campylobacter sp. and isolated strains were tested for antimicrobial susceptibility to selected antimicrobial agents by the minimal inhibitory concentration technique using the broth microdilution method. From 100 farms, data on farm management, animal husbandry and antimicrobial treatments of the calves were collected by questionnaire. Risk factors associated with antimicrobial resistance were identified by logistic regression. In total, 467 E. coli, 413 Enterococcus sp. and 202 Campylobacter sp. were isolated. Of those, 68.7%, 98.7% and 67.8%, respectively, were resistant to at least one of the tested antimicrobial agents. Resistance was mainly observed to antimicrobials frequently used in farm animals. Prevalence of resistance to antimicrobials important for human treatment was generally low. However, a rather high number of quinupristin/dalfopristin-resistant Enterococcus faecium and ciprofloxacin-resistant Campylobacter sp. were detected. External calf purchase, large finishing groups, feeding of milk by-products and administration of antimicrobials through feed upon arrival of the animals on the farm significantly increased the risk of antimicrobial resistance at farm level. Participation in a quality assurance programme and injection of a macrolide upon arrival of the animals on the farm had a protective effect. The present study showed that veal calves may serve as a reservoir for resistant bacteria. To ensure food safety, veal calves should be included in the national monitoring programme for antimicrobial resistance in farm animals. By improving farm management and calf husbandry the prevalence of resistance may be reduced.

Antibiotic-dependent correlation between drug-induced killing and loss of luminescence in Streptococcus gordonii expressing luciferase

Measuring antibiotic-induced killing relies on time-consuming biological tests. The firefly luciferase gene (luc) was successfully used as a reporter gene to assess antibiotic efficacy rapidly in slow-growing Mycobacterium tuberculosis. We tested whether luc expression could also provide a rapid evaluation of bactericidal drugs in Streptococcus gordonii. The suicide vectors pFW5luc and a modified version of pJDC9 carrying a promoterless luc gene were used to construct transcriptional-fusion mutants. One mutant susceptible to penicillin-induced killing (LMI2) and three penicillin-tolerant derivatives (LMI103, LMI104, and LMI105) producing luciferase under independent streptococcal promoters were tested. The correlation between antibiotic-induced killing and luminescence was determined with mechanistically unrelated drugs. Chloramphenicol (20 times the MIC) inhibited bacterial growth. In parallel, luciferase stopped increasing and remained stable, as determined by luminescence and Western blots. Ciprofloxacin (200 times the MIC) rapidly killed 1.5 log10 CFU/ml in 2-4 hr. Luminescence decreased simultaneously by 10-fold. In contrast, penicillin (200 times the MIC) gave discordant results. Although killing was slow (< or = 0.5 log10 CFU/ml in 2 hr), luminescence dropped abruptly by 50-100-times in the same time. Inactivating penicillin with penicillinase restored luminescence, irrespective of viable counts. This was not due to altered luciferase expression or stability, suggesting some kind of post-translational modification. Luciferase shares homology with aminoacyl-tRNA synthetase and acyl-CoA ligase, which might be regulated by macromolecule synthesis and hence affected in penicillin-inhibited cells. Because of resemblance, luciferase might be down-regulated simultaneously. Luminescence cannot be universally used to predict antibiotic-induced killing. Thus, introducing reporter enzymes sharing mechanistic similarities with normal metabolic reactions might reveal other effects than those expected.

Sub-inhibitory concentrations of vancomycin prevent quinolone-resistance in a penicillin-resistant isolate of Streptococcus pneumoniae

BACKGROUND: The continuous spread of penicillin-resistant pneumococci represents a permanent threat in the treatment of pneumococcal infections, especially when strains show additional resistance to quinolones. The main objective of this study was to determine a treatment modality impeding the emergence of quinolone resistance. RESULTS: Exposure of a penicillin-resistant pneumococcus to increasing concentrations of trovafloxacin or ciprofloxacin selected for mutants resistant to these drugs. In the presence of sub-inhibitory concentrations of vancomycin, development of trovafloxacin-resistance and high-level ciprofloxacin-resistance were prevented. CONCLUSIONS: Considering the risk of quinolone-resistance in pneumococci, the observation might be of clinical importance.

Quinolone antibiotics in therapy of experimental pneumococcal meningitis in rabbits

Using a rabbit model of pneumococcal meningitis, we compared the pharmacokinetics and bactericidal activities in cerebrospinal fluid (CSF) of older (ciprofloxacin, ofloxacin) and newer (levofloxacin, temafloxacin, CP-116,517, and Win 57273) quinolones with those of the beta-lactam ceftriaxone. All quinolones penetrated into the inflamed CSF better than ceftriaxone, and the speed of entry into CSF was closely related to their degrees of lipophilicity. At a dose of 10 mg/kg.h, which in the case of the quinolones already in use in clinical practice produced concentrations attainable in the sera and CSF of humans, ciprofloxacin had no antipneumococcal activity (delta log10 CFU/ml.h, +0.20 +/- 0.14). Ofloxacin (delta log10 CFU/ml.h, -0.13 +/- 0.12), temafloxacin (delta log10 CFU/ml.h, -0.19 +/- 0.18), and levofloxacin (delta log10 CFU/ml.h, -0.24 +/- 0.16) showed slow bactericidal activity (not significantly different from each other), while CP-116,517 (delta log10 CFU/ml.h, -0.59 +/- 0.21) and Win 57273 (delta log10 CFU/ml.h, -0.72 +/- 0.20) showed increased bactericidal activities in CSF that was comparable to that of ceftriaxone at 10 mg/kg.h (delta log10 CFU/ml.h, -0.80 +/- 0.17). These improved in vivo activities of the newer quinolones reflected their increased in vitro activities. All quinolones and ceftriaxone showed positive correlations between bactericidal rates in CSF and concentrations in CSF relative to their MBCs. Only when this ratio exceeded 10 did the antibiotics exhibit rapid bactericidal activities in CSF. In conclusion, in experimental pneumococcal meningitis the activities of new quinolones with improved antipneumococcal activities were comparable to that of ceftriaxone.

Stratification of cumulative antibiograms in hospitals for hospital unit, specimen type, isolate sequence and duration of hospital stay

BACKGROUND: Empirical antibiotic therapy is based on patients' characteristics and antimicrobial susceptibility data. Hospital-wide cumulative antibiograms may not sufficiently support informed decision-making for optimal treatment of hospitalized patients. METHODS: We studied different approaches to analysing antimicrobial susceptibility rates (SRs) of all diagnostic bacterial isolates collected from patients hospitalized between July 2005 and June 2007 at the University Hospital in Zurich, Switzerland. We compared stratification for unit-specific, specimen type-specific (blood, urinary, respiratory versus all specimens) and isolate sequence-specific (first, follow-up versus all isolates) data with hospital-wide cumulative antibiograms, and studied changes of mean SR during the course of hospitalization. RESULTS: A total of 16 281 isolates (7965 first, 1201 follow-up and 7115 repeat isolates) were tested. We found relevant differences in SRs across different hospital departments. Mean SRs of Escherichia coli to ciprofloxacin ranged between 64.5% and 95.1% in various departments, and mean SRs of Pseudomonas aeruginosa to imipenem and meropenem ranged from 54.2% to 100% and 80.4% to 100%, respectively. Compared with hospital cumulative antibiograms, lower SRs were observed in intensive care unit specimens, follow-up isolates and isolates causing nosocomial infections (except for Staphylococcus aureus). Decreasing SRs were observed in first isolates of coagulase-negative staphylococci with increasing interval between hospital admission and specimen collection. Isolates from different anatomical sites showed variations in SRs. CONCLUSIONS: We recommend the reporting of unit-specific rather than hospital-wide cumulative antibiograms. Decreasing antimicrobial susceptibility during hospitalization and variations in SRs in isolates from different anatomical sites should be taken into account when selecting empirical antibiotic treatment.

Antimicrobial resistance in Escherichia coli strains isolated from Swiss weaned pigs and sows

Based on Directive (EC) No 99/2003, monitoring programs on the development of antimicrobial resistance in bacteria from livestock are implemented in many European countries. The aim of the present study was (i) to establish comprehensive baseline data on the antimicrobial resistance situation in Escherichia coli isolates obtained from healthy pigs (pooled fecal samples) originating from 60 Swiss pig-breeding farms, and (ii) to analyze differences in the resistance frequency between Escherichia coli isolates from weaned pigs and sows. Susceptibility testing (disc diffusion method) was performed on 429 isolates from weaned pigs and 431 isolates from sows. Overall, 17.7% of the isolates from weaned pigs and 22.5% of the Escherichia coli isolates from sows were susceptible to all antibiotics tested. Low resistance prevalence was found for amoxicillin, amoxicillin/clavulanic acid, ampicillin, cefquinome, ciprofloxacin, colistin, florfenicol, and gentamicin. The most frequently found resistances were against streptomycin (60.6% of the isolates from weaners and 64.3% of the isolates from sows), sulfonamide (51.5% and 26.9%), tetracycline (35.2% and 22.0%), and trimethoprim (27.5% and 11.1%). With exception of colistin, most resistances were found for those antibiotics commonly used on the farms. Except for ciprofloxacin and streptomycin, isolates from weaned pigs showed higher resistance prevalence than those from sows. This difference was significant for cefquinome, florfenicol, sulfonamide, tetracycline, and trimethoprim (p<0.05).