Regional differences in Clostridium difficile infections in relation to fluoroquinolone and proton pump inhibitor use, Finland, 2008-2011

BACKGROUND

Several antimicrobial agents and proton pump inhibitors (PPIs) have been identified as risk factors for Clostridium difficile infections (CDIs). Nationwide laboratory-based surveillance of CDIs in Finland since 2008 has shown variation in regional CDI rates. We evaluated whether regional differences in CDI rates were associated with antibacterial and PPI use.

METHODS

Data on mean annual incidence rates of CDIs during 2008-2011 in 21 healthcare districts (HDs) were obtained from the National Infectious Disease Register, consumption (median annual use) of antimicrobials and PPIs from the Finnish Medical Agency, availability of molecular diagnostics by a laboratory survey and data on ribotypes from the national reference laboratory. The association over the 4 years was measured by incidence rate ratio (IRR) and we performed both bivariate and multivariate analyses.

RESULTS

During 2008-2011, PPI use increased 27% but fluoroquinolone use was stable. The level of fluoroquinolone use was strongly associated with the mean annual CDI incidence rate in different HDs over the 4-year period, but PPI use had less effect. The molecular diagnostics methodology and PCR ribotype 027 were not independently associated with CDI rate. The final multivariable model only included fluoroquinolone and PPI use; IRR for fluoroquinolones was 2.20 (95% confidence interval (CI), 1.32-3.67; p = 0.003).

CONCLUSIONS

Fluoroquinolone use may play a role in regional differences in CDI rates. Although the use has not recently increased, regionally targeted antimicrobial stewardship campaigns promoting appropriate use of fluoroquinolones should still be encouraged since they may decrease the incidence of CDIs.

Once-daily, oral levofloxacin monotherapy for low-risk neutropenic fever in cancer patients: a pilot study in China

This pilot study assesses the safety and efficacy of once-daily, oral levofloxacin monotherapy in Chinese patients with low-risk febrile neutropenia. In this prospective, single-arm, open-label, multicenter clinical trial, 46 adult Chinese patients with solid tumors and low-risk febrile neutropenia were included. Patients received oral levofloxacin monotherapy (500 mg orally/day) until day 12, followed by 7 days of follow-up (day 19). Body temperature was measured three times per day. On days 2, 3, 5-7, 9, 12, and 19, disease symptoms and vital signs were recorded, adverse drug reactions were assessed, and blood samples were collected to determine the whole-blood cell count and the absolute neutrophil count. Blood cultures and chest radiographs were performed simultaneously until negative results were found. Oral levofloxacin was effective and well tolerated in 97.6% of patients irrespective of the cancer type and cause of fever. Body temperature began to decline in 24.4, 68.3, and 90.2% of patients, respectively, at 12, 24, and 48 h after initiating levofloxacin therapy. On days 5 and 7, 95.1 and 97.6% of the patients had complete defervescence, respectively. The median time for absolute neutrophil count recovery to at least 1500/mm after initiation of treatment was 3 days. Only one patient reported mild diarrhea. This pilot study showed that oral levofloxacin quickly and effectively reduced fever, initiated neutrophil recovery, and was well tolerated in Chinese low-risk febrile neutropenic patients with solid tumors. Further study is needed to compare patient data of levofloxacin with the standard amoxicillin/ciprofloxacin protocol in this population for both safety and efficacy.

Salmonella subtypes with increased MICs for azithromycin in travelers returned to The Netherlands

Antimicrobial susceptibility was analyzed for 354 typhoidal Salmonella isolates collected during 1999-2012 in the Netherlands. In 16.1% of all isolates and in 23.8% of all isolates that showed increased MICs for ciprofloxacin, the MIC for azithromycin was increased. This resistance may complicate empirical treatment of enteric fever.

Fluoroquinolones impair tendon healing in a rat rotator cuff repair model: a preliminary study

BACKGROUND

Recent studies suggest that fluoroquinolone antibiotics predispose tendons to tendinopathy and/or rupture. However, no investigations on the reparative capacity of tendons exposed to fluoroquinolones have been conducted.

HYPOTHESIS

Fluoroquinolone-treated animals will have inferior biochemical, histological, and biomechanical properties at the healing tendon-bone enthesis compared with controls.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ninety-two rats underwent rotator cuff repair and were randomly assigned to 1 of 4 groups: (1) preoperative (Preop), whereby animals received fleroxacin for 1 week preoperatively; (2) pre- and postoperative (Pre/Postop), whereby animals received fleroxacin for 1 week preoperatively and for 2 weeks postoperatively; (3) postoperative (Postop), whereby animals received fleroxacin for 2 weeks postoperatively; and (4) control, whereby animals received vehicle for 1 week preoperatively and for 2 weeks postoperatively. Rats were euthanized at 2 weeks postoperatively for biochemical, histological, and biomechanical analysis. All data were expressed as mean ± standard error of the mean (SEM). Statistical comparisons were performed using either 1-way or 2-way ANOVA, with P < .05 considered significant.

RESULTS

Reverse transcriptase quantitative polymerase chain reaction (RTqPCR) analysis revealed a 30-fold increase in expression of matrix metalloproteinase (MMP)-3, a 7-fold increase in MMP-13, and a 4-fold increase in tissue inhibitor of metalloproteinases (TIMP)-1 in the Pre/Postop group compared with the other groups. The appearance of the healing enthesis in all treated animals was qualitatively different than that in controls. The tendons were friable and atrophic. All 3 treated groups showed significantly less fibrocartilage and poorly organized collagen at the healing enthesis compared with control animals. There was a significant difference in the mode of failure, with treated animals demonstrating an intrasubstance failure of the supraspinatus tendon during testing. In contrast, only 1 of 10 control samples failed within the tendon substance. The healing enthesis of the Pre/Postop group displayed significantly reduced ultimate load to failure compared with the Preop, Postop, and control groups. There was no significant difference in load to failure in the Preop group compared with the Postop group. Pre/Postop animals demonstrated significantly reduced cross-sectional area compared with the Postop and control groups. There was also a significant reduction in area between the Preop and control groups.

CONCLUSION

In this preliminary study, fluoroquinolone treatment negatively influenced tendon healing.

CLINICAL RELEVANCE

These findings indicate that there was an active but inadequate repair response that has potential clinical implications for patients who are exposed to fluoroquinolones before tendon repair surgery.

Ciprofloxacin-induced tendinopathy of the gluteal tendons

Fluoroquinolone-induced tendinopathy most commonly affects the Achilles tendon; however, involvement of several other tendons has been described. This is a case report of ciprofloxacin-induced tendinopathy of the gluteal tendons with MRI findings. An obese 25-year-old woman with no significant past medical history was diagnosed with acute pyelonephritis and was treated with intravenous ciprofloxacin. Shortly after her first dose of ciprofloxacin, she developed severe left hip pain and decreased range of motion. MRI of the hips showed bilateral tendinopathy of the gluteal muscle insertion. A diagnosis of ciprofloxacin-induced tendinopathy was made based on her MRI and a Naranjo score of 7. Ciprofloxacin was stopped and her pain quickly resolved. Fluoroquinolones cause tendinopathy in 0.14 % to 0.4 % of patients using these agents. Fluoroquinolone-associated tendinopathy is a serious adverse reaction that can affect many tendons and should be considered in any patient presenting with new musculoskeletal complaints and in whom there is a history of fluoroquinolone use within the preceding 6 months.

Dramatic decrease in fluoroquinolones in the pediatric population in Korea

PURPOSE

This study was performed to evaluate the change of prescribing patterns after the regulatory action regarding fluoroquinolones in pediatric patients.

METHODS

We conducted a time series analysis using the Korea Health Insurance Review and Assessment Service National Patients Sample database. Study subjects consisted of pediatric patients under 18 years of age who were prescribed antibiotics at least once (ATC code, J01) before (January 2009-December 2009) and after implementation (January 2010-December 2011) of the regulation. The use of fluoroquinolones was defined as the use of the following antibiotics for at least once in pediatric patients: ofloxacin, ciprofloxacin, norfloxacin, lomefloxacin, levofloxacin, and gemifloxacin. We calculated the number of pediatric fluoroquinolone users for each month. The difference between proportions before and after the regulation was estimated as relative and absolute reduction of fluoroquinolone use. We calculated 95% confidence intervals (CI).

RESULTS

We identified 4, 945, 169 antibiotic prescriptions in 484, 914 pediatric patients. During the 12-month period before implementation, percentage of fluoroquinolone use was 4.81% (95% CI: 4.70-4.91%, N = 8001). We observed a rapid decrease in the monthly number of fluoroquinolone users in pediatric population after the implementation of regulatory action. In the year after regulatory action, the percentage of fluoroquinolone use was only 0.26% (95% CI: 0.24-0.28%, N = 834). Overall, there was a 94.55% relative reduction (95% CI: 88.02-101.56%) in the use of fluoroquinolones.

CONCLUSION

Korean regulatory actions regarding fluoroquinolones had an effect of reducing use in pediatric population.

Clinical presentation and treatment of orthopaedic implant-associated infection

Orthopaedic implants are highly susceptible to infection. The aims of treatment of infection associated with internal fixation devices are fracture consolidation and prevention of chronic osteomyelitis. Complete biofilm eradication is not the primary goal, as remaining adherent microorganisms can be removed with the device after fracture consolidation. By contrast, in periprosthetic joint infection (PJI), biofilm elimination is required. Surgical treatment of PJI includes debridement with retention, one- or two-stage exchange and removal without reimplantation. In addition, prolonged antibiotic treatment, preferably with an agent that is effective against biofilm bacteria, is required. Rifampicin is an example of an antibiotic with these properties against staphylococci. However, to avoid the emergence of resistance, rifampicin must always be combined with another antimicrobial agent. With this novel treatment approach, orthopaedic implant-associated infection is likely to be eradicated in up to 80-90% of patients. Because most antibiotics have a limited effect against biofilm infections, novel prophylactic and therapeutic options are needed. Surface coating with antimicrobial peptides that reduce bacterial attachment and biofilm formation can potentially prevent implant-associated infection. In addition, quorum-sensing inhibitors are a novel therapeutic option against biofilm infections.

Uncomplicated Urinary Tract Infections and Antibiotic Resistance-Epidemiological and Mechanistic Aspects

Uncomplicated urinary tract infections are typically monobacterial and are predominantly caused by Escherichia coli. Although several effective treatment options are available, the rates of antibiotic resistance in urinary isolates of E. coli have increased during the last decade. Knowledge of the actual local rates of antibiotic resistant pathogens as well as the underlying mechanisms are important factors in addition to the geographical location and the health state of the patient for choosing the most effective antibiotic treatment. Recommended treatment options include trimethoprim alone or in combination with sulfamethoxazol, fluoroquinolones, β-lactams, fosfomycin-trometamol, and nitrofurantoin. Three basic mechanisms of resistance to all antibiotics are known, i.e., target alteration, reduced drug concentration and inactivation of the drug. These mechanisms—alone or in combination—contribute to resistance against the different antibiotic classes. With increasing prevalence, combinations of resistance mechanisms leading to multiple drug resistant (mdr) pathogens are being detected and have been associated with reduced fitness under in vitro situations. However, mdr clones among clinical isolates such as E. coli sequence type 131 (ST131) have successfully adapted in fitness and growth rate and are rapidly spreading as a worldwide predominating clone of extraintestinal pathogenic E. coli.

SIADH associated with ciprofloxacin

OBJECTIVE

To report a case of ciprofloxacin-induced syndrome of inappropriate antidiuretic hormone (SIADH).

CASE SUMMARY

A 68-year-old Caucasian woman presented on 2 separate occasions with generalized weakness. Both times, she was started on ciprofloxacin for a urinary tract infection. Prior to the first episode, she had also been on Augmentin for several days. On both occasions, her ciprofloxacin was discontinued on admission, and her sodium levels rose. On the first occasion, she was given 5% dextrose in water to slow the rate of rise, yet she still corrected faster than the recommended rate. After the second admission, she was briefly given hypertonic saline but remained off intravenous fluids, and her sodium again rose faster than the recommended rate.

DISCUSSION

An objective causality assessment using the Naranjo scale was done. A score of 8 revealed a probable causality between ciprofloxacin and SIADH. The likely mechanism of this reaction is ciprofloxacin crossing the blood-brain barrier and stimulating the γ-aminobutyric acid and N-methyl-D-aspartate receptors, which leads to the synthesis and release of antidiuretic hormone.

CONCLUSION

Fluoroquinolones have the potential to cause SIADH. In this case, ciprofloxacin probably caused SIADH.

Previous antibiotic exposure and antimicrobial resistance in invasive pneumococcal disease: results from prospective surveillance

BACKGROUND

Estimating the risk of antibiotic resistance is important in selecting empiric antibiotics. We asked how the timing, number of courses, and duration of antibiotic therapy in the previous 3 months affected antibiotic resistance in isolates causing invasive pneumococcal disease (IPD).

METHODS

We conducted prospective surveillance for IPD in Toronto, Canada, from 2002 to 2011. Antimicrobial susceptibility was measured by broth microdilution. Clinical information, including prior antibiotic use, was collected by chart review and interview with patients and prescribers.

RESULTS

Clinical information and antimicrobial susceptibility were available for 4062 (90%) episodes; 1193 (29%) of episodes were associated with receipt of 1782 antibiotic courses in the prior 3 months. Selection for antibiotic resistance was class specific. Time elapsed since most recent antibiotic was inversely associated with resistance (cephalosporins: adjusted odds ratio [OR] per day, 0.98; 95% confidence interval [CI], .96-1.00; P = .02; macrolides: OR, 0.98; 95% CI, .96-.99; P = .005; penicillins: OR [log(days)], 0.62; 95% CI, .44-.89; P = .009; fluoroquinolones: profile penalized-likelihood OR [log(days)], 0.62; 95% CI, .39-1.04; P = .07). Risk of resistance after exposure declined most rapidly for fluoroquinolones and penicillins and reached baseline in 2-3 months. The decline in resistance was slowest for macrolides, and in particular for azithromycin. There was no significant association between duration of therapy and resistance for any antibiotic class. Too few patients received multiple courses of the same antibiotic class to assess the significance of repeat courses.

CONCLUSIONS

Time elapsed since last exposure to a class of antibiotics is the most important factor predicting antimicrobial resistance in pneumococci. The duration of effect is longer for macrolides than other classes.

Selection and evolution of resistance to antimicrobial drugs

The overuse and misuse of antibiotics over many years has selected a high frequency of resistance among medically important bacterial pathogens. The evolution of resistance is complex, frequently involving multiple genetic alterations that minimize biological fitness costs and/or increase the resistance level. Resistance is selected at very low drug concentrations, such as found widely distributed in the environment, and this selects for resistant mutants with a high fitness. Once resistance with high fitness is established in a community it is very difficult to reduce its frequency. Addressing the problem of resistance is essential if we are to ensure a future where we can continue to enjoy effective medical control of bacterial infections. This will require several actions including the discovery and development of novel antibiotics, the creation of a continuous pipeline of drug discovery, and the implementation of effective global antibiotic stewardship to reduce the misuse of antibiotics and their release into the environment.

Fluoroquinolone resistance and molecular characterization of gyrA and parC quinolone resistance-determining regions in Escherichia coli isolated from poultry

Escherichia coli are a common inhabitant of the gastrointestinal tract of mammals and birds; nevertheless, they may be associated with a variety of severe and invasive infections. Whereas fluoroquinolones (FQ) have been banned in the United States for use in poultry production, the use of these antimicrobials in poultry husbandry is still possible in the European Union, although with some restrictions. The aim of this study was to investigate the FQ resistance of 235 E. coli isolates recovered from chickens and turkeys. Minimum inhibitory concentrations were determined by a microdilution method, whereas mutations in the quinolone resistance-determining regions of the target genes, gyrA and parC, were detected by a PCR-based method. High resistance rates (>60%) were observed for nalidixic acid, flumequine, and difloxacin, whereas resistance to ciprofloxacin, danofloxacin, enrofloxacin, marbofloxacin, and sarafloxacin was less frequently reported (<40%). Sixty-four isolates (27.2%) showed full susceptibility toward the tested FQ, but 57 isolates (24.2%) were resistant to all tested FQ. The remaining 114 E. coli isolates (48.5%) were grouped in 5 different resistance patterns. Isolates resistant only to flumequine or nalidixic acid or both possessed 1 gyrA mutation, whereas isolates with further resistance to enrofloxacin, difloxacin, danofloxacin, and sarafloxacin had in addition 1 or 2 parC substitutions. Two gyrA mutations coupled with 1 substitution in parC were detected in isolates resistant to all tested FQ. The number of mutations and their correlation with the in vitro activity of FQ reflected the currently accepted model, according to which a single gyrA substitution is associated with resistance or decreased susceptibility to older quinolones, whereas further gyrA or parC substitutions are needed for a higher level of resistance.

Fluoroquinolone use is a risk factor for methicillin-resistant Staphylococcus aureus acquisition in long-term care facilities: a nested case-case-control study

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization is a well-established risk factor for subsequent infection and a key event in interindividual transmission. Some studies have showed an association between fluoroquinolones and MRSA colonization or infection. The present study was performed to identify specific risk factors for MRSA acquisition in long-term care facilities (LTCFs).

METHODS

A prospective cohort of patients naive for S. aureus colonization was established and followed (January 2008 through October 2010) in 4 French LTCFs. Nasal colonization status and potential risk factors were assessed weekly for 13 weeks after inclusion. Variables associated with S. aureus acquisition were identified in a nested-matched case-case-control study using conditional logistic regression models. Cases were patients who acquired MRSA (or methicillin-sensitive S. aureus [MSSA]). Patients whose nasal swab samples were always negative served as controls. Matching criteria were center, date of first nasal swab sample, and exposure time.

RESULTS

Among 451 included patients, 76 MRSA cases were matched to 207 controls and 112 MSSA cases to 208 controls. Multivariable analysis retained fluoroquinolones (odds ratio, 2.17; 95% confidence interval, 1.01-4.67), male sex (2.09; 1.10-3.98), and more intensive care at admission (3.24; 1.74-6.04) as significantly associated with MRSA acquisition, and body-washing assistance (2.85; 1.27-6.42) and use of a urination device (1.79; 1.01-3.18) as significantly associated with MSSA acquisition.

CONCLUSIONS

Our results suggest that fluoroquinolones are a risk factor for MRSA acquisition. Control measures to limit MRSA spread in LTCFs should also be based on optimization of fluoroquinolone use.

In Vitro Antibiofilm Efficacies of Different Antibiotic Combinations with Zinc Sulfate against Pseudomonas aeruginosa Recovered from Hospitalized Patients with Urinary Tract Infection

Urinary tract infections (UTIs) are a serious healthcare dilemma influencing millions of patients every year and represent the second most frequent type of body infection. Pseudomonas aeruginosa is a multidrug-resistant pathogen causing numerous chronic biofilm-associated infections including urinary tract, nosocomial, and medical devices-related infections. In the present study, the biofilm of P. aeruginosa CCIN34519, recovered from inpatients with UTIs, was established on polystyrene substratum and scanning electron microscopy (SEM) and was utilized for visualization of the biofilm. A previously described in vitro system for real-time monitoring of biofilm growth/inhibition was utilized to assess the antimicrobial effects of ciprofloxacin, levofloxacin, moxifloxacin, norfloxacin, ertapenem, ceftriaxone, gentamicin, and tobramycin as single antibiotics as well as in combinations with zinc sulfate (2.5 mM) against P.aeruginosa CCIN34519 biofilm. Meanwhile, minimum inhibitory concentrations (MICs) at 24 h and mutant prevention concentrations (MPCs) at 96 h were determined for the aforementioned antibiotics. The real-time monitoring data revealed diverse responses of P.aeruginosa CCIN34519 biofilm to the tested antibiotic-zinc sulfate combinations with potential synergisms in cases of fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin, and norfloxacin) and carbapenem (ertapenem) as demonstrated by reduced MIC and MPC values. Conversely, considerable antagonisms were observed with cephalosporin (ceftriaxone) and aminoglycosides (gentamicin, and tobramycin) as shown by substantially increased MICs and MPCs values. Further deliberate in vivo investigations for the promising synergisms are required to evaluate their therapeutic potentials for treatment of UTIs caused by P. aeruginosa biofilms as well as for developing preventive strategies.

A cross-sectional study to investigate pneumococcal vaccination in the elderly in a low income county: patient knowledge, awareness, and attitudes of vaccination and prevalence rates by socioeconomic status

BACKGROUND

Pneumonia represents the leading cause of infection-related death and the fifth cause of overall mortality, in the elderly. With increasing age, the human immune system undergoes characteristic changes which lead to increased incidence and severity of infectious diseases and to insufficient protection following vaccination as antibody response of elderly vaccines are weaker and decline faster.

OBJECTIVE

Knowledge and Attitude toward Pneumonia and its Vaccination in elderly patients.

RESULT

Among low SES, 54.9% (549/1000) while from high SES, 91.8% (918) responded that they had heard about pneumonia before (P<0.05). 79.5% (795/1000) patients of high SES had heard about pneumococcal vaccination while only 28.8% (288/1000) patients from low SES had heard about pneumococcal vaccine. Only 2.3% of low SES patients were immunized for pneumococcal vaccine while 16.5% high SES patients were vaccinated. Reported reason for not being immunized were; did not hear, no body advised, vaccine is too expensive, and ignored thinking it is not necessary.

METHOD

We conducted a cross-sectional study on 2000 elderly patients who were admitted in medicine and surgery wards of Civil Hospital Karachi and Aga Khan University Hospital Karachi from the period of October to December 2012 to determine their knowledge and attitude toward pneumonia and its vaccination in elderly. Study group was divided into low and high socio-economic status on the basis of patients coming to government Hospital i.e., civil hospital and private hospital i.e., Aga khan hospital. Data was collected through convenient sampling technique. Exclusion criteria were patients below 60 years and those who didn't give consent to be part of study.

CONCLUSION

Aside from introducing public awareness program about elderly vaccination at state level, free of cost vaccination of elderly individuals should be done.

Ciprofloxacin-resistant Campylobacter spp. in retail chicken, western Canada

During 2005–2010, the Canadian Integrated Program for Antimicrobial Resistance Surveillance identified increased prevalence of ciprofloxacin (a fluororquinolone) resistance among Campylobacter isolates from retail chicken in British Columbia (4%–17%) and Saskatchewan (6%–11%), Canada. Fluoroquinolones are critically important to human medicine and are not labeled for use in poultry in Canada.

Fitness benefits in fluoroquinolone-resistant Salmonella Typhi in the absence of antimicrobial pressure

Fluoroquinolones (FQ) are the recommended antimicrobial treatment for typhoid, a severe systemic infection caused by the bacterium Salmonella enterica serovar Typhi. FQ-resistance mutations in S. Typhi have become common, hindering treatment and control efforts. Using in vitro competition experiments, we assayed the fitness of eleven isogenic S. Typhi strains with resistance mutations in the FQ target genes, gyrA and parC. In the absence of antimicrobial pressure, 6 out of 11 mutants carried a selective advantage over the antimicrobial-sensitive parent strain, indicating that FQ resistance in S. Typhi is not typically associated with fitness costs. Double-mutants exhibited higher than expected fitness as a result of synergistic epistasis, signifying that epistasis may be a critical factor in the evolution and molecular epidemiology of S. Typhi. Our findings have important implications for the management of drug-resistant S. Typhi, suggesting that FQ-resistant strains would be naturally maintained even if fluoroquinolone use were reduced.

DOI:http://dx.doi.org/10.7554/eLife.01229.001

The fluoroquinolones are a group of antimicrobials that are used to treat a variety of life-threatening bacterial infections, including typhoid fever. Before the introduction of antimicrobials, the mortality rate from typhoid fever was 10–20%. Prompt treatment with fluoroquinolones has reduced this to less than 1%, and has also decreased the severity of symptoms suffered by people with the disease.

Now, however, the usefulness of many antimicrobials, including the fluoroquinolones, is threatened by the evolution of antimicrobial resistance within the bacterial populations being treated. Drug resistance in bacteria typically arises through specific mutations, or following the acquisition of antimicrobial resistance genes from other bacteria. It is thought that the frequent use of antimicrobials in human and animal health puts selective pressure on bacterial populations, allowing bacterial strains with mutations or genes that confer antimicrobial resistance to survive, while bacterial strains that are sensitive to the antimicrobials die out.

At first it was thought that specific mutations conferring antimicrobial resistance came at a fitness cost, which would mean that such mutations would be rare in the absence of antimicrobials. Now, based on research into typhoid fever, Baker et al. describe a system in which the majority of evolutionary routes to drug resistance are marked by significant fitness benefits, even in the absence of antimicrobial exposure.

Typhoid is caused by a bacterial pathogen known as Salmonella Typhi, and mutations in two genes—gyrA and parC—result in resistance to fluoroquinolones. Baker et al. show that mutations in these genes confer a measurable fitness advantage over strains without these mutations, even in the absence of exposure to fluoroquinolones. Moreover, strains with two mutations in one of these genes exhibited a higher than predicted fitness, suggesting that there is a synergistic interaction between the two mutations. This work challenges the dogma that antimicrobial resistant organisms have a fitness disadvantage in the absence of antimicrobials, and suggests that increasing resistance to the fluoroquinolones is not solely driven by excessive use of this important group of drugs.

DOI:http://dx.doi.org/10.7554/eLife.01229.002

Fitness gains hamper efforts to tackle drug resistance

It has long been assumed that resistance to antibiotics reduces the fitness of disease-causing bacteria, but experiments on Salmonella Typhi, the bacteria that causes Typhoid fever, are now challenging this view.

Influence of Sterilized Human Fecal Extract on the Sensitivity of Salmonella enterica ATCC 13076 and Listeria monocytogenes ATCC 15313 to Enrofloxacin

There is much debate on whether continuous exposure of commensal bacteria and potential pathogens residing in the human intestinal tract to low levels of antimicrobial agents from treated food animals pose a public health concern. To investigate antimicrobial effects on bacteria under colonic conditions, we studied resistance development in Salmonella enterica and Listeria monocytogenes exposed to enrofloxacin in the presence of fecal extract. The bacteria were incubated at 37 °C in Mueller-Hinton broth, with and without 0.01~0.5 μg/mL enrofloxacin, in the presence and absence of sucrose, and with 1% or 2.5% filter-sterilized fecal extract, for three passages. In the second and third passages, only the bacteria incubated in the media containing sterilized fecal extract grew in 0.5 μg/mL of enrofloxacin. Fecal extract (1% and 2.5%) decreased the sensitivity of S. enterica to enrofloxacin in the medium containing the efflux pump inhibitors reserpine and carbonyl cyanide-m-chlorophenylhydrazone (CCCP) and affected the accumulation of ethidium bromide (EtBr) in this bacterium. Enrofloxacin (0.06 µg/mL) and fecal extract altered the composition of fatty acids in S. enterica and L. monocytogenes. We conclude that fecal extract decreased the susceptibilities of S. enterica and L. monocytogenes to concentrations of enrofloxacin higher than the MIC and resulted in rapid resistance selection.

Resistance to Fluoroquinolone by a Combination of Efflux and Target Site Mutations in Enteroaggregative Escherichia coli Isolated in Korea

Objectives

Enteroaggregative Escherichia coli (EAEC) was recently reported as a major diarrheagenic pathogen in infant and adult travelers, both in developing and developed countries. EAEC strains are known to be highly resistant to antibiotics including quinolones. Therefore in this study we have determined the various mechanisms of quinolone resistance in EAEC strains isolated in Korea.

Methods

For 26 EAEC strains highly resistant to fluoroquinolone, minimal inhibitory concentrations for fluoroquinolones were determined, mutations in the quinolone target genes were identified by PCR and sequencing, the presence of transferable quinolone resistance mechanism were identified by PCR, and the contribution of the efflux pump was determined by synergy tests using a proton pump inhibitor. The expression levels of efflux pump-related genes were identified by relative quantification using real-time PCR.

Results

Apart from two, all tested isolates had common mutations on GyrA (Ser83Leu and Ser87Gly) and ParC (Ser80Gln). Isolates EACR24 and EACR39 had mutations that have not been reported previously: Ala81Pro in ParC and Arg157Gly in GyrA, respectively. Increased susceptibility of all the tested isolates to ciprofloxacin and norfloxacin in the presence of the pump inhibitor implies that efflux pumps contributed to the resistance against fluoroquinolones. Expression of the efflux pump-related genes, tolC, mdfA, and ydhE, were induced in isolates EACR 07, EACR 29, and EACR 33 in the presence of ciprofloxacin.

Conclusion

These results indicate that quinolone resistance of EAEC strains mainly results from the combination of mutations in the target enzyme and an increased expression of efflux pump-related genes. The mutations Ala81Pro in ParC and Arg157Gly in GyrA have not been reported previously the exact influence of these mutations should be investigated further.

Multiplex Real-Time Polymerase Chain Reaction-Based Method for the Rapid Detection of gyrA and parC Mutations in Quinolone-Resistant Escherichia coli and Shigella spp

Two real-time polymerase chain reaction assays were developed to detect mutations in codons 83 and 87 in gyrA and in codons 80 and 91 in parC, the main sites that causes quinolone resistance in pathogenic Escherichia coli and Shigella spp. isolates. These assays can be employed as a useful method for controlling infections caused by quinolone-resistant E coli and Shigella isolates.

Prophylaxis of neutropenic fever with ciprofloxacin in patients with acute myeloid leukemia treated with intensive chemotherapy

AIMS

Neutropenic fever is one of the most serious complications after induction chemotherapy in acute myeloid leukemia (AML). Prophylaxis with antibiotics for prevention of neutropenic fever in AML is controversial and there are few studies on this issue from developing countries.

METHODS

In this retrospective study, we analyzed the clinical data and outcome of patients with AML who did or did not receive prophylactic ciprofloxacin 500 mg BD for neutropenic fever.

RESULTS

A total of 69 AML patients were treated by "3 + 7" protocol for their first induction chemotherapy. Prophylaxis was given to 25 of them. Incidence of neutropenic fever was the same in both groups (80% vs 82%). Duration of fever and the mortality rate were also similar in both groups.

CONCLUSION

It seems that in developing countries, using prophylactic ciprofloxacin has no significant effect on the incidence of neutropenic fever and the outcome of the AML patients.

Orofacial dyskinesia associated with the use of levofloxacin

OBJECTIVE

To describe a case of orofacial dyskinesia in a patient treated with levofloxacin for acute diverticulitis.

CASE SUMMARY

A 77-year-old woman with mild renal insufficiency was admitted with acute diverticulitis. She was initiated on levofloxacin 500 mg IV daily and metronidazole 500 mg IV every 8 hours. On day 4 of treatment, she experienced involuntary, rhythmic facial grimacing accompanied by periodic cervical muscular contractures. Her speech became dysarthric, interrupted by uncontrolled facial and tongue movements, all findings consistent with orofacial dyskinesia. Antibiotics were discontinued, and symptoms resolved after administration of diphenhydramine and lorazepam IV.

DISCUSSION

Fluoroquinolone-associated central nervous system (CNS) toxicities are infrequently observed. They are most commonly associated with ciprofloxacin and are thought to be related to inhibition of γ-aminobutyric acid receptors and activation of N-methyl-d-aspartate receptors. Orofacial dyskinesia has previously been reported primarily with second-generation fluoroquinolones, with only a single case report implicating a third-generation fluoroquinolone. To our knowledge, we report the second case of orofacial dyskinesia with a third-generation fluoroquinolone, the first such case associated with levofloxacin. The orofacial dyskinesia experienced in this case was categorized as probably related to levofloxacin, as assessed by the Naranjo adverse drug reaction probability assessment tool. Contributing factors likely included age and renal function.

CONCLUSIONS

Although rare, CNS toxicities such as orofacial dyskinesia have been reported with levofloxacin. Patients on fluoroquinolones of advanced age and with renal insufficiency should be monitored closely for such toxicities.

US-based emergency department visits for fluoroquinolone-associated hypersensitivity reactions

PURPOSE

To estimate the rate of hypersensitivity reactions per 100,000 prescription dispensings of fluoroquinolones based on care rendered in a nationally representative sample of US hospital emergency departments (ED).

METHODS

We analyzed the frequency of fluoroquinolone-associated hypersensitivity reactions using the National Electronic Injury Surveillance System-Cooperative Adverse Drug Event Surveillance system (2004-2010) in conjunction with US retail outpatient prescription data from IMS Health (2004-2010). We further categorized reaction severity into three subgroups (mild, moderate, and severe).

RESULTS

Based on 1422 cases of fluoroquinolone-associated hypersensitivity reactions and national drug utilization projections, we estimated risk of hypersensitivity reactions for moxifloxacin, ciprofloxacin, and levofloxacin. The absolute risk of a fluoroquinolone-related hypersensitivity reaction of any severity was low (44.0 (95% CI 34.8-53.3) ED visits/100,000 prescriptions); however, we identified a statistically significant difference in the relative risk (rate ratios) of seeking care in an ED attributed to moxifloxacin hypersensitivity compared to either levofloxacin or ciprofloxacin. For all reaction severities, the estimated ED visits/100,000 prescriptions were 141.3 (95% CI 99.9-182.7) for moxifloxacin, 40.8 (95% CI 31.5-50.0) for levofloxacin, and 26.3 (95% CI 20.8-31.9) for ciprofloxacin. When the rates were stratified by reaction severity category (mild or moderate-severe), moxifloxacin continued to be implicated in more ED visits per 100,000 prescriptions dispensed than either levofloxacin or ciprofloxacin.

CONCLUSION

Fluoroquinolones may cause hypersensitivity reactions requiring care in an ED, and relative to use, the rate of moxifloxacin-related hypersensitivity reactions is higher compared to levofloxacin or ciprofloxacin.