Management of fluoroquinolone resistance in Pseudomonas aeruginosa--outcome of monitored use in a referral hospital

Prevalence and Antibiotic Susceptibility of Bacterial Isolates From Dogs With Ulcerative Keratitis in Midwestern United States

The objective of this study was to describe bacterial culture and antibiotic susceptibility results in 476 dogs presenting with suspected bacterial keratitis in Iowa and surrounding Midwestern states, further detailing trends in patient characteristics, seasonality, and antimicrobial resistance. Corneal swabs yielded 465 bacterial isolates and 220 cultures (46.2%) with no apparent growth (0–5 isolates per culture). The most frequent bacterial genera were Staphylococcus (32.3%), Streptococcus (19.1%), and Pseudomonas (12.5%), while the most common bacterial species were Staphylococcus pseudintermedius (26.7%), Streptococcus canis (12%), and Pseudomonas aeruginosa (7.5%). Compared to mixed-breed dogs, canine breeds most likely to be examined for ulcerative keratitis included Boston terrier, Cavalier King Charles spaniel, miniature pinscher, pug, rat terrier, Saint Bernard, shih tzu, and silky terriers. In summer, the likelihood to yield a negative culture was reduced while the likelihood to culture Pseudomonas species was increased. Bacteria considered multidrug resistant (MDR, resistant to ≥ 3 antibiotic classes) represented 20% of all canine isolates and were most prevalent for Staphylococcus species (33%). An alarming, escalating trend of MDR prevalence was noted between 2016 (5%) and 2020 (34%). Individual ophthalmic preparations (i.e., single antibiotics or commercially available antibiotic combinations) with highest efficacy against all bacterial isolates included chloramphenicol (83%), ceftiofur (79%), amikacin (77%), neomycin-polymyxin B-bacitracin (77%), and gentamicin (74%). Efficacy of systemic antibiotics and combinations of ophthalmic preparations was also evaluated. Based on the present findings, triple antibiotic (Neo-Poly-Bac) is recommended as empirical monotherapy for prophylactic antibiotic therapy in dogs with simple corneal ulcers, while a chloramphenicol-ciprofloxacin combination is empirically recommended for therapeutic management of infected corneal ulcers. Pending culture and susceptibility results, appropriate selection of empiric antibiotic therapy is important to enhance therapeutic outcome and reduce antibacterial resistance in dogs with corneal ulceration.

The Impact of Antibiotic Stewardship Programs in Combating Quinolone Resistance: A Systematic Review and Recommendations for More Efficient Interventions

Quinolones are among the most commonly prescribed antibiotics worldwide. A clear relationship has been demonstrated between excessive quinolone use and the steady increase in the incidence of quinolone-resistant bacterial pathogens, both in hospital and community sites. In addition, exposure to quinolones has been associated with colonization and infection with healthcare-associated pathogens such as methicillin-resistant Staphylococcus aureus and Clostridium difficile in hospitalized patients. Therefore, the management of quinolone prescribing in hospitals through antibiotic stewardship programs is considered crucial. Although suggestions have been made by previous studies on the positive impact of stewardship programs concerning the emergence and spread of multidrug-resistant bacteria at hospital level, the association of quinolone-targeted interventions with reduction of quinolone resistance is vague. The purpose of this article was to evaluate the impact of stewardship interventions on quinolone resistance rates and healthcare-associated infections, through a literature review using systematic methods to identify and select the appropriate studies. Recommendations for improvements in quinolone-targeted stewardship programs are also proposed. Efforts in battling quinolone resistance should combine various interventions such as restriction formulary policies, prospective audits with feedback to prescribers, infection prevention and control measures, prompt detection of low-level resistance, educational programs, and guidelines for optimal quinolone usage. However, the effectiveness of such strategies should be assessed by properly designed and conducted clinical trials. Finally, novel approaches in diagnostic stewardship for rapidly detecting bacterial resistance, including PCR-based techniques, mass spectrometry, microarrays, and whole-genome sequencing as well as the prompt investigation on the clonality of quinolone-resistant strains, will strengthen our ability to personalize quinolone prescribing to individual patients.

[Resistance to fluoroquinolones in 2013: what are the consequences in internal medicine?]

Because of their important qualities, fluoroquinolones are amongst the most prescribed antibiotics in the world. The corollary of this success is the rapid increase in resistance to fluoroquinolones, responsible for treatment failures. Moreover, fluoroquinolone-resistance is often accompanied by resistance to other classes of antibiotics. Currently, significant levels of resistance are found both in hospitals and in community settings, severely limiting possibilities for empirical use of fluoroquinolones. A major mechanism explaining the rapid emergence of resistance to fluoroquinolones is their specific impact on human microbiota and the selection of resistant strains in the microbiota, which seems to be an unavoidable ecological side effect. In order to preserve the efficiency of this important class of antibiotics, limiting their use and respecting good practice recommendations are essential.

Topical piperacillin/tazobactam for recalcitrant pseudomonas aeruginosa keratitis

PURPOSE

To report the treatment of therapy-resistant Pseudomonas aeruginosa keratitis with topical piperacillin/tazobactam.

METHODS

Retrospective report of 3 cases.

RESULTS

Three patients with P. aeruginosa keratitis were unresponsive to various antimicrobials. Resolution of all 3 cases of keratitis occurred upon commencement of topical piperacillin/tazobactam.

CONCLUSION

Therapy-resistant P. aeruginosa keratitis acquired from the community is becoming an increasing problem. Topical piperacillin/tazobactam is an option for the treatment of therapy-resistant P. aeruginosa keratitis.

Impact of antibiotic restrictions: the ethical perspective

Antibiotic restrictions present difficult choices for physicians, patients and payors. Physicians must choose between the welfare of the patient and the directive of healthcare systems to restrict antibiotics. These may be supported with incentives or penalties, causing a conflict of interest. The patient has an expectation of best care, but will often be unaware of antibiotic restriction policies and is therefore not fully informed about his/her treatment. For payors, reducing the volume of antibiotic prescribing and/or prescribing less expensive antibiotics are apparently attractive targets for cost savings. However, we are only now beginning to understand the downstream consequences of restricting antibiotics on outcomes and costs. We are hampered by the lack of a universal ethical framework and information on outcomes. In addition, the concept of 'effective' or 'best' therapy will vary among different groups. Balancing the risks of treating or not treating with antibiotics is complex. Suboptimal therapy, that fails to eradicate the bacterial infection, exposes the patient to the risk of poor outcome, adverse events and the wider risk of antimicrobial resistance. Failure to treat where the risk of a poor outcome exceeds the risk of an adverse event is also ethically unacceptable. The key to rational antibiotic prescribing is to identify those patients who need antibiotic therapy and optimise therapy to achieve the fastest bacterial and clinical cure. We are only now beginning to assemble the information and tools to be able to make such decisions. Above all, we should treat on the basis of knowledge.

Mutant prevention concentration for ciprofloxacin and levofloxacin with Pseudomonas aeruginosa

The mutant prevention concentration (MPC) was determined by population analysis using six fluoroquinolone-susceptible isolates of Pseudomonas aeruginosa applied to fluoroquinolone-containing agar plates. The MPCs were 3 mg/L and 9.5 mg/L for ciprofloxacin and levofloxacin, respectively. At high concentrations of either compound, single-step gyrA resistance mutants were recovered. Using a modified method for estimating the MPC, 151 clinical isolates were surveyed. Modal MPCs were 2 mg/L and 8 mg/L, respectively, for ciprofloxacin and levofloxacin. Thus, ciprofloxacin is three to four times more active than levofloxacin against resistant mutant subpopulations. For individual isolates, the MPC correlated poorly with the minimum inhibitory concentration (r(2) = 0.41 and 0.39 for ciprofloxacin and levofloxacin, respectively).

Squeezing the antibiotic balloon: the impact of antimicrobial classes on emerging resistance

The ongoing problem of emerging antimicrobial resistance has been likened to a balloon where settling one specific issue results in a 'bulge' of even worse problems. However, much has been learned about how to best use our critical antibacterial agents in ways to avoid or even repair some of the resistance damage that has been done. A compilation of current literature strongly suggests that to slow the development of resistance to antimicrobial agents it is optimal to use drugs with more than one mechanism of action or target, to prescribe those with demonstrated ability to minimise or reverse resistance problems, and to avoid underdosing of potent antibiotics. The most recent information also indicates that it is best to limit empirical use of beta-lactam plus fluoroquinolone combination therapy, since these two classes activate some common resistance responses, and using them together can facilitate multidrug resistance in important pathogens, particularly Pseudomonas aeruginosa and Acinetobacter species. This review discusses the role of each major antimicrobial class on resistance development and presents specific strategies for combating the growing problem of multidrug-resistant bacteria. We now have the knowledge to better manage our antimicrobial agent prescribing practices, but finding the will and resources to apply our understanding remains a formidable challenge.

Impact of a fluoroquinolone formulary change on acquisition of quinolone-resistant gram-negative bacilli

Rising rates of fluoroquinolone resistance in bacteria have been associated with increased fluoroquinolone use. In vitro data show differences in potency among fluoroquinolone antibiotics against gram-negative bacteria and have led to the hypothesis that rates of selection of resistant microorganisms may be affected by the choice of the specific fluoroquinolone. Because clinical data to prove this hypothesis are lacking, the aim of the present study was to determine rates of acquisition of quinolone-resistant gram-negative bacilli (QRGNB) in the fecal flora of medical intensive care unit patients before and after a formulary change from ciprofloxacin to levofloxacin. Unadjusted rate ratios for acquisition of QRGNB were 1.09 (95%CI, 1.02-1.16) for each day of ciprofloxacin use and 1.01 (95%CI, 0.87-1.17) for each day of levofloxacin use. Following adjustment for other antibiotic use, enteral feeding, APACHE II score, and nursing home admission, neither ciprofloxacin nor levofloxacin use was associated with acquisition of QRGNB. In conclusion, a formulary change from ciprofloxacin to levofloxacin was not significantly associated with an increased risk of acquisition of QRGNB.

Fluoroquinolone-resistant Pseudomonas aeruginosa: risk factors for acquisition and impact on outcomes

OBJECTIVES

Resistance among Pseudomonas aeruginosa has risen dramatically and parallels the increase in fluoroquinolone (FQ) prescribing in recent years. Risk factors for FQ resistance in P. aeruginosa and its impact on outcomes need to be well characterized.

METHODS

A case-control study was carried out on hospitalized adult patients from whom FQ-resistant (case) and FQ-susceptible (control) P. aeruginosa were isolated.

RESULTS

A total of 177 patients with positive cultures (91 cases and 86 controls) and 119 with documented infections (65 cases, 54 controls) were included in risk factor and outcomes analysis, respectively. Independent risk factors for FQ resistance were: FQ exposure (OR 12.6, CI 4.95-32), nosocomial acquisition (OR 8.6, CI 3.5-20.7), and diabetes mellitus (OR 6.4, CI 2.1-19.3). An FQ agent was prescribed in 59% of patients receiving an 'antipseudomonal' empirical regimen. Compared with controls, FQ-resistant cases had a median delay to receiving effective therapy of 3.5 days versus 1 day and poorer outcomes: (i) lower complete response rate (45% versus 63%, P=0.04); (ii) longer time to achieve clinical stability (8 days versus 3 days, P=0.005); and (iii) higher infection-related mortality (21% versus 7%; OR = 2.9, 0.9-9.4). Empirical FQ use (OR 4.6, CI 1.5-14.3), FQ resistance (OR 3.6, CI 1.0-13.1), and high APACHE II score (OR 1.1, CI 1.0-1.2) were independent risk factors for increased mortality.

CONCLUSIONS

FQ exposure from widespread prescribing is a modifiable risk factor for FQ resistance in P. aeruginosa. FQ empirical therapy for Pseudomonas infections may be associated with significant delays in administering effective therapy resulting in adverse outcomes.

Impact of restricting fluoroquinolone prescription on bacterial resistance in an intensive care unit

The purpose of this study was to assess the effect of reducing prescription of fluoroquinolones in an intensive care unit (ICU) upon bacterial resistance, particularly as regards Pseudomonas aeruginosa. For six months between January 2001 and June 2001, administration of fluoroquinolones was kept to a minimum. A bacteriological screening of patients was performed to assess the incidence of fluoroquinolone-resistant bacteria. There was a 75.8% restriction in prescriptions of fluoroquinolones. There was no significant change in bacterial ecology between the periods preceding (12 months) and following (12 months) restriction. There was a significant recovery of sensitivity of P. aeruginosa to ciprofloxacin (P<or=0.01), with a decrease in resistant strains from 71.3% in the pre-restriction period to 52.4% in the post-restriction period. Regarding clinical data, no significant differences were noted between the pre-restriction and the post-restriction periods, except for the number of cases of ventilator-associated pneumonia with P. aeruginosa resistant to ciprofloxacin. This study demonstrated the possibility of introducing rotation of antibiotics in an ICU.

Predicting hospital rates of fluoroquinolone-resistant Pseudomonas aeruginosa from fluoroquinolone use in US hospitals and their surrounding communities

Rates of fluoroquinolone resistance among Pseudomonas aeruginosa in hospitals are increasing, but interhospital variability is great. We sought to determine whether this variability correlated to fluoroquinolone use in hospitals and in the surrounding community. Hospital quinolone use in 1999 (24 hospitals) through 2001 (35 hospitals) was determined from billing records. The number of fluoroquinolone prescriptions within a 10-mile (approximately 16-km) radius of each hospital was determined for 1999 and 2000. Hospital fluoroquinolone use increased from 1999 through 2001, from 137 to 163 defined daily doses (DDD)/1000 patient-days (P=.01). The rate of community fluoroquinolone use also increased, from 2.3 to 2.8 DDD/1000 inhabitant-days (P<.001). Rates of fluoroquinolone-resistant P. aeruginosa increased from 29% in 1999 to 36% in 2001 (P=.003). Both community and hospital fluoroquinolone use were predictive of rates of fluoroquinolone-resistant P. aeruginosa. Levofloxacin was associated with resistance, but ciprofloxacin was not. Most of the variability in resistance rates is explained by volume of fluoroquinolone use, both in the hospital and the surrounding community.

Fluoroquinolone AUIC Break Points and the Link to Bacterial Killing Rates Part 2: Human Trials

OBJECTIVE

To review clinical trials with fluoroquinolones and the pharmacokinetic and pharmacodynamic parameters predictive of clinical and microbiologic outcomes and resistance. Data on fluoroquinolones are summarized and the premise that a single AUIC target >125 may be used for all fluoroquinolones against all target organisms is examined.

DATA SOURCES

Primary articles were identified by a MEDLINE search (1966-February 2002) and through secondary sources.

STUDY SELECTION AND DATA EXTRACTION

All of the articles identified from the data sources were evaluated and all information deemed relevant was included.

DATA SYNTHESIS

The fluoroquinolones exhibit concentration-dependent killing. This effect clearly depends upon concentrations achieved and outcomes depend upon endpoints established by individual investigators. With AUIC values <60, the actions of fluoroquinolones are essentially bacteriostatic; any observed bacterial killing is the combined effect of low concentrations in relation to minimum inhibitory concentration and the action of host factors such as neutrophils and macrophages. AUIC values >100 but <250 yield bacterial killing at a slow rate, but usually by day 7 of treatment. AUICs >250 produce rapid killing, and bacterial eradication occurs within 24 hours. Disagreements regarding target endpoints are the expected consequences of comparing microbial and clinical outcomes across animal models, in vitro experiments (Part 1), and humans when the endpoints are clearly not equivalent. Careful attention to time-related events such as speed of bacterial killing versus global endpoints such as bacteriologic cure allows optimal break points to be defined.

CONCLUSIONS

Evidence from human trials favors the use of AUIC values >250 for rapid bactericidal action, regardless of whether the organism is gram-negative or gram-positive.

Clinical and molecular epidemiology of quinolone-resistant Escherichia coli isolated from urinary tract infection

Since the use of fluoroquinolone antibiotic in clinical practice was introduced about a decade ago, quinolone-resistant E. coli (QREC) strains are being isolated with increasing frequency. From 1996 to 2000, 297 cases of urinary tract infection (UTI) due to QREC were observed in our hospital; 218 episodes (73.5%) were community acquired. The incidence of QREC UTIs increased steadily from 14.4% to 21.3% during 5 years when we compared the clinical characteristics of 60 QREC UTI with those of 80 quinolone-susceptible E. coli UTIs. Significant differences in susceptibility to various antibiotics were observed between the QREC and QSEC strains of E. coli. The multidrug resistance rate of QREC was much higher (38.3%) than those of quinolone susceptible isolates (18.8%). Prior fluoroquinolone use (p = 0.05), old age (p = 0.001), and a vegetative state (p = 0.03) were the independent risk factors for the acquisition of QREC UTI. The outcome of E. coli UTI is dependent on quinolone resistance. Thirty-day mortality was higher in QREC UTI patients, probably due to aggravation of underlying illness, but not quinolone resistance. On the basis of PFGE analysis, although some clustering was found in the hospital, genomic diversity was found among both the community and nosocomial strains. The increased frequency of QREC UTIs is thus not due to transmission of resistant strains but probably results from the selection of resistant strains from the endogenous flora of patients.

Maintaining fluoroquinolone class efficacy: review of influencing factors

Previous experience with antimicrobial resistance has emphasized the importance of appropriate stewardship of these pharmacotherapeutic agents. The introduction of fluoroquinolones provided potent new drugs directed primarily against gram-negative pathogens, while the newer members of this class demonstrate more activity against gram-positive species, including Streptococcus pneumoniae. Although these agents are clinically effective against a broad range of infectious agents, emergence of resistance and associated clinical failures have prompted reexamination of their use. Appropriate use revolves around two key objectives: 1) only prescribing antimicrobial therapy when it is beneficial and 2) using the agents with optimal activity against the expected pathogens. Pharmacodynamic principles and properties can be applied to achieve the latter objective when prescribing agents belonging to the fluoroquinolone class. A focused approach emphasizing "correct-spectrum" coverage may reduce development of antimicrobial resistance and maintain class efficacy.

Characterization of Pseudomonas aeruginosa isolates: occurrence rates, antimicrobial susceptibility patterns, and molecular typing in the global SENTRY Antimicrobial Surveillance Program, 1997-1999

During 1997-1999, a total of 70,067 isolates (6631 Pseudomonas aeruginosa isolates) were analyzed in the SENTRY program by geographic region and body site of infection. The respiratory tract was the most common source of P. aeruginosa. P. aeruginosa isolation rates increased during the study interval. Europe was the only region to show a significant decline in beta-lactam and aminoglycoside susceptibility rates. There was a reduction in the rates of susceptibility of Canadian isolates to imipenem and of Latin American isolates to meropenem. A total of 218 multidrug-resistant P. aeruginosa isolates (MDR-PSA; resistant to piperacillin, ceftazidime, imipenem, and gentamicin) were observed; MDR-PSA occurrence rates (percentages of all isolates) ranged from 8.2% (Latin America) to 0.9% (Canada). No antimicrobial inhibited >50% of MDR-PSA strains. Molecular characterization of selected, generally resistant strains was performed. Isolates showing unique ribogroups were found in Europe, Latin America, and the United States, but clonal spread was documented in several medical centers.

A risk-benefit assessment of levofloxacin in respiratory, skin and skin structure, and urinary tract infections

As a class, the quinolone antibacterials can no longer be assumed to be both effective and relatively free of significant adverse effects. Recent safety issues with newer generation fluoroquinolones, and concerns regarding drug-use associated bacterial resistance have made all drugs in this class subject to intense scrutiny and further study. Levofloxacin is a second generation fluoroquinolone with a post marketing history of well tolerated and successful use in a variety of clinical situations. Quinolones as a class cause a variety of adverse effects, including phototoxicity, seizures and other CNS disturbances, tendonitis and arthropathies, gastrointestinal effects, nephrotoxicity, prolonged QTc interval and torsade de pointes, hypo- or hyperglycaemia, and hypersensitivity reactions. Levofloxacin has been involved in only a few case reports of adverse events, which include QTc prolongation, seizures, glucose disturbances, and tendonitis. Levofloxacin has been shown to be effective at dosages of 250mg to 500mg once-daily in clinical trials in the management of acute maxillary sinusitis, acute bacterial exacerbations of chronic bronchitis, community-acquired pneumonia, skin and skin structure infections, and urinary tract infections. There are data suggesting that levofloxacin may promote fluoroquinolone resistance among the Streptococcus pneumoniae, and that clinical failures may result from this therapy. Other data suggest that fluoroquinolones with lower potency against Pseudomonas aeruginosa than ciprofloxacin, such as levofloxacin, may drive class-wide resistance to this pathogen. Levofloxacin is an effective drug in many clinical situations, but its cost is significantly higher than amoxicillin, erythromycin, or first and second generation cefalosporins. Because of the propensity to select for fluoroquinolone resistance in the pneumococcus and potentially other pathogens, levofloxacin should be an alternative agent rather than a drug-of-choice in routine community-acquired respiratory tract, urinary tract, and skin or skin structure infections. In areas with increasing pneumococcal beta-lactam resistance, levofloxacin may be a reasonable empiric therapy in community-acquired respiratory tract infections. Similarly, in patients with risk factors for infectious complications or poor outcome, levofloxacin may be an excellent empiric choice in severe community-acquired respiratory tract infections, urinary tract infections, complicated skin or skin structure infections, and nosocomial respiratory and urinary tract infections. Better clinical data are needed to identify the true place in therapy of the newer fluoroquinolones in common community-acquired and nosocomial infections. Until then, these agents, including levofloxacin, might best be reserved for complicated infections, infection recurrence, and infections caused by beta-lactam or macrolide-resistant pathogens.

Use of norfloxacin in poultry production in the eastern province of Saudi Arabia and its possible impact on public health

Samples of market-ready chicken muscle and liver from 32 local broiler farms were first screened for antibiotic residues by microbiological assay. The antibiotic-residue-positive muscles and livers from 22 farms were further analysed for norfloxacin (NFX) residues by high performance liquid chromatography. NFX was detected in 35.0% and 56.7% of raw antibiotic-residue-positive muscles and livers, respectively. The NFX-positive muscles and livers were respectively obtained from 11 (50.0%) and 14 (63.6%) of the 22 antibiotic-residue-positive farms. Since the maximum residue limit (MRL) for NFX has not yet been fixed, the MRL for enrofloxacin was used in the study. All NFX-positive farms had mean raw tissue levels, which were 2.7- to 34.3-fold higher than the MRL. Although cooking markedly reduced NFX tissue concentrations, mean detectable levels remained above MRL in large proportions of NFX-positive samples and farms. Susceptibility patterns of Enterobacteriaceae isolates from chicken and human patients to NFX showed alarmingly high rates of resistance in chicken isolates especially among Escherichia coli (45.9%) and Pseudomonas spp. (70.6%) compared with patients' isolates (10.5% and 18.2%, respectively). The study reveals widespread misuse of NFX in the local poultry industry, which may pose a major risk to public health including possible stimulation of bacterial resistance and hypersensitivity reactions to fluoroquinolones. More prudent use of fluoroquinolones in food-producing animals is therefore recommended. Further, there is a need to establish MRL values for NFX.