Impact of the fluoroquinolones on gastrointestinal flora

Predictors of Rectal Carriage of Carbapenem-Resistant Enterobacteriaceae (CRE) among Patients with Known CRE Carriage at Their Next Hospital Encounter

Background.

Carbapenem-resistant Enterobacteriaceae (CRE) are important extremely drug-resistant pathogens that have emerged during the past decade. Early identification and isolation of carriers are key components of an effective infection control strategy in healthcare facilities. Very little is known about the natural history of CRE carriage. We aimed to determine the predictors of a positive CRE rectal screen test among patients with known CRE carriage screened at their next hospital encounter.

Methods.

A case-control study was conducted. Sixty-six patients who tested positive for CRE carriage were surveyed for CRE rectal carriage at the next hospital encounter; screen-positive patients were compared with screen-negative control patients. Data were extracted from the patients' medical records and from the hospital computerized database.

Results.

Twenty-three case patients and 43 control patients were identified. Predictors for a positive CRE rectal carriage test were (1) prior fluoroquinolone use (odds ratio [OR], 4.27; 95% confidence interval [CI], 1.10–16.6), (2) admission from an institution or another hospital (OR, 4.04; 95% CI, 1.33–12.37), and (3) time interval less than or equal to 3 months since the first positive CRE test (OR, 3.59; 95% CI, 1.24–10.37). Among patients with no predictor variables, the likelihood of having a positive screen test at the next hospital encounter was 1/7. If they had at least 1 predictor, the likelihood increased to 1/2.

Conclusions.

Prior fluoroquinolone use, transfer from another healthcare facility, and admission less than or equal to 3 months since the first CRE isolation are predictors of persistent CRE rectal carriage. These predictors can be used in designing CRE prevention strategies.

Risk factors for prolonged carriage of vancomycin-resistant Enterococcus faecium among patients in intensive care units: a case-control study

OBJECTIVES

The aim of this study was to identify the risk factors for prolonged carriage of vancomycin-resistant Enterococcus faecium (VREF) in intensive care units (ICUs).

METHODS

A retrospective case-control study was performed in the ICUs of a university hospital in Korea from September 2006 to July 2009. VREF carriage was identified through weekly active surveillance rectal cultures. Clinical characteristics and the risk factors for VREF acquisition were compared between cases with prolonged VREF carriage (≥ 5 weeks, n = 58) and controls with shorter VREF carriage (<3 weeks, n = 36) in a multivariate logistic regression model. The effect of vancomycin consumption on vancomycin-resistant enterococci (VRE) colonization pressure was investigated using time-series analysis with an autoregressive error model.

RESULTS

Out of a total of 6327 rectal swab cultures examined, 1915 (30.3%) specimens from 266 patients were positive for VREF. The weekly VRE colonization pressure ranged from 0.77% to 42.42%. Vancomycin use after VREF acquisition significantly increased VREF carriage (adjusted odds ratio = 4.09; 95% confidence interval = 1.32-12.65). The case group had higher in-hospital mortality than the control group [21 (36.2%) versus 4 (11.1%), P = 0.007]. Increment of VRE colonization pressure was significantly associated with vancomycin consumption of 1week before (i.e. time t - 1) (P = 0.0028) and moderately associated with that of the corresponding week (i.e. time t) (P = 0.0595).

CONCLUSIONS

Vancomycin use in patients with VREF colonization might prolong the duration of carriage. Restriction of vancomycin use should be strengthened in these patients through infection control measures.

Treatment with fluoroquinolones or with beta-lactam-beta-lactamase inhibitor combinations is a risk factor for isolation of extended-spectrum-beta-lactamase-producing Klebsiella species in hospitalized patients

Antibiotic exposure exerts strong selective pressure and is an important modifiable risk factor for antibiotic resistance. We aimed to identify the role of various antibiotics as risk factors for the isolation of extended-spectrum-beta-lactamase (ESBL)-producing Klebsiella spp. in hospitalized patients at a tertiary-care hospital. A parallel multivariable model was created to compare two groups of cases with either nosocomially acquired ESBL- or non-ESBL-producing Klebsiella spp. to a common control group of hospitalized patients (a case-case-control design). Seventy-eight ESBL cases, 358 non-ESBL cases, and 444 controls were analyzed. Significant factors associated with the isolation of Klebsiella spp. were an age of >65 years, transfer from a health care facility, an intensive care unit (ICU) stay, and the presence of a comorbid malignancy or lung, hepatic, or renal disease. A propensity score was generated from the above, and our ability to discriminate between Klebsiella cases and controls (area under the receiver-operating-characteristic [ROC] curve, 0.78) was good. The ESBL phenotype was tightly linked with fluoroquinolone resistance (95% versus 18%, P < 0.001). Factors associated with isolation of ESBL Klebsiella spp. in a multivariable analysis, adjusting for the propensity score, included exposure to beta-lactam-beta-lactamase inhibitor combinations (odds ratio [OR], 10.17; 95% confidence interval [CI], 1.19 to 86.92) and to fluoroquinolones (OR, 2.86; 95% CI, 1.37 to 5.97). Exposure to broad-spectrum cephalosporins was statistically associated with ESBL Klebsiella spp. only among the subgroup of patients not treated with fluoroquinolones. In our institution, where the ESBL-producing-Klebsiella phenotype is coselected with fluoroquinolone resistance, fluoroquinolone and beta-lactam-beta-lactamase inhibitor combinations, rather than cephalosporins, are the main risk factors for ESBL isolates. Formulary interventions to limit the spread of ESBL-producing isolates should be tailored to each setting.

Febrile neutropenia: highlighting the role of prophylactic antibiotics and granulocyte colony-stimulating factor during standard dose chemotherapy for solid tumors

The prevention of chemotherapy-induced febrile neutropenia is important as it reduces hospitalization and is likely to improve quality of life. Several prophylactic strategies are available, although their use in patients with an anticipated short duration of neutropenia is controversial and not recommended. This paper presents the results of a review of the literature on the efficacy and cost-effectiveness of prophylactic antibiotics and/or granulocyte colony-stimulating factor, and also discusses the recommendations in current guidelines in view of recent publications. Both primary prophylactic granulocyte colony-stimulating factor and prophylactic antibiotics reduce the risk of febrile neutropenia considerably, and the addition of prophylactic granulocyte colony-stimulating factor to antibiotics is even more effective. As antibiotics, however, give rise to antimicrobial resistance and granulocyte colony-stimulating factor is expensive, tailoring of prophylaxis is clearly needed. This will increase the absolute clinical and economical benefits of prophylaxis. Patient-related, treatment-related and disease-related factors enhancing the risk of febrile neutropenia are discussed, including the, underrated, high risk of febrile neutropenia specifically in the first cycles of chemotherapy. Half of the patients developing febrile neutropenia during treatment do so in the first cycle of chemotherapy, which favors primary prophylaxis. The efficacy of secondary prophylaxis is not well documented. Finally, new interesting agents in the treatment and supportive care of solid tumors have become available, and these are discussed in relation to the incidence and prevention of febrile neutropenia.

Campylobacter and fluoroquinolones: a bias data set?

There is no universally accepted standard method for the isolation of Campylobacter spp. and it is considered that currently available isolation media are not yet optimal for the recovery of Campylobacter spp. from a range of sample types. Almost all methods incorporate antibiotics into the isolation media to inhibit growth of other bacteria within the sample. It is established that the incorporation of such antibiotics into isolation media will inhibit the growth of some Campylobacter spp. as well as other bacteria. The results of the use of such suboptimal isolation methods are that the isolates which 'survive' the isolation procedure will be those which: (i) are able to 'out compete' the rest of the bacteria in the sample, i.e. they are able to grow faster; (ii) are resistant to the antibiotics used in the isolation media; and (iii) are randomly selected by the laboratory technician as being a 'typical'Campylobacter spp. It is clear that such a procedure is intrinsically biased and will mean that species resistant to the antibiotics used in the media will be isolated. This introduces real doubt that the bacteria isolated are truly representative of those initially found on the sample. It is also becoming clear that Campylobacter spp. are rather difficult to isolate as pure cultures and many are in fact mixtures of more than one strain. Again this introduces great uncertainty as to the prevalence and distribution of respective species from the different sample types. This is especially true when considering isolation of Campylobacter spp. causing disease in man as there is no certainty that the selected isolate is that which was responsible for disease. The incorporation of antibiotics into the isolation media not only introduces the issue of species bias but perhaps more importantly exposes the Campylobacter spp. to a cocktail of antibiotics thereby providing the potential for them to 'switch on' antibiotic resistance mechanisms. It might be argued that this has always been the case for isolation of Campylobacter spp., however, we know that the antibiotic cocktails used in media over the last 10 years have changed and indeed there was a time when the filtration protocol which didn't use antibiotics was more widely used. As most reports in the literature do not state what methods were used to isolate Campylobacter spp. it is not possible to quantify any relationship between antibiotics used in the isolation media and susceptibility data. An approved method for Campylobacter susceptibility testing was not available until May 2002, all data generated prior to this date will have been generated using non-standard methods. As tremendous variability in the reproducibility data for Campylobacter spp. was observed during the development of the standard agar dilution susceptibility method, data generated with disk diffusion and broth microdilution methods must be considered with caution. It has been shown that, compared with the conventional agar dilution method, the E-test tends to give rise to lower minimal inhibitory concentrations (MICs) for sensitive strains and higher MICs for resistant strains. There are no recommended antibiotic breakpoint concentrations for Campylobacter spp. A breakpoint is used to separate sensitive from resistant strains of bacteria and is thus crucial to any discussion of antibiotic resistance. This discussion is further complicated by introduction of the terms microbiological and clinical breakpoints. While a microbiological breakpoint can be a useful parameter with regard to identifying resistance factors it cannot on its own be used to predict whether that bacteria will respond to treatment from an appropriate antibiotic. Predicting clinical response is a function of the clinical breakpoint which considers the pharmacokinetic profile of the antimicrobial compound, i.e. the concentration of the antimicrobial compound in the body and the MIC. The National Committee for Clinical Laboratory Standards (NCCLS) uses microbiological, pharmacokinetic and clinical data to establish breakpoints, without c and clinical data to establish breakpoints, without such considerations it is not possible to consider what is truly clinically sensitive and resistant. There are no reported studies that have systematically determined appropriate breakpoints for Campylobacter, there are data however, which relate MICs to clinical outcome. It is without dispute that microbiological resistance in Campylobacter spp. occurs as a result of mutation in the gyrA gene with single point mutations most frequently causing a four- to eightfold shift in the MIC. What is also clear is that if a high enough concentration of antimicrobial relative to MIC of the infecting organism can be achieved not only will the parent organism be killed but also the 'resistant' mutant. Considering the above and the concentrations of ciprofloxacin achieved in the gastro-intestinal tract it is not surprising that clinical cure can be demonstrated for organisms with an MIC of 32 microg ml(-1).

Vancomycin-resistant enterococci: 15 years and counting

We review the history of vancomycin-resistant enterococci (VRE) and propose a causal model illustrating the roles of exposure to VRE reservoirs, patient characteristics, antimicrobial exposure, and prevalence of VRE in the progression from potential VRE reservoirs to active disease in hospitalized patients. Differences in VRE colonization and VRE infection are discussed with respect to hospital surveillance methodology and implications for interventions. We further document clonal transmission of VRE in a large, urban, teaching hospital and demonstrate VRE susceptibility to a wide array of antimicrobial agents. This model can guide the identification of mutable factors that are focal points for intervention.

Absorption of ofloxacin isomers in the rat small intestine

Ofloxacin, a chiral fluoroquinolone, possesses two optical isomers. The antibacterial activity of S-(-)-ofloxacin is 8 to 128 times higher than that of R-(+)-ofloxacin. In the rat, a saturable absorption process has been described for racemic ofloxacin. In the present study we investigated the mechanism underlying the in vivo intestinal absorption of ofloxacin enantiomers in the rat. Blood samples were collected from the portal vein. Our results show that the intestinal absorption of ofloxacin isomers is pH dependent, both enantiomers being best absorbed at neutral pH. S-(-)-Ofloxacin seems to have a greater affinity for the intestinal transporter (initial concentrations at 5 min [C(init)] are 0.17 +/- 0.04 and 0.12 +/- 0.03 microg/ml for S-(-)- and R-(+)-ofloxacin, respectively). Dipeptides fail to modify ofloxacin absorption, but amino acids reduce both isomers' absorption (C(init) is reduced by 53 and 33% with glycine for S-(-)- and R-(+)-ofloxacin, respectively, and by 59 and 42% with L-leucine). Gamma amino butyric acid interferes with the absorption of ofloxacin isomers, but less seriously than do amino acids. Furthermore, ofloxacin competes with other fluoroquinolones or P-glycoprotein substrates for a common secretory pathway, resulting in an increased rate of absorption for both ofloxacin isomers; this is probably an indirect result of their reduced efflux from the apical side of intestinal cells.

Enoxacin: a reappraisal of its clinical efficacy in the treatment of genitourinary tract infections

Enoxacin is a 6-fluoronaphthyridinone antibacterial agent with good in vitro activity against Neisseria gonorrhoeae and most Gram-negative urinary tract pathogens. It is less active in vitro against Acinetobacter spp., Pseudomonas aeruginosa, and most Gram-positive bacteria, than against Gram-negative organisms. Enoxacin is rapidly absorbed, with a high oral bioavailability (87 to 91%). Of the absorbed dose, 44 to 56% is excreted unchanged in the urine, with peak urinary concentrations (>500 mg/L within 4 hours) remaining high (>100 mg/L) for up to 24 hours, sufficient to inhibit most urinary tract pathogens. Single (400 mg) and multiple oral dose regimens (100 to 600 mg twice or 3 times daily for 5 to 14 days) of enoxacin are as effective for the treatment of patients with complicated or uncomplicated urinary tract infections as other antibacterial agents such as amoxicillin, cefuroxime axetil, cotrimoxazole (trimethoprim-sulfamethoxazole) or trimethoprim. Noncomparative data suggest that enoxacin is also an effective agent for the treatment of prostatitis. Single 400 mgoral doses of enoxacin produce >/- 95% bacteriological cure rates in gonococcal infections, comparable to those produced by single intramuscular doses of ceftriaxone 250 mg. Perioperative doses of oral enoxacin 200 mg provide effective prophylaxis against postoperative bacteriuria after transurethral resection of the prostate. Concomitant administration of enoxacin with a number of commonly used therapeutic agents (e.g. antacids, methylxanthines, warfarin) affects the pharmacokinetic properties of either enoxacin or the coadministered agents. Enoxacin is reasonably well tolerated, with the incidence of adverse experiences ranging from 0 to 24%. Adverse events are mainly gastrointestinal, neurological or dermatological and resolve with minimal intervention. Overall, although enoxacin exhibits a number of clinical characteristics that are similar to those of other agents for the treatment of genitourinary tract infections, the advantages offered by this agent generally do not outweigh those of alternative fluoroquinolone agents. Thus, it is likely to prove to be yet another addition to the list of agents available for the management of these infections.

Levofloxacin. A review of its antibacterial activity, pharmacokinetics and therapeutic efficacy

Levofloxacin, an oral fluoroquinolone antibacterial agent, is the optical S-(-) isomer of ofloxacin. In vitro it is generally twice as potent as ofloxacin. Levofloxacin is active against most aerobic Gram-positive and Gram-negative organisms and demonstrates moderate activity against anaerobes. Drug penetration into body tissues and fluids is rapid and widespread after oral administration. In clinical trials conducted in Japan, oral levofloxacin has demonstrated antibacterial efficacy against a variety of infections, including upper and lower respiratory tract, genitourinary, obstetric, gynaecological and skin and soft tissues. In comparative trials with ofloxacin, levofloxacin, at half the daily dosage of ofloxacin, showed equivalent efficacy and a reduced incidence of adverse effects in the treatment of lower respiratory tract and complicated urinary tract infections. Levofloxacin has a tolerability profile similar to that of other oral fluoroquinolones, with gastrointestinal and central nervous system effects reported most commonly. Theophylline dosage adjustment does not appear to be necessary in patients receiving concomitant levofloxacin. Coadministration with antacids or with other drugs containing divalent or trivalent cations reduces levofloxacin absorption. Thus, levofloxacin has potential as a broad spectrum antibacterial drug in the treatment of a variety of infections. However, clinical trials recruiting non-Japanese patients are in progress and these results will form a basis on which future recommendations for the broader use of levofloxacin can be made.