Evaluation of the Treatment of Vancomycin-Resistant Enterococcal Urinary Tract Infections in a Large Academic Medical Center

Antimicrobial pharmacokinetics and preclinical in vitro models to support optimized treatment approaches for uncomplicated lower urinary tract infections

INTRODUCTION

Urinary tract infections (UTIs) are extremely common. Millions of people, particularly healthy women, are affected worldwide every year. One-in-two women will have a recurrence within 12-months of an initial UTI. Inadequate treatment risks worsening infection leading to acute pyelonephritis, bacteremia and sepsis. In an era of increasing antimicrobial resistance, it is critical to provide optimized antimicrobial treatment.

AREAS COVERED

Literature was searched using PubMed and Google Scholar (up to 06/2020), examining the etiology, diagnosis and oral antimicrobial therapy for uncomplicated UTIs, with emphasis on urinary antimicrobial pharmacokinetics (PK) and the application of dynamic in vitro models for the pharmacodynamic (PD) profiling of pathogen response.

EXPERT OPINION

The majority of antimicrobial agents included in international guidelines were developed decades ago without well-described dose-response relationships. Microbiology laboratories still apply standard diagnostic methodology that has essentially remained unchanged for decades. Furthermore, it is uncertain how relevant standard in vitro susceptibility is for predicting antimicrobial efficacy in urine. In order to optimize UTI treatments, clinicians must exploit the urine-specific PK of antimicrobial agents. Dynamic in vitro models are valuable tools to examine the PK/PD and urodynamic variables associated with UTIs, while informing uropathogen susceptibility reporting, optimized dosing schedules, clinical trials and treatment guidelines.

Enterococcal Meningitis/Ventriculitis: A Tertiary Care Experience

Context:

Enterococcal meningitis is very rare among bacterial meningitis and has variable clinical outcomes.

Aims:

The purpose of the current study is to evaluate clinical features, therapeutic options with susceptibility profile, and outcomes of enterococcal meningitis in a tertiary care hospital.

Settings and Design:

We retrospectively reviewed medical records of all patients with enterococcal meningitis over the periods of 4 years.

Subjects and Methods:

The clinical and laboratory data of all patients with enterococcal meningitis were evaluated between 2013 and 2016.

Results:

Six cases of enterococcal meningitis were found (three infant and three adults). All patients developed meningitis after neurosurgical procedures, and majority of patients (four out of six) had central nervous system (CNS) devices in situ at the time of development of meningitis. The causative organism isolated from cerebrospinal fluid (CSF) culture of all patients was Enterococcus species only. All Enterococcus spp. were resistant to ampicillin, Amoxicillin-clavulanate, and oxytetracycline and two isolates were also resistant to vancomycin. Four patients with vancomycin-sensitive Enterococcus spp. were treated with vancomycin alone for mean periods of 18 days (14–21 days). One patient with vancomycin-resistant Enterococcus (VRE) meningitis was treated with linezolid alone, and another one requires combination with rifampicin to achieve microbiological clearance of CSF. CNS devices were removed in all patients. No mortality was reported in current case series.

Conclusions:

Enterococcal meningitis is very uncommon, mostly associated with neurosurgical intervention. Early treatment is associated with favorable outcomes. Removal of CNS devices is recommended to achieve a clinical cure.

Utility of catheterized specimens in reducing overdiagnosis of urinary tract infections in women

AIMS

To evaluate the utility of catheterized samples in reducing overdiagnosis of UTI based on voided specimens among patients presenting with a range of urinary symptoms. We also aimed to determine variables that may modify the predictive value of the voided midstream urine culture.

METHODS

Patient charts were reviewed to identify female patients referred to our voiding dysfunction clinic with a range of complaints warranting urine studies (5/2014-8/2016). Patients with a positive voided urine culture who also had a catheterized urine culture in our system were included. Multiple logistic regression analysis was performed to identify patient characteristics associated with a negative catheterized specimen despite a positive voided specimen.

RESULTS

One hundred and seven women were included in the study. Eighty percent of the cohort was post-menopausal. Although all patients had positive voided specimens, only 53 (49.5%) had positive catheterized specimens. On multivariate analysis negative nitrites on clean catch UA was a significant predictor of a negative catheterized sample (adjusted OR 8.9, 95%CI 2.2-43.7, P = 0.003). WBC/HPF <10 on clean catch UA trended towards significance (adjusted OR 4.72, 95%CI 1.1-26.1, P = 0.05).

CONCLUSIONS

Relying on clean catch urine samples may lead to significant over-diagnosis of UTIs. Our study suggests that in female patients who have vague symptoms of UTI, obtaining catheterized specimens may be beneficial in avoiding the overdiagnosis of UTIs and the overuse of antibiotics. Larger, prospective studies testing our hypothesis are necessary, and would greatly assist in establishing clinical practices that reduce the amount of antibiotics inappropriately prescribed.

Inappropriate Management of Asymptomatic Patients With Positive Urine Cultures: A Systematic Review and Meta-analysis

BACKGROUND

Mismanagement of asymptomatic patients with positive urine cultures (referred to as asymptomatic bacteriuria [ASB] in the literature) promotes antimicrobial resistance and results in unnecessary antimicrobial-related adverse events and increased health care costs.

METHODS

We conducted a systematic review and meta-analysis of studies that reported on the rate of inappropriate ASB treatment published from 2004 to August 2016. The appropriateness of antimicrobial administration was based on guidelines published by the Infectious Diseases Society of America.

RESULTS

A total of 2142 nonduplicate articles were identified, and among them 30 fulfilled our inclusion criteria. The pooled prevalence of antimicrobial treatment among 4129 cases who did not require treatment was 45% (95% CI, 39-50). Isolation of gram-negative pathogens (odds ratio [OR], 3.58; 95% CI, 2.12-6.06), pyuria (OR, 2.83; 95% CI, 1.9-4.22), nitrite positivity (OR, 3.83; 95% CI, 2.24-6.54), and female sex (OR, 2.11; 95% CI, 1.46-3.06) increased the odds of receiving treatment. The rates of treatment were higher in studies with ≥100 000 cfu/mL cutoff values compared with <10 000 cfu/mL for bacterial growth (P, .011). The implementation of educational and organizational interventions designed to eliminate the overtreatment of ASB resulted in a median absolute risk reduction of 33% (rangeARR, 16-36%, medianRRR, 53%; rangeRRR, 25-80%).

CONCLUSION

The mismanagement of ASB remains extremely frequent. Female sex and the overinterpretation of certain laboratory data (positive nitrites, pyuria, isolation of gram-negative bacteria and cultures with higher microbial count) are associated with overtreatment. Even simple stewardship interventions can be particularly effective, and antimicrobial stewardship programs should focus on the challenge of differentiating true urinary tract infection from ASB.

Severity of drug resistance and co-existence of Enterococcus faecalis in diabetic foot ulcer infections

The genes encoding aminoglycoside resistance in Enterococcus faecalis may promote collateral aminoglycoside resistance in polymicrobial wounds. We studied a total of 100 diabetic foot ulcer samples for infection and found 60 samples to be polymicrobial, 5 to be monomicrobial, and 35 samples to be culture negative. A total of 65 E. faecalis isolates were screened for six genes coding for aminoglycoside resistance, antibiotic resistance patterns, and biofilm production. Infectious Diseases Society of America/International Working Group on the Diabetic Foot system was used to classify the wound ulcers. Majority of the subjects with culture-positive wound were recommended conservative management, while 14 subjects underwent amputation. Enterococcal isolates showed higher resistance for erythromycin, tetracycline, and ciprofloxacin. Isolates from grade 3 ulcer showed higher frequency of aac(6')-Ie-aph(2″)-Ia, while all the isolates were negative for aph(2″)-Ib, aph(2″)-Ic, and aph(2″)-Id. The isolates from grade 3 ulcers showed higher resistance to aminoglycosides as well as teicoplanin and chloramphenicol. All the 39 biofilm producers were obtained from polymicrobial wound and showed higher resistance when compared to biofilm non-producers. Higher frequency of isolates carrying aac(6')-Ie-aph(2″)-Ia in polymicrobial community showing resistance to key antibiotics suggests widespread distribution of aminoglycoside-resistant E. faecalis and their role in worsening diabetic foot ulcers.

Revisiting Nitrofurantoin for Vancomycin Resistant Enterococci

INTRODUCTION

Enterococcal infection has emerged as a major therapeutic challenge. Emergence of High Level Aminoglycoside Resistance (HLAR) and Vancomycin-Resistant Enterococcus (VRE) has further limited the drug therapy in enterococcal infections. However, nitrofuratoin being an old drug reported to have less resistance in comparison to the other classes of antimicrobial agents.

AIM

To detect susceptibility of nitrofurantoin against VRE isolates from Urinary Tract Infection (UTI) of outdoor and indoor patient departments.

MATERIALS AND METHODS

An observational study was carried out at a tertiary care hospital in New Delhi over a period of six months (from November 2015 to April 2016). A total of 14,714 urine samples were collected and processed from the patients symptomatic for UTI. The enterococcal isolates were identified and confirmed by standard phenotypic tests. The antimicrobial susceptibility tests of isolated organisms were performed by Kirby-Bauer Disc Diffusion Method as per Clinical and Laboratory Standards Institute (CLSI) 2015 guidelines. The Wilcoxon rank-sum (Mann-Whitney) test was used to compare continuous variables. Chi-square or Fisher's exact tests were used to compare categorical variables. p<0.05 was considered as significant.

RESULTS

A total of 70 enterococci species {Enterococcus faecalis (n=9), Enterococcus faecium, (n=61)} were isolated. Twenty six out of 70 isolates were observed resistant to vancomycin. Among 26 VRE, 21(80.76%) were susceptible to nitrofurantoin. Both the species {E. faecalis (80.32%) and E. faecium (88.8%)} were uniformly susceptible to nitrofurantoin.

CONCLUSION

Nitrofurantoin has retained antimicrobial efficacy against emerging VRE in vitro and can be used for treatment of enterococcal urinary tract infections.

Vancomycin resistant enterococci in urine cultures: Antibiotic susceptibility trends over a decade at a tertiary hospital in the United Kingdom

Purpose

Enterococci are a common cause of urinary tract infection and vancomycin-resistant strains are more difficult to treat. The purpose of this surveillance program was to assess the prevalence of and determine the risk factors for vancomycin resistance in adults among urinary isolates of Enterococcus sp. and to detail the antibiotic susceptibility profile, which can be used to guide empirical treatment.

Materials and Methods

From 2005 to 2014 we retrospectively reviewed 5,528 positive Enterococcus sp. urine cultures recorded in a computerized laboratory results database at a tertiary teaching hospital in Cambridge, United Kingdom.

Results

Of these cultures, 542 (9.8%) were vancomycin resistant. No longitudinal trend was observed in the proportion of vancomycin-resistant strains over the course of the study. We observed emerging resistance to nitrofurantoin with rates climbing from near zero to 40%. Ampicillin resistance fluctuated between 50% and 90%. Low resistance was observed for linezolid and quinupristin/dalfopristin. Female sex and inpatient status were identified as risk factors for vancomycin resistance.

Conclusions

The incidence of vancomycin resistance among urinary isolates was stable over the last decade. Although resistance to nitrofurantoin has increased, it still serves as an appropriate first choice in uncomplicated urinary tract infection caused by vancomycin-resistant Enterococcus sp.

Approach to a positive urine culture in a patient without urinary symptoms

Asymptomatic bacteriuria (ASB) is a condition in which bacteria are present in a noncontaminated urine sample collected from a patient without signs or symptoms related to the urinary tract. ASB must be distinguished from symptomatic urinary tract infection (UTI) by the absence of signs and symptoms compatible with UTI or by clinical determination that a nonurinary cause accounts for the patient's symptoms. The overall purpose of this review is to promote an awareness of ASB as a distinct condition from UTI and to empower clinicians to withhold antibiotics in situations in which antimicrobial treatment of bacteriuria is not indicated.

Vancomycin resistance has no influence on outcomes of enterococcal bacteriuria

BACKGROUND

Infections with vancomycin-resistant enterococci (VRE) are a growing concern in hospitals. The impact of vancomycin resistance in enterococcal urinary tract infection is not well-defined.

AIM

To describe the epidemiology of enterococcal bacteriuria in a hospital and compare the clinical picture and patient outcomes depending on vancomycin resistance.

METHODS

This was a 6-month prospective cohort study of hospital patients who were admitted with or who developed enterococcal bacteriuria in a 1250-bed tertiary care hospital. We examined clinical presentation, diagnostic work-up, management, and outcomes.

FINDINGS

We included 254 patients with enterococcal bacteriuria; 160 (63%) were female and median age was 65 years (range: 17-96). A total of 116 (46%) bacteriurias were hospital-acquired and 145 (57%) catheter-associated. Most patients presented with asymptomatic bacteriuria (ASB) (119; 47%) or pyelonephritis (64; 25%); 51 (20%) had unclassifiable bacteriuria and 20 (8%) had cystitis. Secondary bloodstream infection was detected in 8 (3%) patients. Seventy of 119 (59%) with ASB received antibiotics (mostly vancomycin). There were 74 (29%) VRE bacteriurias. VRE and vancomycin-susceptible enterococci (VSE) produced similar rates of pyelonephritis [19 (25%) vs 45 (25%); P = 0.2], cystitis, and ASB. Outcomes such as ICU transfer [10 (14%) VRE vs 17 (9%) VSE; P = 0.3], hospital length of stay (6.8 vs 5.0 days; P = 0.08), and mortality [10 (14%) vs 13 (7%); P = 0.1] did not vary with vancomycin susceptibility.

CONCLUSIONS

Vancomycin resistance did not affect the clinical presentation nor did it impact patient outcomes in this cohort of inpatients with enterococcal bacteriuria. Almost half of our cohort had enterococcal ASB; more than 50% of these asymptomatic patients received unnecessary antibiotics. Antimicrobial stewardship efforts should address overtreatment of enterococcal bacteriurias.