Fosfomycin susceptibility among multidrug-resistant, extended-spectrum beta-lactamase-producing, carbapenem-resistant uropathogens

Evaluation of the in vitro susceptibility of clinical isolates of NDM-producing Klebsiella pneumoniae to new antibiotics included in a treatment regimen for infections

Background

Due to the growing resistance to routinely used antibiotics, the search for new antibiotics or their combinations with effective inhibitors against multidrug-resistant microorganisms is ongoing. In our study, we assessed the in vitro drug susceptibility of Klebsiella pneumoniae strains producing New Delhi metallo-β-lactamases (NDM) to antibiotics included in the Infectious Diseases Society of America (IDSA) and European Society of Clinical Microbiology and Infectious Diseases (ESCMID) recommendations.

Methods

A total of 60 strains of NDM-producing K. pneumoniae were obtained from different patients hospitalized at the 4th Military Hospital in Wroclaw between 2019 and 2022 and subjected to drug susceptibility to selected antibiotics, including the effects of drug combinations.

Results

Among the tested antibiotics, the highest sensitivity (100%) was observed for cefiderocol, eravacycline (interpreted according to the European Committee on Antimicrobial Susceptibility Testing [EUCAST]), and tigecycline. Sensitivity to intravenous fosfomycin varied depending on the method used. Using the "strip stacking" method, determining cumulative sensitivity to ceftazidime/avibactam and aztreonam demonstrated 100% in vitro sensitivity to this combination among the tested strains.

Conclusion

The in vitro susceptibility assessment demonstrated that, the best therapeutic option for treating infections caused by carbapenemase-producing strains seems to be a combination of ceftazidime/avibactam with aztreonam. Due to the safety of using both drugs, cost effectiveness, and the broadest indications for use among the tested antibiotics, this therapy should be the first-line treatment for carbapenemase-producing Enterobacterales infections. Nevertheless, a comprehensive evaluation of the efficacy of treating infections caused by NDM-producing K. pneumoniae strains should include not only in vitro susceptibility assessment but also an analysis of clinical cases.

Increased Levels of (p)ppGpp Correlate with Virulence and Biofilm Formation, but Not with Growth, in Strains of Uropathogenic Escherichia coli

Urinary tract infections are one of the most frequent bacterial diseases worldwide. UPECs are the most prominent group of bacterial strains among pathogens responsible for prompting such infections. As a group, these extra-intestinal infection-causing bacteria have developed specific features that allow them to sustain and develop in their inhabited niche of the urinary tract. In this study, we examined 118 UPEC isolates to determine their genetic background and antibiotic resistance. Moreover, we investigated correlations of these characteristics with the ability to form biofilm and to induce a general stress response. We showed that this strain collection expressed unique UPEC attributes, with the highest representation of FimH, SitA, Aer, and Sfa factors (100%, 92.5%, 75%, and 70%, respectively). According to CRA (Congo red agar) analysis, the strains particularly predisposed to biofilm formation represented 32.5% of the isolates. Those biofilm forming strains presented a significant ability to accumulate multi-resistance traits. Most notably, these strains presented a puzzling metabolic phenotype-they showed elevated basal levels of (p)ppGpp in the planktonic phase and simultaneously exhibited a shorter generation time when compared to non-biofilm-forming strains. Moreover, our virulence analysis showed these phenotypes to be crucial for the development of severe infections in the Galleria mellonella model.

Assessment of the Susceptibility of Clinical Gram-Negative and Gram-Positive Bacterial Strains to Fosfomycin and Significance of This Antibiotic in Infection Treatment

Multidrug resistance of bacteria has prompted intensive development work on new medicines, but also the search for effective options among the oldest antibiotics. Although intravenous fosfomycin (IVFOS) seems to be an interesting proposal, the recommended agar dilution method for susceptibility determination poses a major problem in routine diagnostic testing. As a consequence, there is a lack of comprehensive data on the frequency of isolation of susceptible or resistant strains. This fact triggered the disposition of EUCAST concerning the revision of IVFOS breakpoints (BPs), including withdrawal of BPs for Enterobacterales (excluding E. coli) and coagulase-negative staphylococci. Therefore, the aim of this study was to assess the activity of fosfomycin against numerous clinical strains using recommended methods. Materials and methods: A total of 997 bacterial strains were tested from the following genera: Enterobacterales, Pseudomonas spp., Staphylococcus spp., Acinetobacter spp., and Enterococcus spp., for which there are currently no BPs. The strains were isolated from various clinical materials from patients hospitalized in five hospitals. During the investigation, the recommended agar dilution method was used. Susceptibility to other antibiotics and resistance mechanisms were determined using an automatic method (Phoenix) the disk diffusion method, and E-tests. MIC values of fosfomycin were estimated for all strains and for susceptible and multidrug-resistant (MDR) strains individually. Results: Except for Acinetobacter and Enterococcus, 83% of the strains were susceptible to IVFOS, including the largest percentage of S. aureus and E. coli. Klebsiella spp. turned out to be the least susceptible strains (66%). The highest proportion of susceptibility to fosfomycin was found among strains that were sensitive to other antibiotics (80.9%), and the lowest was found among Gram-negative carbapenemase-producing bacteria (55.6%) and ESBL+ bacteria (61.6%). The MIC evaluation revealed the lowest MIC₅₀ and MIC₉₀ values for S. aureus (0.5 mg/L and 1 mg/L, respectively) and E. coli (4 mg/L and 32 mg/L, respectively). The highest values of MIC₅₀ were found for Acinetobacter spp. (256 mg/L), while the highest values of MIC₉₀ were found for Acinetobacter spp. and Klebsiella spp. (256 mg/L and 512 mg/L, respectively). Conclusions: IVFOS appears to be suitable for the treatment of many infections, including the empirical treatment of polymicrobial infections and those caused by MDR strains, since the sensitivity of the studied strains to this antibiotic in different groups ranged from 66% to as much as 99%. Sensitivity to fosfomycin was also demonstrated by 60% of carbapenem-resistant strains; therefore, IVFOS is one of the few therapeutic options that can be effective against the most resistant Gram-negative rods. In light of the general consultation posted by EUCAST, obtaining data such as IVFOS MIC value distributions may be vital for the decision of implementing fosfomycin into breakpoint tables.

Activity of Fosfomycin Against The Spectrum of Uropathogens Causing Cystitis

Background:

Urinary tract infections (UTIs) are the most frequent bacterial infections, commonly seen in females. High degree of antimicrobial resistance in uropathogens has challenged the use of therapeutic agents. Fosfomycin which is an old antibiotic with distinctive characteristics, seems to be a promising novel therapeutic agent with a good bactericidal activity towards multi-drug resistant (MDR) uropathogens.

Objective:

The main objective of the study is to evaluate the antibacterial activity of fosfomycin among uropathogens causing cystitis.

Methods:

The study was carried out between 2017-2018. A total of 2060 UTI suspects from outpatient department (OPDs) and inpatient department (IPDs) were screened. Out of 2060 screened patients 1658 were IPD patients and 402 were OPD patients. Patient’s midstream urine samples were collected aseptically and processed according to standard protocols. The frequency of extended-spectrum-beta lactamases (ESBLs) producer and carbapenem resistance were estimated respectively. Cultures with significant growth of uropathogens were identified and minimum inhibitory concentration (MIC) to fosfomycin was determined by agar dilution (AD) and by E-test methods.

Results:

184 out of 2060 (8.9%) urine samples showed significant growth of uropathogens. Uropathogenic Escherichia coli (UPEC) (64%,118/184) was found to be the mostly isolated uropathogen. Among these Gram-negative uropathogens, 80% were ESBLs producers, 43.2% were carbapenem-resistant and 78% isolates were found to be MDR. The fosfomycin susceptibility for UPEC was 95% by AD method.

Conclusions:

This study suggests that Fosfomycin is reasonably effective and can be used in the treatment of MDR uropathogens along with uncomplicated UTIs.

Predisposition of Blood group Non-secretors to Urinary tract infection with Escherichia coli Anti-microbial Resistance and Acute Kidney Injury

Urinary tract infection (UTI) causes significant renal damage and disease severity is compounded by antimicrobial resistance (AMR) and other comorbidities in the patient. Blood group antigens secreted in body fluids (secretor status) are known to play a role in bacterial adhesion and we studied its influence on AMR in UTI. A total of 2758 patients with UTI were studied with urine culture, qualitative and semiquantitative urine microscopy, serum creatinine and secretor status in saliva samples by adsorption-inhibition method. Of these, AMR from 300 patients with E. coli infection were assessed as per CLSI 2019 guidelines and extended-spectrum beta-lactamase (ESBL) genes (bla TEM, bla CTX-M, bla SHV) and NDM1 genes were studied using TaqMan probes in Real-time polymerase chain reaction. Patients with UTI were followed up for two weeks. Female patients had higher predilection (57%) for E. coli infection while patients with diabetes or non-secretors had none. In our study, ESBL producers were seen in 62% of the E. coli isolates and fosfomycin had 100% susceptibility. Non-secretors were significantly associated with acute kidney injury (AKI), AMR and ESBL genes. Multidrug-resistance (MDR) was noted in 127/160 (79.4%) ESBL and 17/18 (94%) NDM1 gene encoding strains. Quantitative urine microscopy scoring predicted AKI both at presentation and at end of follow up. ESBL producers were common in our study population and non-secretors had a significant association with AMR genes. Urine microscopy scoring system may be a useful tool to predict AKI in patients with UTI.

Predisposition of Blood group Non-secretors to Urinary tract infection with Escherichia coli Anti-microbial Resistance and Acute Kidney Injury

Urinary tract infection (UTI) causes significant renal damage and disease severity is compounded by antimicrobial resistance (AMR) and other comorbidities in the patient. Blood group antigens secreted in body fluids (secretor status) are known to play a role in bacterial adhesion and we studied its influence on AMR in UTI. A total of 2758 patients with UTI were studied with urine culture, qualitative and semiquantitative urine microscopy, serum creatinine and secretor status in saliva samples by adsorption-inhibition method. Of these, AMR from 300 patients with E. coli infection were assessed as per CLSI 2019 guidelines and extended-spectrum beta-lactamase (ESBL) genes (bla TEM, bla CTX-M, bla SHV) and NDM1 genes were studied using TaqMan probes in Real-time polymerase chain reaction. Patients with UTI were followed up for two weeks. Female patients had higher predilection (57%) for E. coli infection while patients with diabetes or non-secretors had none. In our study, ESBL producers were seen in 62% of the E. coli isolates and fosfomycin had 100% susceptibility. Non-secretors were significantly associated with acute kidney injury (AKI), AMR and ESBL genes. Multidrug-resistance (MDR) was noted in 127/160 (79.4%) ESBL and 17/18 (94%) NDM1 gene encoding strains. Quantitative urine microscopy scoring predicted AKI both at presentation and at end of follow up. ESBL producers were common in our study population and non-secretors had a significant association with AMR genes. Urine microscopy scoring system may be a useful tool to predict AKI in patients with UTI.

Fosfomycin versus Nitrofurantoin for the Treatment of Lower UTI in Outpatients

Introduction Fosfomycin and nitrofurantoin are increasingly being prescribed in outpatients for the oral treatment of urinary tract infection (UTI). Although ample literature is available on the in vitro sensitivity pattern of fosfomycin and nitrofurantoin in UTI cases, clinical data are scant.

Methodology  Voided midstream urine, collected from patients ≥ 16 years of age of both genders with suspected sign and symptoms, was plated on cystine lactose electrolyte-deficient agar. Uropathogen was defined as an organism known to be associated with the signs and symptoms of UTI with > 10 ⁵ colony forming units/mL of urine. Antimicrobial susceptibility testing was determined by Kirby-Bauer disc diffusion method. Further, for fosfomycin, agar dilution method was also performed.

Results  A total of 143 patients, 47 treated with fosfomycin and 96 with nitrofurantoin, were followed for clinical outcome. The most common isolated uropathogen was Escherichiacoli . In vitro susceptibility rate of uropathogens against fosfomycin and nitrofurantoin was 99.3% and 81.2%, respectively. Overall, the clinical cure rate with fosfomycin and nitrofurantoin treatment groups was 80.85% and 90.06% respectively (not statistically significant).

Conclusion  Fosfomycin and nitrofurantoin showed good in vitro activity against uropathogens from lower UTI and can be used for empirical therapy in our area. Multiple confounding factors may have contributed to the discrepancy between in vitro susceptibility and clinical cure, which needs to be studied further.

Increased Isolation of Extended-Spectrum Beta-Lactamase-Producing Escherichia coli From Community-Onset Urinary Tract Infection Cases in Uttarakhand, India

Background: Management of community-acquired urinary tract infection (CA-UTI) relies heavily on empirical antibiotic therapy. Knowledge of the proportion of drug-resistant isolates especially extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (E. coli), and various risk factors for acquisition are essential.

Method: Outpatient-treated CA-UTI cases were enrolled (continuously for three months), and microbiological analysis of urine sample was performed for significant bacterial growth followed by identification of conventional and matrix-assisted laser desorption/ionization-time of flight (MALDI-ToF) spectrometry method. Subsequent drug resistance and phenotypic ESBL detection were as per guidelines of the Clinical Laboratory Standard Institute (CLSI, USA). Univariate and multivariate analyses (logistic regression) of known and relevant risk factors of ESBL E. coli were performed as per standard statistical technique, using the SPSS computer package (IBM Corp., Armonk, NY). 

Results: Two hundred and forty-one samples (of 694 samples) yielded significant growth. Sixty-one of 131 (46.6%) E. coli isolates were found to be ESBL producers. Non-beta-lactam antibiotic resistance in ESBL producers was high compared to non-ESBL producers (e.g., 88.5% vs 42.3% for quinolone resistance, 80.3% vs 34.3% for gentamicin resistance, etc.). Multivariate analysis (after univariate analysis detected probable factors of a likely ESBL model) indicated significant associations of ESBL-producing E. coli with advancing age (>55 years), prior hospitalization in last one year, use of antibiotics in previous six months, and presence of comorbid illness such as diabetes mellitus and chronic lung disease.

Conclusion: High proportion of our community-acquired uropathogens are ESBL-producing E. coli and likely resistant to important antimicrobial agents such as quinolones, gentamicin, etc. Factors like advancing age, prior hospitalization, and antibiotic use, as well as comorbidities such as diabetes and chronic lung disease, may be strongly associated with ESBL E. coli and should be remembered while administering or preparing guidelines for empiric management of CA-UTI subjects.

In Vitro Activity of Fosfomycin and Nitrofurantoin Against Contemporary Enterobacterales Pathogens Isolated from Indian Tertiary Care Hospitals

Background: In India, multidrug resistance in community and hospital associated Gram-negative pathogens has increased sharply over the past few years. In the absence of novel oral multidrug resistant-pathogen active therapies, the therapeutic situation with regard to community infections is even more challenging. Hence, the focus is now shifting toward potentially expanding the utility of older antibiotics such as fosfomycin and nitrofurantoin beyond their approved pathogen coverage. The current study was undertaken to assess the activity of fosfomycin and nitrofurantoin against Enterobacterales pathogens through minimum inhibitory concentration (MIC) determination to facilitate monitoring future shifts in susceptibility to these agents. Materials and Methods: The present study used 1,350 Enterobacterales, recently collected from various Indian tertiary care hospitals and preserved at Wockhardt Strain Repository. The MIC_50/90 for fosfomycin and nitrofurantoin and the comparator antibiotics was determined for Escherichia coli (N = 470), Klebsiella pneumoniae (N = 429), Enterobacter spp., (N = 144), Proteus spp. (N = 262), and Citrobacter spp. (N = 45), using Clinical and Laboratory Standards Institute recommended agar dilution method. Results: Applying E. coli breakpoints, the susceptibility rates of fosfomycin for E. coli, K. pneumoniae, Enterobacter spp., Proteus spp., and Citrobacter spp., were 95.5%, 53.2%, 71.5%, 76.7%, and 91.1%, respectively. Applying respective breakpoints, the susceptibility rates of comparator drugs, including meropenem, were lower than fosfomycin. Susceptibility of nitrofurantoin for E. coli and Citrobacter isolate was 83%, while limited coverage (<13.2% susceptibility) was observed for other genera. Conclusion: Amidst widespread resistance, a > 70% fosfomycin susceptibility observed for clinical isolates, including strains expressing carbapenemases, is encouraging and supports conducting additional susceptibility and pharmacokinetic/pharmacodynamic studies to explore its potential for expanded therapeutic use. Nitrofurantoin activity spectrum was restricted to E. coli and Citrobacter spp. and, therefore, offers a relatively limited therapeutic scope.

Antibacterial effect of fosfomycin tromethamine on the bacteria inside urinary infection stones

OBJECTIVE

This study sought to evaluate the antibacterial effect of fosfomycin tromethamine (FT) on the bacteria inside urinary infection stones.

METHODS

The internal structures of urinary stones were observed via scanning electron microscopy to verify the presence of internal bacteria. We randomly assigned equal numbers of patients with kidney stones who met the inclusion criteria into two groups in a prospective study and treated them with different perioperative antibiotics. One group (experimental group) was treated with FT, and the other (control group) was treated with cefuroxime sodium. All stone specimens were collected via percutaneous nephrolithotomy (PCNL). The primary infection stones were screened via a stone component analysis, 30 cases in the experimental group and 31 cases in the control group. High-performance liquid chromatography (HPLC)-mass spectrometry was used to measure the drug concentration inside the stones, the bacterial count was calculated via stone culture, and the clinical infection index were monitored for between-group comparisons.

RESULTS

Compared with the control group, the experimental group had a higher internal drug concentration, a higher drug sensitivity against various pathogenic bacteria, a lower bacterial colony count in the stone culture, and a lower incidence of postoperative clinical infection.

CONCLUSIONS

FT is more effective than cefuroxime, which is commonly used during the perioperative period of urinary stones, and exerts a high antibacterial effect on these internal bacteria, and effectively reduces the probability of infection and sepsis after urinary stone surgery. FT can be used as an antibiotic during the perioperative period of urinary stones.

Evaluation of in vitro susceptibility of fosfomycin among Enterobacteriaceae isolates from urine cultures: A study from Puducherry

INTRODUCTION:

The increasing drug resistance among Gram-negative uropathogens and a lack of effective oral antibiotics have limited the therapeutic options available for urinary tract infections (UTIs). This shortage of newer antibiotics has paved the way for considering the use of older antibiotics such as fosfomycin. This study aims to evaluate the in vitro susceptibility of Enterobacteriaceae isolates to fosfomycin.

MATERIALS AND METHODS:

In this descriptive study conducted over a period of 6 months, we processed 1500 urine samples. The Enterobacteriaceae isolates were subjected to in vitro susceptibility testing to fosfomycin, in addition to the regularly used urinary antibiotics, by Kirby–Bauer disc-diffusion method.

RESULTS:

Of 1500 urine samples processed, 582 samples yielded the growth of pathogens. Enterobacteriaceae accounted for 392 (67.3%) of the isolates. Among these isolates, lower rates of resistance were observed for imipenem (4.1%) and fosfomycin (13.3%). Relatively higher rates of resistance were observed for nitrofurantoin (35.5%) and amikacin (30.9%). Nalidixic acid, norfloxacin, gentamicin, cefotaxime, and cotrimoxazole showed a high resistance rate of 82.7%, 69.6%, 52.3%, 69.1%, and 71.4%, respectively. All antibiotics, except fosfomycin, were in routine clinical use in our hospital. The low resistance (13.3%) to fosfomycin is indicative of its utility as an excellent urinary antibiotic.

CONCLUSIONS:

Uropathogenic Enterobacteriaceae isolates displayed excellent in vitro susceptibility to fosfomycin. These in vitro findings suggest the unexplored potential of fosfomycin as a superior therapeutic option for treating uncomplicated UTI.

In vitro effect of fosfomycin on multi-drug resistant gram-negative bacteria causing urinary tract infections

Background

Rising rates of resistance to antimicrobial drugs among Enterobacteriaceae limit the choice of therapeutic agents to treat urinary tract infections. In this context we assessed the in-vitro effect of fosfomycin against extended-spectrum beta-lactamases, AmpC beta-lactamases and carbapenemase-producing strains of Escherichia coli, Klebsiella pneumoniae, Enterobacter spp, and Pseudomonas aeruginosa isolated from the patients with urinary tract infection (UTI) and also studied the effect of fosfomycin on their biofilm formation.

Materials and methods

A total of 326 multidrug-resistant (MDR) isolates comprising of Escherichia coli, Klebsiella pneumoniae, Enterobacter spp, and Pseudomonas aeruginosa from the urine samples of the patients with a diagnosis of UTI were included in the study. MIC 50 and MIC 90 were detected by agar dilution method and the capacity to form biofilm in the presence of fosfomycin by these MDR isolates was assessed by the tissue culture plate method.

Results

The MIC50 for meropenem (0.5 µgm/mL) and nitrofurantoin (32 µgm/mL) was within the susceptible range only for E. coli. Fosfomycin was the only antibiotic that inhibited 100% E.coli, 70% Klebsiella spp, and 50% Pseudomonas spp and 40% Enterobacter spp which included the extended-spectrum beta-lactamases producers. It showed a similar effect on carbapenemase producers and AmpC producers. Fosfomycin disrupted biofilm in 67% (n=141) E.coli, 74% (n=50) Klebsiella spp, 88% (n=27) Pseudomonas spp and 36% (n=23) Enterobacter spp at 24 hrs of incubation with a concentration of 2 fold dilution lower than that of the MIC.

Conclusion

Fosfomycin showed a good inhibitory effect on the biofilms produced by the MDR organisms studied here.

Community- and Hospital-Acquired Klebsiella pneumoniae Urinary Tract Infections in Portugal: Virulence and Antibiotic Resistance

Klebsiella pneumoniae is a clinically relevant pathogen and a frequent cause of hospital-acquired (HA) and community-acquired (CA) urinary tract infections (UTI). The increased resistance of this pathogen is leading to limited therapeutic options. To investigate the epidemiology, virulence, and antibiotic resistance profile of K. pneumoniae in urinary tract infections, we conducted a multicenter retrospective study for a total of 81 isolates (50 CA-UTI and 31 HA-UTI) in Portugal. The detection and characterization of resistance and virulence determinants were performed by molecular methods (PCR, PCR-based replicon typing, and multilocus sequence typing (MLST)). Out of 50 CA-UTI isolates, six (12.0%) carried β-lactamase enzymes, namely bla_TEM-156 (n = 2), bla_TEM-24 (n = 1), bla_SHV-11 (n = 1), bla_SHV-33 (n = 1), and bla_CTX-M-15 (n = 1). All HA-UTI were extended-spectrum β-lactamase (ESBL) producers and had a multidrug resistant profile as compared to the CA-UTI isolates, which were mainly resistant to ciprofloxacin, levofloxacin, tigecycline, and fosfomycin. In conclusion, in contrast to community-acquired isolates, there is an overlap between virulence and multidrug resistance for hospital-acquired UTI K. pneumoniae pathogens. The study is the first to report different virulence characteristics for hospital and community K. pneumoniae pathogens, despite the production of β-lactamase and even with the presence of CTX-M-15 ESBL, a successful international ST15 clone, which were identified in both settings. This highlights that a focus on genomic surveillance should remain a priority in the hospital environment.

In Vitro Activity of Newer and Conventional Antimicrobial Agents, Including Fosfomycin and Colistin, against Selected Gram-Negative Bacilli in Kuwait

Limited data are available on susceptibilities of these organisms to some of the recently made accessible antimicrobial agents. The in vitro activities of newer antibiotics, such as, ceftolozane/tazobactam (C/T) and ceftazidime/avibactam (CZA) along with some “older” antibiotics, for example fosfomycin (FOS) and colistin (CL) were determined against selected strains (resistant to ≥3 antimicrobial agents) of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Minimum inhibitory concentrations (MIC) were determined by Clinical and Laboratory Standards Institute microbroth dilution. 133 isolates: 46 E. coli, 39 K. pneumoniae, and 48 P. aeruginosa were tested. Results showed that E. coli isolates with MIC_50/90, 0.5/1 μg/mL for CL; 4/32 μg/mL for FOS; 0.25/32 μg/mL for C/T; 0.25/8 μg/mL for CZA, exhibited susceptibility rates of 95.7%, 97.8%, 76.1%, and 89.1%, respectively. On the other hand, K. pneumoniae strains with MIC_50/90, 0.5/1 μg/mL for CL; 256/512 μg/mL for FOS; 2/128 μg/mL for C/T; 0.5/128 μg/mL for CZA showed susceptibility rates of 92.3%, 7.7%, 51.3%, and 64.1%, respectively. P. aeruginosa isolates with MIC_50/90, 1/1 μg/mL for CL; 128/128 μg/mL for C/T; 32/64 μg/mL for CZA presented susceptibility rates of 97.9%, 33.3%, and 39.6%, respectively. Higher MICs were demonstrated against most of the antibiotics. However, CL retained efficacy at low MICs against most of the isolates tested.

Urinary Tract Infection Antibiotic Resistance in the United States

Urinary tract infection (UTI) is one of the most common entities in medicine and affected patients present daily in a typical family medicine practice. The patients often present with the "classic symptoms" of dysuria and increased frequency, but sometimes they are asymptomatic or have a mixed picture. In most cases, an antibiotic is prescribed, and this practice is likely contributing to increasing worldwide antibiotic resistance. To help combat this problem, it is important that clinicians seek out their local bacterial resistance patterns and antibiograms, properly diagnose and treat UTI if indicated, and recognize their role in antibiotic stewardship.

In vitro Activity of Fosfomycin against Multidrug-Resistant Urinary and Nonurinary Gram-Negative Isolates

Background:

The era of multidrug-resistant (MDR) Gram-negative bacilli (GNB) has renewed interest in fosfomycin.

Aim:

The present study evaluated the in vitro activity of fosfomycin against MDR urinary and nonurinary GNB isolates.

Materials and Methods:

Fosfomycin susceptibility was carried out by agar dilution for a total of 279 (142 from urine and 137 from other samples) MDR-GNB. Disk diffusion was done for urinary isolates only.

Results:

Urinary tract isolates had a high degree of susceptibility to fosfomycin (overall susceptibility, 90.8%), whereas only 42.9% of nonurinary isolates retained susceptibility to the drug. Percentage susceptibility rates for urinary and nonurinary isolates of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter spp. were 99%, 91.3%, 66%, 0% and 62%, 44.4%, 32%, 11%, respectively.

Conclusion:

Fosfomycin showed excellent in vitro activity for uropathogens. Large-scale evaluation of fosfomycin against MDR systemic isolates is required to evaluate its therapeutic efficacy.