Antimicrobial Resistance Patterns Continue to Evolve in Gram-Negative UTI Treatment – Renal and Urology News

Clinicians should consider the ever-changing spectrum of antimicrobial resistance (AMR) for the most common antibiotics when prescribing treatment for gram-negative urinary tract infections (UTIs), according to study results published in Therapeutic Advances in Infectious Disease.

Researchers conducted a retrospective analysis to explore patterns of AMR associated with the most common antibiotics prescribed for patients with gram-negative UTIs.  Urine cultures collected at the University Hospital Southampton in England between January 2014 and December 2022 were assessed for gram-negative pathogens (Acinetobacter, Escherichia coli, Haemophilus, Klebsiella, Morganella, Neisseria, Salmonella, Serratia marcescens, Pseudomonas, and Proteus). The sensitivity and resistance spectrums toward gram-negative bacteria were evaluated for 11 antibiotics, including amikacin, ampicillin–amoxicillin, cefalexin, ciprofloxacin, co-amoxiclav, fosfomycin, gentamicin, nitrofurantoin, pivmecillinam, piperacillin-tazobactam and trimethoprim.

Urine samples were analyzed using semi-automated Microbiological Antibiotic Sensitivity Testing (MAST) urine culture, as well as European Committee on antimicrobial susceptibility testing disc sensitivity. The Cochran-Armitage test was used to determine trends in resistance by antibiotic.

A total of 164,059 urine samples (primary care source, 71.94%; women, 78.84%; midstream urine, 91.93%) collected for culture analysis were positive for gram-negative bacteria.

Per data sourced in 2022, gentamycin and ciprofloxacin conferred the lowest levels of resistance to gram-negative bacteria (R =5.26% and 9.01%, respectively). Resistance levels of less than 20% were noted for pivmecillinam (R =11.02%), co-amoxiclav (R =12.69%), fosfomycin (R =13.65%), nitrofurantoin (R =14.8%), ceflexin (R =18.42%), and piperacillin-tazobactam (R =18.96%). However, AMR levels were high for both ampicillin-amoxicillin and trimethoprim (57.99% and 29.23%, respectively).

Trends in AMR between 2014 and 2022 varied by antibiotic, with no significant change in resistance levels observed for amikacin (+6.42%; P =.602) or fosfomycin (-13.55; P =.577). However, a positive trend in resistance levels was found for the following antibiotics:

• Pivmecillinam (-142.92%; P <.001);
• Ciprofloxacin (-31.30%; P <.001;
• Trimethoprim (-25.62%; P <.001);
• Gentamycin: (-19.58%; P <.001); and
• Ampicillin-amoxicillin (-12.43%; P <.001).

Further analysis of this time period showed increased AMR levels for the following antibiotics:

• Nitrofurantoin (+28.07%; P <.001);
• Co-amoxiclav (+25.45%; P <.001);
• Piperacillin-tazobactam (+23.42%; P <.001); and
• Cefalexin (+2.50%; P <.001).

Antibiotics exhibiting trends of reduced resistance and adequate efficacy against gram-negative bacteria, considered “golden antibiotics” by the researchers, included ciprofloxacin, fosfomycin, gentamycin, and pivmecilliman.

Study limitations include the retrospective design, missing data on patient characteristics, and the exclusion of urine samples for which cultures were not required for identification of the causative pathogen.

“As the trend in sensitivity for each commonly used antibiotic is continuously changing, our study provides an up-to-date review of the current situation, helping clinicians choosing the most appropriate class of antibiotics in view of the frequent resistance patterns,” the researchers concluded.

This article originally appeared on Infectious Disease Advisor