Antimicrobial Resistance in Nosocomial Isolates of Gram-Negative Bacteria: Public Health Implications in the Latvian Context

Abstract

Antimicrobial resistance (AMR) is one of the most serious threats in modern medicine which requires the constant monitoring of emerging trends amongst clinical isolates. However, very limited surveillance data is available in the Latvian context. In the present study, we conducted a retrospective analysis of microbiological data from one of the largest public multispecialty hospitals in Latvia from 2017 to 2020. AMR trends for 19 gram-negative bacterial (GNB) genera were investigated. During the study period, 11,437 isolates were analyzed with Escherichia spp. (34.71%), Klebsiella spp. (19.22%) and Acinetobacter spp. (10.05%) being the most isolated. Carbapenems like Meropenem and Ertapenem were the most effective against GNBs (3% and 5.4% resistance rates, respectively) while high resistance rates (>50%) were noted against both Ampicillin and Amoxicillin/Clavulanic acid. Enterobacter spp. and Klebsiella spp. showed a significant increase in resistance rate against Ertapenem (p = 0.000) and Trimethoprim-Sulfamethoxazole (p = 0.000), respectively. A decrease in the prevalence of Extended-Spectrum Beta-Lactamase positive (ESBL+) Enterobacterales was noted. Despite the lower prescription levels of the penicillin group antimicrobials than the European average (as reported in ESAC-Net Surveillance reports), GNBs showed high average resistant rates, indicating the role of ESBL+ isolates in driving the resistance rates. Constant and careful vigilance along with proper infection control measures are required to track the emerging trends in AMR in GNBs.

Keywords: AMR; ESBL; antibiotics; antimicrobial resistance; gram-negative bacteria; nosocomial infection.

Figure 1

(A) Average resistance rates against tested antimicrobial agents and GNBs studied. Overall R% indicates the weighted average of resistance rates taking into count the number of isolates and the relevant resistance rates. (B) Trends in bacterial resistance to tested antibiotics across the study period (2017 vs 2020) using χ² test. AMC—amoxicillin-clavulanic acid; AMK—amikacin; AMP—ampicillin; CAZ—ceftazidime; CHL—chloramphenicol; CIP—ciprofloxacin; CTX—cefotaxime; ETP—ertapenem; GEN—gentamicin; IPM—Imipenem; MEM—meropenem; SXT—trimethoprim-sulfamethoxazole; TPZ—piperacillin-tazobactam.

Figure 2

Weighted average of MAR (multiple antibiotic resistance) index for different gram-negative nosocomial bacterial genera showing resistance to various tested antibiotics. MAR ≥ 0.2 indicates isolates originated from the source having a high-risk of antimicrobial contamination.

Figure 3

Percentage of isolates that were identified as Extended-Spectrum Beta-Lactamases positive (ESBL+). (A) Phylogenetic tree showing the phylogenic relationship of the different gram-negative bacteria studied in the present study along with their respective NCBI Taxon ID; (B) Percentage (%) of isolates that were ESBL+ among different genera of Enterobacterales in 2017; (C) Percentage (%) of isolates that were ESBL+ among different genera of Enterobacterales in 2020.

Figure 4

Average consumption rates of antimicrobials expressed as DDD (defined daily dose) per 1000 inhabitants per day (x-axis) against the average resistance rates of GNBs obtained in the present study (y-axis). Antimicrobials were classified based on WHO’s Anatomical Therapeutic Chemical Classification System—J01B includes CHL; J01G includes AMK and GEN; J01E includes SXT; J01M includes CIP; J01C includes AMC, AMP and TPZ; J01D includes CAZ, CTX, ETP, IPM and MEM. The colored lines indicate the respective group average for EEA/EU (European Economic Area/European Union).