Investigation of the effect of rifampicin resistance and risk factors on recovery rates after DAIR procedure in patients with prosthetic joint infection

BACKGROUND

Rifampicin plays a key role in the management of prosthetic joint infections (PJIs), however, the emergence of rifampicin resistance is associated with less favourable clinical outcomes. The purpose of this study was to investigate the impact of rifampicin resistance and other patient-related factors on recovery rates among patients with PJI undergoing debridement, antibiotics and implant retention (DAIR).

METHODS

We reviewed medical records and microbiology reports of 67 patients (37 males and 30 females) undergoing DAIR due to PJI between 2014 and 2021. Patient-related factors, co-morbidities and microbiological reports were collected and reviewed. Forty-four patients had hip, 21 had knee, 1 had shoulder and 1 had elbow joint infection. Obtained data were statistically analysed with a logistic regression model.

RESULTS

Rifampicin-sensitive organism was isolated in 47 cases. Recovery rate was 72.3% in the sensitive and 76.9% in the resistant group. We found no significant effect of rifampicin resistance on the probability of recovery. Age and diabetes mellitus showed negative clinical impact on recovery. Staphylococcus aureus and coagulase-negative Staphylococci were predominant in the rifampicin-sensitive (66.6% of the isolates) and Gram-negative rods in the resistant group (65.2%).

CONCLUSIONS

Based on our results, higher age and diabetes mellitus may have a clinically relevant negative impact on clinical outcome, however, this effect was not statistically significant. This may be due to the limited number of patients included in this study. We observed no clinically relevant effect of rifampicin-resistance, sex and body mass index (BMI) on recovery rates among patients undergoing DAIR due to PJI.

Infection and colonization by Stenotrophomonas maltophilia: antimicrobial susceptibility and clinical background of strains isolated at a tertiary care centre in Hungary

BACKGROUND

Stenotrophomonas maltophilia is an important opportunistic, mainly nosocomial pathogen that emerged in the last decades worldwide. Due to its inherent extended antibiotic resistance, therapeutic options are strongly limited. New resistance mechanisms in S. maltophilia make antibiotic therapy even more difficult. The aim of our study was to investigate the antimicrobial resistance of S. maltophilia isolates collected in our laboratory and to reveal related clinical background.

METHOD

Consecutive non-duplicate S. maltophilia isolates (n = 160) were collected in a three-year period. Conventional methods, automated identification system and MALDI-TOF MS was used for identification, ERIC-PCR for genetic relationship analysis and broth microdilution method to determine the susceptibility for trimethoprim/sulfamethoxazole (SXT), ciprofloxacin, levofloxacin, moxifloxacin, colistin, doxycycline and tigecycline. Clinical final reports were used retrospectively to collect clinical information.

RESULTS

ERIC-PCR revealed large heterogeneity. Trimethoprim/sulfamethoxazole, moxifloxacin and levofloxacin were found to be the most effective agents with MIC50/MIC90 0.5/1, 0.25/1, 1/2 mg/l, respectively. Seventy percent of patients with S. maltophilia infection were treated in intensive care units. All-cause mortality rate was 45%. Nearly 70% of the isolates were collected from polymicrobial infections/colonizations.

CONCLUSIONS

Trimethoprim/sulfamethoxazole is the most potent antibiotic agent against S. maltophilia. In case of SXT hypersensitivity, intolerance or resistance, fluoroquinolones are alternative therapeutic options. Missing clinical breakpoints, consensus antibiotic susceptibility testing guidelines and clinical trials make the interpretation of antibiotic susceptibility testing results difficult. The indirect pathogenicity of S. maltophilia in polymicrobial infections or colonizations has to be taken into consideration.

In vitro activity of clarithromycin in combination with other antimicrobial agents against biofilm-forming Pseudomonas aeruginosa strains

The aim of the study was to investigate the biofilm-production of 60 Pseudomonas aeruginosa strains isolated from clinical samples and to examine the effect of different antimicrobials and their combinations with clarithromycin on biofilm-formation. The minimal inhibitory concentrations (MICs), minimal biofilm inhibitory concentrations (MBICs), and antibiotic synergy by calculating the fractional inhibitory concentration (FIC) index were determined for the following antibiotics: ceftazidime, cefepime, piperacillin/tazobactam, imipenem, meropenem, levofloxacin, ciprofloxacin, gentamicin, amikacin, tobramycin, netilmicin and clarithromycin. A total of 14 (23.3%) isolates out of 60 isolates of P. aeruginosa were biofilm positive. Cefepime, imipenem and meropenem had the lowest MIC 90 values. Piperacillin/tazobactam and clarithromycin had the highest MIC 90 values. Imipenem, meropenem, piperacillin/tazobactam and clarithromycin had the lowest MBIC 90 values. For biofilm-forming P. aeruginosa strains 2-fold to 128-fold higher MBIC values than MIC values were obtained for ceftazidime, cefepime, imipenem, amikacin and netilmicin. The MBIC was 2-fold to 512-fold lower then the MIC values in the case of piperacillin/tazobactam, ciprofloxacin, levofloxacin and clarithromycin. Synergy was generally demonstrated for clarithromycin in combination with aminoglycosides, fluoroquinolones or ceftazidime. However, surprisingly it was found that combinations of clarithromycin with carbapenems or cefepime led to an antagonistic interaction: combination of clarithromycin with imipenem, meropenem or ertapenem showed antagonism in 37.5%, 50% and 62.5% of the strains tested whereas its combination with cefepime expressed antagonism in 75% of the strains, respectively. To the best of our knowledge no one has previously described this phenomenon so far.