ABSTRACT
Myroides species are mostly low-grade opportunistic pathogens and infect immunocompromised patients. Reports of Myroides spp. increased from clinical samples due to unique developments in molecular microbiology. However, clinical importance of this microorganism in intensive care units’ patients is debated. We aimed to determine whether Myroides spp. strains isolated from urinary catheter cultures of patients in intensive care units are led to an infection or colonization by examining the risk factors of the patients between January 2018 and December 2022.
In a university hospital, the patients who Myroides spp.isolated from urine cultures in intensive care units between January 2018 and December 2022 were included in the study. The method and reasons of taking urine samples, the presence of a urinary catheter, blood cultures samples in terms of urinary sepsis, the antimicrobial susceptibility of the isolates, and hospital stay were evaluated retrospectively. Also, control culture samples were taken after 24 and 72 hours by changing the urinary catheters of these patients.
Results: Thirty-six patients were enrolled to the study. Urine cultures were taken for investigate the source of infection in 23 patients, and nine for control urinary culture and in three patients for macroscopic urine blurred and in one patient to detect colonization before urinary surgery. There was not any blood culture positivity found. All Myroides spp. isolated patients had urinary catheter. Average length of hospital stay was determined as 41.3 days (7-355). A total 34 of the 36 isolated Myroides spp. were pan-drug resistant. Antibacterial treatment was not initiated in any of the patients. Urinary catheters change after first isolation of Myroides spp. was recommended in all patients. After the patients’ urinary catheters were changed, Myroides spp. were not grown in the control culture samples taken 24 and 72 hours after.
As a result of our study, Myroides spp. were isolated especially in patients with long hospital stays and urinary catheters. It was determined that the patients were controlled without treatment, only with urinary catheter replacement. We believe that this agent should be evaluated as having a very high rate of urinary colonization, and the urinary catheter should be changed first, urinary symptoms should be followed up, and unnecessary antimicrobial use should be avoided.
Introduction
In recent years, in line with the unique developments in molecular microbiology, many bacteria that were previously isolated from clinical samples but could not be typed have begun to be typed. Therefore, the incidence of Myroides species reports has increased in clinical samples, especially urine culture samples taken from patients with urinary catheters (1).
Myroides species are yellow-pigmented, non-fermentative, Gram-negative bacilli and previously classified as Flavobacterium species. Also, Myroides spp. is widely found in environmental sources, especially in soil and water, but it is also isolated from seafood, and meat processing plants. Although Myroides spp. are ubiquitous in marine and soil environments, they have been associated with very few documented infections in humans since their first identification in the 1920s (2). Myroides spp. are reported to rarely cause infection in immunocompromised patients (3, 4). Although this microorganism is considered a pathogen with low infection potential, it has been reported to be associated with various life-threatening infections such as meningitis, pneumonia, septicemia, urinary tract, and soft tissue infections in recent years. Myroides spp. are mostly low-grade opportunistic pathogens and infect immunocompromised patients such as those with kidney failure, liver cirrhosis, lung disease, cancer, and prolonged stays in intensive care units (4, 5).
Myroides species were rarely isolated from a variety of clinical samples of human infections, such as urine, wounds, and blood. In the literature, the most common infections, depending on Myroides spp. are reported as urinary tract infections (UTIs). Urinary catheter use is an important risk factor for these infections. However, although infections caused by Myroides spp. are rare, they are resistant to multiple antibiotics, such as carbapenems, beta-lactams, and have variable sensitivity to aminoglycosides, quinolones, and sulfamethoxazole (6).
In this context, it was observed in our hospital that the reporting of multi-drug resistant Myroides spp. isolates increased. In this study, we aimed to determine whether Myroides spp. strains isolated from urinary catheter cultures of patients in intensive care units led to infection or colonization by examining the risk factors of the patients between January 2018 and December 2022.
Materials and Methods
Hospital Setting
The study was conducted in a tertiary university hospital with a capacity of 1370 beds and 352 intensive care beds. Thirty-six patients who were hospitalized in intensive care units between January 2018 and December 2022 and whose Myroides spp. were isolated from their clinical samples were included in the study. An informed consent form for the patients was provided. All clinical samples were urine culture samples. Repeated samples from the same patient were excluded from the study. The study was managed following the principles of the Declaration of Helsinki. Ethics committee approval was obtained from the İnönü University Scientific Research and Publication Ethics Committee (decision no: 2021/1240, date: 05.01.2021).
The method and reason for taking urine samples, the presence of a catheter in the patients, blood culture samples in terms of urinary sepsis, the antimicrobial susceptibility of the isolated Myroides spp., and hospital stay were evaluated. Also, control culture samples were taken after 24 and 72 hours by exchanging the urinary catheters of these patients.
Identification and Antimicrobial Susceptibility
Urine culture samples were taken from patients’ catheters in accordance with aseptic techniques. The samples were sent to the microbiology laboratory to be processed within 30 minutes in sterile containers. Urine samples were quantitatively inoculated on 5% sheep blood agar and eosin methylene blue agar medium in the laboratory. After 18-24 hours’ incubation at 37 °C, identification of the isolates that were grown as 1-2 mm round, smooth yellow pigmented, fruit-scented oxidase and catalase positive, Gram-negative bacilli was made by Matrix-Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) (BioMérieux, France). The antimicrobial susceptibility of the isolates to ciprofloxacin, levofloxacin, amoxicillin-clavulanic acid, cefepime, ceftazidime, cefotaxime, imipenem, meropenem, gentamicin, amikacin, piperacillin/tazobactam, and trimethoprim/sulfamethoxazole was determined by the disk diffusion method on Mueller-Hinton agar medium, and colistin susceptibility was determined by the broth micro-dilution method. Results were interpreted according to The European Committee on Antimicrobial Susceptibility Testing guideline recommendations (7). Blood culture samples sent to our laboratory were incubated for 5 days in the BACT/ALERT 3D (BioMérieux, France) fully automated blood culture system.
Statistical Analysis
Statistical analyses were performed using SPSS for Windows, version 17.0 (IBM-SPSS Inc, Armonk, NY).
Results
Myroides spp. was isolated in 36 of the urine culture samples sent from intensive care units to our laboratory over a period of five years. The mean age of the patients was 59±19.9 years (10-84 years), and 22 (61.1%) were male patients. Patients were hospitalized in ICU due to trauma, intracranial events, myocardial infarction, acute renal failure. There was no comorbidity in 11 patients, the other patients had renal or urogenital problems, pulmonary and cardiac problems, intracranial events, and malignancy. All Myroides spp. isolated patients had urinary catheters. Thirty four isolates were resistant to the studied antimicrobials, ciprofloxacin, levofloxacin, amoxicillin-clavulanic acid, cefepime, ceftazidime, cefotaxime, imipenem, meropenem, gentamicin, amikacin, piperacillin/tazobactam, trimethoprim/sulfamethoxazole, and colistin. One isolate was susceptible to cefepime, ceftazidime, cefotaxime, gentamicin, amikacin, trimethoprim/sulfamethoxazole, and two isolates were susceptible to colistin. Based on these results, we concluded that the isolates were pan-drug resistant, except for two strains. It was found that urine cultures were taken during the investigation of the infection focus in 23 of the patients to determine whether the urinary agent was controlled in nine patients, in three patients because of turbidity in the urine color, and in one patient to detect colonization before urinary surgery. None of the patients had urinary symptoms. Before Myroides spp. was isolated, six patients were not receiving any antibiotic treatment, eight patients were using piperacillin/tazobactam, 19 patients were using meropenem, and three patients were using ciprofloxacin. However, spesific antibacterial treatment was not initiated in any of the patients against Myroides spp.
Urinary catheter changes were recommended for all patients. After the patients’ urinary catheters were changed, Myroides spp. isolates were grown in only four of the control culture samples taken 24 hours later. There was no growth in the control culture samples taken 24 and 72 hours after exchanging the urinary catheters of the other thirty-two patients. Urinary catheters of the patients who had growth at the 24th hour was exchanged again, and there was no growth in the samples taken at the 24th and 72nd hours.
In blood cultures, Myroides spp. were not isolated. The average length of hospital stay was determined to be 41.3 days (7-355).
Discussion
Currently, the spectrum of healthcare associated, and community-acquired infections caused by new opportunistic pathogens is constantly increasing. This increase in the number of newly described microorganisms is due to the introduction of MALDI-TOF into clinical microbiology laboratories and the use of molecular identification methods such as 16S rRNA sequencing (1). Due to these technological advances, Myroides spp. are much more isolated in urine culture samples.
Myroides spp. is an aerobic, non-fermentative, immobile Gram-negative bacillus, usually found in water and soil. Due to the presence of flexirubin, they are bacteria with a yellow pigment and a characteristic fruity smell like strawberries (4). They do not belong to the normal human flora. However, since they are rare pathogens in humans, they are considered low-grade opportunistic pathogens. Opportunistic infections have been reported mostly in immunocompromised patients (3, 4). Also, despite their low pathogenicity potential, Myroides spp. isolates are multidrug resistant. They can also form biofilms and have a polysaccharide capsule that makes their surface hydrophobic (4, 6).
It has been reported in the literature that Myroides spp. can cause the most common UTIs and rarely soft tissue, bone, pneumonia, and sepsis (8). Myroides spp. was first reported as an infection agent by Holmes et al. (9) after it was identified from urine cultures. Ktari et al. (10) reported seven UTIs cases due to Myroides spp. in patients who underwent endo-urological operations and had urinary stones. Licker et al. (11) reported four hospital acquired UTIs due to Myroides odoratimimus isolated from the urine specimens of immunocompromised patients. The patients had urinary catheters, and all isolates were resistant to antibiotics. In the report of Yağci et al. (12), in our country, it has been shown that patients with UTIs due to Myroides spp. are catheterized or have urinary tract neoplasia or stones. Kutlu et al. (13) reported an outbreak of UTIs in intensive care units. They isolated six strains of M. odoratimimus from the urine samples. They said that all the patients were immunocompromised, underwent urinary catheterization, and none of the patients had urinary neoplasm, surgery, or calculi. Additionally, they identified the isolates as M. odoratimimus by 16S rRNA-based sequencing and determined that the isolates were resistant to antibiotics.
Antimicrobial treatment of infections due to Myroides spp. isolates is difficult due to their production of metallo-betalactamase. Therefore, many strains are resistant to beta-lactams and carbapenems. They may show variable sensitivity to aminoglycosides, quinolones, and trimethoprim/sulfamethoxazole (6, 8). A total of 34 of the isolated strains in our study were resistant to beta-lactams, carbapenems, aminoglycosides, quinolones, and trimethoprim/sulfamethoxazole. One isolate was susceptible to beta-lactams, aminoglycosides, and trimethoprim/sulfamethoxazole two isolates were susceptible to colistin. Kara et al. (14) reported that eleven Myroides spp. isolates they identified were resistant to all groups except tigecycline. Death has been reported in two cases due to Myroides spp. multi-drug resistance (15, 16).
As a result of our study, Myroides spp. was isolated from urine culture samples taken from the urinary catheters of thirty-six intensive care patients. No growth was detected in the control cultures taken after 72 hours of exchanging the urinary catheters of the patients. The most important risk factors for Myroides spp. in these patients seems to be the length of hospital stay and the presence of a urinary catheter. The average length of hospital stay for the patients were determined to be 41.3 days. However, isolated Myroides spp. was not considered an infection agent, and antimicrobial treatment was not applied to any of the patients.
The limitation of the study was that clonal relationship between the isolates and the source of Myroides spp. spread was not determined.
Conclusion
Myroides spp. were isolated, especially in patients with long hospital stays and urinary catheters. It was determined that the patients were controlled without treatment, only with urinary catheter replacement. We believe that this agent should be evaluated as having a very high rate of urinary colonization, and the urinary catheter should be changed first, urinary symptoms should be followed up, and unnecessary antimicrobial use should be avoided.
