In vitro activity of ceftazidime/avibactam, cefiderocol, meropenem/vaborbactam and imipenem/relebactam against clinical strains of the Stenotrophomonas maltophilia complex

BACKGROUND

Infections caused by Stenotrophomonas maltophilia and related species are increasing worldwide. Unfortunately, treatment options are limited, whereas the antimicrobial resistance is increasing.

METHODS

We included clinical isolates identified as S. maltophilia by VITEK 2 Compact. Ceftazidime/avibactam, meropenem/vaborbactam, imipenem/relebactam, cefiderocol, quinolones, and tetracycline family members were evaluated by broth microdilution method and compared with first-line treatment drugs. Minimum inhibitory concentrations (MICs) were reported for all antibiotics. We sequenced the Whole Genome of cefiderocol resistant strains (CRSs) and annotated their genes associated with cefiderocol resistance (GACR). Presumptive phylogenetic identification employing the 16S marker was performed.

RESULTS

One hundred and one clinical strains were evaluated, sulfamethoxazole and trimethoprim, levofloxacin and minocycline showed susceptibilities of 99.01%, 95.04% and 100% respectively. Ceftazidime was the antibiotic with the highest percentage of resistance in all samples (77.22%). Five strains were resistant to cefiderocol exhibiting MIC values ≥ 2 μg/mL (4.95%). The β-lactamase inhibitors meropenem/vaborbactam and imipenem/relebactam, failed to inhibit S. maltophilia, preserving both MIC50 and MIC90 ≥64 μg/mL. Ceftazidime/avibactam restored the activity of ceftazidime decreasing the MIC range. Tigecycline had the lowest MIC range, MIC50 and MIC90. Phylogeny based on 16S rRNA allowed to identify to cefiderocol resistant strains as putative species clustered into Stenotrophomonas maltophilia complex (Smc). In these strains, we detected GARCs such as Mutiple Drug Resistance (MDR) efflux pumps, L1-type β-lactamases, iron transporters and type-1 fimbriae.

CONCLUSION

Antimicrobial resistance to first-line treatment is low. The in vitro activity of new β-lactamase inhibitors against S. maltophilia is poor, but avibactam may be a potential option. Cefiderocol could be considered as a potential new option for multidrug resistant infections. Tetracyclines had the best in vitro activity of all antibiotics evaluated.

Carbapenem-Resistant Gram-Negative Bacilli Characterization in a Tertiary Care Center from El Bajio, Mexico

Carbapenem-resistant Gram-negative bacilli (CR-GNB) are a major public health concern. We aimed to evaluate the prevalence of CR-GNB and the frequency of carbapenemase-encoding genes in a tertiary referral center from El Bajio, Mexico. A cross-sectional study was conducted between January and October 2022; Gram-negative bacilli (GNB) were screened for in vitro resistance to at least one carbapenem. CR-GNB were further analyzed for carbapenemase-production through phenotypical methods and by real-time PCR for the following genes: blaKPC, blaGES, blaNDM, blaVIM, blaIMP, and blaOXA-48. In total, 37 out of 508 GNB were carbapenem-resistant (7.3%, 95% CI 5.2-9.9). Non-fermenters had higher rates of carbapenem resistance than Enterobacterales (32.5% vs. 2.6%; OR 18.3, 95% CI 8.5-39, p < 0.0001), and Enterobacter cloacae showed higher carbapenem resistance than other Enterobacterales (27% vs. 1.4%; OR 25.9, 95% CI 6.9-95, p < 0.0001). Only 15 (40.5%) CR-GNB had a carbapenemase-encoding gene; Enterobacterales were more likely to have a carbapenemase-encoding gene than non-fermenters (63.6% vs. 30.8%, p = 0.08); blaNDM-1 and blaNDM-5 were the main genes found in Enterobacterales; and blaIMP-75 was the most common for Pseudomonas aeruginosa. The mcr-2 gene was harbored in one polymyxin-resistant E. cloacae. In our setting, NDM was the most common carbapenemase; however, less than half of the CR-GNB showed a carbapenemase-encoding gene.

Carbapenemase-Encoding Genes and Colistin Resistance in Gram-Negative Bacteria During the COVID-19 Pandemic in Mexico: Results from the Invifar Network

In this study, we report the carbapenemase-encoding genes and colistin resistance in Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa in the second year of the COVID-19 pandemic. Clinical isolates included carbapenem-resistant K. pneumoniae, carbapenem-resistant E. coli, carbapenem-resistant A. baumannii, and carbapenem-resistant P. aeruginosa. Carbapenemase-encoding genes were detected by PCR. Carbapenem-resistant K. pneumoniae and carbapenem-resistant E. coli isolates were analyzed using the Rapid Polymyxin NP assay. mcr genes were screened by PCR. Pulsed-field gel electrophoresis and whole-genome sequencing were performed on representative isolates. A total of 80 carbapenem-resistant E. coli, 103 carbapenem-resistant K. pneumoniae, 284 carbapenem-resistant A. baumannii, and 129 carbapenem-resistant P. aeruginosa isolates were recovered. All carbapenem-resistant E. coli and carbapenem-resistant K. pneumoniae isolates were included for further analysis. A selection of carbapenem-resistant A. baumannii and carbapenem-resistant P. aeruginosa strains was further analyzed (86 carbapenem-resistant A. baumannii and 82 carbapenem-resistant P. aeruginosa). Among carbapenem-resistant K. pneumoniae and carbapenem-resistant E. coli isolates, the most frequent gene was bla_NDM (86/103 [83.5%] and 72/80 [90%], respectively). For carbapenem-resistant A. baumannii, the most frequently detected gene was bla_OXA-40 (52/86, 60.5%), and for carbapenem-resistant P. aeruginosa, was bla_VIM (19/82, 23.2%). For carbapenem-resistant A. baumannii, five indistinguishable pulsotypes were detected. Circulation of K. pneumoniae New Delhi metallo-β-lactamase (NDM) and E. coli NDM was detected in Mexico. High virulence sequence types (STs), such as K. pneumoniae ST307, E. coli ST167, P. aeruginosa ST111, and A. baumannii ST2, were detected. Among K. pneumoniae isolates, 18/101 (17.8%) were positive for the Polymyxin NP test (two, 11.0% positive for the mcr-1 gene, and one, 5.6% with disruption of the mgrB gene). All E. coli isolates were negative for the Polymyxin NP test. In conclusion, K. pneumoniae NDM and E. coli NDM were detected in Mexico, with the circulation of highly virulent STs. These results are relevant in clinical practice to guide antibiotic therapies considering the molecular mechanisms of resistance to carbapenems.

649. Evaluation of the NG-Test CARBA 5® in Enterobacteriaceae and P. aeruginosa from Clinical Isolates

Background

Identification of carbapenemase-producing organisms like Enterobacteriaceae and P. aeruginosa is important for treatment decisions and infection control. Identification methods require time and technical training. Lateral flow immunoassay NG-Test CARBA 5® exempt these needs. In Mexico there is no evaluation of it on clinical isolates. It is important to define their diagnostic accuracy.

Methods

We collected 103 clinical strains of Enterobacteriaceae and P. aeruginosa resistant to carbapenems, from 2019 to 2020 from: National Institute of Rehabilitation (INR), National Institute of Cancerology, General Hospital Dr. Manuel Gea González and Hospital Civil de Guadalajara Fray Antonio Mayor. Analyzed in INR’s microbiology laboratory, resistance was corroborated with broth Microdilution Method (CLSI 2020). The carbapenemases was demonstrated by phenotypic methods (CLSI 2021). A homemade PCR was done and sequencing for encoding genes: NDM, KPC, GES, VIM, IMP and OXA-48-like. We analyzed concordance of the NG-Test CARBA 5® versus PCR with kappa coefficient.

Results

Seven discarded, 96 strains entered the analysis: Enterobacteriaceae (73%), P. aeruginosa (27%) (Table1). The carbapenemase-producing organisms were: 1) 56 Enterobacteriaceae, 30% Class B; 2) 23 P. aeruginosa, 90% Class B. NG-Test CARBA 5® for Enterobacteriaceae demonstrated greater sensitivity, specificity, and NPV (table 2). Kappa coefficient of concordance was 0.92 for Enterobacteriaceae and 0.59 for P. aeruginosa (table 2), and discrepancies in table 3. Sequencing of carbapenemase-producing organisim can be find in table 4.

Title 1. Clinical isolates by hospital

Conclusion

The most frequent enzyme were Ambler Class B, consistent with national reports. Sensitivity and specificity was like reported in other series. In P. aeruginosa, errors have already been reported in IMP-type enzymes, ours mainly with IMP-75. To our knowledge there are no reports of the following enzyme variants identified by NG-Test CARBA 5®: KPC-82, VIM-67, IMP-62, and IMP-75. NG-Test CARBA 5® showed high concordance with PCR for Enterobacteriaceae, it has the advantage of being a quick and easy-to-use detection tool. In P. aeruginosa despite the results without solid evidence, we recommend complementing the test with other phenotypic identification tests.

Table 2. Kappa Concordance Coefficient of NG-Test CARBA 5® and PCR

Disclosures

All Authors: No reported disclosures

236. Insight of Polymicrobial Prosthetic Joint Infections at a Referral Hospital

Background

Approximately one-third of the prosthetic joint infections (PJIs) are polymicrobial. They are difficult to treat and there is an urgent need of clinical evidence that help to guide current protocols. We aimed to define the clinical characteristics and outcomes of patients with polymicrobial PJI.

Methods

We conducted a retrospective cohort study of patients with polymicrobial PJI treated at a referral hospital in Mexico City. Clinical data was retrieved and analyzed. Time to treatment failure, was evaluated for all cases.

Results

We identified 166 patients with a polymicrobial PJI from July 2011 to October 2020. The median follow-up period was 3.24 years (IQR, 1.45-6.42). Fistulae (77.7%) and pain (76.5%) were frequent. Patients required a median of 2 (IQR, 1-3) hospitalizations and 3 (IQR, 1-5) surgeries. Relapse, reinfection, and amputation ocurred in 21.1% (35), 10.2% (17), and 7.2% (12) of the cases, respectively. At 1-year follow-up 38.47% (63) patients failed to control the infection. At 2 and 5-year follow-up this rate increased to 50% (83) and 68% (112), respectively. The main infecting microorganisms were Staphylococcus epidermidis (51.8%), Enterococcus faecalis (47.6%), and Staphyloccocus aureus (34.9%). Anaerobes were identified in 38 (22.9%) cases. At 1 and 5-year follow-up, 39.31% (34) and 71.1% (61) of patients with S. epidermidis experienced treatment failure. On the other hand, those with S. aureus showed lower rates (log-rank p-value=0.03): 24.85% (14) and 50% (29), accordingly. Patients affected by anaerobes and E. faecalis exhibited similar trends, between them (log-rank p-value=0.73).

Table1. Clinical findings of patients with polymicrobial PJI.

Frequency distributions of sociodemographic factors, comorbidities, clinical presentation, outcomes, out-patient treatment, and etiology in patients with polymicrobial PJI. Data is presented as absolute frequency followed by relative frequency enclosed in parenthesis, otherwise specified. Abbreviations: SXT, Trimethoprim/Sulfamethoxazole.

Figure 1. Kaplan‒Meier survivorship curve illustrating the time to treatment failure among patients with polymicrobial PJI. The shaded areas surrounding the gross line represent the 95% CI.

Figure2. Kaplan‒Meier survivorship curves illustrating the time to treatment failure among patients with polymicrobial PJI, according to the infecting microorganisms..

Patients affected by S. epidermidis, E.faecalis, S. aureus, and anaerobes are represented with red, blue, green, and black lines, respectively.

Conclusion

Our study showed 61.53% of the patients with polymicrobial PJI controlled the infection at 1-year follow-up. This rate decreased over the years. These patients required a considerable number of hospitalizations and surgeries. Likewise, presenting with fistulae and pain ensured a high suspicion of PJI. S. epidermidis, E. faecalis, and S. aureus were the most frequent infecting microorganisms. The stratification of our cohort suggested the microbiology of polymicrobial PJI could have driven to differences in rates of treatment failure.

Disclosures

All Authors: No reported disclosures

Randomized Controlled Trial to Reduce Bacterial Colonization of Surgical Drains with the Use of Chlorhexidine-Coated Dressings After Breast Cancer Surgery

BACKGROUND

Breast surgery is considered a clean surgery. However, surgical-site infection (SSI) rates are currently higher than predicted. Postoperative drains remain in situ for several days, with inevitable bacterial colonization and increased SSI risk.

METHODS

This randomized controlled trial from October 2016 to January 2018 analyzed patients undergoing breast cancer surgery. The patients were randomized to either the standard drain care group or the antiseptic dressing group (3M® Tegaderm® CHG). Drain samples taken on postoperative days (PODs) 7 and 14 were cultured as standardized in the laboratory. Colonization rates and SSI were compared between the two groups.

RESULTS

The study enrolled 104 patients with 167 surgical drains. The patients' clinical characteristics were similar in the two groups, with no statistically significant differences. Bulb fluid cultures at postoperative week (POW) 1 were positive for 42.9% of the control group and 28.9% of the antiseptic group (p = 0.06). Cultures from the POW 2 assessment were positive for 79.7% of the control group versus 54.9% of the antiseptic group (p = 0.001). Cultures from drain tubes were positive for 79.8% of the control group and 50.7% of the antiseptic group (p = < 0.001). In 11 patients, an SSI developed, 3 (5.8%) from the intervention and 8 (15.4%) from the control procedure (p = 0.11).

CONCLUSION

The study findings demonstrated that the use of antiseptics at the drain exit site significantly reduced bacterial colonization of the closed drainage system in breast cancer surgery. Semi-permeable occlusive chlorhexidine-impregnated dressings provide an opportunity to test simple, safe, and low-cost interventions that may reduce drain bacterial colonization and SSI after breast surgery.

Absence of Measles Virus Detection from Stapes of Patients with Otosclerosis

Objective To determine molecularly the presence of measles virus genetic material in the stapes of patients with otosclerosis. Study Design A cross-sectional study. Setting A tertiary referral hospital. Subjects and Methods Genetic material was extracted from the stapes of patients with otosclerosis (n = 93) during the period from March 2011 to April 2012. The presence of viral measles sequences was evaluated by the real-time reverse transcriptase polymerase chain reaction (RT-PCR). The expression of the CD46 gene was determined. Results Ninety-three patients were included in the study. No sample was positive for any of 3 measles virus genes (H, N, and F). Measles virus RNA was not detected in any sample by real-time RT-PCR. CD46 levels were positive in 3.3% (n = 3) and negative in 96.7% (n = 90). Conclusion This study does not support the theory of measles virus as the cause of otosclerosis. It is necessary to do more research about other causal theories to clarify its etiology and prevention.