Could the Adoptive Transfer of Memory Lymphocytes be an Alternative Treatment for Acinetobacter baumannii Infections?

We evaluated the efficacy of the adoptive transfer of memory B, CD4+, and CD8+ T lymphocytes compared with sulbactam and tigecycline in an experimental murine pneumonia model by two multidrug-resistant Acinetobacter baumannii strains, colistin-susceptible AbCS01 and colistin-resistant AbCR17. Pharmacodynamically optimized antimicrobial dosages were administered for 72 h, and intravenous administration of 2 × 106 of each of the memory cells in a single dose 30 min post-infection. Bacterial lung and blood counts and mortality rates were analyzed. Results showed that a single dose of memory B or CD4+ T cells was as effective as sulbactam in terms of bacterial clearance from the lungs and blood compared with the untreated mice or the tigecycline-treated mice inoculated with the AbCS01 strain. In the pneumonia model by AbCR17, a single dose of memory B or CD4+ T cells also reduced the bacterial load in the lungs compared with both antibiotic groups and was more efficacious than tigecycline in terms of blood clearance. Regarding survival, the adoptive transfer of memory B or CD4+ T cells was as effective as three days of sulbactam treatment for both strains. These data suggest that adoptive memory cell transfer could be a new effective treatment of multidrug-resistant A. baumannii infections.

Effects of pH on the Pathogenicity of Escherichia coli and Klebsiella pneumoniae on the Kidney: In Vitro and In Vivo Studies.

Urine pH reflects the functional integrity of the body and may influence the virulence of uropathogenic Escherichia coli and Klebsiella pneumoniae, the main causes of urinary tract infections (UTIs). This study evaluated the effects of acidic pH on the pathogenicity of uropathogenic E. coli and K. pneumoniae strains, in vitro and in vivo. Four uropathogenic E. coli and four K. pneumoniae strains were used. Biofilm formation, growth competition indices, motility, and adhesion and invasion of human renal cells were analyzed in media with acidic, neutral, and alkaline pH. A murine lower UTI model was used, with urine adjusted to acidic, neutral, or alkaline pH. At acidic pH, E. coli and K. pneumoniae exhibited higher bacterial concentrations in the kidneys and systemic symptoms, including bacteremia. Alkaline urine pH did not affect bacterial concentrations of any strain. In mice with UTIs caused by E. coli Nu14 and K. pneumoniae HUVR42 and acidic urine pH, histopathological studies of the kidneys showed acute inflammation affecting the urothelium and renal parenchyma, which are traits of acute pyelonephritis. These results indicate that acidic pH could increase the pathogenicity of E. coli and K. pneumoniae in murine models of lower UTI, promoting renal infection and acute inflammation.

Clinical and Ecological Impact of an Educational Program to Optimize Antibiotic Treatments in Nursing Homes (PROA-SENIOR): A Cluster, Randomized, Controlled Trial and Interrupted Time-Series Analysis.

BACKGROUND: Antimicrobial stewardship programs (ASPs) are recommended in nursing homes (NHs), although data are limited. We aimed to determine the clinical and ecological impact of an ASP for NHs. METHODS: We performed a cluster, randomized, controlled trial and a before-after study with interrupted time-series analyses in 14 NHs for 30 consecutive months from July 2018 to December 2020 in Andalusia, Spain. Seven facilities implemented an ASP with a bundle of 5 educational measures (general ASP) and 7 added 1-to-1 educational interviews (experimental ASP). The primary outcome was the overall use of antimicrobials, calculated monthly as defined daily doses (DDD) per 1000 resident days (DRD). RESULTS: The total mean antimicrobial consumption decreased by 31.2% (-16.72 DRD; P = .045) with respect to the preintervention period; the overall use of quinolones and amoxicillin-clavulanic acid dropped by 52.2% (P = .001) and 42.5% (P = .006), respectively; and the overall prevalence of multidrug-resistant organisms (MDROs) decreased from 24.7% to 17.4% (P = .012). During the intervention period, 12.5 educational interviews per doctor were performed in the experimental ASP group; no differences were found in the total mean antimicrobial use between groups (-14.62 DRD; P = .25). Two unexpected coronavirus disease 2019 waves affected the centers increasing the overall mean use of antimicrobials by 40% (51.56 DRD; P < .0001). CONCLUSIONS: This study suggests that an ASP for NHs appears to be associated with a decrease in total consumption of antimicrobials and prevalence of MDROs. This trial did not find benefits associated with educational interviews, probably due to the coronavirus disease 2019 pandemic. Clinical Trials Registration. NCT03543605.

Role of PstS in the Pathogenesis of Acinetobacter baumannii Under Microaerobiosis and Normoxia.

Acinetobacter baumannii is a successful pathogen responsible for infections with high mortality rate. During the course of infection it can be found in microaerobic environments, which influences virulence factor expression. From a previous transcriptomic analysis of A. baumannii ATCC 17978 under microaerobiosis, we know the gene pstS is overexpressed under microaerobiosis. Here, we studied its role in A. baumannii virulence. pstS loss significantly decreased bacterial adherence and invasion into A549 cells and increased A549 cell viability. pstS loss also reduced motility and biofilm-forming ability of A. baumannii. In a peritoneal sepsis murine model, the minimum lethal dose required by A. baumannii ATCC 17978 ΔpstS was lower compared to the wild type (4.3 vs 3.2 log colony forming units/mL, respectively), and the bacterial burden in tissues and fluids was lower. Thus, the loss of the phosphate sensor PstS produced a decrease in A. baumannii pathogenesis, supporting its role as a virulence factor.

Extended-spectrum resistance to ß-lactams/ß-lactamase inhibitors (ESRI) evolved from low-level resistant Escherichia coli.

OBJECTIVES: Escherichia coli is characterized by three resistance patterns to ß-lactams/ß-lactamase inhibitors (BLs/BLIs): (i) resistance to ampicillin/sulbactam and susceptibility to amoxicillin/clavulanic acid and piperacillin/tazobactam (RSS); (ii) resistance to ampicillin/sulbactam and amoxicillin/clavulanic acid, and susceptibility to piperacillin/tazobactam (RRS); and (iii) resistance to ampicillin/sulbactam, amoxicillin/clavulanic acid and piperacillin/tazobactam (RRR). These resistance patterns are acquired consecutively, indicating a potential risk of developing resistance to piperacillin/tazobactam, but the precise mechanism of this process is not completely understood. METHODS: Clinical isolates incrementally pressured by piperacillin/tazobactam selection in vitro and in vivo were used. We determined the MIC of piperacillin/tazobactam in the presence and absence of piperacillin/tazobactam pressure. We deciphered the role of the blaTEM genes in the new concept of extended-spectrum resistance to BLs/BLIs (ESRI) using genomic analysis. The activity of ß-lactamase was quantified in these isolates. RESULTS: We show that piperacillin/tazobactam resistance is induced in E. coli carrying blaTEM genes. This resistance is due to the increase in copy numbers and transcription levels of the blaTEM gene, thus increasing ß-lactamase activity and consequently increasing piperacillin/tazobactam MICs. Genome sequencing of two blaTEM-carrying representative isolates showed that piperacillin/tazobactam treatment produced two types of duplications of blaTEM (8 and 60 copies, respectively). In the clinical setting, piperacillin/tazobactam treatment of patients infected by E. coli carrying blaTEM is associated with a risk of therapeutic failure. CONCLUSIONS: This study describes for the first time the ESRI in E. coli. This new concept is very important in the understanding of the mechanism involved in the acquisition of resistance to BLs/BLIs.

Exploration of piperazine-derived thioureas as antibacterial and anti-inflammatory agents. In vitro evaluation against clinical isolates of colistin-resistant Acinetobacter baumannii.

A. baumannii is one of the most important multidrug-resistant microorganisms in hospital units. It is resistant to many classes of antibiotics and the development of new therapeutic strategies is necessary. The aim of this study was to evaluate the antibacterial activity of a set of piperazine-derived thioureas against 13 clinical strains of colistin-resistant A. baumannii. Six derivatives were identified to inhibit bacterial growth of 46% of the A. baumannii strains at low micromolar concentrations (Minimum Inhibitory Concentration from 1.56 to 6.25 µM). A common structural feature in most active compounds was the presence of a 3,5-bis-trifluoromethyl phenyl ring at the thiourea function. In addition, the ability of the compounds to inhibit production of nitric oxide (NO) was examined in RAW 264.7 murine macrophages, highlighting the potential of piperazine-derived thioureas as promising scaffolds for the design of new combined anti-bacterial/anti-inflammatory agents.

Discovery of niclosamide and its O-alkylamino-tethered derivatives as potent antibacterial agents against carbapenemase-producing and/or colistin resistant Enterobacteriaceae isolates.

Carbapenemase-producing Enterobacteriaceae (CPE) represents the most worrisome evolution of the antibiotic resistance crisis, which is almost resistant to most of available antibiotics. This situation is getting even worse particularly due to the recent emergence of colistin resistance. Herein, niclosamide, an FDA-approved traditional drug, and its novel O-alkylamino-tethered derivatives were discovered as new and potent antibacterial agents against carbapenemase-producing and/or colistin resistant Enterobacteriaceae isolates. Among these molecules, compound 10 (HJC0431) with 4-aminobutyl moiety showed the broad antibacterial activities, effective against 6 strains. In vitro checkerboard and time-kill course studies demonstrated the synergistic effects of the screened compounds with colistin against the corresponding strains with various degrees.

Prevalence and clinical impact of Streptococcus pneumoniae nasopharyngeal carriage in solid organ transplant recipients.

BACKGROUND: S. pneumoniae is the leading cause of community-acquired pneumonia in the solid organ transplant recipient (SOTR); nevertheless, the prevalence of colonization and of the colonizing/infecting serotypes has not been studied in this population. In this context, the aim of the present study was to describe the rate, characteristics, and clinical impact of S. pneumoniae nasopharyngeal carriage. METHODS: A prospective observational cohort of Solid Organ Transplant recipients (SOTR) was held at the University Hospital Virgen del Rocío, Seville, Spain with the aim to evaluate the S. pneumoniae colonization and the serotype prevalence in SOTR. Two different pharyngeal swabs samples from 500 patients were included in two different seasonal periods winter and spring/summer. Optochin and bile solubility tests were performed for the isolation of thew strains. Antimicrobial susceptibility studies (MICs, mg/l) of levofloxacin, trimethoprim-sulfamethoxazole, penicillin, amoxicillin, cefotaxime, ceftriaxone, erythromycin, azithromycin and vancomycin for each isolate were determined by E-test strips. Capsular typing was done by sequential multiplex PCR reactions. A multivariate logistic regression analysis of factors potentially associated with pneumococcal nasopharyngeal carriage and disease was performed. RESULTS: Twenty-six (5.6%) and fifteen (3.2%) patients were colonized in winter and spring/summer periods, respectively. Colonized SOT recipients compared to non-colonized patients were more frequently men (79.5% vs. 63.1%, P < 0.05) and cohabitated regularly with children (59% vs. 32.2%, P < 0.001). The most prevalent serotype in both studied periods was 35B. Forty-five percent of total isolates were included in the pneumococcal vaccine PPV23. Trimethoprim-sulfamethoxazole and macrolides were the less active antibiotics. Three patients had non-bacteremic pneumococcal pneumonia, and two of them died. CONCLUSIONS: Pneumococcal colonization in SOTR is low with the most colonizing serotypes not included in the pneumococcal vaccines.

Effect of Hypoxia on the Pathogenesis of Acinetobacter baumannii and Pseudomonas aeruginosa In Vitro and in Murine Experimental Models of Infection.

Hypoxia modulates bacterial virulence and the inflammation response through hypoxia-inducible factor 1α (HIF-1α). Here we study the influence of hypoxia on Acinetobacter baumannii and Pseudomonas aeruginosa infections. In vitro, hypoxia increases the bactericidal activities of epithelial cells against A. baumannii and P. aeruginosa, reducing extracellular bacterial concentrations to 50.5% ± 7.5% and 90.8% ± 13.9%, respectively, at 2 h postinfection. The same phenomenon occurs in macrophages (67.6% ± 18.2% for A. baumannii at 2 h and 50.3% ± 10.9% for P. aeruginosa at 24 h). Hypoxia decreases the adherence of A. baumannii to epithelial cells (42.87% ± 8.16% at 2 h) and macrophages (52.0% ± 18.7% at 24 h), as well as that of P. aeruginosa (24.9% ± 4.5% in epithelial cells and 65.7% ± 5.5% in macrophages at 2 h). Moreover, hypoxia decreases the invasion of epithelial cells (48.6% ± 3.8%) and macrophages (8.7% ± 6.9%) by A. baumannii at 24 h postinfection and by P. aeruginosa at 2 h postinfection (75.0% ± 16.3% and 63.4% ± 5.4%, respectively). In vivo, hypoxia diminishes bacterial loads in fluids and tissues in animal models of infection by both pathogens. In contrast, mouse survival time was shorter under hypoxia (23.92 versus 36.42 h) with A. baumannii infection. No differences in the production of cytokines or HIF-1α were found between hypoxia and normoxia in vitro or in vivo We conclude that hypoxia increases the bactericidal activities of host cells against both pathogens and reduces the interaction of pathogens with host cells. Moreover, hypoxia accelerates the rate at which animals die despite the lower bacterial concentrations in vivo.

Synergistic activity of an OmpA inhibitor and colistin against colistin-resistant Acinetobacter baumannii: mechanistic analysis and in vivo efficacy.

Objectives: Preventing bacterial contact with host cells can provide an additional approach to tackling MDR Acinetobacter baumannii. Recently, we identified AOA-2 as a potential blocker of A. baumannii outer membrane protein A without presenting bactericidal activity. Here, we aimed to study whether AOA-2 can increase the activity of colistin against colistin-resistant A. baumannii in vitro and in vivo. Methods: Reference and clinical A. baumannii strains susceptible and resistant to colistin (CST-S and CST-R) were used. Microdilution and time-kill curve assays were performed to determine the synergy between AOA-2 and colistin. SDS-PAGE assays with CST-S and CST-R outer membrane proteins and MALDI-TOF-TOF (MS-MS/MS) analysis were performed to determine the AOA-2 and colistin synergy mechanism. In a murine peritoneal sepsis model, the therapeutic efficacy of AOA-2 (10 mg/kg/24 h) in combination with a sub-optimal dose of colistin (10 mg/kg/24 h) against CST-R was evaluated by determining the bacterial load in tissues and blood, and mouse survival. Results: We showed that AOA-2 increased the in vitro colistin susceptibility of reference and clinical CST-S and CST-R strains. This combination also enhanced their killing activity after 24 h of drug exposure. This synergy is mediated by the overexpression of Omp25. In vivo, the combination of AOA-2 with colistin significantly reduced the bacterial load in tissues and blood, and increased mouse survival, compared with colistin monotherapy. Conclusions: We identified a novel class of antimicrobial agents that has proven to be effective in combination with colistin in an experimental model of severe infection by CST-R A. baumannii.

Overproduction of Outer Membrane Protein A by Acinetobacter baumannii as a Risk Factor for Nosocomial Pneumonia, Bacteremia, and Mortality Rate Increase.

Background: Outer membrane protein A (OmpA) is a porin involved in Acinetobacter baumannii pathogenesis. However, OmpA clinical implication in hospital-acquired infections remains unknown. We aimed to determine whether OmpA overproduction was a risk factor associated with pneumonia, bacteremia, and mortality. Methods: We analyzed demographic, microbiological, and clinical data from 100 patients included in a unicenter cohort and 246 included in a unicenter cohort and a multicenter cohort. Representative isolates were classified into 2 groups: (1) isolates from patients colonized by A. baumannii (16 from the unicenter and 20 from the multicenter cohort) and (2) isolates from bacteremic or nonbacteremic patients with pneumonia (PP) caused by A. baumannii (13 from the unicenter and 23 from the multicenter cohort) Expression of ompA was determined with quantitative reverse-transcription polymerase chain reaction. Results: Isolates from PP overexpressed more ompA than those from colonized patients from the unicenter (ratio, 1.76 vs 0.36; P < .001) and the multicenter (1.36 vs 0.91; P = .03) cohorts. Among isolates from PP, those from bacteremic patients overexpressed nonsignificantly more ompA than those from nonbacteremic patients in the unicenter (ratio, 2.37 vs 1.43; P = .06) and the multicenter (2.03 vs 0.91; P = .14) cohorts. Multivariate analysis in both cohorts together showed ompA overexpression as independent risk factor for pneumonia (P < .001), bacteremia (P = .005), and death (P = .049). Conclusions: These data suggest that ompA overexpression is an associated factor for pneumonia, bacteremia, and death due to A. baumannii.

Common variants in BDNF, FAIM2, FTO, MC4R, NEGR1, and SH2B1 show association with obesity-related variables in Spanish Roma population.

OBJECTIVES: The objective of this study is to investigate the association between previously GWAS identified genetic variants predisposing to obesity in Europeans and obesity-related phenotypes in Roma population. METHODS: A total of 24 representative single nucleotide polymorphisms (SNPs) were genotyped in 372 individuals belonging to 50 extended families of Roma population. SNPs were tested for association with seven quantitative obesity-related phenotypes in the PLINK program. RESULTS: Risk variants in NEGR1, FAIM2, FTO, and SH2B1 genes were associated with increased adiposity accumulation in Roma population with effect sizes between 0.21 and 0.34 Z-scores for each copy of the BMI increasing allele. Additionally, variants in BDNF and MC4R were significantly associated with adiposity distribution but not with overall fatness. No significant association was detected between obesity-related phenotypes and variants in the first intron of the FTO gene (e.g., rs9939609). CONCLUSIONS: The results of this study suggest that SNPs in or near six genes (BDNF, FAIM2, FTO, MC4R, NEGR1, and SH2B1) are significantly associated with body fat accumulation and distribution in Roma people. However, the association observed among variants in the first intron of FTO and obesity in European derived populations is not evident in the analyzed Roma sample.

Obesity and body size perceptions in a Spanish Roma population.

BACKGROUND: Roma people are particularly vulnerable to developing overweight and obesity. Self-perception of body image may influence the prevalence of obesity in this ethnic minority. AIM: The objectives of this study are to estimate the prevalence of obesity, to analyse body size perceptions and preferences and to assess the relationship between body size perceptions and obesity in the Roma population. SUBJECTS AND METHODS: The analyses were carried out on 372 men, women and children from the Roma population residing in the Greater Bilbao region (Basque Country, Spain). In adults, a standard figural scale was used to analyse body size perceptions and preferences in this ethnic minority. RESULTS: Overall 51.7% of adult and 24.4% of minor Roma individuals were obese. Both Roma men and women had inaccurate self-perceptions of their body size. Significant differences on body size perceptions were detected based on age, sex, nutritional status and socioeconomic characteristics. CONCLUSION: This Roma population presents one of the highest rates of obesity worldwide. Although a certain awareness of the correct weight status was appreciated, the inability of Roma individuals to see themselves as overweight or obese may be a significant factor on the high prevalence of obesity in this population.

Assessing the Influence of Urine pH on the Efficacy of Ciprofloxacin and Fosfomycin in Immunocompetent and Immunocompromised Murine Models of Escherichia coli and Klebsiella pneumoniae Infection in the Lower Urinary Tract.

In vitro studies have suggested that acidic pH may reduce and increase the efficacy of ciprofloxacin and fosfomycin, respectively, when used to treat Escherichia coli and Klebsiella pneumoniae infections. We assessed the effects of acidic, neutral, and alkaline urine pH on the efficacy of optimized ciprofloxacin and fosfomycin dosages in UTI murine model of E. coli and K. pneumoniae. Immunocompetent and immunocompromised mice with adjusted urine pH were inoculated with E. coli and K. pneumoniae strains, and the efficacy was assessed based on the bacterial concentrations in tissues and fluids at 72 h, with respect to untreated controls. At acidic urine pH, both antimicrobials were effective, achieving similar reductions in E. coli concentrations in the kidneys in immunocompetent and immunocompromised mice and in K. pneumoniae in immunocompetent mice. At a neutral urine pH, both therapies reduced the presence of E. coli in the kidneys of immunocompetent mice. However, in immunocompromised mice, antimicrobials were ineffective at treating E. coli infection in the kidneys at a neutral urine pH and showed reduced efficacy against K. pneumoniae at both acidic and neutral urine pH. The results showed no correlation between urine pH and antimicrobial efficacy, suggesting that the reduced effectiveness is associated with the animals' immunocompetence status.

Mitomycin C as an Anti-Persister Strategy against Klebsiella pneumoniae: Toxicity and Synergy Studies.

The combination of several therapeutic strategies is often seen as a good way to decrease resistance rates, since bacteria can more easily overcome single-drug treatments than multi-drug ones. This strategy is especially attractive when several targets and subpopulations are affected, as it is the case of Klebsiella pneumoniae persister cells, a subpopulation of bacteria able to transiently survive antibiotic exposures. This work aims to evaluate the potential of a repurposed anticancer drug, mitomycin C, combined with the K. pneumoniae lytic phage vB_KpnM-VAC13 in vitro and its safety in an in vivo murine model against two clinical isolates of this pathogen, one of them exhibiting an imipenem-persister phenotype. At the same time, we verified the absence of toxicity of mitomycin C at the concentration using the human chondrocyte cell line T/C28a2. The viability of these human cells was checked using both cytotoxicity assays and flow cytometry.

Acidic Urine pH and Clinical Outcome of Lower Urinary Tract Infection in Kidney Transplant Recipients Treated with Ciprofloxacin and Fosfomycin.

Different factors, including antimicrobial resistance, may diminish the effectiveness of antibiotic therapy, challenging the management of post-transplant urinary tract infection (UTI). The association of acidic urine pH with microbiological and clinical outcomes was evaluated after fosfomycin or ciprofloxacin therapy in 184 kidney transplant recipients (KTRs) with UTI episodes by Escherichia coli (N = 115) and Klebsiella pneumoniae (N = 69). Initial urine pH, antimicrobial therapy, and clinical and microbiological outcomes, and one- and six-month follow-up were assessed. Fosfomycin was prescribed in 88 (76.5%) E. coli and 46 (66.7%) K. pneumoniae UTI episodes in the total cohort. When the urine pH ≤ 6, fosfomycin was prescribed in 60 (52.2%) E. coli and 29 (42.0%) K. pneumoniae. Initial urine pH ≤ 6 in E. coli UTI was associated with symptomatic episodes (8/60 vs. 0/55, p = 0.04) at one-month follow-up, with a similar trend in those patients receiving fosfomycin (7/47 vs. 0/41, p = 0.09). Acidic urine pH was not associated with microbiological or clinical cure in K. pneumoniae UTI. At pH 5, the ciprofloxacin MIC90 increased from 8 to >8 mg/L in E. coli and from 4 to >8 mg/L in K. pneumoniae. At pH 5, the fosfomycin MIC90 decreased from 8 to 4 mg/L in E. coli and from 512 to 128 mg/L in K. pneumoniae. Acidic urine is not associated with the microbiological efficacy of fosfomycin and ciprofloxacin in KTRs with UTI, but it is associated with symptomatic UTI episodes at one-month follow-up in E. coli episodes.

Analysis of bacterial pangenomes reduces CRISPR dark matter and reveals strong association between membranome and CRISPR-Cas systems.

CRISPR-Cas systems are prokaryotic acquired immunity mechanisms, which are found in 40% of bacterial genomes. They prevent viral infections through small DNA fragments called spacers. However, the vast majority of these spacers have not yet been associated with the virus they recognize, and it has been named CRISPR dark matter. By analyzing the spacers of tens of thousands of genomes from six bacterial species, we have been able to reduce the CRISPR dark matter from 80% to as low as 15% in some of the species. In addition, we have observed that, when a genome presents CRISPR-Cas systems, this is accompanied by particular sets of membrane proteins. Our results suggest that when bacteria present membrane proteins that make it compete better in its environment and these proteins are, in turn, receptors for specific phages, they would be forced to acquire CRISPR-Cas.

The Lambda Variant in Argentina: Analyzing the Evolution and Spread of SARS-CoV-2 Lineage C.37.

The second wave of COVID-19 occurred in South America in early 2021 and was mainly driven by Gamma and Lambda variants. In this study, we aimed to describe the emergence and local genomic diversity of the SARS-CoV-2 Lambda variant in Argentina, from its initial entry into the country until its detection ceased. Molecular surveillance was conducted on 9356 samples from Argentina between October 2020 and April 2022, and sequencing, phylogenetic, and phylogeographic analyses were performed. Our findings revealed that the Lambda variant was first detected in Argentina in January 2021 and steadily increased in frequency until it peaked in April 2021, with continued detection throughout the year. Phylodynamic analyses showed that at least 18 introductions of the Lambda variant into the country occurred, with nine of them having evidence of onward local transmission. The spatial--temporal reconstruction showed that Argentine clades were associated with Lambda sequences from Latin America and suggested an initial diversification in the Metropolitan Area of Buenos Aires before spreading to other regions in Argentina. Genetic analyses of genome sequences allowed us to describe the mutational patterns of the Argentine Lambda sequences and detect the emergence of rare mutations in an immunocompromised patient. Our study highlights the importance of genomic surveillance in identifying the introduction and geographical distribution of the SARS-CoV-2 Lambda variant, as well as in monitoring the emergence of mutations that could be involved in the evolutionary leaps that characterize variants of concern.

Carbapenem Combinations for Infections Caused by Carbapenemase-Producing Pseudomonas aeruginosa: Experimental In Vitro and In Vivo Analysis.

In the context of difficult-to-treat carbapenem-resistant Pseudomonas aeruginosa infections, we evaluated imipenem, meropenem, and doripenem combinations against eleven carbapenemase-producing P. aeruginosa isolates. According to the widespread global distribution of high-risk clones and carbapenemases, four representative isolates were selected: ST175 (OXA-2/VIM-20), ST175 (VIM-2), ST235 (GES-5), and ST111 (IMP-33), for efficacy studies using a sepsis murine model. Minimum inhibitory concentration (mg/L) ranges were 64-256 for imipenem and 16-128 for meropenem and doripenem. In vitro, imipenem plus meropenem was synergistic against 72% of isolates and doripenem plus meropenem or imipenem against 55% and 45%, respectively. All combinations were synergistic against the ST175, ST235, and ST155 clones. In vivo, meropenem diminished the spleen and blood bacterial concentrations of four and three isolates, respectively, with better efficacy than imipenem or doripenem. The combinations did not show efficacy compared with the more active monotherapies, except for imipenem plus meropenem, which reduced the ST235 bacterial spleen concentration. Mortality decreased with imipenem plus meropenem or doripenem for the ST175 isolate. Results suggest that carbapenem combinations are not an alternative for severe infections by carbapenemase-producing P. aeruginosa. Meropenem monotherapy showed in vivo efficacy despite its high MIC, probably because its dosage allowed a sufficient antimicrobial exposure at the infection sites.

IgM-enriched immunoglobulin improves colistin efficacy in a pneumonia model by Pseudomonas aeruginosa.

We evaluated the efficacy of ceftazidime or colistin in combination with polyclonal IgM-enriched immunoglobulin (IgM-IG), in an experimental pneumonia model (C57BL/6J male mice) using two multidrug-resistant Pseudomonas aeruginosa strains, both ceftazidime-susceptible and one colistin-resistant. Pharmacodynamically optimised antimicrobials were administered for 72 h, and intravenous IgM-IG was given as a single dose. Bacterial tissues count and the mortality were analysed. Ceftazidime was more effective than colistin for both strains. In mice infected with the colistin-susceptible strain, ceftazidime reduced the bacterial concentration in the lungs and blood (-2.42 and -3.87 log10 CFU/ml) compared with colistin (-0.55 and -1.23 log10 CFU/ml, respectively) and with the controls. Colistin plus IgM-IG reduced the bacterial lung concentrations of both colistin-susceptible and resistant strains (-2.91 and -1.73 log10 CFU/g, respectively) and the bacteraemia rate of the colistin-resistant strain (-44%). These results suggest that IgM-IG might be useful as an adjuvant to colistin in the treatment of pneumonia caused by multidrug-resistant P. aeruginosa.