Evaluation of an automated rapid phenotypic antimicrobial susceptibility testing (ASTar, Q-linea AB) applied directly on blood cultures bottles positive for Gram-negative pathogens.

We evaluated the performance of a new rapid phenotypic antimicrobial susceptibility test (ASTar; Q-linea AB) on Gram-negative bacilli, directly from positive blood cultures bottles. MIC values obtained by the routine reference method (Microscan, Beckman Coulter) were compared to the ones provided by the tested method (ASTar). ASTar demonstrated an overall essential agreement of 98% and a category agreement of 96.1%. The overall rate of major errors and very major errors was 2.5% and 3.3%, respectively. ASTar can represent a rapid, simple, and reliable method to speed up information about antimicrobial susceptibility of Gram-negative pathogens from positive blood culture bottles.

Antimicrobial resistance determinants in the oropharyngeal microbiome of 'men having sex with men' attending an sexually transmitted infection clinic.

BACKGROUND: 'Men having sex with men' (MSM) represent a key population with a significant prevalence of pharyngeal Neisseria gonorrhoeae (NG) infections and a high rate of antimicrobial resistance genes in the pharyngeal microbiome. As NG can acquire antibiotic resistance genes from other commensal oropharyngeal bacteria, monitoring the prevalence of these resistance determinants is critical to curtail the spread of NG-resistant strains. PURPOSE AND RESEARCH DESIGN: Here, we assessed the distribution of five resistance genes (pen (A), mtr (R), gyr (A), par (C), msr (D)) in the oropharynx of 164 MSM, attending an Outpatient clinic for STI screening. RESULTS: The most frequently detected resistance gene was msr (D) (88.4%), followed by gyr (A) (67.1%). The distribution of resistance genes was not influenced by pharyngeal gonorrhea nor by the HIV status, whereas a younger age was associated with mtr (R) presence (p = .008). Subjects using mouthwash exhibited significantly lower levels of mtr (R) (p = .0005). Smoking habit was associated with a higher prevalence of par (C) (p = .02). A noteworthy association was observed between the presence of msr (D) gene and the use of antibiotics (p = .014). CONCLUSIONS: Our findings reveal an enrichment of antimicrobial resistance genes in the oropharynx of MSM. These insights could aid in the development of screening programs and antimicrobial stewardship initiatives targeting populations at heightened risk of pharyngeal gonorrhea.

Potential value of a rapid syndromic multiplex PCR for the diagnosis of native and prosthetic joint infections: a real-world evidence study.

Introduction: The BIOFIRE Joint Infection (JI) Panel is a diagnostic tool that uses multiplex-PCR testing to detect microorganisms in synovial fluid specimens from patients suspected of having septic arthritis (SA) on native joints or prosthetic joint infections (PJIs). Methods: A study was conducted across 34 clinical sites in 19 European and Middle Eastern countries from March 2021 to June 2022 to assess the effectiveness of the BIOFIRE JI Panel. Results: A total of 1527 samples were collected from patients suspected of SA or PJI, with an overall agreement of 88.4 % and 85 % respectively between the JI Panel and synovial fluid cultures (SFCs). The JI Panel detected more positive samples and microorganisms than SFC, with a notable difference on Staphylococcus aureus, Streptococcus species, Enterococcus faecalis, Kingella kingae, Neisseria gonorrhoeae, and anaerobic bacteria. The study found that the BIOFIRE JI Panel has a high utility in the real-world clinical setting for suspected SA and PJI, providing diagnostic results in approximately 1 h. The user experience was positive, implying a potential benefit of rapidity of results' turnover in optimising patient management strategies. Conclusion: The study suggests that the BIOFIRE JI Panel could potentially optimise patient management and antimicrobial therapy, thus highlighting its importance in the clinical setting.

Human Campylobacter spp. infections in Italy.

PURPOSE: Campylobacter is a frequent cause of enteric infections with common antimicrobial resistance issues. The most recent reports of campylobacteriosis in Italy include data from 2013 to 2016. We aimed to provide national epidemiological and microbiological data on human Campylobacter infections in Italy during the period 2017-2021. METHODS: Data was collected from 19 Hospitals in 13 Italian Regions. Bacterial identification was performed by mass spectrometry. Antibiograms were determined with Etest or Kirby-Bauer (EUCAST criteria). RESULTS: In total, 5419 isolations of Campylobacter spp. were performed. The most common species were C. jejuni (n = 4535, 83.7%), followed by C. coli (n = 732, 13.5%) and C. fetus (n = 34, 0.6%). The mean age of patients was 34.61 years and 57.1% were males. Outpatients accounted for 54% of the cases detected. Campylobacter were isolated from faeces in 97.3% of cases and in 2.7% from blood. C. fetus was mostly isolated from blood (88.2% of cases). We tested for antimicrobial susceptibility 4627 isolates (85.4%). Resistance to ciprofloxacin and tetracyclines was 75.5% and 54.8%, respectively; resistance to erythromycin was 4.8%; clarithromycin 2% and azithromycin 2%. 50% of C. jejuni and C. coli were resistant to ≥ 2 antibiotics. Over the study period, resistance to ciprofloxacin and tetracyclines significantly decreased (p < 0.005), while resistance to macrolides remained stable. CONCLUSION: Campylobacter resistance to fluoroquinolones and tetracyclines in Italy is decreasing but is still high, while macrolides retain good activity.

Impact of a multidisciplinary management team on clinical outcome in ICU patients affected by Gram-negative bloodstream infections: a pre-post quasi-experimental study.

BACKGROUND: Bloodstream infections (BSIs) by Gram-negative pathogens play a major role in intensive care patients, both in terms of prevalence and severity, especially if multi-drug resistant pathogens are involved. Early appropriate antibiotic therapy is therefore a cornerstone in the management of these patients, and growing evidence shows that implementation of a multidisciplinary team may improve patients' outcomes. Our aim was to evaluate the clinical and microbiological impact of the application of a multidisciplinary team on critically ill patients. METHODS: Pre-post study enrolling critically ill patients with Gram negative bloodstream infection in intensive care unit. In the pre-intervention phase (from January until December 2018) patients were managed with infectious disease consultation on demand, in the post-intervention phase (from January until December 2022) patients were managed with a daily evaluation by a multidisciplinary team composed of intensivist, infectious disease physician, clinical pharmacologist and microbiologist. RESULTS: Overall, 135 patients were enrolled during the study period, of them 67 (49.6%) in the pre-intervention phase and 68 (50.4%) in the post-intervention phase. Median age was 67 (58-75) years, sex male was 31.9%. Septic shock, the need for continuous renal replacement therapy and mechanical ventilation at BSI onset were similar in both groups, no difference of multidrug-resistant organisms (MDRO) prevalence was observed. In the post-phase, empirical administration of carbapenems decreased significantly (40.3% vs. 62.7%, p = 0.02) with an increase of appropriate empirical therapy (86.9% vs. 55.2%, p < 0.001) and a decrease of overall antibiotic treatment (12 vs. 16 days, p < 0.001). Despite no differences in delta SOFA and all-cause 30-day mortality, a significant decrease in microbiological failure (10.3% vs. 29.9%, p = 0.005) and a new-onset 30-day MDRO colonization (8.3% vs. 36.6%, p < 0.001) in the post-phase was reported. At multivariable analysis adjusted for main covariates, the institution of a multidisciplinary management team (MMT) was found to be protective both for new MDRO colonization [OR 0.17, 95%CI(0.05-0.67)] and microbiological failure [OR 0.37, 95%CI (0.14-0.98)]. CONCLUSIONS: The institution of a MMT allowed for an optimization of antimicrobial treatments, reflecting to a significant decrease in new MDRO colonization and microbiological failure among critically ill patients.

Gut microbiome dynamics and Enterobacterales infection in liver transplant recipients: A prospective observational study.

Background & Aims: The aim of this study was to investigate gut microbiome (GM) dynamics in relation to carbapenem-resistant Enterobacterales (CRE) colonization, CRE infection, and non-CRE infection development within 2 months after liver transplant (LT). Methods: A single-center, prospective study was performed in patients undergoing LT from November 2018 to January 2020. The GM was profiled through 16S rRNA amplicon sequencing of a rectal swab taken on the day of transplantation, and fecal samples were collected weekly until 1 month after LT. A subset of samples was subjected to shotgun metagenomics, including resistome dynamics. The primary endpoint was to explore changes in the GM in the following groups: (1) CRE carriers developing CRE infection (CRE_I); (2) CRE carriers not developing infection (CRE_UI); (3) non-CRE carriers developing microbial infection (INF); and (4) non-CRE carriers not developing infection (NEG). Results: Overall, 97 patients were enrolled, and 91 provided fecal samples. Of these, five, nine, 22, and 55 patients were classified as CRE_I, CRE_UI, INF, and NEG, respectively. CRE_I patients showed an immediate and sustained post-LT decrease in alpha diversity, with depletion of the GM structure and gradual over-representation of Klebsiella and Enterococcus. The proportions of Klebsiella were significantly higher in CRE_I patients than in NEG patients even before LT, serving as an early marker of subsequent CRE infection. CRE_UI patients had a more stable and diverse GM, whose compositional dynamics tended to overlap with those of NEG patients. Conclusions: GM profiling before LT could improve patient stratification and risk prediction and guide early GM-based intervention strategies to reduce infectious complications and improve overall prognosis. Impact and implications: Little is known about the temporal dynamics of gut microbiome (GM) in liver transplant recipients associated with carbapenem-resistant Enterobacterales (CRE) colonization and infection. The GM structure and functionality of patients colonized with CRE and developing infection appeared to be distinct compared with CRE carriers without infection or patients with other microbial infection or no infection and CRE colonization. Higher proportions of antimicrobial-resistant pathogens and poor representation of bacteria and metabolic pathways capable of promoting overall host health were observed in CRE carriers who developed infection, even before liver transplant. Therefore, pretransplant GM profiling could improve patient stratification and risk prediction and guide early GM-based intervention strategies to reduce infectious complications and improve overall prognosis.

Antimicrobial Resistance of Genital Mycoplasma and Ureaplasma: A Multicentre Study Over a 5-Year Period in Italy (2017-2021).

Updated data on genital Mollicutes prevalence and antimicrobial susceptibility can help provide guidance for antibiotic stewardship and set up effective strategies for infection control policies. In this multicentre study, we assessed the prevalence and the resistance profile of Mycoplasma hominis (MH) and Ureaplasma species (U. parvum/U. urealyticum), analyzing data from 21,210 subjects who provided urogenital samples for Mollicutes detection by culture over a 5-year period (2017-2021) in two high-density urban areas in the North of Italy (i.e., Bologna and Lecco). Overall prevalence of Mollicutes infection was 22.3%, with women showing a significantly higher detection rate than men (p < 0.00001). The prevalence decreased with age (highest prevalence <30 years) and over the years considered. Ureaplasma strains were much more frequently detected (62.3%) compared to MH (8.3%) and to mixed infections (29.4%). Ureaplasma species showed high levels of ciprofloxacin resistance (39.5%), whereas MH strains were nonsusceptible to azithromycin and roxithromycin in about 60% of cases. Over time, a significant decrease of resistance to azithromycin and doxycycline was detected (p < 0.0001 and 0.0004, respectively), in parallel with an important increase of ciprofloxacin-resistance levels (p < 0.0001). Overall, our results revealed that minocycline and josamycin can be first-line drugs for Mollicutes empirical treatment.

Clonal Dissemination of Candida auris Clinical Isolates in Northern Italy, 2021.

Candida auris is a concerning pathogen in health care due to its ability to spread in medical settings. In this study, we characterized the genome of three C. auris clinical isolates collected in the Emilia-Romagna region of Northeastern Italy from January 2020 to May 2021. Whole-genome sequencing was performed using Illumina iSeq 100 and Oxford Nanopore MinION systems. Genomes were assembled with Flye. Phylogenetic analysis was carried out with RaxML. The ERG11, TAC1b, and FKS1 genes were examined for known substitutions associated with resistance to azoles and caspofungin using Diamond. All three C. auris isolates belonged to clade I (South Asian lineage) and showed high minimum inhibitory concentrations for fluconazole. Two of the three isolates were closely related to the first Italian index case of C. auris occurred in the 2019 and carried similar mutations associated to azole resistance. The third isolate showed a greater phylogenetic distance from these strains and had a different genetic determinant not previously seen in Italy. Our data suggest that two C. auris clinical isolates may have been epidemiologically related to the first outbreak previously observed in Italy, while the remaining isolate may have originated from a different source. Further research is needed to understand C. auris transmission and resistance and to control its spread.

Non-pathogenic Neisseria species of the oropharynx as a reservoir of antimicrobial resistance: a cross-sectional study.

Commensal Neisseria species of the oropharynx represent a significant reservoir of antimicrobial resistance determinants that can be transferred to Neisseria gonorrhoeae. This aspect is particularly crucial in 'men having sex with men' (MSM), a key population in which pharyngeal co-colonization by N. gonorrhoeae and non-pathogenic Neisseria species is frequent and associated with the emergence of antimicrobial resistance. Here, we explored the antimicrobial susceptibility of a large panel of non-pathogenic Neisseria species isolated from the oropharynx of two populations: a group of MSM attending a 'sexually transmitted infection' clinic in Bologna (Italy) (n=108) and a group of males representing a 'general population' (n=119). We collected 246 strains, mainly belonging to N. subflava (60%) and N. flavescens (28%) species. Their antimicrobial susceptibility was evaluated assessing the minimum inhibitory concentrations (MICs) for azithromycin, ciprofloxacin, cefotaxime, and ceftriaxone using E-test strips. Overall, commensal Neisseria spp. showed high rates of resistance to azithromycin (90%; median MICs: 4.0 mg/L), and ciprofloxacin (58%; median MICs: 0.12 mg/L), whereas resistance to cephalosporins was far less common (<15%). Neisseria strains from MSM were found to have significantly higher MICs for azithromycin (p=0.0001) and ciprofloxacin (p<0.0001) compared to those from the general population. However, there was no significant difference in cephalosporin MICs between the two groups. The surveillance of the antimicrobial resistance of non-pathogenic Neisseria spp. could be instrumental in predicting the risk of the spread of multi-drug resistant gonorrhea. This information could be an early predictor of an excessive use of antimicrobials, paving the way to innovative screening and prevention policies.

In Vitro Evaluation of Increasing Avibactam Concentrations on Ceftazidime Activity against Ceftazidime/Avibactam-Susceptible and Resistant KPC-Producing Klebsiella pneumoniae Clinical Isolates.

The novel ß-lactam/ß-lactamase inhibitor combinations (ßL-ßLICs) are one of the last-line resources available against multidrug-resistant (MDR) Gram-negative bacteria. Among ßL-ßLICs, ceftazidime/avibactam (CAZ-AVI) demonstrated strong activity against carbapenem-resistant Enterobacterales (CRE). Avibactam was proven to restore bactericidal activity of ceftazidime, inhibiting both KPC and OXA-48-like ß-lactamases. Despite this, emergence of CAZ-AVI-resistant strains in Enterobacterales has been reported. Herein, we evaluated the in vitro ceftazidime activity in the presence of increasing concentrations of avibactam by the broth microdilution method against CAZ-AVI-susceptible and resistant genome-characterized KPC-producing K. pneumoniae (KPC-Kp) clinical isolates. Strains expressing KPC and co-expressing KPC/OXA-181 carbapenemase were selected on the basis of the different phenotypic traits for novel ßL-ßLICs and cefiderocol. Notably, avibactam at 8 mg/L maintained the MIC of ceftazidime above the clinical breakpoint in 14 out of 15 (93%) KPC-Kp resistant to CAZ-AVI. A high concentration of avibactam (i.e., 64 mg/L) is required to observe a bactericidal activity of ceftazidime against 9 out of 15 (60%) CAZ-AVI-resistant isolates. In vitro evaluation showed that with the increase in the concentration of avibactam, ceftazidime showed high activity against CAZ-AVI-susceptible strains. High concentrations of avibactam in vivo are required for ceftazidime to be active against CAZ-AVI-resistant KPC-Kp.

Clonal dissemination of Klebsiella pneumoniae resistant to cefiderocol, ceftazidime/avibactam, meropenem/vaborbactam and imipenem/relebactam co-producing KPC and OXA-181 carbapenemase.

Objectives: Herein, we describe the epidemiology of carbapenemase-producing Enterobacterales (CPE) before and during the COVID-19 pandemic. Also, we report the emergence of an outbreak of Klebsiella pneumoniae strains co-producing KPC and OXA-181 carbapenemase, resistant to novel ß-lactam/ß-lactamase inhibitors (ßL-ßLICs) and cefiderocol. Methods: CPE were collected during a period of 3 years from 2019 to 2021. Antimicrobial susceptibility testing for novel ßL-ßLICs and cefiderocol was performed by MIC test strips and microdilution with iron-depleted broth. WGS was performed on 10 selected isolates using the Illumina platform, and resistome analysis was carried out by a web-based pipeline. Results: Between January 2019 and December 2021, we collected 1430 carbapenemase producers from 957 patients with infections due to CPE. KPC was the most common carbapenemase, followed by VIM, OXA-48 and NDM. During 2021, we identified 78 K. pneumoniae co-producing KPC and OXA-181 carbapenemases in 60 patients, resistant to meropenem/vaborbactam and imipenem/relebactam. Resistance to ceftazidime/avibactam and cefiderocol was observed respectively in 7 and 8 out of the 10 sequenced K. pneumoniae. Genome analysis showed that all isolates were clonally related, shared a common porin and plasmid content, and carried blaOXA-181 and blaKPC carbapenemases. Specifically, 4 out of 10 isolates carried blaKPC-3, while 6 harboured mutated blaKPC. Of note, KPC producers resistant to ceftazidime/avibactam and harbouring mutated blaKPC exhibited higher MICs of cefiderocol (median MIC 16 mg/L, IQR 16-16) than strains harbouring WT blaKPC-3 (cefiderocol 9 mg/L, IQR 1.5-16). Conclusions: Our results highlight the need for continuous monitoring of CPE to limit widespread MDR pathogens carrying multiple mechanisms conferring resistance to novel antimicrobial molecules.

Real-Life Assessment of the Ability of an Ultraviolet C Lamp (SanificaAria 200, Beghelli) to Inactivate Airborne Microorganisms in a Healthcare Environment.

Airborne-mediated microbial diseases represent one of the major challenges to public health. Ultraviolet C radiation (UVC) is among the different sanitation techniques useful to reduce the risk of infection in healthcare facilities. Previous studies about the germicidal activity of UVC were mainly performed in artificial settings or in vitro models. This study aimed to assess the sanitizing effectiveness of a UVC device (SanificaAria 200, Beghelli, Valsamoggia, Bologna, Italy) in 'real-life' conditions by evaluating its ability to reduce microbial loads in several hospital settings during routine daily activities. The efficacy of the UVC lamp in reducing the bacterial component was evaluated by microbial culture through the collection of air samples in different healthcare settings at different times (30 min-24 h) after turning on the device. To assess the anti-viral activity, air samplings were carried out in a room where a SARS-CoV-2-positive subject was present. The UVC device showed good antibacterial properties against a wide range of microbial species after 6 h of activity. It was effective against possible multi-drug resistant microorganisms (e.g., Pseudomonas spp., Acinetobacter spp.) and spore-forming bacteria (e.g., Bacillus spp.). In addition, the UVC lamp was able to inactivate SARS-CoV-2 in just one hour. Thanks to its effectiveness and safety, SanificaAria 200 could be useful to inactivate airborne pathogens and reduce health risks.

Complete genome sequence and antimicrobial resistance analysis of ESBL-producing Shigella sonnei carrying small cryptic plasmids isolated in northern Italy.

OBJECTIVES: Herein, we sequenced and assembled the genome of a Shigella sonnei isolate carrying several small plasmids using a hybrid approach that combined Oxford Nanopore Technologies and Illumina platforms. METHODS: Whole-genome sequencing was conducted using the Illumina iSeq 100 and Oxford Nanopore MinION systems, and the resulting reads were used for hybrid genome assembly via Unicycler. Coding sequences were annotated using RASTtk, while genes involved in antimicrobial resistance and virulence were identified using AMRFinderPlus. Plasmid nucleotide sequences were aligned to the NCBI non-redundant database using BLAST, and replicons were identified using PlasmidFinder. RESULTS: The genome consisted of 1 chromosome (4 801 657 bp), 3 major plasmids (212 849 bp, 86 884 bp, and 83 425 bp, respectively) and 12 small cryptic plasmids (ranging from 8390 bp to 1822 bp). BLAST analysis revealed that all plasmids were highly similar to previously deposited sequences. Genome annotation predicted 5522 coding regions, including 19 antimicrobial resistance genes and 17 virulence genes. Four of the antimicrobial resistance genes were located in small plasmids, and four of the virulence genes were located in a large virulence plasmid. CONCLUSION: The presence of antimicrobial resistance genes in small cryptic plasmids may represent an overlooked mechanism for the propagation of these genes among bacterial populations. Our work provides new data on these elements that may inform the development of new strategies to control the spread of extended spectrum ß-lactamase-producing bacterial strains.

Comparison of Broth Microdilution, Disk Diffusion and Strip Test Methods for Cefiderocol Antimicrobial Susceptibility Testing on KPC-Producing Klebsiella pneumoniae.

The aim of this study was to compare the reference broth microdilution (BMD) method with the Disk Diffusion (DD) test and strip test against a collection of 75 well-characterized Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae (KPC-Kp) clinical strains to assess cefiderocol (CFD) antimicrobial activity. Whole-genome sequencing was performed on KPC-Kp strains by Illumina iSeq100 platform. The Categorical Agreement (CA) between the BMD method and DD test was 92% (69/75) with a Major Error (ME) of 16.7% (6/36). Additionally, the CA between the BMD method and test strip was 90.7% (68/75) with a Very Major Error (VME) of 17.9% (7/39) and 82.7% (62/75) between the strip test and DD with a ME of 30.2%. KPC-Kp strains showing resistance to CFD were 27 out of 75 (36%) by three methods. Specifically, 51.9% (14/27) of KPC-Kp resistant to CFD harbored blaKPC-3, while 48.1% (13/27) harbored mutated blaKPC-3. Moreover, KPC-Kp strains carrying a mutated blaKPC-3 gene exhibited high MIC values (p value < 0.001) compared to wild-type blaKPC-3. In conclusion, the DD test resulted as a valid alternative to the BMD method to determine the in vitro susceptibility to CFD, while the strip test exhibited major limitations.

Increasing Number of Cases Due to Candida auris in North Italy, July 2019-December 2022.

Candida auris is an emerging fungus that represents a serious health threat globally. In Italy, the first case was detected in July 2019. Then, one case was reported to the Ministry of Health (MoH) on January 2020. Nine months later, a huge number of cases were reported in northern Italy. Overall, 361 cases were detected in 17 healthcare facilities between July 2019 and December 2022 in the Liguria, Piedmont, Emilia-Romagna, and Veneto regions, including 146 (40.4%) deaths. The majority of cases (91.8%) were considered as colonised. Only one had a history of travel abroad. Microbiological data on seven isolates showed that all but one strain (85.7%) were resistant to fluconazole. All the environmental samples tested negative. Weekly screening of contacts was performed by the healthcare facilities. Infection prevention and control (IPC) measures were applied locally. The MoH nominated a National Reference Laboratory to characterise C. auris isolates and store the strains. In 2021, Italy posted two messages through the Epidemic Intelligence Information System (EPIS) to inform on the cases. On February 2022, a rapid risk assessment indicated a high risk for further spread within Italy, but a low risk of spread to other countries.

Characterization of Gardnerella vaginalis isolates: correlations among clades, biofilm formation and cytokine stimulation.

We characterized 61 Gardnerella vaginalis (GV) strains isolated from women with bacterial vaginosis. GV clade 1 was the most commonly found (52.5%), followed by clade 4 (36.1%). All the strains were susceptible to ampicillin and clindamycin, whereas 96.7% and 6.6% of strains showed metronidazole and tetracycline resistance, respectively. Isolates within clade 4 tended to possess the highest ability to form biofilm. Strains resistant to metronidazole and tetracycline were all intermediate or high biofilm producers. All GV clades significantly upregulated the production of pro-inflammatory cytokines by HeLa cells, especially IL-8 and IL-6. Clade 4 induced a significantly higher production of IL-1ß compared to other clades.

Klebsiella pneumoniae carrying multiple alleles of antigen 43-encoding gene of Escherichia coli associated with biofilm formation.

A clinical strain of Klebsiella pneumoniae typed as sequence type 307 carrying three different alleles of the flu gene encoding the Escherichia coli virulence factor antigen 43 associated with biofilm formation was detected and characterized. The flu alleles are located in the chromosome inside putative integrative conjugative elements. The strain displays the phenotypes associated with Ag43, i.e. bi-phasic colony morphology and enhanced biofilm production. Furthermore, the strain produces low amount of capsule known to affect Ag43 function. Analysis of 1431 worldwide deposited genomes revealed that 3.7% Klebsiella pneumoniae carry one or two flu alleles.

Colonization by ceftazidime/avibactam-resistant KPC-producing Klebsiella pneumoniae following therapy in critically ill patients.

OBJECTIVES: Ceftazidime-avibactam (CAZ-AVI)-based treatments have been associated with the emergence of resistance in KPC-producing Klebsiella pneumoniae (KPC-Kp) isolates after antimicrobial exposure. Here, we evaluated the CAZ-AVI resistance development in KPC-Kp isolated from patients treated with CAZ-AVI-based therapy. METHODS: We enrolled adult patients treated with CAZ-AVI-based regimens between January 2020 and January 2021. Carbapenemase-producing isolates collected from clinical samples and rectal swabs were evaluated for CAZ-AVI resistance development after antimicrobial exposure. KPC-Kp developing CAZ-AVI resistance and parental susceptible strains were genomically characterized. Whole genome sequencing was performed by using the Illumina iSeq100 platform and genomes were analyzed for antimicrobial-resistance genes, plasmid and porins sequences. RESULTS: We enrolled 90 patients treated with CAZ-AVI-based therapy and 62.2% (56/90) of them were colonized by KPC-producers before CAZ-AVI-based treatment and 6.6% acquired colonization during therapy. Six (6.6%) patients developed infections because of resistant KPC-Kp after CAZ-AVI exposure and 3 (3.3%) of them developed CAZ-AVI resistance in the rectum. Development of resistance among KPC in the rectum occurred after 32 (IQR, 9-35) days of therapy and after 30 (IQR, 22-40) days in clinical specimens. Genetic analysis demonstrated that the development of CAZ-AVI resistance was associated with mutated blaKPC-3 (blaKPC-31, blaKPC-53, blaKPC-89, and blaKPC-130) and phylogenetic analysis demonstrated a close genomic relationship between KCP-Kp collected from rectum and clinical samples of the same patient. DISCUSSION: Antimicrobial exposure induce a higher incidence of CAZ-AVI resistance development in the blood and respiratory tract than in the rectum (6.7% vs. 3.3%) of CAZ-AVI-treated patients and genome analysis showed that resistance was associated with mutated blaKPC-3 variants.

A descriptive pharmacokinetic/pharmacodynamic analysis of continuous infusion ceftazidime-avibactam in a case series of critically ill renal patients treated for documented carbapenem-resistant Gram-negative bloodstream infections and/or ventilator-associated pneumonia.

OBJECTIVES: To describe the pharmacokinetic/pharmacodynamic (PK/PD) behaviour of continuous infusion (CI) ceftazidime-avibactam and the microbiological outcome in a case series of critically ill renal patients treated for documented carbapenem-resistant Gram-negative (CR-GN) bloodstream infections (BSI) and/or ventilator-associated pneumonia (VAP). METHODS: Critically ill patients with different degrees of renal function who were treated with CI ceftazidime-avibactam for documented CR-GN infections, and who underwent therapeutic drug monitoring from April 2021 to March 2022, were retrospectively assessed. Ceftazidime and avibactam concentrations were determined at steady-state, and the free fraction (fCss) was calculated. The joint PK/PD target of ceftazidime-avibactam was considered as optimal when both Css/MIC ratio for ceftazidime ≥4 (equivalent to 100%fT>4xMIC) and Css/CT ratio for avibactam >1 (equivalent to 100% fT>CT of 4.0 mg/L) were simultaneously achieved (quasi-optimal if only one of the two was achieved, and suboptimal if neither of the two was achieved). The relationship between ceftazidime-avibactam PK/PD targets and microbiological outcome was assessed. RESULTS: Ten patients with documented CR-GN infections (5 BSIs, 4 VAP, 1 BSI+VAP) were retrieved. The joint PK/PD targets of ceftazidime-avibactam were optimal and quasi-optimal in eight and two cases, respectively. Microbiological failure occurred in two patients (one with VAP, one with BSI+VAP), one of whom developed ceftazidime-avibactam resistance. Both underwent renal replacement therapy, and failed despite attaining optimal joint PK/PD target and receiving fosfomycin co-treatment. CONCLUSION: CI administration may enable optimal joint PK/PD targets of ceftazidime-avibactam to be achieved in most critical renal patients with CR-GN infections, and may help to minimize the risk of microbiological failure.