Reduce susceptibility to cefiderocol in gram negative bacteria in children: Is hope already lost before it's even arrived?

BACKGROUND

In last years the diffusion of carbapenem resistance in Gram-negative bacteria (CR-GNB) is increasing worldwide, mainly due to the expression of carbapenemases. Cefiderocol has molecular characteristics that ideally confers activity against all CR-GNB, but resistant strains have already been identified. We describe cefiderocol susceptibility profile among multi-drug resistant Gram-negative isolated from pediatric patients.

METHODS

Prospective, single pediatric center study, 1st January 2020-15th June 2023. All GNB carbapenemases producers or phenotypically carbapenem-resistant isolated in the study period were tested for cefiderocol susceptibility. Clinical and microbiological data were collected. A descriptive analysis was performed, comparing the groups of cefiderocol-resistant vs. cefiderocol-susceptible Enterobacterales and non-fermenting Gram-negative bacteria (NF-GNB).

RESULTS

Forty-seven GNB were tested for cefiderocol susceptibility; 38% were cefiderocol-resistant: 16/30 (52%) among Enterobacterales and 2/17 (12%) among NF-GNB. None of the patients were previously exposed to cefiderocol. Looking at Enterobacterales, resistance to ceftazidime/avibactam was higher among cefiderocol-resistant vs. cefiderocol-susceptible strains (62% vs 36%, respectively), as MBL expression (67% vs. 36%, respectively). Too few NF-GNB were cefiderocol-resistance to draw any conclusion. No difference in ICU admission and mortality was identified comparing cefiderocol-resistant vs. susceptible strains. Patients colonized/infected by cefiderocol-resistant strains had been previously hospitalized more frequently.

CONCLUSION

In our cohort cefiderocol resistance was mostly registered among Enterobacterales, and especially among MBL producers' strains (that were alongside resistant to ceftazidime/avibactam). This could be explained by the known possible cross resistance mechanism among ceftazidime/avibactam and cefiderocol. Also, correlation of cefiderocol-resistance with previous hospitalization could be associated with horizontal resistance transmission. Looking at our data, we believe that cefiderocol should be use cautiously, especially empirically and in monotherapy, due to the high resistance rate.

144. Gram Negative Bacteria with Increased Minimal Inhibitory Concentration for Cefiderocol among Pediatric Patients in a Northern Italy Hospital

Background

Cefiderocol is a siderophore cephalosporin active against Gram negative (GN) carbapenem resistant bacteria, approved in Italy in September 2020 for adult patients. In pediatric population off label use is allowed when severe infections from multidrug resistance (MDR) GN bacteria occur. Recently, some authors reported the emergence, among strains of Enterobacterales resistant to ceftazidime avibactam, of cross-resistance with cefiderocol.

The aim of this study is to describe GN strains with increased Minimal Inhibitory Concentration (MIC) for cefiderocol isolated in our hospital.

Methods

This is a retrospective, single-center study conducted in Istituto Giannina Gaslini Pediatric Hospital (Genoa, Italy) from 1^st January 2020 to 31^st April 2022. We collected all strains of MDR GN bacteria whit increased MIC for cefiderocol isolated in our hospital. Cefiderocol susceptibility testing was performed by disk diffusion assay with the disk of 30 μg (Kirby-Bauer method, KB) according to EUCAST’s recommendations and KB breakpoints. We collected demographical data, previous colonization (if note), carbapenemases production, clinical outcomes (infections from MDR; death at 7 and 30 days; ICU admission).

Results

Overall, 10 GN strains with increased MIC for cefiderocol were collected. 9/10 were Enterobacterales (4 Escherichia coli, 2 Enterobacter cloacae complex, 3 Klebsiella pneumoniae), one was Acinetobacter baumannii. 8/10 patients were admitted to other hospital in the six months before admission in our hospital, data about previous colonization were unknown. All MDR isolated produced metallo-β-lactamase [MBL] (5/10 New Delhi metallo-β-lactamase [NDM], 5/10 Verona integron-encoded metallo β-lactamase [VIM]). Four patients developed infection due to MDR (2 urinary tract infections, 1 bloodstream infection, 1 surgical wound), 2/4 patients died during the hospitalization.

Conclusion

Our study confirms that MDR producing MBL carbapenemases may have reduce susceptibility to cefiderocol, even if never exposed to this siderophore cephalosporin.

Due to the possibility of cross resistance with MDR resistant to ceftazidime/avibactam, cefiderocol should be carefully prescribe in empirical treatment of MBL producers strains.

Disclosures

All Authors: No reported disclosures.

1320. Incidence and Outcome of Gram Negative Blood Stream Infections in Pediatric Intensive Care Unit: a Real Life Experience in a Pediatric Hospital in Italy

Background

Antimicrobial resistance (AMR) among Gram Negative (GN) bacteria is a medical and economic concern. In the pediatric setting there is a paucity AMR data due to a lower surveillance in this population.

Aim of this study is to describe incidence and outcomes of GN bloodstream infections (GN-BSI), especially caused by MDR among children admitted to intensive care unit of Istituto Giannina Gaslini Pediatric Hospital in Genoa from January 2017 to December 2021.

Methods

In this retrospective observational single-center study all pediatric patients admitted to ICU with GN-BSI were enrolled.

We collected demographical and clinical data (such as underlying disease, empiric and targeted therapy, presence of devices, prior colonization due to MDR GN, prior treatments and surgery), and outcome and mortality at 7 and 30 days.

Results

Overall, 97 GN-BSI among 85 children admitted to PICU were included during the study period.

Among all patients 40% (34/85) were male, with median age of 3 months (IQR: 1; 11; range: 0-292) and 75% (64/85) were aged < 1 years). Rates of GN BSI according to 1000 admission are showed in figure 1.

The major causative agent was Klebsiella pneumoniae (28/97, 29%), followed by Escherichia coli (18/97, 18%), while 10 episodes (10%) were due to Pseudomonas aeruginosa (figure 2).

A mechanism of resistance was found in 22/97 (23%), with a prevalence of ESBL producers (13/22, 59%), followed by AmpC (4/22, 18%) and KPC (2/22, 1%). 14/97 patients (14%) had a surveillance swab positive by the same bacteria causing BSI. The susceptibility to the 4 more used drugs for 4 more frequent pathogens are showed in figure 3.

In 40% of GN-BSI the empiric therapy was piperacillin/tazobactam, followed by carbapenem in 28/98, 28% of episodes.

Overall, 18 (21%) patients died, half of whom within 7 days of the BSI, including 3/6 of the onco/hematological patients. Figure 1Rates of GN BSI in PICU according to 1000 admissionFigure 2Species distributionFigure 3Susceptibility to the more used drugs for the more frequent pathogens.

Conclusion

This study confirmed the increasing role of GN in BSI and high mortality among children admitted to PICU, especially the youngest, with an increased rate in our Center. Carbapenem resistance isn’t common, but the empirical treatment with piperacillin/tazobactam often it might be useless.

Disclosures

All Authors: No reported disclosures.

Scoliosis with cognitive impairment in a girl with 8q11.21q11.23 microdeletion and SNTG1 disruption

Idiopathic scoliosis (IS) is an abnormality of the vertebral column with a spine curvature of at least 10 degrees. It is the most common spinal deformity in children with a prevalence of 2%-3%, and its aetiology is unknown. Genetic factors are known to play a role and a number of linkage analyses showed associations of various loci. Here we describe a new case of a de novo interstitial deletion 8q11.21q11.2 disrupting SNTG1 gene, identified by array-CGH in a girl with cognitive impairment and a scoliosis that 'appears' like to IS. SNTG1 encodes γ-1 Syntrophin protein that is part of the dystrophin associated protein complex and interacts directly with the C-terminal of dystrophin. Its expression is restricted to neurons and particularly in those areas of the brain that have been suggested to affect postural control. The involvement of SNTG1 gene in IS was already been reported in a family with a breakpoint between exons 10 and 11. Mutational analysis of SNTG1 exons in 152 sporadic IS patients had revealed changes in three patients. In conclusion, our data add a further line of evidence suggesting SNTG1 could represent an interesting candidate for its involvement in scoliosis.

Expanding the phenotype associated with interstitial 6p25.1p24.3 microdeletion: a new case and review of the literature

Interstitial 6p25.1p24.3 microdeletions are rare events and a clear karyotype/phenotype correlation has not yet been determined. In this study, we present the clinical and molecular description of a child with a de novo 6p25.1p24.3 microdeletion, characterized by array-CGH, associated with mild intellectual disability, facial dysmorphisms, hypopigmentation of the skin of the abdomen, heart defects, mild pontine hypoplasia and hypotonia. This deleted region contains 14 OMIM genes (NRN1, F13A1, RREB1, SSR1, RIOK1, DSP, BMP6, TXNDC5, BLOC1S5, EEF1E1, SLC35B3 and HULC). To the best of our knowledge until now only six cases have been reported presenting an interstitial microdeletion, but a unique case carries a deleted region containing the same genes of our patient. We compared clinical features and genetic data with that of the previously reported patient. We also analysed the gene content of the deleted region to investigate the possible role of specific genes in the clinical phenotype of our patient.

17q23.3 de novo microdeletion involving only TANC2 gene: A new case

Neurodevelopmental disorders (NDDs) show a wide range of overlapping clinical features. Intellectual disability (ID), developmental delay (DD), autism spectrum disorder (ASD), attention-deficit hyperactivity disorder (ADHD), language and communication disorders with or without motor abnormalities and/or epilepsy have been reported associated to single or multiple genes but in many cases the genetic basis remains unknown. The increasingly use of array-CGH has significantly improved the yield of diagnosing genomic disorders and led to the identification of several novel microdeletion and microduplication syndromes. TANC2 encodes a synaptic scaffold protein interacting with multiple neuropsychiatric disorder-related postsynaptic density (PSD) proteins in dendrites. Here, we describe a new case of TANC2 gene disruption in a 17q23.3 de novo microdeletion identified by array-CGH. The patient presented craniofacial dysmorphic features, hypotonia, and severe cognitive and motor impairment. In conclusion, our data add a further line of evidence supporting the role of TANC2 in NDDs and will help further researches to elucidate the regulatory mechanism of synaptic function and plasticity related to TANC2 haploinsufficiency.

1p31.1 microdeletion including only NEGR1 gene in two patients

Neuronal growth regulator 1 (NEGR1), a member of the immunoglobulin superfamily cell adhesion molecule subgroup IgLON, has been involved in neuronal growth and connectivity. Genetic variants, in or near the NEGR1 locus, have been associated with obesity and, more recently, with learning difficulties, intellectual disability, and psychiatric disorders. Here, we described the only second report of NEGR1 gene disruption in 1p31.1 microdeletion in two patients. Patient 1 is a 14-year-old female with neurological and psychiatric features present also in her family. Patient 2 is a 5-month-old infant showing global hypotonia as unique neurological features till now. This patient also carries 7p22.1 duplication, of paternal origin, that could be responsible for some malformations present in the child. We hypothesize a role of NEGR1 in producing the phenotype of our patients and compare them with other cases previously reported in the literature and DECIPHER database to better identify a possible genotype-phenotype correlation.

New recurrent chromosome change in pediatric therapy-related myelodysplastic syndrome: unbalanced translocation 1/6 with cryptic duplication of short arm of chromosome 6

The incidence of therapy-related myelodysplastic syndrome (t-MDS) in pediatric patients is increasing in parallel with the more successful management of the primary tumor, but scant information is available on clinical and cytogenetic characteristics. We report here two children affected by t-MDS after chemo/radiotherapy for a primary solid tumor, both with an unbalanced translocation 1/6 in their bone marrow. Characterization by array comparative genomic hybridization of the imbalances showed an almost identical pattern: almost complete trisomy of the long arm of chromosome 1, and a terminal deletion and interstitial duplication of the short arm of chromosome 6. The gain of chromosome 6 short arm encompasses regions already highlighted as possibly relevant for t-MDS in adults, and we suggest that the unbalanced translocation reported here be considered a new recurrent, non-random chromosomal abnormality in pediatric patients with t-MDS.

Trisomy 17 in congenital plexiform (multinodular) cellular schwannoma

Plexiform (multinodular) cellular schwannomas are rare tumors, not associated with neurofibromatosis type 1, that occur more often in children and can be congenital. Their biology is benign and is characterized by the tendency to recur locally without being metastatic. Cytogenetic studies in adult cases of schwannoma indicate a complete or partial loss of chromosome 22 as the most common abnormality. Only two cytogenetic studies describe cases in children, one of which concerned a congenital cellular plexiform schwannoma. Here, we report the cytogenetic analysis of a second case in an 8-month-old boy with recurrence of trisomy 17.