Tigecycline salvage therapy for critically ill children with multidrug-resistant/extensively drug-resistant infections after surgery

Emergence of ceftazidime-avibactam resistance in blaKPC-33-harbouring ST11 Klebsiella pneumoniae in a paediatric patient

Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses immense threats to the health of infected patients worldwide, especially children. This study reports the infection caused by CRKP in a paediatric intensive care unit (PICU) child and its drug-resistant mutation during the treatment. Twelve Klebsiella pneumoniae carbapenemase (KPC)-producing K. pneumoniae strains were isolated from the child. Broth microdilution method, plasmid transformation assay, and whole genome sequencing (WGS) were performed to investigate the antimicrobial susceptibility, resistance mechanisms, and genetic structural features of CRKPs. The results showed that 12 strains were highly resistant to most available antimicrobial agents. Among them, K. pneumoniae FD11 and K. pneumoniae FD12 were resistant to ceftazidime-avibactam (CZA, MIC >64 mg/L) and restored the carbapenem susceptibility (Imipenem, MIC =0.25 mg/L; Meropenem, MIC =2 mg/L). The patient improved after treatment with CZA in combination with aztreonam. Plasmid transformation assay demonstrated that the blaKPC-33-positive transformant increased MICs of CZA by at least 33-fold and 8-fold compared with the recipient Escherichia coli DH5α and blaKPC-2-positive transformants. WGS analysis revealed that all strains belonged to the ST11-KL64 type and showed highly homologous (3-26 single nucleotide polymorphisms [SNPs]). A single base mutation (G532T) of blaKPC-2 resulted in a tyrosine to aspartic acid substitution at Ambler amino acid position 179 (D179Y), which conferred CZA resistance in K. pneumoniae. This is the first report of a drug-resistant mutation evolving into blaKPC-33 during the treatment of blaKPC-2-positive CRKP in paediatric-infected patients. It advises clinicians that routine sequential antimicrobial susceptibility testing and KPC genotyping are critical during CZA therapy in children infected with CRKP.

Comparative Genomic Analysis Reveals the Emergence of ST-231 and ST-395 Klebsiella pneumoniae Strains Associated with the High Transmissibility of blaKPC Plasmids

Conjugative transposons in Gram-negative bacteria have a significant role in the dissemination of antibiotic-resistance-conferring genes between bacteria. This study aims to genomically characterize plasmids and conjugative transposons carrying integrons in clinical isolates of Klebsiella pneumoniae. The genetic composition of conjugative transposons and phenotypic assessment of 50 multidrug-resistant K. pneumoniae isolates from a tertiary-care hospital (SQUH), Muscat, Oman, were investigated. Horizontal transferability was investigated by filter mating conjugation experiments. Whole-genome sequencing (WGS) was performed to determine the sequence type (ST), acquired resistome, and plasmidome of integron-carrying strains. Class 1 integrons were detected in 96% of isolates and, among integron-positive isolates, 18 stains contained variable regions. Horizontal transferability by conjugation confirmed the successful transfer of integrons between cells and WGS confirmed their presence in conjugative plasmids. Dihydrofolate reductase (dfrA14) was the most prevalent (34.8%) gene cassette in class 1 integrons. MLST analysis detected predominantly ST-231 and ST-395. BlaOXA-232 and blaCTX-M-15 were the most frequently detected carbapenemases and beta-lactamases in the sequenced isolates. This study highlighted the high transmissibility of MDR-conferring conjugative plasmids in clinical isolates of K. pneumoniae. Therefore, the wise use of antibiotics and the adherence to effective infection control measures are necessary to limit the further dissemination of multidrug-resistant bacteria.

Tigecycline-Induced Tooth Discoloration in Children Younger than Eight Years

Tetracycline may cause tooth discoloration when used in young children during tooth development. Whether tigecycline, a tetracycline derivative, has either a similar adverse event or not remains unclear. We assessed the discoloration of the permanent teeth of patients <8 years old after tigecycline exposure. These patients were identified through a retrospective chart review in a Chinese children's hospital. Those who had at least one erupted permanent tooth after tigecycline exposure were interviewed, examined, and photographed by an experienced pediatric dentist and independently assessed by another senior dentist to detect tetracycline-like tooth discoloration. We identified 101 patients who were exposed to tigecycline, 12 of whom were included. The mean daily dose of tigecycline was 2.3 mg/kg of body weight (standard deviation, 0.6), and the median duration was 12.5 days (interquartile range [IQR], 8.0 to 19.3). The median age of exposure was 5.2 years (IQR, 4.5 to 7.4), and the median age of dental examination was 9.1 years (IQR, 9.0 to 10.3). Two patients (16.7%) developed yellow discoloration: a girl having yellow discoloration with white-to-yellow opacities in the upper lateral incisors and lower incisors and a boy with a suspicious buccal yellow discoloration and enamel dysplasia in the second molars. The incidence and extent of tigecycline-associated dental adverse events remain unclear due to the small sample size and inadequate follow-up period.

Dose optimisation based on pharmacokinetic/pharmacodynamic target of tigecycline

Tigecycline, a new first-in-class glycylcycline antibiotic, has shown promising efficacy against a broad range of micro-organisms. It is widely prescribed for various infections, with most prescriptions being considered for off-label use. However, only a few years after its approval by the US Food and Drug Administration (FDA), tigecycline is suspected of increasing all-cause mortality. Some clinicians have suggested such unfavourable outcomes correlate with inadequate drug exposure at the infection site. The pharmacokinetic/pharmacodynamic (PK/PD) profile of a drug plays an important role in predicting its antibiotic effect, which for tigecycline is determined as the ratio of area under the concentration-time curve (AUC) to minimum inhibitory concentration (MIC). In this study, PK/PD targets based on infection sites, bacterial isolates and patient populations are discussed. Generally, a higher dosage of tigecycline for the treatment of serious infections has been recommended in previous reports. However, the latest finding of tigecycline's atypical protein binding property requires consideration when recommending further use. In addition, combination therapy with other antibiotics provides another option by potentially lowering the MICs of multidrug-resistant bacteria.

Tigecycline antibacterial activity, clinical effectiveness, and mechanisms and epidemiology of resistance: narrative review

Tigecycline is unique glycylcycline class of semisynthetic antimicrobial agents developed for the treatment of polymicrobial infections caused by multidrug-resistant Gram-positive and Gram-negative pathogens. Tigecycline evades the main tetracycline resistance genetic mechanisms, such as tetracycline-specific efflux pump acquisition and ribosomal protection, via the addition of a glycyclamide moiety to the 9-position of minocycline. The use of the parenteral form of tigecycline is approved for complicated skin and skin structure infections (excluding diabetes foot infection), complicated intra-abdominal infections, and community-acquired bacterial pneumonia in adults. New evidence also suggests the effectiveness of tigecycline for the treatment of severe Clostridioides difficile infections. Tigecycline showed in vitro susceptibility to Coxiella spp., Rickettsia spp., and multidrug-resistant Neisseria gonnorrhoeae strains which indicate the possible use of tigecycline in the treatment of infections caused by these pathogens. Except for intrinsic, or often reported resistance in some Gram-negatives, tigecycline is effective against a wide range of multidrug-resistant nosocomial pathogens. Herein, we summarize the currently available data on tigecycline pharmacokinetics and pharmacodynamics, its mechanism of action, the epidemiology of tigecycline resistance, and its clinical effectiveness.

Tigecycline Therapy for Multi-drug-Resistant Pseudomonas aeruginosa Sepsis Associated with Multi-organ Failure in an Infant with Persistent Arterial Duct. Case Report

Sepsis is the leading cause of death in infants and children worldwide. The growing drug resistance in nosocomial gram-negative bacteria has resulted in treatment challenges. One of the most common multi-drug-resistant bacteria is Pseudomonas aeruginosa. Resistance to antibiotics used in Pseudomonas aeruginosa infections limits the therapeutic options. We present a tigecycline administration in a 5-month-old infant with patent arterial duct, heart failure, and respiratory failure due to respiratory syncytial virus bronchiolitis with subsequent respiratory distress syndrome and severe sepsis caused by multi-drug-resistant Pseudomonas aeruginosa. Despite combined antibiotic therapy with meropenem, amikacin, and colistin, inflammatory markers increased. Because of life-threatening condition, tigecycline was added to the therapy and was administered intravenously twice daily. Within 48 h, inflammatory markers started to decrease and tigecycline therapy continued for 13 days without adverse effects. Tigecycline used in combination with other antibiotics might be a valuable therapeutic approach in the management of multi-drug-resistant bacteria infections in pediatric patients when conventional antibiotics have failed. Further studies are needed to evaluate the efficacy and safety of tigecycline administration in critically ill pediatric patients.