BACKGROUND: Multidrug-resistant Gram-negative bacteria, exacerbated by excessive use of antimicrobials and immunosuppressants, are a major health threat.
OBJECTIVE: To study the clinical efficacy and safety of colistin sulfate in the treatment of carbapenem-resistant Gram-negative bacilli-induced pneumonia, and to provide theoretical reference for clinical diagnosis and treatment.
METHODS: This retrospective analysis involved 54 patients with Gram-negative bacilli pneumonia admitted to intensive care unit of The General Hospital of the Northern Theater Command of the People\'s Liberation Army of China from August 2020 to June 2022. After bacteriological culture, the patients\' airway secretions were collected to confirm the presence of Gram-negative bacilli. The patients were divided into the experimental and control groups according to the medication used. The research group consisted of 28 patients who received polymyxin sulfate combined with other drugs through intravenous, nebulization, or intravenous combined with nebulization, with a daily dosage of 1.5-3.0 million units. The control group consisted of 26 patients who received standard dosages of other antibiotics (including sulbactam sodium for injection, cefoperazone sodium sulbactam for injection, tigecycline, meropenem, or vaborbactam).
RESULTS: Of the 28 patients included in the research group, 26 patients showed improvement, treatment was ineffective for two patients, and one patient died, with the treatment efficacy rate of 92.82%. Of the 26 patients in the control group, 18 patients improved, treatment was ineffective for eight patients, and two patients died, with the treatment efficacy rate of 54.9%; significant difference was observed between the two groups (P < 0.05). The levels of white blood cell (WBC), procalcitonin (PCT), and C-reactive protein (CRP) in both groups were significantly lower after treatment than before treatment (P < 0.05), and the levels of WBC, PCT, and CRP in the research group were significantly lower than those in the control group (P < 0.05). Compared with before treatment, there were no significant changes in aspartate aminotransferase, creatinine, and glomerular filtration rate in both groups, while total bilirubin and alanine aminotransferase decreased after treatment (P < 0.05) with no difference between the groups. In patients with good clinical outcomes, the sequential organ failure assessment (SOFA) score was low when treated with inhaled polymyxin sulfate, and specific antibiotic treatment did not improve the outcome. Sepsis and septic shock as well as a low SOFA score were independent factors associated with good clinical outcomes.
CONCLUSIONS: Polymyxin sulfate has a significant effect on the treatment of patients with multiple drug-resistant Gram-negative bacilli pneumonia and other infections in the lungs and is safe and reliable. Moreover, the administration route of low-dose intravenous injection combined with nebulization shows better therapeutic effects and lower adverse reactions, providing new ideas for clinical administration.

Salmonella, which is widely distributed in nature, is an important zoonotic pathogen affecting humans, livestock, and other animals. Salmonella infection not only hinders the development of livestock and poultry-related industries but also poses a great threat to human health. In this study, we collected 1,537 samples including weak chicks, dead embryos, fecal samples and environmental samples from 2020 to 2023 (for a period of 1 to 2 months per year) to keep a long-term monitor the prevalence of Salmonella in an intensive laying hen farm, 105 Salmonella strains were isolated with an isolation rate of 6.83% (105/1,537). It revealed a significant decrease in prevalence rates of Salmonella over time (P < 0.001). Before 2020, the predominant serotype was S. Enteritidis. S. Kentucky was first detected in November 2020 and its proportion was gradually found to exceed that of S. Enteritidis since then. S. Kentucky isolates were distributed in various links of the four regions in the poultry farm. A total of 55 S. Kentucky strains, were assigned to ST198 based on whole genome sequencing. Among them, 54 strains were resistant to 12 to 16 antibiotics, indicating that they were extensively drug-resistant (XDR). Seventeen antimicrobial resistance genes were detected in 55 S. Kentucky isolates. For most of these isolates, antibiotic resistance phenotypes were concordant with their genotypes. All S. Kentucky strains isolated from this farm in 2020 to 2023 showed a high similarity based on their core-genome SNP-based phylogeny. The traceability analysis revealed that S. Kentucky was introduced to the farm through newly purchased flocks. The long-term existence of XDR S. Kentucky ST198 poses a substantial risk because of the multiage management and circulation of workers in this poultry farm. Thus, this study is the first to report extensively drug-resistant S. Kentucky ST198 detected in this intensive poultry farm in China.

Spinal muscular atrophy (SMA) is a neurodegenerative disease that results in progressive and symmetric muscle weakness and atrophy of the proximal limbs and trunk due to degeneration of spinal alpha-motor neurons. Children are classified into types 1-3, from severe to mild, according to the time of onset and motor ability. Children with type 1 are the most severe, are unable to sit independently, and experience a series of respiratory problems, such as hypoventilation, reduced cough, and sputum congestion. Respiratory failure is easily complicated by respiratory infections and is a major cause of death in children with SMA. Most type 1 children die within 2 years of age. Type 1 children with SMA usually require hospitalization for lower respiratory tract infections and invasive ventilator-assisted ventilation in severe cases. These children are frequently infected with drug-resistant bacteria due to repeated hospitalizations and require long hospital stays requiring invasive ventilation. In this paper, we report a case of nebulization combined with intravenous polymyxin B in a child with spinal muscular atrophy with extensively drug-resistant Acinetobacter baumannii pneumonia, hoping to provide a reference for the treatment of children with extensively drug-resistant Acinetobacter baumannii pneumonia.

Extensively drug-resistant (XDR) bacteria are the main caues for causing clinical infectious diseases. Our aim was to distinguish the present molecular epidemiological situation of XDR Klebsiella pneumoniae, Acinetobacter baumannii, and Escherichia coli isolates recovered from local hospitals in Changzhou. Antibiotic susceptibility and phenotypic analysis, multilocus sequence typing and Pulsed Field Gel Electrophoresis were performed to trace these isolates. Resistant phenotype and gene analysis from 29 XDR strains demonstrated that they mainly included TEM, CTX-M-1/2, OXA-48, and KPC products. A. baumannii strains belonged to sequence type (ST) ST224, and carrying the blaCTX-M-2/TEM gene. The quinolone genes aac(6\')-ib-cr and qnrB were carrying only in A. baumannii and E.coli. Three (2.3%) of these strains were found to contain the blaNDM-1 or blaNDM-5 gene. A new genotype of K. pneumoniae was found as ST2639. Epidemic characteristics of the XDR clones showed that antibiotic resistance genes distributed unevenly in different wards in Changzhou\'s local hospitals. With the sequencing of blaNDM carrying isolates, the plasmids often carrying a highly conservative Tn3-relavent mobile genetic element. The especially coupled insert sequence ISKox3 may be a distinctive resistance gene transfer loci. The genotypic diversity variation of XDRs suggested that tracking and isolating the sources of antibiotic resistance especially MBL-encoding genes such as blaNDM-will help manage the risk of infection by these XDRs.

The wide dissemination of plasmids carrying antibiotic resistance determinants among bacteria is a severe threat to global public health. Here, we characterized an extensively drug-resistant (XDR) Klebsiella pneumoniae NTU107224 by whole genome sequencing (WGS) in combination with phenotypic tests. Broth dilution method was used to determine the minimal inhibitory concentrations (MICs) of NTU107224 to 24 antibiotics. The whole genome sequence of NTU107224 was determined by Nanopore/Illumina hybrid genome sequencing. Conjugation assay was performed to determine the transferability of plasmids in NTU107224 to recipient K. pneumoniae 1706. Larvae infection model was used to determine the effect(s) of conjugative plasmid pNTU107224-1 on bacterial virulence. Among the 24 antibiotics tested, XDR K. pneumoniae NTU107224 had low MICs only for amikacin (≤1 μg/mL), polymyxin B (0.25 μg/mL), colistin (0.25 μg/mL), eravacycline (0.25 μg/mL), cefepime/zidebactam (1 μg/mL), omadacycline (4 μg/mL), and tigecycline (0.5 μg/mL). Whole genome sequencing showed that the closed NTU107224 genome comprises a 5,076,795-bp chromosome, a 301,404-bp plasmid named pNTU107224-1, and a 78,479-bp plasmid named pNTU107224-2. IncHI1B plasmid pNTU107224-1 contained three class 1 integrons accumulated various antimicrobial resistance genes (including carbapenemase genes blaVIM-1, blaIMP-23, and truncated blaOXA-256) and the blast results suggested the dissemination of IncHI1B plasmids in China. By day 7 after infection, larvae infected with K. pneumoniae 1706 and transconjugant had 70% and 15% survival rates, respectively. We found that the conjugative plasmid pNTU107224-1 is closely related to IncHI1B plasmids disseminated in China and contributes to the virulence and antibiotic resistance of pathogens.

The infections caused by multidrug- and extensively drug-resistant (MDR, XDR) bacteria, including Gram-positive cocci (GPC, including methicillin-resistant Staphylococcus aureus, MDR-Streptococcus pneumoniae and vancomycin-resistant enterococci) and Gram-negative bacilli (GNB, including carbapenem-resistant [CR] Enterobacterales, CR-Pseudomonas aeruginosa and XDR/CR-Acinetobacter baumannii complex) can be quite challenging for physicians with respect to treatment decisions. Apart from complicated urinary tract and intra-abdominal infections (cUTIs, cIAIs), bloodstream infections and pneumonia, these difficult-to-treat bacteria also cause infections at miscellaneous sites (bones, joints, native/prosthetic valves and skin structures, etc.). Antibiotics like dalbavancin, oritavancin, telavancin and daptomycin are currently approved for the treatment of acute bacterial skin and skin structural infections (ABSSSIs) caused by GPC. Additionally, ceftaroline, linezolid and tigecycline have been formally approved for the treatment of community-acquired pneumonia and ABSSSI. Cefiderocol and meropenem-vaborbactam are currently approved for the treatment of cUTIs caused by XDR-GNB. The spectra of ceftazidime-avibactam and imipenem/cilastatin-relebactam are broader than that of ceftolozane-tazobactam, but these three antibiotics are currently approved for the treatment of hospital-acquired pneumonia, cIAIs and cUTIs caused by MDR-GNB. Clinical investigations of other novel antibiotics (including cefepime-zidebactam, aztreonam-avibactam and sulbactam-durlobactam) for the treatment of various infections are ongoing. Nevertheless, evidence for adequate antibiotic regimens against osteomyelitis, arthritis and infective endocarditis due to several GPC and MDR-GNB is still mostly lacking. A comprehensive review of PubMed publications was undertaken and the formal indications and off-label use of important conventional and novel antibiotics against MDR/XDR-GPC and GNB isolates cultured from miscellaneous sites are presented in this paper.

OBJECTIVE: Extensively drug-resistant (XDR) Acinetobacter baumannii poses a severe threat to public health due to its ability to form biofilms and persister cells, which contributes to critical drug resistance and refractory device-associated infections. A novel strategy to alleviate such an emergency is to identify promising compounds that restore the antimicrobial susceptibility of existing antibiotics against refractory infections.
RESULTS: Here, we found a significant synergy among three combinations of SPR741, clarithromycin and erythromycin with a potent antimicrobial activity against XDR A. baumannii (SPR741/CLA/E at 8/10/10 μg ml-1 for XDR AB1069 and at 10/16/10 μg ml-1 for XDR AB1208, respectively). Moreover, the triple combination therapy exhibits a significant antipersister and antibiofilm effect against XDR strains. Mechanistic studies demonstrate that SPR741 may promote intracellular accumulation of macrolides by permeabilizing the outer membrane as well as disrupting membrane potential and further enhance the quorum sensing inhibition activity of the macrolides against XDR A. baumannii and its biofilms. In addition, the triple combination of SPR741 with clarithromycin and erythromycin was not easy to induce resistance in A. baumannii and had effective antimicrobial activity with low toxicity in vivo.
CONCLUSIONS: Collectively, these results reveal the potential of SPR741 in combination with clarithromycin and erythromycin as a clinical therapy for refractory infections caused by XDR A. baumannii.

Carbapenem-resistant Klebsiella pneumoniae (CRKP) are usually multidrug resistant (MDR) and cause serious therapeutic problems. Colistin is a critical last-resort therapeutic option for MDR bacterial infections. However, increasing colistin use has led to the emergence of extensively drug-resistant (XDR) strains, raising a significant challenge for healthcare. In order to gain insight into the antibiotic resistance mechanisms of CRKP and identify potential drug targets, we compared the molecular characteristics and the proteomes among drug-sensitive (DS), MDR, and XDR K. pneumoniae strains. All drug-resistant isolates belonged to ST11, harboring blaKPC and hypervirulent genes. None of the plasmid-encoded mcr genes were detected in the colistin-resistant XDR strains. Through a tandem mass tag (TMT)-labeled proteomic technique, a total of 3531 proteins were identified in the current study. Compared to the DS strains, there were 247 differentially expressed proteins (DEPs) in the MDR strains and 346 DEPs in the XDR strains, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that a majority of the DEPs were involved in various metabolic pathways, which were beneficial to the evolution of drug resistance in K. pneumoniae. In addition, a total of 67 DEPs were identified between the MDR and XDR strains. KEGG enrichment and protein-protein interaction network analysis showed their participation in cationic antimicrobial peptide resistance and two-component systems. In conclusion, our results highlight the emergence of colistin-resistant and hypervirulent CRKP, which is a noticeable superbug. The DEPs identified in our study are of great significance for the exploration of effective control strategies against infections of CRKP.

Extensively drug-resistant and hypervirulent Klebsiella pneumoniae (XDR-hvKp) is a new problem for patients in Intensive Care Unit (ICU) and can become an even more severe threat if resistant to tigecycline, considered one of the \'last lines of defense\' drugs. This study collected seven non-replicated tigecycline-resistant XDR-hvKp from seven patients and performed genome analysis and epidemiological investigation using whole genome equencing (WGS) and other methods. All strains in this study were identified as ST11-KL64 and showed high resistance to antibiotics such as β-lactams, aminoglycosides, quinolones, and tigecycline, and one strain was also resistant to colistin. All strains were determined to be hvKp by the results of serum resistance assay and Galleria mellonella infection models. All strains had resistance genes bla CTX-M-65,bla KPC-2,bla LAP-2,bla TEM-1B, rmtB, and qnrS1 and virulence factors such as rmpA, rmpA2, and aerobactin (iucABCD, iutA). The expression of the AcrAB-TolC efflux pump was upregulated in all strains, and the expression levels of the gene pmrK was significantly upregulated in colistin-resistant strain DP compared to colistin-sensitive strain WT in this study. In conclusion, we described an outbreak caused by tigecycline-resistant XDR-hvKp in the ICU of a teaching hospital in southwest China. The spread of these superbugs poses a great threat to patients and therefore requires us to closely monitor these XDR-hvKp and develop relevant strategies to combat them.

Acinetobacter baumannii, a strictly aerobic, non-lactose fermented Gram-negative bacteria, is one of the important pathogens of nosocomial infection. Major facilitator superfamily (MFS) transporter membrane proteins are a class of proteins that widely exists in microbial genomes and have been revealed to be related to biofilm formation in a variety of microorganisms. However, as one of the MFS transporter membrane proteins, little is known about the role of BIT33_RS14560 in A. baumannii. To explore the effects of BIT33_RS14560 on biofilm formation of A. baumannii, the biofilm formation abilities of 62 isolates were firstly investigated and compared with their transcript levels of BIT33_RS14560. Then, this specific gene was over-expressed in a standard A. baumannii strain (ATCC 19606) and two isolates of extensively drug-resistant A. baumannii (XDR-Ab). Bacterial virulence was observed using a Galleria mellonella infection model. High-throughput transcriptome sequencing (RNA seq) was performed on ATCC 19606 over-expressed strain and its corresponding empty plasmid control strain. Spearman\'s correlation analysis indicated a significant negative correlation (R = -0.569, p = 0.000) between the △CT levels of BIT33_RS1456 and biofilm grading of A. baumannii isolates. The amount of A. baumannii biofilm was relatively high within 12-48 h. Regardless of standard or clinical strains; the biofilm biomass in the BIT33_RS14560 overexpression group was significantly higher than that in the control group ( p < 0.0001). Kaplan-Meier survival curve analysis showed that the mortality of G. mellonella was significantly higher when infected with the BIT33_RS14560 overexpression strain (χ2 = 8.462, p = 0.004). RNA-Seq showed that the mRNA expression levels of three genes annotated as OprD family outer membrane porin, glycosyltransferase family 39 protein, and glycosyltransferase family 2 protein, which were related to bacterial adhesion, biofilm formation, and virulence, were significantly upregulated when BIT33_RS14560 was over-expressed. Our findings provided new insights in identifying potential drug targets for the inhibition of biofilm formation. We also developed a practical method to construct an over-expressed vector that can stably replicate in XDR-Ab isolates.