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Background Symbiotic bacteria affect insect physiology and ecology. They may also mediate insecticide resistance within their hosts and thereby impact pest and vector control practices. Here, we document a novel mechanism of insecticide resistance in which a gut symbiont of the tephritid pest fruit fly Bactrocera dorsalis enhances resistance to the organophosphate insecticide trichlorphon. Results We demonstrated that the gut symbiont Citrobacter sp. (CF-BD) plays a key role in the degradation of trichlorphon. Based on a comparative genomics analysis with other Citrobacter species, phosphatase hydrolase genes were identified in CF-BD. These CF-BD genes had higher expression when trichlorphon was present. Bactrocera dorsalis inoculated with isolated CF-BD obtained higher trichlorphon resistance, while antibiotic-treated flies were less resistant confirming the key role of CF-BD in insecticide resistance. Conclusions Our findings suggest that symbiont-mediated insecticide resistance can readily develop in B. dorsalis and may represent a more widely relevant insecticide resistance mechanism than previously recognized.

To characterize the microbiological, molecular and epidemiological data of an outbreak of carbapenem-resistant Enterobacteriaceae (CRE) in a tertiary-care hospital in Mexico. From September 2014 to July 2015, all CRE clinical isolates recovered during an outbreak in the Hospital Civil \"Fray Antonio Alcalde\" in Jalisco, Mexico were screened for antimicrobial susceptibility, carbapenemase production, carbapenemase-encoding genes, and plasmid profiles. Horizontal transfer of imipenem resistance; and clonal diversity by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST); as well as biofilm production and the presence of 14 virulence genes were analyzed in selected isolates. Fifty-two carbapenem-resistant isolates corresponding to 5 species were detected, i.e., Klebsiella pneumoniae (n = 46), Enterobacter cloacae (n = 3), Escherichia coli (n = 1), Providencia rettgeri (n = 1) and Citrobacter freundii (n = 1) with carbapenemase encoding genes blaNDM-1 (n = 48), blaVIM (n = 3), blaIMP (n = 1) and blaKPC (n = 1) detected in these isolates. The blaNDM-1 gene was detected in plasmids from 130- to 170-kb in K. pneumoniae (n = 46); E. cloacae (n = 3), E. coli (n = 1) and P. rettgeri (n = 1). The transfer of plasmids harboring the blaNDM-1 gene was obtained in eight transconjugants. One plasmid restriction pattern was detected, with the blaNDM-1 identified in different restriction fragments. Predominant clone A of K. pneumoniae isolates archived 28/46 (60%) isolates and belongs to ST392. Besides, ST307, ST309, ST846, ST2399, and ST2400 were detected for K. pneumoniae; as well as E. cloacae ST182 and E. coli ST10. The fimA and uge genes were more likely to be identified in K. pneumoniae carbapenem-susceptible isolates (p = <0.001) and biofilm production was more liable to be observed in carbapenem-resistant isolates (p = <0.05). Four Enterobacteriaceae species harboring the blaNDM-1 gene were detected in a nosocomial outbreak in Mexico; horizontal transfer and strain transmission were demonstrated for the blaNDM-1 gene. Given the variation in the size of the plasmid harboring blaNDM-1, complex rearrangements must also be occurring.

Extended-spectrum beta-lactamase (ESBL) and ampicillin resistance gene type C (ampC) in foodborne Citrobacter freundii (C. freundii) pose a severe public health risk, especially when they combine with other critical resistance genes to produce a reservoir of resistance. Therefore, the current study aimed to estimate the prevalence, phenotypic, and genotypic profiling of antimicrobial resistance in C. freundii isolates obtained from diseased broiler chickens and native Egyptian buffaloes in Kafr El-Sheikh and Dakahlia governorates, Egypt. Also, the investigation of the antibacterial activity of chitosan (CS) 1%, 2%, and chitosan nanoparticles (CSNPs), including the estimation of minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) and their combinations with ciprofloxacin (CIP), were evaluated. C. freundii was detected in 57.58% (19/33) of broiler chickens and 52.63% (20/38) of buffalo. Surprisingly, 26.32% (5/19) and 20% (4/20) of chicken and buffalo samples, respectively were multidrug-resistant (MDR), 42.11% (8/19) and 15% (3/20) were extensively drug-resistant (XDR), and 31.58% (6/19) and 65% (13/20) were pan drug-like-resistant (PDR). High frequencies of resistance genes were observed, including int1, dfrA1, sul2, aadA1, qnrA, and bla (≥ 80%), while other genes such as ermB, bla , bla , tet(M), mcr-1, bla and catA1 were detected at variable rates. Alarmingly, all ESBL/AmpC-producing isolates co-harbored multiple critical resistance genes. CSNPs showed markedly lower MIC and MBC values compared with 1% and 2% CS, indicating significantly stronger bactericidal activity. The concerning prevalence of PDR like-C. freundii in food animals is brought to light by our results, which also provide credence to the use of 2% CS-CIP and CSNPs-CIP combinations as potential substitute treatments for resistant infections.

Objectives Despite regularly being found in blood cultures, there are few studies of bloodstream infection (BSI) with Citrobacter. In this population-based study, the aim was to explore patient characteristics, outcome, and incidence in a publicly funded single payer setting. Methods Patients with growth of Citrobacter in blood culture were identified through the clinical microbiology laboratory in Lund, Sweden, for the year 2013–2023. This laboratory serves the whole Skåne region, with a population of 1.4 million. Medical records were retrospectively reviewed. Results 554 episodes of Citrobacter BSI were identified, with septic shock seen in 25 (4%) episodes and with 38 (7%) episodes resulting in intensive care. The 90-day mortality was 18% and the median age of the patients was 77 years. Resistance to cephalosporins was below 10%, and carbapenem resistance was not found in any isolates. A majority of episodes were healthcare associated or nosocomial, and almost half of BSI cases originated from the urinary tract. The association with the urinary tract was stronger for C. koseri BSI than for C. freundii complex BSI, which was more often polymicrobial and associated with abdominal surgery. Conclusion Citrobacter BSI was primarily found in elderly patients, either hospitalized or in close contact with healthcare in other ways. C. koseri BSI was to a greater extent associated with urinary tract focus compared to patients with BSI due to C. freundii complex, which was associated with abdominal source of infection and polymicrobial BSI.

Background: Various dosing strategies for cefepime have been developed in an effort to maximize pharmacodynamic exposure of this agent against gram-negative infections. An assessment of cefepime dosing strategies is warranted given recent reports of poorer treatment outcomes associated with cefepime compared with other antibiotics, particularly in patients infected with gram-negative organisms with elevated MICs. Objectives: The aims of this study were to compare the efficacy of cefepime IV at a dose of 1 g q8h (adjusted based on renal function) with those of other appropriate antimicrobials in the treatment of gramnegative pulmonary and bloodstream infections and to identify risk factors for treatment failure. Methods: This single-center, open-label, prospective, observational study was conducted at a tertiary care center (Barnes-Jewish Hospital, St. Louis, Missouri). Isolates from infections in adult patients with bacteremia or pulmonary infection caused by Pseudomonas aeruginosa, Enterobacter aerogenes, Enterobacter cloacae, or Citrobacter freundii were assessed in a noninterventional manner. Infections were identified using an electronic notification system. Patients receiving appropriate monotherapy against the studied isolate within 24 hours of culture attainment were stratified into 1 of 3 cohorts according to treatment outcome, as follows: treatment success (resolution of initial fever or elevated white blood cell count to normal values plus the presence of repeat negative cultures from the initial site or below the quantitative definition for infection), improvement (treatment success without repeat negative cultures), or treatment failure (persistent or repeat positive cultures for the original organism at the infected site despite appropriate and adequate antimicrobial therapy, lack of resolution in fever or leukocytosis, switch to an alternative antibiotic, or the addition of another antibiotic with gram-negative coverage after ≥3 days of the initial regimen, relapse of infection within 14 days, or mortality attributable to the index infection). Multivariate regression analysis was used to examine risk factors associated with treatment failure. Results: Data from 120 patients (56.7% male; mean age, 62.2 years) were analyzed. Treatment failure occurred in 48.6% (36/74) of patients who received cefepime versus 32.6% (15/46) of those who received other antibiotics; this difference was not statistically significant. The proportion of patients with markers of increased severity of illness (intensive care unit [ P = 0.005] and mechanical ventilation [ P = 0.002]) was significantly greater in the cefepime group compared with the group that received other antibiotics. Multivariate logistic regression identified infection with Pseudomonas aeruginosa (adjusted odds ratio [AOR], 1.40 [95% CI, 1.01–2.00]) and mechanical ventilation (AOR, 7.08 [95% CI, 1.80–31.3]) as being associated with treatment failure in patients who received cefepime. Mechanical ventilation (AOR, 3.97 [95% CI, 1.47–11.1]) and neutropenia (AOR, 5.26 [95% CI, 1.28–20.0]) were independent predictors of treatment failure among all patients studied. Conclusions: Based on these results in this small cohort, the efficacy of this cefepime dosing strategy (1 g q8h) appeared to be similar to that of other antimicrobials.

is a frequent cause of nosocomial infections and a known cause of diarrheal infections, and has increasingly become multidrug resistant (MDR). In this study, we aimed to determine the genetic diversity, the antimicrobial resistance profiles and virulence properties of from diarrheal patients and healthy individuals. 82 isolates were obtained from human diarrheal outpatients and healthy individuals. Multilocus Sequence Typing (MLST) of seven housekeeping genes was performed. Antimicrobial susceptibility testing was carried out using the disk diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) recommendations. Adhesion and cytotoxicity to HEp-2 cells were assessed. PCR and sequencing were used to identify , , , and genes. The 82 isolates were divided into 76 sequence types (STs) with 65 STs being novel, displaying high genetic diversity. Phylogenetic analysis divided the 82 isolates into 5 clusters. All 82 isolates were sensitive to imipenem (IPM), but resistant to one or more other 16 antibiotics tested. Twenty-six isolates (31.7%) were multidrug resistant to three or more antibiotic classes out of the 10 distinct antibiotic classes tested. Five MDR isolates, all of which were isolated from 2014, harbored one or more of the resistance genes, , , , and . All 11 -carrying isolates belonged to cluster 1, and one isolate carried a new gene ( ). Six isolates showed strong cytotoxicity to HEp-2 cells, one of which was multidrug resistant. isolates from human diarrheal outpatients and healthy individuals were diverse with variation in sequence types, antibiotic resistance profiles and virulence properties.

Mercury (Hg) is one of the most potent toxic heavy metals that distresses livestock, humans, and ecological health. Owing to uncontrolled exposure to untreated tannery industrial effluents, metals such as Hg are increasing in nature and are, therefore, becoming a global concern. As a result, understanding the thriving microflora in that severe condition and their characteristics becomes immensely important. During the course of this study, two Hg-resistant bacteria were isolated from tannery wastewater effluents from leather factories in Kolkata, India, which were able to tolerate 2.211 × 10− 3 M (600 µg/ml) Hg. 16 S rDNA analysis revealed strong sequence homology with Citrobacter freundii, were named as BNC22A and BNC22C for this study. In addition they showed high tolerance to nickel (Ni) and Chromium (Cr) at 6.31 × 10− 3 M (1500 µg/ml) and 6.792 × 10− 3 M (2000 µg/ml) respectively. However, both the isolates were sensitive to arsenic (As) and cadmium (Cd). Furthermore, their antibiotic sensitivity profiles reveal a concerning trend towards resistance to multiple drugs. Overuse and misuse of antibiotics in healthcare systems and agriculture has been identified as two of the main reasons for the decline in efficacy of antibiotics. Though their ability to produce lipase makes them industrially potent organisms, their competence to resist several antibiotics and metals that are toxic makes this study immensely relevant. In addition, their ability to negate heavy metal toxicity makes them potential candidates for bioremediation. Finally, the green mung bean seed germination test showed a significant favourable effect of BNC22A and BNC22C against Hg-stimulated toxicity.

An electrogenic bacterium, named Citrobacter freundii Z7, was isolated from the anodic biofilm of microbial fuel cell (MFC) inoculated with aerobic sewage sludge. Cyclic voltammetry (CV) analysis exhibited that the strain Z7 had relatively high electrochemical activity. When the strain Z7 was inoculated into MFC, the maximum power density can reach 204.5 mW/m²using citrate as electron donor. Series of substrates including glucose, glycerol, lactose, sucrose, and rhammose could be utilized to generate power. CV tests and the addition of anode solution as well as AQDS experiments indicated that the strain Z7 might transfer electrons indirectly via secreted mediators.

Despite the successful application of LNA/2'OMe-FISH procedures for bacteria detection, there is a lack of knowledge on the properties that affect hybridization. Such information is crucial for the rational design of protocols. Hence, this work aimed to evaluate the effect of three essential factors on the LNA/2'OMe hybridization step-hybridization temperature, NaCl concentration and type and concentration of denaturant (formamide, ethylene carbonate and urea). This optimization was performed for 3 Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa and Citrobacter freundii) and 2 Gram-positive bacteria (Enterococcus faecalis and Staphylococcus epidermidis), employing the response surface methodology and a Eubacteria probe. In general, it was observed that a high NaCl concentration is beneficial (from 2 M to 5 M), regardless of the denaturant used. Urea, formamide and ethylene carbonate are suitable denaturants for LNA/2'OMe-FISH applications; but urea provides higher fluorescence intensities among the different bacteria, especially for gram-positive bacteria and for P. aeruginosa. However, a unique optimal protocol was not found for all tested bacteria. Despite this, the results indicate that a hybridization solution with 2 M of urea and 4 M of NaCl would be a proper starting point. Furthermore, a hybridization temperature around 62°C, for 14 bp probes with LNA monomers at every third position of 2'OMe and 64% of GC content, should be use in initial optimization of new LNA/2'OMe-FISH protocols.

Citrobacter freundii is an infrequent but established cause of diarrhea in humans. However, little is known of its genetic diversity and potential for virulence. We analyzed 26 isolates, including 12 from human diarrheal patients, 2 from human fecal samples of unknown diarrheal status, and 12 from animals, insects, and other sources. Pulsed field gel electrophoresis using XbaI allowed us to divide the 26 isolates into 20 pulse types, while multi-locus sequence typing using 7 housekeeping genes allowed us to divide the 26 isolates into 6 sequence types (STs) with the majority belonging to 4 STs. We analyzed adhesion and cytotoxicity to HEp-2 cells in these 26 strains. All were found to adhere to HEp-2 cells. One strain, CF74, which had been isolated from a goat, showed the strongest aggregative adhesion pattern. Lactate dehydrogenase (LDH) released from HEp-2 cells was evaluated as a measure of cytotoxicity, averaging 7.46%. Strain CF74 induced the highest level of LDH, 24.3%, and caused >50% cell rounding, detachment, and death. We named strain CF74 \"cytotoxic and aggregative C. freundii.\" Genome sequencing of CF74 revealed that it had acquired 7 genomic islands, including 2 fimbriae islands and a type VI secretion system island, all of which are potential virulence factors. Our results show that aggregative adherence and cytotoxicity play an important role in the pathogenesis of C. freundii.