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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.

In this study, we investigated the differences in histamine accumulation between blue scad and chub mackerel and methods of inhibiting histamine-forming bacteria and controlling histamine accumulation in fish. The free histidine contents in blue scad and chub mackerel were 1.45 and 2.75 mg/g, respectively. The histamine-forming bacteria isolated from them were identified as Citrobacter freundii, Citrobacter braakii, and Enterobacter aerogenes using 16S rDNA sequence analysis, the VITEK 2 Compact system, and MALDI-TOF MS. The histamine-producing capacities of C. freundii, C. braakii, and E. aerogenes were 470, 1,057, and 4,213 mg/liter, respectively, after culture at 37°C for 48 h. Among the different antimicrobials and preservatives tested, potassium sorbate and sodium diacetate effectively inhibited the histamine-forming bacteria and their histamine production. After chub mackerel was dipped into 0.5% potassium sorbate or sodium diacetate, its histamine content increased more slowly at room temperature. Therefore, a potassium sorbate or sodium diacetate dipping treatment could effectively control histamine accumulation in fish.

Recent reports describe the ability of select bacterial strains to bind human norovirus, although the specificity of such interactions is unknown. The purpose of this work was to determine if a select group of bacterial species representative of human gut microbiota bind to human norovirus, and if so, to characterize the intensity and location of that binding. The bacteria screened included naturally occurring strains isolated from human stool (Klebsiella spp., Citrobacter spp., Bacillus spp., Enterococcus faecium and Hafnia alvei) and select reference strains (Staphylococcus aureus and Enterobacter cloacae). Binding in PBS was evaluated to three human norovirus strains (GII.4 New Orleans 2009 and Sydney 2012, GI.6) and two surrogate viruses (Tulane virus and Turnip Crinkle Virus (TCV)) using a suspension assay format linked to RT-qPCR for quantification. The impact of different overnight culture media prior to washing on binding efficiency in PBS was also evaluated, and binding was visualized using transmission electron microscopy. All bacteria tested bound the representative human norovirus strains with high efficiency (<1 log10 of input virus remained unbound or <10% unbound and >90% binding efficiency) (p>0.05); there was selective binding for Tulane virus and no binding observed for TCV. Binding efficiency was highest when bacteria were cultured in minimal media (<1 log10 of input virus remained unbound, so >90% bound), but notably decreased when cultured in enriched media (1-3 log10 unbound or 0.01 -<90% bound)) (p<0.05). The norovirus-bacteria binding occurred around the outer cell surfaces and pili structures, without apparent localization. The findings reported here further elucidate and inform the dynamics between human noroviruses and enteric bacteria with implications for norovirus pathogenesis.

Microbial synthesis of selenium nanoparticles (SeNPs) as a fertilizer can promote the development of selenium-rich agricultural products. However, most known selenium-reduction strains exhibit a tolerance to selenite of ≤ 100 mmol/L and possess relatively low reduction efficiency. In this study, three strains capable of tolerating selenite concentrations of > 300 mmol/L were screened from selenium-rich soil in Bama, Guangxi, China. Based on 16 S rRNA gene sequence analysis, the three strains were identified as Citrobacter sp.BM-1, Providencia sp.BM-2, and Brucella sp.BM-3. Notably, Brucella sp.BM-3 represents a novel selenium-reducing bacteria. All three strains reduced SeO 3 2− to SeNPs on the cell membrane and subsequently released these nanoparticles outside the cells, forming spherical SeNPs with a particle size of 210–221 nm. Furthermore, qPCR analysis revealed that the selenium-reduction mechanisms in these strains primarily involve the glutathione pathway, which is catalyzed by nitrate reductase and sulfate reductase. These findings suggest that Citrobacter sp.BM-1, Providencia sp.BM-2, and Brucella sp.BM-3 are promising candidates for the synthesis of SeNPs.

Understanding the antibiotic resistance profile of the emerging pathogen Citrobacter telavivum S24 is important for clinical care, surveillance, and research. C. telavivum S24, a strain that exhibits resistance to both streptomycin and spectinomycin, was isolated from the soil at a broiler chicken farm. The strain was identified by whole-genome sequencing and average nucleotide identity analyses. Annotation of the resistance genes revealed that a novel aminoglycoside resistance gene, designated ant(3″)-Ic , is located on the chromosome of C. telavivum S24. This gene exhibits 52% similarity with the previously functionally characterized resistance gene aadA23 . It distinguishes itself from ant(3″)-Ia and ant(3″)-Ib genes, and represents an independent branch. The ant(3″)-Ic gene is recognized as an inherent resistance gene of C. telavivum within a conserved genetic environment. The product of the ant(3″)-Ic gene is the aminoglycoside nucleotidyltransferase ANT(3″)-Ic, which has a theoretical pI of 5.05 and a molecular mass of 29 kDa. ANT(3”)-Ic inactivates streptomycin and spectinomycin with the K m of 46.13 and 115.90 µM, respectively. The discovery of the novel antibiotic resistance gene ant(3″)-Ic and the functional characterization of ANT(3”)-Ic will facilitate more targeted surveillance and treatment strategies for preventing and controlling zoonotic pathogens of zoonotic diseases.

This study was carried out to investigate the risks of simultaneous exposure to pesticide residues and bacteria contaminants in locally produced fresh vegetables and vegetables in Tanzania. A total of 613 samples were analyzed for pesticide residues, out of which 250 were also analyzed for bacterial contamination. Overall, 47.5% had pesticide residues, 74.2% exceeded Maximum Residue Levels (MRLs). Organophosphorus (95.2%), organochlorines (24.0%), pyrethroids (17.3%), and carbamates (9.2%) residues dominated. MRL values were mostly exceeded in tomatoes, onions, watermelons, cucumbers, Chinese cabbage, and sweet paper. Tetramethrin (0.0329-1.3733 mg/kg), pirimiphos-methyl (0.0003-1.4093 mg/kg), permethrin (0.0009-2.4537 mg/kg), endosulfan (beta) (0.0008-2.3416 mg/kg), carbaryl (0.0215-1.5068 mg/kg), profenofos (0.0176-2.1377 mg/kg), chlorpyrifos (0.0004-1.2549 mg/kg) and dieldrin (0.0011-0.5271 mg/kg) exceeded MRLs. The prevalence of bacteria contamination was high (63.2%). Enterobacter (55.6%) Pseudomonas aeruginosa (32.4%), E. coli (28.2%), Citrobacter (26.8%), Klebsiella oxytoca (14.8%), and Salmonella (7.7%) were isolated. Furthermore, 46.4% tested positive for both pesticide residues and bacterial contaminants. Vegetables from farms (60.7%) contained more dual contaminants than market-based vegetables (41.8%). This may have resulted from excessive pesticide use and unhygienic handling of fresh fruits and vegetables at production level. Binary logistic regression showed that fresh fruits and vegetables with pesticide residues were 2.231 times more likely to have bacteria contaminants (OR: 2.231; 95% CI: 0.501, 8.802). The contamination levels of pesticide residues and bacterial contaminants could be perceived as a serious problem as most fresh fruits and vegetables recorded values of pesticide residues far above the MRLs with pathogenic bacteria isolated in higher proportions. MRLs was higher in most vegetables consumed raw or semi-cooked such as watermelons, carrots, cucumber, tomatoes, onion and sweet paper. There is an urgent need to develop pesticide monitoring and surveillance systems at farmer level, educating farmers and promoting the use of greener pesticides to mitigate the health effects of pesticides and bacterial contaminants.

Background Infections due to Citrobacter species are increasingly observed in hospitalized patients and are often multidrug-resistant. Yet, the magnitude and burden of Citrobacter spp. resistance in the hospital setting have not been reported. We aimed to evaluate the epidemiology of  Citrobacter spp. infections among hospitalized patients, their main resistance patterns and Citrobacter spp. involvement in hospital outbreaks. Methods We conducted a systematic review and meta-analysis of published literature (PROSPERO registration Jan-2023, CRD42023390084). We searched Embase, Medline and grey literature for studies on hospitalized patients diagnosed with  Citrobacter  spp. infections, and nosocomial outbreaks due to Citrobacter spp. published during the years 2000–2022. We included observational, interventional, surveillance studies and outbreak reports. Outcomes of interest were the frequency of Citrobacter spp. infections among hospitalized patients and 3rd generation cephalosporin and/or carbapenem resistance percentages in these infections. We used random-effects models to generate pooled outcome estimates and evaluated risk of bias and quality of reporting of outbreaks. Results We screened 1609 deduplicated publications, assessed 148 full-texts, and included 41 studies (15 observational, 13 surveillance and 13 outbreak studies). Citrobacter spp. urinary tract- and bloodstream infections were most frequently reported, with Citrobacter freundii being the main causative species. Hospital-acquired infection occurred in 85% (838/990) of hospitalized patients with Citrobacter infection. After 2010, an increasing number of patients with Citrobacter spp. infections was reported in observational studies. Pooled frequency estimates for Citrobacter spp. infections could not be generated due to lack of data. The pooled prevalence of ESBL and carbapenemase producers among Citrobacter isolates were 22% (95%CI 4–50%, 7 studies) and 18% (95%CI 0–63%, 4 studies), respectively. An increased frequency of reported Citrobacter outbreaks was observed after 2016, with an infection/colonization ratio of 1:3 and a case-fatality ratio of 7% (6/89 patients). Common outbreak sources were sinks, toilets, contaminated food and injection material. Implemented preventive measures included environmental cleaning, isolation of positive patients and reinforcement of hand hygiene. Only seven out of 13 outbreaks (54%) were definitively controlled. Conclusion This review highlights the clinical importance of endemic and epidemic Citrobacter spp. in healthcare settings. As an emerging, multidrug‑resistant nosocomial pathogen it requires heightened awareness and further dedicated surveillance efforts.

Objectives This work was to investigate the optimal treatments of imipenem (IPM) and meropenem (MEM) against bloodstream infections (BSIs) caused by Citrobacter spp . Methods A total of 230 nonduplicate BSIs Citrobacter spp . were collected from 2014 to 2020 in three hospitals in Zhejiang Province in China. The minimum inhibitory concentrations (MICs) of 17 antibiotics were determined. Monte Carlo simulation (MCS) was used to investigate the cumulative fraction of response (CFR) of 8 regimens of IPM and 10 regimens of MEM. Results C. freundii (Cfr) was the predominant epidemic isolate (83.9%, 193/230). The resistance rates to IPM and MEM showed an increasing trend from 2015 to 2019. Fosfomycin showed excellent activity from 2014 to 2020. The probability of target attainment of IPM and MEM by prolonged 3 h infusion therapy (PIT) was higher than that by traditional 0.5 h (h) infusion therapy (TIT) during the same administration dosage. The CFR of all IPM regimes was above 90%, while MEM with 500 mg q8h was lower than 90%, especially for Cfr. Conclusions Cfr is the most common BSIs. Citrobacter spp . PIT is more adequate to provide activity against BSIs Citrobacter spp ., especially for IPM.

Background. World Health Organization identified some Enterobacteriaceae as superbugs because of their high production and spread of extended-spectrum beta-lactamases (ESBL) and carbapenemases. Moreover, their resistance against commonly prescribed antibiotics left few choices of drugs to treat infection. This study is aimed at determining the magnitude of ESBL and carbapenemase-producing Enterobacteriaceae pathogens and their antimicrobial resistance pattern. Materials and Methods. A hospital-based cross-sectional study was carried out from February to April 2019 in the Northwestern Ethiopia region. A total of 384 patients presumptive for bacterial infections were conveniently enrolled in the study. Specimens were collected and processed following standard bacteriological procedures. Drug susceptibility tests were performed using disk diffusion technique. ESBL and carbapenemase enzymes were tested by double disk diffusion and modified carbapenem inhibition methods, respectively. The data obtained were analyzed using SPSS version 22 software, and descriptive statistics were summarized in tables and graphs. Results. Out of 384 clinical specimens processed 100 (26%) were culture positive for Enterobacteriaceae. The proportion of Enterobacteriaceae infection was relatively higher among in-patients 86 (32.6%) than out-patients 14 (11.7%). Overall, Escherichia coli 35 (9.1%) was the leading isolate followed by Klebsiella pneumoniae 31 (8.1%). Klebsiella pneumoniae 15 (15.6%) was the most frequent isolate from bloodstream infection and is the leading isolate from intensive care unit patients 15 (38.3%). Overall, 44 (44%) of Enterobacteriaceae were extended-spectrum beta-lactamase producers. Among them, Citrobacter spp. was the leading one 4 (80%) followed by Enterobacter cloacae 6 (60%) and K. pneumoniae 18 (58.1%). Furthermore, 6 (6%) of Enterobacteriaceae were carbapenemase-producers, in which 5 (50%) of E. cloacae and 3 (9.7%) of K. pneumoniae had highest percentage. Conclusions. ESBL and carbapenemase-producing isolates of Enterobacteriaceae are alarmingly spreading in the study area. Thus, improving the infection prevention strategy and further screening at the national level is recommended to develop the optimal use of antibiotics.

Background Increasing multidrug-resistance in bacteria resulted in a greater need to find alternative antimicrobial substances that can be used for clinical applications or preservation of food and dairy products. Research on antimicrobial peptides including lipopeptides exhibiting both narrow and broad spectrum inhibition activities is increasing in the recent past. Therefore, the present study was aimed at isolation and characterization of antimicrobial lipopeptide producing bacterial strains from fecal contaminated soil sample. Results The phenotypic and 16S rRNA gene sequence analysis of all isolates identified them as different species of Gram-negative genera Citrobacter and Enterobacter . They exhibited common phenotypic traits like citrate utilization, oxidase negative and facultative anaerobic growth. The HPLC analysis of solvent extracts obtained from cell free fermented broth revealed the presence of multiple antimicrobial lipopeptides. The comprehensive mass spectral analysis (MALDI-TOF MS and GC-MS) of HPLC purified fractions of different isolates revealed that the lipopeptides varied in their molecular weight between (m/z) 607.21 to 1536.16 Da. Isomers of mass ion m/z 984/985 Da was produced by all strains. The 1495 Da lipopeptides produced by strains S-3 and S-11 were fengycin analogues and most active against all strains. While amino acid analysis of lipopeptides suggested most of them had similar composition as in iturins, fengycins, kurstakins and surfactins, differences in their β-hydroxy fatty acid content proposed them to be isoforms of these lipopeptides. Conclusion Although antimicrobial producing strains can be used as biocontrol agents in food preservation, strains with ability to produce multiple antimicrobial lipopeptides have potential applications in biotechnology sectors such as pharmaceutical and cosmetic industry. This is the first report on antibacterial lipopeptides production by strains of Citrobacter and Enterobacter .