Citrobacter peritoneal dialysis peritonitis: rare occurrence with poor outcomes

Epidemiology of Citrobacter spp. infections among hospitalized patients: a systematic review and meta-analysis

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.

Genomic analysis of Citrobacter from Australian wastewater and silver gulls reveals novel sequence types carrying critically important antibiotic resistance genes

Antimicrobial resistance (AMR) is a major public health concern, and environmental bacteria have been recognized as important reservoirs of antimicrobial resistance genes (ARGs). Citrobacter, a common environmental bacterium and opportunistic pathogen in humans and other animals, has been largely understudied in terms of its diversity and AMR potential. Whole-genome (short-read) sequencing on a total of 77 Citrobacter isolates obtained from Australian silver gull (Chroicocephalus novaehollandiae) (n = 17) and influent wastewater samples (n = 60) was performed, revealing a diverse Citrobacter population, with seven different species and 33 sequence types, 17 of which were novel. From silver gull using non-selective media we isolated a broader range of species with little to no mobilised ARG carriage. Wastewater isolates (selected using Carbapenem- Resistant Enterobacterales (CRE) selective media) carried a heavy burden of ARGs (up to 21 ARGs, conferring resistance to nine classes of antibiotics), with several novel multidrug-resistant (MDR) lineages identified, including C. braakii ST1110, which carried ARGs conferring resistance to eight to nine classes of antibiotics, and C. freundii ST1105, which carried two carbapenemase genes, blaIMP-4 in class 1 integron structure, and blaKPC-2. Additionally, we identified an MDR C. portucalensis isolate carrying blaNDM-1, blaSHV-12, and mcr-9. We identified IncC, IncM2, and IncP6 plasmids as the likely vectors for many of the critically important mobilised ARGs. Phylogenetic analyses were performed to assess any epidemiological linkages between isolation sources, demonstrating low relatedness across sources beyond the ST level. However, these analyses did reveal some closer relationships between strains from disparate wastewater sources despite their collection some 13,000 km apart. These findings support the need for future surveillance of Citrobacter populations in wastewater and wildlife populations to monitor for potential opportunistic human pathogens.

Butyricimonas virosa Peritonitis in Peritoneal Dialysis Patient: A Case Report and Review

Butyricimonas virosa is a Gram-negative bacillus, which was first discovered in rat faeces in 2009. To date, only seven human infections have been reported in literature. To our knowledge, this is the first reported case of peritoneal dialysis (PD)-related peritonitis due to B. virosa. A 65-year-old Chinese man presented to the hospital with complaints of dizziness and vomiting. On admission, the drained peritoneal dialysate was cloudy. He was empirically treated as a case of PD-related peritonitis with intraperitoneal (IP) cefazolin, ceftazidime, and gentamicin. B. virosa was isolated from peritoneal fluid sample and the antibiotics were changed to IP imipenem and amikacin. Three weeks after completion of the antibiotics, the patient presented again with cloudy peritoneal dialysate and blood stained diarrhoea. IP imipenem and amikacin were recommenced. Multiple peritoneal dialysate samples were sent to the microbiology laboratory, but this time no microorganism was isolated. Colonoscopy examination revealed the presence of extensive rectosigmoidal ulcerations. IP imipenem was replaced with IP piperacillin-tazobactam when the patient developed imipenem-associated neurotoxicity at Day 9 of treatment. The patient recovered fully after completing 3 weeks of IP piperacillin-tazobactam and 2 weeks of IP amikacin. This is the first reported case of PD-related peritonitis due to B. virosa. Susceptibility data for B. virosa are scarce, but a 3-week course of IP piperacillin-tazobactam, imipenem, or meropenem could be potentially useful in treating PD-related peritonitis caused by this organism.

Exploration of the correlation between intestinal flora and Escherichia coli peritoneal dialysis-related peritonitis

BACKGROUND

Escherichia coli peritonitis (EP) is a serious complication of peritoneal dialysis (PD). Gut microbiota alterations occur in end-stage renal disease (ESRD) patients. The relationship between the gut microbiota and PD-related peritonitis is still poorly understood. It is unclear whether the intestinal flora is involved in the pathogenesis of EP.

METHODS

We collected fecal samples from EP patients and normal group (NG) PD patients. 16S rRNA sequencing was used to analyze the gut microbiota of EP and NG patients. The demographic data and clinical indicators of all patients were collected.

RESULTS

Six EP patients and 28 NG patients were recruited for this study. The analysis of fecal community diversity with 16S rDNA sequencing showed an obvious change in the microbial structure of EP patients, where Bacteroidetes and Synergistetes were upregulated at different levels, while Bacilli and Lactobacillus were downregulated at different levels compared to the NG group. Additionally, decreased gene function associated with metabolic pathways was observed in EP patients.

CONCLUSIONS

The altered composition of the gut microbiota in EP patients provided deeper insights into the pathogenesis of EP, and these biomarkers might be established as potential therapeutic targets that deserve further exploration.

Antimicrobial Resistance and Molecular Characterization of Citrobacter spp. Causing Extraintestinal Infections

Objectives

This prospective study was carried out to investigate molecular characteristics and antimicrobial susceptibility patterns of Citrobacter spp. from extraintestinal infections.

Methods

Forty-six clinical Citrobacter spp. isolates were isolated from hospital patients with extraintestinal infections and analyzed by multilocus sequence typing (MLST) using seven housekeeping genes. Antimicrobial susceptibility testing was performed by disk diffusion method according to the Clinical and Laboratory Standards Institute (CLSI) recommendations. Adhesion and cytotoxicity to HEp-2 cells were assessed.

Results

The 46 clinical Citrobacter spp. isolates were typed into 38 sequence types (STs), 9 of which belonged to four clonal complexes (CCs). None of the isolates shared the same ST or CCs with isolates from other countries or from other parts of China. Over half of the isolates were multidrug-resistant (MDR), with 17/26 C. freundii, 5/6 C. braakii, and 3/14 C. koseri isolates being MDR. Moreover, four isolates were carbapenem resistant with resistance to imipenem or meropenem. Among eight quinolone resistant C. freundii, all had a mutation in codon 59 (Thr59Ile) in quinolone resistance determining region of the gyrA gene. Only a small proportion of the isolates were found to be highly cytotoxic and adhesive with no correlation to sample sources.

Conclusions

There was a diverse range of Citrobacter isolates causing extraintestinal infections and a high prevalence of MDR.

Peritonitis from facultative anaerobic gram-negative bacilli likely due to translocation of bacteria from gut in a patient undergoing peritoneal dialysis

The peritonitis caused by gram-negative organisms is a serious complication encountered in patients undergoing peritoneal dialysis, often causing high morbidity and mortality. There has been recognition of peritonitis caused by uncommon organisms because of improved microbiological detection techniques. The healthcare providers involved in the management of these patients should be very vigilant. We report a rare case of peritonitis caused by Citrobacter freundii. A 42-year-old male on peritoneal dialysis for five years presented with abdominal pain and cloudy effluent. The peritoneal fluid analysis was consistent with peritonitis, and peritoneal fluid culture grew Citrobacter freundii. The patient was treated with two courses of double antibiotic coverage with intraperitoneal ceftazidime and oral ciprofloxacin, which failed to resolve the infection and hence resulted in the removal the peritoneal dialysis catheter and dialysis modality change.

Lineage, Antimicrobial Resistance and Virulence of Citrobacter spp

Citrobacter spp. are opportunistic human pathogens which can cause nosocomial infections, sporadic infections and outbreaks. In order to determine the genetic diversity, in vitro virulence properties and antimicrobial resistance profiles of Citrobacter spp., 128 Citrobacter isolates obtained from human diarrheal patients, foods and environment were assessed by multilocus sequence typing (MLST), antimicrobial susceptibility testing and adhesion and cytotoxicity testing to HEp-2 cells. The 128 Citrobacter isolates were typed into 123 sequence types (STs) of which 101 were novel STs, and these STs were divided into five lineages. Lineages I and II contained C. freundii isolates; Lineage III contained all C. braakii isolates, while Lineage IV and V contained C. youngae isolates. Lineages II and V contained more adhesive and cytotoxic isolates than Lineages I, III, and IV. Fifty-one of the 128 isolates were found to be multidrug-resistant (MDR, ≥3) and mainly distributed in Lineages I, II, and III. The prevalence of quinolone resistance varied with Lineage III (C. braakii) having the highest proportion of resistant isolates (52.6%), followed by Lineage I (C. freundii) with 23.7%. Seven qnrB variants, including two new alleles (qnrB93 and qnrB94) were found with Lineage I being the main reservoir. In summary, highly cytotoxic MDR isolates from diarrheal patients may increase the risk of severe disease.

Microbiological survey of sugar gliders (Petaurus breviceps) kept as pets in Italy

The sugar glider (Petaurus breviceps) is a small, arboreal, nocturnal, gliding mammalian possum belonging to the marsupial infraclass. Exotic marsupials, including sugar gliders, are becoming popular companion pets and, consequently, the risk of potential infections that can be transmitted to humans should be investigated. Data on the role of the sugar glider as a possible carrier of pathogenic and zoonotic bacteria are scarce and fragmentary. Therefore, this study is aimed at evaluating the prevalence of potentially zoonotic bacteria (Salmonella spp., Escherichia coli, Campylobacter spp., Pseudomonas spp., Klebsiella spp., Listeria monocytogenes and Yersinia enterocolitica) in 64 sugar gliders kept as pets in Italy. The highest prevalence of infection pertained to members of the family Enterobacteriaceae, in particular Citrobacter spp. (50%), Enterobacter spp. (28·1%) and Klebsiella pneumoniae (15·6%); Pseudomonas aeruginosa was isolated from 10 out of 64 samples (15·6%). All strains of Klebsiella pneumoniae exhibited some level of resistance to multiple antimicrobials (ampicillin, amoxicillin-clavulanic acid and doxycycline). SIGNIFICANCE AND IMPACT OF THE STUDY: The results of this study show that sugar gliders may act as carriers of potentially pathogenic agents for humans and other animal species, therefore caution should be exercised in the handling and contact with these animals.

Development of rapid and simple experimental and in silico serotyping systems for Citrobacter

Aim:

Members of the genus Citrobacter are important opportunistic pathogens responsible for high mortality rate. Therefore, in this study, we aimed to develop efficient and accurate Citrobacter typing schemes for clinical detection and epidemiological surveillance.

Materials & methods:

Using genomic and experimental analyses, we located the O-antigen biosynthesis gene clusters in Citrobacter genome for the first time, and used comparative genomic analyses to reveal the specific genes in different Citrobacter serotypes.

Results:

Based on the specific genes in O-antigen biosynthesis gene clusters of Citrobacter, we established experimental and in silico serotyping systems for this bacterium.

Conclusion:

Both serotyping tools are reliable, and our observations are biologically and clinically relevant for understanding and managing Citrobacter infection.

Antimicrobial Resistance and Cytotoxicity of Citrobacter spp. in Maanshan Anhui Province, China

Objectives:Citrobacter spp. especially Citrobacter freundii, is frequently causing nosocomial infections, and increasingly becoming multi-drug resistant (MDR). In this study, we aimed to determine the genetic diversity and relationships of Citrobacter spp. from diarrheal patients and food sources, their antimicrobial resistance profiles and in vitro virulence properties.

Methods: Sixty two Citrobacter isolates, including 13 C. freundii, 41 C. youngae and eight C. braakii isolates, were obtained from human diarrheal patients and food sources. Multilocus Sequence Typing (MLST) of seven housekeeping genes and antimicrobial susceptibility testing using the broth microdilution method according to CLSI recommendations were carried out. Adhesion and cytotoxicity to HEp-2 cells were performed. PCR and sequencing were used to identify bla_CTX−M, bla_SHV, bla_TEM and qnr genes.

Results: The 62 isolates were divided into 53 sequence types (STs) with all STs being novel, displaying high genetic diversity. ST39 was a predominant ST shared by 5 C. youngae strains isolated from four foods and a diarrheal patient. All isolates were resistant to cefoxitin, and sensitive to imipenem, meropenem and amikacin. The majority of Citrobacter isolates (61.3%) were MDR of three or more antibiotics out of the 22 antibiotics tested. Two C. freundii isolates each carried the bla_TEM−1 gene and a variant of qnrB77. Three Citrobacter isolates each carried qnrS1 and aac(6')-Ib-cr genes. Seven isolates that showed strong cytotoxicity to HEp-2 cells were MDR.

Conclusions:Citrobacter spp. from human and food sources are diverse with variation in virulence properties and antibiotic resistance profiles. Food may be an important source of Citrobacter species in transmission to humans. C. freundii and C. youngae are potential foodborne pathogens.

Severe peritonitis caused by Citrobacter freundii and successful treatment with double antibiotic coverage

Serratia, Pseudomonas/Providencia, indole-positive Proteus/Acinetobacter/Morganella, Citrobacter, Enterobacter and Hafnia group of organisms cause peritoneal dialysis (PD)-related peritonitis with high morbidity and mortality. Peritonitis caused by Citrobacter freundii is uncommon, and it may lead to catheter removal despite antimicrobial treatment. We describe a case of PD-related peritonitis caused by C. freundii, which was successfully treated with double antibiotic coverage.

Acinetobacter peritoneal dialysis peritonitis: a changing landscape over time

Background

Acinetobacter species are assuming an increasingly important role in modern medicine, with their persistent presence in health-care settings and antibiotic resistance. However, clinical reports addressing this issue in patients with peritoneal dialysis (PD) peritonitis are rare.

Methods

All PD peritonitis episodes caused by Acinetobacter that occurred between 1985 and 2012 at a single centre were retrospectively reviewed. Clinical features, microbiological data, and outcomes were analysed, with stratifications based upon temporal periods (before and after 2000).

Results

Acinetobacter species were responsible for 26 PD peritonitis episodes (3.5% of all episodes) in 25 patients. A. baumannii was the most common pathogen (54%), followed by A. iwoffii (35%), with the former being predominant after 2000. Significantly more episodes resulted from breaks in exchange sterility after 2000, while those from exit site infections decreased (P = 0.01). The interval between the last and current peritonitis episodes lengthened significantly after 2000 (5 vs. 13.6 months; P = 0.05). All the isolates were susceptible to cefepime, fluoroquinolone, and aminoglycosides, with a low ceftazidime resistance rate (16%). Nearly half of the patients (46%) required hospitalisation for their Acinetobacter PD-associated peritonitis, and 27% required an antibiotic switch. The overall outcome was fair, with no mortality and a 12% technique failure rate, without obvious interval differences.

Conclusions

The temporal change in the microbiology and origin of Acinetobacter PD-associated peritonitis in our cohort suggested an important evolutional trend. Appropriate measures, including technique re-education and sterility maintenance, should be taken to decrease the Acinetobacter peritonitis incidence in PD patients.

Viridans streptococci in peritoneal dialysis peritonitis: clinical courses and long-term outcomes

BACKGROUND

The clinical courses and long-term outcomes of viridans streptococcus (VS) peritoneal dialysis (PD) peritonitis remain unclear.

METHODS

We conducted a retrospective analysis of all PD patients in a single center with gram-positive cocci (GPC) peritonitis between 2005 and 2011, and divided them into 3 groups: VS, other streptococci and other GPC (apart from VS). Clinical characteristics and outcomes of the VS group were compared with the other streptococci and other GPC groups, with prognostic factors determined.

RESULTS

A total of 140 patients with 168 episodes of GPC peritonitis (44% of all peritonitis) were identified over 7 years. Among these, 18 patients (13%) developed VS peritonitis, while 14 patients (10%) developed other streptococcal peritonitis. Patients with VS peritonitis had a high cure rate by antibiotic alone (94%), despite a high polymicrobial yield frequency (28%). We found that VS peritonitis carried a lower risk of Tenckhoff catheter removal and relapsing episodes than other GPC peritonitis (6% vs 11%), and a lower mortality than other streptococci peritonitis (0% vs 7%). However, after the index peritonitis episodes, VS, other streptococci, and other GPC group had a significantly increased peritonitis incidence compared with the period before the index peritonitis (all p < 0.01). Patients with VS peritonitis had a significantly higher incidence of refractory peritonitis compared with other streptococci or other GPC peritonitis in the long term (both p < 0.01).

CONCLUSIONS

VS poses a higher risk of subsequent refractory peritonitis after the index episode as compared with other streptococcal or GPC peritonitis. It might be prudent to monitor the technique of these patients with VS peritonitis closely to avoid further peritonitis episodes.