Rahnella aquatilis sepsis in an immunocompetent adult

Timber-colonizing gram-negative bacteria as potential causative agents of respiratory diseases in woodworkers

Occurrence

Gram-negative bacteria occur commonly in the inner tissues of stored coniferous and deciduous timber, showing a marked variation in numbers. The greatest maximal numbers are found in the sapwood of coniferous timber. The common constituents of the Gram-negative biota are potentially pathogenic species of Enterobacteriaceae family of the genera Rahnella, Pantoea, Enterobacter, and Klebsiella. The air of wood-processing facilities is polluted with the wood-borne Gram-negative bacteria and produced by them endotoxin, as demonstrated worldwide by numerous studies.

Effects

There are three potential pathways of the pathogenic impact of wood-borne Gram-negative bacteria on exposed woodworkers: allergic, immunotoxic, and infectious. Allergic impact has been underestimated for a long time with relation to Gram-negative bacteria. Hopefully, the recent demonstration of the first documented case of hypersensitivity pneumonitis (HP) in woodworkers caused by Pantoea agglomerans which developed in extremely large quantities in birch sapwood, would speed up finding of new wood-related cases of HP caused by Gram-negative bacteria. The second pathway is associated with endotoxin, exerting strong immunotoxic (excessively immunostimulative) action. It has been demonstrated that endotoxin is released into wood dust in the form of nano-sized microvesicles, by peeling off the outer membrane of bacteria. Endotoxin microvesicles are easily inhaled by humans together with dust because of small dimensions and aerodynamic shape. Afterwards, they cause a nonspecific activation of lung macrophages, which release numerous inflammatory mediators causing an inflammatory lung reaction, chest tightness, fever, gas exchange disorders, and bronchospasm, without radiographic changes. The resulting disease is known as “Organic Dust Toxic Syndrome” or “toxic pneumonitis.” The potential third pathway of pathogenic impact is infection. The suspected species is Klebsiella pneumoniae that may occur commonly in wood dust; however, until now this pathway has not been confirmed.

Conclusion

Summarizing, Gram-negative bacteria-inhabiting timber should be considered, besides filamentous fungi and actinobacteria, as important risk factors of occupational disease in woodworkers that could be either HP with allergenic background or toxic pneumonitis elicited by endotoxin.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00420-021-01829-1.

Septic Shock Caused by Rahnella aquatilis Bacteremia in an Immunocompetent Adult

Patient: Male, 37-year-old

Final Diagnosis: Septic shock

Symptoms: Fever • rigors

Medication: —

Clinical Procedure: —

Specialty: Infectious Diseases

Comparative analysis of the tonsillar microbiota in IgA nephropathy and other glomerular diseases

Immunoglobulin A nephropathy (IgAN) involves repeated events of gross haematuria with concurrent upper airway infections. The mucosal immune system, especially the tonsil, is considered the initial site of inflammation, although the role of the tonsillar microbiota has not been established in IgAN. In this study, we compared the tonsillar microbiota of patients with IgAN (n = 21) and other glomerular diseases (n = 36) as well as, healthy controls (n = 23) from three medical centres in Korea. The microbiota was analysed from tonsil swabs using the Illumina MiSeq system based on 16S rRNA gene. Tonsillar bacterial diversity was higher in IgAN than in other glomerular diseases, although it did not differ from that of healthy controls. Principal coordinates analysis revealed differences between the tonsillar microbiota of IgAN and both healthy and disease controls. The proportions of Rahnella, Ruminococcus_g2, and Clostridium_g21 were significantly higher in patients with IgAN than in healthy controls (corrected p < 0.05). The relative abundances of several taxa were correlated with the estimated glomerular filtration rate, blood urea nitrogen, haemoglobin, and serum albumin levels. Based on our findings, tonsillar microbiota may be associated with clinical features and possible immunologic pathogenesis of IgAN.

Characterization of Mechanisms Lowering Susceptibility to Flumequine among Bacteria Isolated from Chilean Salmonid Farms

Despite their great importance for human therapy, quinolones are still used in Chilean salmon farming, with flumequine and oxolinic acid currently approved for use in this industry. The aim of this study was to improve our knowledge of the mechanisms conferring low susceptibility or resistance to quinolones among bacteria recovered from Chilean salmon farms. Sixty-five isolates exhibiting resistance, reduced susceptibility, or susceptibility to flumequine recovered from salmon farms were identified by their 16S rRNA genes, detecting a high predominance of species belonging to the Pseudomonas genus (52%). The minimum inhibitory concentrations (MIC) of flumequine in the absence and presence of the efflux pump inhibitor (EPI) Phe-Arg-β-naphthylamide and resistance patterns of isolates were determined by a microdilution broth and disk diffusion assays, respectively, observing MIC values ranging from 0.25 to >64 µg/mL and a high level of multi-resistance (96%), mostly showing resistance to florfenicol and oxytetracycline. Furthermore, mechanisms conferring low susceptibility to quinolones mediated by efflux pump activity, quinolone target mutations, or horizontally acquired resistance genes (qepA, oqxA, aac(6′)-lb-cr, qnr) were investigated. Among isolates exhibiting resistance to flumequine (≥16 µg/mL), the occurrence of chromosomal mutations in target protein GyrA appears to be unusual (three out of 15), contrasting with the high incidence of mutations in GyrB (14 out of 17). Bacterial isolates showing resistance or reduced susceptibility to quinolones mediated by efflux pumps appear to be highly prevalent (49 isolates, 75%), thus suggesting a major role of intrinsic resistance mediated by active efflux.

Bacteremia due to Rahnella aquatilis in a Patient with a Chemoport

Rahnella aquatilis, a saprophytic organism, is a member of the Enterobacteriaceae family. The natural habitat of this organism is fresh water, and it is rarely found in clinical specimens. Clinical conditions ascribed to this organism include bacteremia, respiratory infection, urinary tract infection, wound infection in an immunocompromised host, and infective endocarditis in patients with congenital heart diseases. Here, we report a case of bacteremia due to R. aquatilis in a woman with breast cancer who had received chemotherapy through a chemoport. To our knowledge, this is the second case of bacteremia caused by this organism in a patient with cancer in Korea.

Extended-Spectrum β-Lactamase, AmpC, and MBL-Producing Gram-Negative Bacteria on Fresh Vegetables and Ready-to-Eat Salads Sold in Local Markets

We investigated the occurrence of extended-spectrum β-lactamase (ESBL), AmpC, and carbapenemase-producing Gram-negative bacteria isolated from 160 samples of fresh vegetables (n = 80) and ready-to-eat (RTE) prepacked salads (n = 80). Phenotypic and genotypic analyses were carried out on the isolates in terms of the species present and relative resistance. Resistance to β-lactam antibiotics was found in only 44 (24 from fresh vegetables and 20 from RTE salads) of a total of 312 Gram-negative strains (14.1%). The prevalence of ESBL-producing strains from fresh vegetables was 83.3% (20/24) and 16.7% (4/24) for AmpC. Among the 20 bacterial isolates from RTE salads, 80% (16/20) were identified as ESBL-producing strains and the remaining 20% (4/20) as MBL-producing strains. PCR and sequencing confirmed the presence of bla_SHV-12, bla_CTX-M-1, bla_CTX-M-15, bla_RHAN-1, bla_ACC-1, bla_DHA-1, bla_VIM-1, and bla_IMP-1. Seven different replicons were identified, where IncHI1, FIA, and I1 were the most representative types; when compared with the Inc types, isolates from fresh vegetables and RTE salads were similar. The location of genes on a conjugative plasmid was confirmed by positive results obtained with conjugation assays. Our study has demonstrated the occurrence and distribution of ESBL/AmpC and MBL strains in fresh vegetables and RTE salads in Italy and possible public health risks associated with consumption of these fresh products.

Infections Caused by Antimicrobial Drug-Resistant Saprophytic Gram-Negative Bacteria in the Environment

Background

Drug-resistance genes found in human bacterial pathogens are increasingly recognized in saprophytic Gram-negative bacteria (GNB) from environmental sources. The clinical implication of such environmental GNBs is unknown.

Objectives

We conducted a systematic review to determine how often such saprophytic GNBs cause human infections.

Methods

We queried PubMed for articles published in English, Spanish, and French between January 2006 and July 2014 for 20 common environmental saprophytic GNB species, using search terms “infections,” “human infections,” “hospital infection.” We analyzed 251 of 1,275 non-duplicate publications that satisfied our selection criteria. Saprophytes implicated in blood stream infection (BSI), urinary tract infection (UTI), skin and soft tissue infection (SSTI), post-surgical infection (PSI), osteomyelitis (Osteo), and pneumonia (PNA) were quantitatively assessed.

Results

Thirteen of the 20 queried GNB saprophytic species were implicated in 674 distinct infection episodes from 45 countries. The most common species included Enterobacter aerogenes, Pantoea agglomerans, and Pseudomonas putida. Of these infections, 443 (66%) had BSI, 48 (7%) had SSTI, 36 (5%) had UTI, 28 (4%) had PSI, 21 (3%) had PNA, 16 (3%) had Osteo, and 82 (12%) had other infections. Nearly all infections occurred in subjects with comorbidities. Resistant strains harbored extended-spectrum beta-lactamase (ESBL), carbapenemase, and metallo-β-lactamase genes recognized in human pathogens.

Conclusion

These observations show that saprophytic GNB organisms that harbor recognized drug-resistance genes cause a wide spectrum of infections, especially as opportunistic pathogens. Such GNB saprophytes may become increasingly more common in healthcare settings, as has already been observed with other environmental GNBs such as Acinetobacter baumannii and Pseudomonas aeruginosa.

Environmental Isolate of Rahnella aquatilis Harbors Class 1 Integron

The paper presents first description of class 1 integron in an environmental strain of Rahnella aquatilis, a rarely isolated Gram-negative bacterium of the family Enterobacteriaceae. The strain was isolated from the Warta river water, Poland. Class 1 integrase gene was detected by a PCR assay. Sequencing of the integron’s variable region showed the presence of a dfrA1-aadA1 gene cassette array. The integron was located in a 54-kbp plasmid that was transferable to Escherichia coli J-53 recipient strain in a conjugation assay. The integron-bearing R. aquatilis strain was resistant to aminoglycosides, penicillins, trimethoprim, sulfamethoxazole, and trimethoprim/sulfamethoxazole. This paper confirms that water environment play a major role in the spread of integrons and, consequently, antimicrobial resistance, among bacteria of various genera.

Co-transmission of Rahnella aquatilis between hospitalized patients

Rahnella aquatilis is an environmental Gram-negative bacillus that is rarely reported as human pathogen, being mainly associated with infections in immunocompromised patients. Herein we describe two cases of R. aquatilis isolates recovered from endotracheal aspirate cultures of different patients in a tertiary hospital located in the city of São Paulo, Brazil. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 16S rDNA gene sequencing were performed to confirm bacterial identification after the isolates being erroneously identified as Pantoea spp. by automated system. Both isolates showed the same PFGE pattern and presented the β-lactamase encoding gene blaRAHN-1, responsible for resistance to cephalothin. The isolates were susceptible to broad-spectrum cephalosporins, carbapenems, fluoroquinolones, aminoglycosides, and polymyxin B. This report shows the presence and transmission of uncommon bacteria in the nosocomial environment and alerts us about the need for new tools of correct microbiologic diagnosis.

Rahnella aquatilis Sepsis in a Premature Newborn

Rahnella aquatilis is an infrequently isolated Gram-negative rod within the Enterobacteriaceae family. The organism's natural habitat is water. The organism is rarely isolated from clinical specimens and it seldom causes infection in immunocompetent individuals. Here we present a one-month-old boy who was born prematurely at 27th week of gestation by cesarean section with a birth weight of 730 g. He developed sepsis caused by Rahnella aquatilis during the treatment for ventilator associated pneumonia due to Stenotrophomonas maltophilia with ciprofloxacin. He was successfully treated with a combination of amikacin plus meropenem. Although R. aquatilis is one of the saprophyticus organisms, it may cause life-threatening infection in newborn.

Evaluation of microbial load in oropharyngeal mucosa from tannery workers

Background

Animal skin provides an ideal medium for the propagation of microorganisms and it is used like raw material in the tannery and footware industry. The aim of this study was to evaluate and identify the microbial load in oropharyngeal mucosa of tannery employees.

Methods

The health risk was estimated based on the identification of microorganisms found in the oropharyngeal mucosa samples. The study was conducted in a tanners group and a control group. Samples were taken from oropharyngeal mucosa and inoculated on plates with selective medium. In the samples, bacteria were identified by 16S ribosomal DNA analysis and the yeasts through a presumptive method. In addition, the sensitivity of these microorganisms to antibiotics/antifungals was evaluated.

Results

The identified bacteria belonged to the families Enterobacteriaceae, Pseudomonadaceae, Neisseriaceae, Alcaligenaceae, Moraxellaceae, and Xanthomonadaceae, of which some species are considered as pathogenic or opportunistic microorganisms; these bacteria were not present in the control group. Forty-two percent of bacteria identified in the tanners group are correlated with respiratory diseases. Yeasts were also identified, including the following species: Candida glabrata, Candida tropicalis, Candida albicans, and Candida krusei. Regarding the sensitivity test of bacteria identified in the tanners group, 90% showed sensitivity to piperacillin/tazobactam, 87% showed sensitivity to ticarcillin/clavulanic acid, 74% showed sensitivity to ampicillin/sulbactam, and 58% showed sensitivity to amoxicillin/clavulanic acid.

Conclusion

Several of the bacteria and yeast identified in the oropharyngeal mucosa of tanners have been correlated with infections in humans and have already been reported as airborne microorganisms in this working environment, representing a health risk for workers.

Functional metagenomics reveals previously unrecognized diversity of antibiotic resistance genes in gulls

Wildlife may facilitate the spread of antibiotic resistance (AR) between human-dominated habitats and the surrounding environment. Here, we use functional metagenomics to survey the diversity and genomic context of AR genes in gulls. Using this approach, we found a variety of AR genes not previously detected in gulls and wildlife, including class A and C β-lactamases as well as six tetracycline resistance gene types. An analysis of the flanking sequences indicates that most of these genes are present in Enterobacteriaceae and various Gram-positive bacteria. In addition to finding known gene types, we detected 31 previously undescribed AR genes. These undescribed genes include one most similar to an uncharacterized gene in Verrucomicrobium and another to a putative DNA repair protein in Lactobacillus. Overall, the study more than doubled the number of clinically relevant AR gene types known to be carried by gulls or by wildlife in general. Together with the propensity of gulls to visit human-dominated habitats, this high diversity of AR gene types suggests that gulls could facilitate the spread of AR.

Triclosan-resistant bacteria isolated from feedlot and residential soils

Triclosan is an antimicrobial agent that is currently incorporated into hundreds of consumer and medical products. It can be either a bacteriostatic or bactericidal agent, depending on its formulation. It has activity against Gram-positive and Gram-negative bacteria, as well as some viruses and protists. The purpose of this study was to determine whether triclosan-resistant bacteria could be isolated from the soil. Soils from cattle feedlots and residential lawns were collected and assayed for the presence of these organisms by plating samples on growth media containing triclosan. Organisms were subsequently identified by partial 16S rRNA sequencing analysis. All the organisms isolated in this study were Gram-negative rods, with members of genus Pseudomonas being particularly well represented. This result may not be surprising because Gram-negative organisms are generally more resistant to triclosan, and since Pseudomonas bacteria are known to have numerous efflux mechanisms for dealing with harmful substances.

Infection caused by Rahnella aquatilis

The authors report a case of a 27-year-old African American woman with sickle cell disease who developed septic shock caused by a Rahnella aquatilis infection associated with a peripherally inserted central venous catheter. The infection was treated successfully with ciprofloxacin. R aquatilis is a Gram-negative rod, first isolated from freshwater in 1976, which has been linked to human disease in rare instances, most commonly in immunosuppressed individuals. In addition to this case report, the authors also review the literature.

Frequency and diversity of small cryptic plasmids in the genus Rahnella

BACKGROUND

Rahnella is a widely distributed genus belonging to the Enterobacteriaceae and frequently present on vegetables. Although Rahnella has interesting agro-economical and industrial properties and several strains possess antibiotic resistances and toxin genes which might spread within microbial communities, little is known about plasmids of this genus. Thus, we isolated a number of Rahnella strains and investigated their complements of small plasmids.

RESULTS

In total 53 strains were investigated and 11 plasmids observed. Seven belonged to the ColE1 family; one was ColE2-like and three shared homology to rolling circle plasmids. One of them belonged to the pC194/pUB110 family and two showed similarity to poorly characterised plasmid groups. The G+C content of two rolling circle plasmids deviated considerably from that of Rahnella, indicating that their usual hosts might belong to other genera. Most ColE1-like plasmids formed a subgroup within the ColE1 family that seems to be fairly specific for Rahnella. Intriguingly, the multimer resolution sites of all ColE1-like plasmids had the same orientation with respect to the origin of replication. This arrangement might be necessary to prevent inappropriate synthesis of a small regulatory RNA that regulates cell division. Although the ColE1-like plasmids did not possess any mobilisation system, they shared large parts with high sequence identity in coding and non-coding regions. In addition, highly homologous regions of plasmids isolated from Rahnella and the chromosomes of Erwinia tasmaniensis and Photorhabdus luminescens could be identified.

CONCLUSIONS

For the genus Rahnella we observed plasmid-containing isolates at a frequency of 19%, which is in the average range for Enterobacteriaceae. These plasmids belonged to different groups with members of the ColE1-family most frequently found. Regions of striking sequence homology of plasmids and bacterial chromosomes highlight the importance of plasmids for lateral gene transfer (including chromosomal sequences) to distinct genera.

Rahnella aquatilis bacteremia from a suspected urinary source

A 76-year-old male with prostatic hyperplasia presented with acute pyelonephritis. Blood cultures yielded Rahnella aquatilis. Treatment with intravenous followed by oral levofloxacin resulted in cure. Important characteristics of this organism include its biochemical similarities to Enterobacter agglomerans, its apparent ability to cause bacteremia from a renal focus, and its response to quinolone therapy.

Characterization of two antagonistic strains ofRahnella aquatilis isolated from soil in egypt

In an attempt to obtain biological control agents for controlling bacterial spot of cucumber, over 250 bacterial strains were isolated from agricultural soil samples, collected from different localities in Giza Governorate (Egypt) and screened for in vitro antibiosis towards Xanthomonas campestris. Only 2 strains showed antagonistic activity. They and their culture filtrates restricted the growth of a number of G- and G(+)-indicator bacteria. On Chrome Azurol S agar, both strains exhibited a marked siderophore production. Biolog plates identified these strains as Rahnella aquatilis. Their characteristics were studied and compared with literature data on R. aquatilis. This antagonistic bacterium has not been previously isolated in Egypt.

Identity and antibiotic susceptibility of enterobacterial flora of salad vegetables

The enterobacterial flora from carrots (organic and non-organic) and salad vegetables has been identified and antibiotic susceptibilities determined. Pseudomonas fluorescens and Pantoea (formerly Enterobacter) agglomerans were the species most commonly found; the former was usually resistant to at least six of the antibiotics under test. Rahnella aquatilis (often producing beta-lactamase) was also found in carrots. There were no clear differences in flora from organic and non-organic carrots. Thus, uncooked vegetables are a potential source of highly resistant opportunistic pathogens.