The impact of production of extended-spectrum β-lactamases on the 28-day mortality rate of patients with Proteus mirabilis bacteremia in Korea

Proteus species bloodstream infections: Comparative epidemiology of three species

BACKGROUND

Although Proteus species are occasional causes of serious infections, their epidemiology has not been well defined. The objective was to describe the overall and species-specific occurrence and determinants of Proteus species bloodstream infection (BSI) in a large Australian population.

METHODS

All Queensland residents with Proteus species BSI identified within the publicly funded healthcare system between 2000 and 2019 were included.

RESULTS

A total of 2,143 incident episodes of Proteus species BSI were identified among 2,079 Queensland residents. The prevalence of comorbid illness differed with higher Charlson comorbidity scores observed with P. penneri and P. vulgaris, and higher prevalence of liver disease with P. penneri, higher comorbid cancer with P. vulgaris, and lower diabetes and renal disease prevalence with P. mirabilis BSIs.

CONCLUSION

This study provides novel information on the epidemiology of Proteus species BSI.

Population-based study of Morganella-Proteus-Providencia group bloodstream infections

Background

There is a paucity of studies investigating the population-based epidemiology of Morganella-Proteus-Providencia (MPP) group infections. Our objective was to determine the incidence, risk factors, and outcome of MPP group bloodstream infections (BSI), and explore species-specific differences.

Methods

Population-based surveillance was conducted in the western interior of British Columbia, Canada, between April 1, 2010 and March 30, 2020.

Results

Sixty-two incident MPP group BSI occurred for an annual incidence of 3.4 per 100,000 residents; rates for Morganella morganii, Proteus mirabilis, and Providencia species were 0.5, 2.6, and 0.3 per 100,000 population, respectively. The median year of age was 72.5 and was different (p = 0.03) among the groups. Most (92%) MPP group BSIs were of community-onset. Significant differences were observed in the distribution of clinical focus of infection, with most notably 81% of P. mirabilis BSI due to genitourinary focus as compared to 60% and 22% for Providencia species and M. morganii, respectively. Comorbid illnesses that increased the risk for development of MPP group BSI (incidence rate ratio; 95% CI) were HIV infection (37.0; 4.4-139.6), dementia (11.5; 6.1-20.7), cancer (6.4; 3.2-11.9), stroke 6.5 (2.8-13.3), and diabetes 2.7 (1.3-5.0). Thirteen, one, and none of the cases with P. mirabilis, M. morganii, and Providencia species BSI died within 30 days of index culture for respective all cause case-fatalities of 27%, 11%, and 0% (p = 0.1).

Conclusions

Although collectively responsible for a substantial burden of illness, the epidemiology of MPP group BSI varies significantly by species.

Abundance and prevalence of ESBL coding genes in patients undergoing first line eradication therapy for Helicobacter pylori

The spread of extended-spectrum beta-lactamases (ESBLs) in nosocomial and community-acquired enterobacteria is an important challenge for clinicians due to the limited therapeutic options for infections that are caused by these organisms. Here, we developed a panel of ESBL coding genes, evaluated the abundance and prevalence of ESBL encoding genes in patients undergoing H. pylori eradication therapy, and summarized the effects of eradication therapy on functional profiles of the gut microbiome. To assess the repertoire of known beta lactamase (BL) genes, they were divided into clusters according to their evolutionary relation. Primers were designed for amplification of cluster marker regions, and the efficiency of this amplification panel was assessed in 120 fecal samples acquired from 60 patients undergoing H. pylori eradication therapy. In addition, fecal samples from an additional 30 patients were used to validate the detection efficiency of the developed ESBL panel. The presence for majority of targeted clusters was confirmed by NGS of amplification products. Metagenomic sequencing revealed that the abundance of ESBL genes within the pool of microorganisms was very low. The global relative abundances of the ESBL-coding gene clusters did not differ significantly among treatment states. However, at the level of each cluster, classical ESBL producers such as Klebsiella sp. for blaOXY (p = 0.0076), Acinetobacter sp. for blaADC (p = 0.02297) and others, differed significantly with a tendency to decrease compared to the pre- and post-eradication states. Only 13 clusters were common across all three datasets, suggesting a patient-specific distribution profile of ESBL-coding genes. The number of AMR genes detected in the post-eradication state was higher than that in the pre-eradication state, which could be attributed, at least in part, to the therapy. This study demonstrated that the ESBL screening panel was effective in targeting ESBL-coding gene clusters from bacterial DNA and that minor differences exist in the abundance and prevalence of ESBL-coding gene levels before and after eradication therapy.

Rapid determination of Proteus mirabilis susceptibility to antibiotics using infrared spectroscopy in tandem with random forest

Bacterial infections cause serious illnesses that are treated with antibiotics. Currently used methods for detecting bacterial antibiotic susceptibility consume 48-72 h, leading to overuse of antibiotics. Thus, many bacterial species have acquired resistance to a broad range of available antibiotics. There is an urgent need to develop efficient methods for rapid determination of bacterial susceptibility to antibiotics. The combination of machine learning and Fourier-transform infrared (FTIR) spectroscopy has generated a promising diagnostic approach in medicine and biology. Our main goal is to examine the potential of FTIR spectroscopy to determine the susceptibility of urinary tract infection-Proteus mirabilis to a specific range of antibiotics, within about 20 min after 24 h culture and identification. We measured the infrared spectra of 489 different P. mirabilis isolates and used random forest to analyze this spectral database. A classification success rate of ~84% was achieved in differentiating between the resistant and sensitive isolates based on their susceptibility to ceftazidime, ceftriaxone, cefuroxime, cefuroxime axetil, cephalexin, ciprofloxacin, gentamicin, and sulfamethoxazole antibiotics in a time span of 24 h instead of 48 h.

Prevalence, antibiotic profile, virulence determinants, ESBLs, and non-β-lactam encoding genes of MDR Proteus spp. isolated from infected dogs

This study investigated the prevalence, antibiogram, virulence, extended-spectrum β-lactamases (ESBLs), and non-β-lactam encoding genes of Proteus species isolated from infected dogs in Ismailia province, Egypt. The study was conducted on 70 fecal swabs collected from dogs with diarrhea for bacteriological identification of Proteus spp. The positive isolates were evaluated for antibiotic susceptibility, molecular tests of virulence, ESBLs, and non-β-lactam encoding genes. Prevalence of Proteus spp. was 35.7% (25/70), including Proteus mirabilis (n = 23) and Proteus vulgaris (n = 2). The Proteus spp. prevalence revealed diversity, higher in males than females, in ages < 12 weeks. Investigation of antimicrobial resistance was found against penicillin and amoxicillin (100%), amoxicillin–clavulanic acid (32%), cephalosporins: cefotaxime and ceftazidime (36%), and monobactam: aztreonam (28%) as ESBLs, in addition to tetracycline (32%) and trimethoprim sulfamethoxazole (100%). The strains retrieved by PCR revealed ureC, zapA, and rsbA virulence genes with variant prevalence as 92%, 60%, and 52%, respectively. In addition, the recovered strains contained ESBL genes with a dramatic variable prevalence of 100%, 92%, 36%, and 32%, to blaTEM, blaSHV, blaCTX-M, and blaOXA-1, respectively, and non β-lactam encoding genes with a prevalence of 100%, 48%, 44%, 20%, and 12%, to sul1, tetA, intI1, qnrA, and aadA1. Moreover, 28% (7/25) of recovering strains were MDR (multidrug-resistant) up to four classes of antimicrobials, and 48% (12/25) of the examined strains were MDR up to three antimicrobial classes. In conclusion, to the best of our knowledge, our study could be the first report recording MDR Proteus spp. in dogs in Egypt.

Antibiotic Resistance in Proteus mirabilis: Mechanism, Status, and Public Health Significance

Proteus mirabilis is a specific opportunistic pathogen of many infections including urinary tract infections (UTIs). Risk factors are linked with the acquisition of multidrug-resistant (MDR) to 3 or more classes of antimicrobials) strains. The resistance in extended-spectrum alpha-lactamase is rare, but the rising resistance in extended-spectrum beta-lactamase (ESBL) producing strains is a matter of concern. β-lactamases and antibiotic modifying enzymes mainly constitute the ESBLs resistance mechanism by hydrolyzing the antibiotics. Mutation or Porin loss could lead to the reduced permeability of antibiotics, enhanced efflux pump activity hindering the antibiotic access to the target site, antibiotic failure to bind at the target site because of the target modification, and lipopolysaccharide mutation causing the resistance against polymyxin antibiotics. This review aimed to explore various antimicrobial resistance mechanisms in Proteus mirabilis and their impact on public health status.

Detection of Carbapenem Resistance of Proteus mirabilis Strains Isolated from Foxes, Raccoons and Minks in China

Proteus mirabilis, an opportunistic pathogen, is found to be an emerging threat to both animals and humans for a variety of infections. However, the characteristics of P. mirabilis infections from foxes, raccoons and minks remain unclear. In this context, we identified the antibiotic resistance genes and virulence genes of P. mirabilis isolates from foxes, raccoons and minks in China. Most isolates showed resistance to florfenicol (90.57%), trimethoprim-sulfamethoxazole (73.58%), and imipenem (71.70%). A total of 73.58% of isolates were resistant to antibiotics from at least three or more classes, and were categorized as multi-drug resistant. A total of 33.33% of the isolates were resistant to antibiotics from seven classes. The most prevalent resistant were sul1 (94.34%), followed by floR, blaTEM, aac(6’)Ib-cr and blaOXA-1 with the detection rate of 88.68%, 83.02%, 71.70% and 60.38%, respectively. Among the 51 P. mirabilis isolates that were resistant to beta-lactam antibiotics, all isolates carried at least one beta-lactam gene. In addition, blaNDM and blaOXA-24 genes were firstly reported in carbapenem-resistant P. mirabilis isolates from foxes, raccoons and minks. All isolates exhibited the virulence genes ureC, zapA, pmfA, atfA and mrpA. P. mirabilis isolates carrying all detected 10 virulence genes from different animal species showed different lethal abilities in a G. mellonella larvae model. More importantly, the profiles of antibiotic resistance genes of isolates from fur animals and the environment were generally similar, and phylogenetic analysis showed that the P. mirabilis isolates from farm environment samples may have close relatedness with that from animals.

Septic shock caused by a carbon dioxide-dependent and extended spectrum β-lactamase-producing Proteus mirabilis small colony variant in a long-term bedridden patient

Here, we report a 60-year-old chronically bedridden man with cerebral palsy who had septic shock following a history of urinary tract infection with extended spectrum β-lactamase-producing and auxotrophic Proteus mirabilis detected on blood and urine cultures. This auxotroph formed small colonies only on the blood agar at 24 h in 5% CO₂, but not in the conditions without CO₂, and lacked motility and some biochemical activities. The five-year history of stones in the right renal pelvis suggests chronic urinary tract infection with P. mirabilis requiring a 28-day antibiotic treatment. This paper highlights that the CO₂-dependent P. mirabilis small colony variant may cause sepsis, probably due to chronic infection in uroliths, which should warrant immediate identification.

Catalase Activity is Critical for Proteus mirabilis Biofilm Development, EPS Composition, and Dissemination During Catheter-Associated Urinary Tract Infection

Proteus mirabilis is a leading uropathogen of catheter-associated urinary tract infections (CAUTIs), which are among the most common healthcare-associated infections worldwide. A key factor that contributes to P. mirabilis pathogenesis and persistence during CAUTI is the formation of catheter biofilms, which provide increased resistance to antibiotic treatment and host defense mechanisms. Another factor that is important for bacterial persistence during CAUTI is the ability to resist reactive oxygen species (ROS), such as through the action of the catalase enzyme. Potent catalase activity is one of the defining biochemical characteristics of P. mirabilis, and the single catalase gene (katA) encoded in strain HI4320 was recently identified as a candidate fitness factor for UTI, CAUTI, and bacteremia. Here we show that disruption of katA results in increased ROS levels, increased sensitivity to peroxide, and decreased biofilm biomass. The biomass defect was due to a decrease in extracellular polymeric substances (EPS) production by the ΔkatA mutant, and specifically due to reduced carbohydrate content. Importantly, the biofilm defect resulted in decreased antibiotic resistance in vitro and a colonization defect during experimental CAUTI. The ΔkatA mutant also exhibited decreased fitness in a bacteremia model, supporting a dual role for catalase in P. mirabilis biofilm development and immune evasion.

Adverse clinical outcomes associated with infections by Enterobacterales producing ESBL (ESBL-E): a systematic review and meta-analysis

OBJECTIVES

Enterobacterales producing ESBL (ESBL-E) have been notable for their rapid expansion in community settings. This systematic review and meta-analysis aimed to summarize evidence investigating the association between ESBL-E infection and adverse clinical outcomes, defined as bacteraemia, sepsis or septic shock, and all-cause mortality in adult patients.

METHODS

Database search was conducted in PubMed, Scopus and EMBASE. In general, studies were screened for effect estimates of ESBL-E colonization or infection on clinical outcomes with non-ESBL-producing Enterobacterales as comparator, adult populations and molecular ascertainment of ESBL gene. Meta-analysis was performed using the inverse variance heterogeneity model.

RESULTS

Eighteen studies were identified, including 1399 ESBL-E and 3200 non-ESBL-E infected patients. Sixteen of these studies included only bacteraemic patients. Mortality was studied in 17 studies and ESBL-E infection was significantly associated with higher odds of mortality compared with non-ESBL-producing Enterobacterales infection (OR = 1.70, 95% CI: 1.15-2.49, I 2=58.3%). However, statistical significance did not persist when adjusted estimates were pooled (aOR = 1.67, 95% CI: 0.52-5.39, I 2=78.1%). Septic shock was studied in seven studies and all included only bacteraemic patients. No association between ESBL-E infection and shock was found (OR = 1.23, 95% CI: 0.75-2.02, I 2=14.8%). Only one study investigated the association between ESBL-E infection and bacteraemia.

CONCLUSIONS

Infections by ESBL-E appear to be significantly associated with mortality but not septic shock. Available studies investigating bacteraemia and shock as an intermediate outcome of ESBL-E infections are lacking. Future studies investigating the relationship between clinical outcomes and molecular characteristics of resistant strains are further warranted, along with studies investigating this in non-bacteraemic patients.

Multidrug-Resistant Proteus mirabilis Strain with Cointegrate Plasmid

Proteus mirabilis is a component of the normal intestinal microflora of humans and animals, but can cause urinary tract infections and even sepsis in hospital settings. In recent years, the number of multidrug-resistant P. mirabilis isolates, including the ones producing extended-spectrum β-lactamases (ESBLs), is increasing worldwide. However, the number of investigations dedicated to this species, especially, whole-genome sequencing, is much lower in comparison to the members of the ESKAPE pathogens group. This study presents a detailed analysis of clinical multidrug-resistant ESBL-producing P. mirabilis isolate using short- and long-read whole-genome sequencing, which allowed us to reveal possible horizontal gene transfer between Klebsiella pneumoniae and P. mirabilis plasmids and to locate the CRISPR-Cas system in the genome together with its probable phage targets, as well as multiple virulence genes. We believe that the data presented will contribute to the understanding of antibiotic resistance acquisition and virulence mechanisms for this important pathogen.

Antimicrobial Resistance in Swine Fecal Specimens Across Different Farm Management Systems

Antimicrobial use in agricultural animals is known to be associated with increases in antimicrobial resistance. Most prior studies have utilized culture and susceptibility testing of select organisms to document these phenomena. In this study we aimed to detect 66 antimicrobial resistance (AMR) genes for 10 antimicrobial agent classes directly in swine fecal samples using our previously developed antimicrobial resistance TaqMan array card (AMR-TAC) across three different swine farm management systems. This included 38 extensive antimicrobial use (both in treatment and feed), 30 limited antimicrobial use (treatment only), and 30 no antimicrobial use farms. The number of resistance genes detected in extensive antimicrobial use farms was higher than in limited and no antimicrobial use farms (28.2 genes ± 4.2 vs. 24.0 genes ± 4.1 and 22.8 genes ± 3.6, respectively, p < 0.05). A principal component analysis and hierarchical clustering of the AMR gene data showed the extensive use farm samples were disparate from the limited and no antimicrobial use farms. The prevalence of resistance genes in extensive use farms was significantly higher than the other farm categories for 18 resistance genes including bla SHV, bla CTX-M1 group, bla CTX-M9 group, bla VEB, bla CMY2-LAT, aac(6')-lb-cr, qnrB1, gyrA83L-E. coli, armA, rmtB, aac(3)-IIa, mphA, 23S rRNA 2075G-Campylobacter spp., mcr-1, catA1, floR, dfrA5-14, and dfrA17. These genotypic findings were supported by phenotypic susceptibility results on fecal E. coli isolates. To examine the timing of AMR gene abundance in swine farms, we also performed a longitudinal study in pigs. The results showed that AMR prevalence occurred both early, presumably from mothers, as well as after weaning, presumably from the environment. In summary, detection of AMR genes directly in fecal samples can be used to qualitatively and quantitatively monitor AMR in swine farms.

Characterization of Antibiotic-Susceptibility Patterns, Virulence Factor Profiles and Clonal Relatedness in Proteus mirabilis Isolates from Patients with Urinary Tract Infection in Iran

Purpose

Proteus mirabilis is one of the most important agents of urinary tract infection (UTI). As there are limited data abou the pathogenicity P. mirabilis isolated from Iran, we investigated the virulence characteristics and antibiotic resistance in the isolates. Finally, the genotypic patterns were evaluated by Pulse field gel electrophoresis (PFGE).

Methods

A total of 110 isolates of P. mirabilis causing UTIs were isolated from patients in Tehran, Iran. The virulence characteristics and antimicrobial susceptibility were assayed using phenotypic methods. Extended-spectrum β-lactamases (ESBLs) production was assayed by the combination disk diffusion test (CDDT). Presence of virulence genes and antimicrobial-resistant genes was detected by Polymerase chain reaction (PCR). Finally, thirty-three isolates were selected for PFGE.

Results

All isolates showed the ability of biofilm and hemolysin formation. Antibiotic resistance ranged from 59.1% about cotrimoxazole to 2.7% about amoxicillin-clavulanic acid. Sixteen (14.5%) of the isolates were classified as multi-drug resistant (MDR). All isolates amplified mrpH, mrpA, pmfA, ureG and hpmA genes. Furthermore, the prevalence of zapA, fliC, ptaA, and ucaA genes was 98.2%, 98.2%, 95.5%, and 95.5%, respectively. The prevalence of plasmid-mediated quinolone resistance (PMQR) genes was 4.5% and 0.9% for aac(6')-Ib-cr and qnrA, respectively. Twenty-eight pulsotypes were detected among the 33 isolates by PFGE that pulsotypes 1, 2 and 4 with two isolates and pulsotype 3 with three isolates were the most prevalent ones.

Conclusion

It was found that the P. mirabilis isolates had high frequency of virulence factors. In addition, antibiotic resistance to some antibiotics and also production of ESBLs is alarming and shows the need for hygienic procedures to prevent the dissemination of antibiotic resistance. Although PFGE showed genetic diversity among the isolates, finding of several pulsotypes among the isolates should be considered an alarm to prevent these infections in hospital environments.

A Rare Opportunist, Morganella morganii, Decreases Severity of Polymicrobial Catheter-Associated Urinary Tract Infection

Catheter-associated urinary tract infections (CAUTIs) are common hospital-acquired infections and frequently polymicrobial, which complicates effective treatment. However, few studies experimentally address the consequences of polymicrobial interactions within the urinary tract, and the clinical significance of polymicrobial bacteriuria is not fully understood. Proteus mirabilis is one of the most common causes of monomicrobial and polymicrobial CAUTI and frequently cocolonizes with Enterococcus faecalis, Escherichia coli, Providencia stuartii, and Morganella morganiiP. mirabilis infections are particularly challenging due to its potent urease enzyme, which facilitates formation of struvite crystals, catheter encrustation, blockage, and formation of urinary stones. We previously determined that interactions between P. mirabilis and other uropathogens can enhance P. mirabilis urease activity, resulting in greater disease severity during experimental polymicrobial infection. Our present work reveals that M. morganii acts on P. mirabilis in a contact-independent manner to decrease urease activity. Furthermore, M. morganii actively prevents urease enhancement by E. faecalis, P. stuartii, and E. coli Importantly, these interactions translate to modulation of disease severity during experimental CAUTI, predominantly through a urease-dependent mechanism. Thus, products secreted by multiple bacterial species in the milieu of the catheterized urinary tract can directly impact prognosis.

Extended-spectrum β-lactamase-producing Proteus mirabilis with multidrug resistance isolated from raw chicken in Singapore: Genotypic and phenotypic analysis

OBJECTIVES

Proteus mirabilis is ubiquitous in soil and water. It is an important catheter-associated urinary tract pathogen and has reportedly been associated with antimicrobial-resistant infections. This study reports the draft genome of a multidrug-resistant P. mirabilis isolated from raw retail chicken meat in Singapore.

METHODS

The P. mirabilis strain was isolated on Brilliance^TM ESBL Agar and was screened for antimicrobial susceptibility against 29 antimicrobial agents using a MicroScan® Neg MIC Panel Type 44. The double-disk synergy test (DDST) was used for confirmation of extended-spectrum β-lactamase (ESBL) production. Genomic DNA from the pure culture isolate was extracted and was sent for sequencing based on Illumina HiSeq 2500 technology. Further bioinformatics analysis was performed using online tools available at the Center for Genomic Epidemiology.

RESULTS

Species identification of the isolate was performed by KmerFinder. Antimicrobial susceptibility testing of the isolate showed multidrug resistance to broad-spectrum β-lactams, fluoroquinolones and aminoglycosides, among others. ESBL production was confirmed by the DDST. A total of 29 antimicrobial resistance genes were detected by ResFinder.

CONCLUSION

To the best of our knowledge, this is the first report of the whole-genome sequence of a multidrug-resistant P. mirabilis producing an ESBL from raw chicken meat in Singapore. This indicates that raw meat in Singapore can be a reservoir for drug-resistant pathogens.

Primary and Secondary Bacteremia Caused by Proteus spp.: Epidemiology, Strains Susceptibility and Biofilm Formation

Proteus spp. is an etiological factor of urinary tract and bloodstream infections. The aim of this study was the retrospective analysis of susceptibility of Proteus spp. strains isolated from bloodstream infections (BSIs) as well as similarity evaluation of the strains isolated from different clinical samples. Proteus spp. strains were isolated in 2009-2017 from hospital patients. Identification was based on the colony's morphology and biochemical or MALDI-TOF MS analyzes. The antibiotic susceptibility test was done using the diffusion method. Biofilm formation was evaluated with microplate method using TTC. Bacteremia caused by Proteus spp. was found in 97 patients, mainly secondary to urinary tract infection. Most of the strains were susceptible to piperacillin with tazobactam (95.9%) and amikacin (86.7%). Elderly patients have a higher risk of mortality after BSIs caused by Proteus spp. A detailed analysis was made for randomly chosen 26 strains isolated from 11 patients with Proteus mirabilis bacteremia. Using PFGE, we found that 10 (90.9%) isolates, collected from different clinical specimens of the same patient, were genetically identical.

Proteus spp. is an etiological factor of urinary tract and bloodstream infections. The aim of this study was the retrospective analysis of susceptibility of Proteus spp. strains isolated from bloodstream infections (BSIs) as well as similarity evaluation of the strains isolated from different clinical samples. Proteus spp. strains were isolated in 2009–2017 from hospital patients. Identification was based on the colony’s morphology and biochemical or MALDI-TOF MS analyzes. The antibiotic susceptibility test was done using the diffusion method. Biofilm formation was evaluated with microplate method using TTC. Bacteremia caused by Proteus spp. was found in 97 patients, mainly secondary to urinary tract infection. Most of the strains were susceptible to piperacillin with tazobactam (95.9%) and amikacin (86.7%). Elderly patients have a higher risk of mortality after BSIs caused by Proteus spp. A detailed analysis was made for randomly chosen 26 strains isolated from 11 patients with Proteus mirabilis bacteremia. Using PFGE, we found that 10 (90.9%) isolates, collected from different clinical specimens of the same patient, were genetically identical.

Polymorphisms of Gene Cassette Promoters of the Class 1 Integron in Clinical Proteus Isolates

OBJECTIVE

To describe the polymorphisms of gene cassette promoters of the class 1 integron in clinical Proteus isolates and their relationship with antibiotic resistance.

METHODS

Polymorphisms of the gene cassette promoter in 153 strains of Proteus were analyzed by PCR and nucleotide sequencing. Variable regions of atypical class 1 integrons were detected by inverse PCR and nucleotide sequencing. Enterobacterial repetitive intergenic consensus (ERIC)-PCR was used to analyze the phylogenetic relationships of class 1 integron-positive clinical Proteus isolates. Representative beta-lactamase genes (bla), including bla TEM,bla SHV,bla CTX-M-1,bla CTX-M-2,bla CTX-M-8,bla CTX-M-9,bla CTX-M-25 and bla OXA-1, and plasmid-mediated quinolone resistance (PMQR) genes including qnrA, qnrB, qnrC, qnrD, qnrS, oqxA, oqxB, qepA, and aac(6')-Ib were also screened using PCR and sequence analysis.

RESULTS

Fifteen different gene cassette arrays and 20 different gene cassettes were detected in integron-positive strains. Of them, aadB-aadA2 (37/96) was the most common gene cassette array. Two of these gene cassette arrays (estX-psp-aadA2-cmlA1, estX-psp-aadA2-cmlA1-aadA1a-qacI-tnpA-sul3) have not previously been reported. Three different Pc-P2 variants (PcS, PcWTGN-10, PcH1) were detected among the 96 Proteus strains, with PcH1 being the most common (49/96). Strains carrying the promoters PcS or PcWTGN-10 were more resistant to sulfamethoxazole, gentamicin and tobramycin than those carrying PcH1. Strains with weak promoter (PcH1) harbored significantly more intra- and extra-integron antibiotic resistance genes than isolates with strong promoter (PcWTGN-10). Further, among 153 isolates, representative beta-lactamase genes were detected in 70 isolates (bla TEM-1, 54; bla OXA-1, 40; bla CTX-M-3, 12; bla CTX-M-14, 12; bla CTX-M-65, 5; bla CTX-M-15, 2) and representative PMQR genes were detected in 87 isolates (qnrA, 6; qnrB, 3; qnrC, 5; qnrD, 46; qnrS, 5; oqxA, 7; aac(6')-Ib, 13; aac(6')-Ib-cr, 32).

CONCLUSION

To the best of our knowledge, this study provides the first evidence for polymorphisms of the class 1 integron variable promoter in clinical Proteus isolates, which generally contain relatively strong promoters. Resistance genotypes showed a higher coincidence rate with the drug-resistant phenotype in strong-promoter-containing strains, resulting in an ability to confer strong resistance to antibiotics among host bacteria and a relatively limited ability to capture gene cassettes. Moreover, strains with relatively weak integron promoters can "afford" a heavier "extra-integron antibiotic resistance gene load". Furthermore, the gene cassettes estX, psp and the gene cassette arrays estX-psp-aadA2-cmlA1, estX-psp-aadA2-cmlA1-aadA1a-qacI-tnpA-sul3 have been confirmed for the first time in clinical Proteus isolates. Beta-lactamase genes and PMQR were investigated, and bla TEM-1 and bla OXA-1 were the most common, with qnrD and aac (6')-Ib-cr also being dominant.

Twin arginine translocation, ammonia incorporation, and polyamine biosynthesis are crucial for Proteus mirabilis fitness during bloodstream infection

The Gram-negative bacterium Proteus mirabilis is a common cause of catheter-associated urinary tract infections (CAUTI), which can progress to secondary bacteremia. While numerous studies have investigated experimental infection with P. mirabilis in the urinary tract, little is known about pathogenesis in the bloodstream. This study identifies the genes that are important for survival in the bloodstream using a whole-genome transposon insertion-site sequencing (Tn-Seq) approach. A library of 50,000 transposon mutants was utilized to assess the relative contribution of each non-essential gene in the P. mirabilis HI4320 genome to fitness in the livers and spleens of mice at 24 hours following tail vein inoculation compared to growth in RPMI, heat-inactivated (HI) naïve serum, and HI acute phase serum. 138 genes were identified as ex vivo fitness factors in serum, which were primarily involved in amino acid transport and metabolism, and 143 genes were identified as infection-specific in vivo fitness factors for both spleen and liver colonization. Infection-specific fitness factors included genes involved in twin arginine translocation, ammonia incorporation, and polyamine biosynthesis. Mutants in sixteen genes were constructed to validate both the ex vivo and in vivo results of the transposon screen, and 12/16 (75%) exhibited the predicted phenotype. Our studies indicate a role for the twin arginine translocation (tatAC) system in motility, translocation of potential virulence factors, and fitness within the bloodstream. We also demonstrate the interplay between two nitrogen assimilation pathways in the bloodstream, providing evidence that the GS-GOGAT system may be preferentially utilized. Furthermore, we show that a dual-function arginine decarboxylase (speA) is important for fitness within the bloodstream due to its role in putrescine biosynthesis rather than its contribution to maintenance of membrane potential. This study therefore provides insight into pathways needed for fitness within the bloodstream, which may guide strategies to reduce bacteremia-associated mortality.