The assessment of Proteus mirabilis susceptibility to ceftazidime and ciprofloxacin and the impact of these antibiotics at subinhibitory concentrations on Proteus mirabilis biofilms

Potential antivirulence activity of sub-inhibitory concentrations of ciprofloxacin against Proteus mirabilis isolates: an in-vitro and in-vivo study

BACKGROUND

Proteus mirabilis is a significant nosocomial pathogen that is frequently associated with a wide range of infections, necessitating heightened attention to mitigate potential health risks. Hence, this study was performed to investigate the impact of sub-minimum inhibitory concentrations (MICs) of ciprofloxacin (CIP) on Proteus mirabilis clinical isolates.

METHODS

The sub-MICs of CIP were selected using the growth curve approach. The untreated and treated isolates with sub-MICs of CIP were assessed for their biofilm development, motilities on agar, and other virulence factors. The cell morphology of untreated and treated isolates with sub-MIC of CIP was explored using electron microscope. Moreover, the expression levels of the virulence genes in isolates were measured using quantitative real-time PCR.

RESULTS

Data revealed that sub-MICs of CIP significantly (p < 0.05), in a concentration-dependent manner, inhibited biofilm formation and other virulence factors in the selected isolates. Electron microscope analysis showed cell enlargement and various abnormalities in the cell wall and membrane integrity.

CONCLUSION

Sub-MICs of CIP exhibited inhibition of virulence and alterations in morphological integrity against P. mirabilis isolates.

Antibiotic resistance and virulence profiles of Proteus mirabilis isolated from broiler chickens at abattoir in South Africa

BACKGROUND

Proteus mirabilis has been identified as an important zoonotic pathogen, causing several illnesses such as diarrhoea, keratitis and urinary tract infections.

OBJECTIVE

This study assessed the prevalence of P. mirabilis in broiler chickens, its antibiotic resistance (AR) patterns, ESBL-producing P. mirabilis and the presence of virulence genes.

METHODS

A total of 26 isolates were confirmed as P. mirabilis from 480 pooled broiler chicken faecal samples by polymerase chain reaction (PCR). The disk diffusion method was used to evaluate the antibacterial susceptibility test, while nine virulence genes and 26 AR genes were also screened by PCR.

RESULTS

All 26 P. mirabilis isolates harboured the ireA (siderophore receptors), ptA, and zapA (proteases), ucaA, pmfA, atfA, and mrpA (fimbriae), hlyA and hpmA (haemolysins) virulence genes. The P. mirabilis isolates were resistant to ciprofloxacin (62%) and levofloxacin (54%), while 8 (30.7%) of the isolates were classified as multidrug resistant (MDR). PCR analysis identified the blaCTX-M gene (62%), blaTEM (58%) and blaCTX-M-2 (38%). Further screening for AMR genes identified mcr-1, cat1, cat2, qnrA, qnrD and mecA, 12%, 19%, 12%, 54%, 27% and 8%, respectively for P. mirabilis isolates. The prevalence of the integron integrase intI1 and intI2 genes was 43% and 4%, respectively.

CONCLUSIONS

The rise of ciprofloxacin and levofloxacin resistance, as well as MDR strains, is a public health threat that points to a challenge in the treatment of infections caused by these zoonotic bacteria. Furthermore, because ESBL-producing P. mirabilis has the potential to spread to humans, the presence of blaCTX -M -producing P. mirabilis in broilers should be kept under control. This is the first study undertaken to isolate P. mirabilis from chicken faecal samples and investigate its antibiotic resistance status as well as virulence profiles in South Africa.

Characterization of Potential Virulence, Resistance to Antibiotics and Heavy Metals, and Biofilm-Forming Capabilities of Soil Lignocellulolytic Bacteria

Soil bacteria participate in self-immobilization processes for survival, persistence, and production of virulence factors in some niches or hosts through their capacities for autoaggregation, cell surface hydrophobicity, biofilm formation, and antibiotic and heavy metal resistance. This study investigated potential virulence, antibiotic and heavy metal resistance, solvent adhesion, and biofilm-forming capabilities of six cellulolytic bacteria isolated from soil samples: Paenarthrobacter sp. MKAL1, Hymenobacter sp. MKAL2, Mycobacterium sp. MKAL3, Stenotrophomonas sp. MKAL4, Chryseobacterium sp. MKAL5, and Bacillus sp. MKAL6. Strains were subjected to phenotypic methods, including heavy metal and antibiotic susceptibility and virulence factors (protease, lipase, capsule production, autoaggregation, hydrophobicity, and biofilm formation). The effect of ciprofloxacin was also investigated on bacterial susceptibility over time, cell membrane, and biofilm formation. Strains MKAL2, MKAL5, and MKAL6 exhibited protease and lipase activities, while only MKAL6 produced capsules. All strains were capable of aggregating, forming biofilm, and adhering to solvents. Strains tolerated high amounts of chromium, lead, zinc, nickel, and manganese and were resistant to lincomycin. Ciprofloxacin exhibited bactericidal activity against these strains. Although the phenotypic evaluation of virulence factors of bacteria can indicate their pathogenic nature, an in-depth genetic study of virulence, antibiotic and heavy metal resistance genes is required.

Organic Acids Secreted by Lactobacillus spp. Isolated from Urine and Their Antimicrobial Activity against Uropathogenic Proteus mirabilis

The natural microbiota of the urinary tract includes Lactobacillus spp., which secrete molecules with antimicrobial properties and have antagonistic activity against many pathogens. This paper focuses on the antibacterial effect of Lactobacillus strains isolated from urine against clinical strains of Proteus mirabilis isolated from kidney stones and from urine with coexisting urolithiasis. The study involved analyzing the main antimicrobial molecules secreted by Lactobacillus. In order to indicate which agent had the strongest antimicrobial effect, the supernatants were made alkaline and treated with catalase and high temperature. Both treated and untreated supernatants were analyzed for their activity. Exposing uropathogens to all untreated cell-free supernatants of Lactobacillus significantly reduced their growth, and it was established that these properties were related to organic acid secretion by these strains. Using LC–MS/MS and spectrophotometric techniques, lactic, citric, and succinic acids were determined qualitatively and quantitatively. The influence of these acids on the P. mirabilis growth and biofilm formation and their influence on membrane permeability were also investigated. The results indicate that organic acids secreted by Lactobacillus strains have a high antibacterial potential and could be used as novel agents in the treatment of urinary tract infections caused by P. mirabilis.

DNA Gyrase and Topoisomerase IV Mutations and their effect on Quinolones Resistant Proteus mirabilis among UTIs Patients

Objective:

This study aimed to highlight the importance of mutations within Proteus mirabilis genome that are related to fluoroquinolone resistance.

Methods:

This is a cross sectional study performed in different teaching hospitals in Khartoum State from June 2016 to May 2017. A total of (120) P mirabilis isolates from patients with symptoms of UTIs attending different hospitals in Khartoum State were examined. First, modified Kurby Bauer method was performed for phenotypical detection of resistant isolates. Then polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) followed by sequencing were applied for detection of mutations in GyrA, GyrB, ParC and ParE genes of isolates.

Results:

P. mirabilis showed 30% resistance to ciprofloxacin. All samples revealed mutation at (serine 83) of GyrA and (serine 84) of ParC by Hinf1 restriction endonuclease digestion. Sequencing was performed for 12 samples. For each gene, two resistant and one susceptible strains were randomly selected. The mutations associated with ciprofloxacin resistant P. mirabilis were as follows; (1/3) GyrA (Ser 83 to Ile) and (2/3) ParC (Ser 81 to Ile). Also it revealed silent mutations at codons of GyrB 474 leucine (3/3), 585 valine (2/3), 612 histidine (1/3) and 639 asparagine (1/3) and ParE 469 isoleucine (2/3), 531 aspartic (2/3) and 533 glycine (1/3).

Conclusions:

Ciprofloxacin resistance in P. mirabilis could be monitored through detection of mutations within DNA gyrase (encoded by gyrA and gyrB) and topoisomerase IV (encoded by parC and parE).

Proteus mirabilis Biofilm: Development and Therapeutic Strategies

Proteus mirabilis is a Gram negative bacterium that is a frequent cause of catheter-associated urinary tract infections (CAUTIs). Its ability to cause such infections is mostly related to the formation of biofilms on catheter surfaces. In order to form biofilms, P. mirabilis expresses a number of virulence factors. Such factors may include adhesion proteins, quorum sensing molecules, lipopolysaccharides, efflux pumps, and urease enzyme. A unique feature of P. mirabilis biofilms that build up on catheter surfaces is their crystalline nature owing to their ureolytic biomineralization. This leads to catheter encrustation and blockage and, in most cases, is accompanied by urine retention and ascending UTIs. Bacteria embedded in crystalline biofilms become highly resistant to conventional antimicrobials as well as the immune system. Being refractory to antimicrobial treatment, alternative approaches for eradicating P. mirabilis biofilms have been sought by many studies. The current review focuses on the mechanism by which P. mirabilis biofilms are formed, and a state of the art update on preventing biofilm formation and reduction of mature biofilms. These treatment approaches include natural, and synthetic compounds targeting virulence factors and quorum sensing, beside other strategies that include carrier-mediated diffusion of antimicrobials into biofilm matrix. Bacteriophage therapy has also shown successful results in vitro for combating P. mirabilis biofilms either merely through their lytic effect or by acting as facilitators for antimicrobials diffusion.

Antimicrobial and Antibiofilm Activities of Probiotic Lactobacilli on Antibiotic-Resistant Proteus mirabilis

The emergence of biofilm-forming, multi-drug-resistant (MDR) Proteus mirabilis infections is a serious threat that necessitates non-antibiotic therapies. Antibiotic susceptibility and biofilm-forming activity of P. mirabilis isolates from urine samples were assessed by disc diffusion and crystal violet assays, respectively. Antimicrobial activities of probiotic Lactobacilli were evaluated by agar diffusion. Antibiofilm and anti-adherence activities were evaluated by crystal violet assays. While most P. mirabilis isolates were antibiotic-resistant to varying degrees, isolate P14 was MDR (resistant to ceftazidime, cefotaxime, amoxicillin-clavulanic acid, imipenem, ciprofloxacin, and amikacin) and formed strong biofilms. Cultures and cell-free supernatants of Lactobacillus casei and Lactobacillus reuteri exhibited antimicrobial and antibiofilm activities. The 1/16 concentration of untreated supernatants of L. casei and L. reuteri significantly reduced mature biofilm formation and adherence of P14 by 60% and 72%, respectively (for L. casei), and by 73% each (for L. reuteri). The 1/8 concentration of pH-adjusted supernatants of L. casei and L. reuteri significantly reduced mature biofilm formation and adherence of P14 by 39% and 75%, respectively (for L. casei), and by 73% each (for L. reuteri). Scanning electron microscopy (SEM) confirmed eradication of P14’s biofilm by L. casei. L. casei and L. reuteri could be utilized to combat Proteus-associated urinary tract infections.

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.

Sub-minimum inhibitory concentration ceftazidime inhibits Escherichia coli biofilm formation by influencing the levels of the ibpA gene and extracellular indole

Escherichia coli is a common pathogen of bacterial biofilm infections. Sub-minimum inhibitory concentration ceftazidime (sub-MIC CAZ) could inhibit the biofilm formation of E. coli. Deletion of the ibpAB genes could increase the extracellular indole concentration of E. coli and then inhibit biofilm formation. Therefore, we speculated that sub-MIC CAZ might inhibit biofilm formation via ibpAB. In this study, the results showed that sub-MIC CAZ could significantly inhibit biofilm formation, swimming motility and the expression of the ibpA gene, while it could increase the expression of tnaA gene and extracellular indole concentration. Knockout of the ibpA gene resulted in a decrease in biofilm formation and swimming motility and an increase in the indole concentration. When treated with sub-MIC CAZ, the tnaA gene expression, indole concentration, biofilm formation and swimming motility of MG1655 ΔibpA were similar to those of the control group. The results indicated that sub-MIC CAZ might inhibit the biofilm formation of E. coli by increasing the extracellular indole concentration and downregulating the ibpA gene.

Vitamin C in the Presence of Sub-Inhibitory Concentration of Aminoglycosides and Fluoroquinolones Alters Proteus mirabilis Biofilm Inhibitory Rate

Vitamin C has antimicrobial activity and is often used as an oral supplement accompanying antibiotic treatment in urinary tract infections (UTI). Proteus mirabilis is the third common species responsible for UTIs that are mostly treated with fluoroquinolones or aminoglycosides. Treatment of the UTI caused by P. mirabilis is problematic due to the ability to form biofilm on the urinary catheters. The aim of the study was to evaluate the influence of ascorbic acid in combination with antibiotics on P. mirabilis abilities to form biofilm. The susceptibility of P. mirabilis reference strain ATCC^® 29906™ and four clinical strains isolated from the urine samples of patients with urinary catheter were evaluated according to EUCAST recommendations. The influence of ascorbic acid (0.4 mg × mL⁻¹) in combination with antibiotics on biofilm formation was evaluated spectrophotometrically. Aminoglycosides at sub-inhibitory concentrations more successfully limited biofilm formation by P. mirabilis strains without ascorbic acid addition. Inhibition rate differences at the lowest concentrations of gentamicin and amikacin were statistically significant (p ≤ 0.05). Ascorbic acid addition to the culture medium limited the inhibitory effect of fluoroquinolones, facilitating biofilm formation by P. mirabilis strains. The addition of ascorbic acid during aminoglycosides therapy may disturb treatment of urinary tract infections related to the presence of P. mirabilis biofilm.

Peer pressure from a Proteus mirabilis self-recognition system controls participation in cooperative swarm motility

Colonies of the opportunistic pathogen Proteus mirabilis can distinguish self from non-self: in swarming colonies of two different strains, one strain excludes the other from the expanding colony edge. Predominant models characterize bacterial kin discrimination as immediate antagonism towards non-kin cells, typically through delivery of toxin effector molecules from one cell into its neighbor. Upon effector delivery, receiving cells must either neutralize it by presenting a cognate anti-toxin as would a clonal sibling, or suffer cell death or irreversible growth inhibition as would a non-kin cell. Here we expand this paradigm to explain the non-lethal Ids self-recognition system, which stops access to a social behavior in P. mirabilis by selectively and transiently inducing non-self cells into a growth-arrested lifestyle incompatible with cooperative swarming. This state is characterized by reduced expression of genes associated with protein synthesis, virulence, and motility, and also causes non-self cells to tolerate previously lethal concentrations of antibiotics. We show that temporary activation of the stringent response is necessary for entry into this state, ultimately resulting in the iterative exclusion of non-self cells as a swarm colony migrates outwards. These data clarify the intricate connection between non-lethal recognition and the lifecycle of P. mirabilis swarm colonies.

A resident of animal intestines, Proteus mirabilis is a major cause of catheter-associated urinary tract infections and can cause recurrent, persistent infections. Swarming, which is a collective behavior that promotes centimeter-scale population migration, is implicated in colonization of bladders and kidneys. A regulatory factor of swarming is kin recognition, which involves the transfer of a self-identity protein from one cell into a physically adjacent neighboring cell. However, how kin recognition regulates swarming was previously unclear. We have now shown a mechanism linking kin recognition, swarm migration, and antibiotics tolerance: cells induce a transient antibiotics-tolerant, persister-like state in adjacent non-identical cells which in turn prevents non-identical cells from continuing to participate in collective swarming. These affected non-identical cells continue to exhibit large-scale gene expression suggesting an active shift into a different expression state. These data provide two key insights for the field. First, kin recognition can be a regulatory mechanism that acts with spatial and temporal precision. Second, induction into an antibiotics-tolerant state, instead of occurring stochastically, can be physically and spatially regulated by neighboring cells. These insights highlight the importance of further developing four-dimensional (time and X-, Y-, Z-axes) model systems for interrogating cell-cell signaling and control in microbial populations.

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.

The Ciprofloxacin Impact on Biofilm Formation by Proteus Mirabilis and P. Vulgaris Strains

BACKGROUND

Proteus spp. bacilli belong to opportunistic human pathogens, which are primarily responsible for urinary tract and wound infections. An important virulence factor is their ability to form biofilms that greatly reduce the effectiveness of antibiotics in the site of infection.

OBJECTIVES

The aim of this study was to determine the value of the minimum concentration of ciprofloxacin that eradicates a biofilm of Proteus spp. strains.

MATERIALS AND METHODS

A biofilm formation of 20 strains of P. mirabilis and 20 strains of P. vulgaris were evaluated by a spectrophotometric method using 0.1% 2, 3, 5-Triphenyl-tetrazolium chloride solution (TTC, AVANTORTM). On the basis of the results of the absorbance of the formazan, a degree of reduction of biofilm and minimum biofilm eradication (MBE) values of MBE50 and MBE90 were determined.

RESULTS

All tested strains formed a biofilm. A value of 1.0 μg/mL ciprofloxacin is MBE50 for the strains of both tested species. An MBE90 value of ciprofloxacin for isolates of P. vulgaris was 2 μg/mL and for P. mirabilis was 512 μg/mL.

CONCLUSIONS

Minimum biofilm eradication values of ciprofloxacin obtained in the study are close to the values of the minimal inhibition concentration (MIC).

Antibiotic-Resistant Bacteria Are Major Threats of Otitis Media in Wollo Area, Northeastern Ethiopia: A Ten-Year Retrospective Analysis

Antibiotic resistance is an increasingly serious threat to human health that needs an urgent action. The aim of this study was to determine the prevalence and antibiotic susceptibility profiles of bacteria isolated from patient ear discharges suspected of otitis media. A retrospective analysis was performed using culture and antibiotic susceptibility test results of 1225 patients who visited Dessie Regional Health Research Laboratory from 2001 to 2011. Results showed a strong association (P < 0.001) between age and the risk of acquiring middle ear infection. The predominant bacterial isolates were Proteus spp. (28.8%), Staphylococcus aureus (23.7%), and Pseudomonas spp. (17.2%). Most of the isolated bacteria showed high resistance to ampicillin (88.5%), ceftriaxone (84.5%), amoxicillin (81.9%), and tetracycline (74.5%). About 72.5% of Proteus spp. and 62.2% of Pseudomonas spp. have developed resistance to one and more antibiotics used to treat them. This retrospective study also revealed the overall antibiotic resistance rate of bacterial isolates was increased nearly twofold (P = 0.001) over the last decade. Relatively, ciprofloxacin and gentamicin were the most effective antibiotics against all the isolates. In conclusion, antibiotic-resistant bacteria are alarmingly increasing in Wollo area, northeastern Ethiopia, and becoming a major public health problem in the management of patients with middle ear infection.