Susceptibility of Escherichia coli isolated from uteri of postpartum dairy cows to antibiotic and environmental bacteriophages. Part I: Isolation and lytic activity estimation of bacteriophages

Application of bacteriophage as food preservative to control enteropathogenic Escherichia coli (EPEC)

Objectives

This study was conducted to characterize lytic bacteriophages infecting enteropathogenic Escherichia coli (EPEC) on several types of food and analyze their ability as phage biocontrol to be used as a food preservative. Characterization was done for bacteriophage morphology and stability, along with the determination of minimum multiplicity of infection (miMOI), and application of bacteriophage in the food matrix.

Results

Out of the five samples, BL EPEC bacteriophage exhibited the highest titer of 2.05  ×  10⁹ PFU/mL, with a wide range of pH tolerance, and high thermal tolerance. BL EPEC also showed the least reduction after 168 h of incubation, with a rate of 0.90  ×  10^–3 log₁₀ per hour. Bacteriophages from BL EPEC and CS EPEC showed an ideal value of miMOI of 0.01. As a food preservative, BL EPEC bacteriophage was able to reduce bacteria in food samples with a reduction above 0.24 log₁₀ in lettuce and approximately 1.84 log₁₀ in milk. From this study we found that BL EPEC bacteriophage showed the greatest potential to be used as phage biocontrol to improve food safety

Evidence-Based Tracking of MDR E. coli from Bovine Endometritis and Its Elimination by Effective Novel Therapeutics

Antibiotic-resistant bacteria have become the predominant etiology of endometritis and thus require effective treatment approaches. We used ultrasonography coupled with clinical signs and presented complaints of reproductive issues to investigate the epidemiology, phylogenetic analysis, antimicrobial resistance, and development of novel therapeutics against Escherichia coli isolated from endometritis in bovine (n = 304 from 10 commercial dairy farms). The prevalence of bovine endometritis in this study was 43.75%, while among these, 72.18% samples were positive for E. coli. Nucleotide analysis performed through BLAST and MEGAX showed 98% similarity to the nucleotide sequence of the reference E. coli strain (accession number CP067311.1). The disk diffusion assay revealed pathogen resistance to most antibiotics. Pattern of MIC order of resistance was as follows: enrofloxacin < gentamicin < co-amoxiclav < streptomycin < amoxicillin < metronidazole < oxytetracycline. Field trials revealed the highest recovery rate (in terms of clearance of endometritis and establishment of pregnancy) in case of gentamicin + enrofloxacin (100%) and gentamicin alone (100%), followed by co-amoxiclav + gentamicin (84.61%), oxytetracycline alone (78.57%), and metronidazole + enrofloxacin (33.33%). Hence, the current study reported a higher prevalence of multidrug-resistant E. coli showing considerable similarity with reference strain, and finally, the effective response of novel antibiotics to treat cases.

Application of the Resazurin Cell Viability Assay to Monitor Escherichia coli and Salmonella Typhimurium Inactivation Mediated by Phages

Bacterial inactivation using bacteriophages (or phages) has emerged as an effective solution for bacterial infections, but the screening methods used to evaluate the effectiveness of the phages to inactivate bacteria are not fast, reliable or precise enough. The efficiency of bacterial inactivation by phages has been evaluated by monitoring bacterial concentration either by counting colony-forming units (CFU), a laborious and time-consuming method, or by monitoring the optical density (OD), a less sensitive method. In this study, the resazurin cell viability assay was used to monitor the viability of bacteria from different genera during the inactivation by different phages, and the results were compared with the standard methods used to assess bacterial inactivation. The results showed that the resazurin colorimetric cell viability assay produces similar results to the standard method of colony-counting and giving, and also more sensitive results than the OD method. The resazurin assay can be used to quickly obtain the results of the cell viability effect profile using two different bacterial strains and several different phages at the same time, which is extremely valuable in screening studies. Moreover, this methodology is established as an effective, accurate and rapid method when compared to the ones widely used to monitor bacterial inactivation mediated by phages.

Recent advances and future directions for uterine diseases diagnosis, pathogenesis, and management in dairy cows

Researchers, veterinarians, and farmers' pursuit of a consistent diagnosis, treatment, and prevention of uterine diseases remains challenging. The diagnosis and treatment of metritis is inconsistent, a concerning situation when considered the global threat of antimicrobial resistance dissemination. Endometritis is an insidious disease absent on routine health programs in many dairy farms and from pharmaceutical therapeutics arsenal in places like the US market. Conversely, a multitude of studies advanced the understanding of how uterine diseases compromise oocyte, follicle, and embryo development, and the uterine environment having long-lasting effects on fertility. The field of uterine disease microbiome also experienced tremendous progress and created opportunities for the development of novel preventives to improve the management of uterine diseases. Activity monitors, biomarkers, genomic selection, and machine learning predictive models are other innovative developments that have been explored in recent years to help mitigate the negative impacts of uterine diseases. Albeit novel tools such as vaccines for metritis, immune modulators, probiotics, genomic selection, and selective antimicrobial therapy are promising, further research is warranted to implement these technologies in a systematic and cost-effective manner.

Bacteriophages and associated endolysins in therapy and prevention of mastitis and metritis in cows: Current knowledge

Bacteriophages and the associated endolysins have been proposed as an alternative to antibiotic treatment of mastitis and metritis in cows. Many bacteriophages have been isolated and characterized with a large amount of lytic potential against the bacteria causing mastitis and metritis in cows. Several endolysins with marked lytic activity against mastitis pathogens in vitro were also produced from staphylococcal and streptococcal bacteriophages. In the few clinical studies, however, there has been marginal efficacy of bacteriophages in the therapy of mastitis caused by Staphylococcus aureus. Similarly, lytic bacteriophages have marked antimicrobial activity in vitro against E. coli strains from the uteri of postpartum dairy cows. In clinical studies, however, neither administration of bacteriophages early postpartum nor prepartum was effective in the prevention of metritis in cows. More clinical studies on the effectiveness of bacteriophages and the associated endolysins in the prevention and therapy of mastitis and metritis in cows, therefore, are needed.

Isolation and characterization of pathogenic Escherichia coli bacteriophages from chicken and beef offal

OBJECTIVE

This study was conducted to isolate and characterize lytic bacteriophages for pathogenic Escherichia coli from chicken and beef offal, and analyze their capability as biocontrol for several foodborne pathogens. Methods done in this research are bacteriophage isolation, purification, titer determination, application, determination of host range and minimum multiplicity of infection (miMOI), and bacteriophage morphology.

RESULTS

Six bacteriophages successfully isolated from chicken and beef offal using EPEC and EHEC as host strain. Bacteriophage titers observed between 10⁹ and 10¹⁰ PFU mL^-1. CS EPEC and BL EHEC bacteriophage showed high efficiency in reduction of EPEC or EHEC contamination in meat about 99.20% and 99.04%. The lowest miMOI was 0.01 showed by CS EPEC bacteriophage. CI EPEC and BL EPEC bacteriophage suspected as Myoviridae family based on its micrograph from Transmission Electron Microscopy (TEM). Refers to their activity, bacteriophages isolated in this study have a great potential to be used as biocontrol against several foodborne pathogens.

Effects of hypertonic dextrose and paraffin solution as non-antibiotic treatments of clinical endometritis on reproductive performance of high producing dairy cows

The objective of this study was to compare the reproductive performance of cows affected by clinical endometritis (CE) following treatment with an intrauterine infusion of 50% dextrose solutions (DEX) and liquid paraffin (LP) as alternative therapies with routine treatments including PGF2α injection and intrauterine infusion of oxytetracycline (OTC). Moreover, the reproductive indices of cows treated with endometritis were compared with those of healthy ones. At postpartum reproductive tract examination (28-35 DIM) in one Iranian dairy farm, cows with CE without any selection were assigned to four groups: (a) OTC, a common treatment in Iran, was administered (5 g) to 396 cows, (b) PGF2 α (PG) was injected to 496 cows, (c) dextrose solution (DEX): intrauterine infusion of 50% dextrose solution (200 ml) was done in 427 cows, and (d) liquid paraffin (LP) was administered (100 ml) to 423 cows via intrauterine route. We further assigned 2,233 clinically healthy cows to the control group. The incidence of endometritis was 41.6% in this study. Based on the results of reproductive indices including median days to first AI, days open (DO), first service conception rate, conception rate in 2nd and 3rd services, conception rate in all three services, pregnancy rate < 100 days and pregnancy rate < 200 days, except for median days to first AI in other reproductive indexes, reproductive performance was significantly lower in LP group compared with the healthy cows and other treatment groups (p < 0.05). Except for the first service conception rate and proportion of cows pregnant before 100 days in milk (DIM), there existed no significant difference between the DEX group and the control as far as reproductive performance is concerned (p ≥ 0.05). The first service conception rate was recognizably lower in DEX group compared with OTC and PG (p < 0.05). In conclusion, the use of a non-antibiotic special solution of dextrose 50% is a good alternative to antibiotic agents concerning the treatment of CE in dairy cows.

Management of Reproductive Disease in Dairy Cows

Postpartum diseases are common in dairy cows, and their incidence contributes to reduced fertility and increased risk of culling, making their prevention and management extremely important. Reproductive efficiency has a major impact on economic success of any dairy production unit. Optimizing reproductive efficiency contributes to overall efficiency of production units, minimizing environmental impacts and contributing to sustainability of food production. Additionally, control of reproductive diseases is important for maintenance of health and welfare of dairy cows; for minimizing use of antibiotics; and ensuring a wholesome, safe, and nutritious product.

The effect of prepartum intravaginal bacteriophage administration on the incidence of retained placenta and metritis

The objective of this study was to evaluate the effect of prepartum intravaginal administration of an anti-Escherichia coli bacteriophage cocktail on uterine health and reproductive performance of lactating dairy cows. The study was conducted on a commercial dairy farm located near Ithaca, New York, from March to September 2012, and 107 cows were enrolled. The cows were divided randomly into 2 groups (treatment and control); treatment group cows were submitted to 3 intravaginal administrations of 20 mL of a bacteriophage cocktail including 10 different phages in a lysate with titration of approximately 10(9) plaque-forming units, on d 230, 260, and 275 of gestation. Control cows were not treated with a placebo, and physical examination and sample collection was conducted equally for both groups. Vaginal swabs were collected at d 230, 260, and 275 d of gestation, cervical swabs were collected at 3±1 d in milk, and blood was collected at 275 d of gestation for nonesterified fatty acids and interleukin (IL)-6 serum level measurements and at 10 DIM for β-hydroxybutyrate and IL-6 serum level measurements. The bacteriophage cocktail significantly increased the incidence of retained placenta and metritis. Swab samples were cultured for E. coli and no difference was found between treatment and control groups. The lysate contained 6×10(9) IU of lipopolysaccharide/mL and could have caused prepartum overstimulation of toll-like receptor-4 (TLR4)-chemokine pathway, leading to a weaker immune response. However, IL-6 was not affected by treatment, although sample size was insufficient to prove a treatment effect on the suppression of the chemokine cascade and innate immune system. Bacteriophage treatment had an excellent bactericidal effect in previous in vitro trials; however, special attention must be given to production of the cocktail to obtain a purified solution free of E. coli bacterial products and fragments, particularly lipopolysaccharide.

Salmonella bacteriophage diversity reflects host diversity on dairy farms

Salmonella is an animal and human pathogen of worldwide concern. Surveillance programs indicate that the incidence of Salmonella serovars fluctuates over time. While bacteriophages are likely to play a role in driving microbial diversity, our understanding of the ecology and diversity of Salmonella phages is limited. Here we report the isolation of Salmonella phages from manure samples from 13 dairy farms with a history of Salmonella presence. Salmonella phages were isolated from 10 of the 13 farms; overall 108 phage isolates were obtained on serovar Newport, Typhimurium, Dublin, Kentucky, Anatum, Mbandaka, and Cerro hosts. Host range characterization found that 51% of phage isolates had a narrow host range, while 49% showed a broad host range. The phage isolates represented 65 lysis profiles; genome size profiling of 94 phage isolates allowed for classification of phage isolates into 11 groups with subsequent restriction fragment length polymorphism analysis showing considerable variation within a given group. Our data not only show an abundance of diverse Salmonella phage isolates in dairy farms, but also show that phage isolates that lyse the most common serovars causing salmonellosis in cattle are frequently obtained, suggesting that phages may play an important role in the ecology of Salmonella on dairy farms.

The effect of intrauterine administration of mannose or bacteriophage on uterine health and fertility of dairy cows with special focus on Escherichia coli and Arcanobacterium pyogenes

The objective of this study was to evaluate the effects of intrauterine administration of 50 g of ultrapure mannose or a bacteriophage cocktail and the presence of Escherichia coli and Arcanobacterium pyogenes in the uterine lumen on uterine health and reproductive performance of lactating dairy cows. The study was conducted on a commercial dairy farm located near Ithaca, New York, from May 4 to January 20, 2011, and 597 cows were enrolled. The cows were divided randomly into 3 treatment groups, and treatments were administered at 2 ± 1 d in milk (DIM). Treatment 1 consisted of intrauterine administration of 50 g of ultrapure mannose powder divided in 4 pills; treatment 2 consisted of intrauterine administration of a bacteriophage cocktail that included 4 different phages in one pill, with a dose of approximately 10⁷ plaque-forming units; and treatment 3 consisted of intrauterine administration of one empty pill (control). Intrauterine fluid swabs were collected on day of treatment and at 10 ± 3 DIM; uterine lavage samples were collected at 35 ± 3 DIM. Swabs and uterine lavage samples were cultured for E. coli and A. pyogenes. The intrauterine administration of mannose and bacteriophage did not affect uterine health, reproduction performance, or outcome of intrauterine secretion cultures for E. coli and A. pyogenes. Prevalence of intrauterine E. coli at 2 ± 1 DIM and A. pyogenes at 2 ± 1, 10 ± 3, and 35 ± 3 were affected by retained placenta. Additionally, prevalence of intrauterine E. coli at 10 ± 3 and A. pyogenes at 35 ± 3 DIM were associated with metritis, and cows that were diagnosed with clinical endometritis at 35 ± 3 DIM had greater prevalence of intrauterine E. coli at 2 ± 1 DIM and A. pyogenes at 35 ± 3 DIM. Furthermore, cows positive for E. coli at 2 ± 1 and 10 ± 3 DIM and for A. pyogenes at 10 ± 3 DIM had 1.63, 2.34, and 1.54 increased odds of having metritis. Cows positive for A. pyogenes at 35 ± 3 DIM and for E. coli at 2 ± 1 DIM had 19.8 and 2.66 higher odds of being diagnosed with clinical endometritis, respectively. Additionally, cows negative for E. coli at 2 ± 1 DIM were 1.39 times more likely to conceive than cows positive cows for E. coli.

Evaluation of oral administration of bacteriophages to neonatal calves: Phage survival and impact on fecal Escherichia coli

Diarrhea is an important cause of morbidity and mortality in neonatal calves. Several enteropathogens are associated with diarrhea in young calves, with Enterotoxigenic Escherichia coli (ETEC) infection being the most common type of colibacillosis. The rise of antibiotic resistance in a number of medically important bacterial pathogens has revived interest in the use of bacteriophages as anti-bacterial therapeutic agents. Here we describe the results of a randomized, placebo-controlled, double-blinded study designed to evaluate the effect of an oral bacteriophage cocktail on fecal E. coli colony-forming units (CFU). Ten calves were enrolled in the study to either the bacteriophage group or the placebo group for 22 feedings. Calves in the bacteriophage treatment group (n = 6) received a total of 10⁶ plaque-forming units (PFU) (volume = 5 ml) of each of four bacteriophages while the placebo group (n = 4) received only phosphate-buffered saline (5 ml). Fresh fecal samples and blood samples were collected daily from each calf and analyzed for bacterial count and presence of bacteriophage. E. coli-infecting phages were recovered from all phage-treated calves at concentrations of 10² to 10³ PFU per gram of rectal contents, but none was detected in serum. Phage treatment caused a reduction in fecal E. coli when compared to the control group: the mean log CFU for the placebo-treated group was 9.25 (SE = 0.42) versus 9.11 (SE = 0.34) for the phage-treated group, but the difference was not statistically significant.

Isolation and characterization of two bacteriophages with strong in vitro antimicrobial activity against Pseudomonas aeruginosa isolated from dogs with ocular infections

OBJECTIVE

To isolate and characterize bacteriophages with strong in vitro lytic activity against various pathogenic Pseudomonas aeruginosa strains isolated from dogs with ocular infections.

SAMPLE

26 genetically distinct P aeruginosa isolates.

PROCEDURES

P aeruginosa strains were derived from dogs with naturally acquired ulcerative keratitis. From a large-scale screening for bacteriophages with potential therapeutic benefit against canine ocular infections, 2 bacteriophages (P2S2 and P5U5) were selected; host ranges were determined, and phage nucleic acid type and genetic profile were identified via enzymatic digestion. Electron microscopy was used to characterize bacteriophage ultrastructure. Bacteriophage temperature and pH stabilities were assessed by use of double-layer agar overlay titration. A cocultivation assay was used to evaluate the effect of the bacteriophages on bacterial host growth.

RESULTS

P5U5 was active against all P aeruginosa isolates, whereas P2S2 formed lytic plaques on plates of 21 (80.8%) isolates. For each bacteriophage, the genomic nucleic acid was DNA; each was genetically distinct. Ultrastructurally, P2S2 and P5U5 appeared likely to belong to the Podoviridae and Siphoviridae families, respectively. The bacteriophages were stable within a pH range of 4 to 12; however, titers of both bacteriophages decreased following heating for 10 to 50 minutes at 45° or 60°C. Growth of each P aeruginosa isolate was significantly inhibited in coculture with P2S2 or P5U5; the dose response was related to the plaque-forming unit-to-CFU ratios.

CONCLUSIONS AND CLINICAL RELEVANCE

Bacteriophages P2S2 and P5U5 appear to be good candidates for phage treatment of infection caused by pathogenic P aeruginosa in dogs.

Hormonal and antimicrobial therapy in theriogenology practice: currently approved drugs in the USA and possible future directions

Hormonal and antimicrobial therapies are essential to regulate and maintain healthy reproduction in domestic animals. The appropriate and legal use of these compounds is ultimately the responsibility of the veterinarian and other users, with a primary mission to directly protect and promote the health of animals, and indirectly the health of people. The appropriate use of these products is defined by the Federal Food, Drug, and Cosmetic Act, 21 United States of America § 301 et seq and implementing regulations in the Code of Federal Regulations. In the past, use of a drug in an animal for an unapproved use violated this Act. However, passage of the Animal Medicinal Drug Use Clarification Act 1994 legalized the extra-label use of certain animal and human drugs in veterinary practice for treating diseases. This manuscript reviews currently approved hormonal and antimicrobial drugs for use in theriogenology. Considering the ever increasing knowledge in the area of veterinary reproduction, particularly in the treatment and control of reproduction using antimicrobials and hormones, it would be beneficial to widen the therapeutic options in these categories. The potential for widening the therapeutic options is also discussed in this review, by providing a non-exhaustive but essential list of potential new drugs for use in clinical animal reproduction (theriogenology).

Susceptibility of Escherichia coli isolated from uteri of postpartum dairy cows to antibiotic and environmental bacteriophages. Part II: In vitro antimicrobial activity evaluation of a bacteriophage cocktail and several antibiotics

The use of pathogenic-specific antimicrobials, as proposed by bacteriophage therapy, is expected to reduce the incidence of resistance development. Eighty Escherichia coli isolated from uteri of Holstein dairy cows were phenotypically characterized for antimicrobial resistance to ampicillin, ceftiofur, chloramphenicol, florfenicol, spectinomycin, streptomycin, and tetracycline by broth microdilution method. The lytic activity of a bacteriophage cocktail against all isolates was performed by a similar method. Additionally, the effect of different concentrations of antimicrobials and multiplicities of infections (MOI) of the bacteriophage cocktail on E. coli growth curve was measured. Isolates exhibited resistance to ampicillin (33.7%), ceftiofur (1.2%), chloramphenicol (100%), and florfenicol (100%). All strains were resistant to at least 2 of the antimicrobial agents tested; multidrug resistance (>or=3 of 7 antimicrobials tested) was observed in 35% of E. coli isolates. The major multidrug resistance profile was found for ampicillin-chloramphenicol-florfenicol, which was observed in more than 96.4% of the multidrug-resistant isolates. The bacteriophage cocktail preparation showed strong antimicrobial activity against multidrug-resistant E. coli. Multiplicity of infection as low as 10(-4) affected the growth of the E. coli isolates. The ratio of 10 bacteriophage particles per bacterial cell (MOI=10(1)) was efficient in inhibiting at least 50% of all isolates. Higher MOI should be tested in future in vitro studies to establish ratios that completely inhibit bacterial growth during longer periods. All isolates resistant to florfenicol were resistant to chloramphenicol and, because florfenicol was recently introduced into veterinary clinics, this finding suggests that the selection pressure of chloramphenicol, as well as other antimicrobials, may still play a relevant role in the emergence and dissemination of florfenicol resistance in E. coli. The bacteriophage cocktail had a notable capacity to inhibit the in vitro growth of E. coli isolates, and it may be an attractive alternative to conventional treatment of metritis by reducing E. coli in uteri of postpartum dairy cows.