Short communication: Investigation of extra-intestinal pathogenic Escherichia coli virulence genes, bacterial motility, and multidrug resistance pattern of strains isolated from dairy cows with different severity scores of clinical mastitis

The spontaneously produced lysogenic prophage phi456 promotes bacterial resistance to adverse environments and enhances the colonization ability of avian pathogenic Escherichia coli strain DE456

In the last decade, prophages that possess the ability of lysogenic transformation have become increasingly significant. Their transfer and subsequent activity in the host have a significant impact on the evolution of bacteria. Here, we investigate the role of prophage phi456 with high spontaneous induction in the bacterial genome of Avian pathogenic Escherichia coli (APEC) DE456. The phage particles, phi456, that were released from DE456 were isolated, purified, and sequenced. Additionally, phage particles were no longer observed either during normal growth or induced by nalidixic acid in DE456Δphi456. This indicated that the released phage particles from DE456 were only phi456. We demonstrated that phi456 contributed to biofilm formation through spontaneous induction of the accompanying increase in the eDNA content. The survival ability of DE456Δphi456 was decreased in avian macrophage HD11 under oxidative stress and acidic conditions. This is likely due to a decrease in the transcription levels of three crucial genes-rpoS, katE, and oxyR-which are needed to help the bacteria adapt to and survive in adverse environments. It has been observed through animal experiments that the presence of phi456 in the DE456 genome enhances colonization ability in vivo. Additionally, the number of type I fimbriae in DE456Δphi456 was observed to be reduced under transmission electron microscopy when compared to the wild-type strain. The qRT-PCR results indicated that the expression levels of the subunit of I fimbriae (fimA) and its apical adhesin (fimH) were significantly lower in DE456Δphi456. Therefore, it can be concluded that phi456 plays a crucial role in helping bacterial hosts survive in unfavorable conditions and enhancing the colonization ability in DE456.

Identification of Escherichia coli isolated from flies (Insecta: Diptera) that inhabit the environment of dairy farms harboring extraintestinal virulence markers

AIMS

We investigate extraintestinal pathogenic genes (ExPEC) related to virulence of Escherichia coli in flies from the dairy environment.

METHODS AND RESULTS

We collected 217 flies from nine dairy farms, which were submitted to microbiological culture. Fifty-one E. coli were identified using mass spectrometry. Eleven dipteran families were identified, with a predominance of Muscidae, and a minor frequency of Tachinidae, Drosophilidae, Sphaeroceridae, Ulidiidae, Syrphidae, Chloropidae, Calliphoridae, Sarcophagidae, and Piophilidae. A panel of 16 virulence-encoding genes related to ExPEC infections were investigated, which revealed predominance of serum resistance (traT, 31/51 = 60.8%; ompT, 29/51 = 56.9%), iron uptake (irp2, 17/51 = 33.3%, iucD 11/51 = 21.6%), and adhesins (papC, 6/51 = 11.8%; papA, 5/51 = 9.8%).

CONCLUSIONS

Our findings reveal Dipterans from milking environment carrying ExPEC virulence-encoding genes also identified in clinical bovine E. coli-induced infections.

In Vitro Activity of Quaternary Ammonium in Prototheca Isolated from Clinical Bovine Mastitis Identified by Mass Spectrometry and PCR Sequencing of the cytb Gene Marker

The in vitro algaecide activity of quaternary ammonium (QA) against Prototheca isolated from bovine clinical mastitis was investigated, in which the clinical severity was scored, milk samples were subjected to microbiological culture, and algal species were identified by molecular typing. A total of 4275 milk clinical samples of different cows from ten large dairy farms were used. Forty-four (1%) samples of cows from three dairy farms yielded growth of Prototheca, of which 88.6% (39/44) were identified as Prototheca bovis and 11.3% (5/44) as Prototheca sp. by MALDI-TOF MS, whereas 100% of the isolates were identified as P. bovis using PCR sequencing of the cytb gene. Among cows for which clinical severity scoring was available, 78.8% (26/33) and 21.2% (7/33) had mild and moderate infections, respectively, whereas no animal showed severe clinical signs. The algaecide activity of QA in Prototheca was observed in low concentrations among all isolates, in 20.4% (9/44) at 35 ppm, 36.4% (16/44) at 17 ppm, and 43.2% (19/44) at an 8 ppm, in addition to activity on three reference Prototheca strains. Overall, the study highlights the predominance of P. bovis as the causative agent of algal mastitis in bovines. Prototheca induced abnormalities preponderantly in the milk and mammary gland tissue of cows, and to our knowledge, our study is the first to apply clinical severity scoring in protothecal mastitis. In addition, the study underlines the activity of QA in low concentrations against Prototheca, indicating its potential use as an antiseptic/disinfectant in milking facilities and dairy environments.

Bacterial identification in cerebrospinal fluid of domestic species with neurologic signs: a retrospective case-series study in 136 animals (2005-2021)

Central nervous system (CNS) infections comprise life-threatening clinical conditions in domestic species, and are commonly related to severe sequelae, disability, or high fatality rates. A set of bacterial pathogens have been identified in central nervous infections in livestock and companion animals, although the most of descriptions are restricted to case reports and a lack of comprehensive studies involving CNS-related bacterial infections have been focused on a great number of domestic species. In this scenario, we retrospectively investigated selected epidemiological data, clinical findings, bacteriological culture, and in vitro susceptibility patterns of 136 nonrepetitive neurologic cases in domestic species (2005-2021). Bacterial isolates were recovered from 25% (34/136) of the cerebrospinal fluid (CSF) sampled. The isolates were obtained from cattle (9/136 = 6.6%), dogs (7/136 = 5.1%), horses (6/136 = 4.4%), goats (3/136 = 2.2%), pigs (3/136 = 2.2%), sheep (3/136 = 2.2%), cats (2/136 = 1.5%), and asinine (1/136 = 0.7%). Among animals with bacterial isolation, Staphylococcus aureus (6/34 = 17.6%), Escherichia coli (5/34 = 14.7%), Staphylococcus beta-hemolytic (5/34 = 14.7%), and Trueperella pyogenes (3/34 = 8.8%) were predominant, in addition to a miscellaneous of other bacteria isolated in minor frequency, e.g., Corynebacterium pseudotuberculosis, Enterobacter cloacae, Mannheimia haemolytica, Pseudomonas aeruginosa, and Streptococcus equi subsp. equi. In vitro susceptibility tests of isolates revealed that amoxicillin/clavulanic acid (11/13 = 84.6%), cephalexin (9/11 = 81.8%), and florfenicol (9/12 = 75%) were the most effective antimicrobials. Conversely, isolates exhibited resistance mainly to tetracycline (6/10 = 60%), penicillin (6/11 = 54.5%), and trimethoprim/sulfamethoxazole (5/11 = 45.5%). Also, multidrug resistance to ≥ 3 classes of antimicrobials was found in 23.5% (8/34) strains. Data relative to the outcome was available in 79.4% (27/34) of animals that had bacterial isolation, and from these, the lethality rate was 92.6% (25/27). Incoordination (14/34 = 41.2%), recumbency (11/34 = 32.4%), apathy (10/34 = 29.4%), anorexia (9/34 = 26.5%), blindness (7/34 = 20.6%), seizure (6/34 = 17.6%), limb paresis (5/34 = 14.7%), head-pressing (4/34 = 11.8%), and nystagmus (3/34 = 8.8%) were the most frequent clinical signs. A variety of bacterial pathogens were identified in the CSF of domestic species showing neurologic signs, with a predominance of staphylococci, streptococci, and enterobacteria. High lethality of cases, poor in vitro efficacy of conventional antimicrobials, and a high in vitro multidrug resistance pattern of isolates were seen. Our results contribute to etiological characterization, antimicrobial resistance patterns, and clinical-epidemiological findings of bacterial infections in domestic species with neurological signs.

Characterization of mammary pathogenic Escherichia coli reveals the diversity of Escherichia coli isolates associated with bovine clinical mastitis in Brazil

Mammary pathogenic Escherichia coli (MPEC) is one of the most common pathogens associated with clinical mastitis. We analyzed isolates obtained from milk samples of cows with clinical mastitis, collected from 10 farms in Brazil, to verify molecular and phenotypic characteristics. A total of 192 (4.5%) mammary pathogenic E. coli isolates were obtained from 4,275 milk samples analyzed, but we tested 161. We assigned most of these isolates to E. coli phylogroups B1 (52.8%) and A (36.6%), although phylogroups B2, C, D, E, and unknown also occurred. All isolates were assessed for the presence of several genes encoding virulence factors, such as adhesins (sfaDE, papC, afaBC III, ecpA, fimH, papA, and iha), toxins (hlyA, cnf1, sat, vat, and cdt), siderophores (iroN, irp2, iucD, ireA, and sitA), an invasion protein (ibeA), and serum resistance proteins (traT, KpsMTII, and ompT), and isolates from phylogroups B1, B2, and E showed up to 8 genes. Two isolates harbored the locus of enterocyte effacement (escN⁺) and lack the bundle-forming pilus (bfpB^-) operon, which corresponds to a molecular profile of a subgroup of diarrheagenic E. coli (aEPEC), thus being classified as hybrid MPEC/aEPEC isolates. These isolates displayed a localized adherence-like pattern of adherence in HeLa cells and were able to promote F-actin polymerization underneath adherent bacteria. Based on the pulsed-field gel electrophoresis analyses, considerable genetic variability was observed. A low index of antimicrobial resistance was observed and 2 extended-spectrum β-lactamase-producing E. coli were identified, both harboring bla_CTX-M15 gene, and were classified as ST10 and ST993 using multilocus sequence typing. A total of 148 (91.2%) isolates were weak biofilm producers or formed no biofilm. Because raw milk is still frequently consumed in Brazil, the occurrence of virulence factor-encoding genes from extraintestinal or diarrheagenic E. coli added to the presence of extended-spectrum β-lactamase-producing isolates can turn this veterinary medicine problem into a public health concern.

Genome-Based Characterization of Multidrug-Resistant Escherichia coli Isolated from Clinical Bovine Mastitis

Mastitis occurrence in dairy cows is a broad topic that involves several sectors, from antimicrobial resistance and virulence of strains to economic implications and cattle management practices. Here, we assessed the molecular characterization (antimicrobial resistance determinants, virulence genes, sequences type, serotypes, and plasmid types) of 178 Escherichia coli strains isolated from milk samples from cows with clinical mastitis using a genome-based k-mers approach. Of these, 53 (29.8%) showed multidrug resistance by disc diffusion. We selected eight multidrug-resistant mastitis-associated E. coli for whole-genome sequencing and molecular characterization based on raw data using k-mers. We assessed antimicrobial resistance genes, virulence factors, serotypes, Multilocus Sequence Typing (MLST), and plasmid types. The most antimicrobial resistance gene found were bla_TEM-1B (7/8), tetA (6/8), strA (6/8), strB (6/8), and qnrB19 (5/8). A total of 25 virulence factors were detected encoding adhesins, capsule, enzymes/proteins, increased serum survival, hemolysin, colicins, and iron uptake. These virulence factors were associated with Extraintestinal Pathogenic E. coli. Three pandemic clones were found: ST10, ST101, and ST69. Two E. coli were assigned in the O117 serogroup and one in the O8:H25 serotype. The most common plasmid groups were IncFII (7/8) and IncFIB (6/8). Our findings contribute to the knowledge of virulence mechanisms, epidemiological aspects, and antimicrobial resistance determinants of E. coli strains obtained from clinical mammary infections of cows.

Virulence-encoding genes related to extraintestinal pathogenic E. coli and multidrug resistant pattern of strains isolated from neonatal calves with different severity scores of umbilical infections

Umbilical infections in calves comprise a major cause of neonatal mortality and have been related to a variety of microorganisms. E. coli is an opportunistic enteropathogen characterized by a diversity of virulence factors (VF). Nonetheless, the gene profiles that encode VF associated with umbilical infections in calves and their effect on the clinical severity remains unclear. In this scenario, microbial identification (with an emphasis on E. coli), was carried out among 150 neonatal calves (≤30 days of age) with umbilical infections, where the omphalopathies were clinically scored as mild, moderate, or severe. Also, a panel of 16 virulence-encoding genes related to extraintestinal pathogenic E. coli (ExPEC) were investigated, i.e., fimbriae/adhesins (sfa/focDEa, papA, papC, afaBC), toxins (hlyA, sat, cnf1, cdt), siderophores (iroN, irp2, iucD, ireA), invasins (ibeA), and serum resistance (ompT, traT, kpsMT II). Bacteria and yeasts isolates were identified using mass spectrometry. Bacteria, yeasts, and fungi were isolated in 94.7% (142/150) of neonatal calves sampled. E. coli was the agent most frequently isolated (59/150 = 39.3%), in pure culture (27/59 = 45.8%) and combined infections (32/59 = 54.2%), although a great variety (n = 83) of other species of microorganisms were identified. Clinical severity scores of 1, 2, and 3 were observed in 32.2% (19/59), 23.7% (14/59), and 44.1% (26/59) of E. coli infections, respectively. The ExPEC genes detected were related to serum resistance (traT, 42/59 = 72.2%; ompT, 35/59 = 59.3%, kpsMTII, 10/59 = 17%), invasins (ibeA, 11/59 = 18.6%), siderophores (iucD, 9/59 = 15.3%; iroN, 8/59 = 13.6%), and adhesins/fimbriae (papA, 8/59 = 13.6%; papC, 15/59 = 9.6%). The presence of each virulence gene was not associated with the case's clinical score. Among all isolates, 89.8% (53/59) showed in vitro resistance to sulfamethoxazole/trimethoprim and 59.3% to ampicillin (35/59), while 94.1% (55/59) revealed a multidrug resistant profile. Great complexity of bacteria, yeast, and fungi species was identified, reinforcing the umbilical infections of neonatal calves as a polymicrobial disorder. The high occurrence of E. coli (39.3%) highlights the role of this pathogen in the etiology of umbilical infections in calves. Furthermore, a panel of ExPEC genes was investigated for the first time among calves that were clinically scored for case severity. The high prevalence of traT and ompT indicates that these serum resistance-related genes could be used as biomarkers for further investigations of ExPEC isolates from umbilical infections. Our results contribute to the etiological investigation, clinical severity scoring, antimicrobial resistance pattern, and virulence-related to ExPEC genes involved in umbilical infections of neonatal calves.

Genetic and Antimicrobial Resistance Profiles of Mammary Pathogenic E. coli (MPEC) Isolates from Bovine Clinical Mastitis

Mammary pathogenic E. coli (MPEC) is one of the main pathogens of environmental origin responsible for causing clinical mastitis worldwide. Even though E. coli are strongly associated with transient or persistent mastitis and the economic impacts of this disease, the virulence factors involved in the pathogenesis of MPEC remain unknown. Our aim was to characterize 110 MPEC isolates obtained from the milk of cows with clinical mastitis, regarding the virulence factor-encoding genes present, adherence patterns on HeLa cells, and antimicrobial resistance profile. The MPEC isolates were classified mainly in phylogroups A (50.9%) and B1 (38.2%). None of the isolates harbored genes used for diarrheagenic E. coli classification, but 26 (23.6%) and 4 (3.6%) isolates produced the aggregative or diffuse adherence pattern, respectively. Among the 22 genes investigated, encoding virulence factors associated with extraintestinal pathogenic E. coli pathogenesis, fimH (93.6%) was the most frequent, followed by traT (77.3%) and ompT (68.2%). Pulsed-field gel electrophoresis analysis revealed six pulse-types with isolates obtained over time, thus indicating persistent intramammary infections. The genes encoding beta-lactamases detected were as follows: bla_TEM (35/31.8%); bla_CTX-M-2/bla_CTX-M-8 (2/1.8%); bla_CTX-M-15 and bla_CMY-2 (1/0.9%); five isolates were classified as extended spectrum beta-lactamase (ESBL) producers. As far as we know, papA, shf, ireA, sat and bla_CTX-M-8 were detected for the first time in MPEC. In summary, the genetic profile of the MPEC studied was highly heterogeneous, making it impossible to establish a common genetic profile useful for molecular MPEC classification. Moreover, the detection of ESBL-producing isolates is a serious public health concern.

Pathogenome comparison and global phylogeny of Escherichia coli ST1485 strains

Escherichia coli ST1485 strains belong to the clinically important phylogroup F and have disseminated worldwide in humans, animals, and the environment. Here, we elucidated the pathogenome of a global collection of E. coli ST1485 isolates from diverse sources retrieved from public databases and a high-quality sequenced complete genome of colistin-resistant E. coli strain CFSAN061771 isolated from raw milk cheese which designated as a reference strain. CFSAN061771 belongs to O83:H42-ST1485 pathotype and carries a conjugative ColV plasmid, pCFSAN061771_01, combining extraintestinal virulence genes (ompt, sitA, iroN, etsC, traT, cvaC, hylF, iss, tsh, mchf, iucC, iutA) with a multidrug resistance island (bla_TEM-1, aph(6)-Id, aph(3″)-Ib, sul2, dfrA14). Comparative genomic analysis revealed a high frequency of pCFSAN061771_01-like plasmids in E. coli ST1485. A notable evolutionary genetic event in E. coli ST1485 strains is the acquisition of a pCFSAN061771_02-like plasmid, which confers resistance to several antimicrobials, tellurium, and quaternary ammonium compounds. The identical virulence and antibiotic resistance profiles identified in some human and animal strains are worrisome. This is the first study to emphasize the significance of E. coli ST1485 as a global high-risk virulent and multidrug-resistant clone with zoonotic potential.

Escherichia coli Mastitis in Dairy Cattle: Etiology, Diagnosis, and Treatment Challenges

Bovine mastitis is an inflammation of the udder tissue parenchyma that causes pathological changes in the glandular tissue and abnormalities in milk leading to significant economic losses to the dairy industry across the world. Mammary pathogenic Escherichia (E.) coli (MPEC) is one of the main etiologic agents of acute clinical mastitis in dairy cattle. MPEC strains have virulence attributes to resist the host innate defenses and thrive in the mammary gland environment. The association between specific virulence factors of MPEC with the severity of mastitis in cattle is not fully understood. Furthermore, the indiscriminate use of antibiotics to treat mastitis has resulted in antimicrobial resistance to all major antibiotic classes in MPEC. A thorough understanding of MPEC’s pathogenesis and antimicrobial susceptibility pattern is required to develop better interventions to reduce mastitis incidence and prevalence in cattle and the environment. This review compiles important information on mastitis caused by MPEC (e.g., types of mastitis, host immune response, diagnosis, treatment, and control of the disease) as well as the current knowledge on MPEC virulence factors, antimicrobial resistance, and the dilemma of MPEC as a new pathotype. The information provided in this review is critical to identifying gaps in knowledge that will guide future studies to better design diagnostic, prevent, and develop therapeutic interventions for this significant dairy disease.

Characterization of Antibiotic Resistant Coliform Bacteria and Resistance Genes Isolated from Samples of Smoothie Drinks and Raw Milk

Raw foodstuffs have been marked as a healthier alternative in the context of nutrient content and are becoming more popular with consumers. Thermally untreated foods may represent a microbiological risk connected with the possible presence of antimicrobial resistance. The aim of this study was to prove that popular raw food beverages such as smoothies and raw milk may be a source of antibiotic-resistant coliform bacteria and resistant genes. The majority of antibiotic-resistant isolates (110) were identified as Enterobacter spp., Escherichia coli, and species of Klebsiella spp., predominantly β-lactam and chloramphenicol resistant. Multidrug resistance has been registered in one-third of resistants. Overproduction of efflux pumps was clarified in 8 different bacteria. The majority of resistant isolates were strong biofilm producers. Antibiotic resistance gene blaOXA was detected in 25% of isolates, especially in E. coli. Resistance genes blaTEM and blaSHV were detected in 19% and 14%, respectively. This is the first study to point out that popular raw drinks such as smoothies or raw milk, besides their nutrient benefits, could represent a reservoir of antibiotic-resistant bacteria as well as antibiotic resistance genes. According to this, raw drinks could contribute to the dissemination of antibiotic resistance in the human gastrointestinal tract and environment.

Distribution of CRISPR in Escherichia coli Isolated from Bulk Tank Milk and Its Potential Relationship with Virulence

Simple Summary

In the dairy farms of many different countries, E. coli is one of the most common causes of mastitis. It is defined as mammary pathogenic E. coli, and is known to cause opportunistic infections by possessing diverse virulence factors. Therefore, the purpose of this study was to investigate the virulence potential of E. coli isolates from bulk tank milk in Korea, and observe its association with clustered regularly interspaced short palindromic repeat (CRISPR) arrays. The results showed that out of 183 isolates, 164 (89.6%) possessed one or more of 18 virulence genes, and belonged to phylogenetic groups B1 (64.0%), A (20.1%), D (8.5%), and C (7.3%). CRISPR arrays of E. coli are classified as either CRISPR I-E (CRISPR 1 and 2) or CRISPR I-F (CRISPR 3 and 4). In this study, only CRISPR 1 (95.7%) and 2 (74.4%) were detected. Among the eight protospacers matching plasmids and phages, three were associated with gene regulation, and one was associated with virulence. Moreover, the different virulence genes showed significantly different patterns of CRISPR distribution and CRISPR sequence-types. This result implies that CRISPR loci may be associated with gene regulation and pathogenicity in E. coli, and that the CRISPR sequence-typing approach can help to clarify and trace virulence potential, even though the E. coli isolates were from normal bulk tank milk.

Abstract

Escherichia coli is one of the most common causes of mastitis on dairy farms around the world, but its clinical severity is determined by a combination of virulence factors. Recently, clustered regularly interspaced short palindromic repeat (CRISPR) arrays have been reported as a novel typing method because of their usefulness in discriminating pathogenic bacterial isolates. Therefore, this study aimed to investigate the virulence potential of E. coli isolated from bulk tank milk, not from mastitis, and to analyze its pathogenic characterization using the CRISPR typing method. In total, 164 (89.6%) out of 183 E. coli isolated from the bulk tank milk of 290 farms carried one or more of eighteen virulence genes. The most prevalent virulence gene was fimH (80.9%), followed by iss (38.3%), traT (26.8%), ompT (25.7%), afa/draBC (24.0%), and univcnf (21.9%). Moreover, the phylogenetic group with the highest prevalence was B1 (64.0%), followed by A (20.1%), D (8.5%), and C (7.3%) (p < 0.05). Among the four CRISPR loci, only two, CRISPR 1 and CRISPR 2, were found. Interestingly, the distribution of CRISPR 1 was significantly higher in groups A and B1 compared to that of CRISPR 2 (p < 0.05), but there were no significant differences in groups C and D. The prevalence of CRISPR 1 by virulence gene ranged from 91.8% to 100%, whereas that of CRISPR 2 ranged from 57.5% to 93.9%. The distribution of CRISPR 1 was significantly higher in fimH, ompT, afa/draBC, and univcnf genes than that of CRISPR 2 (p < 0.05). The most prevalent E. coli sequence types (EST) among 26 ESTs was EST 22 (45.1%), followed by EST 4 (23.2%), EST 16 (20.1%), EST 25 (19.5%), and EST 24 (18.3%). Interestingly, four genes, fimH, ompT, afa/draBC, and univcnf, had a significantly higher prevalence in both EST 4 and EST 22 (p < 0.05). Among the seven protospacers derived from CRISPR 1, protospacer 163 had the highest prevalence (20.4%), and it only existed in EST 4 and EST 22. This study suggests that the CRISPR sequence-typing approach can help to clarify and trace virulence potential, although the E. coli isolates were from normal bulk tank milk and not from mastitis.

Klebsiella-induced infections in domestic species: a case-series study in 697 animals (1997-2019)

Klebsiella species, particularly K. pneumoniae, are well-known opportunistic enterobacteria related to complexity of clinical infections in humans and animals, commonly refractory to conventional therapy. The domestic animals may represent a source of the pathogenic and multidrug-resistant Klebsiella species to humans. Nevertheless, most studies involving Klebsiella-induced infections in domestic animals are restricted to case reports or outbreaks. We retrospectively investigated selected epidemiological data, clinical aspects, and in vitro susceptibility pattern of 697 non-repetitive Klebsiella infections in livestock and companion species (1997-2019). The isolates were obtained from different clinical disorders from dogs (n = 393), cattle (n = 149), horses (n = 98), cats (n = 27), pigs (n = 22), sheep (n = 5), goats (n = 2), and buffalo (n = 1), except four isolates from subclinical bovine mastitis. Urinary (223/697 = 32%), enteric (117/697 = 16.8%), mammary (85/697 = 12.2%), reproductive (85/697 = 12.2%), and respiratory disorders (67/697 = 9.6%) were the most common clinical manifestations. Other miscellaneous clinical pictures (116/697 = 16.6%) included abscesses, otitis, hepatitis, conjunctivitis, pyodermitis, sepsis, and encephalitis. Norfloxacin (183/245 = 74.7%) and gentamicin (226/330 = 68.5%) were the most effective antimicrobials. High in vitro resistance of the isolates was seen to ampicillin (326/355 = 91.8%), amoxicillin/clavulanic acid (25/62 = 40.3%), and trimethoprim/sulfamethoxazole (100/252 = 39.7), and multidrug resistance to ≥ 3 classes of antimicrobials was found in 20.4% (142/697) isolates. Wide variety of clinical manifestations of Klebsiella-induced infections was observed, with a predominance of urinary, enteric, mammary, reproductive, and respiratory tract disorders, reinforcing opportunistic behavior of agent. Poor in vitro efficacy was observed to some conventional antimicrobials and ~ 20% of isolates exhibited resistance pattern, reinforcing the need for proper use of drugs on therapy approaches in domestic animals to avoid multidrug-resistant bacteria, an emergent global concern.

An overview on mastitis-associated Escherichia coli: Pathogenicity, host immunity and the use of alternative therapies

Escherichia coli is one of the leading causes of bovine mastitis; it can cause sub-clinical, and clinical mastitis characterized by systemic changes, abnormal appearance of milk, and udder inflammation. E. coli pathogenicity in the bovine udder is due to the interaction between its virulence factors and the host factors; it was also linked to the presence of a new pathotype termed mammary pathogenic E. coli (MPEC). However, the presence of this pathotype is commonly debated. Its main virulence factor is the lipopolysaccharide (LPS) that is responsible for causing an endotoxic shock, and inducing a strong immune response by binding to the toll-like receptor 4 (TLR4), and stimulating the expression of chemokines (such as IL-8, and RANTES) and pro-inflammatory cytokines (such as IL-6, and IL-1β). This strong immune response could be used to develop alternative and safe approaches to control E. coli causing bovine mastitis by targeting pro-inflammatory cytokines that can damage the host tissue. The need for alternative treatments against E. coli is due to its ability to resist many conventional antibiotics, which is a huge challenge for curing ill animals. Therefore, the aim of this review was to highlight the pathogenicity of E. coli in the mammary gland, discuss the presence of the new putative pathotype, the mammary pathogenic E. coli (MPEC) pathotype, study the host's immune response, and the alternative treatments that are used against mastitis-associated E. coli.

Virulence Determinants and Plasmid-Mediated Colistin Resistance mcr Genes in Gram-Negative Bacteria Isolated From Bovine Milk

A major increase of bacterial resistance to colistin, a last-resort treatment for severe infections, was observed globally. Using colistin in livestock rearing is believed to be the ground of mobilized colistin resistance (mcr) gene circulation and is of crucial concern to public health. This study aimed to determine the frequency and virulence characteristics of colistin-resistant Gram-negative bacteria from the milk of mastitic cows and raw unpasteurized milk in Egypt. One hundred and seventeen strains belonging to Enterobacteriaceae (n = 90), Pseudomonas aeruginosa (n = 10), and Aeromonas hydrophila (n = 17) were screened for colistin resistance by antimicrobial susceptibility testing. The genetic characteristics of colistin-resistant strains were investigated for mcr-1-9 genes, phylogenetic groups, and virulence genes. Moreover, we evaluated four commonly used biocides in dairy farms for teat disinfection toward colistin-resistant strains. Multidrug-resistant (MDR) and extensive drug-resistant (XDR) phenotypes were detected in 82.91% (97/117) and 3.42% (4/117) of the isolates, respectively. Of the 117 tested isolates, 61 (52.14%) were colistin resistant (MIC >2 mg/L), distributed as 24/70 (34.29%) from clinical mastitis, 10/11 (90.91%) from subclinical mastitis, and 27/36 (75%) from raw milk. Of these 61 colistin-resistant isolates, 47 (19 from clinical mastitis, 8 from subclinical mastitis, and 20 from raw milk) harbored plasmid-borne mcr genes. The mcr-1 gene was identified in 31.91%, mcr-2 in 29.79%, mcr-3 in 34.04%, and each of mcr-4 and mcr-7 in 2.13% of the colistin-resistant isolates. Among these isolates, 42.55% (20/47) were E. coli, 21.28% (10/47) A. hydrophila, 19.12% (9/47) K. pneumoniae, and 17.02% (8/47) P. aeruginosa. This is the first report of mcr-3 and mcr-7 in P. aeruginosa. Conjugation experiments using the broth-mating technique showed successful transfer of colistin resistance to E. coli J53-recipient strain. Different combinations of virulence genes were observed among colistin-resistant isolates with almost all isolates harboring genes. Hydrogen peroxide has the best efficiency against all bacterial isolates even at a low concentration (10%). In conclusion, the dissemination of mobile colistin resistance mcr gene and its variants between MDR- and XDR-virulent Gram-negative isolates from dairy cattle confirms the spread of mcr genes at all levels; animals, humans, and environmental, and heralds the penetration of the last-resort antimicrobial against MDR bacteria. Consequently, a decision to ban colistin in food animals is urgently required to fight XDR and MDR bacteria.

The deletion of yeaJ gene facilitates Escherichia coli escape from immune recognition

Mammary gland-derived Escherichia coli (E. coli) is an important pathogen causing dairy cow mastitis. Mammary gland mucosal immunity against infectious E. coli mainly depends on recognition of pathogen-associated molecular patterns by innate receptors. Stimulator of interferon (IFN) gene (STING) has recently been the dominant mediator in reacting to bacterial intrusion and preventing inflammatory disorders. In this study, we firstly proved that diguanylate cyclase YeaJ relieves mouse mammary gland pathological damage by changing E. coli phenotypic and host STING-dependent innate immunity response. YeaJ decreases mammary gland circular vacuoles, bleeding and degeneration in mice. In addition, YeaJ participates in STING-IRF3 signaling to regulate inflammation in vivo. While in vitro, YeaJ decreases damage to macrophages (RAW264.7) but not to mouse mammary epithelial cells (EpH4-Ev). Consistent with the results in mouse mammary gland, yeaJ significantly activates STING/TBK1/IRF3 pathway in RAW264.7 as well. In conclusion, the deletion of yeaJ gene facilitates E. coli NJ17 escape from STING-dependent innate immunity recognition in vitro and in vivo. This study highlights a novel role for YeaJ in E. coli infection, which provides a better understanding of host-bacteria interactions and potential prophylactic strategies for infections. IMPORTANCE E. coli is the etiological agent of environmental mastitis in dairy cows, which cause massive financial losses worldwide. However, the pathophysiological role of yeaJ in the interaction between E. coli and host remains unclear. We found that YeaJ significantly influences various biological characteristics and suppresses severe inflammatory response as well as greater damage. YeaJ alleviates damage to macrophages (RAW264.7) and mouse mammary gland. Moreover, these effects of YeaJ are achieved at least partial by mediating the STING-IRF3 signaling pathway. In conclusion, the deletion of yeaJ gene facilitates E. coli NJ17 escape from STING-dependent innate immunity recognition in vitro and in vivo. This study is the basis for further research to better understand host-bacteria interactions and provides potential prophylactic strategies for infections.

Bacteriophage Cocktails Protect Dairy Cows Against Mastitis Caused By Drug Resistant Escherichia coli Infection

Mastitis caused by Escherichia coli (E. coli) remains a threat to dairy animals and impacts animal welfare and causes great economic loss. Furthermore, antibiotic resistance and the lagged development of novel antibacterial drugs greatly challenge the livestock industry. Phage therapy has regained attention. In this study, three lytic phages, termed vB_EcoM_SYGD1 (SYGD1), vB_EcoP_SYGE1 (SYGE1), and vB_EcoM_SYGMH1 (SYGMH1), were isolated from sewage of dairy farm. The three phages showed a broad host range and high bacteriolytic efficiency against E. coli from different sources. Genome sequence and transmission electron microscope analysis revealed that SYGD1 and SYGMH1 belong to the Myoviridae, and SYGE1 belong to the Autographiviridae of the order Caudovirales. All three phages remained stable under a wide range of temperatures or pH and were almost unaffected in chloroform. Specially, a mastitis infected cow model, which challenged by a drug resistant E. coli, was used to evaluate the efficacy of phages. The results showed that the cocktails consists of three phages significantly reduced the number of bacteria, somatic cells, and inflammatory factors, alleviated the symptoms of mastitis in cattle, and achieved the same effect as antibiotic treatment. Overall, our study demonstrated that phage cocktail may be a promising alternative therapy against mastitis caused by drug resistant E. coli.

Application of a simple measuring method to evaluate the fecal microflora of dairy cows in the summer season

OBJECTIVE

The effect of seasonality needs to be considered in designing future studies because global warming has caused a rise in ambient temperatures. The objective of the present study is to investigate the effect of high ambient temperatures on fecal score and fecal microflora in dairy cows during summer.

MATERIALS AND METHODS

During the 7 days before the sampling of feces, the daily mean temperatures were 19.9°C in early summer and more than 27.5°C in late summer. Fecal samples were collected from the rectum of cows and the fecal score was evaluated on a 4-point scale. The equalized samples were used to extract the genomic deoxyribonucleic acid (DNA) of the bacteria (Escherichia coli, Salmonella, Lactobacillus, and Bifidobacterium).

RESULTS

There was no significant difference in fecal scores between the sampling times in early and late summer. In the populations of the bacteria, there was no significant difference between sampling days in the DNA level of Salmonella, and E. coli in late summer increased to more than three times the level in early summer. However, both levels of Lactobacillus and Bifidobacterium in early summer significantly decreased after 2 months.

CONCLUSION

These data suggest that the increase in temperature in late summer may adversely affect the populations of bacteria in the intestinal environment of dairy cows. In addition, the method used in the present study was sufficient to evaluate the changes in internal and external environmental conditions of dairy cattle.