The aim of this article was to provide an overview on the current status of fruit tree diseases caused by Pseudomonas syringae, their importance and distribution, epidemiology and control possibilities with emphasis on plums and cherry. The plant diseases caused by Pseudomonas syringae are economically important and occur worldwide on large diversity of plants. On stone fruits, diseases caused by different pathovars of Pseudomonas syringae are economically important in major fruit growing regions. The severity of damages and economic importance depends on the geographical region, host plant species and pathovar of P. syringae involved in the disease. Bacterial canker induced by P. syringae pv. syringae on all commercially grown stone fruit species and by pv. morsprunorum predominantly on cherries and plums is considered to be the most serious one. Bacterial decline caused by P. syringae pv. persicae is severe on nectarine and peach. Despite the wide spread and economic importance in the most stone fruit growing areas the diseases caused by Pseudomonas syringae in some areas, e.g. Baltic States, are poorly studied, and the data on distribution and pathovars involved in the diseases observed are still missing.

The present study describes situation of antimicrobial resistance of animal pathogens and resistance trends in Estonia in years 2006-2009. Bacterial strains isolated during period 2006-2009 were Escherichia coli (E. coli), Enterococcus faecium (E. faecium), Enterococcus faecalis (E. faecalis), collected from healthy pigs faeces as well as from diagnostic submissions of pig samples. Staphylococcus aureus (S. aureus) isolates originated from cows with clinical mastitis and Staphylococcus pseudointermedius (S. pseudointermedius) isolates from dogs with pyoderma or otitis externa. Antimicrobial susceptibility was detected by microdilution method. Normal enteric microflora from health y pigs had resistance against streptomycin, tetracyclin, sulfametoxazol and trimethoprim. E. faecalis and E. faecium were resistant to erythromycin, tetracyclin, streptomycin and kanamycin. Multiresistance occured mainly against kanamycin, streptomycin and tetracyclin. E. coli strains isolated from pathological material showed high resistance to ampicillin, tetracycline, streptomycin, sulphonamides and trimethoprim. Multiresistance was detected between 60–73% during study years. In 2009, one ESBL (extended spectrum betalactamase) producing isolate was observed. S. aureus strains isolated from clinical mastitis samples were mainly penicillin resistant (58–86%). Meticillinresistant S. aureus was not found during the study. In 2009, resistance to lincomycin (30%) and fucidinic acid (22%) was detected. In S. pseudointermedius strains isolated from canine skin samples the prevalence of resistance to penicillin as high as 53–81% was found. Multidrug resistance was relatively stable being 38% in 2006, 29% in 2007 and 25% in 2009. In conclusion, antimicrobial resistance of animal pathogens in Estonia was high. Further improvement of prudent use of antimicrobials and infection control is needed.

The objective of the present study was to investigate the microbiological content of cows’ milk in Latvia’s organic farms with a purpose to detect potential microbiological threats in milk. Samples were collected in December 2011 at 12 biological dairy farms of Latvia. Raw milk samples (N=155) obtained from cow composite milk were studied. The total mesophilic aerobic and facultative anaerobic microorganisms (MAFAM), the presence of coliforms and coagulase-positive staphylococci, count of yeasts and moulds were analysed using standard methods. Of the sampled cows 50% had a low somatic cell count (SCC) (LESS THAN 200,000 cells mLE-1), 23% - high, but 27% had a very high SCC (greater than 500,000 cells mLE-1). The mean value of MAFAM in the samples with low, high and very high SCC was 4.7, 5.0 and 5.0 log10 colony forming units (cfu) mLE-1, respectively. The yeasts were present in 57% of milk samples with the mean concentration of 3.1 log10 cfu mLE-1. Moulds were found in 27% of all milk samples; their mean concentration was 4.4 log10 cfu mLE-1. Identified mould strains belonged to genera Absidia, Aspergillus, Geotrichum, Mucor and Penicillium. In cases of subclinical mastitis and latent mammary infection the most distributed mastitis pathogens were Staphylococcus aureus, Micrococcus kristinae, Bacillus cereus and coagulase negative staphylococci.

Wheat crown rot is a harmful disease that can be caused by different pathogens. The control of this disease is complicated because of the diversity of pathogens and an insufficient efficacy of fungicides; therefore, the agronomic practices of wheat production are an important tool for reducing the disease development. The aim of this study was to estimate the incidence of wheat crown rot depending on soil tillage system and on the pre-crop of wheat in the year 2016. The field experiment was carried out at the Research and Study farm ‘Peterlauki’ of the Latvia University of Agriculture in the autumn of 2008. The data obtained in 2016 are analysed in this study: A – soil tillage system: 1 – traditional soil tillage with ploughing at the depth of 22 – 24 cm, 2 – reduced soil tillage with disc harrowing up to the depth of 10 cm; B – pre-crop of winter wheat: 1 – wheat, 2 – oilseed rape, 3 – faba beans. The incidence of crown rot was not influenced by soil tillage system, but the impact of pre-crop was significant (p = 0.006). The level of disease was essentially higher in continuous wheat sowings. The experiments showed that the main causal agents of the disease were Fusarium spp. and Oculimacula spp. The spectrum of pathogens was not dependent on a particular agronomic practice.

The aim of this study was to investigate the patterns of antibiotic resistance of Aeromonas spp. bacteria isolated from the sea trout (Salmo trutta) from the state fish hatcheries of the Institute of Food Safety, Animal Health and Environment ‘BIOR’, Latvia. Bacteriological investigations were performed at four state fish hatcheries located in the drainage basins of the main Latvian rivers – Daugava, Venta and Gauja, during the five-year period (2012 – 2016). In fish with visible clinical signs, bacteriological samples were collected from heart, liver, spleen, kidney and ulcer surfaces. Aeromonas hydrophila and Aeromonas salmonicida were isolated from sea trouts. A total of 52 individual sea trouts were examined. Resistance to amoxicillin, ampicillin, cephalexin, colistin, doxycycline, enrofloxacin, erythromycin, florfenicol, gentamycin, kanamycin, lincomycin, neomycin, oxytetracycline, spectinomycin, streptomycin, tetracycline, trimethoprim/sulfamethoxazole was tested. The results of this study suggest a multi-drug resistance pattern among the A. hydrophila isolates. All the isolates were resistant to amoxicillin (100%), ampicillin (100%), cephalexin (100%) and erythromycin (100%). The lowest level of resistance was found against florfenicol (4.55%), gentamycin (4.55%), kanamycin (4.55%), but susceptibility was recorded to enrofloxacin, neomycin and trimethoprim/sulfamethoxazole. A. salmonicida isolates were resistant to oxytetracycline (9.38%) and tetracycline (9.38%). For other antibiotics A. salmonicida isolates were susceptible.

Rhododendron spp. plants were surveyed for Phytophthora infection in Lithuania during 2010 – 2016. This study aims to identify Phytophthora genus pathogen which infects rhododendrons in Lithuania. Samples were taken from young sick plants with visible infection symptoms. Soil sampling was performed from the rhizosphere of sick plants. DNA from soil and plant was tested for the presence of Phytophthora genus pathogens. Data showed positive results of Phytophthora genus specific probe during real-time PCR. All tested diseased leaves and soil samples have indicated Phytophthora sp. infection during Alert-LF® Phytophthora spp. analysis. The extracted DNA concentrations were not very high for Phytophthora species identification, but in most cases, it was high enough for further researches.

The aim of the study was to assess the ability of pathogens metabolic repair from injury within 10 days of refrigerated storage of milk after high pressure treatment. Two pathogenic strains – Listeria monocytogenes ATCC 7644 (LM) and Escherichia coli ATCC 25922 (EC) were inoculated in ultrahigh-temperature treated (UHT) milk at concentration of about 107 CFU mLE-1 and treated at 400, 500, 550, and 600 MPa for 15 min with inlet temperatures 20 °C, and then stored at 4 ± 2 °C to evaluate survival and growth of pathogens. By increasing the applied pressure, an increased rate of the pathogens’ inactivation was achieved. After 10 days of storage, milk treated at 400 MPa showed growth over 3.5 log CFU mLE-1 of L. monocytogenes and 1.7 log CFU mLE-1 of E. coli. In 550 MPa and 600 MPa treated milk samples after 8 and 10 days of storage colony formation occurred (3 CFU mLE-1 (550 LM) and 2 CFU mLE-1 (550 EC, 600 LM and 600 EC)). Although high pressure treatment is effective method for reducing of pathogenic bacteria, the metabolic repair from injury of bacterial cells in milk during storage should be considered.

Studies were conducted at the experimental station of the Stavropol State Agrarian University on leached chernozem, powerful, low-humus heavy loam on loess-like loam in 2017. The goal was to study the effect of the introduction of rocks rich in chemical composition (limestone-shell rock, apatite and phosphogypsum), both separately and jointly, on the microbial phase of the soil. The determination of the number of microorganisms was produced on dense nutrient medium by direct counting of colonies. It was found that the amount of ammonifiers under the control was 37 ml CFU gE−1 (colony-forming units), increasing 1.3–1.5 times with separate use and 2.5–3 times with the joint use of rocks. Similar changes were observed with respect to the number of nitrifiers and aerobic nitrogen fixers of the type Azotobacter. The number of cellulose-depleting microorganisms in the remineralization variants reached 220,00–230,00 CFU gE−1 compared to 115,00 CFU gE−1 under the control. With the introduction of separate rocks, there was a decrease in the occurrence of pathogens, while with a joint introduction they were not detected. The frequency of occurrence of toxin formers, such as Aspergillus and Penicillium, reached 100% at the control and decreased by 20–40% at the experimental variants. It was revealed that the introduction of shell limestone, apatite and phosphogypsum had an effect on the increase in the number of soil microbiota of various physiological groups. Among the fungal microflora, the number of pathogens and toxin formers decreases and the number of pathogen antagonists increases.

Natural defence mechanisms of the mammary gland tissues play a vital role in protecting the gland from infections. The progress of mammary infection depends on the ability of bacterial pathogens to adapt to milk and udder tissues, and on the various virulence factors they activate, as well as on the cow's response. The levels of immunoglobulins (lg) and lactoferrin (Lf) concentration in the milk from dairy cows with and without subclinical mastitis were determined. In this investigation it was stated that 82.5% of samples were negative, but 17.5% of samples were positive for pathogens. Cows had subclinical mastitis caused by Coagulase negative staphylococci observed in 48.60%, Streptococcus uberis - 32.10%, Staphylococcus aureus - 18.90% of cases in milk samples. There were no significant differences between all classes of immunoglobulins concentration in the milk without pathogens and with pathogens. The lactoferrin concentration was significantly increased for 40.33% in the milk with pathogens.

Pyrenophora tritici-repentis is a major wheat pathogen in all wheat (Triticum spp.) growing areas worldwide. Up to date, eight P. tritici-repentis races have been described based on chlorosis, necrosis, or both symptoms caused on race differential wheat genotypes: ‘Glenlea’, 6B662, 6B365, and ‘Salamouni’. Symptom development on differential genotypes depends on the interaction of the pathogen’s necrotrophic effectors named Ptr ToxA, Ptr ToxB, and Ptr ToxC with host susceptibility genes. Ptr ToxA is encoded by the single copy gene ToxA and induces necrosis on sensitive wheat cultivars. Ptr ToxB causes chlorosis and is encoded by the multicopy gene ToxB. The Ptr ToxC is the non-proteinaceous, polar, low molecular mass molecule that also induces chlorosis, but up to date, the gene encoding this toxin is unknown. Races producing Ptr ToxA are predominant in the global Ptr population. There are several reports about new putative races of P. tritici-repentis that do not conform to the current race system, so further research is required. This study aims to collect and systematise available information about the virulence and races of P. tritici-repentis.