Antimikrobna osetljivost bakterija mlečne kiseline izolovanih iz Somborskog sira

Extensive literature data pointed out that some lactic acid bacteria (LABs), the predominant microbiota in fermented dairy products, may serve as reservoirs of antibiotic resistance genes potentially transferable to human pathogens. Hence, there is a growing interest in the possible role of LAB as vectors of antibiotic resistance determinants. This paper reports the susceptibility patterns of a number of LAB species (belonging to the genera Lactococcus, Lactobacillus, and Enterococcus) isolated from different batches of autochthonous Sombor cheese, traditionally made without the addition of starter cultures, and currently proposed as a candidate for PDO/PGI designation. The experimental work was performed to select strains that do not contain antibiotic resistance genes among those with desirable technological characteristics such as rapid acidification, proteolysis, ability to metabolise citrate and form aromogenic compounds. In addition, the results of these screening procedures could also indicate the types and degrees of antimicrobial resistance already present among the LAB community of Sombor cheese, which according to their geographically restricted areas of production, specific manufacturing process and characteristic aroma and appearance, represent a distinct ecological niche.Opsežni literaturni podaci ukazuju da pojedine bakterije mlečne kiseline, čineći dominantnu mikrofloru u fermentisanim proizvodima od mleka, mogu poslužiti kao rezervoar gena rezistencije na antibiotike, potencijalno prenosivih na patogene mikroorganizme. Stoga postoji rastući interes o mogućoj ulozi bakterija mlečne kiseline kao vektora determinanti rezistencije. Ovaj rad izveštava o profilima antibiotske osetljivosti vrsta bakterija mlečne kiseline (rodovi Lactococcus, Lactobacillus i Enterococcus) izolovanih iz različitih linija proizvodnje autohtonog Somborskog sira, tradicionalno proizvedenog bez dodatka starter kulture, a predloženog za dobijanje oznake geografskog porekla. Eksperimentalni rad je izveden u cilju selekcije sojeva koji ne sadrže gene rezistencije na antibiotike, ali su ujedno nosioci poželjnih tehnoloških karakteristika kao što su brza acidifikacija, proteoliza, sposobnost metabolisanja citrata i formiranje aromogenih komponenti. Ujedno, rezultati ovih 'screening' procedura mogu ukazati na tip i stepen antimikrobne rezistencije prisutne među zajednicom bakterija mlečne kiseline Somborskog sira, koji prema geografski određenom području proizvodnje, specifičnom procesu proizvodnje i karakterističnoj aromi i izgledu predstavlja zasebnu ekološku nišu

Nova metoda za dokazivanje antibiotika u mlijeku

Dokazivanje antibiotika u mlijeku je neophodan način kontrole ispravnosti mlijeka, a prema našim propisima ovaj postupak je i obavezan. Nedostatak jednostavnih i brzih metoda za dokazivanje antibiotika u mlijeku predstavlja glavnu prepreku za redovnu i pravilnu kontrolu mlijeka na prisustvo antibiotika

Proving of the bacterial metabolites in hygienic control of the cooled milk - I Piruvate

Broj mikroorganizama u hlađenom mlijeku ustanovljen je indirektno određivanjem piruvata. Rezultati kontinuirane i manualne analize pokazali su praktičnost i brzinu opisane metode.Number of microorganisms in the cooled milk was estimated indirectly by determination of pyruvate. Practicality and rapidity of described methods were of continues and manual analyses

Rizik prisustva stafilokoka u sirevima

Coagulase positive staphylococci isolated from autochthonous cheeses were screened regarding their enterotoxigenic potential and antimicrobial resistance profile. By applying the VIDAS techology, out of 73 coagulase positive staphylococcal isolates, 22 (30,14%) strains showed enterotoxigenic potential. The 50% analysed strains showed antimicrobial resistance properties at least at one of antibiotics tested, and among those resistant population 54,54% strains were characterized by multiple resistance. The obtained results presented the strong argument in risk characterization.Koagulaza pozitivni sojevi izolovani iz autohtonih sireva su okarakterisani u odnosu na njihov enterotoksogeni potencijal i profil fenotipske antimikrobne rezistencije. Primenom VIDAS tehnologije, od 73 koagulaza pozitivna soja stafilokoka analiziranih u našem radu, potencijal produkcije enterotoksina je pokazalo 22 (30,14%) sojeva. Rezistencija na jedan ili više odabranih antibiotika je utvrđena kod 11 (50%) sojeva, od kojih se 6 (54,54%) karakterisalo svojstvom multiple rezistencije. Svojstvo enterotoksogenosti i antimikrobne rezistencije ispitivanih koagulaza pozitivnih stafilokoka predstavlja snažan argument u karakterizaciji rizika njihovog prisustva u sirevima

Fiziološke karakteristike psihrotrofnih bacila izolovanih iz sirovog mleka

The strains of genus Bacillus are often present as containments in raw milk. Their ubiquitous nature, potentiality to produce thermorcsistent spores, ability to grow and bio­chemical activity at low temperatures, so as pathogenicity of some strains have actualized their significance in food industry. The isolation of psychrotrophic bacilli was conducted after incubation of 10 days at 7±1°C (isolation is achieved only from milk samples which demonstrate the changes of Bacillus number at the start and after 10 days of incubation at 7±1°C). It was examined 56 psychrotrophic strains of bacilli isolated from raw milk. During incu­bation of 10 days at 7±1°C, in 50 samples of raw milk the number of bacilli increased from log 0.8±0.78 to 1.73±0.86, whereas in 6 samples the Bacillus number ranged from log 0.10±0.01 to 2.07±0.47. The differences between mean values of Bacillus number on the first and tenth days of incubation at low temperatures (psychrotrophic condition) were subjected to the t-test. It was noticed a highly significant difference. It was also found that 30.35% of isolated strains were heamolytic, 64.28% degraded lechitin, 5.35% broke down gelatin, 78.57%; de­graded casein. A high percentage of isolated bacilli (97.07%) grew at pH 5.7 and 78.57% multiplied in the presence of 7% NaCl.Predstavnici roda Bacillus često su prisutni kao kontaminenti u sirovom mleku. Njihova ubikvitarnost, stvaranje tennorezistentnih spora, sposobnost rasta i biohemijska aktivnost pri niskim temperaturama kao i patogenost pojedinih sojeva aktueliziraju njihov značaj u industriji hrane. Izolacija psihrotrofnih bacila je izvedena posle inkubacije sirovog mleka ud 10 dana na 7±1°C. Psihrotrofni bacili su izolovani samo iz uzoraka koji su pokazivali promenu broja bacila na početku inkubacije I posle 10 dana inkubacije na 7±1°C. Testirana su 56 psihrolrofna soja bacila izolovana iz sirovog mleka. Broj bacila se tokom inkubacije od 10 dana na 7±1°C u 50 uzoraka sirovog mleka povećao sa log0.81±0.78na 1.73±0.86, au6uzorakasa log 0.10±0.10na 2.07±0.47. Statistički je utvrđeno da je promenu broja bacila u uslovima niskih temperatura za period od 10 dana visoko značajna. Izolovani psihrotrofni bacili su u 30,35% hemolitični, 64,28% ledtinaza pozitivni, 5,35% sojeva razlaže želatin, a 78,57% sojeva razlazu kazein. Sposobnost rasta u medijumu sa pH 5,7 pokazuje 97.07% sojeva, a 78,57% raste u prisustvu 7% NaCl

Staphylococcus presence into the milk and problems of the milk control in business

Osnova problema stafilokoka pri kontroli mlijeka proizlazi iz visoke frekvencije nalaza koagulaza pozitivnih stafilokoka u mlijeku (6, 7, 8), razmjerno česte enterotoksičnosti (2, 3, 5) izoliranih sojeva i termostabilnosti enterotoksina. Za nastajanje trovanja ljudi enterotoksičnim stafilokokama potreban je visok broj stafilokoka koji se stvara u neodgovarajućim uvjetima čuvanja i transporta mlijeka. Čuvanjem mlijeka ohlađenog odmah posle dobivanja na 4 °C i 10 °C TN-aza i enterotoksin nisu dokazani u intervalu od 48 sati, ni pri visokim početnim populacijama stafilokoka. Čuvanjem mlijeka 9 sati na 25 °C enterotoksin i TN-aza su pozitivni. U mlijeku hlađenom 5 sati posle muže TN-aza se dokazuje posle 24 i 36 sati u zavisnosti od početne kontaminacije. Iz iznijetih rezultata može se zaključiti da pri nepravilnoj primarnoj obradi mlijeka postoje uvjeti za stvaranje dovoljnih količina enterotoksina koje mogu izazvati trovanja kod ljudi. TN-aza testom mogu se otkriti uzorci u kojima je enterotoksin na nivou detekcije.A basic problem dealing with the control of milk referes to the high frequency by which the coagulase of the positive staphilococci is found in milk (6, 7, 8) as related to the enterotoxicity (2, 3, 5) of the isolated strains and the thermolability of enterotoxines. A high count of staphilococci is necessary to get people poisoned by enterotoxic staphilococci which use to grow under inadequate milk storage and transport conditions. By storing milk cooled down to 4 °C and 10 °C just after it was milked, no TN-ase and enterotoxine were recorded within 48 hours, even not in cases when a high initial population of staphilococci was observed. By storing milk for 9 hours at 25 °C the enterotoxines and TN-ase were positive. In milk, cooled for 5 hours after milking, a TN-ase was observable after 24 an 36 hours dependent on the value of the initial contamination. From the results presented the conclusion can be drawn that an incorrect processing of milk help to create conditions favouring formation of a sufficient quantity of enterotoxins capable of getting people poisoned. By a TN-ase test it was possible to screen out samples indicative of enterotoxines the quantity of which was recorded on the detection level

Sirovo mleko kao izvor Bacillus vrsta odgovornih za kvar proizvoda od mleka

Bacillus spp. are often present as contaminants in raw milk. Due to thermo resistance of their spores, bacilli survive after the heat treatment in milk industry. The proteolytic activity of bacilli leads to spoilage of milk and milk products and according to that influenced the durability of milk product. The material of investigation consisted of 243 samples of raw milk, 40 samples of pasteurized milk and corresponding 40 samples of raw milk during the milk pasteurization and 60 samples of pasteurized milk on expiry date. The proteolytic activity of bacilli was determined according to modified method that is established by Hill and Gasson (1986). The level of Bacillus spp. contamination of raw milk was 2,76±0,72 log10 cfu/ml, 1,74±2,52 log10 cfu/ml for pasteurized during production process, and level of Bacillus spp. contamination of final product-pasteurized milk was 2,38±0,47 log10 cfu/ml. It was determined the presence of following species: B. licheniformis 46,15%, B. pumilus 15,38%, B. subtilis 15,38%, B. brevis 11,54%, B. sphaericus 7,69%, B. cereus 3,85% in raw milk and B. subtillis 71,42%. B. pumilus 14,28% i B. licheniformis 14,28% in pasteurized milk during the production process. Isolated strains of Bacillus spp. showed significant proteolytic activity which have influenced the durability of pasteurized milk.Bacillus spp. su često prisutni kontaminenti sirovog mleka. S obzirom na termorezistent njihovih spora opstaju pri termičkim tretmanima u mlekarskoj industriji. Njihova proteolitička aktivnost dovodi do kvara mleka i time utiče na smanjenu održivost proizvoda od mleka. U radu smo ispitali zastupljenost bacila u sirovom mleku, uticaj temperatura pasterizacije na redukciju bacila u termički obrađenom mleku, kao i proteolitičku aktivnost izolovanih sojeva. Materijal su predstavljala 243 uzorka sirovog mleka, 40 uzoraka pasterizovanog i paralelnih 40 uzoraka sirovog mleka tokom procesa pasterizacije i 60 uzoraka pasterizovanog mleka na kraju perioda održivosti. Proteolitička aktivnost Bacillus spp. određivana je na kazeinskom agaru kao "screening" metoda, a analiza proteolitičke aktivnosti celih ćelija Bacillus spp. u odnosu na proteinske supstrate je vršena modifikovanom metodom koju su razvili Hill i Gasson (1986). Nivo kontaminacije sirovog mleka sa Bacillus spp. je iznosi 2,76±0,72 log10 cfu/ml, pasterizovanog mleka tokom procesa proizvodnje 1,74±2,52 log10 cfu/ml, dok je nivo kontaminacije upakovanog pasterizovanog mleka sa Bacillus spp. iznosio 2,38±0,47 log10 cfu/ml. Identifikacijom sojeva Bacillus spp. izolovanih iz sirovog mleka ustanovljeno je prisustvo: B. licheniformis sa 46,15%, B. pumilus sa 15,38%, B. subtilis sa 15,38%, B. brevis sa 11,54%, B. sphaericus sa 7,69 i B. cereus sa 3,85%, a u pasterizovanom mleku tokom procesa proizvodnje ustanovljeno je prisustvo B. subtillis 71,42%. B. pumilus 14,28% i B. licheniformis 14,28%. Izolovani sojevi Bacilus spp. pokazali su izrazitu proteolitičku aktivnost što za posledicu ima smanjenje održivosti i kvar pasterizovanog mleka

Safety evaluation of Sjenica cheese with regard to coagulase-positive staphylococci and antibiotic resistance of lactic acid bacteria and staphylococci

Sjenica cheese is an artisanal cheese stored in brine, traditionally produced from raw sheeps milk in the southern part of Serbia - Sjenica Pester plateau. The aim of this study was to perform the safety evaluation of Sjenica cheese. As one of the safety criteria we considered the number of coagulase positive staphylococci and their enterotoxigenic potential. Antibiotic susceptibility/resistance patterns of autochthonous lactic acid bacteria and coagulase-positive staphylococci isolated from Sjenica cheese was also investigated. During the monitoring period of the cheese-making process, coagulase positive staphylococci did not reach the value of 10(5) cfu/g. Among coagulase positive staphylococci, 12 (46,15%) isolates showed enterotoxigenic potential and were identified as Staphylococcus intermedius (11 isolates) and Staphylococcus aureus (1 isolate). Vancomycin resistance was the most prevalent phenotypic resistance profile in coagulase positive staphylococci. Lactococci present the most dominant population among lactic acid bacteria. The most prevalent resistance phenotype in lactococci was resistance to streptomycin (83.33%), ampicillin and penicillin (70.83%); lactobacilli were characterized by resistance to vancomycin (62.5%) and tetracycline (54.17%), while resistance to streptomycin (82.46%) was the most prevalent phenotypic profile in enterococci. All coagulase positive staphylococci and lactic acid bacteria isolates that showed resistance to tetracycline on disc diffusion and E-test, were tested for the presence of ribosomal protection proteins, tet(M) and tet(K) genes. All isolates were positive for ribosomal protection proteins genes; 14 (60.87%) isolates showed tet(M) gene presence, while 2 lactobacilli isolates revealed the presence of tet(K) gene

Production technology of Kajmak (cream) and some problems of quality standardization

Kajmak je proizvod od mlijeka prijatnog kiselkastog ukusa sa visokim procentom masti i značajnim procentom bjelančevina. Danas se kajmak proizvodi u nekontroliranim uvjetima pa je njegova kvaliteta često neujednačena. Za kvalitetu kajmaka značajni su postotak suhe tvari i masti, koje su se u istraživanih 208 uzoraka kajmaka kretali od 60,75± 4,36% za suhu tvar i 84,48 ± 5,64% za mast u suhoj tvari sa koeficijentom varijacije 7. Suha tvar bez masti kretala se u velikom rasponu sa koeficijentom varijacije od 52, što ukazuje na neujednačenost proizvodnje. U daljnjem radu neophodno je utvrditi kako poleđine faze proizvodnje kajmaka utječu na njegov sastav."Kajmak" is milk product of pleasant sourish flavor containing much fat. Uncontrolled condition of current production of "kajmak" is often the cause of its quality variation. The quality of "kajmak" depends on total solids and fat contents. Total solids in 208 examined samples attained 60.75 ± 4.36% and fat content 84.48 ± 5.64% (coefficient of variation 7). Solids non fat ranged considerably coefficient of variation being 52, and indicating excessive quality variation. Further study is necessary to explain the influence of some production phases on "kajmak\u27s" structure

Nalaz i aktivnost bakterija mlečne kiseline u autohtonom sjeničkom siru

In this article the prevalence of lactic acid bacteria through the production and ripening period of autochthonous Sjenica cheese was reviewed. The activity of main LAB group was evaluated by pH changes and evolution of ripening coefficient.U radu je prikazana prevalenca bakterija mlečne kiseline tokom procesa proizvodnje i zrenja autohtonog sjeničkog sira. Aktivnost bakterija mlečne kiseline je procenjena na osnovu promene pH vrednosti i koeficijenta zrelosti tokom perioda zrenja od 90 dana