Prisustvo sojeva stafilokoka rezistentnih na meticilin kod studenata Fakulteta veterinarske medicine Univerziteta u Beogradu

Resistance to methicillin in staphylococci is considered to be one of the most dangerous forms of bacterial resistances to antibiotics. Methicillinresistant staphylococci (MRS) are zoonotic agents which cause local and systemic infections in humans and animals, often with a fatal outcome due to the absence of adequate antibiotic therapy. People colonized with strains of MRS are asymptomatic carriers and reservoirs of these strains in human populations. The aim of this research was to determine the prevalence of strains of MRS among clinically healthy students of the Faculty of Veterinary Medicine in Belgrade. The study was conducted on 100 volunteers: 62 males and 38 females. Given that staphylococci are expected to be found in the highest percentage in the nose and on the armpit skin, the swabs were taken from these regions of each person. Blood agar was innoculated immediately on taking the swabs After the incubation and isolation, the staphylococci were identified to species level. Their susceptibility to methicillin was tested in a disk-diffusion test with cefoxitin. All strains which were found to be resistant to cefoxitin were investigated for the presence of mecA gene with PCR. Staphylococci were isolated in 146 out of the 200 swabs taken: there were 79 nose swabs and 67 axillar swabs positive for these bacteria. Seventeen isolates were resistant to cefoxitin and the presence of the mecA gene was confirmed in seven, four of which were taken from the nose and three from the axillary region. The results of this research show that, being 6%, the prevalence of mecA-positive staphylococci in the population of clinically healthy students of veterinary medicine is significant. The percentage of methicillin-resistant staphylococci was higher in nose than in the axillar region of the students.Rezistencija na meticilin kod stafilokoka smatra se jednim od najopasnijih oblika rezistencije bakterija na antibiotike. Sojevi meticilin rezistentnih stafilokoka (MRS) pripadaju zoonotskim agensima i uzročnici su lokalnih i sistemskih infekcija kod ljudi i životinja, često sa fatalnim ishodom zbog nedostatka efikasne terapije. Ljudi kolonizovani sojevima MRS su asimptomatski nosioci i predstavljaju rezervoare ovih sojeva u humanoj populaciji. Cilj ovog istraživanja je bio da se utvrdi prevalencija izolata MRS kod klinički zdravih studenata Fakulteta veterinarske medicine u Beogradu. U istraživanje je bilo uključeno 100 studenata - dobrovoljaca, 62 muškog i 38 ženskog pola. Brisevi su uzimani iz nosa i pazuha zato što su stafilokoke u najvećem procentu zastupljene u tim regijama. Brisevi su odmah zasejavani na krvni agar. Nakon inkubacije i izolacije, izvršena je identifikacija stafilokoka do vrste. Ispitivanje osetljivosti stafilokoka na meticilin izvedeno je primenom disk difuzione metode sa cefoksitinom. Svi sojevi rezistentni na cefoksitin ispitani su na prisustvo mecA gena metodom lančane reakcije polimeraze (PCR). Od ukupno 200 uzetih briseva izolovano je 146 izolata stafilokoka, 79 iz briseva nosa i 67 iz briseva pazušne regije. Kod 17 izolata ustanovljena je rezistencija na cefoksitin, a kod 7 je utvrđeno prisustvo mecA gena. Četiri mecA pozitivna izolata su poticala iz briseva nosa, a 3 sa kože pazušne regije. Utvrđena prevalencija meticilin-rezistentnih stafilokoka kod klinički zdravih studenata Fakulteta veterinarske medicine od 6%, procenjena je kao značajna. Veća učestalost stafilokoka rezistentnih na meticilin ustanovljena je na sluzokoži nosa u odnosu na kožu pazuha

Otkrivanje prisustva PBP2a (Penicillin-binding proteina 2a) i mecA gena kod meticilin rezistentnih Stafilokoka poreklom od životinja

For the purpose of detecting methicillin (oxacillin) resistance in staphylococcal strains, in a number of microbiological laboratories only disc diffusion method with cefoxitin and/or oxacillin discs is used. Besides this method, it is desirable to determine MIC values for cefoxitin and/or oxacillin. After examination by disc diffusion and dilution methods, latex agglutination is used for the detection of PBP2a and PCR is used for the detection of mecA gene. Use of PCR is not possible in a large number of diagnostic laboratories and as method of choice, latex agglutination test for rapid detection of PBP2a is recommended. In this investigation, as confirmatory methods, latex agglutination and PCR were used for strains that were resistant to oxacillin and/or cefoxitin by disc diffusion and broth microdilution methods. In total, 14 strains of coagulase-negative staphylococci originating from clinical specimens of cats, dogs and chicken were examined. Among isolated strains, it was established that the dominating species was Staphylococcus haemolyticus with 11 isolated strains. Other isolated species were Staphylococcus epidermidis, Staphylococcus capitis and Staphylococcus vitulinus, each with one isolated strain. For all 14 strains, oxacillin MIC values ranged from 0.5 μg/mL to >64 μg/mL and cefoxitin MIC values ranged from 1 μg/mL to >256 μg/mL. Positive agglutination reaction by latex agglutination test was recorded in 13 out of 14 strains. The PCR assay for mecA gene was positive in 12 investigated strains.Radi otkrivanja meticilin (oksacilin)-rezistentnih sojeva stafilokoka u većini mikrobioloških laboratorija koristi se najčešće samo disk difuziona metoda uz primenu antibiogram diskova oksacilina i cefoksitina. Pored navedene metode, poželjno je da se utvrde i vrednosti MIC oksacilina i/ili cefoksitina primenom dilucione metode u bujonu ili agaru. Nakon ispitivanja pomenutim metodama za definitivno utvrđivanje pripadnosti soja grupi meticilin rezistentnih stafilokoka, koriste se metoda lateks aglutinacije za utvrđivanje prisustva PBP2a i PCR metoda za detekciju mecA gena. Kako primena metode PCR nije moguća u većini laboratorija koje se bave rutinskom dijagnostikom, kao metoda izbora preporučuje se lateks aglutinacioni test za brzo otkrivanje PBP2a. U ovom ispitivanju primenjeni su lateks aglutinacioni test i PCR metod, kao potvrdne metode za ispitivanje sojeva stafilokoka koji su bili rezistentni na oksacilin i/ili cefoksitin na osnovu rezultata dobijenih disk difuzionom metodom i mikrodilucionom metodom u bujonu. Ukupno je ispitano 14 sojeva koagulaza - negativnih stafilokoka izolovanih iz kliničkih uzoraka poreklom od pasa, mačaka i kokoši. Među izolovanim sojevima, ustanovljeno je da dominira vrsta Staphylococcus haemolyticus sa 11 izolata, a po jedan soj je izolovan od vrsta Staphylococcus epidermidis, Staphylococcus capitis i Staphylococcus vitulinus . Vrednosti MIC oksacilina za 14 sojeva iznosile su od 0.5 mg/mL do >64 mg/mL, a vrednosti MIC cefoksitina iznosile su od 1 mg/mL do >256 mg/mL. Kod 13 od 14 sojeva utvrđena je pozitivna reakcija aglutinacije primenom lateks aglutinacionog testa. Kod 12 ispitivanih sojeva je utvrđeno prisustvo mecA gena PCR metodom

Otpornost na antibiotike kod bakterija izolovanih od riba iz Srbije

Introduction. Bacteria isolated from skin, gills, and fish intestines from aquaculture ponds, ornamental fish stores/aquariums and live fish markets were investigated. Materials and Methods. Disk diffusion and E-test were used for susceptibility testing to carbapenems, ureidopenicillins with or without ß-lactamase inhibitor, 3rd and 4th generation cephalosporins, aminoglycosides, colistin, fluoroquinolones, and chloramphenicol. PCR was used to detect resistance genes in the bacterial isolates. Results and Conclusions. Among the total number of bacteria tested, regardless of the genus and species, 56.7% of isolates were found to be sensitive to all antibiotics, 23.1% of isolates were resistant to one or two antibiotics, and 20.2% of isolates were resistant to three and up to 16 antibiotics. In A. hydrophila isolated from a guppy (Poecilia reticulata) sampled in an ornamental fish store aquarium, 16S rRNA methyltransferase was confirmed by finding the rmtB gene. Pseudomonas isolates showing phenotypic resistance to carbapenems, ureidopenicillins with or without ß-lactamase inhibitor and 3rd and 4th generation cephalosporins were tested and found negative for different resistance genes by PCR (MßL, ESBL, KPC, OXA-23, OXA-24, OXA-40, OXA-58, VIM, IMP, SPM, GIM, NDM, TEM, SHV, CTX-M-1, CTX-M-9, OXA-1, OXA-9 and the AmpC group, as well as single genes, MOXM, CITM, ACCM, EBCM, FOXM, DHAM). Based on E-test results, three Pseudomonas isolates from common carp (Cyprinus carpio) were found to be resistant to colistin with MIC values of 4 μg/mL.Uvod. U ovom ispitivanju izolovane su bakterija koje su sastavni deo mikrobioma kože, škrga i creva riba iz različitih sredina (ribnjaci, akvarijumi, riblje pijace). Materijal i metode. Primenom disk difuzionog testa i E testa ispitivano je fenotipsko ispoljavanje rezistencije na karbapeneme, ureidopeniciline sa i bez inhibitora beta-laktamaza, cefalosporine III i IV generacije, aminoglikozide, tetraciklin, kolistin, flurohinolone i hloramfenikol. Prisustvo gena rezistencije vršeno je primenom metode PCR. Rezultati i zaključak. Posmatrano na ukupan broj ispitanih sojeva, bez obzira na rod i vrstu bakterija, 56,7% sojeva je osetljivo na sve antibiotike, 23,1% sojeva je rezistentno na 1 do 2 antibiotikaa 20,2% sojeva je rezistentno na 3 do 16 antibiotika. Kod soja A. hydrophila izolovanom iz akvarijumske ribice gupi nalazom gena rmtBpotvrđeno je prisustvo 16S rRNK metiltransferaze odgovornim za rezistenciju na aminoglikozide. Pseudomonas izolati koji su pokazali fenotipsku rezistenciju na karbapeneme, ureidopeniciline sa i bez inhibitora beta-laktamaza, kao i na cefalosporine III i IV generacije, testirani su i bili negativni na sledeće gene (MßL, ESBL, KPC, OXA-23, OXA-24, OXA-40, OXA-58, VIM, IMP, SPM, GIM, NDM, TEM, SHV, CTX-M-1, CTX-M-9, OXA-1, OXA-9, AmpC grupni kao i pojedinačni geni, MOXM, CITM, ACCM, EBCM, FOXM, DHAM). Na osnovu dobijenih rezultata primenom E testa, kod 3 soja iz roda Pseudomonas izolovanih od šarana nađena je rezistencija na kolistin sa dobijenim vrednostima MIK 4 μg/mL

Diferencijacija Pseudomonas i Stenotrophomonas vrsta izolovanih iz riba primenom molekularnih metoda i MALDI-TOF metode

For the purpose of precise antibiotic susceptibility testing it is necessary to clearly distinguish Pseudomonas and Stenotrophomonas genera, considering acquired resistance of Pseudomonas species, as well as the intrinsic resistance of Stenotrophomonas species. This is why in the identification of the 51 isolates originated from fish, the following methods were used: standard PCR, 16S rRNA gene sequencing, and MALDI-TOF. The results of the standard PCR test, 16S rRNA gene sequencing and MALDI-TOF analysis confirmed 35 strains to belong to the Pseudomonas genus. Standard PCR test and VITEK MS device confirmed that 10 strains belong to Stenotrophomonas maltophilia species. Three strains were positive in both standard PCR tests for Pseudomonas and Stenotrpohomonas. 16S rRNA gene sequencing identified these 3 strains to be 99% Pseudomonas sp. and 99% Stenotrophomonas sp. VITEK MS first identified these three strains as 99% Stenotrophomonas, and in the repeated identification it identified them as 99% Pseudomonas. MALDI TOF/TOF 4800 Plus device identified these strains as Stenotrophomonas. Three strains were negative in both standard PCR tests for Pseudomonas and Stenotrpohomonas. 16S rRNA gene sequencing identified these 3 strains to be 99% Pseudomonas sp. and 99% Stenotrophomonas sp. VITEK MS first identified these three strains as 99% Stenotrophomonas, and in the repeated identification it identified them as 99% Pseudomonas. MALDI TOF/TOF 4800 Plus device identified these strains as Stenotrophomonas. Although modern test methods that have very high specificity (PCR, 16S rRNA gene Pseudomonas and Stenotrophomonas species for 6 isolates could not be reached using the above mentioned methods.S obzirom na značaj stečene rezistencije Pseudomonas vrsta, kao i na intrinzičnu rezistenciju Stenotrophomonas vrsta, a u cilju preciznog ispitivanja osetljivosti na antibiotike, neophodna je jasna diferencijacija pripadnika ovih rodova bakterija. U tom cilju su u identifikaciji 51 izolata poreklom od riba korišćene metode: standardni PCR, 16S rRNA sekvenciranje gena, MALDI-TOF. Rezultati standardnog PCR testa, 16S rRNA sekvenciranja gena i MALDI-TOF analize su za 35 sojeva potvrdili pripadnost rodu Pseudomonas. Standardnim PCR testom i primenom aparata VITEK MS utvrđeno je da 10 sojeva pripada vrsti Stenotrophomonas maltophilia. U 16S rRNA sekvenciranju gena 3 soja koja su bila pozitivna u oba standardna PCR testa identifikovana su kao 99% Pseudomonas sp. i 99% Stenotrophomonas sp. VITEK MS je ova tri soja u prvoj identifikaciji identifikovao kao 99% Stenotrophomonas, a u ponovljenoj identifikaciji kao 99% Pseudomonas. Ti sojevi su na aparatu MALDI TOF/TOF 4800 Plus bili identifikovani kao Stenotrophomonas. U 16S rRNA sekvenciranju gena tri soja koja su bila negativna u oba standardna PCR testa su identifikovana kao 99% Pseudomonas sp. i 99% Stenotrophomonas sp. Aparat VITEK MS je ova tri soja identifikovao u jednoj identifikaciji kao 99% Stenotrophomonas, a u drugoj identifikaciji 99% kao Pseudomonas. Ti sojevi su na aparatu MALDI TOF/ TOF 4800 Plus bili identifikovani kao Stenotrophomonas. Iako su u ovom istraživanju korišćene savremene metode ispitivanja koje imaju vrlo visoku specifičnost (PCR, 16s rRNK sequencing, MALDI TOF) precizna diferencijacija Pseudomonas i Stenotrophomonas vrsta nije mogla biti postignuta

Supercritical Fluid Extraction of Celery and Parsley Fruit-Chemical Composition and Antibacterial Activity

Supercritical fluid extraction as an environmentally friendly technology was applied to isolate biologically active extracts from celery and parsley fruits for potential applications in the food industry. The extractions were performed under mild temperature conditions of 39.85 °C and at pressures of 10 and 30 MPa. The extracts were analyzed regarding their chemical composition, antibacterial activity, and cytotoxic effect. Sedanolide was the dominant component of the celery fruit extracts, comprising more than 70% of the obtained fraction, while the content of apiole in the parsley fruit SC CO2 extracts exceeded 85%. The celery fruit extracts showed strong and moderately strong antibacterial activity against tested Staphylococcus aureus, Bacillus (B.) cereus, B. subtilis, B. circulans, Listeria (L.) greyi, L. seeligeri and L. welshimeri, with minimal inhibitory concentration (MIC) values between 160 and 640 µg/mL, and weak activity against the selected Salmonella isolates with a MIC of 2560 µg/mL. The parsley extract obtained at 10 MPa showed strong and moderately strong antibacterial effects against Bacillus strains with obtained MICs of 160-640 µg/mL, and weak activity against Staphylococcus, Listeria, and Salmonella with a MIC of 2560 µg/mL. Cytotoxicity investigation showed that the extracts with proven antibacterial activity had no cytotoxic effect on rabbit kidney cells at concentrations of up to 640 µg/mL

Ispitivanje osetljivosti Staphylococcus vrsta na neke antibakterijske lekove primenom disk difuzione i mikrodilucione metode u bujonu

The objective of this work was to identify isolated Staphylococcus species and to investigate their sensitivity to some antibacterial drugs. The material used for these investigations were Staphylococcus isolates originating from milk samples. A total of 25 strains of Staphylococcus isolates were examined, including 24 from milk samples from cows with mastitis, and one strain was isolated from a milk sample from a cow following treatment for mastitis. For primary identification, catalase and oxidase tests were used, as well as the free coagulase test. Following the preliminary tests, the isolated strains were identified using commercial systems ID32 STAPH (bioMérieux, France) and the BBL Crystal Gram-Positive ID Kit (Becton Dickinson, USA) according to the enclosed instructions. The Staphylococcus isolates were examined for sensitivity to the following: oxacillin, penicillin, cefoxitin, gentamicin, erythromycin, chloramphenicol, tetracycline, ciprofloxacin, sulfametoxazol/trimetoprim, and vacomycin using the disk diffusion method and the broth microdilution method as recommended by the Clinical and Laboratory Strandards Institute - CLSI(2003), and the results were interpreted according to CLSI recommendations from 2008 and 2010. Antibiogram disks manufactured by Becton Dickinson (USA) were used, and the broth microdilution method was applied using pure antibiotic substances from different manufacturers: erythromycin, chloramphenicol, cefoxitin, gentamicin, oxacillin, tetracycline (Sigma Aldrich, USA), sulfametoxazol (Fluka, USA), penicillin (Calbiochem, Germany), vancomycin (Abbott laboratories, USA), ciprofloxacin and trimetoprim (Zdravlje A.D., Serbia). All 25 strains were catalase positive and oxidase negative. Of the 25 strains, 19 were coagulase positive and 6 were coagulase negative.With the implementation of the disk diffusion method on 19 strains of S. aureus, 17 were established to be resistant to penicillin (89.5%), and 2 strains to gentamicin (10.5%). The investigation of 3 strains of S. xylosus using the disk diffusion method showed that one strain was resistant to tetracycline (33.3%) and to oxacillin (33.3%), while another strain was found to be resistant to penicillin (33.3%). The third strain of S. xylosus was sensitive to all the examined antibiotics. Two strains of S. simulans and one strain of S. haemolyticus were not found to be resistant to any of the examined antibiotics using the disk diffusion method. The implementation of the broth microdilution method yielded in 13 strains of S. aureus resistance to penicillin (68.4%) with MIC values from 0.5 to 4 μg/m, in 2 strains to gentamicin (10.5%) with MIC values of 32 μg/ml, and intermediary sensitivity to chloramphenicol was established in 9 strains of S. aureus (47.4%) with MIC values of 16 μg/ml and to vancomycin in 1 strain of S. aureus (5.3%) with MIC values of 4 μg/ml.Cilj ovog rada je bila identifikacija izolovanih vrsta stafilokoka i ispitivanje njihove osetljivosti na neke antibakterijske lekove. Kao materijal u ovom ispitivanju korišćeni su izolati stafilokoka poreklom iz uzoraka mleka. Ukupno je ispitano 25 sojeva izolovanih stafilokoka od kojih su 24 poticala iz uzoraka mleka krava sa mastitisom, a jedan soj je izolovan iz uzorka mleka krave nakon lečenja mastitisa. U primarnoj identifikaciji su korišćeni katalaza i oksidaza testovi, kao i test prisustva slobodne koagulaze. Nakon izvođenja preliminarnih testova, vršena je identifikacija izolovanih sojeva, primenom komercijalnih sistema ID32 STAPH (bioMérieux, Francuska) i BBL Crystal Gram-Positive ID Kit (Becton Dickinson, SAD) prema uputstvima proizvođača. Osetljivost izolovanih sojeva stafilokoka ispitivana je na: oksacilin, penicilin, cefoksitin, gentamicin, eritromicin, hloramfenikol, tetraciklin, ciprofloksacin, sulfametoksazol/trimetoprim i vankomicin primenom disk difuzione metode i mikrodilucione metode u bujonu prema preporukama Instituta za kliničke i laboratorijske standarde (Clinical and Laboratory Strandards Institute - CLSI (2003), a tumačenje rezultata je vršeno prema preporukama CLSI iz 2008. i 2010. godine. Korišćeni su antibiogram diskovi proizvođača Becton Dickinson (SAD), a za mikrodilucionu metodu u bujonu korišćene su čiste supstance antibakterijskih lekova različitih proizvođača: eritromicin, hloramfenikol, cefoksitin, gentamicin, oksacilin, tetraciklin (Sigma Aldrich, SAD), sulfametoksazol (Fluka, SAD), penicilin (Calbiochem, Nemačka), vankomicin (Abbott laboratories, SAD), ciprofloksacin i trimetoprim (Zdravlje A.D., Srbija). Svih 25 sojeva je bilo katalaza pozitivno i oksidaza negativno. Od 25 sojeva, 19 je bilo koagulaza-pozitivno, a 6 koagulaza-negativno. Primenom disk difuzione metode od 19 sojeva S. aureus kod 17 je utvrđena rezistencija na penicilin (89,5%), a kod 2 soja na gentamicin (10,5%). Od 3 soja S. xylosus, kod jednog je primenom disk difuzione metode utvrđena rezistencija na tetraciklin (33,3%) i na oksacilin (33,3%), dok je kod drugog soja utvrđena rezistencija na penicilin (33,3%). Treći soj S. xylosus je bio osetljiv na sve ispitivane antibiotike. Kod dva soja S. simulans i jednog soja S. haemolyticus nije utvrđena rezistencija ni na jedan od ispitivanih antibiotika primenom disk difuzione metode. Primenom mikrodilucione metode u bujonu kod 13 sojeva S. aureus je utvrđena rezistencija na penicilin (68,4%) sa vrednostima minimalne inhibitorne koncentracije (MIC) od 0,5 do 4 μg/m, kod 2 soja na gentamicin (10,5%) sa vrednostima MIC od 32 μg/ml, a intermedijarna osetljivost na hloramfenikol utvrđena je kod 9 sojeva S. aureus (47,4%) sa vrednostima MIC od 16 μg/ml i na vankomicin kod jednog soja S. aureus (5,3%) čija je vrednost MIC iznosila 4 μg/ml

Temporal dynamics of polysemous verb processing

Semantic Settling Dynamics (SSD) model predicts that polysemy effect would change as a function of time spent in processing (Armstrong & Plaut, 2016). In early processing, the processing advantage would be large (compared to unambiguous words), whereas later, the effect would decrease. Research in Serbian described polysemy by quantitatively expressing the magnitude of the ambiguity of a particular word through measures such as number of senses (NoS). Such experiments revealed a facilitatory effect of polysemy in visual lexical decision task (vLDT; Filipović Đurđević, 2007). In SSD framework, this effect would be the equivalent of the early processing. Once the processing is prolonged, we expected reduction of this effect, similar to previous findings comparing polysemy to unambiguous words. This was demonstrated in experiments that employed the prolonging strategy of comparing vLDT (early processing) and auditory lexical decision task (aLDT; late processing). When the stimuli were nouns, we found the expected facilitatory polysemy effect in vLDT and null effect in aLDT (Mišić & Filipović Đurđević, 2019). Compared to the model predictions and the previous research, this loss of effect in later processing was unexpected. Therefore, the aim of this research was twofold – to extend the SSD testing on polysemous verbs and to replicate the results we found on nouns. We tested whether the NoS effect would change in the late processing by using the same prolonging strategy as in previous experiments. Two groups of participants (71 in vLDT, 75 in aLDT) were presented with 100 polysemous verbs in two versions of lexical decision task – visual and auditory. NoS was estimated based on the senses listed in the Matica Srpska dictionary (2007). Linear mixed modelling revealed that the aLDT was significantly slower than the vLDT. Marginal facilitatory NoS effect was found in vLDT (β = -.020, S.E. = .010, df = 100.07, t = -1.934, p = .056). The interaction with task modality was also marginally significant (β = .019, S.E. = .010, df = 98.84, t = -1.871, p = .064). Even though the NoS effect was marginally significant in both the baseline and the prolonged processing condition, the trends point to the same pattern of the results as the ones previously found. Early processing reveals a facilitatory effect, while in later processing, that effect is attenuated. This is a partial replication of the findings from the noun experiment and together they converge to the conclusion that the SSD model cannot give precise predictions regarding the effect change

The polysemy effect across inflected word forms

Polysemes are ambiguous words with multiple related senses (PAPER – ‘writing paper’ and ‘scientific paper’; Rodd et al., 2002). Previous research established that polyseme processing is also affected by sense uncertainty (Filipović Đurđević & Kostić, 2017). However, Serbian words appear in multiple inflected forms where each form has multiple syntactic meanings and functions and are therefore also ambiguous. The aim of this paper was twofold. The first was to explore the uncertainty effect throughout the inflected forms. We tested whether inflected word forms are equally ambiguous, considering that syntactic properties of a sentence can affect word meaning (Kostić et al., 2003). The second aim was to explore whether the potential (in)consistency of the polysemy effect could be a consequence of the dynamics of mapping cues to outcomes in a discriminative learning (DL) network. We collected lexical decision data and compared the predictive power of information-theoretic (IT) measures of uncertainty and the measures derived from the DL model (Baayen et al., 2011). We presented 35 polysemous nouns of masculine gender to 124 participants. Each noun was presented in seven inflected forms in a Latin-square design. Reaction times were predicted by two sets of variables – entropy of the sense frequency distribution (Filipović Đurđević & Kostić, 2017). DL predictors were derived from two cue-outcome weight matrices (Milin et al., 2017). Grapheme-to-lexome (G2L) matrix was calculated from a network mapping trigraphs to lemmata. Lexome-to-lexome (L2L) matrix from a network mapping 1000 co-occurring context words as cues to lemmata. Diversity measures from G2L and L2L (r = .36, p < .001; r = .25, p < .001), and G2L prior measure (r = .27, p < .001) correlated with entropy. We modelled lexical decision latencies with GAMMs (Wood, 2006) and compared models with entropy and DL predictors interacting with the inflected form. The entropy model revealed differing entropy effects across word forms, with marginal significance in the nominative form. DL model revealed a similar variation in DL predictor effect but had a better fit than the IT model. Inconsistent entropy effects across word forms suggest that there might be an interaction between semantics and syntax. Correlations between DL and entropy measures reveal that discrimination of orthographic cues might be a process behind this observed complexity. This research opens the question of the need for estimating ambiguity separately across different inflected forms of the same lemmata

Can a naive discrimination learning model classify inflected forms of polysemous nouns?

The interactive approach in the modularity-of-syntax debate suggests that we simultaneously process a vast amount of information regarding both semantic and syntactic meaning of a word. When we add to the consideration the ubiquity of ambiguity phenomena such as polysemy (multiple related senses), the information that most words convey seems quite demanding. Knowing that multiple approaches demonstrated the interaction between semantic and syntactic meanings (Kostić et al., 2004; Mišić & Filipović Đurđević, 2021), the aim of this study was to investigate whether this complexity can arise from a simple and cognitively plausible learning mechanism such as Rescorla-Wagner rule (RW; Rescorla & Wagner, 1972) implemented in the ndl framework (Arppe et al., 2015). Starting from the fact ndl can perform as a classifier (Milin et al., 2017, Sering et al., 2018), we wanted to test whether it can predict the correct inflected form of a polysemous word based on both orthographic and semantic cues. For the purposes of this paper we conducted two simulation studies with two different networks. Orthographic network learned inflected forms of 150 Serbian polysemous words (outcomes) based on the orthographic cues (trigrams; bradom – #br, bra, rad, ado, dom, om#). Each appearance of a target word in corpus was considered a learning event. These events were used to train the network using the RW rule. For each of the unique learning events, we calculated the bottom-up support that the outcome gets from cues that appeared by summing cue-outcome connection weights. The network correctly classified 94.6% of the outcomes. The semantic network utilized co-occurring words from the corpus as cues with the same outcomes. We preselected 3000 most frequent nouns, verbs, and adjectives (Frequency Dictionary of Contemporary Serbian Language; Kostić, 1999) for context words. Learning events in this simulation were built by moving a seven-point window centered on the outcome through the corpus. Whenever any of the context words were found within the positions flanking the outcome word, they would be considered cues in that learning event. RW rule training and classification on 880975 unique learning events was the same as in the orthographic network, however the success rate was opposite – only 3.4% of the words were correctly classified. The success of the orthographic network is not surprising, considering the small sample of words which reduces the need for cue competition. On the other hand, semantic cues i.e. context words seem to have the exact opposite problem. When most frequent words are selected, they are shared between many of the outcomes. Fewer distinct cues make discrimination between outcomes harder. Therefore, this low classification rate in the semantic network does not reject the interactive approach, but suggests the cue selection that does not capture the complex semantic and syntactic information