Kocuria Varians Research Articles

Kocuria varians infection associated with brain abscess: A case report

BackgroundKocuria, established by Stackebrandt et al., previously was classified into Micrococcus. Only two species, K. rosea and K. kristinae are reported to be associated as pathogenic and found with catheter-related bacteremia and acute cholecystitis.Case presentationWe herein report the first case of brain abscess caused by Kocuria varians, a gram-positive microorganism, in a 52-year-old man. Hematogenous spread is the probable pathogenesis.ConclusionsThis report presents a case of Kocuria varians brain abscess successfully treated with surgical excision combined with antimicrobial therapy. In addition, Vitek 2 system has been used to identify and differentiate between coagulase-negative staphylococcus.

Bacterial Pollution in Molluscs Arch Clam, Orbicularia orbiculata and Blood Cockle, Anadara granosa of Pahang Estuary, Malaysia

A study was conducted on physico-chemical parameters and bacterial pollution in Orbicularia orbiculata (Wood, 1828) and Anadara granosa (L.) at Pahang estuary from January to February 2009. The temperature was ranged from 28.00-29.87°C, pH 7.79-8.10, specific conductivity 51.49-55.89 mS cm-1, salinity 18.74-30.10 ppt., TDS 33.63-39.59 g L-1, DO 6.80-7.50 mg L-1. The nitrate concentration was found to be highest at Station 3 (14.09 μg at N-l) and lowest at Station 2 (7.04 μg at N-l). The nitrite concentration showed highest concentration at Station 4 (7.07 μg at N-l) and lowest concentration at Station 2 (1.67 μg at N-l). Whilst the phosphate content was higher (10.78 μg at N-l) at Station 3 and lowest at Station 2 (2.34 μg at N-l). A total of 60 Orbicularia orbiculata and 40 Anadara granosa samples were subjected to microbiological analysis. The bacteria were isolated using non selective agar such as TSA agar and selective agar before they were identified using conventional methods in combination with API identification kit. A total of nine bacterial species were identified from Orbicularia orbiculata. They were Escherichia coli., Aerococcus viridans 1, Aerococcus viridans 2, Gemella morbillorum, Kocuria varians, Micrococcus sp., Pseudomonas aeruginosa, Staphylococcus sciuri, Streptococcus pneumoniae. Whilst, Nineteen bacterial species were identified in Anadara granosa such as Aeromonas hydrophila group 1, Aerococcus viridians 1, Aerococcus viridans 2, Chromobacterium violaceum., Enterobacter gergoviae, Erwinia sp., Escherichia coli, Enterococcus avium, Gemella morbillorum, Kluyvera sp., Vibrio fluvialis, Vibrio cholerae, Vibrio parahaemolyticus, Lactococcus lactis, Leuconostoc sp., Staphylococcus capitis, Staphylococcus lentus, Staphylococcus epidermidis, Staphylococcus xylosus. The finding indicates that the edible mollusc of Pahang estuary was polluted with pathogenic bacteria which could be harmful for human consumption.

Prosthetic valve endocarditis due to Kocuria varians

Prosthetic valve endocarditis due to Kocuria varians

Combined Use of Starter Cultures and Preservatives To Control Production of Biogenic Amines and Improve Sensorial Profile in Low-Acid Salami

The combined effect of starter culture, nitrites, and nitrates has been studied in low-acidity salamis, typical products of northern Italy. Nine batches have been prepared, combining three different inoculations of starter cultures (control, Lactobacillus plantarum , and Lactobacillus plantarum together with Kocuria varians ) with three different preservatives (control, sodium nitrate, and sodium nitrite). All of the batches showed a good fermentation process with a proper pH decrease, which was quicker in batches inoculated with L. plantarum. The use of starter cultures and in particular the use of nitrites allowed the control of the proliferation of Enterobacteriaceae and enterococci. The accumulation of biogenic amines, especially putrescine, cadaverine, tryptamine, and tyramine, in salami ready for consumption (60 days of ripening) was strongly affected by the presence of Enterobacteriaceae and enterococci. Results obtained showed that the combined use of adequate preservatives and starter cultures allows the production of safer products with improved sensorial profile.

Staphylococcus pseudolugdunensis sp. nov., a pyrrolidonyl arylamidase/ornithine decarboxylase-positive bacterium isolated from blood cultures

Twelve coagulase-negative staphylococcal isolates recovered from blood cultures with positive pyrrolidonyl arylamidase and ornithine decarboxylase reactions were identified as Staphylococcus lugdunensis by the clinical microbiology laboratory. However, none of these 12 isolates were recognized by a S. lugdunensis translation elongation factor Tu ( tuf) gene-specific probe. Under the API STAPH V4.0 identification system (bioMérieux, Durham, NC), 8 of these 12 isolates could not be identified with low discrimination scores, and 4 were identified as Kocuria varians/ rosea with identification probabilities that ranged from 95.5% to 99.6%. All 12 isolates possessed identical partial 16S rRNA gene sequences, and the full 16S rRNA gene sequences of the prototype strain B006 were closely related to a tentatively assigned “ Staphylococcus pettenkoferi”. All 12 isolates had identical partial tuf gene sequences corresponding to 666 to 858 nucleotide positions, and the 1188-base pair full tuf sequences of B006 strain were mostly related to 2 Staphylococcus epidermidis isolates with a 93.02% similarity. Two isolates, which were recovered from the same patient over a 16-day interval, were considered to be a pathogen causing an intravenous line-associated infection; the remaining 10 isolates were considered to be skin contaminants. Biochemical tests currently used in the clinical microbiology laboratory to identify S. lugdunensis appear to lack specificity in identifying these isolates. On the basis of the close biochemical reactions with S. lugdunensis and phylogenetic evidence, these isolates are proposed the designation Staphylococcus pseudolugdunensis sp. nov.

<italic>Kocuria varians</italic> infective endocarditis

Kocuria varians belongs to genus Micrococcus. Members of the genus Micrococcus are generally believed to be temporary residents on humans, most frequently found on the exposed skin. We report a case of prosthetic valve endocarditis caused by K.varians in a patient who had undergone aortic valve replacement 8yrs ago. He presented with fever of two weeks duration. Investigations revealed infective endocarditis of prosthetic valve. Blood culture samples grew K.varians. The patient was empirically started on ampicillin and gentamicin intravenously and later with vancomycin and rifampicin. But the patient died due to neurological complications.

Microbial flora of spermatophores from black tiger shrimp(Penaeus monodon) declines over long-term cryostorage

Microbial contamination in sperm banks is of concern to sperm bank managers to prevent the perceived risk of disease transmission during cryostorage. The objective of this study was to examine the bacterial profile of cryopreserved spermatophores during long-term storage in liquid nitrogen in order to assess the risk of microbial flora during cryostorage. Spermatophores (N=216) collected from males (N=108) were equilibrated in calcium-free saline containing 5% dimethyl sulfoxide for 30 min and frozen at a cooling rate of −2 °C min−1 prior to storage in liquid nitrogen tanks. Cryopreserved spermatophores were sampled for bacterial profiles after 1 h and 30, 60, 90, 120, 150, 180 and 210 days using Plate count Agar, Thiosulphate Citrate Bile Salts Agar and Pseudomonas Isolation Agar. The incubation temperature was 37 °C for 24–48 h. Long-term storage of spermatophores in liquid nitrogen resulted in the reduction of the bacterial numbers. The number of total heterotrophic bacteria and total Vibrio decreased significantly (P<0.05) to 2.1±0.4×104 CFU/g (95.5% reduction) and 18.7±4.1×103 CFU/g (93.8% reduction), respectively, after 30 days in storage, while those of total Pseudomonas declined significantly (P<0.05) to 1.11±5.9×105 CFU/g (62.8% reduction) within 1 h of storage. Average sperm viability of cells from fresh spermatophores (96.4±1.8%) was not significantly different (P>0.05) from those of cryopreserved spermatophores held in liquid nitrogen for 1 h, 30 or 60 days (94.2±2.1, 89.8±3.5 and 86.7±3.9%, respectively, however it decreased significantly (P<0.05) after 90 days of storage. There were 23 bacterial species identified from fresh and cryopreserved spermatophores. The bacterial species least able to survive cold storage were Proteus mirabilis, Enterobacter spp., Vibrio spp., Kocuria varians, Bacillus cereus, B. amyloliquefaciens, B. circulans, Pseudomonas aeruginosa and Burkholderia cepacia because they were not detected from cryopreserved spermatophores after 90 or 120 days. The normal flora remaining at the end of the experiment (day 210) were Staphylococcus non aureus, Micrococcus spp., Proteus spp., Ochrobactrum anthropi, Corynebacterium spp., B. licheniformis and Pseudomonas spp. Cryopreservation of P. monodon spermatophores nearly eliminated the occurrence of pathogenic bacteria (Vibrio spp. and Ps. aeruginosa) culturable at 37 °C during long-term storage in liquid nitrogen.

Interactions between strains of Staphylococcus xylosus and Kocuria varians isolated from fermented meats

To evaluate the interactions of Staphylococcus xylosus on Kocuria varians strains isolated from fermented meat products. Interactions were assessed in vitro by agar spot test, agar well diffusion assay and spectrophotometric assay. The growth of K. varians (five strains) alone was compared with that in the presence of growing cells of S. xylosus (50 strains) or in the presence of heat-treated or untreated supernatants of S. xylosus. Sixteen strains stimulated the growth of K. varians K4, while four strains inhibited the K4 strain. Heated cell-free supernatants of S. xylosus did not have any effect on K. varians. The proteolytic activity of single strains or their combinations was assessed in vitro and in vivo by sodiumdodecylsulfate-polyacrylamide gel electrophoresis of sarcoplasmic protein extracts. Combinations of stimulatory strains of S. xylosus and K. varians showed a higher proteolytic activity compared with that of S. xylosus or K. varians alone. The interactions between strains may influence both the growth of the co-cultured strains and proteolysis, technologically relevant characteristics. The study of interactions between coagulase-negative cocci may guide the formulation of mixed strain starters for the production of fermented sausages.

Microbiological characteristics of “androlla”, a Spanish traditional pork sausage

Counts of total aerobic mesophilic microflora, lactic acid bacteria, salt-tolerant microflora, Enterobacteriaceae, enterococci, moulds and yeasts, and staphylococci, and some physico-chemical parameters (total solids, NaCl and nitrate contents and pH and a w values) were determined in 20 units of “androlla”, a traditional dry-fermented sausage made in the NW of Spain. In general, high counts of all the investigated microbial groups were observed, with average values of 8.99±0.46 log cfu/g for the total aerobic mesophilic microflora, 9.11±0.16 log cfu/g for the lactic acid bacteria, 6.87±0.68 log cfu/g for the salt-tolerant microflora, 2.80±1.85 log cfu/g for the Enterobacteriaceae, 3.25±1.86 log cfu/g for the enterococci, 4.30±1.73 log cfu/g for the moulds and yeasts, and 3.62±0.60 log cfu/g for the staphylococci. From MRS agar, SPC agar+7.5% NaCl, VRBG agar, and KAA agar, 10 colonies were randomly taken from each androlla unit and from each culture medium. A total of 200 strains per culture medium were then identified using the classical methods. Among the isolates from MRS agar, Lactobacillus sakei predominated, followed by Lactobacillus curvatus, Lactobacillus alimentarius and Lactobacillus plantarum. Of the 200 isolates obtained from SPC agar+7.5% NaCl, only 56 strains belonged to the Staphylococcaceae or Micrococcaceae families. Among the Staphylococcaceae, Staphylococcus xylosus was the main species, followed by Staph. epidermidis; Staph. equorum, Staph. capitis and Staph. saprophyticus were isolated in very low proportions. Among the Micrococcaceae, Micrococcus luteus predominated, followed by Micrococcus lylae, Kocuria varians and Kocuria kristinae. Of the 150 isolates obtained from VRBG agar, Hafnia alvei was the main species, followed by Serratia liquefaciens and Enterobacter amnigenus; six isolates were identified as Salmonella. Among the 190 isolates obtained from KAA agar, 122 were considered enterococci; 20 isolates were identified as Enterococcus faecium, one as Enterococcus faecalis and 101 as Enterococcus inter faecalis-faecium.

Construction and analysis of fractional multifactorial designs to study attachment strength and transfer of Listeria monocytogenes from pure or mixed biofilms after contact with a solid model food.

The aim of this study was to establish which of seven factors influence the adhesion strength and hence bacterial transfer between biofilms containing Listeria monocytogenes (pure and two-species biofilms) and tryptone soya agar (TSA) as a solid organic surface. The two-species biofilms were made of L. monocytogenes and one of the following species of bacteria: the nonpathogenic organisms Kocuria varians, Pseudomonas fluorescens, and Staphylococcus sciuri and CCL 63, an unidentified gram-negative bacterium isolated from the processing plant environment. We used biofilms prepared under conditions simulating open surfaces in meat-processing sites. The biofilm's adhesion strength and population were evaluated by making 12 contacts on a given whole biofilm (4.5 cm(2)), using a new slice of a sterilized TSA cylinder for each contact, and plotting the logarithm CFU . cm(-2) detached by each contact against the contact number. Three types of detachment kinetics were observed: biphasic kinetics, where the first slope may be either positive or negative, and monophasic kinetics. The bacteria that resisted a chlorinated alkaline product and a glutaraldehyde- and quaternary ammonium-based disinfectant had greater adhesion strengths than those determined for untreated biofilms. One of the four non-Listeria strains studied, Kocuria varians CCL 56, favored both the attachment and detachment of L. monocytogenes. The stainless steel had smaller bacterial populations than polymer materials, and non-Listeria bacteria adhered to it less strongly. Our results helped to evaluate measures aimed at controlling the immediate risk, linked to the presence of a large number of CFU in a foodstuff, and the delayed risk, linked to the persistence of L. monocytogenes and the occurrence of slightly contaminated foods that may become dangerous if L. monocytogenes multiplies during storage. Cleaning and disinfection reduce the immediate risk, while reducing the delayed risk should be achieved by lowering the adhesion strength, which the sanitizers used here cannot do at low concentrations.

Behaviour of the constitutive biota of two types of Spanish dry-sausages ripened in a pilot-scale chamber

The behaviour of the constitutive biota in eighty four samples belonging to two different types of Spanish dry-cured sausages during the ripening process in a pilot-scale chamber was investigated. Samples were analyzed in three stages during production: fresh product, first drying stage and finished product. Lactic acid bacteria (LAB) and Coagulase-negative cocci (CNC) were identified by the API system. In general, evolution of LAB and CNC during the ripening process of Spanish dry-cured sausages increased during the first days after which numbers of these organisms remained stable. Pediococcus pentosaceus and Staphylococcus xylosus, were the dominant species. Lactobacillus plantarum, Staphylococcus saprophyticus Staphylococcus simulans and Kocuria varians were also present. The results obtained show that the ripening process in a pilot-scale chamber under controlled conditions contributes to a more homogeneous behaviour of the constitutive biota, in comparison with commercial production standards.

Molecular, technological and safety characterization of Gram-positive catalase-positive cocci from slightly fermented sausages

The population of Gram-positive catalase-positive cocci from slightly fermented sausages was characterized at species and strain level by molecular techniques and some technological and hygienic aspects were also considered. Staphylococcus xylosus was the predominant species (80.8%) followed by Staphylococcus warneri (8.3%), Staphylococcus epidermidis (5.8%) Staphylococcus carnosus (4.6%), and Kocuria varians (0.4%). Proteolytic activity was observed in 23% of the isolates. The species with the highest percentage of proteolytic strains was S. warneri. Lipolytic activity was found in 45.8% of the isolates and S. xylosus was the species with the highest percentage of lipolytic isolates. Biogenic amine production was not widely distributed (only 14.6% of the isolates). Tyramine was the most intense amine produced, although by only 4.6% of the isolates. Phenylethylamine was more frequently detected (10.8% of isolates) but at lower levels. Some strains also produced putrescine (3.3%), cadaverine (2.9%), histamine (1.3%) and tryptamine (0.4%). All isolates were susceptible to linezolid and vancomicin and over 70% were resistant to penicillin G, ampicilin and sulphonamides. Most of the mecA + strains (only 4.6% of isolates) also displayed resistance to multiple antibiotics. A reduced enterotoxigenic potential was found. Only 3.3% of isolates showed staphylococcal enterotoxins genes, all identified as entC gene. The combination of RAPD-PCR and plasmid profiling allowed the discrimination of 208 different profiles among the 240 Gram-positive catalase-positive cocci characterized, indicating a great genetic variability.

Volatile and Biogenic Amines, Microbiological Counts, and Bacterial Amino Acid Decarboxylase Activity throughout the Salt-Ripening Process of Anchovies (Engraulis encrasicholus)

Chemical and microbiological parameters were studied during the industrial production of salt-ripened anchovies (Engraulis encrasicholus). Gradual acidification and increases in the proteolysis index and in total volatile basic nitrogen were observed. At the end of the maturing process, the values reached pH 5.55 ± 0.03, 21.33 ± 5.82%, and 44.06±12.47 mg/100 g, respectively. In the three studied anchovy batches, the biogenic amines tyramine, histamine, putrescine, cadaverine, and agmatine increased during ripening. The highest values were found in the batch where initial microbial load was highest (batch 1), especially for enterobacteria and enterococci. Tyramine was the most abundant amine, reaching values from nondetectable to 90 mg/kg, whereas histamine did not surpass 20 mg/kg. Among the microorganisms isolated, Enterobacter cloacae, Aerococcus viridans, Kocuria varians, and Staphylococcus chromogenes were able to decarboxylate amino acids and produce biogenic amines in vitro. Most (70.59%) of the microorganisms identified were able to produce histamine, 23.53% were able to produce the diamines putrescine and cadaverine, and only 11.76% were able to produce tyramine, although this substance was the major biogenic amine found in anchovy samples.

Reclassification of strain CCM 132, previously classified as Kocuria varians, as Kocuria carniphila sp. nov.

A Gram-positive actinobacterium, previously classified as Kocuria varians, was subjected to a polyphasic taxonomic study. The bacterium showed the peptidoglycan type Lys-Ala3 (variation A3alpha), MK-7(H2) was the major menaquinone and anteiso-C(15 : 0) and anteiso-C(17 : 0) were the major fatty acids. On the basis of the phylogenetic and phenotypic characteristics of the actinobacterium, a novel species, Kocuria carniphila sp. nov. (type strain, CCM 132T=DSM 16004T), is proposed.

Effect of chlorophenols on the membrane lipids of bacterial cells

Abstract Chlorophenols, widespread soil and water contaminants and often degradation products of some pesticides, are a potential stress factor for survival of environmental bacteria. The effect of pentachlorophenol (PCP) and 2,4-chlorophenol (2,4-CP) on the growth, amount of lipid, and fatty acid composition in the membrane lipids was examined in a strain of the bacterium Kocuria varians, able to degrade chlorophenols. The index of fatty acid unsaturation in two main membrane lipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) decreased in the presence of chlorophenols. Transformation of stearic acid into oleic acid was significantly increased by PCP addition only in PE, but conversion of oleic acid into linoleic acid was blocked by PCP and 2,4-CP in both PC and PE. This observation may indicate that while Δ9 desaturase was sensitive mainly to 2,4-CP, activity of Δ12 desaturase was inhibited by both PCP and 2,4-CP.

Interactions in biofilms between Listeria monocytogenes and resident microorganisms from food industry premises

Twenty nine bacterial strains were grown as binary culture biofilms with Listeria monocytogenes to assess their influence on the settlement of the latter on stainless steel coupons. Most of the strains had been isolated from food processing plants after cleaning and disinfection and were tentatively identified by the APILAB Plus 3.3.3 database (bioMérieux). Sixteen of them decreased L. monocytogenes biofilm colony forming units (CFU) counts. Three strains, Bacillus sp. CCL 9 an unidentified Gram-positive strain CCL 59 and Pseudomonas fluorescens E9. 1, led to a 3-log difference in CFU counts between the pure L. monocytogenes biofilms and the mixed biofilms. Eleven strains had no effect and only four, Kocuria varians CCL 73, Staphylococcus capitis CCL 54, Stenotrophomonas maltophilia CCL 47 and Comamonas testosteroni CCL 24, had a positive effect, with a 0.5- to 1.0-log increase in the L. monocytogenes biofilm CFU counts. On its own, L. monocytogenes settled as single cells, but in binary biofilms, different spatial arrangements were observed: (i) with K. varians CCL 73, K. varians CCL 56 and S. capitis CCL 54, L. monocytogenes cells gathered around the microcolonies of the partner strain; (ii) with the two Gram-negative strains, C. testosteroni CCL 24 and CCL 25, L. monocytogenes cells formed its own microcolonies. No link could be found between the exopolysaccharide production capacity of the bacterial strains in pure-culture biofilms and their effect on the L. monocytogenes population in mixed biofilms. With one strain, C. testosteroni CCL 24, adding filter-sterilized supernatant from a pure-culture biofilm to a pure culture of L. monocytogenes increased the number of L. monocytogenes cells adhering to the stainless steel coupons and forming microcolonies. This study suggests that the “house flora” can have a strong effect on the likelihood of finding L. monocytogenes on inert surfaces.

Antimicrobial Potential of Immobilized Lactococcus lactis subsp. lactis ATCC 11454 against Selected Bacteria

Immobilization of living cells of lactic acid bacteria could be an alternative or complementary method of immobilizing organic acids and bacteriocins and inhibit undesirable bacteria in foods. This study evaluated the inhibition potential of immobilized Lactococcus lactis subsp. lactis ATCC 11454 on selected bacteria by a modified method of the agar spot test. L. lactis was immobilized in calcium alginate (1 to 2%)–whey protein concentrate (0 and 1%) beads. The antimicrobial potential of immobilized L. lactis was evaluated in microbiological media against pathogenic bacteria (Escherichia coli, Salmonella, and Staphylococcus aureus) or Pseudomonas putida, a natural meat contaminant, and against seven gram-positive bacteria used as indicator strains. Results obtained in this study indicated that immobilized L. lactis inhibited the growth of S. aureus, Enterococcus faecalis, Enterococcus faecium, Lactobacillus curvatus, Lactobacillus sakei, Kocuria varians, and Pediococcus acidilactici. Only 4 h of incubation at 35°C resulted in a clear inhibition zone around the beads that increased with time. With the addition of 10mM of a chelating agent (EDTA) to the media, results showed growth inhibition of E. coli; however, P. putida and Salmonella Typhi were unaffected by this treatment. These results indicate that immobilized lactic acid bacteria strains can be successfully used to produce nisin and inhibit bacterial growth in semisolid synthetic media.

Endoroot bacteria derived from marigolds (Tagetes spp.) can decrease soil population densities of root-lesion nematodes in the potato root zone

Single isolates of bacterial endophytes, isolated from the nematode antagonistic plant species African (Tagetes erecta L.) and French (T. patula L.) marigold, were introduced into potatoes (Solanum tuberosum L.). Several bacterial species possessed activity against root-lesion nematodes (Pratylenchus penetrans) in soils around the root zone of potatoes, namely: Microbacterium esteraromaticum, Tsukamurella paurometabolum, isolate TP6, Pseudomonas chlororaphis, Kocuria varians and K. kristinae. Of these, M. esteraromaticum and K. varians depressed the population densities of root-lesion nematodes without incurring any yield penalty (tuber wet weight). No significant differences were found in the total numbers of P. penetrans nematodes, rhabditid nematodes or `other' parasitic nematode species within the root tissues of bacterized potato plants compared to the unbacterized check. Overall, tuber fresh weights and tuber number were equal to or significantly lower (P\le0.05) in bacterized plants than their unbacterized counterpart. We conclude that endoroot bacteria from Tagetes spp. can play a role in nematode suppression through the attenuation of nematode proliferation. We propose that these nematode control properties are capable of transfer to other crops in a rotation as a beneficial `residual' microflora – a form of beneficial microbial allelopathy.

Validation of a microbiological method: the STAR protocol, a five-plate test, for the screening of antibiotic residues in milk

The results of an in-house laboratory validation of a microbiological method for the screening of antibiotic residues in milk are presented. The sensitivity of this five-plate test, called Screening Test for Antibiotic Residues (STAR), was established by the analysis of milk samples spiked with 66 antibiotics at eight different concentrations. Ten different groups of antibiotics were studied: macrolides, aminoglycosides, cephalosporins, penicillins, quinolones, tetracyclines, sulphonamides, lincosamides, phenicolated and miscellaneous drugs. It was shown that 21 antibiotics were detected by the STAR protocol at or below the maximum residue limit (MRL), and that a further 27 drugs could be detected at levels from the MRL up to four times the MRL. The sensitivity of the STAR protocol was at or below the MRL for three macrolides, one tetracycline, two aminoglycosides, some sulphonamides, half of the beta-lactams, quinolones, lincosamides, trimethoprim and baquiloprim. Moreover, the STAR protocol was at least twice as sensitive as conventional methods for macrolides, quinolones and tetracyclines. The other antibiotics had limits of detection between four and 150 times the MRL. Each plate was preferentially sensitive for one or two families of antibacterials: the plate Bacillus cereus for tetracyclines, the plate Escherichia coli for quinolones, the plate Basillus subtilis for aminoglycosides, the plate Kocuria varians for macrolides, and the plate Bacillus stearothermophilus for sulphonamides and beta-lactams. This method has been used routinely on a day-to-day basis to direct the physicochemical confirmation towards one or two families of antibiotics. Considering the high cost of liquid chromatography coupled with tandem mass spectrometry detection analyses, the reduction of the range of antibiotics to test for confirmation is a significant gain in time and money.

Contribution of starter cultures to the proteolytic process of a fermented non-dried whole muscle ham product

Porcine longissimus dorsi muscles were cured by brine injection. Curing brine containing 15% (w/v) NaCl, 1.33% (w/v) glucose, 750 ppm sodium nitrite, and appropriate levels of either Lactobacillus sakei LAD, L. sakei LAD plus Kocuria varians FT4 (formally Micrococcus varians), L. sakei LAD plus papain and GDL (glucono-delta-lactone) plus K. varians FT4, was injected to the muscle at a pumping rate 15% w/v. The effect of these treatments on the proteolysis in the ham system was compared to a control ham, produced without starter culture and containing GDL acidulant to control pH and antibiotics to reduce the contribution of background microflora. Hydrolysis of sarcoplasmic and myofibrillar protein fractions was evaluated by SDS-PAGE and reverse phase-HPLC. Hams with different treatments were also investigated for differences in amino acid profile, protein and non-protein nitrogen level, colour, pH, water activity and moisture and microbiological evolution. There was no significant difference in the gross compositional analysis of any of the treatments compared to the control. There was no significant difference ( p>0.05) in the protein content, non-protein nitrogen level, SDS-PAGE and free amino acid analysis between the control ham and ham inoculated with proteolytic starter culture. However, it was observed that hams containing starter cultures exhibited decreases in certain peptide fractions and corresponding increases in some free amino acids compared to the uninoculated control. It can be concluded that, while the principle mechanisms resulting in the proteolysis of this non-dried ham product involve the activity of endogeneous cathepsins, the addition of proteolytic starter cultures influence the amino acid profile thereby potentially enhancing the sensorial attributes of the ham.