The Effect of Temperature, Pressure and Chlorine Concentration of Spray Washing Water on Numbers of Bacteria on Lamb Carcases

Combined analysis of three experiments showed that when lamb carcases with initial bacterial numbers of between logi₁₀3.29 and 4.22/cm² were spray washed, statistically significant reductions in bacterial numbers of log₁₀O.5 were obtained when the spray wash water temperature was > 57°C, and reductions of log₁₀1.0 were obtained when the temperature was ≥ 80°C. Reductions at all temperatures were enhanced by log₁₀0.66 when the water contained 30 µg/ml chlorine, but increasing the concentration to 450 µg/ml reduced bacterial numbers only by a further log₁₀0–29. At highly contaminated sites increasing the duration of spraying from 30 to 120 s significantly increased the reductions obtained when water containing added chlorine was used. Reductions in bacterial numbers after spray washing with pressures of 3.5, 5.6. 7.7 kg/cm² were not significantly different.     

Bacteriological evaluation of groups of beef carcasses before the wash at six Alberta abattoirs

K.W.F. JERICHO, J.A. BRADLEY AND G.C. KOZUB. 1994. A method has been developed for the bacteriological evaluation of groups of beef carcasses which can be used to measure the degree of control over hygiene during hide removal and carcass dressing in abattoirs. This method, which enumerates aerobic mesophilic bacteria automatically using a hydrophobic grid membrane filter, was applied at six abattoirs. Two hundred excision samples (5 × 5 × 0.5 cm) were taken at 10 sites on the external surface of a group of 20 carcasses (five carcasses were sampled on each of four consecutive daily visits) for group-carcass evaluation at each abattoir. For each abattoir, the mean log₁₀ Most Probable Number of Growth Units (MPNGU) and between-carcass variance component were obtained for each site and the average over sites. Using the average within-abattoir variance of this study and previously published studies involving 76 additional carcasses (Jericho et al. 1993), it was determined that 20 carcasses are more than adequate to estimate the mean log₁₀ MPNGU per cm² within 0.5 units at a site. The distribution of the log₁₀ MPNGU per cm² over the 10 sites was compared for the abattoirs, and sites were found to cluster into 2–4 homogenous groups. The means over sites of log₁₀ MPNGU per cm² for the abattoirs ranged from 1.52 to 2.64 and were unrelated to line speed     

Comparison of conductimetric and traditional plating techniques for detecting yeasts in fruit juices

Frozen fruit juice concentrates containing an average microbial population of log₁₀ 1.54 cfu ml^-1 were examined by traditional plating techniques and direct and indirect conductimetry. The initial populations in diluted (1:4) concentrates increased to an average of log₁₀ 3.82 cfu ml^-1 during incubation at 25°C for 24 h. Incubation before plating and subjecting to conductimetric tests also facilitated the resuscitation of cells that may have been freeze-injured. Yeasts were recovered in equal numbers on acidified (pH 3.5) potato dextrose agar and dichloran rose bengal chloramphenicol agar (pH 5.6). Yeasts and bacteria were recovered on orange serum agar. Detection times determined by indirect conductimetry correlated fairly well ( r = -0.73) with populations (cfu ml^-1) detected on traditional plating media. Populations in diluted concentrates which were not incubated before examination were detected conductimetrically in an average of 48.9 h, whereas detection times for diluted concentrates incubated for 24 h at 25°C before testing were reduced to an average of 14.1 h. Examination by conventional (direct) conductimetry required an additional 10–20 h to reach changes in conductance of 5 μS h^-1.     

Survival of Escherichia coli O157 : H7 in yoghurt during preparation and storage at 4°C

Cow's milk was inoculated with ca 10³ and 10⁷ cfu ml⁻¹ Escherichia coli O157 : H7. After fermentation at 42°C for 0–5 h, the yoghurt was stored at 4°C. Two kinds of yoghurt were used : traditional yoghurt (TY), made with Streptococcus thermophilus and Lactobacillus bulgaricus starter cultures, and 'bifido' yoghurt (BY), made with the two starter cultures plus Bifidobacterium bifidum . After 7 d E. coli O157 : H7 decreased from 3·52 to 2·72 log₁₀ cfu ml⁻¹ and from 7·08 to 5·32 log₁₀ cfu ml⁻¹ in TY, and from 3·49 to 2·73 log₁₀ cfu ml⁻¹ and from 7·38 to 5·41 log₁₀ cfu ml⁻¹ in BY. The pH values of yoghurt dropped from 6·6 to 4·5 and 4·4 in TY (for low and high pathogen inocula, respectively), and from 6·6 to 4·6 and 4·5 in BY (for low and high pathogen inocula, respectively).     

Amines in fresh beef of normal pH and the role of bacteria in changes in concentration observed during storage in vacuum packs at chill temperatures

E dwards , R.A., D ainty , R.H., H ibbard , C.M. & R amantanis , S.V. 1987. Amines in fresh beef of normal pH and the role of bacteria in changes in concentration observed during storage in vacuum packs at chill temperatures.
The amine content of fresh and vacuum-packaged beef of normal pH stored at 1°C was evaluated by high performance liquid chromatography of dansyl derivatives. Fresh samples contained five amines, viz. putrescine, cadaverine, histamine, sperm-ine and spermidine. Development of a natural spoilage flora during storage led to increases in concentration of putrescine and cadaverine and the production of a sixth amine, tyramine. Pure culture meat inoculation experiments showed tyramine formation to be restricted to lactobacilli and to strains of Lactobacillus divergens and Lact. carnis in particular; strains of leuconostocs, Enterobacteriaceae, Pseudomonas spp. and Brochothrix thermosphacta were negative. Production of tyramine at cell densities >log₁₀ 6/cm² indicated its potential as an objective measure of acceptability/spoilage.     

Routine metabolism of juvenile spot, Leiostomus xanthums (Lacépède), as a function of temperature, salinity and weight

Routine oxygen consumption rates of juvenile spot, Leiostomus xanthums , were measured over a range of temperatures, salinities and fish weights. As predicted, Q O₂ increased with temperature and decreased with body weight. However, Q O₂ decreased with decreasing salinity and did not show the expected minimum at isosmotic concentrations. The data are best described by the relationship: log₁₀ Q O₂ (mg O₂ g⁻¹ h⁻¹) = 0.129 log_lo salinity (%0) + 1.604 log₁₀ temperature (°C)-0.1401og₁₀(g)-2.767.     

The influence of thermal parameters on the acclimation responses of pinfish Lagodon rhomboides exposed to static and decreasing low temperatures

Pinfish Lagodon rhomboides acclimation rates were determined by modelling changes in critical thermal minimum ( T _{crit min}, ° C) estimates at set intervals following a temperature decrease of 3–4° C. The results showed that pinfish gained a total of 3·7° C of cold tolerance over a range of acclimation temperatures ( T _acc, ° C) from (23–12° C), that cold tolerance increased with exposure time to the reduced temperature at all T _acc, but that the rate of cold tolerance accruement (mean 0·14° C day⁻¹) was independent of T _acc. A highly significant ( P < 0·001) multivariate predictive model was generated that described the acclimation rates and thermal tolerance of pinfish exposed to reduction in water temperature: log₁₀ T _{crit min}= 0·41597 − 0·01704 T _acc+ 0·04320 T _plunge− 0·08376[log₁₀ ( t + 1)], where T _plunge is plunge temperature (° C) and t is the time (days). A comparison of the present data, with acclimation rate data for other species, suggests that factors such as latitude or geographic range may play a more important role than ambient temperature in determining cold acclimation rates in fishes.     

Effect of heat treatment on Cronobacter spp. in reconstituted, dried infant formula: preparation guidelines for manufacturers

Aim:  To explore safe guidelines for manufacturers and consumers to prepare, handle and store dry infant formula (DIF) to protect infants against Cronobacter spp.
Methods and Results:  Selected strains (2.45, FSM 293, ATCC-12868, FSM-271) screened from 68 strains of Cronobacter spp . were used to study growth and survival in commercial DIF. Prototype growth patterns in Enterobacteriaceae enrichment broth (EEB) containing a cocktail comprised of ATCC 12868, ATCC 29004, ATCC 29544 and ATCC 51329 showed a rapid increase in cell count (2·0 log₁₀ to 6·2 log₁₀ CFU ml⁻¹). Infant formula provided a better protective environment for the cells of Cronobacter strains than did buffered peptone water . Experiments on survival in inoculated (10⁴–10⁶ CFU ml⁻¹) reconstituted infant formula (RIF), preparation temperature, the effect of preparation volume (one-serving or two-serving) and effect of storage at room temperature for up to 10 h provided information to develop consumer guidelines for DIF preparation and handling.
Conclusions:  Reconstituted DIF in water at >70°C in larger volumes, minimizing storage time before feeding and storing unused reconstituted formulate at <4°C, may reduce the risk of Cronobacter infection in infants.
Significance and Impact of the Study:  Meningitis, necrotizing enterocolitis and bacteremia in premature babies has been linked to contaminated milk powder and DIF; better handling practices may improve the safety of these foods for neonates.     

A desk study of the relationship between temperature and hatching time for the eggs of five species of salmonid fishes

SUMMARY. Information on temperature (T°C) and time from fertilization to 50% hatch ( D days) for five species of salmonid fishes has been used to assess several mathematical models relating D and T . No single equation gave the best fit to all five data sets. The power law with temperature correction (α), log₁₀₁ D = log₁₀ a + b log₁₀ ( T - α) and the quadratic, log₁₀ D = log₁₀ a + bT + b ₁ T ² (where a, b, b ₁, and α are constants), each accounted for over 97 % of the variance of D and were good fits to the observed data points for all five species. There was little difference between the predictions obtained from these two equations within the range of observed temperatures. Therefore, the simpler power-law model is preferred. However, there were substantial within-species differences between values of D predicted from extrapolations of the two models from 2 or 3°C down to 0°C. When more data for low temperatures become available it will be possible to make a more objective choice of model.     

Effect of Hyperbaric Carbon Dioxide Pressure on the Microbial Flora of Pork Stored at 4 or 14°C

Changes in the microbial flora of pork stored at 4 or 14°C were studied in 5 atm CO₂, 1 atm CO₂ or 1 atm air. The time needed for the total aerobic count at 4°C to reach 5 × 10⁶ organisms/cm² was about three times longer in 5 atm CO₂ than in 1 atm CO₂, and about 15 times longer in 5 atm CO₂ than in air. At 14°C there was no difference in growth rate between 5 atm CO₂ and 1 atm CO₂. No off-odour was detected after storage in 5 atm CO₂ for 14 d, but the pork in 1 atm CO₂ (6 d) was organoleptically unacceptable.
The predominant organisms on the pork from the processing line were: Flavobacterium spp., Acinetobacter calcoaceticus, Pseudomonas spp., Micrococcus spp. and Moraxella spp. After aerobic storage at 4°C (8 d) or 14°C (3 d) more than 90% of the flora consisted of Pseudomonas spp. At 4°C all Pseudomonas spp. were of the non-fluorescent type, whilst at 14°C 32% were Ps. putida and Ps. fluorescens. After storage in 1 atm CO₂ Lactobacillus spp. represented 66% of the flora at 14°C (6 d) and 100% at 4°C (40 d), with L. xylosus dominating. After storage in 5 atm CO₂ Lactobacillus spp. constituted the total flora at both temperatures with L. lactis (14°C) and L. xylosus (4°C) dominating.
It was concluded that high partial pressures of CO₂ have a considerable shelf-life prolonging effect by (i) selecting the microflora towards Lactobacillus spp. and (ii) reducing the growth rate of these Lactobacillus spp. The controlling and growth inhibitory effect of CO₂ was promoted by reduced temperatures.     

A novel terrestrial halophilic environment: The phylloplane of Atriplex halimus, a salt-excreting plant

Abstract This paper describes the microbial ecosystem found on the leaves of Atriplex halimus , a salt-excreting plant in the central Negev highlands of Israel. Because of the regular nightly occurence of dew at this location, these leaves undergo a diurnal wetting so that phylloplane microorganisms experience large fluctuations in salinity and water activity, as well as tolerate repeated desiccation. During the dry season, in the late spring and summer, a significant amount of salts and organic material coats the leaf surface. During dew events the salt concentration at the leaf surface was calculated to be > 0.4 M. Direct counts of the respiring bacteria on the leaf surface ranged from 1.06×10⁴ to 5.06×10⁵ per cm². Using a variety of media it was shown that there was limited bacterial diversity which could be cultured, with greater than 90% of the isolates being orange colored Gram-negative rods. Viable counts ranged from 0.32 to 2.32×10⁴ bacteria per cm² of A. halimus leaf surface. No bacteria capable of nucleating ice were recovered in these studies. The dominant orange pigmented bacterium, identified as a halotolerant Pseudomonas sp., grew optimally at 30°C and at 5% NaCl and was capable of growth in media containing up to 20% NaCl. This bacterium could grow on a variety of organic compounds, including some associated with plant materials. The leaf bacteria were desiccation-tolerant when on the leaf surface or when directly washed off the leaves, but much less so when in isolatd culture. A major component of the tolerance to desiccation is probably related to the compounds on the leaf surface.     

Enterotoxigenicity of Staphylococcus aureus strains isolated from poultry: raw poultry carcases as a potential food-poisoning hazard

Staphylococcus aureus strains were isolated from end-of-lay poultry carcases obtained from a plant at two different stages of processing before and after storage at different temperatures. These strains were supplemented with Staph. aureus strains isolated from poultry from a wide range of sources and biotyped, phage typed, and tested for production of enterotoxins A-E. The isolates were found to consist of poultry and human specific strains and each of these groups contained strains able to produce enterotoxin. Poultry strains produced only enterotoxin D whereas human strains produced enterotoxins A, C and D. The hen carcases used in storage experiments were found to be naturally contaminated with enterotoxin D producing staphylococci. No enterotoxin D could be detected on any of the carcases even after storage at temperatures which allowed multiplication of the organisms to occur (final Staph. aureus counts ranged from 10² to 10⁷/16 cm² of breast skin).     

Note: Thermophilic campylobacters in dairy slurries on Lancashire farms: seasonal effects of storage and land application

Slurry storage tanks on Lancashire farms were sampled in May, June, October and November. There was a seasonal pattern in the number of thermophilic campylobacters. The average log₁₀ MPN per gram fresh weight (log₁₀ MPN gfw⁻¹) in stored samples in May and June was 0·78 ( S.D. 0·71) compared to 2·07 ( S.D. 0·70) in November and December. Campylobacters were readily detected in samples of mature slurry and composted bedding that farmers were about to put to land. The survival of campylobacters in slurry sprayed on land was studied in two seasons. In June, on farm A, stored slurry was mechanically aerated for 48 h and very low numbers of campylobacters (0·9 log₁₀ MPN gfw⁻¹) remained in the slurry before it was sprayed onto land. They became undetectable within 24 h once sprayed on land. In contrast, campylobacters in matured but unaerated slurry that was sprayed onto land on farm B in February were still detectable in samples taken 5 d after application to land, dropping from 2·11 log₁₀ MPN gfw⁻¹–1·37, a decline of only 0·74 log₁₀ MPN gfw⁻¹ in the first 5 d after application.     

Incidence and Spoilage Potential of Isolates from Vacuum-packaged Meat of High pH Value

Meat of high pH value (6·6) showing dark-cutting characteristics was vacuum-packaged and stored for up to 8 weeks at 0–2°C. 'Off'-odours were detected on opening the packages after 6 weeks of storage. Total counts at this stage were ca. 10⁷/cm² of which lactobacilli were the major component, with ca. 10⁶/cm² Gram negative organisms. Psychrotrophic Enterobacteriaceae represented a major proportion of the microflora only after the full 8 weeks of storage and were not detected previously. Aerobic storage of steaks cut from the vacuum packaged meat stored for 8 weeks resulted in a predominantly Gram negative spoilage flora.
Inoculation studies on meat of normal pH value (5·4) and appearance using representative isolates from the vacuum-packaged meat microflora indicated that most of the test organisms were capable of causing spoilage under aerobic conditions but few under vacuum-packaging when incubated at 4°C. On meat of higher pH value (6·15) many of the Gram negative isolates did not grow as well, whereas the Gram positive isolates grew better than on meat of normal pH value when held under aerobic conditions. Under vacuum-packaging all but one isolate grew as well or better on meat of high pH value than on normal meat at 4°C and objectionable odours were more marked.     

Improved PCR detection sensitivity of Erwinia carotovora subsp. atroseptica in potato tuber peel extract by prior enrichment on a selective medium

A simple and sensitive method was developed to replace the need for complex and laborious DNA extraction to remove inhibitory substances in potato tuber peel extract before detection of Erwinia carotovora subsp. atroseptica (Eca) by PCR. Eca was enriched by a factor of 10⁵ when peel extract was inoculated onto a selective medium, CVP, and incubated at 27°C for 24 h. Bacterial micro-colonies which developed were suspended in 500 μl of water and the bacteria diluted in water 100-fold, or 10-fold followed by washing by centrifugation, before PCR testing. The sensitivity of detection obtained with the former was ca 10¹–10² cells ml⁻¹ and with the latter ca 10¹ cells ml⁻¹, when different numbers of streptomycin-resistant Eca strain were added to peel extract from three Eca-free potato cultivars. The method was validated and the sensitivity confirmed relative to two different commonly used Eca detection methods using naturally contaminated tubers.     

Thermoregulation and metabolism in the Cape golden mole (Insectivora: Chrysochloris asiatica)

The Cape golden mole, Chrysochloris asiatica is an insectivore which excavates superficial foraging burrows as it searches for its food. It has a mean (±S.D.) resting metabolic rate (RMR) when newly captured of 1–17±0.17 cm³ O₂g^-1 h^-1 ( n = 14), within the thermoneutral zone (TNZ) of 30–32°C.
The body temperature (Tb) of the mole in the TNZ is low 32.9 ± 0.36 ( n = 14) and remains stable at ambient temperatures (Tas) from 28–32°C. Above 32°C (range 34–37°C), Tb increases albeit slightly to 36 ± 1.75°C ( n = 14). The conductance is high 0.27 ± 006cm³ O₂g^-1 h^-l°C^-1 ( n = 46) at the lower limit of thermoneutrality. The mean RMR at 9°C (the lowest Ta tested) was 4.82±11 cm³ O₂g^-1h^-1, which is 4.1 times that of the RMR in the TNZ.
At an ambient temperature of 9°C, three of the golden moles entered a state of torpor where the RMR was reduced from 5.9±0.56 to 10 1.0 ± 0.69cm³O₂g^-1h^-1.     

The effects of medium and rate of freezing on the survival of chlamydias after lyophilization

The effects of suspension media and rate of freezing on the survival of Chlamydia trachomatis LGV₂ and Chlamydia pneumoniae after lyophilization were assessed. The highest loss in infectious elementary bodies (EBs) occurred during lyophilization. The survival was higher after freezing at a rate of 1°C min^-1 and lyophilization than that after rapid freezing at - 70°C or - 196°C. The recovery (± 5%) was higher when fetal calf serum (FCS) containing glucose, saccharose or lactose were used as lyophilization media than that (0.5–3%) when yolk-sac, skimmed milk or phosphate buffer containing sucrose, glutamine and 10% FCS (SPG) were used. After lyophilization, the survival was not affected in the tested range from 10⁴ to 5 times 10⁶ inclusion-forming units (ifu) ml^-1 prior to freezing. After storage for 4 months at 4°C, the numbers of ifu of both Chlamydia serovars that were recovered were identical to the numbers of ifu immediately after lyophilization. It was concluded that chlamydias can be stored and transported in lyophilized form. However, a loss of 95% in infectious EBs should be taken into account.     

THE SANITATION OF FISH BOXES. I. THE QUANTITATIVE AND QUALITATIVE BACTERIOLOGY OF COMMERCIAL WOODEN FISH BOXES

SUMMARY: The cleaning efficiency of hosing wooden market fish boxes with cold water, the usual commercial practice, was very low, even when high pressure jets were used. After washing, the internal surfaces could still carry up to 20 × 10⁶ bacteria/cm². Even prolonged steaming failed to sterilize the surfaces. Coryneform organisms accounted for over 50% of the total bacterial flora, although these have usually been reported as present in only low proportions on both fresh and spoiling fish. The major subsidiary groups were species of Achromobacter and Pseudomonas , constituting about 18% and 14% of the population respectively. A few micrococci and flavobacteria were also present.
The conditions of counting, i.e. whether roll tubes or Petri dishes were used, whether incubation was at 0°, 20° or 37°, and whether the media were based on sea or tap water, could markedly influence both the magnitude of the count and the proportions of the different types of bacteria which could be isolated.     

Production and storage of Rhizobium leguminosarum cell concentrates for use as inoculants

Recovery of Rhizobium leguminosarum cells by centrifugation after growth in an industrial fermenter was 100-fold higher when cells were grown on yeast extract (5 g/1) as sole source of carbon and nitrogen when compared with the yields recovered when cells were grown in standard mannitol-yeast extract medium. Methods of storing concentrated suspensions of R. leguminosarum were investigated. Freeze-drying caused a marked decrease in viable cell numbers. Viable cell numbers of bacterial concentrates stored in peat decreased steadily from 10₁₁-10₁₂ cfu/g to 10₉ cfu/g or less during 26 weeks storage at room temperature or at 4°C. Cell concentrates stored in 40% glycerol at — 20°C maintained viable numbers higher than 10₁₁ cfu/ml during a 76 week storage period.     

Scaling of oxygen consumption of Lake Magadi tilapia, a fish living at 37°C

Rates of oxygen consumption were measured in the geothermal, hot spring fish, Oreochromis alcalicus grahami by stopped flow respirometry. At 37° C, routine oxygen consumption followed the allometric relationship: V o₂=0.738 M ^0.75, where V o₂ is ml O₂ h ⁻¹ and M is body mass (g). This represents a routine metabolic rate for a 10 g fish at 37° C of 0.415 ml O₂ g⁻¹ h ⁻¹ (16.4 μmol O₂ g ⁻¹ h ⁻¹). Acutely increasing the temperature from 37 to 42° C significantly elevated the rate of O₂ consumption from 0.739 to 0.970 ml O₂ g ⁻¹ h ⁻¹ ( Q ₁₀=l.72). In the field, O. a. grahami was observed to be 'gulping' air from the surface of the water especially in hot springs that exceeded 40° C. O. a. grahami may utilize aerial respiration when O₂ requirements are high.