Decline In Bacterial Numbers Research Articles

Safety in Serbian animal source food industry and the impact of hazard analysis and critical control points: A review

There is a significant lack of HACCP-educated and/or HACCP-highly trained personnel within the Serbian animal source food workforces and veterinary inspectors, and this can present problems, particularly in hazard identification and assessment activities. However, despite obvious difficulties, HACCP benefits to the Serbian dairy industry are widespread and significant. Improving prerequisite programmes on the farms, mainly through infrastructural investments in milk collectors and transportation vehicles on one hand, and increasing hygiene awareness of farmers through training on the other hand has improved the safety of milk. The decline in bacterial numbers on meat contact surfaces, meat handlers’ hands and cooling facilities presents strong evidence of improved process hygiene and justifies the adoption of HACCP in Serbian meat establishments. Apart from the absence of national food poisoning statistics or national foodborne disease databases, the main obstacle to fully recognising the impact of HACCP on the safety of animal source food in Serbia is the lack of research regarding the occurrence of chemical and/or physical hazards interrelated with its production.

The air-borne distribution of zoonotic agents from livestock waste spreading and microbiological risk to fresh produce from contaminated irrigation sources.

To assess the risks of zoonotic agents in dissemination of livestock wastes into the environment by airborne distribution. To subsequently assess the survival time of zoonotic agents, introduced in irrigation water, on the phylloplane of produce. An Escherichia coli marker was introduced into pig slurry which was spread using a rain gun sprayer. Air sampling was undertaken to determine the distance reached by the marker. No recoveries were observed at a distance of 250 m. Borehole water, contaminated with zoonotic agents, was used to irrigate field plots sown with lettuce and spinach. Decline in bacterial numbers on the phylloplane was observed with time. After initial rapid decreases, we were unable to detect any pathogen from the phylloplane, 1 month after contamination. These preliminary results suggest that the risks to public health from the aerosolized spread of bacteria during slurry spreading by rain gun are low. Although, zoonotic agents on crop phylloplanes perish quickly, the risks of overhead irrigation of fresh produce 3 weeks before harvest should still be considered. These preliminary results improve our understanding on the fate of zoonotic agents in the environment. Spreading liquid livestock wastes by an airborne mechanism may not pose a significant public health risk. Detection of zoonotic agents 3 weeks after contamination of lettuce and spinach means that consideration should be given by the farmers until the time of harvest, when irrigating fresh produce with water that may have been directly or indirectly contaminated by livestock wastes.

Survival of bacteria on wood and plastic particles: Dependence on wood species and environmental conditions

AbstractThe survival of two hygienically relevant bacteria,Escherichia colipIE639 andEnterococcus faecium, was followed on wooden sawdust of seven different European woods (pine, spruce, larch, beech, maple, poplar, and oak) versus polyethylene chips by using cultivation-dependent and molecular-based methods in parallel. The survival of the bacteria on wood was dependent on various factors such as the wood species, the type of the inoculated bacterium, the ambient temperature, and humidity. The bacterial titre decreased fastest on pine followed by oak compared to the other woods and plastic. Cultivation-independent analysis employing DNA extraction, Southern blot hybridisation, and PCR-based detection of marker genes of the test bacteria confirmed this result. The decline in bacterial numbers correlated with the decrease of bacterial DNA in the samples. Amounts of DNA ofE. coliandE. faeciumrecovered from pine and oak-wood sawdust were generally lower compared to the other woods and plastic.The presented study shows that pine and oak exhibit substantially better hygienic performance than plastic and indicates an antibacterial effect caused by a combination of the hygroscopic properties of wood and the effect of wood extractives.

Influence of Modified Natural or Synthetic Surfactant Preparations on Growth of Bacteria Causing Infections in the Neonatal Period

Connatal bacterial pneumonia is common in neonates. Animal studies and initial clinical reports indicate that surfactant dysfunction is involved in the pathophysiology of severe neonatal pneumonia. Since respiratory distress syndrome and connatal pneumonia may be difficult to differentiate in the first hours of life, neonates with respiratory failure due to bacterial infections might receive surfactant. Under such conditions surfactant components might be catabolized by bacteria and promote bacterial growth. We therefore investigated the influence of three modified natural (Curosurf, Alveofact, and Survanta) and two synthetic (Exosurf and Pumactant) surfactant preparations on the growth of bacteria frequently cultured from blood or tracheal aspirate fluid in the first days of life. Group B streptococci (GBS), Staphyloccocus aureus, and Escherichia coli were incubated in a nutrient-free medium (normal saline) for 5 h at 37 degrees C, together with different surfactants at concentrations of 0, 1, 10, and 20 mg/ml. With the exception of E. coli, incubation in saline alone led to a variable decrease in CFU. In the presence of Alveofact, Exosurf, and Pumactant the decline in bacterial numbers was less marked than in saline alone. Curosurf was bactericidal in a dose-dependent fashion for GBS and had a strong negative impact on the growth of a GBS subtype that lacked the polysaccharide capsule. In contrast, Survanta (10 and 20 mg/ml) significantly promoted the growth of E. coli, indicating that surfactant components may actually serve as nutrients. We conclude that bacterial growth in different surfactant preparations is influenced by microbial species and the composition and dose of the surfactant. Further studies are necessary to elucidate the mechanisms behind our findings and to evaluate the effects of surfactant on bacterial growth in vivo.

The effect of the time of sampling on the compliance of bathing water in NW England with the EU Directive on bathing water quality

The ability of Morecambe’s three designated bathing waters to pass the EU Directive on Bathing Water Quality depends on the time of day when the sample is taken, the indicator organism tested for and whether the test uses the most strict (Guideline) or the least strict (Imperative) criteria. Morning and afternoon sampling for faecal coliforms, faecal streptococci and the pathogenCampylobacter was carried out monthly over the 1996 and 1997 bathing seasons. In the afternoons average faecal coliforms declined by 77% in 1996 and 87% in 1997 compared with the mornings, faecal streptococci by 79% and 83% and campylobacters by 66% and 86%. This decline in bacterial numbers between morning and afternoon was related to variations in water temperature and levels of ultraviolet radiation. All three bathing waters failed the Guideline criteria of the EU Directive on Bathing Water Quality. Using the Imperative criteria, no bathing waters passed in the mornings of either year, some passed in the afternoons of 1996 and all passed in the afternoons of 1997. The increased pass rate in 1997 coincided with improved sewage treatment, high temperatures and increased levels of sunshine. In 1997 sampling by the Environment Agency produced fewer failures than our morning sampling but more than our afternoon sampling. Their sampling was done around midday. It is suggested that where possible all sampling of EU designated bathing waters should be carried out in the early morning.

Progress Towards a New Tuberculosis Vaccine

New weapons are needed in the fight against tuberculosis, both antibacterial drugs and a vaccine. If one new antituberculosis drug is developed it will encounter emerging resistance; at least two are needed, to be used in combination only. This is a complicated and difficult goal. In contrast, an effective new vaccine would have multiple antigenic targets within the bacterium, making the emergence of resistance to the vaccine unlikely. This is a simpler goal to achieve, and recent research indicates that it may be within reach. A diverse range of protein antigens can give encouragingly high levels of protective immunity in animal models when administered with adjuvants or as DNA vaccines. Accelerated arrest of bacterial multiplication, followed by sustained decline in bacterial numbers, are key parameters of protection; the vaccine must target antigens produced by actively multiplying bacteria as well as growth-inhibited bacteria. Consistent with this, the protective antigens have been found among secreted and stress proteins (for example Ag85, ESAT-6, hsp65, hsp70). Species-specific antigens are not required, so these remain available for diagnostic tests. Adoptive transfer of protection from vaccinated or infected mice into naive mice by transfer of purified T cells and clones shows that protection is expressed by antigen-specific cytotoxic T cells that produce interferon-gamma and lyse infected macrophages. These cells are produced in response to endogenous antigen. DNA vaccination appears to be superior to recombinant mycobacterial or viral vectors for this purpose.

Development of an intraperitoneal implant chamber for the study of in vivo-grown Pasteurella haemolytica in cattle

An intraperitoneal implant chamber was developed for the study of the in vivo growth of Pasteurella haemolytica in calves. The chamber had a volume of approximately 100 ml and featured an external sampling port which allowed multiple and sequential sampling of the chamber contents. A single polycarbonate diffusion membrane with a pore size of 0.22 μm allowed host peritoneal fluid to diffuse into the chamber and maintained the bacterial population free of white blood cells. Chambers were implanted into the peritoneal cavities of four five-month-old dairy-cross calves, demonstrated to be sero-negative by indirect haemagglutination assay. Three days later, four different P. haemolytica isolates, of serotypes A1 or A2, were inoculated into the chambers. In all cases, there was a slow decline in the viable bacterial numbers within the chambers. Western blot analysis of the antibody content of the chamber fluids revealed IgG antibodies to P. haemolytica OMPs in the fluid prior to inoculation and both 9 and 15 days after inoculation. Furthermore, there was no significant change in the IgG antibody content of the chamber fluid, either quantitatively or qualitatively, during the course of the experiment. Analysis of the bactericidal activity of pre-inoculation chamber fluid against the corresponding bacterial isolate suggested that an antibody-dependent complement-mediated process was not responsible for the decline in bacterial numbers. Overall, the chamber design was demonstrated to be extremely effective for in vivo studies of P. haemolytica in calves, allowing easy and regular sampling of the chamber contents and maintaining bacteria free of white blood cells. Although there was a slow decline in bacterial numbers over time, sufficient numbers of cells could be obtained for analysis of cell-surface antigens.

Disturbance associated with bait-collection for sandprawns (<I>Callianassa kraussi</I>) and mudprawns (<I>Upogebia africana</I>): Long-term effects on the biota of intertidal sandflats

The sandprawn Callianassa kraussi and the mudprawn Upogebia africana are used extensively as fish bait in southern Africa. A holistic analysis of disturbance associated with experimental prawn-collecting was undertaken to determine its repercussions upon the sediment and associated macrofaunal, meiofaunal, microbial and microalgal communities. Patterns of recovery were examined for 18 months following the disturbance. The recovery of both C. kraussi and U. africana was far more protracted than predicted, taking 18 months for completion. Sedimentary compaction, associated with the removal of prawns, could account for these prolonged recoveries. Both C. kraussi and U. africana suffered greater depressions of population densities (ca. 70%) than would have been expected from the proportions removed (ca. 10% and 46% respectively). This suggests that disturbance and sedimentary compaction have greater effects than the removal of sand- and mudprawnsper se. One month after the disturbance of C. kraussi, chlorophyll levels increased above control levels and remained elevated for a further 2-3 months. In contrast, the removal of U. africana resulted in nett decreases in chlorophyll levels for approximately one month following the disturbance. A short-lived decline in bacterial numbers was apparent following the removal of C. kraussi but not U. afiicana. Meiofaunal numbers declined immediately after disturbance of both C. kraussi and U. aficana, but this depression was followed by explosive increases and then a return to control levels. The macrofauna was slower to recover and, after initial reductions of numbers, biomass and species richness, still showed signs of depression 18 months after the disturbance. Three response patterns were apparent: species which were immediately reduced by the treatments and were also slow to recover; species which appeared to have their recruitment suppressed relative to the control; and species which were unaffected by the treatment. Only a single macrofaunal species, the hermit crab Diogenes brevirostris, benefited from the disturbance. Similar trends were observed following the harvesting of both C. kraussi and U. africana.

Evaluation of activity of temafloxacin against Bacteroides fragilis by an in vitro pharmacodynamic system

An in vitro pharmacodynamic system has been successfully adapted to simulate in vivo antimicrobial pharmacokinetics under anaerobic conditions. This system was used to perform time-kill kinetic studies which were designed to compare the activity of temafloxacin to ciprofloxacin and cefotetan against two strains of Bacteroides fragilis (ATCC 25285 and ATCC 23745). All experiments were performed as single-dose, 24-h, duplicate runs. Starting bacterial inocula of 10(7) CFU/ml were exposed to starting antimicrobial concentrations of 5 micrograms of temafloxacin per ml, 5 micrograms of ciprofloxacin per ml, and 100 micrograms of cefotetan per ml. Terminal half-lives of 8, 4, and 4 h were simulated for each antimicrobial agent. Temafloxacin was rapidly bactericidal against B. fragilis. Ciprofloxacin was not bactericidal (< 3 log10 unit decline in bacterial numbers) to either strain of B. fragilis. Cefotetan was bactericidal (> or = 3 log10 unit decline in bacterial numbers) to each strain but killed at a slower rate than temafloxacin. Times to 3 log10 unit declines of strain ATCC 25285 were 2, 4, and > 24 h, whereas those of strain ATCC 23745 were 4, 4, and > 24 h for temafloxacin, cefotetan, and ciprofloxacin, respectively. Total logarithmic declines of strain ATCC 25285 were > 4.5, > 4.5, and 2.9 log10 CFU/ml, whereas those of strain ATCC 23745 were 4.1, > 4.5, and 1.2 log10 CFU/ml for each drug, respectively. These and other studies demonstrated that temafloxacin showed potential as an agent that could have been further developed for use in the treatment of anaerobic infections. However, the drug was removed from the market by its manufacturer because of toxicity issues. Although the release of newer fluoroquinolones that possess significant activity against anaerobic bacteria does not appear imminent, the time-kill studies performed in this study demonstrate that further research is warranted in the development of fluoroquinolones which possess significant antianaerobic activity.

Bacterial activities in the Dead Sea, 1980-1991: survival at the upper limit of salinity

Since the mass development of halophilic bacteria in 1980 and the subsequent decline of the community in 1982, no new mass development of bacteria has occurred in the Dead Sea, and bacterial numbers have remained extremely low. The lake’s salinity, and more specifically the divalent cation concentration, have increased greatly during the last ten years. To quantitate the activity of the community of heterotrophic bacteria in the Dead Sea water column, rates of incorporation of amino acids, glycerol, and acetate were measured, both during the 1980–1981 bloom and in recent years. With the development of the bloom, rates of incorporation amino acids, glycerol and acetate increased. Concomitant with the decline in bacterial numbers, the incorporation rates of amino acids and acetate decreased at the end of 1980-beginning of 1981, while glycerol incorporation rates remained high for one more year. Measurements in 1989 and in 1991 showed very low but significant incorporation rates (three to four orders of magnitude lower than during the 1980–1981 bloom). By the use of specific inhibitors, it was shown that the remaining activity was due to halophilic archaeobacteria. The mechanism of the long-term survival of a small active bacterial community in the Dead Sea in the absence of primary producers and other obvious sources of organic carbon, and at divalent cation concentrations greatly exceeding those enabling growth, is still unknown.

Thermal susceptibility of Streptococcus faecium strains isolated from frankfurters

The heat resistance of nine strains of Streptococcus faecium isolated from frankfurters was determined at 63 and 68 degrees C in brain heart infusion broth. Exponential-phase cultures (approximately 10(7) colonies/mL) were used as inoculants. The heat resistance of S. faecium DP2181, a moderately resistant isolate, was further examined in broth (55, 63, and 68 degrees C) and frankfurter emulsion (63 and 68 degrees C). The decimal reduction times (D values) were determined by regression. In broth, both time-temperature combinations resulted in a 3-4 log decline in bacterial numbers for the nine S. faecium strains tested. For S. faecium DP2181, the survivor curves deviated from the logarithmic order of death at all three heating temperatures. An initial slow period of death was evident at 55 degrees C and a resistant tail of organisms was observed at 55, 63, and 68 degrees C. The D55D63, and, D68 values for the logarithmic portion of the corresponding survivor curves were 105.6, 9.36, and 3.34 min, respectively. The survival of DP2181 was enhanced by the frankfurter emulsion. The results indicate that populations of S. faecium existed that were very heat resistant and could survive normal frankfurter processing if initially present in high numbers.

Temporal development of protective cell-mediated and humoral immunity in BALB/c mice infected with Brucella abortus.

In BALB/c mice infected i.v. with attenuated strain 19 of Brucella abortus, the organism replicates to high numbers in the spleen and reaches peak concentrations at 2 wk postinfection (p.i.). The infection is then progressively cleared so that by 8 wk p.i. numbers of bacteria have decreased 10,000 fold or more. Passive transfer assays were performed with T cell-enriched spleen cells and serum of donor mice infected 2, 3, 4, 5, 6, or 8 wk previously. Antibodies conferred significant protection to recipients at and after 3 wk p.i., whereas protection by T cells was not evident until 4 wk p.i. The combined transfer of serum and cells enhanced protection over that provided by serum or cells alone when transfers were made before, but not after, challenge infection. Protection conferred by T cell-enriched spleen cells of 6-wk donors was unaffected by the presence of equal quantities of cells from 3-wk donors, but was abrogated by the removal of both CD4 and CD8 T cell subsets. Experiments with purified CD4 and CD8 subsets revealed that cell-mediated protection resided at equivalent levels in both subsets. Daily treatment of mice with Cyclosporin A for 4 wk after infection caused some increase in numbers of brucellae in spleens and livers. Although immune responses of treated animals were markedly suppressed, there was little effect of treatment on numbers of macrophages in the spleen, on enhanced killing of Listeria monocytogenes in the spleen, or on the nature and intensity of splenic and hepatic inflammatory responses. These data indicate that acquired resistance to infection with B. abortus in mice is the result of independent, and probably also interactive, effects of antibodies and T effector cells of both CD4 and CD8 phenotypes. The initial decline in bacterial numbers in the spleen, which occurred in the absence of detectable cell-mediated immunity in that organ, could probably be ascribed principally to effects of antibodies and to nonimmune stimuli responsible for increased formation, attraction, and activation of macrophages.

Bacterial growth on macrophyte leachate and fate of bacterial production1

The role bacteria play in transferring organic carbon to other trophic levels in aquatic ecosystems depends on the efficiency with which they convert dissolved organic carbon into bacterial biomass and on the ability of consumers to graze bacteria. We have measured the conversion efficiency for bacteria growing on macrophyte‐derived dissolved organic carbon and estimated the amount of bacterial production removed by grazing. Bacteria converted this DOC into new tissue with an efficiency of 53%, substantially higher than the apparent conversion efficiency of macrophyte‐derived particulate organic carbon or other types of DOC. Two estimates of grazing indicate that the decline in bacterial numbers after the bloom was probably due to grazing by flagellates. These results show the significance of the bacterial link between DOC and other trophic levels.

Role of resident macrophages, peripheral neutrophils, and translymphatic absorption in bacterial clearance from the peritoneal cavity.

Microbial pathogens within the peritoneal cavity are thought to encounter three categories of host defense mechanisms: (i) removal mechanisms, which occur via diaphragmatic lymphatic absorption; (ii) killing mechanisms, in which host phagocytes act as effector cells; and (iii) sequestration mechanisms due to fibrin trapping and the formation of adhesions between visceral surfaces. We sought to define and quantitate the relative role of the first two components in an experimental rat model of Escherichia coli peritonitis in which fibrinous adhesions do not form. Intraperitoneal challenge with greater than or equal to 2 X 10(8) CFU of viable E. coli led to an initial decline in bacterial numbers followed by ongoing proliferation and greater than 50% mortality. With inocula of less than or equal to 5 X 10(7) CFU, elimination of bacteria occurred after moderate initial proliferation, and no mortality ensued. Nonviable, radiolabeled E. coli organisms were utilized to examine bacterial clearance via translymphatic absorption and phagocytosis. Both processes were extremely rapid, serving to eliminate free bacteria rapidly within the peritoneal cavity. Although macrophages and polymorphonuclear leukocytes within the peritoneal cavity demonstrated similar phagocytic capacities, the predominance of macrophages at the time of the initial bacterial insult led to the conclusion that these cells, in addition to translymphatic absorption, represent the first line of host defenses, acting to eliminate bacteria in the incipient stages of infection.

A PRELIMINARY ANALYSIS OF BACTERIAL NUMBERS AND BIOMASS IN LANGEBAAN LAGOON

Summary Water samples taken down the length of Langebaan lagoon reveal a decline in bacterial numbers from Saldanha Bay to the head of the lagoon, with a parallel decline in suspended particles. Bacterial biomass (x 43, 27 mg.m−3) was comparable to zooplankton biomass. Intertidal samples from different sediment types showed an increase of bacteria towards the southern tip of the lagoon, with decrease in particle size and increases in percentage mud and percentage organic material. Bacteria comprise only a small percentage of the organic pool, but their biomass ranges from 16 to 232 mg (dry weight) per kg of wet sediment. This approximates a mean of 14,2 g (dry weight) per m2 (range 1,32 to 25,74): comparable to the biomass of benthic macrofauna. Considerable seasonal variation occurs in the organic pool.