Increase In Bacterial Counts Research Articles

Mouse milk bacterial count in coagulase negative staphylococcus species induced mastitis

Bovine mastitis in an economically important disease of dairy cattle and caused by multi etiological factors. In the present study, milk viable bacterial count in mouse mastitis induced by Staphylococcus epidermidis, S. chromogenes, S. haemolyticus and S. aureusisolated from apparently normal bovine milk was studied. The 2 x 104CFUorganisms in 50 µl per teat were inoculated through intramammary route in 4th and 5th pairs of abdominal mammary gland in mice. The mouse milk ranging from 50 to 200 µl per mice wascollectedat 6, 12, 24, 48, 72 and 96 hrs after intramammary inoculation. The milk was diluted with sterile PBS and subjected to bacterial countby pour plate method. The viable bacterial count in mice milk showed significant (P<0.05) increase in bacterial colonies at 12, 24, 48 and 72hrs after S. aureus infection in mice. The three coagulase negative staphylococci(CNS) species showed initial increase in bacterial counts at 12 and 24 hrs but declined from 48 to 96 hrs after IMI in mice. Thus, CNS species can increase the mice viable bacterial count moderately but ten to fifteen fold increase was observed in S. aureus infected mice mammary gland.This indicated the subclinical nature of CNS intramammaryinfection in mice and also the host ability to overcome and eliminate the CNS infection. Mouse is a suitable model to study coagulase negative staphylococcus species induced bovine subclinical mastitis.

Aerosols Contamination in the Dental Practice Following Everyday Procedures: An Observational Study.

The purpose of the present observational study was to evaluate the bacterial load in the air following various dental procedures. Air contamination following seven aerosol-generating dental procedures was assessed. The air volume was sampled by a wet cyclone collector for 10 min during 10 sessions of the following procedures: air-polishing, ultrasonic instrumentation, manual instrumentation, rubber cup polishing, cavity preparation with a 1:5 red contra-angle, cavity preparation with turbine and Low Volume Evacuator (LVE), and cavity preparation with turbine and High Volume Evacuator (HVE). Contamination of the sampled solution was determined using ATP (Adenosine TriPhosphate) quantification of the viable bacterial count, and compared to baseline measurements. The baseline air contamination was 1.45 (0.85-2.04) CFUs/L of air. The highest increase in air contamination was observed after the use of a turbine with LVE, with an average of 7.38 (95% CI 3.87-10.89) CFUs/L of air (p < 0.01). The use of the turbine with HVE and the use of the red hand-piece resulted in non-significant increases in bacterial counts compared to baseline (2.98 [1.34-4.63] and 2.70 [0.18-4.22] CFUs/L of air respectively). The application of air polishing, ultrasonic instrumentation, hand instrumentation and rubber cups did not result in a higher bacterial count than the baseline. Routine professional oral hygiene procedures do not increase air contamination. However, cavity excavation with LVE creates a significantly higher bacterial count in the air.

Effect of Oral Application of Povidone-Iodine on the Amount of Viable Bacteria Entering the Lower Respiratory Tract in Intubated Patients With Oral Cancer: A Preliminary Study.

One of the causes of ventilator-associated pneumonia (VAP) is the aspiration of fluid-containing pathogenic bacteria into the lower respiratory tract. The purpose of this study was to determine whether oral povidone-iodine (PV-I) application reduces bacterial counts in the fluid on the cuff of an endotracheal intubation tube. Patients intubated and managed with tracheostomy for oral cancer surgery were divided into two groups. The PV-I group received a single topical application of PV-I in the oral cavity. The brushing group underwent tooth brushing with suction and cleaning. Before the intervention, and at one, two, three, and six hours after intervention, samples were taken from the mouth and the cuff to determine viable bacterial counts using the delayed real-time polymerase chain reaction method, which quantifies only viable bacteria. Seven patients in the PV-I group and six in the brushing group were included in the study. The brushing group showed an increase in bacterial counts in both the oral cavity and on the cuff up to six hours post intervention. In contrast, the PV-I group showed significantly lower bacterial counts from one to six hours post intervention, both in the oral cavity and on the cuff. These results indicate that topical PV-I application reduces the number of bacteria entering the lower respiratory tract and may help prevent VAP.

Salmonella pathogenicity island-14 is a critical virulence factor responsible for systemic infection in chickens caused by Salmonella gallinarum

Salmonella enterica serovar Gallinarum (S. gallinarum) is an important host-specific pathogen that causes fowl typhoid, a severe systemic, septicemic, and fatal infection, in chickens. S. gallinarum causes high morbidity and mortality in chickens and poses a significant burden and economic losses to the poultry industry in many developing countries. However, the virulence factors and mechanisms of S. gallinarum-induced systemic infection in chickens remain poorly understood. In this study, we constructed a Salmonella pathogenicity island-14 (SPI-14) mutant strain (mSPI-14) of S. gallinarum and evaluated the pathogenicity of mSPI-14 in the chicken systemic infection model. The mSPI-14 exhibited the same level of bacterial growth and morphological characteristics but significantly reduced resistance to bile acids compared with the wild-type (WT) strain in vitro. The virulence of mSPI-14 was significantly attenuated in the chicken oral infection model in vivo. Chickens infected with WT showed typical clinical symptoms of fowl typhoid, with all birds succumbing to the infection within 6 to 9 days post-inoculation, and substantial increases in bacterial counts and significant pathological changes in the liver and spleen were observed. In contrast, all mSPI-14-infected chickens survived, the bacterial counts in the organs were significantly lower, and no significant pathological changes were observed in the liver and spleen. The expression of interleukin (IL)-1β, IL-12, CXCLi1, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ in the liver of mSPI-14-infected chickens were significantly lower than those in the WT-infected chickens. These results indicate that SPI-14 is a crucial virulence factor in systemic infection of chickens, and avirulent mSPI-14 could be used to develop a new attenuated live vaccine to prevent S. gallinarum infection in chickens.

Microbiological Quality and Safety of Brazilian Mozzarella Cheese During Production Stages.

This study assessed the microbiological quality and safety of mozzarella during various production stages in northern Tocantins, Brazil, by identifying critical biological points in the industrial environment within a tropical climatic region. Batches of mozzarella were evaluated, from raw milk to primary packaging, with a shelf life of 120 d at 4°C. Indicator microorganisms were quantified, and through microbiological and biomolecular approaches, Salmonella spp. and Listeria monocytogenes were identified. In addition, the toxigenic potential of coagulase-positive staphylococci (CPS) was characterized. Results indicated that the raw milk used for mozzarella production had low microbiological quality; pasteurization of raw milk effectively eliminated all identified pathogens and reduced microbiological counts (p > 0.05). An increase in bacterial counts (>2 log colony-forming unit [CFU]/g) and recontamination with Salmonella spp. and CPS, which potentially produce staphylococcal enterotoxin B, were observed during milk coagulation and curd draining. Stretching of the fermented curd reduced the enterobacteria, total coliforms, and Escherichia coli median values by 2.56, 2.64, and 2.3 log CFU/mL, respectively. Similarly, brining the pieces by immersion reduced the quantity of enterobacteria and total coliforms by 2.3 and 1.6 log CFU/mL, respectively. Of interest, in the freshly finished product, Salmonella spp. was present but L. monocytogenes was absent; however, after the shelf-life period, L. monocytogenes was present but Salmonella spp. was absent. Considering the environmental conditions that can promote the multiplication and preservation of pathogens and spoilage of dairy products in tropical climates, it is necessary to review operational hygiene procedures, particularly in milk coagulation vats and fermentation tables. This will ensure the production of high-quality mozzarella cheese with a reduced consumption risk.

In vitro evaluation of enterococcus faecalis growth in different conditions on dentinal substrate

The aim of this study was to find the best growth conditions of Enterococcus faecalis on a dentinal substrate in order to be used for the development of a complex multispecies endodontic biofilm. Fifty two single rooted extracted human teeth and fifty two dentinal disks were mechanically prepared, sterilized, inoculated with Enterococcus faecalis and divided randomly into 8 groups where the substrate, the inoculation technique, the medium type, and the pre-treatment with collagen type I was varied. Bacterial count was evaluated and colonies were counted and confirmed by colony morphology observation on blood agar and Gram staining at 3,7, 14, 21, and 28 days. On day 14 of the culture, the bacterial count showed the highest values in all groups. Root canals and Type 1 collagen pre-treatment and glucose proved to have significant positive effects on the bacterial count compared to dentinal disks and BHI media only. The increase in bacterial count found with the direct inoculation technique was not significantly different from that of the indirect technique.

Conjunctival and nasal microbiota evaluation of dogs submitted to dacryocystorhinostomy

The purpose of this study was to evaluate changes in the conjunctival and nasal microbiota, in the long term, of dogs undergoing bilateral dacryocystorhinostomy. Twelve male and female dogs (23 eyes), aged between 1 and 10 years, were enrolled in the study, selected on the basis of presentation with epiphora and chromodacryorrhea for at least six months. Cultures of material obtained from the ocular conjunctiva and nasal sinus of all dogs were evaluated to determine the conjunctival and nasal microbiota pre-and postoperatively (at 60, 120, and 240 d). Preoperatively, gram-negative bacteria were identified in the conjunctival microbiota of 66.5% (n=8), while gram-positive bacteria were found in 33.3% (n=4). Throughout the clinical evolution, a balance was found between the presence of gram-positive and gram-negative bacteria in the conjunctival microbiota. Pure cultures of Pseudomonas aeruginosa (25%) and Staphylococcus intermedius (25%) were found most frequently. Regarding the conjunctival microbiota, we can conclude that in obstructive diseases, there is a predominance of gram-negative bacteria in the lacrimal system, notably Pseudomonas aeruginosa. This study did not observe an increase in bacterial counts in the nasal cavity through the new surgical pathway to the conjunctival sac.

SERS immunoassay analysis of Escherichia coli and Staphylococcus aureus based on sandwich-structured complex probe and target-induced strand displacement.

Adirect and ultra-sensitive surface-enhanced Raman scattering (SERS) immunoassay method is introducedfor the detection of Escherichia coli and Staphylococcus aureus. This methodology is based on a sandwich-structured complex probe (SCP) mechanism, combined with target-induced strand displacement. Moreover, by leveraging the amplified SERS signal from gold nanoparticles (AuNPs) corresponding to an increase in bacterial count, we achieve quantitative determination. The SCP demonstrates remarkable specificity, sensitivity, and anti-interference capability in bacterial detection. The detection limits for both bacterial strains are as low as 10CFU/mL. In our selectivity tests, all peak intensities had standard deviations (n = 3) below 6%. Recoveries in normal human serum were 101-110% for E. coli and 96-101% for S. aureus. In milk, the recoveries were 102-105% for E. coli and 100-105% for S. aureus, respectively, demonstrating a high level of accuracy and resistance to interference. In addition, the SCP offers a dual-detection capability, enabling simultaneous diagnosis of multiple targets, which greatly simplifies the testing procedure. The findings underscore that this immunoassay platform fulfills the demand for rapid and precise pathogenic bacterial diagnosis, holding substantial potential for practical applications.

Hypoxia-induced HIF-1α promotes Listeria monocytogenes invasion into tilapia.

HIF-1α is a nuclear transcription factor, and its activity is tightly regulated by the level of available oxygen in cells. Here, we investigated the roles of HIF-1α in the invasion of Listeria monocytogenes into tilapia under hypoxic environments. We found that the expression levels of HIF-1α in examined tissues of hypoxic tilapia were significantly upregulated, indicating that the tissue cells have been in hypoxic conditions. After 24-h infection with L. monocytogenes, we found that bacterial burden counts increased significantly in all examined tissues of hypoxic fish. To explore why the bacterial count increased significantly in the tissues of hypoxic fish, we modulated HIF-1α expression through RNAi technology. The results indicated that c-Met expression levels were positively related to HIF-1α expression. Since c-Met is the receptor of InlB that plays critical roles in the adhesion and invasion of L. monocytogenes, the ∆InlB strain was used to further explore the reason for the significant increase in bacterial counts in hypoxic fish. As expected, the decrease in the adhesion ability of ∆InlB suggested that InlB mediates L. monocytogenes infection in tilapia. After being infected with ∆InlB strain, we found that the bacterial counts in hypoxic fish were not affected by hypoxic conditions or HIF-1α expression levels. These findings indicate that HIF-1α may promote the internalization of InlB by upregulating c-Met expression and therefore contributes to the invasion of L. monocytogenes into hypoxic tilapia. IMPORTANCE Listeria monocytogenes is a zoonotic food-borne bacterial pathogen with a solid pathogenicity for humans. After ingestion of highly contaminated food, L. monocytogenes is able to cross the intestine invading phagocytic and nonphagocytic cells and causes listeriosis. China is the world's largest supplier of tilapia. The contamination rate of L. monocytogenes to tilapia products was as high as 2.81%, causing a severe threat to public health. This study revealed the underlying regulatory mechanisms of HIF-1α in the invasion of L. monocytogenes into tilapia under hypoxic environments. This study will be helpful for better understanding the molecular mechanisms of hypoxic environments in L. monocytogenes infection to tilapia. More importantly, our data will provide novel insights into the prevention and control of this pathogen in aquaculture.

Differentially culturable tubercle bacteria as a measure of tuberculosis treatment response.

Routine efficacy assessments of new tuberculosis (TB) treatments include quantitative solid culture or routine liquid culture, which likely miss quantification of drug tolerant bacteria. To improve these assessments, comparative analyses using additional measures such as quantification of differentially culturable tubercle bacteria (DCTB) are required. Essential for enabling this is a comparative measure of TB treatment responses using routine solid and liquid culture with liquid limiting dilutions (LLDs) that detect DCTB in sputum. We recruited treatment-naïve TB patients, with and without HIV-infection, and serially quantified their sputum for DCTB over the course of treatment. Serial sputum sampling in 73 individuals during their first 14 days of treatment demonstrated that clearance of DCTB was slower compared to routine solid culture. Treatment response appeared to be characterized by four patterns: (1) Classic bi-phasic bacterial clearance; (2) early non-responders with slower clearance; (3) paradoxical worsening with an increase in bacterial count upon treatment initiation; and (4) non-responders with no change in bacterial load. During treatment, LLDs displayed greater bacterial yield when compared with quantitative solid culture. Upon treatment completion, 74% [46/62] of specimens displayed residual DCTB and within this group, two recurrences were diagnosed. Residual DCTB upon treatment completion was associated with a higher proportion of MGIT culture, GeneXpert, and smear positivity at two months post treatment. No recurrences occurred in the group without residual DCTB. These data indicate that DCTB assays detect distinct subpopulations of organisms in sputum that are missed by routine solid and liquid culture, and offer important alternatives for efficacy assessments of new TB treatments. The residual DCTB observed upon treatment completion suggests that TB treatment does not always eliminate all bacterial populations, a finding that should be investigated in larger cohorts.

Bacteriological composition of groundwater and its role in human health

Bacteriological composition of groundwater and its role in human health

The Physicochemical, Microbiological, and Structural Changes in Beef Are Dependent on the Ultrasound System, Time, and One-Side Exposition.

The effect of high-intensity ultrasound (HIU) system (bath, 37 kHz and 90 W/cm2; or probe, 24 kHz and 400 W) and application time (25 or 50 min, one-side exposition) on the properties of bovine Longissimus lumborum after 7 d of storage at 4 °C was studied. The bath system significantly increased the lightness of the muscle, while other color parameters (a*, b*, hue, and chroma) were not different from the control. The water holding capacity and shear force decreased significantly (3.1–5% and 0.59–0.72 kgf, respectively) in sonicated meat independently of the system, favoring the tenderization of the muscle after storage. Microstructural changes observed in the HIU-exposed surface provided evidence of a higher area of interfibrillar spaces (1813 vs. 705 µm2 in the control), producing tenderization of the muscle, compared with the control. HIU significantly increased counts of total aerobic and coliform bacteria, especially after 50 min of ultrasonication. HIU also increased lactic acid bacterial counts in the bath system. Single-sided muscle exposition to ultrasound may produce sufficient significant changes in muscle properties, which could decrease long treatment times that would be needed for the exposition of both sides. HIU in bath systems increases tenderness by modifying meat ultrastructure, with no significant changes in physicochemical parameters. Nevertheless, microbiological quality may need to be considered during the process due to a slight increase in bacterial counts.

STORAGE STUDIES OF FUNCTIONAL YOGURT DRINK MADE WITH MEDIUM CHAIN TRIGLYCERIDE OIL AND ITS QUALITY ATTRIBUTES

Medium chain triglyceride oil based functional yogurt drink was prepared from skim milk with the addition of MCT at two different variations (0.5 and 1.0%) and transferred to a sterilized glass bottle with skimmed milk at (43 °C). The pH and TSS values of yogurt decreased over the storage period with a simultaneous increase in bacterial count. The sample with concentration of 1 % of MCT treated at 43 °C showed the best results compared to control samples with an acceptable microbial load. The highest lightness index was found in MY2 with 82.30 and lowest was in MY1 with 80.5 at the 1st day of the storage. At the end of the storage period (21st day), decreased lightness (L*) was observed in MY1 followed by control sample. TA was significantly increased in MYC than in MCT samples with value of 1.11±0.11% and 1.10±0.10% respectively. Acceptability index of sensory attributes of developed yogurt drink of 1 % MCT oil incorporated shows the best overall acceptability compared to other samples. Hence it is a potential replacement to the probiotic drinks with added health benefits.

Induction of bacterial cystitis in female rabbits by uropathogenic Escherichia coli and the differences between the bladder dome and trigone

ABSTRACT This study is designed to evaluate the histological effects of uropathogenic Escherichia coli (UPEC) infection in the urinary bladder of female rabbits and compare the differences between the dome and trigone. Bacterial cystitis was induced in 13 female rabbits by transurethral inoculation of UPEC into the urinary bladder. Eight animals served as controls. Urine samples were collected by catheterization and cultured for bacterial growth after 12 and 24 hours then every 48 hours. Infection was defined as ≥(1X105) colony-forming unit/ml of UPEC in the first two urine samples. Bladder dome and trigonal specimens were examined by light and scanning electron microscopy eight days after infection. There was a sustained increase in bacterial count, with urethral bleeding and rabbit weakness suggesting bladder colonization in the 10/13 study group (77%). Infection was not demonstrated in two animals and was spontaneously cleared in the third after 48 hours. No control animals developed an infection. In infected rabbits (n = 10), the dome showed inflammatory changes including the epithelial loss or thinning, inflammatory cell infiltration, and congested blood vessels compared to controls. The trigone showed a more pronounced inflammatory response than the dome. The presence of urinary bacterial growth, infection manifestations, and inflammatory changes that were more severe in the trigone than in the dome indicate successful bacterial inoculation and induction of cystitis. This animal model can be used for clinical trials on female cystitis. Our histological findings support a possible role of trigone in the pathogenesis of urinary tract infection.

Determination of exchangeable cations and residual concentration of herbicide treated soils and analysis of the in-vitro biodegradation of the herbicides

This study determined the effect of Atrazine, Xtravest, Gramoxone and Glyphosate on exchangeable cations and also analysed the in-vitro biodegradation of this herbicides as well as assayed for their residual concentration in soils. Exchangeable Na+, Ca2+, K+, Mg2+, Fe2+and Zn+ were analysed in atomic absorption spectrophotometer. Utilisation of herbicides was determined using the method of Moneke, while herbicide degradation and residual concentration of herbicide were analysed using Gas Chromatography. K+, Ca2+, Mg2+, and Na+ declined while Fe2+ and Zn+ accumulated significantly. Bacteria and fungi significantly utilised herbicides as carbon source via increases in bacterial counts, optical density, fungal counts and fungal dry weights. Herbicides were significantly degraded by bacteria and fungi. Bacteria degraded herbicides faster compared to fungi. The lowest herbicide concentration of 118.55 ppm was obtained from atrazine inoculated with bacteria, while the highest herbicide concentration of 449.23 ppm was obtained from xtravest inoculated with fungi. Residual concentration of herbicides increased significantly (P

Microbial and host-derived biomarker changes during ligature-induced and spontaneous peri-implantitis in the Beagle dog.

To evaluate microbial and host-derived biomarker changes during experimental peri-implantitis in the Beagle dog. Limited data exist on the microbial and biomarker changes during progressive bone loss as result of experimental peri-implantitis. In total, 36 implants (ndogs =6) were assessed over 3 episodes of ligature-induced peri-implantitis followed by a period of spontaneous progression. Implants with hybrid (H) and completely rough (R) surface designs were used. Clinical and radiographic parameters were recorded at 4 timepoints. Peri-implant sulcus fluid was collected from the buccal and lingual aspects of the implants. The presence of 7 bacterial species and 2 host-derived biomarkers was assessed during the study period. Total bacterial counts were significantly correlated with marginal bone loss (MBL) (r=.21; P=.009). Further, Phorphyromonas gulae (Pg) and Tannerella forsythia (Tf) were commonly correlated with MBL, suppuration (SUP) and the sulcular bleeding index scores (mSBI) (P<.05). Other bacteria were further correlated with SUP, mSBI, and MBL. While the analyzed bacteria dropped, Prevotella intermedia (Pi) further increased during the spontaneous progressive phase (P<.05). Total bacterial load did not differ significantly between H and R implants. Host-derived IL-10 was undetected along the study period. IL-1β positively correlated with probing pocket depth (r=.18; P=.03). During spontaneous progression, H implants displayed statistically significant lower levels of IL-1β (P=.003). Experimental peri-implantitis is associated with an increase in bacterial counts. While Pg and Tf are associated with ligature-induced disease progression, Pi augmented its load during the spontaneous progressive phase. IL-1β is associated with pocket probing depth and influenced by implant surface characteristics during the spontaneous progression phase.

Effect of Halal and Non-Halal Slaughtering Methods on Bacterial Contamination of Poultry Meat

This study was designed to investigate and compare the effect of halal (Islamic rules) and non-halal (non-Islamic rules) slaughtering methods on the quality characteristics of chicken. Ten village chickens weighing 0.9 - 1 kg of the same age and farm management were involved; five of them were slaughtered using the halal method, while the other five were slaughtered using the non-halal method by cutting only one side of the jugular vein and carotid artery. Bleeding time, death time, the volume of blood loss, microbial count of Standard Plate Count (SPC) and Coliform Plate Count (CPC) were determined immediately at and post-slaughtering. There was no significant difference in the microbial count of CPC between both slaughtering methods. Bleeding time, death time and SPC results for non-halal slaughtered chickens were significantly (p<0.05) higher than the halal slaughtered chickens, while the volume of blood lost was found significantly (p<0.05) lower for non-halal slaughtered chickens. These data suggested that non-halal slaughtered chickens could contain more residual blood in the meat that can lead to an increase in bacterial counts, consequently shortened shelf life.

Appraisal of Public Pipe-borne Water Quality in Jimeta/Yola Adamawa State (Nigeria): From the Treatment-plants to End-user Points

This research aimed at assessing the drinking water quality of piped water distribution in Jimeta-Yola Adamawa State, Nigeria. The strategy was based on establishing the possibilities of contaminants underlying the distribution channels compromising the quality from the treatment source to the consumer point of use. Selected heavy metals and physiological parameters were determined toward establishing the water quality indices (WQI). Though, most of the parameter determined fell below or within the permissible limits (PL) set by WHO for drinking water, the results indicated significant (p&lt;0.05) differences in the concentrations determined in the treatment plants (Yola treatment plant (YTP) and Jimeta treatment plant (JMTP)) with those at the consumer endpoints (YTPC and JMTPC). The results showed the WQI at the treatment plants being compromised due to the induction of pollutants across the distribution pipes. The water samples at the treatment point (JMTP) were excellent, having WQI &lt;25 and good quality at YTP (25&lt; WQI&lt;50). However, the water quality on leaving the treatment source was observed to slightly change to poor quality at JMTPC (WQI= 57.00), and further observed to be in moderate-good quality at YTPC (WQI=49.27). Further analysis showed an increase in bacterial counts in the water samples at the consumer points. Escherichia coli concentrations of 565 and 718 cfu /100 mL were detected in samples from YTPC and JMTPC, despite the fact the water was observed to be free from bacteria at the treatment plants.

Random packing material in disinfection contactors: Effects on final drinking water quality

AbstractThis study investigates the concern about biofilm growth on random packing material (RPM) used to enhance the hydraulic disinfection efficiency of a chlorine contactor. The inflow, outflow, and RPM were monitored for heterotrophic bacteria (via heterotrophic plate counts) and Pseudomonas aeruginosa as indicators of bacteriological water quality and the presence of biofilm. The results of this study show that there was no substantial biofilm growth in a lab‐scale chlorine contactor and no substantial increase in bacterial counts for the bulk outflow over a 10‐week period. Thus, the potential for excessive biofilm growth should not be considered a barrier concerning the use of RPM to improve the hydraulic disinfection efficiency of chlorine contactors in small drinking water treatment systems.

Use of Sonication for Enhanced Sampling of Attached Microbes from Groundwater Systems

The vast majority of microorganisms in aquifers live as biofilms on sediment surfaces, which presents significant challenges for sampling as only the suspended microbes will be sampled through normal pumping. The use of a down-well low frequency sonicator has been suggested as a method of detaching microbes from the biofilm and allowing rapid sampling of this community. We developed a portable, easy to use, low-frequency electric sonicator and evaluated its performance for a range of well depths (tested up to 42 m below ground level) and casing types. Three sonicators were characterized in laboratory experiments using a 1m long tank filled with pea gravel. These included a commercially available pneumatic sonicator, a rotating flexible shaft sonicator, and the prototype electric sonicator. The electric sonicator detached between 56 and 74% of microbes grown on gravel-containing biobags at distances ranging between 2 and 50 cm from the sonicator. The field testing comprises of a total of 55 sampling events from 48 wells located in 4 regions throughout New Zealand. Pre- and post-sonication samples showed an average 33 times increase in bacterial counts. Microbial sequence data showed that the same classes are present in pre- and post-sonicated samples and only slight differences were seen in the proportions present. The sampling process was rapid and the significant increases in bacterial counts mean that microbial samples can be quickly obtained from wells, which permits more detailed analysis than previously possible.