Non-permanent primary food packaging materials assessment: Identification, migration, toxicity, and consumption of substances.

Almost all processed food comes packaged in either plastic, glass, metal, or paper and paperboard materials, and many packaging materials are disposed of after a single use (linear economy). Based on the concept of a circular economy, the recycling of food packaging materials has become one of the main targets for industries and regulators around the world. However, recycling presents particular challenges, mainly related to the recycled material composition, which determines its reusability, application, functionality, and chemical safety. In this latter matter, it has been demonstrated that the use of recycled food packaging materials increases the number and possible sources of substances that could be present in the packaging material, which is of concern as substances that can migrate into food and cause health hazards upon consumption. This review compiles information regarding substances detected in non-permanent food packaging materials, focusing mainly on plastics, paper, and paperboards. The compilation of literature studies (110 research articles) on the presence of intentionally added substances (IAS) and non-intentionally added substances (NIAS) in food packaging materials, their migration, toxicity, and dietary exposure has been summarized, evaluated, and discussed. In addition, current sustainable food packaging trends have been mentioned. Finally, approaches to reduce the presence, migration, and potential exposure to substances that have migrated from packaging materials into food have been reviewed.

Bacterial survival and adhesion for formulating new oral probiotic foods.

Probiotics are defined as live microorganisms, which, when administered in adequate amounts, confer health benefits to the host. Traditionally, probiotic food research has heavily focused on the genera Bifidobacteria and Lactobacilli, along with their benefits for gut health. Recently with the identification of new probiotic strains specifically intended for oral health applications, the development of probiotic foods for oral health benefits has garnered interest, with a renewed focus on identifying new food formats for delivering probiotics. The development of novel oral probiotic foods is highly complex, as the composition of a food matrix dictates: (1) bacterial viability during production and shelf life and (2) how bacteria partition with components within a food matrix and subsequently adhere to oral cavity surfaces. At present, virtually no information is available on oral probiotic strains such as Streptococcus salivarius; specifically, how orally-derived strains survive under different food parameters. Furthermore, limited information exists on the partition behavior of probiotics with food components, governed by physico-chemical interactions and adhesion phenomena. This review aspires to examine this framework by providing a foundation with existing literature related to the common probiotic genera, in order to inform and drive future attempts of designing new oral probiotic food formats.

Comparison of four extraction methods for analysis of volatile hop-derived aroma compounds in beer.

The volatile organic compound profile in beer is derived from hops, malt, yeast, and interactions between the ingredients, making it very diverse and complex. Due to the range and diversity of the volatile organic compounds present, the choice of the extraction method is extremely important for optimal sensitivity and selectivity. This study compared four extraction methods for hop-derived compounds in beer late hopped with Nelson Sauvin. Extraction capacity and variation were compared for headspace solid-phase micro extraction, stir bar sorptive extraction, headspace sorptive extraction, and solvent-assisted flavor evaporation. Generally, stir bar sorptive extraction was better suited for acids, headspace sorptive extraction for esters and aldehydes, while headspace solid-phase microextraction was less sensitive overall, extracting 40% fewer compounds. Solvent-assisted flavor evaporation with dichloromethane was not suitable for the extraction of hop-derived volatile organic compounds in beer, as the profile was strongly skewed towards alcohols and acids. Overall, headspace sorptive extraction is found to be best suited, closely followed by stir bar sorptive extraction.

Comparing PTR-MS profile of milk inoculated with pure or mixed cultures of spoilage bacteria.

The volatile organic compounds (VOCs) associated with UHT milk (n=8) inoculated with either pure inoculums of Pseudomonas fluorescens (two strains tested) or Chryseobacterium sp., or with mixed cultures of 2 or all 3 of the bacterial strains, and held at 4.5 °C for up to 26 days was measured using proton transfer reaction - mass spectrometry (PTR-MS). The VOCs evolved included a range of carbonyl compounds, alcohols, esters, and acids and had significant qualitative and quantitative differences between the inoculums. Milks inoculated with paired (mixed) bacterial cultures attained patterns similar to the VOC composition of one of the pure inoculums, which could be attributed to the domination of these bacteria within the mixed inoculum. This study will help to characterize the spoilage of milk and provide important insights into understanding the factors that limit the shelf life of milk.

Yeast Strain Influences the Hop-Derived Sensory Properties and Volatile Composition of Beer.

The perception of hop-derived flavour in beer is not well understood, particularly regarding the effect that different yeast strains and fermentation parameters have on perceived hop aroma and the mechanisms responsible for these changes. To evaluate the influence of yeast strain on the sensory properties and volatile composition of beer, a standard wort, late-hopped with New Zealand Motueka hops (5 g·L-1), was fermented with one of twelve yeast strains under constant conditions (temperature and yeast inoculation rate). The bottled beers were evaluated using a free sorting sensory methodology, and their volatile organic compounds (VOC) were assessed using gas chromatography mass spectrometry (GC/MS) with headspace solid-phase microextraction (SPME) sampling. Beer fermented with SafLager W-34/70 yeast was associated with a hoppy flavour attribute, whereas WY1272 and OTA79 beers were sulfury, and WY1272 was also metallic. WB06 and WLP730 beers were perceived to be spicy, with WB06 beer also perceived as estery, whereas VIN13 beer was sour, and the WLP001 beer was astringent. Beers fermented using the twelve yeast strains had clearly distinct VOC profiles. Beer made with WLP730, OTA29, SPH, and WB06 yeasts had the highest 4-vinylguaiacol levels, which contributed to their spicy attribute. Beer made with W3470 had high levels of nerol, geraniol, and citronellol, which supported its sensory characterisation as being 'hoppy'. This research has illustrated the important role that yeast strain has on modulating hop flavour in beer.

The physico-chemical characterization of casein-modified surfaces and their influence on the adhesion of spores from a Geobacillus species.

To gain a better understanding of the factors influencing spore adhesion in dairy manufacturing plants, casein-modified glass surfaces were prepared and characterized and their effect on the adhesion kinetics of spores from a Geobacillus sp., isolated from a dairy manufacturing plant (DMP) was assessed using a flow chamber. Surfaces were produced by initially silanizing glass using (3-glycidyloxypropyl) trimethoxysilane (GPS) or (3-aminopropyl) triethoxysilane to form epoxy-functionalized (G-GPS) or amino-functionalized glass (G-NH(2)) substrata. Casein was grafted to the G-GPS directly by its primary amino groups (G-GPS-casein) or to G-NH(2) by employing glutaraldehyde as a linking agent (G-NH(2)-glutar-casein). The surfaces were characterised using streaming potential measurements, contact angle goniometry, infrared spectroscopy and scanning electron microscopy. The attachment rate of spores suspended in 0.1 M KCl at pH 6.8, was highest on the positively charged (+14 mV) G-NH(2) surface (333 spores cm(-2) s(-1)) compared to the negatively charged glass (-22 mV), G-GPS (-20 mV) or G-GPS-casein (-21 mV) surfaces (162, 17 or 6 spores cm(-2) s(-1) respectively). Whilst there was a clear decrease in attachment rate to negatively charged casein-modified surfaces compared to the positively charged amine surface, there was no clear relationship between surface hydrophobicity and spore attachment rate.

Biogenic amines and potential histamine - Forming bacteria in Rihaakuru (a cooked fish paste).

The biogenic amine concentration in Rihaakuru (a fish paste) (n=28), obtained from different parts of the Maldives (North, South, and Central), was determined by HPLC. Ten biogenic amines were detected; agmatine, not detected (ND) - 161ppm; cadaverine, ND - 387ppm; histamine, ND - 5487ppm; putrescine, ND - 290ppm; phenylethylamine, ND - 23ppm; serotonin, ND - 91ppm; spermine, ND - 329ppm; spermidine, ND - 79ppm; tryptamine, ND - <5ppm; and tyramine, ND - 50ppm. Nine biogenic amines were found in 3 samples, 8 in 10 samples, 7 in 6 samples, 6 in 3 samples, 4 in 5 samples, and 1 was found in 1 sample. Histamine was detected at levels that are regarded as a risk to human health. Fourteen isolates were selected from two randomly selected samples out of the 28 samples of Rihaakuru and screened for histamine production. Twelve of the 14 isolates produced histamine, with the highest histamine producers being Bacillus massiliensis Nai5 (6.65ppm) and Bacillus polyfermenticus (5.58ppm); while Bacillus malacitensis produced the least (<0.5ppm).

Chemistry and microbiology of traditional Rihaakuru (fish paste) from the Maldives.

Rihaakuru is a traditional Maldivian side dish consumed mainly with rice. It is a thick brown fish paste, made from tuna after prolonged heating. Samples tested were found to have a low water activity (0.55-0.8), slightly acidic pH (5.62-6.18) and moderate salt content (1.4-1.6%). The product was found to be rich in polyunsaturated fatty acids such as omega-3, had high protein content (56-59%) and an energy level of 13.8 kJ/g. The product had a low microbial count (1.54-2.31 log(10) cfu/g). The bacteria isolated belonged to the Bacillaceae (Genus Clostridium, and Bacillus), Streptococcaceae (Genus Streptococcus), Micrococcaceae (Genus Staphylococcus), and Corynebacterium. The product appears to be a nutritious and shelf-stable product.

Salt modulates bacterial hydrophobicity and charge properties influencing adhesion of Pseudomonas aeruginosa (PA01) in aqueous suspensions.

The influence on cell hydrophobicity of differential extension with ionic strength of lipopolysaccharide molecules (LPS), which exist as charged and uncharged polymers at the surface of the gram-negative bacterium Pseudomonas aeruginosa (PA01), has been investigated. Attenuated total reflection infrared (ATR-IR) spectral absorptions from a single layer of cells adsorbed to ZnSe increased in intensity with increasing NaCl concentration up to 0.1 mol L(-1). Dynamic contact angle measurements (Wilhelmy plate tensiometry) made with a ZnSe plate having an adsorbed cell layer and the adherence of the cells to hexadecane suggest that PA01 cells were most hydrophobic in contact with 0.1 mol L(-1) NaCl solutions. These data indicate a charge screening induced compression of the charged LPS polymers decreasing the cell-surface approach distance and increasing the cell hydrophobicity due to the greater surface predominance of the uncharged LPS polymers. Interestingly, adsorbed cell layers in 0.3 mol L(-1) NaCl had a lower IR absorption intensity, and PA01 cells suspended in 0.3 mol L(-1) were found to be more hydrophilic, indicating that other factors influence the cell-surface approach distance and hydrophobicity. The examination of cell electrophoretic mobility variation with NaCl concentration suggests that the compression of charged polysaccharides increases the polysaccharide charge density and may also reduce the flow of liquid through the polysaccharide layer affecting the effective potential at the interface, the cell hydrophobicity, and the cell-surface approach distance.

Effect of cold storage and different ions on the thermal resistance of B. cereus NZAS01 spores- analysis of differential gene expression and ion exchange.

Bacillus cereus spores in food are able to survive pasteurization, and if conditions are favourable, subsequently germinate, grow and produce toxins causing food poisoning. The objectives of this study were to firstly determine the impact of cold storage and ion uptake on the thermal resistance of B. cereus spores and secondly to use differential gene expression to help elucidate possible molecular mechanisms for the changes detected in their thermal resistance. B. cereus spores were held at 4 °C in either 0.05 or 0.5 M solutions of cations (Na+, Ca2+ Mg2+,K+, Zn2+) for 6 days and their D88-values were estimated. In the presence of sodium chloride (0.05 and 0.5 M), sodium phosphate buffer, (pH 7, 0.05 and 0.5 M) or zinc acetate (0.05 M), D88 values decreased by 8.8, 10.9, 11.2, 12.9, and 10.2 min respectively, with no evidence of germination (plating methods). Exposure of spores to Na+ in sodium phosphate buffer (pH 7, 0.05 and 0.5 M) or sodium chloride (0.05 and 0.5 M) resulted in the accumulation of Na+ (66.0 ±â€¯2.9, 193.1 ±â€¯4.6, 136.2 ±â€¯9.9 and 70.5 ±â€¯2.7 µg/g) by spores at the significant expense of K+ (10.8 ±â€¯0.5, 7.5 ±â€¯0.2, 8.1 ±â€¯0.4 and 3.6 ±â€¯0.4 µg/g respectively). The mechanism behind the loss of resistance in sodium phosphate buffer (0.05 M) was further investigated by monitoring the differential gene expression using mRNA sequencing. Genes encoding for uracil permease (BC_3890), Mg2+ P-type ATPase-like protein (BC_1581), ABC transporter ATP-binding protein (BC_0815), and 2-keto-3-deoxygluconate permease (BC_4841) were significantly (FDR value ≤0.05) upregulated. This upregulation indicated a possible increase in permeability, which is suggested to account for the increased uptake of sodium ions and the reduction measured in the spore's thermal resistance. This data suggests that during storage at 4 °C in the presence of sodium ions, spores should not be considered to be completely dormant.

Differential gene expression for investigation of the effect of germinants and heat activation to induce germination in Bacillus cereus spores.

Differential gene expression was used to explore the mechanisms underpinning the differences in the impact of heat activation (70 °C for 30 min) on the germination of Bacillus cereus spores in the presence and absence of a germinant (L-alanine). The number of germinated cells, after heat activation plus L-alanine (3.5 ±â€¯0.02 log CFU/ml) in the spore only initial population was found to be higher than that in only heat activated spores (2.01 ±â€¯0.02 log CFU/ml). The concentration of DPA released by heat activated spores in the presence of L-alanine was 68.3 ±â€¯0.1 and 112.1 ±â€¯0.02 µg/ml after 30 and 60 min, compared to 96.5 and 166.2 ±â€¯0.01 µg/ml after 30 and 90 min, respectively released by spores subjected only to heat activation. Gene (BC0784) encoding for the spore germination protein, gerA operon was up-regulated with a log2-transformed fold change value of 1.2 due to heat activation in the presence of L-alanine. The GerA operon located in the inner membrane is known to be involved in the uptake of L-alanine by B. cereus and has been reported to be involved in L-alanine mediated germination. In addition the up-regulation of genes involved in the uptake of L-alanine is proposed to provide the answer to the synergistic effect of heat and L-alanine in inducing germination in B. cereus spores. In short, heat activation increases the ability of L-alanine to penetrate into the spore's inner membrane, where it can be recognized by the receptors for initiation of the germination pathway. In the current study, the majority of the ribosomal proteins were down-regulated (when spores were heat treated in presence of germinants) this process also appeared to slow down protein synthesis by restricting the protein translation machinery. Differential gene expression revealed the genes responsible for the pathways related to transport and recognition of L-alanine into the spore that could have led to the accelerated germination process along with partial shutting down of protein synthesis pathway and ABC transporters. Knowledge of gene regulation in spores during heat activation will help in the development of approaches to prevent spore germination, which could provide an additional safeguard against bacterial growth and toxin production in improperly cooled heat treated foods.

Impact of temperature, nutrients, pH and cold storage on the germination, growth and resistance of Bacillus cereus spores in egg white.

B. cereus spores are a concern to the food industry, especially to the producers of heat sensitive food products like egg white or precooked and stored food such as fried rice. This study investigated the impact of nutrients, temperature (4, 8, 15 and 25 °C), pH (4, 5, 7 and 9), and cold storage on the germination, growth and resistance of B. cereus spores. In egg white held at 4 °C for 12 days spore germination was not apparent, however the addition of egg yolk (5%) resulted in a 2 Log colony forming units (CFU)/mL increase in vegetative cells (p < .05). Adding l-alanine (0.9 mg/mL) to egg white did not induce germination unless the spores were simultaneously heat activated at 70 °C for 30 min. On incubation at 15 or 25 °C in egg white, spore germination increased by 3.0 Log and 3.7 Log CFU/mL on day 12. The presence of 5% yolk further enhanced germination and subsequent sporulation during storage at 15 and 25 °C. Acidification (pH 4) of 10% egg white solution prevented germination at 4, 8, 15 and 25 °C. Spores held at 4 °C for 6 days in phosphate buffer (50 mM, pH 4) had visible deformations on their surface (scanning electron microscopy) and a significant reduction in D88, and D92 values of 13.9 and 8.2 min respectively. A better understanding of how spores sense and respond to changing environmental conditions will help in the development of processing strategies, involving multiple hurdles to ensure the prevention of germination and subsequent toxin production.

Development of a novel sample reuse approach to measure the impact of lean meat, bone and adipose tissue on the development of volatiles in vacuum-packed chilled lamb stored at 2 °C for 15 days.

The impact of different ratios of lean meat, adipose tissue (fat) and bone on the volatile organic compound (VOC) profile of vacuum-packed (VP) lamb stored at 2 °C for up to 15 days was investigated using two sampling approaches. VOC development in individual samples was followed over time using either a traditional sampling regime where replicate samples were sampled (single-use) at a given time or a novel approach where replicate samples were resampled (reuse) over time. VOCs present in the headspace of the packaged samples were detected using proton-transfer-reaction mass spectrometry (PTR-MS) with complementary solid phase micro-extraction gas chromatography-mass spectrometry (SPME-GC-MS) analysis on a subset of samples. Bacteria numbers were determined using standard microbiological methods. Meat packaged with 20% added adipose tissue contained slightly higher numbers of bacteria at the start of the trial with correspondingly higher VOC levels compared to lean meat alone. Storage time (as a proxy for microbial numbers) was the main driver for VOC production. Differences between the reuse and the single-use sample sets were minimal, suggesting that resampling of VP lamb samples may be a useful approach to study the development of low frequency spoilage patterns over time.

Adhesive secretions of live mussels observed in situ by attenuated total reflection-infrared spectroscopy.

The chemical species involved in the adhesion of blue mussels (Mytilus galloprovincialis) and greenshell mussels (Perna canaliculus) to surfaces has been investigated using in situ attenuated total reflection infrared (ATR-IR) spectroscopy. Mussel spat ranging in size from 0.5 to 25 mm were placed in a flow cell containing a ZnSe multiple internal reflection prism and supplied with temperature-controlled seawater. Distinctively different absorption spectra were obtained when the mussels were predominantly moving across the surface or forming permanent bonds. With limited movement, the absorption spectrum was characteristic of protein with peaks near 1647 cm-1 (amide I), 1543 cm-1 (amide II), and 1235 cm-1 (amide III). When the mussels were observed to be moving across the surface of the ATR-IR crystal there was a strong broad absorption maximum around 1200-900 cm-1 (carbohydrate polymers), presumably due to the secretion of a weakly acidic mucopolysaccharide. Distinct differences in the spectra obtained from the adhesive secretions of blue or greenshell mussels were not observed. The data presented is the first reported use of IR spectroscopy to obtain in situ, real-time, chemical data on the interactions between invertebrates and substrates immersed in sea water.

Investigating the in-vitro and in-vivo flavour release from 21 fresh-cut apples.

In-vitro and in-vivo flavour release from 21 different apple cultivars was studied using proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) with a focus on the relationship between texture and volatile organic compound (VOC) emission. Generally, firm-juicy cultivars had a shorter time to first swallow (Tswal) and a higher number of swallows (Nswal), while softer-mealy cultivars had a longer Tswal and a lower Nswal. Firm-juicy cultivars containing high VOC concentrations had a short time to maximum intensity (Tmax) owing to a shorter Tswal and a higher Nswal as juice was released during mastication. Swallowing increased VOC flow through the nasal cavity. These results differ from previous flavour release studies with gel/gel-like model systems as juiciness/release of fluids is not a factor in such matrices. The current study, therefore, highlights the benefits of using in-vivo analysis to gain a better understanding of flavour release in real food products.

Development of a laboratory scale clean-in-place system to test the effectiveness of "natural" antimicrobials against dairy biofilms.

A laboratory scale system, partially reproducing dairy plant conditions, was developed to quantify the effectiveness of chlorine and alternative sanitizers in reducing the number of viable bacteria attached to stainless steel surfaces. Stainless steel tubes fouled in a continuous flow reactor were exposed to a standard clean-in-place regime (water rinse, 1% sodium hydroxide at 70 degrees C for 10 min, water rinse, 0.8% nitric acid at 70 degrees C for 10 min, water rinse) followed by exposure to either chlorine (200 ppm) or combinations of nisin (500 ppm), lauricidin (100 ppm), and the lactoperoxidase system (LPS) (200 ppm) for 10 min or 2, 4, 8, 18, or 24 h. There was significant variation in the effectiveness of the alkaline-acid wash steps in reducing cell numbers (log reduction between 0 and 2). Following a 10-min treatment, none of the sanitizers significantly reduced the number of attached cells. Two hours of exposure to chlorine, nisin + the LPS, or lauricidin + the LPS achieved 2.8, 2.2, and 1.6 log reductions, respectively. Exposure times > 2 h did not further decrease the number of viable bacteria attached to the stainless steel. The effectiveness of combinations of nisin, lauricidin, and the LPS was similar to that of chlorine (P > 0.05), and these sanitizers could be used to decontaminate the surfaces of small-volume or critical hard-to-clean milk processing equipment.

A novel method for the reduction of numbers of Listeria monocytogenes cells by freezing in combination with an essential oil in bacteriological media.

The use of multiple freeze (-20 degrees C)-thaw cycles in combination with isoeugenol and polysorbate 80 was investigated as a method for the reduction of numbers of Listeria monocytogenes cells in a bacteriological medium. Three freeze (1 h, -20 degrees C)-thaw cycles in the presence of isoeugenol at concentrations of 0, 100, and 300 ppm resulted in average L. monocytogenes reductions of 0.69, 2.65, and 3.3 log10 MPN (most probable number) per ml, respectively. Increasing the number of freeze-thaw cycles further decreased cell numbers, with reductions of nearly 5 log10 MPN/ml being obtained with six freeze-thaw cycles. Freeze-thaw cycles were effective in reducing cell numbers at isoeugenol concentrations down to 25 ppm. Rapid freezing rates with liquid nitrogen were found to be less effective in reducing numbers of L. monocytogenes cells. Two rapid freeze-thaw cycles in the presence of 100 ppm isoeugenol and polysorbate 80 resulted in a reduction of 1.45 log10 MPN/ml. Two freezing (-20 degrees C) cycles involving slow freezing and thawing rates with samples being held frozen for 6 h for each cycle resulted in reductions larger than those obtained with faster freezing rates. It was found that complete thawing in freeze-thaw cycles was not necessary to achieve bactericidal action. The application of multiple freeze-thaw cycles in combination with low concentrations of isoeugenol could effectively reduce numbers of L. monocytogenes cells in bacteriological media.

Monitoring photooxidation-induced dynamic changes in the volatile composition of extended shelf life bovine milk by PTR-MS.

Exposure of milk to light leads to photooxidation and the development of off-flavours. To follow these reactions, semi-skimmed (1.5% fat) and whole (3.8% fat) extended shelf life (ESL) bovine milk samples were exposed to fluorescent light for up to 20 h at room temperature, and the volatiles in the samples' headspace were measured in real time using proton-transfer-reaction mass spectrometry (PTR-MS). Compounds tentatively identified as methanethiol, acetone/propanal, pentanal/octanal/nonanal/1-octen-3-ol, hexanal, diacetyl, dimethyl disulphide, heptanal and benzaldehyde displayed dynamic release profiles relating to the changes occurring in milk upon exposure to light.

X-ray micro-computer tomographic method to visualize the microstructure of different apple cultivars.

Apples are appreciated for their texture with firmness acting as an indicator of quality. During prolonged storage, apples can soften and their texture can become undesirably mealy. Using an X-ray microcomputer tomography (µ-CT) scanner, the porosity (ratio of intercellular space [IS] to total volume) and the structural arrangement of the parenchyma tissue of 4 apple cultivars (Braeburn, Fuji, Golden Delicious, Jazz) stored under similar conditions for 100 d were visualized via the development of 2D and 3D images. The texture of the apples was also measured using a puncture test. The morphometric and textural measurements revealed that firm Jazz apples (flesh firmness: 29.84N) had a lower porosity (17%) compared to soft Golden Delicious apples (flesh firmness: 14.16N; porosity: 29.8%). In general, firm apples had a higher dry matter (%) and a lower porosity (%), while the reverse was true for softer apples. However, this was not an absolute trend as cultivar specific differences in the microstructural organization and consequent mechanical strength of the parenchyma tissue also influenced firmness. For example, although Fuji apples were firm (28.42N), they had a high porosity (29.3%) due to the presence of numerous small and compact IS. In comparison, soft Golden Delicious apples had a high porosity (29.8%) due to the presence of large, interconnected IS. Imaging technologies have the potential to provide a pictorial or graphical database showing the size range distribution of IS corresponding to different parenchyma tissue types and how they relate to apple texture and eating quality.

Antibiotic susceptibility of Moraxella catarrhalis biofilms in a continuous flow model.

Antibiotic susceptibility of Moraxella catarrhalis biofilms was assessed using a Sorbarod filter continuous flow model. Ceftriaxone, erythromycin, amoxicillin, and Augmentin produced significant decreases in both biofilm and planktonic viable cell populations collected from the effluent. Augmentin produced the greatest reduction in biofilm (2.5 orders of magnitude) and planktonic populations (4 orders of magnitude). However, the minimum biofilm eradication concentration was not reached within the concentration range tested (4-64 mg/L), despite demonstrable susceptibility in standard microdilution tests (minimum bactericidal concentrations [MBC] ≤0.06 mg/L). Antibiotic tolerance of M. catarrhalis biofilm populations was partly due to an inoculum effect and partly inherent. Amoxicillin had no effect against a ß-lactamase-producing M. catarrhalis. Compared to batch-grown cells, planktonic cells recovered from the Sorbarod filter effluent were more resistant to the antibiotics tested (MBC ≤0.06 and >64 mg/L, respectively). Overall, the findings may explain the lack of response of some M. catarrhalis infections to antimicrobial therapy.