Glycerol Broth Research Articles

Evaluation and Molecular Characterization of Colistin-Resistant Isolates of Pseudomonas aeruginosa and Klebsiella pneumoniae from the Infected Wounds of Hospitalized Patients.

This study was planned to determine the colistin-resistant (CR) gene distribution among two species of gram-negative bacteria, Pseudomonas aeruginosa and Klebsiella pneumoniae. In total, 50 isolates of K. pneumoniae (14 isolates, 28%) and P. aeruginosa (36 isolates, 72%) were isolated between August 2023 and October 2023 from clinical wound samples at Jinnah Hospital and Lahore General Hospital Lahore, Pakistan. To determine the resistance genes linked to CR and assess antimicrobial susceptibility, all isolates were kept at -80°C in 15% glycerol broth. Using the right primer sets, a polymerase chain reaction (PCR) was utilized to identify the CR-associated mcr-1 gene of the gramnegative isolates. Out of 50, 40 isolates (80%) showed resistance against colistin with MICs of 8 and 128 μg/ml. The majority (97%) of P. aeruginosa CR strains were considered multidrug resistant (MDR). All K. pneumoniae isolates were resistant to cefepime, cotrimoxazole, ceftriaxone, and imipenem. The clinical CR isolates of P. aeruginosa were highly resistant to ceftriaxone, imipenem, cefepime, cotrimoxazole, ciprofloxacin, amikacin, and piperacillin/tazobactum. The antibiotic resistance pattern was terrifyingly high among both bacterial species. According to the PCR results, CR was prevalent among the gram-negative samples, and the mcr-1 gene was positive in 6/40 (15%) of the CR isolates, including four P. aeruginosa and two K. pneumoniae strains. The high CR (80%) reported in this research is cause for concern and underscores an urgent need to use colistin in a limited and logical manner, similar to other antibiotics.

Highly efficient fermentation of glycerol and 1,3-propanediol using a novel starch as feedstock

As a potential cost-effective feedstock for highly efficient fermentation of glycerol and its downstream product 1,3-propanediol (1,3-PD), duckweed starch was characterized and used for glycerol fermentation, for the first time, in this study. Genes involved in glycerol biosynthesis (gpd1 and gpp2) were overexpressed in Escherichia coli, and genes involved in glycerol catabolism (glpK and gldA) were disrupted, which led to significantly decreased residual sugar levels and dramatically increased glycerol production. The maximum glycerol concentration in fed-batch fermentation reached 102.72 g L-1 at 28 h, and the glycerol productivity was 3.67 g L-1 h-1, which, to our knowledge, is the highest productivity thus far reported. Subsequently, glycerol broth was fermented into 1,3-PD by Klebsiella pneumoniae. The concentration, conversion rate and productivity of 1,3-PD reached 35.54 g L-1, 40.28% and 0.89 g L-1 h-1, respectively, without optimization. In summary, the duckweed starch-to-glycerol-to-1,3-PD process is feasible and shows potential for improving glycerol industry competitiveness.

Efficacy of Peptone Glycerol Broth in Long-term Storage of the Bacterial and Yeast Cultures

Introduction: Bacterial isolates and control strains stocking is an integral part of clinical microbiology laboratories. This is an essential step in maintaining quality. Preserving the strains without altering the character is an essentiality. There are different stock culture preparations studied in past showing varied level of performance. Aim: To evaluate the performance in terms of longevity and phenotypic character preservation of Peptone Glycerol Broth (PGB) in comparison to Brucella Glycerol Broth (BGB) and Skim Milk (SKM). Materials and Methods: The present study was a prospective analytical study. Three quality control strains and seven clinical isolates with different types of resistance were stocked in triplicates with cryobead based peptone broth with 15% glycerol, Brucella Broth (BB) with 15% glycerol and 10% SKM and stored at -80°C. Isolates were revived in monthly pattern, quarterly pattern and once after 10 months to assess the variations in viability and loss of phenotypic properties arising out of repeated freeze thaw and contaminations. Viability was assessed by time taken to produce observable confluent growth on revival. Metabolic characters and antibiotic susceptibility testing were compared before and after stock revival at intervals. Results: The phenotypic characters like metabolic features and antibiotic susceptibility were preserved with all three preparations both with repeated freeze thaw and single freeze thaw at the end of 10 months. PGB and BGB had a 100% revival rate of stored isolates with a confluent growth at 24 hours in comparison to 93.56% with SKM. Conclusion: Cryobead preparation of peptone broth-15% glycerol can be used as an effective preparation for stock culture maintenance of non-fastidious bacteria and yeast.

Response surface optimization of prodigiosin production by mutagen-treated Serratia marcescens in different growth media

Background: Prodigiosin is a bioactive bacterial pigment produced by Serratia marcescens and possesses anticancer, antibiotic, antifungal, antibacterial, and immunosuppressive activities without any toxic effects on human cells. Objectives: The study was planned to optimize the effect of ultravoilet (UV) light and acridine orange (AO), as mutagens and incubation time on prodigiosin production by S. marcescens in nutrient agar broth and peptone glycerol broth. Materials and Methods: The optimization was done by constructuing a quadratic polynomial response surface model using a bifactorial central composite design. The S. marcescens starian was treated with UV light (0, 30, 60, 90, and 120 s) and various concentrations of AO (0, 50, 100, 150, and 200 μg/mL) and incubated in the selected growth media for different times (0, 15, 30, 45, and 60 h). The prodigiosin production was measured in terms of change in pH and optical density (OD) of the ethanolic extracts of culture media. Results: The prodigiosin production was found to be a significant linear and quadratic function of incubation time in both of the culture media. However, a statistically non-significant increased prodigiosin production, in terms of pH and OD of the extracts, was observed under the influence of both mutagens. The optimum values of incubation time to achieve optimal production of prodigiosin from UV light-exposed and AO-treated cultures were found to be in the range of 37–60 h, respectively. Conclusion: The pigment production was increased significantly with an increase in the incubation time. The study provides the optimum conditions for the production of prodigiosin in research and commercial field.

Molecular Characterisation of Carbapenem-Resistant Enterobacteriaceae from Intensive Care Units.

To determine the molecular characterisation of carbapenem-resistant enterobacteriaceae (CRE) from patients admitted in intensive care units (ICUs) of a tertiary care hospital. Descriptive study. Department of Pathology and Microbiology, Pakistan Institute of Medical Sciences (PIMS), SZABMU, Islamabad, Pakistan, from July 2015 to March 2016. Fifty isolates of CRE from intensive care units samples were processed, collected through samples coming from ICUs. Specimens were cultured on blood and Mac Conkey agar, and organisms were identified. Resistant organisms to imipenem and meropenem were preserved in glycerol broth at -80oC. Their molecular characterisation was done using the conventional PCR targeting NDM, KPC, VIM and IMP genes. Out of 50 samples, 13 (26%) were from urine, 13 (26%) from endotracheal tube tip, 7 (14%) from blood, 7 (14%) from pus, 7 (14%) from tracheal secretions, 2 (4%) from fluids, and 1 (2%) from catheter tip. NDM genes was isolated in 56% isolates. VIM, KPC, and IMP genes were not found in any isolates. NDM positive isolates included 86% Klebsiella pneumonia, 10% Escherichia coli, and 4% Klebsiella oxytoca. NDM gene was present in 28 (56%) samples. Whereas, VIM gene, KPC gene, and IMP genes were not detected in the CRE samples.

Using prodigiosin against some gram-positive and gram-negative bacteria and Trypanosoma cruzi.

Background:This work aimed to explore the action of natural prodigiosin on both bacterial organisms and Trypanosoma cruzi cells.Methods:Natural prodigiosin pigment was extracted and purified from cultures of Serratia marcescens. Two media, peanut broth and peptone glycerol broth, both recommended in the literature for prodigiosin production, were compared. The prodigiosin obtained was employed to explore its antimicrobial properties against both bacteria and Trypanosoma cruzi cells. Results:Peanut broth yielded four times more prodigiosin. The prodigiosin showed remarkable activity (minimal inhibitory concentrations in the range of 2-8 µM for bacteria and half maximal inhibitory concentration of 0.6 µM for Trypanosoma cruzi). In fact, the prodigiosin concentration required to inhibit parasite growth was as low as 0.25 mg/l versus 4.9 mg/l of benznidazole required. Furthermore, atomic force microscopy revealed marked morphological alterations in treated epimastigote forms, although no pore-formation activity was detected in protein-free environments. Conclusions:This work demonstrates the potential usefulness of prodigiosin against some gram-positive and gram-negative bacteria and Trypanosoma cruzi although further studies must be done in order to assess its value as a candidate molecule.

Effect of Cell Lysis (CLs) Products on Acidophilic Chemolithotrophic Microorganisms and the Role of Acidocella Species

ABSTRACTAcidophilic chemolithotrophic microorganisms (CMs) are widely used for bioleaching of mineral resources. However, the growth of bacteria and their leaching activity are often inhibited (restricted) by organic components, e.g. lysates and exudates. The aims of this study were to examine the extent of cell lysis (CLs) inhibition on acidophilic microorganisms and to identify microorganisms that can utilize CLs products and eliminate their inhibition effect on acidophilic microorganisms. Specifically, it was revealed that Acidithiobacillus caldus was severely inhibited at 5% CLs products, whereas A. ferrooxidans and Leptospirillum ferriphilum are severely inhibited at 20%. It has been found that strains RBA and RBB of heterotrophic bacteria, isolated from anaerobic sludge, can biodegrade CLs products and when co-cultured with A. ferrooxidans, they can alleviate the toxic effect of CLs products under low pH (2–3). It has been shown that besides CLs, isolated strains can grow on glucose, glycerol, yeast extract, citric acid, and tryptone soya broth with an optimum temperature of 35°C and a pH of 3. The strains showed the ability to reduce ferric ions to ferrous ions when glycerol was used as a substrate after 2 days under both aerobic and anaerobic conditions. On the basis of morphophysiological and molecular biological studies, the isolated strains RBA and RBB were identified as Acidocella spp.

Different Preservation Methods for Long Term Maintenance of <i>Haemophilus influenzae</i>

Haemophilus species are Gram-negative coccobacilli that require factor X and factor V for growth. Beyond this, it is a finicky bacterium to culture, and any modification of culture procedures greatly reduces isolation rates. Poor quality of laboratories in developing countries results in its poor isolation rates. This study was done with the objective of finding out the optimal cultural environment and media so that it could be maintained for a longer period in economical settings like ours which was done using H. influenzae ATCC 49,766. In this study, several culture media were tested as a means to preserve H. influenzae ATCC like TSB + glycerol + sheep blood, BHI broth, BHI broth + glycerol, BHI broth+ glycerol + sheep blood, Chocolate agar slant and satellitism plate. Three sets of respective media were inoculated with 18 - 24 hours growth of H. influenzae. They were incubated at 37 oC 48 hours in a candle extinction jar. The media were checked for growth by subculturing them on chocolate agar plates and identified by biochemical reactions. Each set was maintained at 2 oC - 8 oC, -20 oC and at room temperature and checked for the viability 24 hourly by subculturing them on chocolate agar. Results showed best growth of H. influenza on chocolate agar slants for 15 - 20 days, followed by BHI + glycerol + sheep blood broth and satellitism plate for 4 - 6 days followed by BHI broth for 2 - 4 days. There was no growth in TSB + glycerol + sheep blood broth and BHI + glycerol broth media. Present study showed similar results as done by NS Srikanth et al. 2003 with growth on chocolate agar & satellitism plate for 3 - 5 days but no growth in TSB + Glycerol + Sheep blood broth media. Chocolate agar slant is by far the most long term preserving media for H. influenzae. However, growth on BHI broth with various modifications is also showed a good preservation for 3 - 5 days, so with further experiments we can hope to maintain the organism in these media also.

Density Distribution of Pharyngeal Carriage of Meningococcus in Healthy Young Adults: New Approaches to Studying the Epidemiology of Colonization and Vaccine Indirect Effects.

Improved understanding of Neisseria meningitidis (Nm) carriage biology and better methods for detection and quantification would facilitate studies of potential impact of new vaccines on colonization and transmission in adolescents. We performed plate cultures on 107 oropharyngeal swabs stored frozen in skim milk tryptone glucose glycerol (STGG) broth and previously positive for Nm. We compared quantitative polymerase chain reaction (qPCR) detection of Nm in 601 STGG-swabs with culture. Using qPCR (n = 87), a log-phase broth culture standard curve and semiquantitative plate cultures (n = 68), we measured density of carriage. We compared qPCR genogrouping of DNA extracts from STGG-swabs and from plate culture lawns (n = 110) with purified isolates (n = 80). Swab storage resulted in only 10% loss of culture sensitivity. Direct sodC qPCR Nm detection yielded more positives (87/601, 14.5%) than culture (80/601, 13.3%). Most samples (57/110) positive by culture were also positive by qPCR and vice versa, but discrepancies (single positives) were frequent among low-density samples. sodC qPCR was positive in 79/80 isolates but in only 65 by ctrA qPCR. Density both by culture and qPCR varied across 4 orders of magnitude with the majority being low (<50 bacteria-gene copies/mL) and a minority being high (>1000). Genogrouping qPCRs yielded more positive results when performed on DNA extracts from lawn cultures. We provide the first description of the distribution of Nm carriage density. This could be important for understanding transmission dynamics and population-level effectiveness of adolescent vaccine programs. Storage of swabs frozen in STGG for batched laboratory analysis facilitates carriage studies and direct sodC qPCR for Nm combined with qPCR genogrouping of lawn culture extracts provides accurate, detailed description of colonization.

Haemophilus influenzae isolates survive for up to 20 years at − 70 °C in skim milk tryptone glucose glycerol broth (STGGB) if thawing is avoided during re-culture

Haemophilus influenzae remains a major cause of disease worldwide requiring continued study. Recently, isolates of Streptococcus pneumoniae and Moraxella catarrhalis, but not H. influenzae, were reported to survive long-term ultra-freeze storage in STGGB. We show that nontypeable H. influenzae isolates survive for up to 20years when thawing is avoided.

Comparison of three media for transport and storage of the samples collected for detection of avian influenza virus

Detection of avian influenza viruses (AIVs) is important for diagnosis, surveillance and control of avian influenza which is of great economic and public health significance. Proper transport and storage of samples is critical for the detection when the samples cannot be detected immediately. As recommended by some international or national authoritative entities and some publications, phosphate buffered saline (PBS), PBS–glycerol and brain heart infusion broth (BHIB) are frequently used for transport and storage of the samples collected for detection of AIVs worldwide. In this study, we compared these three media for transport and storage of simulated and authentic swab and feces samples collected for detection of AIVs using virus isolation and reverse transcription-PCR. The results suggest that PBS–glycerol is superior to PBS and BHIB as the sample transport and storage media. The results also suggest that the samples collected for detection of AIVs should be detected as soon as possible because the virus concentration of the samples may decline rapidly during storage within days at 4 or −20°C.

Viability and stability of Escherichia coli and enterococci populations in fecal samples upon freezing.

We studied the survival of Escherichia coli and enterococci populations in fecal samples of 7 host species after storage at -20 and -80 °C for 30 days. Composite fecal samples were collected from cows, chickens, horses, pigs, dogs, birds, and humans, and bacteria were enumerated before and after storage. Twenty-eight colonies of each bacterial species were typed before and after storage and the strains were assigned to different biochemical phenotypes (BPTs). A significant reduction in the number of E. coli was observed in all samples stored at -20 °C but in only 3 of those samples stored at -80 °C. However, the numbers of enterococci were similar in most stored samples (except cow and birds). The number and the distribution of E. coli and enterococci BPTs in fresh samples did not vary significantly from those stored at either temperature. Furthermore, the population structure of E. coli and enterococci did not change significantly after storage at -80 °C, this was always the case for those samples stored at -20 °C. We conclude that for those studies investigating E. coli or enterococci population structure, short-term storage (≤ 30 days) of fecal samples in a glycerol broth at -80 °C is a preferable option.

Changes in Thermal Resistance of Three Salmonella Serovars in Response to Osmotic Shock and Adaptation at Water Activities Reduced by Different Humectants

The purpose of this study was to investigate the effect of osmotic shock and adaptation at low water activity (aw) and the type of humectant used to lower the aw, on heat resistance of three Salmonella enterica serovars (Saintpaul 02-109, Tennessee 2053H, and Elmsbuettel 1236H). The serovars were grown (adapted) or transferred (osmotic shocked) in low-aw broths and subjected to heat treatment at 55°C for up to 45 min; samples were removed at 5-min intervals and immediately placed in an ice-water bath until plating. The aw of tryptic soy broth (TSB) was lowered by the addition of 20% (wt/wt) glycerol (aw 0.94), 4% (wt/wt) sodium chloride (NaCl; aw 0.97), or 35% sucrose (wt/wt) (aw 0.95). The type of humectant and cell adaptation significantly affected the D55°C-value. Cells merely suspended in 20% glycerol broth (i.e., nonadapted) prior to heat treatment showed a larger D55°C-value (3.0 to 3.9 min), when compared with that of cells adapted in the same medium (D55°C-values of 0.86 to 0.98 min). Interestingly, cells adapted to TSB plus glycerol were not more resistant to heat than were the controls. NaCl and sucrose showed a net protective effect for all serovars under both the adapted and nonadapted conditions, with sucrose providing the most protection. Highest D55°C-values were obtained for cultures adapted to TSB plus sucrose. Based on these results, the effect of reduced aw on thermal resistance of Salmonella serovars varies greatly, depending on medium constituents and adaptation of the pathogen in these media.

Vibrio cholerae Persisted in Microcosm for 700 Days Inhibits Motility but Promotes Biofilm Formation in Nutrient-Poor Lake Water Microcosms

Toxigenic Vibrio cholerae, ubiquitous in aquatic environments, is responsible for cholera; humans can become infected after consuming food and/or water contaminated with the bacterium. The underlying basis of persistence of V. cholerae in the aquatic environment remains poorly understood despite decades of research. We recently described a “persister” phenotype of V. cholerae that survived in nutrient-poor “filter sterilized” lake water (FSLW) in excess of 700-days. Previous reports suggest that microorganisms can assume a growth advantage in stationary phase (GASP) phenotype in response to long-term survival during stationary phase of growth. Here we report a V. cholerae GASP phenotype (GASP-700D) that appeared to result from 700 day-old persister cells stored in glycerol broth at −80°C. The GASP-700D, compared to its wild-type N16961, was defective in motility, produced increased biofilm that was independent of vps (p<0.005) and resistant to oxidative stress when grown specifically in FSLW (p<0.005). We propose that V. cholerae GASP-700D represents cell populations that may better fit and adapt to stressful survival conditions while serving as a critical link in the cycle of cholera transmission.

Loss of the meca gene during storage of methicillin-resistant Staphylococcus aureus isolates in Northwestern Nigeria

Preservation of strains in a microbiology laboratory is of great importance for quality control, teaching, and research. Freezing is a very common method of preservation and storage of microorganisms. The evaluation of new diagnostic or in vitro antimicrobial susceptibility tests for methicillin-resistant Staphylococcus aureus (MRSA) requires well-defined strain collections. The study was aimed at determining whether loss of mecA gene in MRSA is related to the storage method. A total of 1692 non-duplicate S. aureus isolates were collected from different human clinical specimens at 8 different health institutions in Northwestern Nigeria from February, 2008 to April, 2010. All the isolates were screened for methicillin resistance using disc diffusion method (DDM), screen agar method (SAM) and latex agglutination techniques (PBP). Thereafter, the isolates were stored in 16% v/v glycerol broth at -80°C. In December, 2011, the isolates were retested by polymerase chain reaction (PCR) which was used to amplify both the S. aureus specific sequence gene andmecA gene of 100 isolates, with the amplicon size of 107 and 532 bp. The prevalence rate of MRSA on DDM, SAM, and PBP were 26.3, 24.2 and 25.0%, respectively. Surprisingly, themecA gene was lost in 95.0% of 100 MRSA isolates after 2 years of storage at −80°C with the Micro bank system (Pro-lab Diagnostics, Austin, Tex.). This study demonstrates thatmecA can be lost from MRSA strains stored at −80°C with the Micro bank system. This finding has important implications for the management of strain collections and is of use for all future biobanking projects. Key words: Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA),mecA gene, storage, human, Northwestern Nigeria.

Selective enumeration of propionibacteria in Emmental-type cheese using Petrifilm™ Aerobic Count plates added to Lithium Glycerol broth

Propionibacteria derived from dairy products are relevant starter cultures for the production of Swiss and Emmental-type cheeses, and the monitoring of which is mandatory for proper quality control. This study aimed to evaluate an alternative procedure to enumerate propionibacteria, in order to develop a reliable and practical methodology to be employed by dairy industries. 2,3,5-triphenyltetrazolium chloride (TTC) inhibitory activity was tested against five reference strains (CIRM 09, 38, 39, 40 and 116); TTC at 0·0025% (w/v) was not inhibitory, with the exception of one strain (CIRM 116). Subsequently, the four TTC-resistant strains, three commercial starter cultures (PS-1, PB-I, and CHOO) and twelve Emmental-type cheese samples were subjected to propionibacteria enumeration using Lithium Glycerol (LG) agar, and Petrifilm™ Aerobic Count (AC) plates added to LG broth (anaerobic incubation at 30 °C for 7 d). Petrifilm™ AC added to LG broth presented high counts than LG agar (P<0·05) for only two reference strains (CIRM 39, and 40) and for all commercial starter cultures. Cheese sample counts obtained by both procedures did not show significant differences (P<0·05). Significant correlation indexes were observed between the counts recorded by both methods (P<0·05). These results demonstrate the reliability of Petrifilm™ AC plates added to LG broth in enumerating select Propionibacterium spp., despite some limitations observed for specific commercial starter cultures.

Comparison of three methods for the recovery of skin pathogens from impetigo swabs collected in a remote community of Northern Territory, Australia

Impetigo is a common infection in children living in remote areas. Immediate plating of impetigo swabs is the gold standard for bacterial recovery but is rarely feasible in remote regions. Bacterial culture increases our understanding of antibiotic resistance and strain diversity, which guides treatment protocols and epidemiological monitoring. We investigated three practical alternatives for recovering Streptococcus pyogenes and Staphylococcus aureus from transported swabs: dry swabs transported at 4°C with desiccant and plated within 48 h; swabs inoculated into skim milk tryptone glucose glycerol broth (STGGB), transported at 4°C, stored at -70°C and plated within 61 days; and ESwabs inoculated into Amies broth, transported at 4°C and plated within 48 h. Detection of Strep. pyogenes and Staph. aureus from simultaneously collected swabs was compared for the dry vs STGGB (36 sores) and the STGGB vs Amies (39 sores) methods. Swabs were collected from 43 children (75 sores sampled) in a remote community of Northern Territory, Australia in November 2011. The children had impetigo and were participating in the Skin Sore Trial [Australian Clinical Trials Registry ACTRN12609000858291]. Recovery of Strep. pyogenes for dry vs STGGB was 72% (26/36) and 92% (33/36) and for STGGB vs Amies was 92% (36/39) for both methods. Staphylococcus aureus recovery for dry vs STGGB was 69% (25/36) and 72% 26/36) and for STGGB vs Amies was 74% (29/39) and 85% (33/39). STGGB and Amies media provided higher recovery of Strep. pyogenes than dry swabs. These results and the opportunity to batch and store specimens for molecular studies support the use of STGGB transport media for future impetigo research.

Assessment of Process Parameters Influencing the Enhanced Production of Prodigiosin from Serratia marcescensand Evaluation of Its Antimicrobial, Antioxidant and Dyeing Potentials

Aims: Prodigiosin is a bright red pigment produced by certain strains of Serratia marcescens, characterized by a common pyrrolylpyrromethane skeleton. This pigment is found to possess antibacterial, antifungal, immunosuppressive and antiproliferative activity. The present study aimed at designing process parameters for the enhanced production of this pigment. Methodology and Results: Peptone glycerol broth was selected as the best synthetic medium. The effects of various media components and process parameters like carbon and nitrogen sources, temperature, pH, incubation period and other supplements were investigated. Maximal amount of prodigiosin was produced at temperature 25 °C, pH 7.0 and incubation period of 48 h. Supplementation of media with maltose and peptone yielded maximal amount of prodigiosin. Incorporation of minimal amount of supplements like silica gel, iron salts, inorganic phosphate also showed promising results. Chromatographic separations suggested that prodigiosin is made up of three different fractions (purple, orange and red). Further investigation of antimicrobial properties of prodigiosin revealed that it is a potent inhibitor against gram positive bacteria like Staphylococcus aureus and Bacillus cereus and fungal pathogens like Candida albicans, C. parapsilosis and Cryptococcus sp. This antimicrobial potency remained stable under a wide range of temperature and pH. The antioxidant capacity of prodigiosin was found to be 22.05 μg ascorbic acid equivalents/ml of extract. When applied to textiles, prodigiosin resisted the action of acid, alkali and detergent. Conclusion, Significance and Impact of study: Besides combating gram positive bacterial pathogens and some pathogenic yeasts, prodigiosin with strong dyeing and antioxidant activity may find broad applications in textile and therapeutic industries.

English

The conversion of glycerol to 1,3-propanediol (1,3-PD) is an environmentally friendly biological process and has attracted great interests worldwide. Efficient utilization of raw glycerol could bring significant economic benefits for 1,3-PD production. In the present study, the glycerol broth from strain Zygosacharomyces rouxii JL2011 was first used as the sole carbon source for 1,3-PD production by Klebsiella pneumoniae . The result indicates that the glycerol broth affected K. pneumoniae growth and 1,3-PD yield dramatically. Therefore, the raw glycerol was further prepared by extraction and purification, and the effect of raw glycerol on 1,3-PD production was investigated. The results obtained showed that the purified glycerol could be directly utilized in shake-flask culture by K. pneumoniae with a result comparable with that attained from pure glycerol. In addition, the fed-batch culture using raw glycerol as the substrate was conducted giving 56.1 g×L -1 with a yield of 0.40 g×g -1 glycerol and productivity of 1.12 g×L -1 ×h -1 . Key words: 1,3-propanediol, Klebsiella pneumoniae, Zygosacharomyces rouxii , raw glycerol.

Viability of respiratory pathogens cultured from nasopharyngeal swabs stored for up to 12 years at − 70 °C in skim milk tryptone glucose glycerol broth

Nasopharyngeal carriage studies are needed to monitor changes in important bacterial pathogens in response to vaccination and antibiotics. The ability to store original specimens frozen in skim milk tryptone glucose glycerol broth (STGGB) allows additional studies to be conducted without the need for further expensive field collection. Although sub-cultured isolates remain viable in this medium for many years, limited data are available to indicate viability of relatively low numbers of organisms present in nasopharyngeal specimens stored frozen over long periods of time. We conducted several studies whereby swabs stored in STGGB at − 70 °C for up to 12 years were thawed and aliquots cultured. Recovery of Streptococcus pneumoniae (72% positive from 269 swabs), Haemophilus influenzae (62% from 214) and Moraxella catarrhalis (81% from 162) was not significantly different from the original cultures: 69% (Risk Difference [RD] 3.0, 95% Confidence Interval [CI] − 4.7, 10.7), 66% (RD − 4.7, 95% CI − 13.8, 4.4) and 78% (RD 3.1, 95% CI − 5.7, 11.9) positive respectively. There was no trend in recovery from swabs stored for increasing lengths of time. We conclude that studies which rely on the viability of these respiratory pathogens can be conducted using original swabs stored at − 70 °C for at least 12 years.