Category Archives: Antibiotic Resistance

Research – Variation of antibiotic resistance in Salmonella Enteritidis, Escherichia coli O157 :H7 , and Listeria monocytogenes after exposure to acid, salt, and cold stress

Wiley Online


Bacteria with antibiotic‐resistant could seriously threaten to human health, increasing the treatment cost for infections and negatively affecting treatment outcomes. Stress adaptation is one possible mechanism for the acquisition or enhancement of antibiotic resistance in bacteria as a result of cross‐protection. In this study, the effects of acid, salt, and cold stress on the antibiotic resistance of Salmonella Enteritidis, Listeria monocytogenes , and Escherichia coli O157:H7 were investigated using the disc diffusion method. For S. Enteritidis, acidic growth conditions increased resistance to ciprofloxacin and erythromycin ( < .05), and addition of 4% NaCl to growth media decreased resistance to chloramphenicol ( < .05). Irrespective of pH and the NaCl concentration of the growth medium, refrigerated E. coli O157:H7 showed increased resistance to amoxycillin, ciprofloxacin, gentamicin, streptomycin, and erythromycin ( < .05). Acid‐adapted L. monocytogenes showed decreased the resistance to amoxycillin, ampicillin, chloramphenicol, ciprofloxacin, erythromycin, gentamicin, streptomycin, and tetracycline ( < .05). In conclusion, prolonged exposure of foodborne pathogens to acid, salt, and cold stress alters their antibiotic resistance. However, the effect of acid, salt, and cold stress on bacterial antibiotic resistance depend on both the bacterial species and the specific antibiotic. Therefore, multiple factors need to be considered for a foodborne antimicrobial resistant risk assessment.

Research – Optimization on antimicrobial effects of surfactin against Bacillus cereus spore


Abstract :The purpose of this study was to establish a three-variable bactericidal model of temperature, time, and concentration to determine the optimal conditions for Bacillus cereus  spore inactivation by surfactin. In order to obtain the binary regression equation of the inactivated spore model, a total of 17 simulations were performed using response surface methodology. The experimental results showed that the three factors each had a discernible but non-equal impact on the inactivation response value. Multiple regression analysis of experimental results using Design-Expert software yielded as the following equation: Optimal inactivation of spores was achieved by treatment with surfactin at a concentration of 4 mg/ml for 40 h at 53 °C, with the response value reaching 1.8. The spores were treated with surfactin under these conditions; the microstructural changes of spores were observed by scanning electron microscopy. We found that the structures of the outer wall of the spores were damaged, while the spores in the control sample showed no visible damage.

Research – Foodborne Klebsiella pneumoniae: Virulence Potential, Antibiotic Resistance, and Risks to Food Safety


CDC Klebsiella

Image CDC


Gastrointestinal carriage of Klebsiella pneumoniae is a predisposing factor for liver abscess in several Asian countries. To determine whether hypervirulent K. pneumoniae in the gut may be transmitted through food, we screened a range of raw and ready-to-eat retail food by culture and recovered K. pneumoniae in 21% (147 of 698) of samples tested. Based on PCR, no K. pneumoniae isolates carried the rmpA gene linked to community-acquired pyogenic liver abscess, providing no evidence of a link between food and liver disease. However, phenotypic resistance to multiple antibiotic classes was seen through disk diffusion tests, and carriage of genetic elements (wcaG and capsule types K1, K2, and K54) associated with increased virulence (8%, 11 of 147) was observed by PCR. Multidrug-resistant isolates were from raw vegetables, chicken or pork liver, and a ready-to-eat poultry dish; one multidrug-resistant K. pneumoniae isolate from raw bean sprouts was resistant to a third-generation cephalosporin (ceftriaxone). Although K. pneumoniae may be present in food without causing harm, we found isolates belonging to the K1 capsular serotype coexisting with the wcaG gene, one also conferring multidrug resistance. K. pneumoniae that carry antibiotic resistance genes, regardless of pathogenicity, may increase the available genetic pool of resistance along the food chain. Hygienic food handling practices are necessary to lower risks of acquiring K. pneumoniae and other opportunistic pathogens.

Research – Food safety risk posed to consumers of table eggs from layer farms in Gauteng Province, South Africa: Prevalence of Salmonella species and Escherichia coli , antimicrobial residues, and antimicrobial resistant bacteria

Wiley Online hazegg.jpg

The study conducted on 39‐layer farms in Gauteng Province, South Africa determined the prevalence and resistance of enteropathogens, and antimicrobial residues in table eggs collected from the farms. Eggs were tested for the presence of bacteria using standard methods. The resistance of bacteria to eight antimicrobial agents was determined using the disc diffusion method. Antimicrobial residues were detected in table eggs using the microbial inhibition test, enzyme‐linked immunosorbent assay (ELISA), and high performance liquid chromatography (HPLC). Risk factors for egg contamination by bacteria and antimicrobial residues were determined through a questionnaire survey of farmers. The farm prevalence of Salmonella spp. and Escherichia coli in table eggs was 7.7 and 48.7%, respectively. Nineteen (48.7%) and 2 (5.1%) of eggshells and egg contents, respectively, were positive for coli but only eggshells yielded Salmonella species, 2.0% (4 of 196). Overall, 71.4% of 49 coli isolates exhibited resistance to one or more antimicrobial agents. The farm prevalence and egg content prevalence of antimicrobial residues was 2.6 and 0.5%, respectively, with the detection of sulfonamide (79 ppb) and oxytetracycline (106 ppb). The prevalence of resistant coli and Salmonella spp. and the occurrence of antimicrobial residues in egg content may pose food safety and therapeutic threats to consumers.

Research – Antimicrobial Resistance in Salmonella enterica Serovar Paratyphi B Variant Java in Poultry from Europe and Latin America



Image CDC

Salmonella enterica serovar Paratyphi B variant Java sequence type 28 is prevalent in poultry and poultry meat. We investigated the evolutionary relatedness between sequence type 28 strains from Europe and Latin America using time-resolved phylogeny and principal component analysis. We sequenced isolates from Colombia, Guatemala, Costa Rica, and the Netherlands and complemented them with publicly available genomes from Europe, Africa, and the Middle East. Phylogenetic time trees and effective population sizes (Ne) showed separate clustering of strains from Latin America and Europe. The separation is estimated to have occurred during the 1980s. Ne of strains increased sharply in Europe around 1995 and in Latin America around 2005. Principal component analysis on noncore genes showed a clear distinction between strains from Europe and Latin America, whereas the plasmid gene content was similar. Regardless of the evolutionary separation, similar features of resistance to β-lactams and quinolones/fluoroquinolones indicated parallel evolution of antimicrobial resistance in both regions.

Research -ECCMID studies probe resistant pathogens in pets, pet food, and people


Two studies by Portuguese scientists presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) highlight concerns about the potential for transmission of multidrug-resistant (MDR) bacteria between companion animals and humans.

In one study, researchers from the University of Porto found high levels of MDR enterococci in raw-frozen dog food sold in the European Union. In another study, a household survey and molecular screening by researchers from the University of Lisbon found the colistin-resistance gene MCR-1 in two healthy humans and one dog with a skin infection.

But in a third study, researchers in Germany reported that pet ownership does not appear to be a significant risk factor for colonization with MDR organisms (MDROs).

Research – Burying or burning garbage boosts airborne bacteria, antibiotic resistance genes

Science Daily

Municipal solid waste is trash — such as plastic, food scraps and lawn clippings — that goes into garbage bins and doesn’t get recycled. Most of this waste is buried in landfills or is incinerated. Now, researchers reporting in ACS’ Environmental Science & Technology have shown that when disposed of in this way, municipal solid waste can be an important source of antibiotic-resistance genes in the air.

Residual antibiotics from discarded medications and other products can end up in municipal solid waste. Some microbes in the garbage are resistant to those antibiotics, and they can spread resistance genes to other bacteria, allowing them to survive in the presence of these drugs. But scientists hadn’t studied whether treating the garbage through incineration or landfilling releases these bacteria and genes into the air, where people or animals could breathe them in. So Yi Luo, Xiangdong Li and colleagues wanted to investigate the bacterial community and associated antibiotic-resistance genes in the municipal solid waste treatment system of Changzhou, a city in eastern China.


Research – Campylobacter chicken liver outbreak adds to evidence of risk

Food Safety News


Image CDC

Researchers have called for increased awareness to reduce the risk of Campylobacter outbreaks linked to incorrectly cooked chicken liver dishes.

Communication from food safety and public health authorities may be required. Any strategy should ensure the risk profile of poultry liver-containing dishes is raised and availability of evidence-based preventative strategies for food preparation promoted, according to the study published in the journal Epidemiology and Infection.

There were 19 people who got campylobacteriosis linked to an outbreak in England 2016; seven confirmed and 12 probable cases. Chicken liver pâté was most strongly associated with illness. Three cases reported an incubation period of less than 24 hours, consistent with other outbreaks of campylobacteriosis associated with poultry liver.

Diversorium Ltd., the company which owned and operated the Downe Arms, a hotel in Wykeham near Scarborough, was fined £8,000 ($10,300) in November 2017 for two food hygiene related offences related to the outbreak.

Research – Stressed-out dust is sharing antibiotic resistance genes


First study to show indoor dust bacteria have transferrable antibiotic resistance genes.

A new Northwestern University study is the first to find that bacteria living in household dust can spread antibiotic resistance genes. Although most bacteria are harmless, the researchers believe these genes could potentially spread to pathogens, making infections more difficult to treat.

“This evidence, in and of itself, doesn’t mean that antibiotic resistance is getting worse,” said Northwestern’s Erica Hartmann, who led the study. “It’s just one more risk factor. It’s one more thing that we need to be careful about.”

Research – Antibacterial mechanism of Tetrapleura tetraptera extract against Escherichia coli and Staphylococcus aureus and its application in pork

Wiley Online


The antibacterial activity and the mechanism of Tetrapleura tetraptera root extract against Escherichia coli and Staphylococcus aureus were investigated. The mechanism of action of T. tetraptera on tested bacterial species was predominantly characterized by the study of transmission electron microscopy, which revealed severe damage on the primary target which affected the cell integrity and cell membrane permeability. The loss of soluble proteins studied by bacterial protein sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis and the decreased adenosine triphosphate and DNA contents confirmed the leakage of cell wall. In addition, the studies revealed that the root extract of T. tetraptera could also disrupt the respiratory metabolism by inhibiting the bacteria through the Embden–Meyerhof–Parnas and the hexose monophosphate pathways. T. tetraptera extract possessed a high level of antimicrobial activity in pork, which significantly reduced total viable bacterial population. This study clearly indicates that the T. tetraptera could be a potential source of new antimicrobial agent which has proven effective activity against antibiotic‐resistant strains of pathogens.

Practical Applications

Tetrapleura tetraptera is a flowering plant native to Africa with a wide range of applicability in local cuisines and traditional medicine. The T. tetraptera root extract possesses high antimicrobial activity against both gram‐positive and gram‐negative bacteria. This study could contribute to the better understanding of antibacterial mechanism of T. tetraptera. As a natural food preservative, it has broad prospect to be utilized in the meat industry.