The use of plant growth promoting bacteria may prove useful in developing strategies to facilitate plant growth under normal as well as diverse abiotic stress conditions. The application of microbes with the aim of improving nutrients availability for plants is an important practice and necessary for sustainable agriculture. During the past couple of decades, the use of microbial inoculants for sustainable agriculture has increased tremendously in various parts of the world. Significant increases in growth and yield of agronomically important crops in response to inoculation with plant growth promoting (PGP) microbes have been repeatedly reported. The actual biodiversity of PGP microbes belong to different groups including Actinobacteria, Bacteroidetes, Balneolaeota Firmicutes, Proteobacteria and Spirochaetes. PGP bacteria are naturally occurring soil bacteria that aggressively colonize plant roots and benefit plants by providing growth promotion either directly by solubilization of phosphorus, potassium and zinc; production of indole acetic acids, gibberellic acid, cytokinin; biological nitrogen fixation or in-directly by production of ammonia, hydrogen cyanide, siderophore and biocontrol against different plant pathogens. In this review, we have discussed method of isolation, characterization, identification and biodiversity of bacteria associated with crops and further mechanisms of plant growth promotion under the normal as well as diverse abiotic stress conditions.

/pdf/plant-growth-promoting-bacteria-biodiversity-and-2gg9apuc0d.pdf

Plant growth promoting bacteria: Biodiversity and multifunctional attributes for sustainable agriculture.

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

Background: The development of multi-antibiotic resistant bacteria, especially Gram-negative bacteria which are the major cause of hospital-acquired infections worldwide, had been increasing. Escherichia coli and Klebsiella sp. had become more resistant to different classes of antibiotics, and the treatment of infections caused by these bacteria had developed into a challenge in both developed and developing countries. This study had determined the multi-antibiotic resistance (MAR) patterns of Escherichia coli and Klebsiella sp. isolated from clinical inpatient and outpatient samples. Method: The present study had used 50 E. coli and 48 Klebsiella sp. isolates. Antibiotic susceptibility test had been carried out by using disk diffusion method, and the interpretation of results of the zones of inhibition had accorded with Clinical Laboratory Standards Institute (CLSI). The antibiotics used had included the following: streptomycin, ciprofloxacin, erythromycin, nitrofurantoin, amikacin, gentamicin, ofloxacin, cefepime, oxacillin, colistin sulfate, cefotaxime, ceftazidime, pefloxacine, and cloxacillin. Results:E. coli and K. pneumoniae had shown high-resistance patterns. E. coli had exhibited high resistance against cloxacillin (96%), oxacillin (96%), erythromycin (88%), and most especially streptomycin (98%). Similarly, K. pneumoniae had presented a high resistance to streptomycin (88%), cloxacillin (92%), oxacillin (92%), and colistin (92%). E. coli had presented the highest multidrug resistance with a MAR index of 1.00. A total of 17 E. coli isolates had shown resistance to the 14 antibiotics tested. Conclusion:E. coli and Klebsiella sp. in clinical isolates in outpatients and inpatients in Ibadan, Western Nigeria had demonstrated high antimicrobial resistance. Thus, such condition should be considered a major public health concern, and measures must be taken to establish the sources and drivers of this problem.

Prevalence of Multi-Antibiotic Resistant Escherichia coli and Klebsiella species obtained from a Tertiary Medical Institution in Oyo State, Nigeria

Every year millions of people die due to fatal waterborne diseases around the world especially in developing countries like India. Sikkim, a northeastern state of India, greatly depends on natural water sources. About 80% of the population of Sikkim depends on natural spring water for domestic as well as agricultural use. Recent waterborne disease outbreaks in the state raises a concerning question on water quality. In this study, we analyzed water quality especially for the detection of Enterobacteriaceae members from four districts of the state. Isolation with selective culture media techniques and taxonomic characterization of Enterobacteriaceae bacteria with 16S rRNA gene showed the prevalence of Escherichia coli (37.50%), Escherichia fergusonii (29.41%), Klebsiella oxytoca (36.93%), Citrobacter freundii (37.92%), Citrobacter amalonaticus (43.82%), Enterobacter sp. (43.82%), Morganella morganii (43.82%), Hafnia alvei (32.42%), Hafnia paralvei (38.74%), and Shigella flexneri (30.47%) in the spring water of Sikkim. Antibiotic susceptibility test (AST) showed resistance of the isolates to common antibiotics like ampicillin, amoxicillin as well as to third generation antibiotics like ceftazidime and carbapenem. None of the isolates showed resistance to chloramphenicol. E. coli isolated from spring water of Sikkim showed presence of different virulence genes such as stx1 (81.81%), elt (86.66%), and eae (66.66%) along with resistance gene for ampicillin (CITM) (80%), quinolones (qnrB) (44.44%), tetracycline (tetO) (66.66%), and streptomycin (aadA1) (66.66%). The data indicates a high incidence rate of multiple antibiotic resistant enteric bacteria in the spring water of Sikkim. Additionally, the presence of enteric bacteria in the water samples indicates widespread fecal contamination of the spring water.

/pdf/distribution-of-antibiotic-resistant-enterobacteriaceae-3g2gdlhe1z.pdf

Distribution of Antibiotic-Resistant Enterobacteriaceae Pathogens in Potable Spring Water of Eastern Indian Himalayas: Emphasis on Virulence Gene and Antibiotic Resistance Genes in Escherichia coli.

Background: This study determined the prevalence and antibiotic susceptibility profiles of Staphylococcus aureus isolated from selected critical control points (farm, transport, abattoir, and retai...

Antibiotic Resistance in Staphylococcus aureus from Poultry and Poultry Products in uMgungundlovu District, South Africa, Using the "Farm to Fork" Approach.

Respiratory infections are common causes of morbidity and mortality worldwide. We sought to assess the multiple antibiotic resistance (MAR) index, fitness and virulence potential in Pseudomonas aeruginosa from patients with lower respiratory tract infections. Isolates were assessed for antimicrobial susceptibility, in vitro competitive fitness, and pigment, elastase and rhamnolipid production. Oxidative stress tolerance was determined on both planktonic and biofilm cells, and virulence potential was tested in a plant model. Mean MAR index for isolates was 0.34 (range 0.17–0.50). Whilst isolates exhibited good biofilm formation in the presence of ciprofloxacin, there was no significant difference in biofilm production over the concentration range assessed. Several drug-resistant strains were out-competed by a susceptible strain even in the presence of antibiotic. H2O2 exerted a greater oxidative stress than tert-butyl-hydroperoxide and, as expected, biofilms were more resistant than planktonic cells. Whilst most (81 %) isolates were pigmented there was no significant difference between pigmented and non-pigmented isolates when elastolytic activity was compared (P>0.05). More than half of the isolates produced the quorum sensing mediator rhamnolipid and infection of the plant model by bacteria occurred whether elastase or rhamnolipid was present or absent. These data suggest that non-pigmented strains of P. aeruginosa might pose an equally significant microbiological threat as pigmented strains even though pigment production appeared to be strongly associated with elastase expression. Whilst dual expression of elastase and rhamnolipid by these bacteria would cause severe tissue damage (as seen in the plant model), non-production of either does not prevent bacteria from causing serious infection.

Multiple antibiotic resistance index, fitness and virulence potential in respiratory Pseudomonas aeruginosa from Jamaica

Klebsiella pneumoniae is an important opportunistic pathogen with significant potential for virulence and multidrug resistance. Treatment failure often occurs because the pathogen may couple virulence and drug resistance with the stringent response. This study assessed the role of the spoT gene in environmental and nutritional stress tolerance, exopolysaccharide capsule production and biofilm formation. spoT mutants were constructed using the lambda red recombinase technique, and mutant and wild-type (WT) strains were exposed to limiting concentrations of carbon (glucose), phosphate and aminoacid, and environmental stresses of ethanol, salt and heat. Cell viability, capsule production and cell length were assessed as well as the ability to grow biofilm under antibiotic pressure using gentamicin and ceftazidime. spoT mutants were more susceptible to stresses versus WT; the reverse was true for survival during biofilm susceptibility assay (p < 0.05), especially when carbon and phosphate were present. spoT mutants were elongated and lacked a capsule versus WT and non-starved strains. The inability to produce capsule in mutants before and after starvation was likely a general effect of spoT mutation. These data suggest that the spoT-mediated stringent response is important for K. pneumoniae in conditions of nutrient limitation, environmental stress and antimicrobial pressure.

spoT-mediated stringent response influences environmental and nutritional stress tolerance, biofilm formation and antimicrobial resistance in Klebsiella pneumoniae.

Rochell T. Davis

Papers

Multiple antibiotic resistance index, fitness and virulence potential in respiratory Pseudomonas aeruginosa from Jamaica

spoT-mediated stringent response influences environmental and nutritional stress tolerance, biofilm formation and antimicrobial resistance in Klebsiella pneumoniae.