Nosocomial infection caused by vancomycin‐susceptible multidrug‐resistant Enterococcus faecalis over a long period in a university hospital in Japan

Compared with other developed countries, vancomycin‐resistant enterococci (VRE) are not widespread in clinical environments in Japan. There have been no VRE outbreaks and only a few VRE strains have sporadically been isolated in our university hospital in Gunma, Japan. To examine the drug susceptibility of Enterococcus faecalis and nosocomial infection caused by non‐VRE strains, a retrospective surveillance was conducted in our university hospital. Molecular epidemiological analyses were performed on 1711 E. faecalis clinical isolates collected in our hospital over a 6‐year period [1998–2003]. Of these isolates, 1241 (72.5%) were antibiotic resistant and 881 (51.5%) were resistant to two or more drugs. The incidence of multidrug resistant E. faecalis (MDR‐Ef) isolates in the intensive care unit increased after enlargement and restructuring of the hospital. The major group of MDR‐Ef strains consisted of 209 isolates (12.2%) resistant to the five drug combination tetracycline/erythromycin/kanamycin/streptomycin/gentamicin. Pulsed‐field gel electrophoresis analysis of the major MDR‐Ef isolates showed that nosocomial infections have been caused by MDR‐Ef over a long period (more than 3 years). Multilocus sequence typing showed that these strains were mainly grouped into ST16 (CC58) or ST64 (CC8). Mating experiments suggested that the drug resistances were encoded on two conjugative transposons (integrative conjugative elements), one encoded tetracycline‐resistance and the other erythromycin/kanamycin/streptomycin/gentamicin‐resistance. To our knowledge, this is the first report of nosocomial infection caused by vancomycin‐susceptible MDR‐Ef strains over a long period in Japan.     

Drug resistance and IS6110‐RFLP patterns of Mycobacterium tuberculosis in patients with recurrent tuberculosis in northern Thailand

The emergence of drug resistant Mycobacterium tuberculosis has become a global threat to tuberculosis (TB) prevention and control efforts. This study aimed to determine the drug resistance profiles and DNA fingerprints of M. tuberculosis strains isolated from patients with relapsed or retreatment pulmonary TB in Chiang Rai province in northern Thailand. Significant differences in multidrug resistance (MDR) (P = 0.025) and resistance to isoniazid (P = 0.025) and rifampin (P = 0.046) between first and second registrations of patients with retreatment TB were found. However, there were no significant differences in resistance to any drugs in patients with relapsed TB. The rate of MDR‐TB strains was 12.2% among new patients at first registration, 22.5% among patients with recurrence who had previously undergone treatment at second registration and 12.5% at third registration. Two retreatment patients whose initial treatment had failed had developed MDR‐TB with resistance to all TB drugs tested, including rifampin, isoniazid, streptomycin and ethambutol. IS6110‐RFLP analysis revealed that 66.7% (10/15 isolates) of MDR‐TB belonged to the Beijing family. In most cases, IS6110‐RFLP patterns of isolates from the same patients were identical in relapse and retreatment groups. However, some pairs of isolates from retreatment patients after treatment failure had non‐identical IS6110‐RFLP patterns. These results suggest that, after failure and default treatment, patients with retreatment tuberculosis have a significantly greater risk of MDR‐TB, isoniazid and rifampin resistance than do other patients.     

Heterogeneous virulence potential and high antibiotic resistance of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> strains isolated from Korean pneumonia patients

Pseudomonas aeruginosa is an opportunistic human pathogen of clinical importance that causes airway infections in immunocompromised patients. Here, we report the virulence-associated characteristics of strains of P. aeruginosa, isolated from the sputa of 25 Korean pneumonia patients. A high degree of genomic plasticity was observed by random amplified polymorphic DNA genotype analysis, suggesting that the infections were caused by strains with diverse genomic backgrounds. Biofilm formation of each isolate was heterogeneous in terms of their relative motilities. In addition, 48% of isolates were defective in the production of 3-oxo-C₁₂-HSL (PAI-1), a quorum sensing signal molecule. In these strains, PAI-1-dependent elastase production was correspondingly decreased, suggesting that a large number of strains were presumed to be quorum sensing deficient. Multidrug resistance (MDR) was seen in 56% of the isolates tested, and 44% of the MDR strains were resistant to five or more antibiotics. Taken together, our results provide additional insights into the virulence traits of P. aeruginosa clinical isolates, which will aid in treating P. aeruginosa infections in pneumonia patients.     

Pseudomonas aeruginosa Population Structure Revisited

At present there are strong indications that Pseudomonas aeruginosa exhibits an epidemic population structure; clinical isolates are indistinguishable from environmental isolates, and they do not exhibit a specific (disease) habitat selection. However, some important issues, such as the worldwide emergence of highly transmissible P. aeruginosa clones among cystic fibrosis (CF) patients and the spread and persistence of multidrug resistant (MDR) strains in hospital wards with high antibiotic pressure, remain contentious. To further investigate the population structure of P. aeruginosa, eight parameters were analyzed and combined for 328 unrelated isolates, collected over the last 125 years from 69 localities in 30 countries on five continents, from diverse clinical (human and animal) and environmental habitats. The analysed parameters were: i) O serotype, ii) Fluorescent Amplified-Fragment Length Polymorphism (FALFP) pattern, nucleotide sequences of outer membrane protein genes, iii) oprI, iv) oprL, v) oprD, vi) pyoverdine receptor gene profile (fpvA type and fpvB prevalence), and prevalence of vii) exoenzyme genes exoS and exoU and viii) group I pilin glycosyltransferase gene tfpO. These traits were combined and analysed using biological data analysis software and visualized in the form of a minimum spanning tree (MST). We revealed a network of relationships between all analyzed parameters and non-congruence between experiments. At the same time we observed several conserved clones, characterized by an almost identical data set. These observations confirm the nonclonal epidemic population structure of P. aeruginosa, a superficially clonal structure with frequent recombinations, in which occasionally highly successful epidemic clones arise. One of these clones is the renown and widespread MDR serotype O12 clone. On the other hand, we found no evidence for a widespread CF transmissible clone. All but one of the 43 analysed CF strains belonged to a ubiquitous P. aeruginosa “core lineage” and typically exhibited the exoS ⁺/exoU ⁻ genotype and group B oprL and oprD alleles. This is to our knowledge the first report of an MST analysis conducted on a polyphasic data set.     

Prevalence and antimicrobial resistance in Salmonella enterica isolated from broiler chickens,pigs and meat products in Thailand–Cambodia border provinces

This study aimed to examine the prevalence and antimicrobial resistance (AMR) of Salmonella isolates from broiler chickens, pigs and their associated meat products in the Thailand–Cambodia border provinces. A total of 941 samples were collected from pigs and broiler chickens at slaughter houses and from carcasses at local fresh markets in Sa Kaeo, Thailand (n = 554) and Banteay Meanchey, Cambodia (n = 387) in 2014 and 2015. From these samples, 345 Salmonella isolates were collected from Sa Keao (n = 145; 23%) and Banteay Meanchey (n = 200; 47%) and assayed for antimicrobial susceptibility, class 1 integrons and extended‐spectrum β‐lactamase (ESBL) genes. Serovars Typhimurium (29%) and Rissen (29%) were the most common serotypes found in Thai and Cambodian isolates, respectively. Multidrug resistance was detected in 34% and 52% of isolates from Sa Keao and Banteay Meanchey, respectively. The majority of the Thai isolates were resistant to ampicillin (72.4%), whereas most Cambodian isolates were resistant to sulfamethoxazole (71%). Eleven isolates from Sa Keao and 44 from Banteay Meanchey carried class 1 integrons comprising resistance gene cassettes. The most common gene cassette array was dfrA12‐aadA2 (61.1%). Six isolates were ESBL producers. The β‐lactamase genes found included bla_TEM‐1, bla_CTX‐M‐55 and bla_CMY‐2. Some of these class 1 integrons and ESBL genes were located on conjugative plasmid. In conclusion, multidrug‐resistant Salmonella are common in pigs, chickens and their products in the Thailand–Cambodia border provinces. Our findings indicate that class 1 integrons play a role in spread of AMR in the strains in this study.     

Phenotypic and genotypic profile of clinical and animal multidrug‐resistant Salmonella enterica isolates from Mexico

Aims

The objective of this study was to obtain a phenotypic and genotypic profile of Salmonella enterica including multidrug‐resistant (MDR) isolates from food‐producing animals and clinical isolates, as well as their genetic relatedness in two different States of Mexico (Jalisco and State of Mexico).

Methods and Results

A total of 243 isolates were evaluated in terms of antimicrobial resistance (AMR) and related genes through a disk diffusion method and PCR respectively; we found 16 MDR isolates, all of them harbouring the bla_CMY gene but not qnr genes, these isolates represent less than 10% of the collection. The pulsed‐field gel electrophoresis revealed a higher genotypic similitude within isolates of State of Mexico than Jalisco.

Conclusions

A low percentage of Salmonella isolates were resistant to relevant antibiotics in human health, nevertheless, the AMR and involved genes were similar despite the different serovars and origin of the isolates.

Significance and Impact of the Study

This investigation provided an insight of the current status of AMR of Salmonella isolates in two States of Mexico and pinpoint the genes involved in AMR and their epidemiological relationship, the information could help to determine an adequate therapy in human and veterinary medicine.     

Heterogeneity and phylogenetic relationships of community-associated methicillin-sensitive/resistant Staphylococcus aureus isolates in healthy dogs, cats and their owners

Aims: To investigate the distribution of staphylococcal enterotoxin genes (se) and the molecular features of community‐associated methicillin‐sensitive/resistant Staphylococcus aureus (CA‐MSSA/MRSA) isolates in the nostrils of healthy pets and their owners. Methods and Results: A total of 114 Staph. aureus isolates were identified from 1563 nasal swab samples, and CA‐MRSA accounted for 20·2% (n = 23) of the total identified isolates. CA‐MRSA isolates (91·3%, 21/23) harboured higher percentage of se than did CA‐MSSA isolates (58·2%, 53/91) (P < 0·01), and the two highest se profiles of CA‐MRSA were seb‐sek‐seq (42·9%, 9/21) and seb‐sek‐seq‐sep (28·6%, 6/21). Of the MSSAs, 42·8% (39/91) were resistant to at least one antimicrobial drug and 8·8% (8/91) were multidrug resistant (MDR). We identified nine staphylocoagulase (SC) types (I–VIII and X) and three multilocus sequence types (ST59‐MRSA‐IV/V, ST‐239‐MRSA‐V and ST241‐MRSA‐V). SC VII (23·4%, 22/94), a staphylococcal food poisoning isolate found mainly in Japan, and ST‐59‐MRSA‐IV/V (85%, 17/20), a widespread CA‐MRSA clone found mainly in Taiwan, both were the most predominant types. Phylogenetic analysis together with se and molecular characteristics obtained using pulsed‐field gel electrophoresis showed that high levels of antimicrobial resistance and the se‐carrying clone ST59‐MRSA‐IV/V‐SC VII were all clustered in genogroup 5. Conclusions: The CA‐MRSA clone of se‐carrying‐MDR‐ST‐59‐IV/V‐SC VII was identified predominantly in this study, and this clone might play a significant role in staphylococcal food poisoning in community settings. Significance and Impact of the Study: To our knowledge, this is the first study focussing on enterotoxin‐carrying CA‐MRSA/MSSA in pets and their owners, and the results support the future warnings in animal–human bond caused by CA‐staphylococci in the commonwealth and the need to take cautions worldwide.     

Proteome and carbon flux analysis of Pseudomonas aeruginosa clinical isolates from different infection sites

Pseudomonas aeruginosa is known as opportunistic pathogen frequently isolated from different infection sites. To investigate the expression rates of P. aeruginosa proteins commonly expressed by different clinical isolates, absolute protein quantities were determined employing a gel‐free and data‐independent LC‐IMS^E approach. Moreover, the metabolic diversity of these isolates was investigated by ¹³C‐metabolic flux analyses. 812 proteins were reproducibly identified and absolutely quantified for the reference strain P. aeruginosa PAO1, 363 of which were also identified and relatively quantified in all isolates. Whilst the majority of these proteins were expressed in constant amounts, expression rates of 42 proteins were highly variable between the isolates. Notably, the outer membrane protein OprH and the response regulator PhoP were strongly expressed in burned wounds isolates compared to lung/urinary tract isolates. Moreover, proteins involved in iron/amino acids uptake were found to be highly abundant in urinary tract isolates. The fluxome data revealed a conserved glycolysis, and a niche‐specific divergence in fluxes through the glyoxylate shunt and the TCA cycle among the isolates. The integrated proteome/fluxome analysis did not indicate straightforward correlation between the protein amount and flux, but rather points to additional layers of regulation that mediate metabolic adaption of P. aeruginosa to different host environments. All MS data have been deposited in the ProteomeXchange with identifier PXD002373 ( http://proteomecentral.proteomexchange.org/dataset/PXD002373 ).     

Reduced expression of virulence factors in multidrug-resistant Pseudomonas aeruginosa strains

MDR Pseudomonas aeruginosa strains are isolated from clinical specimens with increasing frequency. It seems that acquiring genes which determine antibiotic resistance usually comes at a biological cost of impaired bacterial physiology. There is no information on investigations comparing phenotypic differences in MDR and MDS P. aeruginosa strains in literature. The study included 150 clinical P. aeruginosa isolates (75 classified as MDS and 75 as MDR). PFGE analysis revealed five pairs of identical isolates in the group of MDR strains and the results obtained for these strains were not included in the statistical analyses. MDR strains adhered to polystyrene to a lesser extent than MDS strains. The growth rate in the liquid medium was significantly lower for MDR strains. Detectable amounts of alginate were present in the culture supernatants of seven MDS and six MDR strains. The MDR P. aeruginosa strains which were investigated produced significantly lower amounts of extracellular material binding Congo Red, lower lipolytic, elastase, LasA protease, phospholipase C activity and pyocyanin quantity in culture supernatants when compared with MDS strains. No significant differences were observed between MDR and MDS strains in proteolytic activity. In conclusion, the MDR P. aeruginosa strains have impaired virulence when compared to MDS strains.     

Overexpressed recombinant quorum quenching lactonase reduces the virulence,motility and biofilm formation of multidrug-resistant Pseudomonas aeruginosa clinical isolates

The increasing occurrence of resistance among Pseudomonas aeruginosa clinical isolates necessitates finding alternatives to antibiotics for controlling the infection of such pathogenic bacteria. In this study, lactonase gene ahl-1 from Bacillus weihenstephanensis isolate-P65 was successfully cloned and expressed in Escherichia coli BL21 (DE3) under the control of T7 promoter for utilizing its quorum quenching activity against three multidrug-resistant (MDR) P. aeruginosa clinical isolates. The biological activity of the overexpressed lactonase enzyme (Ahl-1), tested using a synthetic signal and Chromobacterium violaceum CV026 as a biosensor, displayed good catalytic activity using hexanoyl homoserine lactone (HHL) as a substrate and Chromobacterium violaceum (CV026) as a biosensor (77.2 and 133 nm min⁻¹ for the crude and the purified Ahl-lactonase enzymes, respectively). Upon challenging its ability to inhibit the virulence of three MDR P. aeruginosa clinical isolates, recombinant Ahl-1 successfully prevented the accumulation of acylhomoserine lactone signals resulting in a significant reduction in the investigated virulence determinants; protease (from 40 up to 75.5%), pyocyanin (48–75.9%), and rhamnolipids (52.7–63.4%) (P value < 0.05). Ahl-1 also displayed significant inhibitory activities on the swarming motility and biofilm formation of the three tested MDR P. aeruginosa clinical isolates (P value < 0.05). Consequently, Ahl-1 lactonase enzyme in this study is considered a promising therapeutic agent to inhibit P. aeruginosa pathogenicity with no fear of emergence of resistance.

     

Emergence of carbapenem non‐susceptible multidrug resistant Acinetobacter baumannii strains of clonal complexes 103B and 92B harboring OXA‐type carbapenemases and metallo‐β‐lactamases in Southern India

The molecular epidemiology and carbapenem resistance mechanisms of clinical isolates of Acinetobacter baumannii obtained from a south Indian tertiary care hospital were investigated by repetitive extragenic palindromic sequence PCR (REP‐PCR) and multi‐locus sequence typing (MLST). Analysis of resistant determinants was achieved by PCR screening for the presence of genes encoding OXA‐carbapenemases, metallo‐β‐lactamases (MBLs) and efflux pumps. REP‐PCR generated around eight clusters of high heterogeneity; of these, two major clusters (I and V) appeared to be clonal in origin. Analysis of representative isolates from different clusters by MLST revealed that most of the isolates belonged to sequence type 103 of CC103^B. Second most prevalent ST belonged to clonal complex (CC) 92^B which is also referred to as international clone II. Most of the isolates were multi‐drug resistant, being susceptible only to polymyxin‐B and newer quinolones. Class D β‐lactamases such as bla_{OXA‐51‐like} (100%), bla_{OXA‐23‐like} (56.8%) and bla_{OXA‐24‐like} (14.8%) were found to be predominant, followed by a class B β‐lactamase, namely bla_IMP‐1 (40.7%); none of the isolates had bla_OXA‐58 like, bla_NDM‐1 or bla_SIM‐1. Genes of efflux‐pump adeABC were predominant, most of isolates being biofilm producers that were PCR‐positive for autoinducer synthase gene (>94%). Carbapenem non‐susceptible isolates were highly diverse and present throughout the hospital irrespective of type of ward or intensive care unit. Although previous reports have documented diverse resistant mechanisms in A. baumannii, production of MBL and OXA‐type of carbapenamases were found to be the predominant mechanism(s) of carbapenem resistance identified in strains isolated from Southern India.     

Pseudomonas aeruginosa in a hydropathic facility: diversity, susceptibility and imipenem resistance mutation

Aims: To detect Pseudomonas aeruginosa in water and treatment equipment biofilms of a thermae hydropathic facility and to study antibiotic susceptibility and genetic diversity. Methods and Results: One hundred and fifty‐four planktonic isolates were obtained from 2220 water samples during 4 years. Seventy‐two biofilm isolates were obtained from 23 samples of inner parts of three inhalation equipments. Antibiotic susceptibility was determined by disc diffusion. All isolates were susceptible to tested antimicrobials, except two biofilm isolates and one planktonic isolate. Twenty‐one resistant mutants were observed (nine from biofilms), mostly with imipenem (IP) resistance (81%), by diminished expression of OprD porin, as it was observed by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE). Random amplification polymorphic DNA showed a genetically heterogeneous population that is spread through the entire system and persistent in time. IP resistance mutation ability was spread through the population. Conclusions: The permanent assessment of Ps. aeruginosa is necessary not only in water, as expressed in official programmes, but also in equipments where biofilms are evident. Ps. aeruginosa was more prevalent in biofilm populations and presented higher ability to adapt to antibiotic pressure. Significance and Impact of the Study: Twenty‐one million people use thermae in Europe. Official microbiological quality control programmes only consider water surveillance. Present study proves the need of a review on current official programmes.     

Biogenic selenium nanoparticles: characterization,antimicrobial activity and effects on human dendritic cells and fibroblasts

Tailored nanoparticles offer a novel approach to fight antibiotic‐resistant microorganisms. We analysed biogenic selenium nanoparticles (SeNPs) of bacterial origin to determine their antimicrobial activity against selected pathogens in their planktonic and biofilm states. SeNPs synthesized by Gram‐negative Stenotrophomonas maltophilia [Sm‐SeNPs(?)] and Gram‐positive Bacillus mycoides [Bm‐SeNPs(+)] were active at low minimum inhibitory concentrations against a number of clinical isolates of Pseudomonas aeruginosa but did not inhibit clinical isolates of the yeast species Candida albicans and C. parapsilosis. However, the SeNPs were able to inhibit biofilm formation and also to disaggregate the mature glycocalyx in both P. aeruginosa and Candida spp. The Sm‐SeNPs(?) and Bm‐SeNPs(+) both achieved much stronger antimicrobial effects than synthetic selenium nanoparticles (Ch‐SeNPs). Dendritic cells and fibroblasts exposed to Sm‐SeNPs(?), Bm‐SeNPs(+) and Ch‐SeNPs did not show any loss of cell viability, any increase in the release of reactive oxygen species or any significant increase in the secretion of pro‐inflammatory and immunostimulatory cytokines. Biogenic SeNPs therefore appear to be reliable candidates for safe medical applications, alone or in association with traditional antibiotics, to inhibit the growth of clinical isolates of P. aeruginosa or to facilitate the penetration of P. aeruginosa and Candida spp. biofilms by antimicrobial agents.     

Mutations of the β‐tubulin gene fragments from carbendazim‐resistant isolates of Pestalotiopsis sp. causing strawberry leaf blight in Chiang Mai,Thailand

Screening of field isolates of Pestalotiopsis sp. from strawberry leaf blight in Thailand identified 56 carbendazim‐resistant isolates. Of 56 isolates, 39 highly resistant (HR) phenotypes grew well on PDA amended with carbendazim even at ≥500 mg/L. Isolates with carbendazim‐resistant phenotype had a conspicuous mutation at particular sites in the beta‐tubulin (β‐tubulin) gene sequence. A β‐tubulin encoding gene from this pathogen was cloned and sequenced. Analysis of the β‐tubulin gene in highly resistant (HR) isolates showed a substitution at codon 79 and 102 from serine (AGT) to lysine (AAA) and valine (GTA) to alanine (GCA), respectively. The detection of such point mutations in the β‐tubulin gene allows the rapid screening to detect carbendazim‐resistant isolates in the field.     

Antibacterial potential of hGlyrichin encoded by a human gene

Emerging multidrug‐resistant (MDR) bacteria are an enormous threat to human life because of their resistance to currently available antibiotics. The genes encoding antibacterial peptides have been studied extensively and are excellent candidates for a new generation of antibiotic drugs to fight MDR bacteria. In contrast to traditional antibiotics, antibacterial peptides, which do not cause drug resistance, have an unparalleled advantage. However, because most antibacterial peptides originate in species other than humans, the hetero‐immunological rejection of antibacterial peptides is a key disadvantage that limits their clinical application. In this study, we identify hGlyrichin as a potential human antibacterial polypeptide. The hGlyrichin polypeptide kills a variety of bacteria including the MDR bacteria methicillin‐resistant Staphylococcus aureus, MDR Pseudomonas aeruginosa, and MDR tubercle bacillus. A 19 amino acid peptide (pCM19) at positions 42–60 of hGlyrichin is crucial for its antibacterial activity. The hGlyrichin polypeptide kills bacteria through the destruction of the bacterial membrane. In addition, all peptides that are homologous to hGlyrichin have antibacterial activity and can penetrate the bacterial membrane. Importantly, hGlyrichin does not cause hemolytic side effects in vitro or in vivo. Therefore, based on the virtues of hGlyrichin, i.e., the absence of hetero‐immunological rejection and hemolytic side effects and the unambiguous efficacy of killing pathogenic MDR bacteria, we propose hGlyrichin as a potential human antibacterial polypeptide. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.     

Antimicrobial Susceptibility Profiles of <Emphasis Type="Italic">Salmonella</Emphasis><Emphasis Type="Italic">enterica</Emphasis> Serotypes Recovered from Pens of Commercial Feedlot Cattle Using Different Types of Composite Samples

Salmonella enterica in cattle production systems may be associated with important human and animal disease issues. However, tremendous diversity exists among Salmonella recovered, and more information is needed about strains of greatest potential health concern, particularly those that are multidrug resistant (MDR). By characterizing Salmonella isolates from commercial feedlot pens, this study aimed to evaluate the strain diversity and prevalence of MDR Salmonella from different types of composite pen samples. Antimicrobial susceptibility profiles, serotype, and presence or absence of the integron-encoded intI1 gene were determined for 530 Salmonella isolates recovered using composite rope (n = 335), feces (n = 59), and water (n = 136) samples from 21 pens in 3 feedlots. The study investigated only pens with available isolates from multiple sample types. Most isolates (83.0%) of the 19 Salmonella serotypes identified were susceptible or intermediately susceptible to all the antimicrobials evaluated. Resistance to sulfisoxazole (14.9%), streptomycin (3.8%), and tetracycline (3.6%) were the most common. None of the isolates tested positive for a class 1 integron, and only 2.5% were resistant to multiple antimicrobials. All the MDR isolates, namely, serotypes Uganda (n = 9), Typhimurium (n = 2), and Give (n = 2), were resistant to at least five antimicrobials. Most MDR isolates (n = 11) were from two pens during 1 week within one feedlot. Overall, many Salmonella isolates collected within a pen were similar in terms of serotype and antimicrobial susceptibility regardless of sample type. However, MDR Salmonella and rare serotypes were not recovered frequently enough to suggest a general strategy for appropriate composite sampling of feedlot cattle populations for Salmonella detection and monitoring.     

Lactonase-expressing Lactobacillus plantarum NC8 attenuates the virulence factors of multiple drug resistant Pseudomonas aeruginosa in co-culturing environment

Pseudomonas aeruginosa possesses an arcade of both cell-associated and extracellular cytotoxic virulence factors which are regulated by a multi-component quorum sensing system. Many research studies report success of lactonase in combating the pathogenicity of P. aeruginosa but delivery of lactonase remains a challenge. The present study aims at developing a delivery vehicle for lactonase. Lactobacillus plantarum NC8 was used as host for aiiA (Bacillus thuringiensis 4A3 lactonase gene) using pSIP409 expression vector. pSIP409: aiiA construct was stably maintained in L. plantarum NC8. Co-culturing of multi-drug resistant (MDR) clinical isolates of P. aeruginosa and PAO1 with recombinant L. plantarum NC8 led to significant reduction (p < 0.001) in extracellular virulence factors like pyocyanin, protease, elastase and rhamnolipids in P. aeruginosa and also showed significant reduction in adhesion of P. aeruginosa strains to uroepithelial cells in vitro. This study shows the heterologous expression of AiiA lactonase in L. plantarum NC8. Co-culturing of lactonase expressing L. plantarum NC8 with MDR P. aeruginosa strains led to attenuation of their virulence significantly. These results underscore the potential application of recombinant L. plantarum NC8 with anti-quorum sensing properties to control infections caused by multidrug resistant P. aeruginosa.