Changing patterns of bacterial profile and antimicrobial resistance in high-risk patients during the COVID-19 pandemic at a tertiary oncology hospital.

The widespread evolution of phenotypic resistance in clinical isolates over the years, coupled with the COVID-19 pandemic onset, has exacerbated the global challenge of antimicrobial resistance. This study aimed to explore changes in bacterial infection patterns and antimicrobial resistance during the COVID-19 pandemic. This study involved the periods before and during COVID-19: the pre-pandemic and pandemic eras. The surveillance results of bacterial isolates causing infections in cancer patients at an Egyptian tertiary oncology hospital were retrieved. The Vitek®2 or Phoenix systems were utilized for species identification and susceptibility testing. Statistical analyses were performed comparing microbiological trends before and during the pandemic. Out of 2856 bacterial isolates, Gram-negative bacteria (GNB) predominated (69.7%), and Gram-positive bacteria (GPB) comprised 30.3% of isolates. No significant change was found in GNB prevalence during the pandemic (P = 0.159). Elevated rates of Klebsiella and Pseudomonas species were demonstrated during the pandemic, as was a decrease in E. coli and Acinetobacter species (P < 0.001, 0.018, < 0.001, and 0.046, respectively) in hematological patients. In surgical patients, Enterobacteriaceae significantly increased (P = 0.012), while non-fermenters significantly decreased (P = 0.007). GPB species from either hematological or surgical wards exhibited no notable changes during the pandemic. GNB resistance increased in hematological patients to carbapenems, amikacin, and tigecycline and decreased in surgical patients to amikacin and cefoxitin (P < 0.001, 0.010, < 0.001, < 0.001, and 0.016, respectively). The study highlights notable shifts in the microbial landscape during the COVID-19 pandemic, particularly in the prevalence and resistance patterns of GNB in hematological and surgical wards.

Biofilm-mediated infections by multidrug-resistant microbes: a comprehensive exploration and forward perspectives.

A biofilm is a collection of microorganisms organized in a matrix of extracellular polymeric material. Biofilms consist of microbial cells that attach to both surfaces and each other, whether they are living or non-living. These microbial biofilms can lead to hospital-acquired infections and are generally detrimental. They possess the ability to resist the human immune system and antibiotics. The National Institute of Health (NIH) states that biofilm formation is associated with 65% of all microbial illnesses and 80% of chronic illnesses. Additionally, non-device-related microbial biofilm infections include conditions like cystic fibrosis, otitis media, infective endocarditis, and chronic inflammatory disorders. This review aims to provide an overview of research on chronic infections caused by microbial biofilms, methods used for biofilm detection, recent approaches to combat biofilms, and future perspectives, including the development of innovative antimicrobial strategies such as antimicrobial peptides, bacteriophages, and agents that disrupt biofilms.

Retained colistin susceptibility in clinical Acinetobacter baumannii isolates with multiple mutations in pmrCAB and lpxACD operons.

The progressive increase in the resistance rates to first- and second-line antibiotics has forced the reuse of colistin as last-line treatment for Acinetobacter baumannii infections, but the emergence of colistin-resistant strains is not uncommon. This has been long linked to acquired chromosomal mutations in the operons pmrCAB and lpxACD. Hence, such mutations are routinely screened in colistin-resistant strains by most studies. The current study was designed to explore the possible existence of pmrCAB and lpxACD mutations in colistin-susceptible isolates. For this purpose, the whole genome sequences of eighteen multi-/extensively drug resistant A. baumannii were generated by Illumina sequencing and screened for missense mutations of the operons pmrCAB and lpxACD. Most of the isolates belonged to global clones (GCs) including GC1 (n=2), GC2 (n=7), GC7 (n=2), GC9 (n=3), and GC11 (n=1). The minimum inhibitory concentrations (MICs) of colistin were determined by the broth microdilution assay. Seventeen isolates were fully susceptible to colistin with MICs ranging from (≤0.125 to 0.5 µg/ml). Interestingly, all colistin-susceptible isolates carried missense mutations in pmrCAB and lpxACD operons with reference to A. baumannii ATCC 19606. Overall, 34 mutations were found. Most substitutions were detected in pmrC (n=20) while no mutations were found in pmrA or lpxA. Notably, the mutation pattern of the two operons was almost conserved among the isolates that belonged to the same sequence type (ST) or GC. This was also confirmed by expanding the analysis to include A. baumannii genomes deposited in public databases. Here, we demonstrated the possible existence of missense mutations in pmrCAB and lpxACD operons in colistin-susceptible isolates, shedding light on the importance of interpreting mutations with reference to colistin-susceptible isolates of the same ST/GC to avoid the misleading impact of the ST/GC-related polymorphism. In turn, this may lead to misinterpretation of mutations and, hence, overlooking the real players in colistin resistance that are yet to be identified.

Increasing trends of colistin resistance in patients at high-risk of carbapenem-resistant Enterobacteriaceae.

INTRODUCTION: Occurrence of colistin-resistant Enterobacteriaceae in response to the unregulated use of this antibiotic has been documented. This study reports an investigation of colistin resistance rates among carbapenem-resistant enterobacterial clinical isolates. METHODS: A total of 196 multidrug-resistant Enterobacteriaceae isolates (Klebsiella pneumoniae (n = 100), Escherichia coli (n = 89) and Enterobacter cloacae (n = 7) were selected from Gram-negative isolates over one year. Susceptibility to antimicrobials was determined using Vitek2. Broth microdilution method was used to detect colistin antimicrobial susceptibility. Identification of ESBL and carbapenemases were both done phenotypically and by PCR. RESULTS: All the studied isolates showed multidrug-resistant phenotypes with 51.5% resistance to carbapenems (meropenem, imipenem). Very low resistance rates towards tigecycline (n = 9) 4.6% were found. Thirty-nine isolates (19.9%) showed reduced susceptibility to colistin among the MDR isolates. Sixty-four isolates (32.7%) were ESBL producers. Hundred isolates (51%) were carbapenemase producers using Carba NP test. The PCR amplification results revealed that 40 isolates (20%) harboured NDM-1 and 40 isolates contained OXA-48-like gene. Coexistence of both (NDM-1 and OXA-48-like) was observed in nine (4.59%) isolates. A Statistically significant relationship was observed between carbapenem resistance and each of the followings; OXA-48 producers (p= .009), amikacin resistance (p = .000), gentamicin resistance (p = .032), tobramycin resistance (p = .000), and tigecycline resistance (p-value ≤ .001). A statistical significance was detected between ESBL-producing isolates and carbapenem susceptible isolates ESBL producers with p = 0.000. CONCLUSION: An alarming sign is the increasing colistin resistance rates among carbapenem-resistant isolates. Aminoglycosides are still a therapeutic option to decrease the use of colistin and avoid further development of resistance.KEY MESSAGESHigh rates of colistin resistance among carbapenem-resistant Enterobacteriaceae.The choice of antibiotic is significantly associated with the clinical site of infection.Aminoglycosides are offered choices for treating multiple drug-resistant Enterobacteriaceae to preserve the colistin and carbapenems.

Tn7382, a novel composite transposon harboring blaNDM-1 and aphA6 in Acinetobacter baumannii.

OBJECTIVES: Co-transfer of carbapenem and amikacin resistance might contribute to the evolution of extensively drug resistant (XDR) Acinetobacter baumannii. The current study used bioinformatic tools and an in silico approach to investigate the potential mobility of a novel composite transposon co-harboring blaNDM-1 and aphA6. METHODS: The transposon, named here Tn7382, was recently identified in the chromosomes of two XDR A. baumannii isolates (M02 and M11) from Egypt. The draft genomes of M02 and M11 were generated by Illumina sequencing. Nucleotide homology of Tn7382 and flanking regions was analyzed using the Basic Local Alignment Search Tool. RESULTS: Tn7382 is derived from Tn125 and encompasses seven open reading frames [aphA6, ISAba125 transposase-coding gene, blaNDM-1, ble, iso, tat, cutA] enclosed by two direct copies of ISAba14. While described for the first time, Tn7382 was found in the chromosomes of five A. baumannii strains deposited in the NCBI database. Using the Artemis Comparison Tool, the potential mobility of Tn7382 was demonstrated in silico by comparative genomic analysis of two A. baumannii strains (TP1 and TP2) retrieved from the NCBI database. The transposon was acquired by TP2 at the same location as an ISAba14 element in the ancestral variant TP1 isolated from the same patient in the USA 11 days earlier. CONCLUSIONS: Here, we present the characteristics of Tn7382, a composite transposon flanked by ISAba14 and harboring the aphA6 and blaNDM-1 resistance genes. In silico analysis inferred the potential mobility of Tn7382, but experimental validation is still required.

Genetic Configuration of Genomic Resistance Islands in Acinetobacter baumannii Clinical Isolates From Egypt.

In Acinetobacter baumannii (A. baumannii), a wide repertoire of resistance genes is often carried within genomic resistance islands (RIs), particularly in high-risk global clones (GCs). As the first in Egypt, the current study aimed at exploring the diversity and genetic configuration of RIs in the clinical isolates of A. baumannii. For this purpose, draft genomes of 18 isolates were generated by Illumina sequencing. Disk diffusion susceptibility profiling revealed multidrug resistance (MDR) and extensive drug resistance (XDR) phenotypes in 27.7 and 72.2%, respectively. The highest susceptibility was noted for tigecycline (100.0%) followed by colistin (94.4%), for which an MIC50 of 0.25 µg/ml was recorded by the broth microdilution assay. Sequence typing (ST) showed that the majority of the isolates belonged to high-risk global clones (GC1, GC2, and GC9). A novel Oxford sequence type (ST2329) that also formed a novel clonal complex was submitted to the PubMLST database. A novel bla ADC variant (bla ADC-258) was also identified in strain M18 (ST85Pas/1089Oxf). In addition to a wide array of resistance determinants, whole-genome sequencing (WGS) disclosed at least nine configurations of genomic RIs distributed over 16/18 isolates. GC2 isolates accumulated the largest number of RIs (three RIs/isolate) followed by those that belong to GC1 (two RIs/isolate). In addition to Tn6022 (44.4%), the comM gene was interrupted by AbaR4 (5.5%) and three variants of A. baumannii genomic resistance island 1(AbGRI)-type RIs (44.4%), including AbaR4b (16.6%) and two novel configurations of AbGRI1-like RIs (22.2%). Three of which (AbaR4, AbaR4b, and AbGRI1-like-2) carried bla OXA-23 within Tn2006. With less abundance (38.8%), IS26-bound RIs were detected exclusively in GC2 isolates. These included a short version of AbGRI2 (AbGRI2-15) carrying the genes bla TEM-1 and aphA1 and two variants of AbGRI3 RIs carrying up to seven resistance genes [mphE-msrE-armA-sul1-aadA1-catB8-aacA4]. Confined to GC1 (22.2%), sulfonamide resistance was acquired by an ISAba1 bracketed GIsul2 RI. An additional RI (RI-PER-7) was also identified on a plasmid carried by strain M03. Among others, RI-PER-7 carried the resistance genes armA and bla PER-7. Here, we provided a closer view of the diversity and genetic organization of RIs carried by a previously unexplored population of A. baumannii.

Standardization and quantitative analysis of Araucaria Heterophylla extract via an UPLC-MS/MS method and its formulation as an antibacterial phytonanoemulsion gel.

Skin infections are among the bacterial infections that present significant therapeutic challenges due to antibiotic resistance. Recently, herbal products clutched a significant attention as safe replacements for other medications but their low aqueous solubility and poor bioavailability are considered major challenges which could be circumvented via formulation. As a species of genera Araucaria, Araucaria Heterophylla possesses pharmacological activities such as antioxidant and antibacterial actions, and this study aimed to standardize the extract of the plant against 4'''methoxyamentoflavone (as a main component of the extract) through a validated UPLC-MS/MS method and evaluate its antibacterial activity, which was followed by loading the standardized extract into a nanoemulsion to form a phytonanoemulsion (PNE), where the design analysis and optimization were performed through a simplex lattice design. The optimized PNE (PNE 3) was then loaded into HPMC/Pluronic F-127 gel (in ratio 1:4) to sustain the release of the active constituent. The heightened penetrability of PNE 3 gel was visualized via confocal laser scanning microscopy, and its prolonged effect was proved thru an in vivo study conducted on male Wistar rats. A histopathological study revealed the safety of the formulation when applied topically. Thus, PNE gel could be a potentially broad-spectrum antibacterial drug delivery system.

In Vitro Cytotoxic Activity and Phytochemical Characterization (UPLC/T-TOF-MS/MS) of the Watermelon (Citrullus lanatus) Rind Extract.

Reusing food waste is becoming popular in pharmaceutical industries. Watermelon (Citrullus lanatus) rind is commonly discarded as a major solid waste. Here, the in vitro cytotoxic potential of watermelon rind extracts was screened against a panel of human cancer cell lines. Cell cycle analysis was used to determine the induction of cell death, whereas annexin V-FITC binding, caspase-3, BAX, and BCL-2 mRNA expression levels were used to determine the degree of apoptosis. VEGF-promoting angiogenesis and cell migration were also evaluated. Moreover, the identification of phytoconstituents in the rind extract was achieved using UPLC/T-TOF-MS/MS, and a total of 45 bioactive compounds were detected, including phenolic acids, flavonoids aglycones, and their glycoside derivatives. The tested watermelon rind extracts suppressed cell proliferation in seven cancer cell lines in a concentration-dependent manner. The cytotoxicity of the rind aqueous extract (RAE) was higher compared with that of the other extracts. In addition to a substantial inhibitory effect on cell migration, the RAE triggered apoptosis in HCT116 and Hep2 cells by driving the accumulation of cells in the S phase and elevating the activity of caspase-3 and the BAX/BCL-2 ratio. Thus, a complete phytochemical and cytotoxic investigation of the Citrullus lanatus rind extract may identify its potential potency as an anticancer agent.

Epidemiological features of nosocomial Klebsiella pneumoniae: virulence and resistance determinants.

Aim: The authors aimed to examine antibiotic resistance genes and representative virulence determinants among 100 Klebsiella pneumoniae isolates with an emphasis on capsular serotypes and clonality of some of the isolates. Methods: PCR amplification of (rmpA, rmpA2, iutA, iroN and IncHI1B plasmid) and (NDM, OXA-48, KPC, CTX-M-15, VIM, IMP, SPM) was conducted. Wzi sequencing and multilocus sequence typing (MLST) were performed. Results: K2 was the only detected serotype in the authors' collection. RMPA2 was the most common capsule-associated virulence gene detected. All studied isolates harbored OXA-48-like (100%) and NDM (43%) (n = 43). ST147 was the most common sequence type. Conclusion: This work provides insight into the evolution of the coexistence of virulence and resistance genes in a tertiary healthcare setting in Cairo, Egypt.

Genomic Characterization of Extensively Drug-Resistant NDM-Producing Acinetobacter baumannii Clinical Isolates With the Emergence of Novel bla ADC-257.

Acinetobacter baumannii has become a major challenge to clinicians worldwide due to its high epidemic potential and acquisition of antimicrobial resistance. This work aimed at investigating antimicrobial resistance determinants and their context in four extensively drug-resistant (XDR) NDM-producing A. baumannii clinical isolates collected between July and October 2020 from Kasr Al-Ainy Hospital, Cairo, Egypt. A total of 20 A. baumannii were collected and screened for acquired carbapenemases (bla NDM, bla VIM and bla IMP) using PCR. Four NDM producer A. baumannii isolates were identified and selected for whole-genome sequencing, in silico multilocus sequence typing, and resistome analysis. Antimicrobial susceptibility profiles were determined using disk diffusion and broth microdilution tests. All bla NDM-positive A. baumannii isolates were XDR. Three isolates belonged to high-risk international clones (IC), namely, IC2 corresponding to ST570Pas/1701Oxf (M20) and IC9 corresponding to ST85Pas/ST1089Oxf (M02 and M11). For the first time, we report bla NDM-1 gene on the chromosome of an A. baumannii strain that belongs to sequence type ST164Pas/ST1418Oxf. Together with AphA6, bla NDM-1 was bracketed by two copies of ISAba14 in ST85Pas isolates possibly facilitating co-transfer of amikacin and carbapenem resistance. A novel bla ADC allele (bla ADC-257) with an upstream ISAba1 element was identified in M19 (ST/CC164Pas and ST1418Oxf/CC234Oxf). bla ADC genes harbored by M02 and M11 were uniquely interrupted by IS1008. Tn2006-associated bla OXA-23 was carried by M20. bla OXA-94 genes were preceded by ISAba1 element in M02 and M11. AbGRI3 was carried by M20 hosting the resistance genes aph(3`)-Ia, aac(6`)-Ib`, catB8, ant(3``)-Ia, sul1, armA, msr(E), and mph(E). Nonsynonymous mutations were identified in the quinolone resistance determining regions (gyrA and parC) of all isolates. Resistance to colistin in M19 was accompanied by missense mutations in lpxACD and pmrABC genes. The current study provided an insight into the genomic background of XDR phenotype in A. baumannii recovered from patients in Egypt. WGS revealed strong association between resistance genes and diverse mobile genetic elements with novel insertion sites and genetic organizations.

Antimicrobial Resistance Threats in the emerging COVID-19 pandemic: Where do we stand?

Antimicrobial resistance (AMR) continues to exert a substantial toll on the global health and world economy and is now expected to be hidden by COVID-19 for a while. The wrong consumption of antibiotics during the COVID-19 pandemic will raise disastrous effects on AMR management and antibiotic stewardship programs. This is related to the concerns extrapolated due to an increase in mortality rates in patients with bacterial coinfections. Importantly, the immune system of COVID-19 patients in regions with high AMR may be fighting on two fronts altogether, the virus and MDR bacteria. Current control policies to manage AMR and prioritization of antibiotic stewardship plans are mandatory during this pandemic. This review aims to discuss the rising concerns of the excess use of antibiotics in COVID-19 patients highlighting the role of bacterial coinfections in these patients. Types of prescribed antibiotics and the development of antibiotic resistance is addressed as well.

MALDI-TOF MS Overcomes Misidentification of the Uncommon Human Pathogen Candida famata by Routine Phenotypic Identification Methods.

Candida famata has been associated with the identifiable Candida infections that takes place in human and the identification error of this species possibly will result in misinterpretation of antifungal susceptibility and improper diagnosis; which will have a major effect on the prognosis and therapy of patients. Our objective is to correctly identify Candida spp. collected from patients at the intensive care units, New Cairo University teaching hospital in Cairo-Egypt using matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS). Hundred clinically isolated yeast strains were identified using API 20C AUX obtained from patients receiving care at intensive care units. ATB FUNGUS 3 strips were used to detect the minimum inhibitory concentration. Thirty-three non duplicate strains identified as C. famata were subjected to re-identification by MALDI-TOF MS. Our results revealed that isolates were initially identified as C. famata 33%, C. tropicalis 15%, C. albicans 12% and C. parapsillosis 10% using the phenotypic techniques. MALDI-TOF MS analyses results showed that the 33 C. famata isolates are C. tropicalis (n = 29), Trichosporon asahii (n = 2), C. parapsilosis (n = 1), and Aeromonas sobria (n = 1). Antifungal resistance was low in the Candida species, except for reduced susceptibility to itraconazole among C. krusei strains. This report shows that misidentification of C. famata is frequent when using conventional phenotypic methods of identification which result in challenges in treating fungal infections. MALDI-TOF MS is an accurate convenient substitute to classical approaches for fungal identification. In general, antifungal multidrug resistance is uncommon in our studied Candida species and yeast isolates.

Severe COVID-19 and Sepsis: Immune Pathogenesis and Laboratory Markers.

The ongoing outbreak of the novel coronavirus disease 2019 (COVID-19), induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has taken a significant toll on people and countries all over the world. The pathogenesis of COVID-19 has not been completely elucidated yet. This includes the interplay between inflammation and coagulation which needs further investigation. The massive production of proinflammatory cytokines and chemokines results in the so-called cytokine storm, leading to plasma leakage, vascular hyperpermeability, and disseminated vascular coagulation. This is usually accompanied by multiorgan failure. The extensive changes in the serum levels of cytokines are thought to play a crucial role in the COVID-19 pathogenesis. Additionally, the viral load and host inflammation factors are believed to have a significant role in host damage, particularly lung damage, from SARS-CoV-2. Interestingly, patients exhibit quantitative and qualitative differences in their immune responses to the virus, which can impact the clinical manifestation and outcomes of COVID-19. There needs to be a better understanding of the dynamic events that involve immune responses, inflammatory reactions, and viral replication in the context of the COVID-19 infection. Here, we discuss the main aspects of COVID-19 pathogenesis while supporting the hypothesis that inflammatory immune responses are involved in the progression of the disease to a more critical and fatal phase. We also explore the similarities and differences between severe COVID-19 and sepsis. A deeper understanding of the COVID-19 clinical picture as it relates to better-known conditions such as sepsis can provide useful clues for the management, prevention, and therapy of the disease.

Emergence of colistin resistance in multidrug-resistant Klebsiella pneumoniae and Escherichia coli strains isolated from cancer patients.

BACKGROUND: Colistin resistance is mainly driven by alterations in the Gram-negative outer membrane lipopolysaccharides and is caused, in most cases, by mutations in mgrB gene. However, the recent emergence of plasmid-encoded colistin resistance among Enterobacteriaceae strains represents a serious threat to global public health. In this paper we have investigated the rates of colistin resistance and the underlying mechanisms in 450 Klebsiella pneumoniae and Escherichia coli isolates obtained from cancer patients in Egypt. METHODS: Colistin susceptibility and minimum inhibitory concentrations were determined according to the European Committee on Antimicrobial Susceptibility Testing, by broth microdilution, and by E-test. The mcr-1, mcr-2 and mgrB genes were detected by PCR and then sequenced. Clonal diversity in colistin-resistant K. pneumoniae was evaluated by multilocus sequence typing. RESULTS: Forty (8.8%) colistin-resistant isolates, including 22 K. pneumoniae and 18 E. coli, were isolated over 18 months. Of these, 50% were carbapenem-resistant, out of which nine were blaOXA-48 and seven blaNDM-1 positive. The mechanisms of colistin resistance could be revealed only in three of the 40 resistant strains, being represented by mcr-1 in one blaNDM-1-positive E. coli strain and in one K. pneumoniae ST11 and by mgrB mutations, detected in one K. pneumoniae isolate. None of the studied isolates harbored mcr-2. CONCLUSIONS: Our results demonstrate a high frequency of colistin resistance in enterobacterial strains isolated from cancer patients, but a low prevalence of the most well known resistance mechanisms.

Multiple sequence types responsible for healthcare-associated Acinetobacter baumannii dissemination in a single centre in Egypt.

BACKGROUND: Acinetobacter baumannii is an increasingly worrying organism in the healthcare setting, due to its multidrug resistance and persistence. Prolonged hospitalisation, immunocompromised patients and excessive antibiotic exposure all contribute to increasing the risk of A. baumannii infections, which makes cancer patients a significant risk group. This study aims to investigate the dissemination of A. baumannii at the National Cancer Institute (NCI) in Cairo - Egypt. METHODS: All bacterial isolates were typed using Multi-locus Sequence Typing (MLST) to characterise the epidemiology of isolates. The intrinsic OXA-51-like, and the acquired carbapanemases OXA-23, - 24/40, - 58, NDM, IMP, and VIM were also amplified and sequenced to genetically identify mechanisms of carbapenem resistance. RESULTS: MLST results show a high degree of multi-clonal dissemination, with 18 different Sequence Types (STs) identified, including 5 novel. The majority of isolates belonged to International Clone (IC) 2, and carbapenem resistance was detected in 93% of isolates and mediated by blaOXA-23, blaOXA-58, blaNDM-1 and blaVIM-1. We also report the presence of a resistant ST732 (OXA-378) which has been previously identified in migratory birds. CONCLUSIONS: Multiple highly resistant clones were identified in a Cancer hospital in Cairo. It is vital that clinicians and healthcare workers are aware of the population of A. baumannii present in order to have appropriate treatment and infection control practices.

Probiotic Lactobacillus sp. inhibit growth, biofilm formation and gene expression of caries-inducing Streptococcus mutans.

Streptococcus mutans contributes significantly to dental caries, which arises from homoeostasic imbalance between host and microbiota. We hypothesized that Lactobacillus sp. inhibits growth, biofilm formation and gene expression of Streptococcus mutans. Antibacterial (agar diffusion method) and antibiofilm (crystal violet assay) characteristics of probiotic Lactobacillus sp. against Streptococcus mutans (ATCC 25175) were evaluated. We investigated whether Lactobacillus casei (ATCC 393), Lactobacillus reuteri (ATCC 23272), Lactobacillus plantarum (ATCC 14917) or Lactobacillus salivarius (ATCC 11741) inhibit expression of Streptococcus mutans genes involved in biofilm formation, quorum sensing or stress survival using quantitative real-time polymerase chain reaction (qPCR). Growth changes (OD600) in the presence of pH-neutralized, catalase-treated or trypsin-treated Lactobacillus sp. supernatants were assessed to identify roles of organic acids, peroxides and bacteriocin. Susceptibility testing indicated antibacterial (pH-dependent) and antibiofilm activities of Lactobacillus sp. against Streptococcus mutans. Scanning electron microscopy revealed reduction in microcolony formation and exopolysaccharide structural changes. Of the oral normal flora, L. salivarius exhibited the highest antibiofilm and peroxide-dependent antimicrobial activities. All biofilm-forming cells treated with Lactobacillus sp. supernatants showed reduced expression of genes involved in exopolysaccharide production, acid tolerance and quorum sensing. Thus, Lactobacillus sp. can inhibit tooth decay by limiting growth and virulence properties of Streptococcus mutans.

Antimicrobial resistance pattern and their beta-lactamase encoding genes among Pseudomonas aeruginosa strains isolated from cancer patients.

This study was designed to investigate the prevalence of metallo-ß-lactamases (MBL) and extended-spectrum ß -lactamases (ESBL) in P. aeruginosa isolates collected from two different hospitals in Cairo, Egypt. Antibiotic susceptibility testing and phenotypic screening for ESBLs and MBLs were performed on 122 P. aeruginosa isolates collected in the period from January 2011 to March 2012. MICs were determined. ESBLs and MBLs genes were sought by PCR. The resistant rate to imipenem was 39.34%. The resistance rates for P. aeruginosa to cefuroxime, cefoperazone, ceftazidime, aztreonam, and piperacillin/tazobactam were 87.7%, 80.3%, 60.6%, 45.1%, and 25.4%, respectively. Out of 122 P. aeruginosa, 27% and 7.4% were MBL and ESBL, respectively. The prevalence of bla(VIM-2), bla(OXA-10(-)), bla(VEB-1), bla(NDM(-)), and bla(IMP-1)-like genes were found in 58.3%, 41.7%, 10.4%, 4.2%, and 2.1%, respectively. GIM-, SPM-, SIM-, and OXA-2-like genes were not detected in this study. OXA-10-like gene was concomitant with VIM-2 and/or VEB. Twelve isolates harbored both OXA-10 and VIM-2; two isolates carried both OXA-10 and VEB. Only one strain contained OXA-10, VIM-2, and VEB. In conclusion, bla(VIM-2)- and bla(OXA-10)-like genes were the most prevalent genes in P. aeruginosa in Egypt. To our knowledge, this is the first report of bla(VIM-2), bla(IMP-1), bla(NDM), and bla(OXA-10) in P. aeruginosa in Egypt.