Rapid detection of carbapenemase-producing gram-negative bacteria directly from blood culture bottles for a reliable guided empiric therapy.

Bloodstream infections (BSIs) caused by multidrug-resistant bacteria are a critical life-threatening challenge which necessitates the urgency to trigger life-saving treatment in a timely manner. This study aimed to evaluate the time required for rapid detection of carbapenemase-producing Enterobacterales (CPE) directly from blood culture bottles to optimize empirical treatment of BSI, especially in pediatric and infant patients, using a cost-effective method. This study included 419 Gram-negative bacteria, of which Klebsiella pneumoniae and Escherichia coli were the most common CPE causing BSI in pediatric and neonatal patients. Phenotypic and genotypic resistance of the selected isolates (45 K. pneumoniae and 9 E. coli) were determined by VITEK-2 Compact system and PCR, respectively. BACT/ALERT bottles were spiked with isolates. Finally, colorimetric RESIST-BC assay and Vitek-2 compact system were evaluated for the rapid detection of carbapenem-resistant bacteria directly from positive blood culture bottles. All selected isolates were phenotypically resistant to carbapenems. PCR showed that blaNDM and blaOXA-48 were present in all isolates, blaVIM was present in 44.4%, while blaKPC and blaIMP were entirely absent. The RESIST-BC kit showed good agreement with PCR for blaNDM and blaOXA-48, demonstrating high sensitivity and specificity, but not with blaVIM. These findings point out that RESIST-BC assay demonstrated an exceptionally short detection time for CPE, completing all cases within the first hour after the blood culture bottles flagged positive. It is also superior in providing a clue for clinicians on antibiotic combinations that can be administered, depending on the type of ß-lactamases detected, promptly and efficiently, with low expenses.

A correlation study between virulence factors and multidrug resistance among clinical isolates of Proteus mirabilis.

Treatment of Proteus mirabilis infections is a challenge due to the high abundance of virulence factors and the high intrinsic resistance to antimicrobials. Multidrug resistance (MDR) and extensive drug resistance (XDR) further challenge the control of P. mirabilis infection. This study aimed to investigate the correlation between virulence determinants and multidrug resistance in 100 clinical isolates of P. mirabilis collected in Alexandria from December 2019 to June 2021. Susceptibility to antimicrobials was tested by the Kirby Bauer method. Detection of swarming, urease, protease, hemolysin, and biofilm formation was performed phenotypically and by PCR amplification of zapA, flaA, ureC, mrpA, atfA, ucaA, hpmA, and luxS. MDR and XDR were detected in 34% and 5%, respectively. All isolates were positive for motility, swarming, urease, and protease production. Ninety percent were positive for hemolysin production, while 73% formed biofilm. All isolates possessed the ureC and zapA genes. The luxS, flaA, ucaA, hpmA, mrpA, and atfA genes were detected in 99%, 98%, 96% 90%, 89%, and 84%, respectively. The presence of a single biofilm-related gene was statistically correlated with non-biofilm production (P= 0.018). It was concluded that P. mirabilis isolates from catheterized-urine samples were significantly associated with biofilm formation. MDR and virulence were not statistically correlated. A significant positive correlation was detected between some virulence genes in P. mirabilis. Non-MDR isolates of P. mirabilis had a high abundance of virulence factors with no statistically significant difference from MDR. Most of the MDR and all XDR isolates could produce biofilm.

Relevance of HLA-DP/DQ and INF-λ4 Polymorphisms to COVID-19 Outcomes.

Background: Single nucleotide polymorphisms provide information on individuals' potential reactions to environmental factors, infections, diseases, as well as various therapies. A study on SNPs that influence SARS-CoV-2 susceptibility and severity may provide a predictive tool for COVID-19 outcomes and improve the customized coronavirus treatment. Aim: To evaluate the role of human leukocyte antigens DP/DQ and IFNλ4 polymorphisms on COVID-19 outcomes among Egyptian patients. Participants and Methods: The study involved 80 patients with severe COVID-19, 80 patients with mild COVID-19, and 80 non-infected healthy volunteers. Genotyping and allelic discrimination of HLA-DPrs3077 (G/A), HLA-DQrs7453920 (A/G), and IFNλ4 rs73555604 (C/T) SNPs were performed using real-time PCR. Results: Ages were 47.9 ± 8, 44.1 ± 12.1, and 45.8 ± 10 years in severe, mild and non-infected persons. There was a statistically significant association between severe COVID-19 and male gender (p = 0.002). A statistically significant increase in the frequency of HLA-DPrs3077G, HLA-DQrs7453920A, and IFNλ4rs73555604C alleles among severe COVID-19 patients when compared with other groups (p < 0.001). Coexistence of these alleles in the same individual increases the susceptibility to severe COVID-19 by many folds (p < 0.001). Univariate and multivariate logistic regression analysis for the studied parameters showed that old age, male gender, non-vaccination, HLA-DQ rs7453920AG+AA, HLA-DPrs3077GA+GG, and IFNλ4rs73555604CT+CC genotypes are independent risk factors for severe COVID-19 among Egyptian patients. Conclusion: HLA-DQ rs7453920A, HLA-DPrs3077G, and IFNλ4rs73555604C alleles could be used as markers of COVID-19 severity.

Characterisation of Methicillin-Resistant Staphylococcus aureus from Alexandria, Egypt.

The present study aims to characterise clinical MRSA isolates from a tertiary care centre in Egypt's second-largest city, Alexandria. Thirty isolates collected in 2020 were genotypically characterised by microarray to detect their resistance and virulence genes and assign them to clonal complexes (CC) and strains. Isolates belonged to 11 different CCs and 14 different strains. CC15-MRSA-[V+fus] (n = 6), CC1-MRSA-[V+fus+tir+ccrA/B-1] (PVL+) (n = 5) as well as CC1-MRSA-[V+fus+tir+ccrA/B-1] and CC1153-MRSA-[V+fus] (PVL+) (both with n = 3) were the most common strains. Most isolates (83%) harboured variant or composite SCCmec V or VI elements that included the fusidic acid resistance gene fusC. The SCCmec [V+fus+tir+ccrA/B-1] element of one of the CC1 isolates was sequenced, revealing a presence not only of fusC but also of blaZ, aacA-aphD and other resistance genes. PVL genes were also common (40%). The hospital-acquired MRSA CC239-III strain was only found twice. A comparison to data from a study on strains collected in 2015 (Montelongo et al., 2022) showed an increase in fusC and PVL carriage and a decreasing prevalence of the CC239 strain. These observations indicate a diffusion of community-acquired strains into hospital settings. The beta-lactam use in hospitals and the widespread fusidic acid consumption in the community might pose a selective pressure that favours MRSA strains with composite SCCmec elements comprising mecA and fusC. This is an unsettling trend, but more MRSA typing data from Egypt are required.

Impact of ACE and Endoplasmic Reticulum Aminopeptidases Polymorphisms on COVID-19 Outcome.

Background: COVID-19 outcomes display multiple unexpected varieties, ranging from unnoticed symptomless infection to death, without any previous alarm or known aggravating factors. Aim: To appraise the impact of ACErs4291(A/T) and ERAP1rs26618(T/C) human polymorphisms on the outcome of COVID-19. Subjects and methods: In total, 240 individuals were enrolled in the study (80 with severe manifestations, 80 with mild manifestations, and 80 healthy persons). ACErs4291(A/T) and ERAP1rs26618(T/C) genotyping was performed using RT-PCR. Results: The frequency of the ACErs4291AA genotype was higher among the severe COVID-19 group than others (p < 0.001). The ERAP1rs26618TT genotype frequency was higher among the severe COVID-19 group in comparison with the mild group (p < 0.001) and non-infected controls (p = 0.0006). The frequency of the ACErs4291A allele was higher among severe COVID-19 than mild and non-infected groups (64.4% vs. 37.5%, and 34.4%, respectively), and the ERAP1rs26618T allele was also higher in the severe group (67.5% vs. 39.4%, and 49.4%). There was a statistically significant association between severe COVID-19 and ACErs4291A or ERAP1rs26618T alleles. The coexistence of ACErs4291A and ERAP1rs26618T alleles in the same individual increase the severity of the COVID-19 risk by seven times [OR (95%CI) (LL−UL) = 7.058 (3.752−13.277), p < 0.001). A logistic regression analysis revealed that age, male gender, non-vaccination, ACErs4291A, and ERAP1rs26618T alleles are independent risk factors for severe COVID-19. Conclusions: Persons carrying ACErs4291A and/or ERAP1rs26618T alleles are at higher risk of developing severe COVID-19.

Impact of bariatric surgery on the effectiveness of serological response after COVID-19 vaccination.

PURPOSE: The primary objective of the current study is to determine whether bariatric surgery reversed the negative impact of obesity on the serological response after the COVID-19 vaccination. This objective is achieved in two steps: (a) quantifying the negative impact of obesity on the serological response after COVID-19 vaccination if it is present, and (b) testing whether bariatric surgery reversed this impact. The secondary objective was to monitor the occurrence of adverse events. METHODS: This is a prospective cohort study between May 2021 and August 2021 on the strength of serological response after COVID-19 vaccination. Patients were classified into three groups. Group A (controls with normal or overweight), Group B (bariatric patients pre-operative), and Group C (bariatric patients post-operative). Quantitative antibodies against SARS­CoV­2 RBD with a strong neutralizing capacity were quantified from sera after at least 2 weeks post-vaccination. RESULTS: Of the 276 participants, Group A had n = 73, Group B had n = 126, and Group C had n = 77 patients. Overall, a strongly positive vaccine serological response was observed among 86% in group A, 63% in Group B, and 88% in Group C. Group C showed 5.33 times [95% CI 2.15 to 13.18] higher immune response than group B. Mild to moderate adverse events occurred in 30.1% [95% CI 24.7 to 35.9] of the study samples. Adverse events with the whole virus, mRNA, and vector vaccines occurred in 25%, 28%, and 37%, respectively. CONCLUSION: Vaccinating and bariatric surgery are safe and effective treatments in the serological response in patients who suffer from obesity.

The association of human cytomegalovirus with biomarkers of inflammation and immune activation in breast cancer.

BACKGROUND: The presence of human cytomegalovirus (HCMV) in breast cancer has been reported, suggesting a potential association between HCMV infection and breast carcinogenesis. OBJECTIVE: To evaluate the association between HCMV infection and immune activation and inflammatory markers in breast cancer. METHODS: HCMV DNA was detected from all patients using real-time PCR, Anti HCMV IgM and IgG antibodies were measured. IL-17 and IL-22 concentrations were detected by ELISA. Assessment of NLR and PLR was done, and cell proliferation was assessed using MTT assay. RESULTS: The results revealed a significantly increased prevalence of anti-HCMV IgG and HCMV DNA in patients compared to both benign and control groups where positive HCMV prevalence was significantly associated with vascular invasion, proliferation rate, high neutrophil-to-lymphocyte ratio (NLR), and elevated IL-17 serum level. Furthermore, we demonstrated that increased serum IL-17 in patients was markedly associated with tumor stage, vascular invasion, and high NLR. CONCLUSION: It can be concluded that HCMV infection may have vital roles in breast cancer pathogenesis. Moreover, altered peripheral blood cells and cytokines may result in disordered immune response in breast cancer patients.

Prevalence of trimethoprim/sulfamethoxazole resistance genes among Stenotrophomonas maltophilia clinical isolates in Egypt.

Stenotrophomonas maltophilia is an important multidrug resistant nosocomial pathogen. Trimethoprim/sulfamethoxazole (TMP/SMX) is considered the drug of choice for treatment of S. maltophilia infections, thus emerging resistance to TMP/SMX poses a serious threat. In the present study we aimed to investigate the frequency of TMP/SMX resistance genes (sul1, sul2, dfrA), and to evaluate their relatedness with integron 1 (int1), and insertion sequence common regions (ISCR) among 100 S. maltophilia from different clinical isolates in Egypt. Isolates were identified biochemically and confirmed by VITEK2. Detection of sul1, sul2, and dfrA genes, int1 and ISCR elements was performed by PCR. Among the 16 TMP/SMX resistant isolates, sul1 gene was detected in all of them, and it was associated with int1 gene presence in all resistant isolates. The sul2 gene was detected in 6 out of 16 resistant isolates (37.5%), and only 2 of the 16 resistant isolates (12.5%) harboured dfrA gene. ISCR was detected in 10 of the resistant isolates (62.5%) and in 4 of them it was associated with the presence of sul2 gene. Among the 84 TMP/SMX sensitive isolates, sul1 gene was detected in 15 (17.8%), int1 in 16 (19%) and ISCR in 6 (7.1%). None of the susceptible isolates had sul2 or dfrA genes. These findings point out an increasing frequency of TMP/SMX resistance genes among S. maltophilia clinical isolates in our region, so the adoption of prudent use of S. maltophilia antimicrobial agents and the establishment of a surveillance system are desperately needed.

Effect of azithromycin and phenylalanine-arginine beta-naphthylamide on quorum sensing and virulence factors in clinical isolates of Pseudomonas aeruginosa.

BACKGROUND AND OBJECTIVES: Pseudomonas aeruginosa is a problematic opportunistic pathogen causing several types of nosocomial infections with a high resistance rate to antibiotics. Production of many virulence factors in P. aeruginosa is regulated by quorum sensing (QS), a cell-to-cell communication mechanism. In this study, we aimed to assess and compare the inhibitory effect of azithromycin (AZM) and EPI-PAßN (efflux pump inhibitor-Phenylalanine-Arginine Beta-Naphthylamide) on QS system and QS-dependent virulence factors in P. aeruginosa clinical isolates. MATERIALS AND METHODS: A total of 50 P. aeruginosa isolates were obtained from different types of clinical specimens. Isolates were investigated for detection of QS system molecules by AHL cross-feeding bioassay and QS-dependent virulence factors; this was also confirmed by detection of QS genes (lasR, lasI, rhlR, and rhlI) using PCR assay. The inhibitory effect of sub-MIC AZM and EPI PAßN on these virulence factors was assessed. RESULTS: All the P. aeruginosa, producing QS signals C4HSL, failed to produce C4HSL in the presence of sub-MIC AZM, In the presence of EPI PAßN (20 µg/ml) only 14 isolates were affected, there was a significant reduction in QS-dependent virulence factors production (protease, biofilm, rhamnolipid and pyocyanin) in the presence of either 20 µg/ml EPI or sub-MIC of AZM with the inhibitory effect of AZM was more observed than PAßN. CONCLUSION: Anti-QS agents like AZM and EPI (PAßN) are useful therapeutic options for P. aeruginosa due to its inhibitory effect on QS-dependent virulence factors production without selective pressure on bacteria growth, so resistance to these agents is less likely to develop.

Prevalence of Genes Encoding Aminoglycoside-Modifying Enzymes and armA among Acinetobacter baumannii Clinical Isolates in Alexandria, Egypt.

INTRODUCTION: Acinetobacter baumannii (A.baumannii) is a ubiquitous pathogen responsible for serious infections in hospitalized patients with a high propensity to develop resistance to antimicrobial agents. The study aimed to determine the antimicrobial resistance patterns and the prevalence of aminoglycoside resistance genes among A. baumannii clinical isolates from patients in different intensive care units (ICUs) in Alexandria, Egypt. METHODS: A total of 100 A. baumannii isolates collected from ICU patients were confirmed as A. baumannii by VITEK 2 and the presence of the blaOXA-51 gene has been reported. Antimicrobial susceptibility testing was performed and Multiplex PCR was done for the detection of aminoglycoside resistance genes. RESULTS: Most of the isolates (82%) were resistant to all tested aminoglycosides; resistance was higher for kanamycin and neomycin, followed by amikacin. The predominant AMEs were aphA6 and aphA1 in 86% and 67% of the isolates, respectively; aacA4 and aacC1 were detected in 37% and 8%, respectively, while aadA1 and aadB were present in 34% and 4%, respectively. Furthermore, the armA gene was detected in 83% of the isolates. CONCLUSION: The results of this study revealed a high level carriage of armA and AMEs, which limit the usage of aminoglycoside as a treatment option for A. baumannii and make treatment extremely difficult.

Intestinal schistosomiasis among preschool and school-aged children in a rural setting near Alexandria: initiative for elimination.

OBJECTIVE: To assess the status of intestinal schistosomiasis among preschool-aged (PSAC) and school-aged children (SAC) and to compare the efficacy of praziquantel (PZQ) in both groups. METHODS: The study was conducted on 400 children; 103 PSAC and 297 SAC. Diagnosis of Schistosoma mansoni was based on triplicate Kato-Katz thick smears from a single stool sample. To identify the missed cases by Kato-Katz, 120 randomly selected negative cases (38 PSAC and 82 SAC) were screened by real-time PCR. All S. mansoni-positive cases by Kato-Katz were treated by crushed PZQ tablets. Four weeks after treatment, the cure rate was assessed by Kato-Katz smears and real-time PCR. RESULTS: The prevalence of S. mansoni with Kato-Katz was 7.8% among PSAC and 7.4% among SAC. Most of children (63.3%) had light-intensity infection. The cure rate was 100% among PSAC by both techniques, and 91%, and 77.2% among SAC by Kato-Katz and real-time PCR, respectively. In the 120 stool samples screened by real-time PCR, S. mansoni prevalence was 25%; 15.8% and 29.3% were among PSAC and SAC respectively. Treated cases showed a lower range of Ct values than untreated cases. Two melting temperature ranges (Tm = 83-87°C and 89-93°C) were recognised among uncured cases which may point to S. mansoni genetic variability. CONCLUSION: Continuous monitoring and inclusion of PSAC in schistosomiasis control programmes are crucial. Real-time PCR and other molecular tools are recommended for evaluation of the true prevalence, assessment of cure and further studies on genetic diversity.

Significance of Intracellular Adhesion Molecule-1 Polymorphism and IP-10 among Breast Cancer Patients.

Breast cancer (BC) is the second leading cause of women's death worldwide. Intercellular adhesion molecule-1 (ICAM-1) is involved in cell-cell interaction, migration and recruitment of immune cells. Polymorphisms in ICAM-1 gene may be involved in BC progression. IFN-gamma inducible protein-10 (IP-10) has the ability to recruit T-cells to induce cellular immunity and may have protective effect against BC development. The current study aimed to shed light on the role of of ICAM-1 SNP and/or serum levels of IP10 in BC in Egyptian female patients and detect possible correlation between these two factors and pathological prognostic markers. 40 breast cancer patients and 40 healthy females were enrolled in the study. Genotyping of ICAM-1 rs281437 SNP was done using real time PCR and serum levels of IP-10 were measured using ELISA. Allelic distribution demonstrated high frequency of ICAM-1 rs281437 CC genotype among BC patients (60%) compared to CT and TT alleles (30% and 10%, respectively). ICAM-1 rs281437 CC genotype showed 9.8 folds more risk to develop BC than other genotypes (95% CI=5.8-21.8, P<0.05). Relation between the studied alleles and hormonal receptors (ER, PR) showed that both ICAM-1 rs281437 CC and CT genotype have 5 folds more to be ER+, PR+ BC compared to TT allele (95% CI=0.21-117.8 and 0.15-125.4, respectively). Serum IP-10 levels were markedly decreased among breast cancer patients when compared with healthy controls (P = 0.001). In conclusion, ICAM-1 rs281437 CC genotype is significantly associated with breast cancer; females carrying CC allele may be at higher risk to develop BC than those carrying CT or TT genotypes. On the other hand, IP-10 may have a protective effect against breast cancer.

Impact of Interleukin 28B and ICAM-1 Genetic Polymorphisms on Response to Direct Antiviral Treatment Among HCV Infected Patients.

BACKGROUND: Single nucleotide polymorphisms (SNPs) of IL-28B and/or ICAM-1 could have a role in expecting a response from HCV infected patients to direct antiviral agents (DAAs). OBJECTIVE: The aim of the current study was to investigate the impact of IL-28B rs12979860 and rs8099917, and, ICAM-1 rs281437 SNPs on response to treatment with sofosbuvir + Daclatsvir ± Ribavirin, among HCV-infected Egyptian patients. METHODS: Whole blood genomic DNA was extracted from 120 participants (80 HCV-infected patients and 40 healthy volunteers). HCV-infected patients were subdivided into responders and nonresponders to DAAs. Liver function testing, anti-HCV antibodies, HCV-RNA viral load and HCV genotyping were performed. IL-28B and ICAM-1 SNPs were evaluated by real-time PCR. RESULTS: ALT and AST levels were significantly higher among non-responder HCV infected patients (P = 0.001*). 90% of the patients had HCV genotype 4a and the remaining 10% had 4l genotype. Allelic discrimination revealed that IL-28B rs12979860 T, IL-28B rs809917 T and ICAM-1 rs281437 C alleles were more frequent among HCV-infected patients (responders or non-responders) than controls. However, IL-28B rs8099917 G allele was more frequent among healthy controls. Regarding the response to DAAs treatment, HCV-infected patients with IL-28B rs8099917 GG genotype showed a significantly earlier viral response compared to those carrying TT alleles. ICAM-1 rs281437 CT alleles were non significantly more frequent among responders. However, IL-28B rs12979860 alleles did not show any difference. CONCLUSION: Genotyping of IL-28B rs8099917 is a useful independent tool for expecting a response of Egyptian HCV-infected patients to DAAs.

Emergence of blaVEB and blaGES among VIM-producing Pseudomonas aeruginosa clinical isolates in Alexandria, Egypt.

Thirty-three Pseudomonas aeruginosa isolates, resistant to one or more ß-lactams, were included in this study. Identification of tested strains was confirmed using MALDI-TOF/MS. Phenotypic and genotypic ß-lactamase patterns were investigated. Most of the isolates were resistant to carbapenems (32 out of 33) and to the extended-spectrum cephalosporins (ESC) (30 out of 33). Phenotypically, the production of extended-spectrum beta-lactamase (ESBL), metallo-ß-lactamases (MBL), and carbapenemases was detected in 10, 23, and 9 isolates, respectively. However, AmpC hyperproduction was not phenotypically detected among all isolates. Genotypically, ESBL and MBL encoding genes were detected in 23 and 27 isolates, respectively. Altogether 27 strains were detected as blaVIM positive and 16 strains carried blaOXA-10 gene. To the best of our knowledge, this is the first report of P. aeruginosa clinical isolates harboring blaVEB together with blaGES in Egypt, where 5 of our 30 ESC-resistant isolates showed this genotype. Our results confirmed that resistance of P. aeruginosa isolates to ß-lactam antibiotics is mediated via multiple ß-lactamases belonging to different molecular classes. To the best of our knowledge, this is the first report of blaVEB among P. aeruginosa clinical isolates from Egypt. Ten isolates harbored blaVEB and five of them co-harbored blaVEB together with blaGES, blaVIM, and blaOXA-10.

Seronegative and occult hepatitis C virus infections in patients with hematological disorders.

Studies of the association between seronegative or occult (OCI) hepatitis C virus (HCV) infection, and hematological disorders have yielded controversial results. The aim of this study was to investigate seronegative and OCI HCV infections in among patients with different hematological disorders. This study included 90 anti-HCV-negative patients with either benign or malignant hematological disorders (group I), along with 20 age- and sex-matched apparently healthy subjects, who served as controls (group II). We tested for HCV RNA in sera and PBMCs by RT-nested PCR and for liver enzyme activity. Seronegativity and OCI were detected in 66.7 % and 20 % respectively, of the studied cases (group I). OCI was more evident in Hodgkin lymphoma and thalassemia. A significant increase in AST activity was observed in the seronegative and OCI groups and in ALT and AST in HCV-seronegative or OCI and negative HCV patients (p ≤ 0.05). Seronegativity and OCI are a significant clinical problem in patients with hematological disorders, warranting wider use of molecular tests combined with periodic evaluations of liver functions for diagnostic purposes.

Correlation of quorum sensing and virulence factors in Pseudomonas aeruginosa isolates in Egypt.

INTRODUCTION: Pseudomonas aeruginosa is one of the most virulent nosocomial pathogens worldwide. Quorum sensing (QS) regulates the production of pathogenic virulence factors and biofilm formation in P. aeruginosa. The four genes lasR, lasI, rhlR,and rhlI were found to regulate this QS system. In this study, we aimed to assess the correlation between these four genes and QS-dependent virulence factors and to detect the inhibitory effect of clove oil on QS. METHODOLOGY: Fifty P. aeruginosa clinical isolates were collected. Susceptibility to different antibiotics was tested. Virulence factors including biofilm formation, pyocyanin production, and twitching motility were phenotypically detected. QS genes were amplified by polymerase chain reaction (PCR), and one strain subsequently underwent sequencing. The inhibitory effect of clove oil on virulence factors was also tested. RESULTS: A positive correlation was found between biofilm formation and the presence of lasR and rhlI genes. Twitching motility was positively correlated with the presence of lasR, lasI, and rhlI genes. On the other hand, no correlation was found between pyocyanin production and any of the studied genes. Only one isolate amplified all the tested QS gene primers, but it did not express any of the tested virulence factors phenotypically. Sequence analyses of this isolate showed that the four genes had point mutations. CONCLUSIONS: Results emphasize the importance of QS in P. aeruginosa virulence; however, QS-deficient clinical isolates occur and are still capable of causing clinical infections in humans. Also, clove oil has an obvious inhibitory effect on QS, which should be clinically exploited.