Role of interspecies bacterial communication in the virulence of pathogenic bacteria

Abstract

Bacteria live in a polymicrobial community where it interacts with biotic and abiotic factors using specific signalling molecules. Acyl homoserine lactones, autoinducing peptides, bacteriocins and polyamines are a few signals documented for interspecies signalling. The signalling system could be used for a coordinated behaviour categorised as Quorum sensing (QS). QS is a term used to define a cell – cell communication process amongst bacteria that helps to gather cell density information and regulate gene expression accordingly. QS had been demonstrated to play a pivotal role in bacterial pathogenesis by regulating the expression of different virulence factors affecting adhesion, invasion and survival within a tissue. In the current review, we discuss the role of interspecies bacterial communication in pathogenicity. The molecules involved in the interspecies bacterial communication affecting virulence factors required for the establishment of infection have been discussed in detail to gain an insight for development of strategies that can be proposed to combat bacterial infections by attenuating their communication systems. The knowledge on the role of interspecies bacterial communication on virulence will assist in understanding the factors affecting symptomatic and asymptomatic infections.     

Catheter-related candidemia caused by Candida lipolytica in a child with tubercular meningitis

Candida lipolytica is weakly pathogenic yeast, which is rarely isolated from the blood. We recovered this species from repeated blood samples and in the central venous catheter in a debilitated pediatric patient of tubercular meningitis. Identity was established on the basis of colony morphology and sugar assimilation tests (ID 32C assimilation profile). The fungemia and associated fever subsided after the removal of catheter and amphotericin B therapy. The data suggest that though of low virulence and usually a contaminant, C. lipolytica is emerging yeast pathogen in cases of catheter-related candidemia. Pathogenicity is indicated by isolation from repeated samples as in our case. Intensive therapy is recommended in cases not resolving spontaneously or responding to removal of catheter alone.     

Human immunodeficiency virus (HIV) gag antigen-specific T-helper and granule-dependent CD8 T-cell activities in exposed but uninfected heterosexual partners of HIV type 1-infected individuals in North India

Repeated exposure to human immunodeficiency virus (HIV) does not always result in HIV infection, and several cohorts of HIV-exposed but uninfected (EU) individuals have been described. We studied T-helper and granule-dependent cytotoxic T-lymphocyte (CTL) activities in a group of 30 EU partners of HIV type 1 (HIV-1)-infected individuals. HIV-1-specific helper-T-cell activity was studied by measuring the levels of interleukin 2 (IL-2) produced by peripheral blood mononuclear cells (PBMCs) and the granule-dependent CTL activity by measuring the intracellular levels of perforin and granzyme B expression in CD8+ T cells after stimulation with gag p24 antigen. Elevated IL-2 production by PBMCs after p24 stimulation occurred in EU individuals. The levels of perforin and granzyme B expression in CD8+ T cells were also higher among EU individuals than among healthy controls. HIV-specific helper-T-cell and granule-dependent CTL activities inversely correlated with the time since the last unprotected sexual exposure in these individuals. In our cohort, activation of T-helper and granule-dependent CTL activities against HIV might be due to unprotected sexual contact. These results indicate that HIV-1-specific T-cell responses could play a role in protection against acquiring infection in this cohort of EU individuals.     

Therapeutic IMC-C225 antibody inhibits breast cancer cell invasiveness via Vav2-dependent activation of RhoA GTPase

PURPOSE: Abnormalities in the expression and signaling pathways downstream of epidermal growth factor receptor (EGFR) contribute to progression, invasion, and maintenance of the malignant phenotype in human cancers. Accordingly, biological agents, such as the EGFR-blocking antibody IMC-C225 have promising anticancer potential and are currently in various stages of clinical development. Because use of IMC-C225 is limited, at present, only for treatment of cancer with high EGFR expression, the goal of the present study was to determine the effect of IMC-C225 on the invasiveness of breast cancer cells with high and low levels of EGFR expression. EXPERIMENTAL DESIGN: The effect of IMC-C225 on invasion was studied using breast cancer cell lines with high and low levels of EGFR expression. RESULTS: The addition of EGF led to progressive stress fiber dissolution. In contrast, cells treated with IMC-C225 showed reduced invasiveness and increased stress-fiber formation. Interestingly, IMC-C225 pretreatment was accompanied by EGFR phosphorylation, as detected using an anti-phosphorylated tyrosine antibody (PY99), which correlated with phosphorylation of Vav2 guanine nucleotide exchange factor and activation of RhoA GTPase irrespective of EGFR level, and Vav2 interacted with EGFR only in IMC-C225-treated cells. The underlying mechanism involved an enhanced interaction between beta1 integrins and EGFR upon IMC-C225 treatment. CONCLUSION: Here, we defined a new mechanism for IMC-C225 that cross-links integrins with EGFR, leading to activation of RhoA and inhibition of breast cancer cell invasion irrespective of the level of EGFR in the cells, thus providing a rationale for using IMC-C225 in the metastatic setting independent of the levels of EGFR.     

Cutaneous lesions in new born

Five hundred unselected newborn babies delivered in the Department of Obstetrics and Gynaecology, Unit II of SGBT Hospital attached to Government Medical College, Amritsar during April 2000 to October 2000 were examined for cutaneous lesions daily for the first five days after birth. Different cutaneous lesions were seen in 474(94.8%) newborns. The physiological skin changes observed in order of frequency were Epstein pearls in 305(61%), Mongolian spot in 301(60.2%), superficial cutaneous desquamation in 200(40%), icterus in 128(25.6%), milia in 119(23.8%), sebaceous gland hyperplasia in 107(21.4%), occipital alopecia in 94(18.8%), lanugo in 72(14.4%), peripheral cyanosis in 47(9.4%), breast hypertrophy in 29(5.8%) and miniature puberty in 28(5.6%) newborns. Of the transient non-infective skin diseases, erythema toxicum neonatorum was observed most commonly in 105(21%), followed by miliaria rubra in 103(20.6%) and acne neonatorum in 27(5.4%) newborns. The naevi and other developmental defects in the descending order were salmon patch in 69(13.8%), congenital melanocytic noevi in 10(2%), accessory tragi in 3(0.6%), spina bifida in 2(0.4%), hydrocephalus in 1(0.2%) and poliosis in 1(0.2%) newborns. Cradle cap was the only dermatitis observed in 50(10%) newborns. One (0.2%) case each of Harlequin ichthyosis and labial cyst was seen.