Antimicrobial resistance, biofilm production and invasion of mammary epithelial cells by Enterococcus faecalis and Enterococcus mundtii strains isolated from bovine subclinical mastitis in Brazil.

Members of the genus Enterococcus are among the most relevant etiologic agents of bovine clinical and subclinical mastitis, a major problem for the dairy industry. In Brazil, clonal diversity, and multidrug resistance profiles related to bovine infections need further investigation. In this study, 11 bacterial strains recovered from mastitis subclinical cases detected in different farms of São Paulo, Brazil, were identified as Enterococcus faecalis (n = 8) and Enterococcus mundtii (n = 3) by biochemical testing and MALDI-TOF mass spectrometry. Pulsed-field gel electrophoresis categorized the enterococcal isolates into two main clusters (A and B) with similarity ranging from 85 to 100%. The isolates were shown to be resistant tetracycline (73%), erythromycin (73%), quinupristin-dalphopristin (64%), norfloxacin (9%), fosfomycin (9%) and linezolid (9%). Moreover, seven strains (64%) were considered multidrug-resistant. All the isolates were able to produce biofilms when grown in milk for 24 h: 54·54% were classified as moderate producers and 45·45% were weak producers. Interestingly, only two strains (Ef17 and Em42) remained as moderate biofilm producers after 48 h incubation. Moreover, all isolates showed no ability to form biofilm in tryptic soy broth (TSB) after 24 and 48 h incubation. In addition, cytoskeleton components were partially involved in E. faecalis and E. mundtii entry to epithelial cells as demonstrated by induction of actin stress fibre. In conclusion, enterococci isolates recovered from bovine subclinical mastitis were resistant to several classes of antibiotics, showing the ability to form biofilms in milk and invade mammary epithelial cells, suggesting an advantageous feature in mammary gland colonization during mastitis development. In addition, they can spread along the food chain by different routes and eventually constitute a possible threat for public health, including E. mundtii specie.

A current review of pathogenicity determinants of Streptococcus sp.

The genus Streptococcus comprises important pathogens, many of them are part of the human or animal microbiota. Advances in molecular genetics, taxonomic approaches and phylogenomic studies have led to the establishment of at least 100 species that have a severe impact on human health and are responsible for substantial economic losses to agriculture. The infectivity of the pathogens is linked to cell-surface components and/or secreted virulence factors. Bacteria have evolved sophisticated and multifaceted adaptation strategies to the host environment, including biofilm formation, survival within professional phagocytes, escape the host immune response, amongst others. This review focuses on virulence mechanism and zoonotic potential of Streptococcus species from pyogenic (S. agalactiae, S. pyogenes) and mitis groups (S. pneumoniae).

Biofilm formation on different pH conditions by Streptococcus agalactiae isolated from bovine mastitic milk.

Streptococcus agalactiae is among the most relevant aetiologic agent of bovine clinical and subclinical mastitis, a major problem for the dairy industry. In Brazil, clonal diversity, capsular typing and multidrug resistance profiles of S. agalactiae related to human and bovine infections need further investigation. Presently, S. agalactiae isolates of bovine subclinical mastitis, from Brazilian Northeastern region, were submitted to capsular and pulsed-field gel electrophoresis (PFGE)-typing, antimicrobial susceptibility and assays of biofilm formation at different time incubation and pH levels. Sixteen bovine isolates were characterized by polymerase chain reaction assay as S. agalactiae capsular type II (CTII) and classified by PFGE in A1/A2 (n = 06), B1/B2 (n = 06), C (n = 03) and D (n = 01) patterns. Bovine S. agalactiae CTII strains were classified as 25% multidrug-resistant (MDR) with susceptibility to penicillin, linezolid and vancomycin. Biofilm formation on abiotic surface was strain- and time-dependent with significantly higher rates at pH 6·5. In conclusion, S. agalactiae capsular type II isolates recovered from bovine subclinical mastitis produced different pH-dependent biofilm levels. Our findings suggest that biofilm production is modulated by environmental factors and provides S. agalactiae advantageous in colonizing mammary gland during mastitis development, including MDR strains. SIGNIFICANCE AND IMPACT OF THE STUDY: Streptococcus agalactiae is among the most relevant aetiologic agent of bovine clinical and subclinical mastitis, a major problem for the dairy industry. The disease may cause significant economic loss due to decreased production and milk quality and increased use of medicaments. Presently, data demonstrated that biofilm formation favours the establishment of infectious process in health mammary tissue by S. agalactiae and emphasizes that an acidic pH promotes adhesion by biofilm-forming bacterial strains. S. agalactiae strains (25%) showed resistance to tetracycline, azithromycin, erythromycin and clindamycin, and consequently were classified as multidrug-resistant strains.

Streptococcus agalactiae infection in cancer patients: a five-year study.

Although the highest burden of Streptococcus agalactiae infections has been reported in industrialized countries, studies on the characterization and epidemiology are still limited in developing countries and implementation of control strategies remains undefined. The aim of this retrospective study was to assess the epidemiological, clinical, and microbiological aspects of S. agalactiae infections in cancer patients treated at a Reference Brazilian National Cancer Institute - INCA, Rio de Janeiro, Brazil. We reviewed the clinical and laboratory records of all cancer patients identified as having invasive S. agalactiae disease during 2010-2014. The isolates were identified by biochemical analysis and tested for antimicrobial susceptibility. A total of 263 strains of S. agalactiae were isolated from cancer patients who had been clinically and microbiologically classified as infected. S. agalactiae infections were mostly detected among adults with solid tumors (94 %) and/or patients who have used indwelling medical devices (77.2 %) or submitted to surgical procedures (71.5 %). Mortality rates (in-hospital mortality during 30 days after the identification of S. agalactiae) related to invasive S. agalactiae infections (n = 28; 31.1 %) for the specific category of neoplasic diseases were: gastrointestinal (46 %), head and neck (25 %), lung (11 %), hematologic (11 %), gynecologic (4 %), and genitourinary (3 %). We also found an increase in S. agalactiae resistance to erythromycin and clindamycin and the emergence of penicillin-less susceptible isolates. A remarkable number of cases of invasive infections due to S. agalactiae strains was identified, mostly in adult patients. Our findings reinforce the need for S. agalactiae control measures in Brazil, including cancer patients.

Cytochemical study of Streptococcus agalactiae and macrophage interaction.

Light and electron microscopy were used to analyse the process of interaction of Streptococcus agalactiae (serotypes Ia, III, and V) with resident and activated mouse peritoneal macrophages. Transmission electron microscopy showed that adherence of the S. agalactiae serotype Ia, but not III and V serotypes, to the surface of activated macrophages triggers the respiratory oxidative burst as revealed by the presence of reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H]-oxidase in the phagocytic vacuoles. Fusion of macrophage lysosomes with bacteria-containing phagocytic vacuoles was observed in macrophages treated with Lucifer yellow as well as by localization of acid phosphatase for all serotypes.

Potential pathogenic role of aggregative-adhering Corynebacterium diphtheriae of different clonal groups in endocarditis.

Invasive diseases caused by Corynebacterium diphtheriae have been described increasingly. Several reports indicate the destructive feature of endocarditis attributable to nontoxigenic strains. However, few reports have dealt with the pathogenicity of invasive strains. The present investigation demonstrates a phenotypic trait that may be used to identify potentially invasive strains. The study also draws attention to clinical and microbiological aspects observed in 5 cases of endocarditis due to C. diphtheriae that occurred outside Europe. Four cases occurred in female school-age children (7-14 years) treated at different hospitals in Rio de Janeiro, Brazil. All patients developed other complications including septicemia, renal failure and/or arthritis. Surgical treatment was performed on 2 patients for valve replacement. Lethality was observed in 40% of the cases. Microorganisms isolated from 5 blood samples and identified as C. diphtheriae subsp mitis (N = 4) and C. diphtheriae subsp gravis (N = 1) displayed an aggregative adherence pattern to HEp-2 cells and identical one-dimensional SDS-PAGE protein profiles. Aggregative-adhering invasive strains of C. diphtheriae showed 5 distinct RAPD profiles. Despite the clonal diversity, all 5 C. diphtheriae invasive isolates seemed to display special bacterial adhesive properties that may favor blood-barrier disruption and systemic dissemination of bacteria. In conclusion, blood isolates from patients with endocarditis exhibited a unique adhering pattern, suggesting a pathogenic role of aggregative-adhering C. diphtheriae of different clones in endocarditis. Accordingly, the aggregative-adherence pattern may be used as an indication of some invasive potential of C. diphtheriae strains.

Cell surface hydrophobicity and the net electric surface charge of group B streptococci: the role played in the micro-organism-host cell interaction.

The cell surface hydrophobicity, net electric surface charge and cell adhesion of six group B streptococci strains were assessed. Treatment with trypsin reduced cytoadhesion of the six strains (80340, 90356, 85147, 90222, 90186 and 88641) and induced loss of surface negative charge in the other four strains (80340, 85147, 90222 and 90186). The same treatment increased the surface hydrophobicity of three strains (90356, 90222 and 88641). Neuraminidase treatment caused a decrease in the negative surface charge of all the strains resulting in significant increases in both cytoadhesion and surface hydrophobicity of five (80340, 90356, 85147, 90222 and 88641) and four (90356, 85147, 90222 and 88641) strains, respectively. This indicates that sialic acid residues are important anionogenic groups exposed on the streptococcal cell surface. Treatment of buccal epithelial cells with N-acetyl-beta-D-glucosaminidase made them less adherent for most of the strains (80340, 85147, 90222, 90186 and 88641) assayed.

Human monocytes and monocyte-derived macrophage phagocytosis of serotype III group B streptococci strains.

In this report group B streptococci (GBS) strains 90356 and 80340 isolated from liquor and vagina, respectively, were placed into contact with human peripheral blood monocytes (PBM) and macrophages derived from monocytes (MDM) by differentiation in vitro. The increased expression of CD16 and CD68 by macrophages cultured for 7 days compared with adherent monocytes supported the distinct maturation status of these cells. The number of viable intracellular bacteria of the 90356 strain was observed after 2 h of incubation with PBM (P < 0.001) and 0.5 h with MDM (P < 0.001). MDM cells seemed to present a more efficient mechanism of bacterial destruction of GBS type III, isolated from a case of meningitis. Viable cells of strain 80340, isolated from the vagina, were not detected in significant numbers in PBM and MDM phagocytic cells. These findings add to our current understanding of the roles played by multiple receptor-ligand systems in the uptake and pathogenesis of group B streptococci infection. Survival strategies of GBS, which interfere with macrophage bactericidal functions, might exist.

Sialic acid content and surface hydrophobicity of group B streptococci.

The sialic acid content and the cell-surface hydrophobicity index of 40 group B streptococci (GBS) strains were assessed. GBS isolated from invasive infections (virulent strains) presented an increased level of sialic acid content (1.4%) when compared with GBS isolated from asymptomatic patients (0.53%). Treatment of GBS strain 85634 with neuraminidase resulted in a decrease (about 25%) in the net negative surface charge as assessed by cell electrophoresis. This finding suggests that sialic acid residues are important anionogenic groups exposed on GBS cell surface. N-acetylneuraminic acid was the only sialic acid derivative characterized in the strain 85634 as evaluated by gas-liquid chromatography. GBS from different serotypes presented a hydrophobic index mean value of 0.9. Even though the sialic acid contributed effectively to the negative charge on GBS cell surface, no difference was observed in the hydrophobic index when virulent and avirulent strains were compared.

Potential pathogenic role of aggregative-adhering Corynebacterium diphtheriae of different clonal groups in endocarditis

Invasive diseases caused by Corynebacterium diphtheriae have been described increasingly. Several reports indicate the destructive feature of endocarditis attributable to nontoxigenic strains. However, few reports have dealt with the pathogenicity of invasive strains. The present investigation demonstrates a phenotypic trait that may be used to identify potentially invasive strains. The study also draws attention to clinical and microbiological aspects observed in 5 cases of endocarditis due to C. diphtheriae that occurred outside Europe. Four cases occurred in female school-age children (7-14 years) treated at different hospitals in Rio de Janeiro, Brazil. All patients developed other complications including septicemia, renal failure and/or arthritis. Surgical treatment was performed on 2 patients for valve replacement. Lethality was observed in 40 percent of the cases. Microorganisms isolated from 5 blood samples and identified as C. diphtheriae subsp mitis (N = 4) and C. diphtheriae subsp gravis (N = 1) displayed an aggregative adherence pattern to HEp-2 cells and identical one-dimensional SDS-PAGE protein profiles. Aggregative-adhering invasive strains of C. diphtheriae showed 5 distinct RAPD profiles. Despite the clonal diversity, all 5 C. diphtheriae invasive isolates seemed to display special bacterial adhesive properties that may favor blood-barrier disruption and systemic dissemination of bacteria. In conclusion, blood isolates from patients with endocarditis exhibited a unique adhering pattern, suggesting a pathogenic role of aggregative-adhering C. diphtheriae of different clones in endocarditis. Accordingly, the aggregative-adherence pattern may be used as an indication of some invasive potential of C. diphtheriae strains.