Medicine and Health Sciences Commons^™

Proteolytic Regulation Of Toxin-Antitoxin Systems By Clppc In Staphylococcus Aureus, Niles P. Donegan, Earl T. Thompson, Zhibiao Fu, Ambrose L. Cheung

Dartmouth Scholarship

Bacterial toxin-antitoxin (TA) systems typically consist of a small, labile antitoxin that inactivates a specific longer-lived toxin. In Escherichia coli, such antitoxins are proteolytically regulated by the ATP-dependent proteases Lon and ClpP. Under normal conditions, antitoxin synthesis is sufficient to replace this loss from proteolysis, and the bacterium remains protected from the toxin. However, if TA production is interrupted, antitoxin levels decrease, and the cognate toxin is free to inhibit the specific cellular component, such as mRNA, DnaB, or gyrase. To date, antitoxin degradation has been studied only in E. coli, so it remains unclear whether similar mechanisms of regulation …

Sarz Promotes The Expression Of Virulence Factors And Represses Biofilm Formation By Modulating Sara And Agr In Staphylococcus Aureus, Sandeep Tamber, Ambrose L. Cheung

Dartmouth Scholarship

Staphylococcus aureus is a remarkably adaptable organism capable of multiple modes of growth in the human host, as a part of the normal flora, as a pathogen, or as a biofilm. Many of the regulatory pathways governing these modes of growth are centered on the activities of two regulatory molecules, the DNA binding protein SarA and the regulatory RNAIII effector molecule of the agr system. Here, we describe the modulation of these regulators and their downstream target genes by SarZ, a member of the SarA/MarR family of transcriptional regulators. Transcriptional and phenotypic analyses of a sarZ mutant demonstrated that the …

Prevalence Of Mycoplasma Bovis And Other Contagious Bovine Mastitis Pathogens In Bulk Tank Milk Of Dairy Cattle Herds In Khon Kaen Province, Thailand, Jaruwan Kampa, Varaporn Sukolapong, Arunee Buttasri, Apirom Charoenchai

The Thai Journal of Veterinary Medicine

Mastitis is a most frequent and costly disease of dairy cattle worldwide. All three contagious mastitis pathogens, Mycoplasma bovis, Streptococcus agalactiae and Staphylococcus aureus were investigated in 55 bulk tank milk samples from dairy cattle herds in Khon Kaen Province Thailand, by nested PCR and/or conventional bacterial culture. Bulk milk somatic cell count (BMSCC) was used as indicator for mastitis problem; i.e. > 5x105 somatic cells/ml of milk. The prevalence of Mycoplasma bovis, Streptococcus agalactiae and Staphylococcus aureus were 1.8%, 21.8% and 7.3%, respectively. Results from BMSCC indicated mastitis problem in 47 herds. However, 34 high-BMSCC with negative-contagious pathogen identification samples …

Modulation Of Edna Release And Degradation Affects Staphylococcus Aureus Biofilm Maturation., Ethan E. Mann, Kelly C. Rice, Blaise R. Boles, Jennifer L. Endres, Dev Ranjit, Lakshmi Chandramohan, Laura H. Tsang, Mark S. Smeltzer, Alexander R. Horswill, Kenneth W. Bayles

Journal Articles: Pathology and Microbiology

Recent studies have demonstrated a role for Staphylococcus aureus cidA-mediated cell lysis and genomic DNA release in biofilm adherence. The current study extends these findings by examining both temporal and additional genetic factors involved in the control of genomic DNA release and degradation during biofilm maturation. Cell lysis and DNA release were found to be critical for biofilm attachment during the initial stages of development and the released DNA (eDNA) remained an important matrix component during biofilm maturation. This study also revealed that an lrgAB mutant exhibits increased biofilm adherence and matrix-associated eDNA consistent with its proposed role as an …

An Evaluation Of Methicillin Resistant Staphylococcus Aureus Survival On Five Environmental Surfaces Under Two Different Humidities, With And Without The Addition Of Bovine Serum Albumin, Courtney Ann Coughenour

UNLV Theses, Dissertations, Professional Papers, and Capstones

The spread of antibiotic resistant bacteria is a major public health concern, as they result in greater healthcare costs and increased morbidity and mortality rates. Methicillin resistant Staphylococcus aureus (MRSA) is one organism of particular concern, with the number of infections increasing in epidemic proportion. Bacterial surface contamination with MRSA is significant, as it may serve as a reservoir for transmission and have negative health implications. The purpose of this study was to evaluate survival of MRSA on five environmental surface materials; glass, wood, vinyl, plastic, and cloth. The effect of relative humidity (RH) and bovine serum albumin (BSA) were …

Regulation Of The Mazef Toxin-Antitoxin Module In Staphylococcus Aureus And Its Impact On Sigb Expression, Niles P. Donegan, Ambrose L. Cheung

Dartmouth Scholarship

In Staphylococcus aureus, the sigB operon codes for the alternative sigma factor σ^Band its regulators that enable the bacteria to rapidly respond to environmental stresses via redirection of transcriptional priorities. However, a full model of σ^Bregulation in S. aureus has not yet emerged. Earlier data has suggested that mazEF, a toxin-antitoxin (TA) module immediately upstream of the sigB operon, was transcribed with the sigB operon. Here we demonstrate that the promoter P_mazE upstream of mazEF is essential for full σ^B activity and that instead of utilizing autorepression typical of TA systems, sigB …

Antibiotic Resistance In Staphylococcus Aureus-Containing Cutaneous Abscesses Of Patients With Hiv, Gus W Krucke, Deanna E Grimes, Richard M Grimes, Thai D Dang

Journal Articles

PURPOSE: The aim of this study was to document the resistance patterns found in exudates from cutaneous abscesses of HIV-infected persons.

BASIC PROCEDURES: Patient records were reviewed on 93 culture and sensitivity tests performed on exudates taken from incised and drained abscesses of HIV-infected persons.

MAIN FINDINGS: Of the specimens, 84.6% were Staphylococcus aureus. Of these, 93.5% were penicillin resistant, 87% oxacillin resistant, 84.4% cephazolin resistant, 84.4% erythromycin resistant, 52.2% ciprofloxacin resistant, and 15.6% tetracycline resistant. Fifty-eight specimens were tested for clindamycin with 29.3% found resistant; 85.7% were methicillin-resistant S aureus (MRSA) (defined as resistant to both penicillin G and …

Interconnections Between Sigma B, Agr, And Proteolytic Activity In Staphylococcus Aureus Biofilm Maturation, Katherine J. Lauderdale, Blaise R. Boles, Ambrose L. Cheung, Alexander R. Horswill

Dartmouth Scholarship

Staphylococcus aureus is a proficient biofilm former on host tissues and medical implants. We mutagenized S. aureus strain SH1000 to identify loci essential for ica-independent mechanisms of biofilm maturation and identified multiple insertions in the rsbUVW-sigB operon. Following construction and characterization of a sigB deletion, we determined that the biofilm phenotype was due to a lack of sigma factor B (SigB) activity. The phenotype was conserved in a sigB mutant of USA300 strain LAC, a well-studied community-associated methicillin-resistant S. aureus isolate. We determined that agr RNAIII levels were elevated in the sigB mutants, and high levels of RNAIII expression are …

Epidemiology And Risk Factors For Staphylococcus Aureus Colonization In Children In The Post-Pcv7 Era, Grace M. Lee, Susan S. Huang, Sheryl L. Rifas-Shiman, Vriginia L. Hinrichsen, Stephen I. Pelton, Ken Kleinman, William P. Hanage, Marc Lipsitch, Alexander J. Mcadam, Jonathan A. Finkelstein

Public Health Department Faculty Publication Series

BACKGROUND:

The incidence of community-associated methicillin-resistant Staphylococcus aureus (MRSA) has risen dramatically in the U.S., particularly among children. Although Streptococcus pneumoniae colonization has been inversely associated with S. aureus colonization in unvaccinated children, this and other risk factors for S. aureus carriage have not been assessed following widespread use of the heptavalent pneumococcal conjugate vaccine (PCV7). Our objectives were to (1) determine the prevalence of S. aureus and MRSA colonization in young children in the context of widespread use of PCV7; and (2) examine risk factors for S. aureus colonization in the post-PCV7 era, including the absence of vaccine-type S. …

Multiple Antibiotic Resistant Staphylococcus Spp. In Environmental Settings, Stephen Shost

Legacy Theses & Dissertations (2009 - 2024)

Ninety staphylococci carrying the mecA gene, including 17 strains of methicillin-resistant Staphylococcus aureus (MRSA), were isolated from environmental settings within New York State. Waterborne staphylococci harboring mecA were isolated from multiple sources: the Hudson River near a combined sewage overflow; urban streams; freshwater and marine beaches; a swimming pool; swimming pool decks; combined sewage; as well as wastewater treatment plant (WWTP) primary sewage influent, mixed liquor, aeration water, and final (unchlorinated) effluent. Environmental MRSA strains were isolated from beach water (n=3); swimming pool deck water (n=1); Hudson River water (n=2); combined sewage (n=3); as well as wastewater treatment plant mixed …

Survival Of Certain Nosocomial Infectious Agents On The Surfaces Of Various Covering Materials, Hali̇l Yazgi, M. Hami̇dullah Uyanik, Mustafa Ertek, Ayşe Esi̇n Aktaş, Hakan İgan, Ahmet Ayyildiz

Turkish Journal of Medical Sciences

Aim: The aim of the present study was to investigate the survival time of some nosocomial infectious agents on the surface of various covering materials. Materials and Methods: Four kinds of flooring materials (vinyl and ceramic tile as floor covering material; and laminate and inox sheet as bench covering material) were experimentally contaminated with Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and vancomycin-resistant (VR) Enterococcus faecalis, which were frequently encountered in nosocomial infections. The survival periods of representative agents on the tested flooring materials were detected by culturing from the surfaces. Results: It was found that the survival periods were shorter …

A Case Report Of Ulcerative Lymphangitis (A Mini Review Of Causes And Current Therapies), Fereydon Rezazadeh Zavoshti, Amir Babak Sioofy-Khojine, Hassan Ali Mahpeikar

Turkish Journal of Veterinary & Animal Sciences

Ulcerative lymphangitis, or pigeon fever, is a bacterial infection of the lymphatic vessels of the skin in horses, cattle, sheep, and goats. Corynebacterium pseudotuberculosis is the classical cause of the disease. However, other pathogens such as Staphylococcus aureus have been isolated from cases of ulcerative lymphangitis. The aim of this report is to review the causes of pyoderma and skin abscesses in horses with specific attention to Staphylococcus aureus. A 10-year-old Thoroughbred stallion was examined in the suburbs of Tabriz (northwest of Iran) in February 2007. Skin abscesses were present around the hock joints on the hind limbs, on the …

Risk Factors For Acquisition Of Methicillin-Resistant Staphylococcus Aureus And Clonal Spread Of The Isolates In A Medical Intensive Care Unit, Emi̇ne Alp, Mehmet Yerer, Duygu Esel, Gökhan Metan, Mehmet Doğanay

Turkish Journal of Medical Sciences

Aim: Methicillin-resistant Staphylococcus aureus (MRSA) is still the commonest pathogen in hospital-acquired infections with high morbidity and mortality. MRSA colonization usually precedes infection and dissemination of the microorganism. The aim of this study was to determine risk factors for the colonization and infection with MRSA in a medical intensive care unit (MICU) and to show the genetic relation of strains. Materials and methods: This study was conducted prospectively between 1 December 2004 and 31 January 2006 in MICU. Patients (>16 years) admitted to the MICU were screened for MRSA on admission (in the first 48 hours), at the end …