luxS Gene and Biofilm Formation in Streptococcus uberis Isolated from Bovine Mastitis Cases

Background: Streptococcus uberis (S. uberis) is an environmental pathogen causing mastitis in Dairy cattle. It causes recurrent mastitis and reduction in milk production in livestock causing economic loss. The prevalence of S. uberis intramammary infections is due to ability of the organism to form biofilm in udder tissue. The present study is on in-vitro biofilm production, the correlation of luxS gene and the biofilm formation in S. uberis. Methods: A total of 91 mastitic milk samples were collected from cattle and buffaloes brought at Veterinary Hospitals and farms in Krishna, Guntur and West Godavari districts, Andhra Pradesh. The identification of the culture isolates was based on cultural and biochemical characteristics and confirmed by Polymerase Chain Reaction (PCR). The Streptococcus species cultures showing greyish, pinpointed colonies and/or aesculin hydrolysis on Edwards medium were further identified by various biochemical tests viz., catalase test, ninhydrin test, sodium hippurate hydrolysis test and type of haemolysis on 7% sheep blood agar. Confirmation of the isolates by PCR was followed by detection of biofilm formation using qualitative Congo red agar (CRA) method, quantitative microtiter plate (MTP) assay and biofilm gene (luxS) was detected using PCR.Conclusion: From this study it is suggestable that for biofilm study both phenotypic and genotypic methods should be taken together which can be influenced by various other factors also. MTP assay was a good choice for quantitative biofilm determination, which was giving a more accurate and understandable results. The results express that any of the isolates without luxS didn’t produce a strong biofilm and it is concluded that there may be other genes for regulation of biofilm production and/or luxS gene has a regulatory role for one or more genes related to biofilm formation in S. uberis.

Molecular Detection of Extended-Spectrum β-Lactamases- Producer Serratia marcescens Causing Neonatal Sepsis in Iraq

Serratia marcescens is an important nosocomial pathogen that causes a variety of infections, especially urinary tract and bloodstream infections. The emergence and spread of multidrug-resistant Serratia marcescens producing extended-spectrum beta-lactamases is a threat to public health worldwide at present. Extended-spectrum β-lactamases (ESβLs) including TEM, SHV, and CTX-M are the predominant types that confer resistance to beta-lactam group of antibiotics. Many reports have been investigated ESBL-producing isolates of Enterobacteriaceae in Iraq. However, there are few studies concerned about ESβL-producing Serratia marcescens particularly, detection of ESBLs encoding genes. Therefore this study aimed to identify ESβLs encoding genes in Serratia marcescens isolates from a neonatal intensive care unit. Fifty isolates were identified phenotypically using the VITEK® 2 compact system. For confirming the identification of bacterial strains, molecular detection of housekeeping LuxS gene was done using species-specific designed primers. Antibiogram was performed using the VITEK® 2 compact system. A phenotypic confirmatory test for ESβLs producers was performed using a combination disc method. The ESβLs encoding genes, including blaTEM, blaSHV, and blaCTX-M, were amplified using a PCR-based technique; the amplified products of some selected isolates were sequenced. Molecular detection of isolates using PCR-based amplification of the LuxS gene showed that all isolates possessed this gene. The patterns of antimicrobial resistance for isolates under study showed very high resistance to cephalosporins, while they were susceptible to carbapenem drugs and tigecycline. Findings based on the PCR technique showed that the prevalence of ESβLs encoding genes of isolates was 13 (26%), 31 (62%), and 46 (92%) for blaTEM, blaSHV, and blaCTX-M respectively. In the present study, it was concluded that blaCTX-M gene was the most prevalent ESβLs-encoding gene among ESβLs producing Serratia marcescens isolates.

Isolation and Identification of Serratia marcescens from Suspected Late Neonatal Sepsis in Intensive Care Unit

Background: Neonatal sepsis stays one of the main sources of morbidity and mortality both among infant in ICU, in light of the planning of the disease neonatal sepsis has been categorized into early and late-onset sepsis, where the latter occurs after one week of life and is often more insidious in onset than the former. Objective: To detect the rate of Serratia marcescens infection in neonatal sepsis in ICU by molecular technique. Methods: A total of 50 neonates with the age group 8 days to 30 days who were admitted to AL-Kadhumiya Teaching Hospital/ Baghdad during the period January to March ,2017 were recruited for this cross-sectional study. Approximately 3 ml of venous blood were obtained from each patients. These samples were examined for septicemia by blood culturing followed by API20 for quick identification of relevant bacteria. Furthermore, bacteria DNA was isolated directly from blood samples, and conventional PCR based on luxS gene, highly specific to S. marcescens, was achieved. Results: Blood culture were positive in 36(72 %) out of 50 samples; the most common bacterial causes were Staphylococcus aureus (18.7%), Pseudomonas aeruginosa (13.8%) and Serratia marcescens (11.1%), Molecular method revealed specific amplification of luxS gene in 12 samples (24%). Conclusion: Serratia marcescens has risen as a most widely recognized causative agent in late onset sepsis.

Quorum sensing in Enterococcus faecium, Enterococcus faecalis and Bacillus cereus strains isolated from ricotta processing

ABSTRACT: The quorum sensing phenomenon is a process of intra- and inter-species microbial communication involving the production and detection of extracellular signaling molecules. The autoinducer AI-2 has been proposed to serve as a ‘universal signal’ for interspecies communication. This study aimed to evaluate the capability of Enterococcus faecium, Enterococcus faecalis, and Bacillus cereus strains isolated from ricotta processing to produce quorum sensing signalling molecules (AI-2). The strains were evaluated for the presence of the luxS gene using the polymerase chain reaction. AI-2 quorum sensing signalling molecules were measured in relative light units (RLUs) using a luminometer. A total of 74% of E. faecium, 91% of E. faecalis, and 95% of B. cereus isolates were positive for luxS gene. In addition, the induced bioluminescence in Vibrio harveyi BB170 was observed in all strains, indicating the presence of the AI-2 autoinducer.