Padmini, B (2009) Bacteriological profile of clinically significant Coagulase Negative Staphylococci isolated from various clinical specimens with special reference to the Virulence factors. Masters thesis, Coimbatore Medical College, Coimbatore.
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Abstract
INTRODUCTION : Coagulase-Negative Staphylococci (CoNS) are ubiquitous microorganisms that predominate the normal skin flora. Due to their ubiquitous nature and relatively low virulence, CoNS have long been considered to be clinically insignificant, and hence when isolated from clinical specimens, the clinicians and the microbiologists discarded them as contaminants. However, it is noted that under appropriate conditions, CoNS can produce serious human diseases and the incidence of such infections has clearly increased in recent years. Moreover they are seen as one among the most commonly isolated organisms in the clinical microbiological laboratory. According to the National Nosocomial Infections Surveillance System, CoNS are among the five most commonly reported pathogens in hospitals. The postulated reasons for the current prevalence and clinical importance of these organisms include their great numbers on the skin, their selection as a result of wide spread usage of broad-spectrum antibiotics in the hospital, their ability to adhere to and form biofilm on the surfaces of vascular catheters and other medical devices, and their meager nutritional requirements. The emergence of CoNS as important potential pathogens is partly due to the increased usage of transient / permanent medical devices and partly due to the growing appreciation of this group of organisms as opportunistic pathogens. Infection caused by CoNS is increasingly common in patients having indwelling catheters, orthopedic appliances, prosthetic devices and urinary catheters. AIMS AND OBJECTIVES : The aim of the present study is to assess the various microbiological aspects of Coagulase-Negative Staphylococci (CoNS) and its clinical significance with special emphasis on demonstration of virulence factors and methicilin resistance. OBJECTIVES: 1. To identify CoNS among bacterial isolates from various clinical specimens. 2. Speciation and biotyping of CoNS isolates. 3. To ascertain the significance of pathogenic CoNS in causation of infections, by demonstrating the virulence factors. 4. To evaluate the biofilm production by different methods. 5. To evaluate antimicrobial susceptibility pattern - methicilin resistance and multidrug resistance among CoNS. MATERIALS AND METHODS : A total of 135 CoNS Strains were isolated from deep wounds, blood samples, pus, urine samples, body fluids, and IV catheter tips by conventional cultural methods. Of the 135 isolates, 90 were considered as clinically significant. The following criteria were considered while determining the clinical significance of a CoNS isolate. Inclusion Criteria: 1. Strains isolated in pure culture from specimens, 2. The culture was from body fluids (blood, cerebrospinal fluid, urine, pleural fluid, joint fluid, peritoneal fluid, etc.), or from a purulent, draining wound 3. High colony-count urine samples (>105 organisms per ml), 4. I.V. catheter tips > 15 colonies, 5. Significant clinical symptoms of diseases like fever, purulent discharge from wound, signs of general & local Inflammation, and repeated urinary tract infections, 6. Laboratory criteria like increased count of WBC, ESR, CRP, etc. Exclusion criteria: 1. Organism isolated as mixed growth, 2. Growth only in broth, 3. Growth after 72 hrs, 4. No significant clinical symptoms of disease in patients. RESULTS : The present study was conducted on 90 clinically-significant CoNS isolates. All strains were negative for both clumping factor and tube coagulase. The most common source for all CoNS species combined was wound infections and pus, constituting 39 out of 90 strains (43%), followed by 21 (23%) from blood cultures, 14 (15.5%) from urine samples, 6 (6.6%) from catheters, 2 (3.9%) from cerebrospinal fluid, 4 (1.9%) from ascitic fluid, and 5 from other sources. CONCLUSION : The study of CoNS isolated from various sources indicated 66% of isolates as clinically significant and S. epidermidis as the most frequently isolated species. The speciation was done by five tests simple scheme method, which is reliable, simple, inexpensive, and accurate procedure and will prove useful in microbiology laboratory as simplicity and speed are very essential in diagnostic and therapeutic purpose. The most important virulent factor biofilm production in CoNS was associated mostly in prosthetic device related conditions like orthopedic wounds, PDF, CSF and IV catheters and biofilm on implanted foreign material can cause major medical and economic sequel. Antimicrobial susceptibility testing revealed the wide spread methicillin resistance and MDR among CoNS and is particularly notable with S. epidermidis. The prevalence of MDR was more in the methicillinresistant isolates and in slime producers as cells in biofilms are normally more resistant to antibiotics. It is necessary to predict the potential pathogenicity by biofilm demonstration in vitro which can be easily done by MTP method and antibiotic susceptibility of each clinical isolates, early in the course of infection, which will be helpful to provide appropriate antibiotic therapy and prevent implant removal. Taking into consideration that the etiological importance of CoNS has often been neglected, the present investigation confirmed that these microorganisms should not be ignored or classified as mere contaminants.
| Item Type: | Thesis (Masters) |
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| Uncontrolled Keywords: | Bacteriological Profile ; Clinically Significant ; Coagulase Negative ; Staphylococci ; Virulence Factors. |
| Subjects: | MEDICAL > Microbiology |
| Depositing User: | Subramani R |
| Date Deposited: | 14 Aug 2017 05:56 |
| Last Modified: | 14 Aug 2017 05:56 |
| URI: | http://repository-tnmgrmu.ac.in/id/eprint/1443 |
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