Evolution of slime production by coagulase-negative staphylococci and enterotoxigenic characteristics of Staphylococcus aureus strains isolated from various human clinical specimens

Abstract

The present study was designed to determine the slime production of coagulase-negative staphylococci (CoNS) and the enterotoxigenic properties of Staphylococcus aureus strains, and to evaluate the clinical importance of slime-producing CoNS and enterotoxigenic S. aureus strains isolated from various human clinical specimens. For this purpose, a total of 120 Staphylococcus strains were isolated and identified, and further characterized for their slime production and enterotoxigenicity. Of the clinical isolates, 55 (45.8 %) were found to be S. aureus, and the others (54.2 %) were identified as CoNS. Of the CoNS, 20 (16.7 %) were further identified as Staphylococcus hominis, 18 (15 %) as Staphylococcus epidermidis, six (5 %) as Staphylococcus xylosus, six (5 %) as Staphylococcus warneri, five (4.2 %) as Staphylococcus sciuri, four (3.3 %) as Staphylococcus haemolyticus, and two each (1.7 %) as Staphylococcus simulans, Staphylococcus capitis and Staphylococcus saprophyticus, respectively. Thirty-nine (60 %) of 65 CoNS were found to be slime producers. Slime production was observed in all CoNS, except S. capitis, mostly from blood (38.5 %), tracheal aspiration (20.5 %) and urine (12.8 %) specimens. In addition, of the 55 S. aureus isolates, 46 (83.6 %) were found to be enterotoxigenic, and of these S. aureus strains, 39 (84.7 %) were positive for staphylococcal enterotoxin (SE)A. The results of this study showed that the slime-producing CoNS were mostly found in clinical specimens of blood, tracheal aspirate and urine. SEA was the predominant enterotoxin type detected in S. aureus strains from human clinical specimens. INTRODUCTIONCoagulase-negative staphylococci (CoNS), inhabitants of skin and mucous membranes, are known to be opportunistic pathogens, causing bacterial keratitis and infections in immunocompromised hosts or in patients implanted with medical devices such as intravascular and peritoneal dialysis catheters, prosthetic heart valves and orthopaedic prostheses (Kogan et al., 2006). CoNS are characterized by an ability to colonize the surfaces of biomaterials by adhering in biofilm-structured communities of cells encased in a self-produced polymeric matrix, an amorphous slimy material that is loosely bound to staphylococcal cells. Slime is believed to make the micro-organisms more resistant to administered antibiotics and to host-defence mechanisms (Götz, 2002).Staphylococcus aureus strains are widespread in nature. They inhabit the skin, mucous membranes, anterior nares, eyes and gastrointestinal tract of asymptomatic individuals, where they can exist as resident or transient members of the normal flora without causing disease. However, some strains are responsible for many nosocomial infections, and in addition are the main causative agent of food intoxication by virtue of their variety of enterotoxins (Stephan et al., 2001 Recently, many studies have mainly been focused on the slime production of CoNS, but the results of these studies mostly do not reflect the importance of slime-producing CoNS from dif...

Characterization and Antibiotic Susceptibility Pattern of Coagulase Negative Staphylococci with Special Reference to Methicillin Resistance

“…However only few data are available on CONS infections with methicillin resistance from developing countries. [8] In the present study most of the isolates were from pus followed by blood and urine and it is well correlated with previously published studies [9,10,11,12,13] which had clearly shown that CONS were commonly isolated from pus, urine, blood & indwelling catheters. The most common organism identified in our study was S.epidermidis (65.5%) followed by S Saprophyticus (15%), S haemolyticus (10.83%) which was almost in par with the studies conducted by Singh S et al, [14] Adriana N et al, [ 9] Pal & Ayyageri.…”

“…In the present study 55.83% were slime producing organisms, S. epidermidis (82.09%) was the most common species in producing slime followed by S haemolyticus (8.96%) S. Sciuri (4.48%) which was almost similar to the results shown by few other authors. 2,11,12 Also Seetha KS et al, [2] & Boynukara B et al, [13] reported in their study that 16.07% of S. saprophyticus was producing slime, but interestingly in our study S. saprophyticus didn't produce the slime. On the other hand, it should also be considered that slime production may be affected by various factors, such as medium composition, the presence of carbohydrate, iron and CO 2 and oxidation.…”

“…The most common organism identified in our study was S.epidermidis (65.5%) followed by S Saprophyticus (15%), S haemolyticus (10.83%) which was almost in par with the studies conducted by Singh S et al, [14] Adriana N et al, [ 9] Pal & Ayyageri. [11] Where as Boynukara B et al [13] observed that S hominis the common species (30.8%) isolated followed by S. epidermidis (27.7%) & s xylosus (9.2%). The differences in the incidence of individual species in various publications can be attributed to the clinical samples received from different types and section of the hospitals as well as different methodology applied by various authors for specialization.…”

Differences between Two Clinical Staphylococcus capitis Subspecies as Revealed by Biofilm, Antibiotic Resistance, and Pulsed-Field Gel Electrophoresis Profiling

“…urealyticus with a selective advantage. Biofilms form a barrier around bacteria, protecting them from antibiotics and phagocytes and thus making the treatment of infections very difficult (4,30). However, given the likely value of biofilm formation in providing a positive selective advantage, the question remains as to why biofilm-negative antibiotic-susceptible S. capitis subsp.…”

Correlation of Slime Production Investigated via Three Different Methods in Coagulase-Negative Staphylococci with Crystal Violet Reaction and Antimicrobial Resistance

“…11,14,23,31 -40 In the study by Boynukara et al, 35 the rate of slimepositive CNS was 38.5% from blood samples, 20.5% from tracheal aspirates and 12.8% from urinary samples. Catalanotti et al 39 determined that slime-positive S. epidermidis and S. aureus strains showed more surface hydrophobic characteristics than slimenegative ones.…”