Study of virulence factors in coagulase-negative staphylococci isolated from newborns

[Intraosseous vancomycin in total knee arthroplasty]

INTRODUCTION

intravenous antibiotic prophylaxis has significantly reduced the incidence of periprosthetic joint infection (PJI) in knee surgeries. However, for patients colonized with methicillin-resistant Staphylococcus aureus (MRSA) or those at risk of colonization, prophylaxis should include vancomycin. Intraosseous (IO) administration of vancomycin could enhance its effectiveness in total knee arthroplasty (TKA).

MATERIAL AND METHODS

a retrospective review was conducted, including 143 patients at risk of PJI scheduled for TKA who received IO vancomycin along with intravenous (IV) cefazolin, referred to as group I (GI), between May 2021 and December 2022. The occurrence of complications in the first three postoperative months was evaluated. Results were compared with 140 patients without risk factors who received standard IV prophylaxis, designated as group II (GII).

RESULTS

in GI, 500 mg of IO vancomycin was administered, injected into the proximal tibia, in addition to standard IV prophylaxis. In GII, patients received only IV cefazolin. The incidence of complications was 1.64% in GI and 1.4% in GII. The PJI rate at 90 postoperative days was 0.69% in GI and 0.71% in GII.

CONCLUSIONS

IO vancomycin administration, along with standard IV prophylaxis, provides a safe and effective alternative for patients at risk of MRSA colonization. This approach minimizes complications associated with IV vancomycin use and addresses logistical challenges of timely administration.

Virulence Potential and Antibiotic Susceptibility of S. aureus Strains Isolated from Food Handlers

Staphylococcus spp. are common members of the normal human flora. However, some Staphylococcus species are recognised as human pathogens due to the production of several virulence factors and enterotoxins that are particularly worrisome in food poisoning. Since many of Staphylococcal food poisoning outbreaks are typically associated with cross-contamination, the detection of S. aureus on food handlers was performed. Hand swabs from 167 food handlers were analysed for the presence of S. aureus. More than 11% of the samples were positive for S. aureus. All S. aureus strains were isolated and analysed for the presence of virulence and enterotoxin genes, namely, sea, seb, sec, sed, seg, sei, tsst-1 and pvl. The same strains were phenotypically characterised in terms of antibiotic susceptibility using the disc diffusion method and antimicrobial agents from 12 different classes. A low prevalence of antibiotic-resistant strains was found, with 55.6% of the strains being sensitive to all of the antimicrobial agents tested. However, a high prevalence of resistance to macrolides was found, with 44.4% of the strains showing resistance to erythromycin. At least one of the virulence or toxin genes was detected in 61.1% of the strains, and seg was the most prevalent toxin gene, being detected in 44.4% of the strains.

Staphylococcal Enterotoxin Genes in Coagulase-Negative Staphylococci-Stability, Expression, and Genomic Context

In the current study, we screened a collection of coagulase-negative staphylococci (CoNS) isolates for orthologues of staphylococcal enterotoxins (SEs) involved in S. aureus-related staphylococcal food poisoning (SFP). The amplicons corresponding to SEs were detected in S. chromogenes, S. epidermidis, S. haemolyticus, S. borealis, S. pasteuri, S. saprophyticus, S. vitulinus, S. warneri, and S. xylosus. All amplicons were sequenced and identified as parts of known S. aureus or S. epidermidis SE genes. Quantitative real-time PCR allowed determining the relative copy number of each SE amplicon. A significant portion of the amplicons of the sea, seb, sec, and seh genes occurred at low copy numbers. Only the amplicons of the sec gene identified in three isolates of S. epidermidis displayed relative copy numbers comparable to sec in the reference enterotoxigenic S. aureus and S. epidermidis strains. Consecutive passages in microbiological media of selected CoNS isolates carrying low copy numbers of sea, seb, sec, and seh genes resulted in a decrease of gene copy number. S. epidermidis isolates harbored a high copy number of sec, which remained stable over the passages. We demonstrated that enterotoxin genes may occur at highly variable copy numbers in CoNS. However, we could identify enterotoxin genes only in whole-genome sequences of CoNS carrying them in a stable form at high copy numbers. Only those enterotoxins were expressed at the protein level. Our results indicate that PCR-based detection of enterotoxin genes in CoNS should always require an additional control, like analysis of their presence in the bacterial genome. We also demonstrate S. epidermidis as a CoNS species harboring SE genes in a stable form at a specific chromosome site and expressing them as a protein.

Prevalence and distribution of resistance and enterotoxins/enterotoxin-like genes in different clinical isolates of coagulase-negative Staphylococcus

Background

Coagulase-negative staphylococcus (CoNS) is considered to be the major reservoirs for genes facilitating the evolution of S. aureus as a successful pathogen. The present study aimed to determine the occurrence of genes conferring resistance to fluoroquinolone, determining of the prevalence of insertion sequence elements IS256, IS257 and different superantigens (SAgs) among CoNS isolates obtained from various clinical sources.

Materials and methods

The current study conducted on a total of the 91 CoNS species recovered from clinical specimens in Hamadan hospitals in western Iran in 2017–2019. The antimicrobial susceptibility testing was performed using disk diffusion method and the presence of the IS256 and IS257, genes conferring resistance to fluoroquinolone and enterotoxins/enterotoxin-like encoding genes were investigated by polymerase chain reaction (PCR) method.

Results

Among genes encoding classic enterotoxins, sec was the most frequent which was carried by 48.4% of the 91 isolates, followed by seb in 27.5% of the isolates. None of the CoNS isolates was found to be positive to enterotoxin-like encoding genes. In 11(12%) of all isolates that were phenotypically resistant to levofloxacin, 9 isolates (81.8%) were positive for gyrB, 8 isolates (72.7%) were positive for gyrA, 8 isolates (72.7%) harbored grlB and 7 isolates (63.6%) were found to carry grlA. The IS256 and IS257 were identified in 31.8% and 74.7% of the isolates, respectively. The results of statistical analysis showed a significant association between the occurrence of staphylococcal enterotoxins (SEs) encoding genes and antimicrobial resistance.

Conclusion

Antimicrobial resistant determinants and SEs are co-present in clinical CoNS isolates that confer selective advantage for colonization and survival in hospital settings. The coexistence of insertion elements and antibiotic resistance indicate their role in pathogenesis and infectious diseases.

Review of Clinically and Epidemiologically Relevant Coagulase-Negative Staphylococci in Africa

Coagulase-negative staphylococci (CoNS) have engendered substantial interest in recent years as pathogenic causes of infections in both human and veterinary medicine, especially in the immunocompromised, critically ill, long-term hospitalized and in those harboring invasive medical devices such as catheters. They have been implicated in infections such as urinary tract infections, bloodstream infections, and invasive device-related infections, and are responsible for substantial economic losses in livestock production. The advancement of diagnostic techniques has increased our understanding of their molecular mechanisms of pathogenicity, even though distinguishing between innocuousness and pathogenicity is still challenging. The incidence of CoNS varied across the continent in humans and animals (mainly cattle), ranging from 6% to 68% in suspected human infections and from 3% to 61.7% in suspected animal infections, distributed across different geographic locations. Furthermore, there were varying antibiotic resistance patterns observed in CoNS isolates, with high methicillin resistance in some cases, leading to crossresistance against many antibiotics. Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus xylosus were most commonly reported in studies herein reviewed, while the enterotoxin C gene, atl E gene, ica gene, and hemolysin virulence factors were linked with enhanced pathogenicity. Advancement in identification and typing methods, including whole genome sequencing, virulence screening, and the assessment of the immune status of subjects in studies will help to thoroughly assess the true pathogenic potential of isolated CoNS species in developing countries. Careful antibiotic stewardship guidelines should be followed due to the ability of CoNS to develop multidrug resistance.

Identification of hemolysin encoding genes and their association with antimicrobial resistance pattern among clinical isolates of coagulase-negative Staphylococci

OBJECTIVE

Coagulase-negative staphylococci (CoNS) are as considered opportunistic pathogens which capable of producing several toxins, enzymes and resistance genes. The current study aimed to determine the occurrence of different hemolysins genes and patterns of antibiotic resistance among CoNS species.

RESULTS

The highest frequency of antibiotic resistance was observed against cefoxitin in 49 isolates (53.8%), and the lowest resistance was against novobiocin in 5 isolates (5.5%). None of the isolates was resistant to vancomycin. The prevalence of hla, hla_yidD, hld, and hlb genes was: 87.9%, 62.6%, 56%, and 47.3%, respectively. The hla/yidD and hld genes were detected in 69.4% of S. epidermidis and the hla gene in 94.6% of S. haemolyticus isolates; the hlb gene was detected in 53.1% of the S. epidermidis isolates. The mecA gene was identified in 50 (55%) of the CoNS isolates. In conclusion, the results of statistical analysis showed that the hld gene had a significant association with resistance to levofloxacin and erythromycin antibiotics, the hlb with clindamycin resistance and the hla/yidD with rifampicin and novobiocin resistance. The results of this study showed that there is a significant relationship between hemolysin encoding genes and antibiotic resistance patterns; therefore, detection of virulence factors associated with antibiotic resistance has become a significant issue of concern.

Evaluation of Biofilm Formation and Presence of Ica Genes in Staphylococcus epidermidis Clinical Isolates

Objectives

Biofilm formation is one of the important features of Staphylococcus epidermidis, particularly in nosocomial infections. We aimed to investigate the biofilm production by phenotypic methods and the presence of ica genes in S epidermidis.

Methods

A total of 41 S epidermidis isolates were recovered from different clinical specimens. Biofilm formation was evaluated by microtiter plate, tube method and Congo red agar method. The presence of icaA and icaD genes was investigated by PCR. Validity of methods (sensitivity and specificity), and metrics for test performance (positive/negative predictive value, and positive/negative likelihood ratio) were determined.

Results

By both microtiter plate and tube method, 53.6% of S epidermidis isolates were able to produce biofilm, whilst only 24.4% of isolates provided a biofilm phenotype on Congo red agar plates. icaA and icaD genes were found in 100% and 95.1% of isolates, respectively. Biofilm phenotypes accounted for 4.8% by microtiter plate assay, despite the absence of the ica gene. Congo red agar and PCR exhibited a lower sensitivity (18% and 45.5%, respectively) for identifying the biofilm phenotype in comparison to microtiter plate.

Conclusion

The microtiter plate method remains generally a better tool to screen biofilm production in S epidermidis. In addition, the ability of S epidermidis to form biofilm is not always dependent on the presence of ica genes, highlighting the importance of ica-independent mechanisms of biofilm formation. The use of reliable methods to specifically detect biofilms can be helpful to treat the patients affected by such problematic bacteria.

Staphylococcus simulans associated with endocarditis in broiler chickens

This report suggests a strong association between coagulase-negative Staphylococcus simulans and endocarditis in broiler chickens of a single flock. Clinical signs included increased mortality and lameness, and some dead chickens were found on their backs. Lesions included cauliflower-like, fibrinous vegetative lesions on the left atrioventricular valve; cream-coloured, necrotic foci of varying size in the liver; and necrosis of the femoral head. Histopathological examination of the heart revealed multifocal conglomerates of bacterial colonies attached to the valvular endocardium, threads of fibrin, and inflammatory cells with the presence of heterophils. S. simulans strains were first identified by API ID32, and then confirmed with Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry and by partial sequencing of the rpoB and dnaJ genes. These bacteria were resistant to methicillin but sensitive to vancomycin and characterized by slime production and protease activity.

Methicillin resistance and biofilm production of Staphylococcus epidermidis isolates from infectious and normal flora conjunctiva

PURPOSE

Coagulase-negative staphylococci have been reported to be the most frequent cause of bacterial postoperative endophthalmitis. Biofilm formation is the major virulence factor of Staphylococcus epidermidis and is often associated with methicillin resistance. This study aims at evaluating the presence of biofilm-producing and methicillin resistance genes (mecA) in S. epidermidis.

METHODS

S. epidermidis isolated from clinically infected sites (group 1) and from normal human conjunctiva (group 2) were studied. All the isolates were tested for their ability to produce biofilm by the conventional Christensen´s method and the presence of mecA by PCR using the 22-mer oligonucleotides as primers.

RESULTS

In total 20 isolates from group 1 and 22 from group 2 were studied. Biofilm and mecA were detected in 15 (75 %) and in 14 (70 %) in group 1 as compared to 8 (36.3 %) and 4 (18.2 %) in group 2 (p = 0.016). Simultaneously, biofilm production and presence of mecA genes were observed in 13/20 (65.0 %) in group 1, and 4/22 (18.2 %) in group 2 (p = 0.002). Multi-resistance was observed in 55 % in group 1 and 9 % in group 2 (p = 0.002); 57 % of the biofilm-producing strains was multi-resistant in contrast to none of the non-producing strains. In all multi-resistant strains, biofilm production was seen.

CONCLUSIONS

Biofilm formation capacity was widely distributed, particularly among mecA (+) S. epidermidis strains, which also displayed a high diversity of antibiotic resistance profiles.

Staphylococcus epidermidis and Staphylococcus haemolyticus: detection of biofilm genes and biofilm formation in blood culture isolates from patients in a Brazilian teaching hospital

Infections with coagulase-negative staphylococci are often related to biofilm formation. This study aimed to detect biofilm formation and biofilm-associated genes in blood culture isolates of Staphylococcus epidermidis and S. haemolyticus. Half (50.6%) of the 85 S. epidermidis isolates carried the icaAD genes and 15.3% the bhp gene, while these numbers were 42.9% and 0 for S. haemolyticus, respectively. According to the plate test, 30 S. epidermidis isolates were biofilm producers and 40% of them were strongly adherent, while only one (6%) of the 17 S. haemolyticus biofilm-producing isolates exhibited a strongly adherent biofilm. The concomitant presence of icaA and icaD was significantly associated with the plate and tube test results (P ≤ 0.0004). The higher frequency of icaA in S. epidermidis and of icaD in S. haemolyticus is correlated with the higher biofilm-producing capacity of the former since, in contrast to IcaD, IcaA activity is sufficient to produce small amounts of polysaccharide. Although this study emphasizes the importance of icaAD and bhp for biofilm formation in S. epidermidis, other mechanisms seem to be involved in S. haemolyticus.

Staphylococcus epidermidis as a cause of bacteremia

Staphylococcus epidermidis is a biofilm-producing commensal organism found ubiquitously on human skin and mucous membranes, as well as on animals and in the environment. Biofilm formation enables this organism to evade the host immune system. Colonization of percutaneous devices or implanted medical devices allows bacteria access to the bloodstream. Isolation of this organism from blood cultures may represent either contamination during the blood collection procedure or true bacteremia. S. epidermidis bloodstream infections may be indolent compared with other bacteria. Isolation of S. epidermidis from a blood culture may present a management quandary for clinicians. Over-treatment may lead to patient harm and increases in healthcare costs. There are numerous reports indicating the difficulty of predicting clinical infection in patients with positive blood cultures with this organism. No reliable phenotypic or genotypic algorithms currently exist to predict the pathogenicity of a S. epidermidis bloodstream infection. This review will discuss the latest advances in identification methods, global population structure, pathogenicity, biofilm formation, antimicrobial resistance and clinical significance of the detection of S. epidermidis in blood cultures. Previous studies that have attempted to discriminate between invasive and contaminating strains of S. epidermidis in blood cultures will be analyzed.

Staphylococcus epidermidis and Staphylococcus haemolyticus: Molecular Detection of Cytotoxin and Enterotoxin Genes

Although opportunistic pathogens, coagulase-negative staphylococci (CoNS), including Staphylococcus epidermidis and Staphylococcus haemolyticus, have long been regarded as avirulent organisms. The role of toxins in the development of infections caused by CoNS is still controversial. The objective of this study was to characterize the presence of enterotoxin and cytotoxin genes in S. epidermidis and S. haemolyticus isolates obtained from blood cultures. Cytotoxin genes were detected by PCR using novel species-specific primers. Among the 85 S. epidermidis and 84 S. haemolyticus isolates, 95.3% and 79.8%, respectively, carried at least one enterotoxin gene. The most frequent enterotoxin genes were sea (53.3%), seg (64.5%) and sei (67.5%). The seg gene was positively associated with S. epidermidis (p = 0.02), and this species was more toxigenic than S. haemolyticus. The hla/yidD gene was detected in 92.9% of S. epidermidis and the hla gene in 91.7% of S. haemolyticus isolates; hlb was detected in 92.9% of the S. epidermidis isolates and hld in 95.3%. Nosocomial Staphylococcus epidermidis and S. haemolyticus isolates exhibited a high toxigenic potential, mainly producing the non-classical enterotoxins seg and sei. The previously unreported detection of hla/yidD and hlb in S. epidermidis and S. haemolyticus using species-specific primers showed that these hemolysin genes differ between CoNS species and that they are highly frequent in blood culture isolates.

Virulence factors and antimicrobial resistance of coagulase-negative staphylococci isolated from drinking water

Little has been published about the occurrence, speciesidentification, andpathogenicpotentialofcoagulasenegative staphylococci (CoNS) present in drinking water. In this study, ten species were identified among 57 isolates of staphylococci from 756 samples of chlorinated drinking water taken from public distribution networks in the Slovak Republic. S. warneri (37%), S. haemolyticus (23%), and S. saprophyticus ssp. saprophyticus (14%) were identified most frequently. Isolates did not produce coagulase, DNase, or hyaluronidase; production of gelatinase and lecithinase was observed in 28 and 22 isolates, respectively. Genetically encoded ability for production of enterotoxin SED was revealed in two isolates. Among ten antibiotics tested, resistance to ampicillin (66.7%), penicillin (64.9%), and erythromycin (57.9%) were observed most frequently. Resistance to gentamicin, vancomycin, or clindamycin was not confirmed. Production of β-lactamase was observed in 64.9% of isolates. Fourty-two isolates were resistant to two or more antibiotics tested, and eight isolates showed multiresistance. The presence of mecA gene was confirmed in 8 isolates, while PBP2a was revealed in 7. Two isolates of S. epidermidis were identified as methicillin-resistant (MRSE). The results demonstrate that CoNS in chlorinated drinking water may possess virulence factors and show resistance to various antibiotics. Therefore, their pathogenic potential should not be ignored.

Phenotypic and genotypic characterization of canine pyoderma isolates of Staphylococcus pseudintermedius for biofilm formation

Biofilm-forming ability is increasingly being recognized as an important virulence factor in several Staphylococcus species. This study evaluated the biofilm-forming ability of sixty canine derived clinical isolates of S. pseudintermedius, using three phenotypic methods, microtiter plate test (MtP), Congo red agar method (CRA) and tube adherence test, and the presence and impact of biofilm-associated genes (icaA and icaD). The results showed that icaA and icaD genes were detected concomitantly in 55 (91.7%) of 60 isolates. A majority (88.3%) of the strains screened had matching results by the tube adherence test, MtP and PCR analysis. Better agreement (95%) was found between the PCR-based analysis and the CRA. Results of the icaA and icaD gene PCRs showed good agreement with CRA results, with a kappa of 0.7. Comparing the phenotypic methods, the statistical analysis showed that the agreement among the phenotypical tests using categorical data was generally good. Considering two classes (biofilm producer and biofilm non-producer), the percentage of matching results between the CRA method and the tube adherence test and between the CRA method and the MtP was 93.3%. A concordance of 100% was revealed between the MtP and the tube adherence test. The results indicate a high prevalence of the ica genes within S. pseudintermedius isolates, and their presence is associated with in vitro formation of a biofilm. A combination of phenotypic and genotypic tests is recommended for investigating biofilm formation in S. pseudintermedius.

Virulence, Speciation and Antibiotic Susceptibility of Ocular Coagualase Negative Staphylococci (CoNS)

BACKGROUND

Coagulase negative Staphylococci (CoNS) are common inhabitants of human skin and mucous membranes. With the emergence of these organisms as prominent pathogens in patients with ocular infections, investigation has intensified in an effort to identify important virulence factors and to inform new approaches to treatment and prevention.

AIM

To isolate CoNS from ocular specimens; to study the possible virulence factors; speciation of coagulase negative staphylococci (CoNS) which were isolated from ocular complications; antibiotic susceptibility testing of ocular CoNS.

MATERIALS AND METHODS

The specimens were collected from the target patients who attended the Microbiology Laboratory of a tertiary care eye hospital in Coimbatore, Tamilnadu state, India. The isolates were subjected to tube and slide coagulase tests for the identification of CoNS. All the isolates were subjected to screening for lipase and protease activities. Screening for other virulence factors viz., slime production on Congo red agar medium and haemagglutination assay with use of 96-well microtitre plates. These isolates were identified upto species level by performing biochemical tests such as phosphatase test, arginine test, maltose and trehalose fermentation tests and novobiocin sensitivity test. The isolates were subjected to antibiotic susceptibility studies, based on the revised standards of Clinical and Laboratory Standards Institutes (CLSI).

RESULTS

During the one year of study, among the total 260 individuals who were screened, 100 isolates of CoNS were obtained. Lipolytic activity was seen in all the isolates, whereas 38 isolates showed a positive result for protease. A total of 63 isolates showed slime production. Of 100 isolates, 30 isolates were analyzed for haemagglutination, where 4 isolates showed the capacity to agglutinate the erythrocytes. The results of the biochemical analysis revealed that of the 100 isolates of CoNS, 43% were Staphylococcus epidermidis. The other isolates were identified as S. xylosus (n=8), S. captis (n=16), S. haemolyticus (n=10), S. saccharolyticus (n=2), S. hominis (n=5), S. saprophyticus (n=6) and S. intermedius (n=1). On the other hand, 9 isolates were not identified. In the antibiotic susceptibility analysis, it was found that most of the isolates were sensitive to vancomycin, amikacin and linczolid and resistant to cefatoxime, oxacillin, bacitracin and nalidixic acid.

CONCLUSION

S. epidermidis was found to be predominant in causing the ocular complications. Slime production, heamagglutination, protease and lipase activities could be the putative virulence factors of CoNS. Antibiotic susceptibility patterns of CoNS against antibacterial agents revealed maximum resistance to beta lactam groups, and the resistance was found to be higher to oxacillin, and lowest to vancomycin.

Species identification and antimicrobial resistance of coagulase-negative staphylococci isolated from the meat of sea fish

Seventy-eight isolates of staphylococci obtained from the meat of Theragra chalcogramma, Scomber scombrus, and Clupea harengus were identified and tested in this study. 16S rDNA sequence specific for the genus Staphylococcus was detected in all isolates with the help of PCR method. All of 78 isolates were coagulase-negative, and DNAse activity was only confirmed in 4 of them. The following species of staphylococci were identified using MALDI-TOF mass spectrometry: S. warneri (52%), S. epidermidis (33%), S. haemolyticus (6.4%), S. pasteuri (3.8%), S. sciuri (1.2%), S. capitis (1.2%), and S. hominis (1.2%). Antimicrobial resistance to 7 antibiotics was determined in each isolate with the help of agar dilution method. In general, resistance against ampicillin was observed in majority of isolates (87%). On the contrary, the best sensitivity of CoNS was determined to gentamicin (96%). Only 1 S. warneri strain showed resistance to cefoxitin. Furthermore, 83% of staphylococcal isolates were simultaneously resistant to 2 or more antibiotics.

PRACTICAL APPLICATION

This study confirmed the need of monitoring antimicrobial resistance in coagulase-negative staphylococci not only in the meat of slaughter animals but also in retail marine fish. The results showed that MALDI-TOF mass spectrometry is useful, accurate, and rapid method for species identification of food pathogens including Staphylococcus spp.

Some Virulence Factors of Staphylococci Isolated From Wound and Skin Infections in Shahrekord, IR Iran

Background:

Staphylococci release a large number of enzymes. Some of these, such as coagulase, beta- lactamase, hemolysins and biofilms are considered indices of pathogenicity.

Objectives:

The aim of the current study was based on the isolation and identification of Staphylococcus aureus and coagulase negative Staphylococci (CNS) strains from various skin lesions and examining their biofilms, beta- lactamase, hemolysins production and antibiotic resistance pattern.

Materials and Methods:

Sixty one infected wounds and 39 skin infections samples were collected and examined. After the culture and identification, examination for production of hemolysins, beta- lactamase, biofilm and susceptibility toward 9 antimicrobials was performed.

Results:

Out of 75 isolated Staphylococci, sixty (80%) were biofilm producers. Two overall prevalence of 28.5% and 100% of ß-lactamase production were recorded for isolated S. aureus and CNS, respectively. Twenty out of 49 (40.8%), the same number of α- and β- hemolytic S. aureus, were isolated while six (12.24%) were ∂ -hemolysin producers. Twenty two of Twenty six (84.6%) isolates of CNS, were hemolysin producers that all were ∂ type. The S. aureus isolates from wound infections, show a high sensitivity pattern to all examined antibiotics, this sensitivity pattern for isolates from skin dermatitis is relatively low, though.

Conclusions:

High percentage of hemolysins, biofilm and beta lactamase production by isolated Staphylococci, suggests an important role of these virulence factors in the pathogenesis of isolated Staphylococci from dermatitis lesions. The S. aureus isolates from wound infections, show a high sensitivity pattern to all examined antibiotics. Only ciprofloxacin was found to be active against all isolates from dedermatitis lesions.

Enterotoxigenic potential of coagulase-negative staphylococci

Staphylococci are a worldwide cause of human and animal infections including life-threatening cases of bacteraemia, wound infections, pyogenic lesions, and mastitis. Enterotoxins produced by some staphylococcal species were recognized as causative agents of staphylococcal food poisoning (SFP), being also able to interrupt human and animal immune responses. Only enterotoxins produced by Staphylococcus aureus were as yet well characterized. Much less is known about enterotoxigenic potential of coagulase-negative species of genus Staphylococcus (CNS). The pathogenic role of CNS and their enterotoxigenicity in developing SFP has not been well established. Although it has been reported that enterotoxigenic CNS strains have been associated with human and animal infections and food poisoning, most of research lacked a deeper insight into structure of elements encoding CNS enterotoxins. Recent studies provided us with strong evidence for the presence and localization of enterotoxin-coding elements in CNS genomes and production of enterotoxins. Thus, the importance of pathogenic potential of CNS as a source of staphylococcal enterotoxins has been highlighted in human and animal infections as well as in food poisoning.

Risk factors for infection with coagulase-negative staphylococci in newborns from the neonatal unit of a brazilian university hospital

Background:

Coagulase-negative staphylococci (CoNS) are one of the most frequent causative agents of neonatal nosocomial infections, especially in premature and low-weight newborns. Risk factors for infection include extracellular polysaccharide production and consequent biofilm formation that permit adhesion to the smooth surface of catheters and other medical devices. The objective of this study was to identify CoNS strains isolated from 105 newborns admitted to the Neonatal Unit of our hospital, and to evaluate the association of biofilm production and host risk factors with the occurrence of infection.

Methods:

CoNS isolates were identified and classified as significant or contaminant based on clinical and laboratory data of the newborn medical records. Perinatal risk factors for infection, neonatal clinical evolution, and antibiotic treatment were analysed. In addition, the presence of genes (icaA, icaC and icaD) responsible for biofilm production in CoNS was investigated.

Results:

Among the 130 CoNS strains studied, 66 (50.8%) were classified as clinically significant and 64 (49.2%) as contaminant. There was no difference in the detection of biofilm-specific genes between CoNS strains isolated from newborns with (81.8%) and without infection (84.3%), although 11 (91.7%) of the 12 children whose death was related to CoNS were infected with strains that were positive for these genes. Forty-five (83.3%) of the 54 newborns infected with CoNS were premature and 33 (61.1%) had a birth weight ≤ 1,500 g. Most newborns infected with CoNS had been submitted to invasive procedures, including catheter use (85.2%), parenteral nutrition (61.1%), and mechanical ventilation (57.4%). S. epidermidis was the most frequently isolated species (81.5%) and was more related to infection (86.3%) than to contamination (76.5%).

Conclusion:

Most newborns infected with CoNS presented factors that contributed to the colonization and development of infection with these microorganisms, including a birth weight ≤ 1,500 g, catheter complications, use of a drain, and previous antibiotic treatment. The fact that most children who died of CoNS-related infection carried strains positive for biofilm-specific genes indicates the importance of this virulence factor for the outcome of staphylococcal infections.

An Enterotoxin-Bearing Pathogenicity Island in Staphylococcus epidermidis

Cocolonization of human mucosal surfaces causes frequent encounters between various staphylococcal species, creating opportunities for the horizontal acquisition of mobile genetic elements. The majority of Staphylococcus aureus toxins and virulence factors are encoded on S. aureus pathogenicity islands (SaPIs). Horizontal movement of SaPIs between S. aureus strains plays a role in the evolution of virulent clinical isolates. Although there have been reports of the production of toxic shock syndrome toxin 1 (TSST-1), enterotoxin, and other superantigens by coagulase-negative staphylococci, no associated pathogenicity islands have been found in the genome of Staphylococcus epidermidis, a generally less virulent relative of S. aureus. We show here the first evidence of a composite S. epidermidis pathogenicity island (SePI), the product of multiple insertions in the genome of a clinical isolate. The taxonomic placement of S. epidermidis strain FRI909 was confirmed by a number of biochemical tests and multilocus sequence typing. The genome sequence of this strain was analyzed for other unique gene clusters and their locations. This pathogenicity island encodes and expresses staphylococcal enterotoxin C3 (SEC3) and staphylococcal enterotoxin-like toxin L (SElL), as confirmed by quantitative reverse transcription-PCR (qRT-PCR) and immunoblotting. We present here an initial characterization of this novel pathogenicity island, and we establish that it is stable, expresses enterotoxins, and is not obviously transmissible by phage transduction. We also describe the genome sequence, excision, replication, and packaging of a novel bacteriophage in S. epidermidis FRI909, as well as attempts to mobilize the SePI element by this phage.

Comparison of methods for the detection of biofilm production in coagulase-negative staphylococci

BACKGROUND

The ability of biofilm formation seems to play an essential role in the virulence of coagulase-negative staphylococci (CNS). The most clearly characterized component of staphylococcal biofilms is the polysaccharide intercellular adhesin (PIA) encoded by the icaADBC operon. Biofilm production was studied in 80 coagulase-negative staphylococci (CNS) strains isolated from clinical specimens of newborns with infection hospitalized at the Neonatal Unit of the University Hospital, Faculty of Medicine of Botucatu, and in 20 isolates obtained from the nares of healthy individuals without signs of infection. The objective was to compare three phenotypic methods with the detection of the icaA, icaD and icaC genes by PCR.

FINDINGS

Among the 100 CNS isolates studied, 82% tested positive by PCR, 82% by the tube test, 81% by the TCP assay, and 73% by the CRA method. Using PCR as a reference, the tube test showed the best correlation with detection of the ica genes, presenting high sensitivity and specificity.

CONCLUSIONS

The tube adherence test can be indicated for the routine detection of biofilm production in CNS because of its easy application and low cost and because it guarantees reliable results with excellent sensitivity and specificity.

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

This study investigated slime production by coagulase-negative staphylococci (CNS) using the standard tube (ST), Congo red agar (CRA) plate and Christensen's tube (CT) methods, and compared the results with those of the crystal violet reaction (CVR) test. The potential correlation between slime production and antimicrobial resistance was also evaluated. In total, 205 CNS strains were isolated from biological samples: 92 (44.9%) were shown to produce slime by the ST method; 96 (46.8%) by the CRA plate method; 90 (43.9%) by the CT method; and 89 (43.4%) strains were CVR positive. Eighty-three (40.5%) CNS strains were positive for slime production by the ST, CRA and CT methods. The findings of the ST, CRA and CT test methods were consistent with each other but were not related to CVR positivity. Based on the ST method, rates of antibiotic resistance to several antimicrobial agents were higher in slime-positive strains than in slime-negative strains and, in some cases, this was statistically significant.

Toxigenicity in Staphylococcus aureus and Coagulase-Negative Staphylococci: Epidemiological and Molecular Aspects

Representatives of the Staphylococcus genus are the most common pathogens found in hospital environments, and they are etiological agents for a large variety of infections. Various virulence factors are responsible for the symptoms and severity of infections caused by Staphylococcus aureus. Among them are staphylococcal enterotoxins (SEs), which cause staphylococcal food poisoning, and toxic shock syndrome toxin-1 (TSST-1). Some reports indicate that TSST-1 and staphylococcal enterotoxins are also produced by coagulase-negative staphylococci (CNS). The present review aimed to discuss general aspects of staphylococcal toxins as well as the epidemiology, genetics and detection of toxins in Staphylococcus aureus and coagulase-negative staphylococci, since these microorganisms are becoming more and more frequent in nosocomial infections.