Characterization of Colonizing Staphylococcus aureus Isolated from Surgical Wards' Patients in a Nigerian University Hospital

In contrast to developed countries, only limited data on the prevalence, resistance and clonal structure of Staphylococcus aureus are available for African countries. Since S. aureus carriage is a risk factor for postoperative wound infection, patients who had been hospitalized in surgical wards in a Nigerian University Teaching Hospital were screened for S. aureus carriage. All S. aureus isolates were genotyped (spa, agr) and assigned to multilocus sequence types (MLST). Species affiliation, methicillin-resistance, and the possession of pyrogenic toxin superantigens (PTSAg), exfoliative toxins (ETs) and Panton-Valentine Leukocidin (PVL) were analyzed. Of 192 patients screened, the S. aureus carrier rate was 31.8 % (n = 61). Of these isolates, 7 (11.5%) were methicillin-resistant (MRSA). The isolates comprised 24 spa types. The most frequent spa types were t064, t084, t311, and t1931, while the most prevalent MLST clonal complexes were CC5 and CC15. The most frequent PTSAg genes detected were seg/sei (41.0%) followed by seb (29.5%), sea (19.7%), seh (14.7%) and sec (11.5). The difference between the possession of classical and newly described PTSAg genes was not significant (63.9% versus 59.0% respectively; P = 0.602). PVL encoding genes were found in 39.3% isolates. All MRSA isolates were PVL negative, SCCmec types I and VI in MLST CC 5 and CC 30, respectively. Typing of the accessory gene regulator (agr) showed the following distribution: agr group 1 (n = 20), group II (n = 17), group III (n = 14) and group IV (n = 10). Compared to European data, enterotoxin gene seb and PVL-encoding genes were more prevalent in Nigerian methicillin-susceptible S. aureus isolates, which may therefore act as potential reservoir for PVL and PTSAg genes.     

Epidemiologic Typing of Methicillin-Resistant Staphylococcus aureus in Neonate Intensive Care Units Using Pulsed-Field Gel Electrophoresis

To elucidate the mode of dissemination of methicillin-resistant Staphylococcus aureus (MRSA) in neonate intensive care units (NICUs), a total of 223 isolates from 3 separate hospitals were investigated between 1994 and 1996 by a DNA fingerprinting technique with pulsed-field gel electrophoresis (PFGE). Exoprotein profiles of some strains were also examined using SDS-polyacrylamide gel-electrophoresis (SDS-PAGE) and the assessment of enzyme/toxin production such as coagulase, enterotoxin and TSST-1. Judging from the strain typing data from PFGE results and the epidemiological data, 2 different types of PFGE patterns (A and B) and their subtypes (A′, A″ and B′) were identified. The A type including A′ and A″ (comprising approximately 95% of the isolates) was markedly dominant. Only 5% of the isolates belonged to type B and subtype B′. On the other hand, MRSA isolated from adult patients admitted to the same hospital showed many different PFGE patterns. The results strongly suggested that some strain(s) with specific PFGE pattern(s) is prevalent in NICUs. Furthermore, isolates which expressed the same PFGE pattern did not always express the same SDS-PAGE pattern. There were some isolates with different abilities to produce coagulase, enterotoxin C and toxic-shock syndrome toxin (TSST)-1, and the abilities had no relation with a particular type of PFGE pattern. Therefore, a combination of PFGE analysis and biochemical analyses of coagulase, enterotoxin C and TSST-1 may provide us with more detailed information for the epidemiological study of MRSA in NICUs.     

A novel comprehensive analysis method for Staphylococcus aureus pathogenicity islands

Staphylococcus aureus pathogenicity islands (SaPIs) form a growing family of mobile genetic elements (MGEs) in Staphylococci. Horizontal genetic transfer by MGEs plays an important role in the evolution of S. aureus. Several SaPIs carry staphylococcal enterotoxin and SE‐like toxin genes. To comprehensively investigate the diversity of SaPIs, a series of primers corresponding to sequences flanking six SaPI insertion sites in S. aureus genome were designed and a long and accurate (LA)‐PCR analysis method established. LA‐PCR products of 13–17 kbp were observed in strains with seb, selk or selq genes. Restriction fragment length polymorphism (RFLP) analysis showed that the products have different RFLP characteristics than do previously described SaPIs; they were therefore predicted to include new SaPIs. Nucleotide sequencing analysis revealed seven novel SaPIs: seb‐harboring SaPIivm10, SaPishikawa11, SaPIivm60, SaPIno10 and SaPIhirosaki4, selk and selq‐harboring SaPIj11 and non‐superantigen‐harboring SaPIhhms2. These SaPIs have mosaic structures containing components of known SaPIs and other unknown genes. Strains carrying different SaPIs were found to have significantly different production of superantigen toxins. The present results show that the LA‐PCR approach can comprehensively identify SaPI diversity and is useful for investigating the evolution of S. aureus pathogenicity.     

Occurrence,antibiotic resistance and enteroxigenicity of Staphylococcus spp. in tonsils of slaughtered pigs in Greece

The aims of the present study were to examine the occurrence of Staphylococcus spp. in the tonsils of slaughtered pigs in a regional slaughterhouse in Greece, the antibiotic resistance of the Staphylococcus spp. isolates, and the enteroxigenicity of the S. aureus isolates. Staphylococcus spp. were isolated in 70 (48·61%) out of the total 144 tonsil samples. The predominant species was S. aureus in coagulase-positive staphylococci (CoPS), while the predominant species were Staphylococcus epidermidis and Staphylococcus saprophyticus in the coagulase-negative staphylococci (CoNS). Staphylococcus spp. isolates presented high antibiotic resistance frequencies to tetracycline (97·1%) or clindamycin (80·0%) and low antibiotic resistance frequencies to fusidic acid (14·3%). No methicillin-resistant S. aureus (MRSA) strains were identified, and all Staphylococcus spp. isolates were susceptible to vancomycin. Among the 26 S. aureus isolates, 21 (80·76%) possessed staphylococcal enterotoxin genes with seven different enterotoxin gene profiles. The predominant enterotoxin profile was seg, sei and sej with seven S. aureus isolates. The occurrence of multidrug resistant Staphylococcus spp. in pig tonsils indicate public health risk to pork consumers and handlers in developing antimicrobial resistance.     

Usefulness of Multiple-Locus VNTR Fingerprinting in detection of clonality of community- and hospital-acquired <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> isolates

Staphylococcus aureus has become a major source of hospital infections and the risk of colonisation and infection by community-acquired methicillin-resistant S. aureus (CA-MRSA) is increasingly higher. Because of the importance of S. aureus to public health, many molecular typing methods have been developed to determine its transmission routes and source of infection during epidemiological investigations. In this study we evaluated the usefulness of multiplex PCR based Multi-Locus VNTR Fingerprinting (MLVF) as the first step method for rapid differentiation of Croatian and Polish S. aureus isolates in hospital and community settings. This is a first report of the usefulness of MLVF in typing of hospital-acquired methicillin-sensitive S. aureus (HA-MSSA) and four CA-MRSA isolates. A total of 47 isolates of S. aureus recovered in Croatia in 2004 and in Poland in 2006 and 2007 were tested. The MLVF results were compared to those produced by other typing methods, such as Pulsed-Field Gel Electrophoresis (PFGE), Multi-Locus Sequence Typing (MLST) and spa typing. The MLVF analysis showed almost the same clonality results as the remaining typing methods although some differences were found. Epidemiological data about the relation among S. aureus isolates and the results produced by typing methods applied in the present study indicate that because of the advantages in ease and speed of Variable Number of Tandem Repeats (VNTR) procedure over PFGE, spa typing and MLST, MLVF can be used as a first screening method followed by additional typing.     

Adaptation of Staphylococcus aureus to ruminant and equine hosts involves SaPI‐carried variants of von Willebrand factor‐binding protein

Staphylococci adapt specifically to various animal hosts by genetically determined mechanisms that are not well understood. One such adaptation involves the ability to coagulate host plasma, by which strains isolated from ruminants or horses can be differentiated from closely related human strains. Here, we report first that this differential coagulation activity is due to animal‐specific alleles of the von Willebrand factor‐binding protein (vWbp) gene, vwb, and second that these vwb alleles are carried by highly mobile pathogenicity islands, SaPIs. Although all Staphylococcus aureus possess chromosomal vwb as well as coagulase (coa) genes, neither confers species‐specific coagulation activity; however, the SaPI‐coded vWbps possess a unique N‐terminal region specific for the activation of ruminant and equine prothrombin. vWbp‐encoding SaPIs are widely distributed among S. aureus strains infecting ruminant or equine hosts, and we have identified and characterized four of these, SaPIbov4, SaPIbov5, SaPIeq1 and SaPIov2, which encode vWbp^Sbo4, vWbp^Sbo5, vWbp^Seq1 and vWbp^Sov2 respectively. Moreover, the SaPI‐carried vwb genes are regulated differently from the chromosomal vwb genes of the same strains. We suggest that the SaPI‐encoded vWbps may represent an important host adaptation mechanism for S. aureus pathogenicity, and therefore that acquisition of vWbp‐encoding SaPIs may be determinative for animal specificity.     

Antimicrobial Resistance of Staphylococcus aureus Strains Acquired by Pig Farmers from Pigs

Carriage of animal-associated methicillin-resistant Staphylococcus aureus (MRSA) clonal complex 398 (CC398) is common among pig farmers. This study was conducted (i) to investigate whether pig farmers are colonized with pig-specific S. aureus genotypes other than CC398 and (ii) to survey antimicrobial resistance of S. aureus isolates from pigs and pig farmers. Forty-eight S. aureus isolates from pig farmers and veterinarians and 130 isolates from pigs collected in Western Switzerland were genotyped by spa typing and amplified fragment length polymorphism (AFLP). Antimicrobial resistance profiles were determined for representative sample of the isolates. The data obtained earlier on healthy S. aureus carriers without exposure to agriculture were used for comparison. The genotype composition of S. aureus isolates from pig farmers and veterinarians was similar to isolates from pigs with predominant AFLP clusters CC398, CC9, and CC49. The resistance to tetracycline and macrolides (clarithromycin) was common among the isolates from farmers and veterinarians (52 and 21%, respectively) and similar to resistance levels in isolates from pigs (39 and 23%, respectively). This was in contrast to isolates from persons without contact with agriculture, where no (0/128) isolates were resistant to tetracycline and 3% of the isolates were resistant to clarithromycin. MRSA CC398 was isolated from pigs (n = 11) and pig farmers (n = 5). These data imply that zoonotic transmission of multidrug-resistant S. aureus from pigs to farmers is frequent, and well-known MRSA transmission merely represents the tip of the iceberg for this phenomenon. We speculate that the relatively low frequency of MRSA isolation is related to lower antimicrobial use in Switzerland compared to, for example, the Netherlands.     

SCC<Emphasis Type="Italic">mec</Emphasis> Type IV,PVL-Negative,Methicillin-Resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> in Cystic Fibrosis Patients from Brazil

Twenty seven S. aureus isolates were obtained from cystic fibrosis (CF) patients at a tertiary care hospital in Brazil. Nineteen (70.4%) were methicillin-susceptible S. aureus (MSSA) and eight (29.6%) methicillin-resistant S. aureus (MRSA). Of the MRSA isolates, four had SCCmec type III and four had SCCmec type IV. PVL genes were not detected in any of the MSSA or MRSA isolates. New studies are necessary to evaluate the exact impact of these different MRSA clones in CF patients.     

Nasal Staphylococcus aureus and S. pseudintermedius carriage in healthy dogs and cats: a systematic review of their antibiotic resistance,virulence and genetic lineages of zoonotic relevance

The molecular ecology of Staphylococcus aureus, Staphylococcus pseudintermedius and their methicillin-resistant strains in healthy dogs and cats could serve as good models to understand the concept of bacterial zoonosis due to animal companionship. This study aims to provide insights into pooled prevalence, genetic lineages, virulence and antimicrobial resistance (AMR) among healthy dogs and cats. Original research and brief communication articles published from 2001 to 2021 that reported the nasal detection of S. aureus and S. pseudintermedius in healthy dogs and cats in the community, homes and outside veterinary clinics were examined and analysed. Forty-nine studies were eligible and included in this systematic review. The pooled prevalence of nasal carriage of S. aureus/methicillin-resistant S. aureus (MRSA) in healthy dogs and cats were 10.9% (95% CI: 10.1–11.9)/2.8% (95% CI: 2.4–3.2) and 3.2% (95% CI: 1.9–4.8)/0.5% (95% CI: 0.0–1.1), respectively. Conversely, the pooled prevalence of S. pseudintermedius/methicillin-resistant S. pseudintermedius (MRSP) in healthy dogs and cats were 18.3% (95% CI: 17.1–19.7)/3.1% (95% CI: 2.5–3.7) and 1.3% (95% CI: 0.6–2.4)/1.2% (95% CI: 0.6–2.3), respectively. Although highly diverse genetic lineages of S. aureus were detected in healthy dogs and cats, MSSA-CC1/CC5/CC22/CC45/CC121/CC398 and MRSA-CC5/CC93/CC22/CC30 were mostly reported in dogs; and MSSA-CC5/CC8/CC15/CC48 and MRSA-CC22/CC30/CC80 in cats. Of note, MSSA-CC398 isolates (spa-types t034 and t5883) were detected in dogs. Genetic lineages often associated with MSSP/MRSP were ST20/ST71, highlighting the frequent detection of the epidemic European MRSP-ST71 clone in dogs. S. aureus isolates carrying the luk-S/F-PV, tst, eta, etb and etd genes were seldomly detected in dogs, and luk-S/F-PV was the unique virulence factor reported in isolates of cats. S. pseudintermedius isolates harbouring the luk-S/F-I, seint and expA genes were frequently found, especially in dogs. High and diverse rates of AMR were noted, especially among MRSA/MRSP isolates. There is a need for additional studies on the molecular characterization of isolates from countries with under-studied nasal staphylococci isolates.     

The polyphenol (-)-epicatechin gallate disrupts the secretion of virulence-related proteins by Staphylococcus aureus

Aim: (?)‐Epicatechin gallate (ECg) modifies the morphology, cell wall architecture and β‐lactam antibiotic susceptibility of Staphylococcus aureus. As these effects result primarily from intercalation into the bacterial cytoplasmic membrane, the capacity of ECg to modulate the secretion of two key staphylococcal virulence factors, coagulase and α‐toxin, was examined. Methods and Results: Bioassays were used to determine coagulase and haemolysin activity in culture supernatants of a number of S. aureus isolates grown in the presence and absence of ECg; α‐toxin secretion was also evaluated by immunoblotting. Growth in ECg reduced the levels of activity of both proteins in culture supernatants; the effects could only be partly explained by ECg‐mediated inhibition of bioactivity and by induction of secreted proteases. Conclusion: ECg suppresses the secretion of coagulase and α‐toxin by clinical isolates of S. aureus. Significance and Impact of the Study: The observation that secretion of key components of staphylococcal virulence can be compromised by a naturally occurring polyphenol supports the notion that ECg and related compounds may have therapeutic utility for the control of infections that are currently difficult to treat due to the propensity of methicillin‐resistant S. aureus to accumulate antibiotic resistance genes.     

我国部分地区即食食品和蔬菜中金黄色葡萄球菌污染分布及耐药和基因分型情况

【目的】系统调查了我国15个代表性城市在即食食品(卤肉、烤肉、凉拌菜和巴氏奶)和蔬菜样品中金黄色葡萄球菌(Staphylococcus aureus)的污染分布情况,并对分离株进行耐药性分析及多位点序列分型(Multilocus sequence typing,MLST)研究,为食源性金黄色葡萄球菌的风险识别和分子溯源提供基础数据。【方法】依据GB 4789.10-2010对540份即食食品和蔬菜样品进行定性和最大可能数(Most probable number,MPN)分析;采用K-B纸片扩散法检测金黄色葡萄球菌分离株的耐药特征并通过PCR检测mecA基因;应用MLST方法确证金黄色葡萄球菌的主要ST型。【结果】结果发现9.3%(50/540)的样品中检出金黄色葡萄球菌,其中卤肉污染率最高,为16.3%(30/184),其次为烤肉(9.2%,6/65),蔬菜(6/150,4.0%)污染率最低。定量分析发现62.0%的阳性样品污染水平处于0.3–1.0 MPN/g,其中3份阳性样品污染水平≥110 MPN/g。对50株分离株进行24种抗生素耐药性检测,发现82.0%的分离株对氨苄西林和青霉素耐药,64.0%的分离株为多重耐药株。对mecA阳性分离株进行SCCmec分型,发现均为SCCmecⅣa。所有分离株进行MLST分型,共检出14种型别,其中ST3595和ST3847为新ST型。【结论】普遍的多重耐药性表明我国食源性金黄色葡萄球菌的耐药状况已较为严重,对消费者的安全健康存在潜在威胁。ST型与耐药存在一定的关联性,这为进一步了解该菌在我国食品中的流行趋势和风险评估提供了科学的数据支撑。     

Clonal distribution of bone sialoprotein-binding protein gene among Staphylococcus aureus isolates associated with bloodstream infections

Staphylococcus aureus is a leading cause of bloodstream infections (BSI) and diseases that may be caused by hematogenous spread. The staphylococcal adhesin, for which the association with the infections emerging as a complication of septicemia has been well documented, is a bone sialoprotein-binding protein (Bbp). The aim of the study was to assess the prevalence of a bbp gene in S. aureus bloodstream isolates associated with BSI and to investigate to what degree the distribution of this gene is linked to the clonality of the population. Spa typing, used in order to explore the genetic population structure of the isolates, yielded 29 types. Six spa clusters and seven singletons were identified. The most frequent was spa clonal complex CC021 associated with MLST CC30 (38 %). The bbp gene was found in 47 % of isolates. Almost all isolates (95 %) clustered in spa clonal complex CC021 were positive for this gene. All isolates carrying the bbp gene were sensitive to methicillin, and if clustered in the spa CC021, belonged to agr group III. Our study shows that Bbp is not strictly associated with BSI. However, one may conclude that for clonally related S. aureus strains most commonly causing BSI, the risk of Bbp-mediated complications of septicemia is expected to be higher than for other strains.     

Diverse Enterotoxin Gene Profiles among Clonal Complexes of Staphylococcus aureus Isolates from the Bronx,New York

Staphylococcal enterotoxins (SE) can cause toxin-mediated disease, and those that function as superantigens are implicated in the pathogenesis of allergic diseases. The prevalence of 19 enterotoxin genes was determined by PCR in clinical S. aureus strains derived from wounds (108) and blood (99). We performed spa typing and multilocus sequence typing (MLST) to determine clonal origin, and for selected strains staphylococcal enterotoxin B (SEB) production was measured by enzyme-linked immunosorbent assay. Strains carried a median of five SE genes. For most SE genes, the prevalence rates among methicillin-resistant and methicillin-sensitive S. aureus isolates, as well as wound- and blood-derived isolates, did not differ. At least one SE gene was detected in all except two S. aureus isolates (>99%). Complete egc clusters were found in only 11% of S. aureus isolates, whereas the combination of sed, sej, and ser was detected in 24% of clinical strains. S. aureus strains exhibited distinct combinations of SE genes, even if their pulsed-field gel electrophoresis and MLST patterns demonstrated clonality. USA300 strains also showed considerable variability in SE content, although they contained a lower number of SE genes (mean, 3). By contrast, SE content was unchanged in five pairs of serial isolates. SEB production by individual strains varied up to 200-fold, and even up to 15-fold in a pair of serial isolates. In conclusion, our results illustrate the genetic diversity of S. aureus strains with respect to enterotoxin genes and suggest that horizontal transfer of mobile genetic elements encoding virulence genes occurs frequently.As a commensal, Staphylococcus aureus colonizes the nasal mucosa of 20 to 40% of humans (54), and as a pathogen it causes pyogenic diseases and toxin-mediated diseases (38). S. aureus produces many different virulence factors, including enterotoxins (SEs), which can cause defined toxic shock syndromes (4). The characterization of some of these toxins led to the discovery of superantigens (41), which bind to major histocompatibility complex class II molecules and Vβ chains of T-cell receptors, resulting in the activation of large numbers of T cells (20 to 30%) and massive cytokine production (10, 18). These superantigen-induced “cytokine storms” are responsible for the toxic effects seen in staphylococcal entertoxin B (SEB)- and toxic shock syndrome toxin (TSST)-associated shock syndromes in S. aureus infections (13, 40, 47). To date, 19 SEs have been identified based on sequence homologies, and studies have reported enterotoxin genes in up to 80% of all S. aureus strains (4, 21). Although many new enterotoxins have been identified, i.e., seg ser and seu (33, 37, 44, 49), their precise functions have not been characterized yet. The majority of experimental work with SEs is still done with SEB, toxic shock syndrome toxin 1, and SEA (27, 31), because these toxins are commercially available. Most SEs are located on mobile elements in bacterial genomes such as plasmids or pathogenicity islands and can thus be easily transferred horizontally between strains (5, 34, 35). Certain SE genes are grouped together. For instance seg, sei, sem, sen, and seo are commonly found in a gene cluster (egc) on genomic island νSAβ (34), and sel and sek are often found together with seb or sec on S. aureus pathogenicity islands. Other staphylococcal superantigen genes are encoded on plasmids (sed, sej, and ser) or are linked to the antibiotic resistance cassette SCCmec (seh) (44, 55). Phage φ3 carries either sea (strain Mu50), sep (N315), or sea sek seq (MW2) (1, 29).Although a few clinical studies have attempted to correlate shock and outcome with the presence of certain SEs in patients with S. aureus infections (17, 28), the contribution of these toxins to outcome is still unclear. Recent papers have proposed the SEs are immunomodulators and that colonization with S. aureus strains that produce SEB may contribute to the pathogenesis of asthma, chronic rhinitis, and dermatitis (2, 36, 46, 48, 56). The superantigen function of SEs in supernatants of S. aureus cultures can be neutralized by serum of colonized patients (21, 23). With new data emerging implicating SEs in the pathogenesis of chronic allergic syndromes, production of monoclonal antibodies and or vaccine strategies targeting SEs may be considered (6, 24, 26, 30) in the future. It is therefore important to characterize the prevalence of SE genes in clinical S. aureus strains.In this study, we analyzed SE content in both methicillin-resistant S. aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) strains that were cultured from wounds (including USA300) and bloodstream infections of patients from a defined geographical area. In addition, SEB production was quantified by enzyme-linked immunosorbent assay (ELISA) in S. aureus strains carrying the seb gene, and spa typing confirmed clonal diversity among S. aureus isolates from different patients, as well as clonal stability in serial isolates, and multilocus sequence typing (MLST) done on a subset of less common spa types. We conclude that SE genes are abundant in S. aureus strains, albeit less abundant in USA300. SE content and combination are highly diverse and therefore more discriminatory than pulsed-field gel electrophoresis (PFGE) and MLST typing, albeit stable in serial isolates. Quantification of SEB production demonstrates that enterotoxin secretion can vary greatly among strains, even if they belong to the same S. aureus lineage. Given the complexities of SE prevalence, regulation, and possible function, we propose that the association of these toxins with chronic allergic diseases or outcome may be oversimplified at present. Precise characterizations of SE function and secretion patterns in individual S. aureus clones are warranted.     

Staphylococcal Enterotoxins B and C

Abstract

The staphylococcal enterotoxins (SEs) are a subgroup of related protein exotoxins in the pyrogenic toxin (PT) family produced by Staphylococcus aureus and Streptococcus pyogenes (1). Like other members of the PT family, the SEs are superantigens and elaborate a set of biological activities linked to their ability to stimulate cells of the immune system (2). These activities contribute to their ability to induce toxic shock syndrome, immunosuppression, and probably other diseases (3). However, as is evident from the fact that they are designated as enterotoxins, the SEs are distinguishable from other members of the PT family by their ability to induce gastroenteritis when ingested. Hence, they are the causative agents in staphylococcal food poisoning (SFP), a very common form of food-associated gastroenteritis in the United States and worldwide (4).     

驴源兽疫链球菌的分离鉴定及多位点序列分型分析

【目的】本研究采集了新疆地区驴腺疫病料,从样品中分离鉴定可疑病原菌并对其进行基因水平的分型与进化分析。【方法】对采集的新疆地区某驴场驴腺疫病驴颌下淋巴结拭子进行细菌分离培养,对2个分离株(HT111、HT321)进行染色、培养、生化试验、药敏试验,对其16S rRNA及SeM基因进行测序和进化分析,并通过PCR扩增7个管家基因,利用多位点序列分型(MLST)方法鉴定其分子分型。【结果】2个分离株均属马链球菌兽疫亚种,其中HT111对测试的13种抗生素中的3种(青霉素、克拉霉素和四环素)耐药,HT321对8种抗生素(阿莫西林、头孢呋辛、头孢噻呋、青霉素、克拉霉素、克林霉素、土霉素和四环素)耐药。序列分型发现了一种新的ST型为ST420 (HT321),分离株HT111为ST179型。【结论】本研究在新疆地区首次分离了驴源马链球菌兽疫亚种,并鉴定出一个新的ST型(ST420),为驴腺疫的流行病学提供了参考数据。     

Detection of methicillin-resistant <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> using double duplex real-time PCR and dye Syto 9

A screening method for methicillin-resistant Staphylococcus aureus (MRSA) using real-time polymerase chain reaction (PCR) and dye Syto 9 was developed and evaluated. The assay was based on the two duplex reactions run simultaneously. The detection reaction amplified staphylococcal cassette chromosome mec (SCCmec) right extremity sequences and S. aureus-specific 442-bp DNA (Sa442). The control reaction amplified S. aureus-specific nuclease gene nuc and a marker of methicillin resistance, mecA. The method was evaluated by analyzing 214 clinical S. aureus isolates yielding 98.7 % sensitivity, 100 % specificity, 100 % positive predictive value and 96.6 % negative predictive value for detection of MRSA. The detection limit was determined to be 15–80 genome copies per real-time PCR. It was able to discriminate between MRSA, methicillin resistant coagulase negative staphylococci and methicillin susceptible S. aureus (MSSA) isolates containing only small fragments of the right extremity of the SCCmec (MSSA revertants).     

Genotypes, exotoxin gene content, and antimicrobial resistance of Staphylococcus aureus strains recovered from foods and food handlers

Staphylococcal food poisoning, one of the most common food-borne diseases, results from ingestion of one or more staphylococcal enterotoxins (SEs) produced by Staphylococcus aureus in foods. In the present study, 64 S. aureus isolates recovered from foods and food handlers, associated or not associated with food-poisoning outbreaks in Spain, were investigated. They were assigned to 31 strains by spa typing, multilocus sequence typing (MLST), exotoxin gene content, and antimicrobial resistance. The strains belonged to 10 clonal complexes (CCs): CC5 (29.0%), CC30 (25.8%), CC45 (16.1%), CC8, CC15 (two strains each), CC1, CC22, CC25, CC59, and CC121 (one strain each). They contained hemolysin genes (90.3%); lukED (77.4%); exfoliatin genes eta, etd (6.5% each), and etb (3.2%); tst (25.8%); and the following enterotoxin or enterotoxin-like genes or clusters: sea (38.7%), seb (12.9%), sec (16.1%), sed-selj with or without ser (22.9%), selk-selq (6.5%), seh, sell, selp (9.7% each), egc1 (32.3%), and egc2 (48.4%). The number of se and sel genes ranged from zero to 12. All isolates carrying tst, and most isolates with genes encoding classical enterotoxins (SEA, SEB, SEC, and SED), expressed the corresponding toxin(s). Two CC5 isolates from hamburgers (spa type t002, sequence type 5 [ST5]; spa type t2173, ST5) were methicillin resistant and harbored staphylococcal cassette chromosome mec (SCCmec) IVd. Six (19.4%) were mupirocin resistant, and one (spa type t120, ST15) from a food handler carried mupA (MIC, 1,250 μg/ml). Resistance to ampicillin (blaZ) (61.3%), erythromycin (ermA-ermC or ermC) (25.8%), clindamycin (msrA-msrB or msrB) (16.1%), tetracycline (tetK) (3.2%), and amikacin-gentamicin-kanamycin-tobramycin (aphA with aacA plus aphD or aadD) (6.5%) was also observed. The presence of S. aureus strains with an important repertoire of virulence and resistance determinants in the food chain represents a potential health hazard for consumers and merits further observation.     

Frequent occurrence of multidrug‐resistant CC17 Enterococcus faecium among clinical isolates in Sweden

Aims: To screen for the globally spread cluster of Enterococcus faecium, clonal complex 17 (CC17) and characterize the genetic profile of Swedish clinical Ent. faecium isolates. Methods: A total of 203 consecutive isolates collected from 2004 to 2007 from patients with bacteraemia in Sweden. All isolates were genotyped using multiple‐locus variable‐number tandem repeat analysis (MLVA) and 20 isolates representing different MLVA types (MT) were chosen for multilocus sequence typing (MLST). Minimal inhibitory concentrations against clinically relevant antibiotics were determined with agar dilution. Presence of the virulence genes esp and hyl was investigated using PCR. Results: A total of 65% (n = 109) of all isolates belonged to MT‐1, and the second most common MLVA type was MT‐159 (13%, n = 21). MLST analysis confirmed the presence of CC17 during the entire study period. The number of isolates resistant to gentamicin and vancomycin, as well as the presence of hyl, increased significantly during the investigation period. Conclusions: The present study demonstrates that nosocomial infections caused by Ent. faecium CC17 are commonly occurring in Sweden. Significance and Impact of the Study: This is the first report of CC17 Ent. faecium in Sweden. The increase of antibiotic resistance and virulence indicates that these strains are further adapting to the hospital environment.     

The prevalence of Staphylococcus aureus and methicillin resistant Staphylococcus aureus in milk and dairy products in Riyadh,Saudi Arabia

In terms of life- menaced contagion, methicillin resistant Staphylococcus aureus (MRSA) is known to be one of which and it is truly notable in the contaminated food causing a community health anxiety. However, the occurrence of S. aureus and MRSA in diverse kinds of dairy products have been tested in this study. Samples from: raw milk (unpasteurized) from horse, goat, camel, and cow origins and unpacked cheese were checked for the recovered strains of such bacterium and MRSA. Wholly, MRSA isolates were verified for antimicrobial susceptibility and further characterized by mecA and staphylococcal cassette chromosome mec (SCCmec) typing. Also, Panton-Valentine Leukocidin (PVL), Staphylococcus aureus protein A (spa), and Staphylococcal enterotoxins (SEs) were also tested between all positive MRSA isolates in order to discover the virulence factors. Consequently, 70% of the 100 collected dairy products samples were contaminated by S. aureus bacteria and 72.9% of them were defined as MRSA. 9.8% of MRSA isolates contained mecA genes with SCCmec type II (80%) as the most common SCCmec type. Moreover, large number of MRSA isolates were identified as multidrug resistance and 28.6% of MRSA-mecA positive isolates were also carried vancomycin resistance genes (i.e., vanB). Too, spa gene was detected between 9.8% of MRSA isolates but PVL gene was not spotted at all. Additionally, the existing of SEs was variable between MRSA isolates and the most common type was SEH (51%). In general, our results confirmed that raw milk and unpacked cheese in the Kingdom of Saudi Arabia (Riyadh) is a potential vehicle for multidrug resistant MRSA transmission. It is a critical civic health menace and stresses, thus; the need of applying well cleanliness practices is essential.