Emerging Challenges in Staphylococcus aureus Bloodstream Infections: Insights from Coagulase Typing, Toxin Genes, and Antibiotic Resistance Patterns

BackgroundThe number of studies regarding the incidence of multidrug resistant strains and distribution of genes encoding virulence factors, which have colonized the post-Soviet states, is considerably limited. The aim of the study was (1) to assess the Staphylococcus (S.) aureus nasal carriage rate, including Methicillin Resistant S. aureus (MRSA) strains in adult Ukrainian population, (2) to determine antibiotic resistant pattern and (3) the occurrence of Panton Valentine Leukocidine (PVL)-, Fibronectin-Binding Protein A (FnBPA)- and Exfoliative Toxin (ET)-encoding genes.MethodsNasal samples for S. aureus culture were obtained from 245 adults. The susceptibility pattern for several classes of antibiotics was determined by disk diffusion method according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. The virulence factor encoding genes, mecA, lukS-lukF, eta, etb, etd, fnbA, were detected by Polymerase Chain Reaction (PCR).ResultsThe S. aureus nasal carriage rate was 40%. The prevalence of nasal MRSA carriage in adults was 3.7%. LukS-lukF genes were detected in over 58% of the strains. ET-encoding genes were detected in over 39% of the strains and the most prevalent was etd. The fnbA gene was detected in over 59% of the strains. All MRSA isolates tested were positive for the mecA gene. LukS-lukF genes and the etd gene were commonly co-present in MRSA, while lukS-lukF genes and the fnbA gene were commonly co-present in Methicillin Sensitive S. aureus (MSSA) isolates. No significant difference was detected between the occurrence of lukS-lukF genes (P > 0.05) and the etd gene (P > 0.05) when comparing MRSA and MSSA. The occurrence of the fnbA gene was significantly more frequent in MSSA strains (P < 0.05).ConclusionsIn Ukraine, S. aureus is a common cause of infection. The prevalence of S. aureus nasal carriage in our cohort of patients from Ukraine was 40.4%. We found that 9.1% of the strains were classified as MRSA and all MRSA isolates tested positive for the mecA gene. We also observed a high prevalence of PVL- and ET- encoding genes among S. aureus nasal carriage strains. A systematic surveillance system can help prevent transmission and spread of drug resistant toxin producing S. aureus strains.

BACKGROUND. Nasal carriage of Staphylococcus aureus among hospital personnel is a common cause of hospital acquired infections. Emergence of drug resistant strains especially methicillin resistant S. aureus (MRSA) is a serious problem in hospital environment. Therefore, the aim of this study was to determine the prevalence of nasal carriage of Staphylococcus aureus its antibiotic susceptibility among healthcare workers (HCWs) in Ukraine.&#x0D; METHODS. This cross-sectional study was conducted from January to December 2017. The study included medical workers from 19 hospitals in different Ukrainian regions. Nasal swabs were taken from 755 randomly selected HCWs. The mean age of participants was 32.41 ± 8.29 years (range 19—74 years) with a male-to- female ratio of 0.47. The isolates were identified as S. aureus based on morphology, Gram stain, catalase test, coagulase test, and mannitol salt agar fermentation. The sensitivity patterns of S. aureus strains were determined by disk diffusion method (Kirby — Bauer). The panel of antibiotics used in sensitivity tests included: penicillin, oxacillin, cefoxitin, amoxicillin/clavulanic acid, gentamicin, tobramicin, ciprofloxacin, levofloxacin, moxifloxacin, mupirocin, nitrofurantoin, vancomycin, teicoplanin, fosfomycin, clindamycin, erythromycin, rifampicin, linezolid, tetracycline, tigecycline, trimethoprim/sulphamethoxazole, and fusidic acid. Interpretative criteria were those suggested by the CLSI (Clinical and Laboratory Standards Institute). MRSA were confirmed by detection of the mecA gene by polymerase chain reaction.&#x0D; RESULTS. Nasal screening identified 31.1 % (235/755) S. aureus carriers. Of the 235 nasal carriers of S. aureus, 4 % (196/755) carried MSSA (methicillin-sensitive S. aureus) and 39/755 (16.6 %) carried MRSA. The frequency of MRSA and MSSA carriage also varied according to the department/ward. The highest prevalence of nasal carriage of MRSA was in the surgical wards. The staff of the general, pediatric, cardiovascular, neuro and orthopedic surgery wards together with the emergency department accounted for 56.4 % of all MRSA carriers. There was no significant difference between the sexes (p = 0.247), age (p = 0.817), and years of healthcare service (p = 0.15) with regard to the nasal carriage of MRSA and MSSA. In univariate analysis we divided the hospital departments into: emergency, internal medicine, pediatrics, ICUs, surgery, and non-medical units and found no significant difference between MSSA and MRSA carriers (p = 0.224). In the multivariate analysis, the occupation «nurse» was independently associated with MRSA carriage (p = 0.012, odds ratio 3.6, 95 % confidence interval 1.3—9.7). All the S. aureus isolates recovered from nasal carriers, were susceptible to linezolid, tigecycline, vancomycin, teicoplanin, and mupirocin. Susceptibility to the other antimicrobials was also on a high level: 98.3 % of strains were found susceptible to trimethoprim/sulphamethoxazole, 96.2 % — to nitrofurantoin, 95.3 % — to fusidic acid, 92.3 % — to fosfomicin, 88.5 % — to amoxicillin/clavulanic acid, 87.2 % — to tobramycin, 86.8 % — to clindamycin. Resistance to oxacyllin came up to 16.6 %.&#x0D; CONCLUSIONS. Nasal carriage of S. aureus appears to play a key role in the epidemiology and pathogenesis of infection. HCWs who are at interface between the hospital and the community may serve as agents of cross contamination of hospital acquired and community acquired MRSA. It is of importance to follow the evolution of resistance to antibiotics in this species, especially to β-lactams.

Molecular characterization of Staphylococcus aureus strains isolated from hospitalized patients based on coagulase gene polymorphism analysis: High frequency of vancomycin-intermediate S. aureus and the emergence of coagulase type II in Iran

Methicillin-resistant Staphylococcus aureus bacteremia in neonatal intensive care units: genotyping analysis and case-control study.

This study gives the reported prevalence of cockroaches and the medical importance of theinsects due to the transmission of nosocomial infections. Besides, one of the major reasons of hospital and community infections all over the world is methicillin-resistant Staphylococcus aureus(MRSA). The aim of this study was to determine inset the hospital cockroaches as the main factor for MRSA infections transmission and also determine antibiogram pattern MRSA. In this study, going to hospitals, over 100 cockroaches were collected using hand and Telesticky methods and enriching the intended strain on a specific medium. Then was a designed primer for mecA gene and amplification in polymerase chain reaction (PCR). The disk diffusion method was used for specifying resistance patterns in line with guidelines of Clinical and Laboratory Standards Institute(CLSI). Results showed that a total of 44 (62.86%) of 100 samples were contaminated with S. aureus isolated from cockroaches hospitals, also with molecular sieve of PCR, an addition of 8 (19.56%) of the strain contained the mecA gene. The overall resistance of isolated MRSA strains to antimicrobial agents was 8 (100%) for methicillin, 7 (87.5%) for cefixime and 6 (75%) for vancomycin, which had more resistance, respectively. This study implies that cockroaches, as a potential factor in transmission of MRSA function and medical resistance pattern of MRSA are different in different areas. Key words: Antibiogram, resistance, methicillin-resistant Staphylococcus aureus (MRSA), Chaharmahal-va-Bakhtiari hospitals, polymerase chain reaction (PCR).

Pediatric sepsis due to Staphylococcus aureus (S. aureus) is associated with high morbidity and mortality. Accessory-Gene-Regulator (agr) has a role in the pathogenesis of S. aureus through controlling and regulating the expression of virulence genes. Therefore, the aim of the present study was to investigate the prevalence of genotypes of the agr system in S. aureus isolated from children with sepsis and to assess their relationship to biofilm formation and antibiotic resistance. The study was a retrograde cross-sectional study that included 131 children with health care associated sepsis due to S. aureus. The isolated S. aureus was investigated for their ability to form biofilm by microplate method, antibiotic susceptibility pattern by disc diffusion method, and molecular determination of agr genotypes by polymerase chain reaction (PCR). Methicillin resistant S. aureus (MRSA) was defined by resistance to cefoxitin antibiotic disc in 70 (53.4%) of the isolates and biofilm formation was positive in 67 (58%) of the isolates. Molecular study of the agr genes revealed that 54 (41.2%), 40 (30.5%), 27 (20.6%), and 10 (7.5%) of the studied isolates had agr I, agr II, agr III, and agr IV, respectively. In comparison between MRSA and methicillin sensitive S. aureus (MSSA), there was a signif-icant increase in biofilm formation among MRSA (65.7%, p = 0.01) compared to MSSA (34.3%) and an increase in agr genotype I among MRSA (68.6%, p = 0.001) compared to agr I in MSSA (9.8%). There was a significant association with the presence of a central venous catheter (51.4%, p = 0.001) and urinary tract catheter (81.4%, p = 0.001) in children with MRSA compared to children with MSSA (21.3%, OR = 3.9, 95% CI = 1.8 - 8.5 and 36.1%, OR = 7.8, 95% CI 3.5 - 17.3, respectively). There was an increase in the biofilm formation among S. aureus isolated from pediatric patients with sepsis with a significant increase in MRSA. The agr group I was the main agr gene among the isolated S. aureus. Moreover, agr I was the predominant gene in MRSA isolates and was significantly associated with biofilm formation.

Staphylococcus aureus has long been recognised as an important pathogen. Originally sensitive to penicillins, including methicillin, the introduction of penicillin into clinical practice led to resistance and methicillin resistant S. aureus (MRSA) was first described in 1961. Not only is S. aureus a pathogen, but it commonly colonises skin and mucous membranes. The anterior nares are the most consistent area from which the organism can be isolated. Carriage rates of methicillin sensitive S. aureus (MSSA) vary between 25% and 33% and there is no significant difference between the general population and healthcare workers in this respect. Carriage of MRSA, however, is more common in healthcare workers than in the general population and general practitioners are just as likely as hospital workers to be carriers. Persistent carriage of MRSA occurs in 4.6% of healthcare workers [1]. With regard to carriage of S. aureus, four patterns occur. Some individuals always carry the organism (persistent carriers), some carry the organism intermittently (intermittent carriers) and some never carry the organism (non-carriers) [2]. Transient carriage is recognised in persons who carry the organism for a short period after contact with another person who is either infected or is carrying S. aureus. Transient carriage is common; up to 50% of nurses will have positive nasal swabs at the end of a shift when they have been caring for a patient with MRSA but most will be negative when swabbed at the beginning of the next shift [3]. S. aureus infection is common in hospital and S. aureus carriage is a risk factor for development of infection. In the surgical population there is a fourfold increased risk of S. aureus bacteraemia in carriers compared to non-carriers [4], and at least 80% of S. aureus infections are caused by S. aureus cells that were present on the skin or mucous membranes before hospital admission (endogenous infection) [5]. This leaves approximately 20% where the S. aureus has been acquired from elsewhere (exogenous infection) and the possibility of transfer from a healthcare worker in this group is very real. Carriage of MRSA is more likely than that of MSSA to lead to clinical infection, including wound, lower respiratory tract and catheter-related blood stream infections [6], and the risk of death is greater with MRSA bacteraemia compared with MSSA bacteraemia [7]. These are two of the reasons that there is a current focus on MRSA rather than MSSA. There are two main ways by which anaesthetists can increase the risk of MRSA bacteraemia in their patients – poor aseptic technique and poor hand hygiene – but there are a number of other factors that impact upon the transmission of MRSA, with which anaesthetists may be less familiar. Although hand hygiene is the public face of prevention [8, 9], the wide range of procedures and processes that have been identified as important means that MRSA blood stream infection has become a quality marker used by the UK Department of Health to set targets, rank hospitals and permit application for Foundation status. Mandatory reporting of MRSA blood stream infection to the Health Protection Agency began in 2001 and most hospitals now undertake a root cause analysis following every MRSA bacteraemia. Although post-operative MRSA bacteraemia only accounts for 50% of all cases, many of the surgical patients who develop MRSA bacteraemia have undergone major surgery and as such have had a number of intravascular catheters placed in the peri-operative period. Poor technique, imperfect compliance with guidelines or inadequate documentation of the line placement procedure is often quoted in a root cause analysis as a possible cause of infection. Regardless of the complexity of the operation, the anaesthetist is identified as a person possibly responsible for the MRSA infection. So what are the factors that can impact on the transmission and therefore the chance of MRSA bacteraemia occurring? A number of factors have been identified as important [10] and most of these are relevant to anaesthetists. Healthcare workers, besides being clean and competent, should be present in sufficient numbers to enable infection control procedures to be completed correctly. This last point is particularly relevant to anaesthetists. It is not possible to administer intravenous drugs with one hand and maintain the airway with the other whilst following correct infection control procedures. The correct process would be for two separate people to carry out the two separate procedures, a luxury that few of us experience. Care delivery procedures can be influenced both by the actions that we take and the decisions that we make. Hand hygiene and the use of personal protective equipment should be routine [11] and aseptic technique should be used correctly whenever appropriate. How many anaesthetists have been taught to scrub properly or to don gloves using a no-touch technique? This is not yet considered a core competency by the Royal College of Anaesthetists. Decisions that we make that impact upon the transmission of MRSA include avoiding the use of invasive devices and removing all devices as soon as possible. Equipment that is used must be able to be decontaminated between patients if it is not disposable. The line between disposable and non-disposable equipment is sometimes vague. It is obvious that the transoesophageal echocardiography machine used in theatre is not disposable but less obvious is an accepted method of decontamination between patients. A number of the ‘disposable’ items that we use are disposed of whilst trying to balance cost and risk. The disposable bag on the anaesthetic machine is used by the same hand that maintains the airway of the unconscious patient and yet it is frequently changed only at the end of the day or week. Effective decontamination of this type of item is extremely difficult. Administrative processes have been developed over the last few years that are designed to have an impact on the transmission of MRSA. These include antibiotic stewardship, surveillance and screening of patients and staff. Surveillance is now undertaken routinely as part of all hospitals’ infection control programmes, with hospitals obliged to publish the number of MRSA bacteraemias that occur every month. Although some anaesthetists fit nicely into groups that can take an active part in reviewing surveillance data and therefore work to reduce the incidence of MRSA (neuro-anaesthetists may review the data from neurosurgical and neuro-intensive care patients etc), many anaesthetists do not fit neatly into these groups and view the surveillance data with little more than passing interest. Screening patients for MRSA is not a control measure in itself but the efficacy of screening depends upon the other interventions that occur following the result. This will include decolonisation or isolation. Recommendations for screening have changed over the last 15 years from not being recommended, to being recommended for high risk surgery, to being recommended for virtually all patients [12], and screening before admission to hospital (or on admission when admitted as an emergency) has been mandatory for all patients in the UK since April 2009 [13]. How this intervention impacts upon the prevalence of MRSA bacteraemia remains to be seen, but there is already evidence that screening higher risk patients significantly reduces prevalence. The approach to positive MRSA carriage in patients will vary according to the urgency of admission and local policy, but elective patients now receive decolonisation treatment if found to be positive when screened. The controversy surrounding routine screening of patients has now disappeared and it has been replaced by a controversy about the screening of healthcare workers. Although the 2006 guidelines for MRSA in healthcare facilities did not recommend routinely screening staff, the times they are a-changing and the public is beginning to demand this. Sir Richard Branson is now Vice-President of the Patient’s Association and he has stated that he wants to see the immediate implementation of routine screening for MRSA in healthcare workers. So why should it be done, how should it be done, how should MRSA carriage be treated in healthcare workers and what are the implications for the 4.6% of us who are carriers of MRSA? There is a clear association between carriage of MRSA by healthcare workers and MRSA infection in patients, but it is unclear whether the healthcare worker is the ‘source, vector or victim’ of the problem [1]. The 2006 guidelines recommended that investigation or screening of staff should be restricted to those associated with an outbreak of MRSA, possibly starting with staff who had skin lesions eg eczema, but the argument for more general screening is supported by the correlation between colonisation rate and the prevalence of endemic MRSA. The likely source of MRSA will change markedly from now on with the introduction of universal screening for patients, changing the odds that a single case of MRSA bacteraemia originates from a healthcare worker. When screening (of staff) is done, it should be performed at the beginning of the day away from the clinical environment. This will prevent inappropriate identification of transient carriers with unnecessary treatment and exclusion from work. Swabs should be moistened with sterile saline before swabbing to enhance the likelihood of detection. Although there is no agreement on the sites to be swabbed, this should certainly include the anterior nares and usually includes the groin or axilla. Treatment of a MRSA positive healthcare worker should be multi-faceted. Exclusion from the clinical workplace for 48 h following the positive finding and initiation of treatment are recommended. Return to clinical work should be determined by a risk analysis. Clearly anaesthetists fall into a high-risk group and return to practice is generally delayed until negative swabs have been obtained 48 h after treatment has been completed. Treatment generally lasts 5 days and includes showering and hair washing with chlorhexidine liquid and mupiricin ointment applied to the anterior nares. Although the goal of treatment in the patient population is decolonisation, in healthcare workers, the aim is eradication. Eradication is continued decolonisation, with a negative screen at either 6 or 12 months. The difference between the two is due to treatment failure or recurrence. Treatment failure occurs in 9% of healthcare workers, some of which may be due to treatment compliance, but recurrence in healthcare workers who were initially decolonised has been estimated to occur in approximately 25% by 1 month [14]. So what are the implications for anaesthetists? It is not yet clear that testing for all or all relevant healthcare workers will be introduced, but there are a number of advantages if it is. It will probably reduce the prevalence in patients where MRSA is endemic and decrease the incidence where MRSA is sporadic. It will reduce the chance of MRSA infection in healthcare workers and will undoubtedly improve patient and public confidence. It would add to the existing training methods in infection control by a process of ‘vivid experience’ [15]. Balancing the advantages, there are a number of disadvantages or other considerations. First, careful consideration needs to be made of the ethics of mass screening [16] and whether the imperative that benefit should outweigh likely harm has been met. The complexities of individual vs population benefit must also be considered. Screening staff would provide false reassurance for non-colonised or non-identified healthcare workers, it would disrupt patient care and it would threaten staff morale. The feelings of guilt of MRSA positive healthcare workers towards patients and close contacts would need to be addressed. The issues of stigmatisation, anonymity, failure of decolonisation and reporting of long-term carriers under the ‘Reporting of Injuries, Diseases and Dangerous Occurrences Regulations’ (RIDDOR, 1995) as a mechanism of providing legal protection all need consideration. Although public pressure can be very powerful it is important to have a logical approach to screening staff before its introduction.

Background and Aims: Based on the results, Staphylococcus aureus is one of the serious infectious agents found in community and hospitals with remarkable potential for high morbidity and mortality around the globe. The present study was carried out for molecular investigation of methicillinresistant Staphylococcus aureus strains and Staphylococcal Chromosomal Cassette mec (SCCmec) phenotypes isolated from the intensive care unit in Hazrat Fatemeh Zahra hospital of Isfahan. Materials and Methods: A total of 76 clinical wound samples were collected from Hazrat Fatemeh Zahra Hospital in Isfahan and evaluated by polymerase chain reaction (PCR) methods. The Methicillin resistance Staphylococcus aureus (MRSA) screening was performed by genotypic and phenotypic methods; also antibiotic resistance pattern was determined by using the disk diffusion method and related genes by PCR. Results: Totally, 53 (69.7%) out of 76 clinical samples were positive for MRSA. Of the 76 MRSA strains, 39 (63.51%) were PVL positive (51.3%). The most commonly infected samples were collected from wounds (40.8%). The most commonly detected antibiotic resistance genes were mecA (89.61%), tetK (88.23%), tetM (49.15%) and msrA (46.93%). Resultantly, it was shown that MRSA has the highest level of resistance against methicillin (98%), penicillin (97.24%), tetracycline (89.64%). It was also revealed that the most commonly detected SCCmec types in the MRSA strains are types II (14.53%) and III (16.82%). Conclusions: In summary, this paper argues that the orderly surveillance of hospital-associated infections and initial management and supervision of the antibiotic resistance patterns are required to control the prevalence of MRSA.

Background: Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSIs) are common in hospitals and nursing homes. Infection prevention efforts reduced MRSA BSI in hospitals but the trend in nursing homes is not well described. In addition, the contribution of methicillin sensitive S. aureus (MSSA) to the total burden of invasive S. aureus (iSA) in nursing homes remains unknown. Methods: As part of the CDC Emerging Infections Program, we conduct population-based surveillance for iSA infections in Monroe County, New York. Case patients were county residents with S. aureus isolated from a sterile site. Our analysis was limited to data from 2009–2018 for MRSA and 2015–2018 for MSSA and to cases classified as hospital-onset (HO, positive culture ≥3 calendar days after admission) or nursing home-onset (NHO, positive culture in nursing homes or within 3 days of hospital admission from a nursing home). Risk factors for iSA BSI in nursing homes were compared using the χ2 and Student t tests in SAS version 9.4 software. Results: During 2009–2014, 664 MRSA cases occurred and 427 (64%) were BSIs. Of these, 228 (53%) were NHO and 199 (47%) were HO. The BSI incidence per 100,000 population of NHO cases declined from 7.9 in 2009 to 2.8 in 2014, mirroring the decline in HO incidence from 8.7 in 2009 to 3.1 in 2014 (Fig. 1). During 2015–2018, 203 MRSA cases (163 BSIs, 80%) and 235 MSSA cases (163 BSIs, 69%) occurred. Of the 163 MRSA BSIs, 94 (58%) were NHO and 69 (42%) were HO, whereas of the 235 MSSA BSIs, only 56 (34%) were NHO and 107 (66%) were HO. MRSA BSI incidence per 100,000 population in both settings plateaued during 2015–2018 (Fig. 1) and MSSA NHO BSI incidence was lower than HO (1.9 NHO vs 3.6 HO). The total iSA BSI incidence was similar in both settings (5.9 vs 5.0 per 100,000 population in HO and NHO, respectively). NHO MSSA and MRSA cases have similar risk factors for BSI; 45 (30%) had decubitus ulcers, 34 (23%) were on chronic dialysis, 41 (27%) had a CVC in place within 2 days of BSI onset, and 63% had prior healthcare exposures. Most of these developed within 4 weeks of hospital discharge (Fig. 2). Conclusions: The incidence of MRSA BSI in nursing homes has declined since 2009 but plateaued starting in 2015. Compared to MRSA, MSSA caused fewer BSIs in nursing homes; however, iSA risk factors, including previous healthcare exposure, were similar. Continued study is needed to identify interventions effective against all iSA infections in nursing homes.Funding: NoneDisclosures: None

Methicillin-resistant Staphylococcus aureus (MRSA) colonization or infection of the wound may cause MRSA bacteremia with increased mortality, making it important to treat the infection. The increasing prevalence of MRSA accentuates the need for an effective therapy.1 Daptomycin is a cyclic lipopeptide antibiotic derived from Streptomyces roseosporus, which shows a potent bactericidal activity against most Gram-positive organisms including MRSA.1,2 Daptomycin received FDA approval in 2003 and was launched overseas. However it was approved for use in India after over 4 years (in 2008) without conducting any clinical trial in Indian population.3 Prior to this, a Sentry Antimicrobial Surveillance Program (2006-2007) performed in 14 medical centers in 13 Indian cities observed 100% susceptibility of the MRSA strains to Daptomycin.1 Following its introduction, limited data is available on the level of resistance to daptomycin in MRSA strains in India, making it important to have knowledge of the contemporary susceptibility levels. The present study was conducted in St. John's Medical College Hospital, a tertiary care multi-specialty hospital in Bangalore, India catering to patients of all socio-economic classes. We retrospectively determined the minimum inhibitory concentration (MIC) of daptomycin for clinically relevant, non-repetitive 30 MRSA and 20 methicillin-sensitive Staphylococcus aureus (MSSA) isolates randomly selected from 1615 Staphylococcus aureus isolates obtained from pus and wound swab samples (n=6687) submitted to the microbiology laboratory for aerobic culture and sensitivity profiling during January 2011 to December 2011. Among the 30 strains of MRSA, 22 strains were from hospital-acquired (HA)-MRSA infection and 8 strains were from community-acquired (CA)-MRSA infection. The majority of the patients harboring these MRSA strains were male (70%) and belonged to the age groups 21-40 years (46.7%), followed by 41-60 years (26.7%), ≤20 years (16.7%) and 61-80 years (10%). The patients harboring the studied MSSA strains were predominantly females (60%) and belonging to the age groups 21-40 years (45%), followed by 41-60 years (25%), 61-80 years and ≤20 years (15% each). The antibiotic resistance patterns of these isolates were determined by Kirby-Bauer disc diffusion method as per CLSI guidelines. The MIC for daptomycin (range: 0.016-256 μg/mL) was performed by E-test (bioMerieux, SA, France) according to CLSI guidelines. ATCC 29213 Staphylococcus aureus strain was used as a control. Table 1 shows the antibiotic resistance pattern of the strains included in this study. Vancomycin resistance by disc diffusion method was observed in 7% of the MRSA (n=2) and 5% (n=1) of the MSSA strains. All the isolates were susceptible to teicoplanin. The MIC levels of daptomycin against the MRSA and MSSA clinical isolates studied are shown in the Table 2. The MIC value for S. aureus ATCC 29213 was within the range 0.38-0.5 μg/mL. Daptomycin resistance in MRSA strains was observed at a low level of 6.7% (2/30). All the MRSA strains showed a MIC50/MIC90 of 0.38/1 μg/mL against daptomycin (MIC range: 0.19-2 μg/mL). Two HA-MRSA strains showed resistance to daptomycin (MIC: 2 μg/mL), retaining susceptibility to vancomycin. Daptomycin showed potent activity (MIC: ≤0.38 μg/mL) against vancomycin resistant MRSA (n=2) isolates. However since the MIC was not performed for vancomycin we could not ascertain whether these two strains were vancomycin resistant Staphylococcus aureus (VRSA) or vancomycin intermediate Staphylococcus aureus (VISA). It was further observed that the CA-MRSA strains (MIC50/MIC90: 0.25/0.5 μg/mL) were inhibited at two-fold lower MIC than HA-MRSA strains (MIC50/MIC90: 0.5/1 μg/mL). None of the twenty MSSA strains showed resistance to daptomycin (MIC50/MIC90: 0.38/1; range: 0.19-1 μg/mL). Table 1. Antibiotic resistance pattern of the MRSA and MSSA clinical isolates Table 2. Daptomycin minimum inhibitory concentration levels in MRSA and MSSA clinical isolates Although the sample size was small, daptomycin showed a good potency, inhibiting 93% of the MRSA strains. Our data supports the previous studies, showing good activity of daptomycin against MRSA strains. Earlier studies from India have reported daptomycin resistance in MRSA strains ranging from 0% to 10%.1,4–8 The studies reporting daptomycin resistance in Indian MRSA strains were from northern India (10%) and western India (6.25%).7, 8 To our knowledge for the first time we are reporting daptomycin resistance in MRSA (6.7%) from Southern India. With a well-documented safety profile and increased success rate in MRSA infection, daptomycin can be a viable therapeutic option for patients with MRSA wound infection. However in view of daptomycin resistant strains observed in our study we suggest that daptomycin MIC should be monitored to prevent treatment failure from possible emergence of strains with reduced susceptibility.

Introduction:Staphylococcus aureus (S. aureus) causes a variety of infections, ranging from a mild skin infection to blood stream infections and deep seated infections. As Stapylococcus aureus bacteremia (SAB) has the tendency to cause endovascular and metastatic infections, complications can occur at almost all sites of the body. Hence, SAB is associated with increased morbidity and mortality in spite of appropriate antimicrobial treatment. The virulence in S. aureus is determined by the presence of adhesins and toxins, which behave like superantigens (SAgs) and leads to a massive release of proinflammatory cytokines causing overwhelming inflammatory response leading to endothelial leakage, hemodynamic shock, multiorgan failure, and possibly death.Materials and Methods:One year prospective study conducted in a tertiary care hospital in southern part of India included all patients with SAB. Clinical details were filled according to. All isolates were subjected to polymerase chain reaction (PCR) for enterotoxin profiling.Results:A total of 101 patients of SAB were identified which comprises of 61 (60.4%) patients with methicillin-susceptible S. aureus (MSSA) and 40 (39.6%) patients with methicillin-resistant S. aureus (MRSA). Most common predictors of mortality were prior hospitalization and antibiotic intake, severe organ dysfunction, shock, tachycardia, and leukocytosis. Two-third of the isolates had at least one enterotoxin, most prevalent was sea; 28% and 27% (P - value = 0.001) MSSA isolates had seg and sei; whereas, 38.6% (P - value < 0.001) of MRSA isolates were found to have sea. The most common enterotoxin associated with mortality was sei, which comprised of 38% of all mortality.Conclusion:In SAB, the significant predictors of mortality were prior hospitalization and antibiotic intake, presence of multiorgan dysfunction, and shock. Although overall significance between the enterotoxin and shock could not be demonstrated, it successfully demonstrated the difference of enterotoxin between MSSA and MRSA.

Staphylococcus Aureus colonization and bacteremia in children with cancer.

The regulating gene of femA was studied in methicillin-resistant Staphylococcus aureus (MRSA). High-level MRSA, low-level MRSA and methicillin-sensitive S. aureus (MSSA) were identified by agar diffusion. Beta-lactamases were detected by nitrocephin and the presence of the mecA gene was determined by polymerase chain reaction (PCR). Only isolates that were both beta-lactamase-negative and mecA-positive were used. The femA gene and its 250 base pair (bp) upstream sequence were amplified by PCR and expression was determined by real-time fluorescent quantitative PCR. The 250 bp upstream sequence was labelled by BrightStar Psoralen-Biotin and detected by electrophoretic mobility shift assay (EMSA). Expression levels of femA in MSSA, low-level MRSA and high-level MRSA were 3.53 x 10(-3)% - 29.91%, 5.54 x 10(-3)% - 3.1 x 10(2)% and 13.88 - 5.50 x 10(4)%, respectively. EMSA detected a signal shift in 57 high-level MRSA isolates but not in four low-level MRSA and four MSSA strains. Expression of femA in high-level MRSA (non-beta-lactamase-producing) was higher than in low-level MRSA and MSSA. The femA regulating gene probably lies in the 250 bp upstream sequence in MRSA and high-level expression is essential for high-level methicillin resistance.

Objectives Staphylococcus aureus or methicillin-resistant Staphylococcus aureus (MRSA) has been an important pathogen causing bloodstream infections. Our study aimed to investigate the epidemiological and genetic diversity of clinical S. aureus isolates from patients with bloodstream infection in four hospitals of Shanghai from 2009 to 2011.MethodsA collection of S. aureus isolates causing bloodstream infection from four hospitals in the central part of Shanghai was carried out. Antimicrobial susceptibility testings of collected isolates were performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines, and spa-type, multi-locus sequence typing, agr type and toxin gene profiling were performed to explore the molecular diversity. Moreover, MRSA strains were also characterized by Staphylococcal cassette chromosome mec (SCCmec) typing.ResultsThe drugs such as linezolid, teicoplanin and vancomycin were efficacious for treating S. aureus including MRSA bloodstream infection. Methicillin-sensitive Staphylococcus aureus (MSSA) strains displayed distinct diversity in molecular characterization and toxin genes, and three virulent MSSA strains encoding at least five toxins were detected. Five community-associated MRSA (CA-MRSA) strains were found, but the majority (88.7%) of MRSA strains belonged to two epidemic clones (ST239-MRSA- III and ST5-MRSA- II) with different toxin gene profiles among patients with bloodstream infection.ConclusionsHealthcare-associated MRSA (HA-MRSA) strains were still the main pathogen causing bloodstream infections in spite of the emergence of CA-MRSA strains in hospital setting.

Molecular epidemiological studies of Staphylococcus aureus in urinary tract infection