Staphylococcus Aureus Isolates Research Articles

Detection of β-lactamase and antibiotic susceptibility of clinical isolates of Staphylococcus aureus

Abstract Staphylococcus aureus (SA) is the pathogen of greatest concern in the clinical worldwide because of its intrinsic virulence and ability to cause the diverse array of life-threatening infections. In the last two decades or so, antimicrobial resistance has evolved into one of the most formidable problems of infectious diseases. Bacteria acquire resistance to β-lactam antibiotics, most commonly due to the production of enzymes called β-lactamase. This enzyme hydrolyzes the amide bond of β-lactam antibiotics to make them ineffective. In this study, screening of clinical isolates of SA showed β-lactamase activity in 11 clinical isolates (SA-1745, SA-2071, SA-2940, SA-3151, SA-4423, SA-4620, SA-4627, SA-4693, SA-4696, SA-10760, Methicillin-resistant Staphylococcus aureus (MRSA), and one wild- type strain (SA-96) by iodometric and nitrocefin disk methods. The antibiotic susceptibility profiles of 12 strains of SA were determined for four β-lactam antibiotics viz. penicillin, ampicillin, cefoxitin and oxacillin. All the clinical isolates showed resistant to these antibiotics. Further, minimum inhibitory concentration (MIC) of four β-lactam antibiotics was also determined by micro-broth dilution assay. The MIC of penicillin, ampicillin and oxacillin against wild-type strain of SA was 0.078 µg/ml, whereas the MIC of cefoxitin against wild-type strain was recorded as 1.25 µg/ml. The MIC of these antibiotics against 11 clinical isolates of SA including methicillin-resistant Staphylococcus aureus (MRSA) ranged between 1.95 µg/ml to 1000 µg/ml. All clinical isolates were highly resistant to penicillin and ampicillin followed by cefoxitin and oxacillin. The outcomes of the present study can be useful for the screening of other natural bioactive compounds against these virulent strains.

1215. Geographic Distribution of Staphylococcus aureus With Reduced Sensitivity and Resistance to Vancomycin in the Dominican Republic

BackgroundResistant Staphylococcus aureus (SA) poses a major challenge to clinicians. The prevalence of methicillin-resistant SA (MRSA) has increased over the past decades, while vancomycin resistance remains rare. Only 14 cases of vancomycin-resistant SA (VRSA) have been described in the United States since 2002. VRSA and SA with reduced susceptibility to vancomycin (VISA) cause high morbidity and mortality. There is a paucity of data on VRSA in developing nations. We seek to define the prevalence and resistance profile of SA in the Dominican Republic (DR).MethodsThis is a retrospective review of resistance patterns of SA isolates from a clinical laboratory in the DR (Amadita Laboratories). Amadita provides services nationwide. Data collected from 2016 to 2017 included SA phenotypic sensitivity patterns and geographic location and income level. VISA and VRSA were defined as having minimum inhibitory (MIC) concentrations between 4 and 8 and MIC >16.ResultsOf 5,372 SA samples, 2,735 (51%) were MRSA, 21 were VISA and 39 were VRSA. VRSA samples were more commonly from Santo Domingo (SD) (Figure 1). Communities in SD with mixed and low incomes had greater burden of VRSA (Figure 2). Antimicrobial susceptibilities are shown in Table 1.Figure 1.VRSA samples in the DR by location.Figure 2.VRSA samples in Metropolitan SD based on income level of communities.Table 1: Antimicrobial Susceptibility for SA Isolates by Drug Resistance Category (%)CiprofloxacinClindamycinErythromycinGentamicinLevofloxacinLinezolidOxacillinQuinupristin-DalfopristinPenicillin GTrimethoprim Sulfamethoxazole (TMP-SMX)RifampinTetracyclinesTigecyclineVISA812333908010052100010010057100VRSA874351948794641006929771100ConclusionIn this nationwide sample, we found an alarming number of VISA and VRSA. Most cases were in metropolitan SD, with lower income communities carrying a higher case burden. Linezolid and TMP-SMX retain activity against VISA and VRSA in the DR. The rise of vancomycin resistance in developing countries and the disproportionate burden on communities of low income is concerning and requires further study. Infection control measures and antimicrobial stewardship interventions may help prevent further spread of resistant strains.Disclosures All authors: No reported disclosures.

Antimicrobial resistance, virulence gene profile and molecular typing of Staphylococcus aureus isolates from dairy cows in Xinjiang Province, northwest China.

Staphylococcus aureus (SA) is a major pathogen causing dairy cow mastitis and endometritis. Recently, animal-derived SA strains pose a serious public-health threat. However, little is known about antimicrobial resistance and virulence factors of SA isolated from dairy cows in Xinjiang, China. In this study, antimicrobial resistance, virulence gene profiles and genotypes of SA from clinical mastitis and endometritis in dairy cows were investigated. A total of 337 clinical samples (186 milk samples from clinical mastitis cases and 151 endometritis swab samples) were collected from 15 large-scale dairy farms and were screened for SA. All SA isolates were subjected to antimicrobial susceptibility testing, detection of virulence genes and molecular typing. A total of 155 SA strains were isolated; 22 (14.2%) were methicillin-resistant S. aureus (MRSA). Resistance of MRSA isolates was significantly higher than that of methicillin-susceptible S. aureus (MSSA). The percentage of virulence genes varied between MSSA and MRSA. The strains could be divided into two SCCmec types (I and IVa), three agr types (I, II and III) and four spa types (t779, t2883, t13751 and t1939). MLST identified 14 sequence types, among which ST1 and ST9 had relatively high detection rates. These findings revealed that ST9-t1939-agrI was the main genotype of MSSA, whilst ST1-SCCmecI-t1939-agrI was the main genotype of MRSA from dairy cows. More significantly, a novel ST (STX) was identified for the first time. The majority of SA strains from dairy cows were multidrug-resistant and carried multiple virulence genes, posing a potential public-health risk.

Alpha-Toxin Contributes to Biofilm Formation among Staphylococcus aureus Wound Isolates.

Biofilms complicate treatment of Staphylococcus aureus (SA) wound infections. Previously, we determined alpha-toxin (AT)-promoted SA biofilm formation on mucosal tissue. Therefore, we evaluated SA wound isolates for AT production and biofilm formation on epithelium and assessed the role of AT in biofilm formation. Thirty-eight wound isolates were molecularly typed by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (ST), and spa typing. We measured biofilm formation of these SA isolates in vitro and ex vivo and quantified ex vivo AT production. We also investigated the effect of an anti-AT monoclonal antibody (MEDI4893*) on ex vivo biofilm formation by methicillin-resistant SA (USA 300 LAC) and tested whether purified AT rescued the biofilm defect of hla mutant SA strains. The predominant PFGE/ST combinations were USA100/ST5 (50%) and USA300/ST8 (33%) for methicillin-resistant SA (MRSA, n = 18), and USA200/ST30 (20%) for methicillin-susceptible SA (MSSA, n = 20). Ex vivo AT production correlated significantly with ex vivo SA wound isolate biofilm formation. Anti-alpha-toxin monoclonal antibody (MEDI4893*) prevented ex vivo biofilm formation by MRSA USA300 strain LAC. Wild-type AT rescued the ex vivo biofilm defect of non-AT producing SA strains. These findings provide evidence that AT plays a role in SA biofilm formation on epithelial surfaces and suggest that neutralization of AT may be useful in preventing and treating SA infections.

Pediatric neck abscesses: No increase in methicillin-resistant Staphylococcus aureus

IntroductionRecent studies from Western countries showed an increased incidence rate of methicillin-resistant Staphylococcus aureus (MRSA) isolated from pediatric neck abscesses cultures. We sought to examine the microbiology and antibiotic susceptibility of such samples over a 10-year period, and particularly of Staphylococcus aureus (SA), in order to determine whether a similar trend exists in our institution. MethodsA retrospective chart review of children ≤18 years that underwent needle aspiration or surgical drainage of neck abscesses, including suppurative lymphadenitis, retropharyngeal abscesses, and parapharyngeal abscesses was conducted between 1/1/06–31/12/15. ResultsSixty-two children were identified with a male predominance (34, 55%). The median age was 2 years. There were 37 (60%) suppurative lymphadenitis, 15 (24%) parapharyngeal abscess, and 10 (16%) retropharyngeal abscess cases. Twenty-nine (47%) children received antibiotic treatment prior to admission, most commonly β-lactam agents. Of them, 15 (52%) had positive cultures, including 7 (47%) with SA. On admission, 45 (73%) children had already received amoxicillin-clavulanate. Of those who did not improve, 16 (26%) received ceftriaxone and clindamycin. Twenty-one (38%) cultures were negative. The most common isolated bacteria were SA in 13 (24%), Streptococcus pyogenes in 7 (13%), and Streptococcus viridians group in 9 (16%). Of the SA isolates, there was only 1 (8%) case of MRSA; however, there were 4 (31%) clindamycin-resistant SA isolates. ConclusionUnlike previously published data, there was no increase in MRSA incidence at our institution. However, the high prevalence of clindamycin-resistant SA was in line with previous reports. These findings should be considered when starting empirical therapy in pediatric neck abscesses.

Antibiotic Resistance in Young Children in Kilosa District, Tanzania 4 Years after Mass Distribution of Azithromycin for Trachoma Control.

Mass administration of azithromycin (MDA) is integral to trachoma control. Recent studies suggest that MDA may increase drug-resistant pathogens, yet findings from prior studies suggest little long-term impact on resistance. This disparity may be linked to differences in pre-MDA community-level resistance patterns. We describe carriage prevalence and antibiotic resistance patterns for Streptococcus pneumoniae (Spn) (nasopharyngeal swab collection), Staphylococcus aureus (SA) (nasopharyngeal swabs), and Escherichia coli (EC) (rectal swabs) in 1,047 children ages 1-59 months in a district with MDA cessation 4 years ago. Antibiotic susceptibility was evaluated by disk diffusion and Etest. The carriage rates for Spn, SA, and EC were 43.5% (455/1,047), 13.2% (138/1,047), and 61.7% (646/1,047), respectively. Resistance to AZM was observed in 14.3%, 29.0%, and 16.6% of the Spn, SA, and EC isolates, respectively. Spn resistance was variable (0-67%) by hamlet. Future analyses will assess the influence of pre-MDA antibiotic resistance patterns on those observed following MDA.

Penicillin-susceptible Staphylococcus aureus: susceptibility testing, resistance rates and outcome of infection

Background: Staphylococcus aureus (SA) is an important human pathogen that causes both superficial and invasive infections. Penicillin is now rarely used in the treatment of SA infections due to widespread resistance and a concern about the accuracy of existing methods for penicillin susceptibility testing. The aims of the present study were to determine the frequency of penicillin-susceptible SA isolates from blood and wound cultures in Lund, Sweden, and to evaluate methods for penicillin testing in SA. We also wanted to investigate if penicillin-susceptible isolates are associated with higher mortality.Methods: Hundred blood culture isolates collected 2008/2009, 140 blood culture isolates from 2014/2015, and 141 superficial wound culture strains from 2015 were examined. Penicillin susceptibility was tested with disk diffusion according to EUCAST guidelines, and results were confirmed with a cloverleaf assay and PCR amplification of the BlaZ gene. Patient data for all bacteraemia cases were extracted from medical records.Results: The disk diffusion method with assessment of both zone size and zone edge appearance had high accuracy in our study. About 57% of bacteraemia isolates from 2008/2009 were sensitive to penicillin compared to 29% in 2014/2015 (p < .0001). In superficial wound cultures, 21% were penicillin susceptible. There was no difference in co-morbidity or mortality rates between patients with penicillin resistant and penicillin sensitive SA bacteraemia.Conclusion: Disk-diffusion is a simple and reliable method to detect penicillin resistance in SA, and susceptibility rates are significant. Penicillin has many theoretical advantages and should be considered in the treatment of SA bacteraemia when susceptible.

Predictive Characteristics of Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Swab for MRSA-positive Culture in Hospitalized Veterans

BackgroundProviders often must decide whether to empirically treat hospitalized patients for MRSA. The results of routine MRSA nares swabs often are available prior to clinical culture results, so could conceivably help guide antibiotic selection. However, the reported predictive value of nares swabs is mixed. Therefore, we sought to define the predictive characteristics of MRSA nares swabs for the MRSA status of clinical Staphylococcus aureus(SA) isolates at the Minneapolis Veterans Affairs Medical Center (MVAMC).MethodsWe retrospectively reviewed electronic health records (EHRs) of 599 MVAMC inpatients with a clinical SA isolate between 2013 and 2016. The SA isolates were from skin/soft tissue (n = 281), blood (n = 99), respiratory (n = 90), urine (n = 62), and bone/joint (n = 27). We recorded each isolate’s MRSA vs. MSSA status and the result of the temporally closest MRSA nares swab, then compared swab and culture results in relation to culture site and swab-to-culture interval.ResultsOverall, for identifying MRSA among patients with a clinical SA isolate, the MRSA nares swab’s sensitivity was 65.1%, specificity 96.2%, positive predictive value (PPV) 91.4%, and negative predictive value (NPV) 81.9%. The odds ratio (OR) of a positive MRSA nares swab for a MRSA-positive culture was 47.9 (95% confidence interval [CI] 25.7–89.2). Exclusion of the 70 nares swabs that were collected > 14 days before the clinical isolate increased the NPV to 84.0%, with a corresponding sensitivity 68.0%, specificity 83.9%, and PPV 90.3%. Test performance varied significantly by culture site (Table).Culture SiteOR (95% CI)Sens. (%)Spec. (%)PPV (%)NPV (%)All47.9 (25.7–89.2)65.196.291.481.9Skin/soft tissue59.7 (22.5–158.3)63.497.293.081.9Blood65.9 (13.6–319.9)95.896.992.085.1Respiratory64.1 (13.3–309.5)73.295.993.881.0Urine13.5 (3.7–49.5)64.388.281.875.0Bone/jointN/A20.0100.0100.084.6ConclusionA positive MRSA nares swab greatly increased the odds that a SA isolate was MRSA. However, sensitivity and NPV were lower than some prior studies. Our findings suggest that, for veterans with a severe infection that might be due to SA, a negative MRSA nares screen provides insufficient NPV to allow confident omission of empiric MRSA-active antibiotics.Disclosures All authors: No reported disclosures.

Relationship between pathogenic, clinical, and virulence factors of Staphylococcus aureus in infective endocarditis versus uncomplicated bacteremia: a case-control study.

Pathogenic factors of Staphylococcus aureus (SA) in the development of infective endocarditis (IE) have not been sufficiently investigated. The purpose of this study was to analyze the pathogenesis and virulence factors of SA in patients with IE as compared to patients with uncomplicated bacteremia (un-BAC). This is a retrospective case-control study (2002-2014) performed at a tertiary hospital in Spain. Clinical and epidemiological factors were analyzed. We assessed the presence of toxin genes [toxic shock syndrome toxin 1 (tst-1) and enterotoxins A (etA), B (etB), and D (etD)] and the potential relationship between accessory gene regulator (agr) groups and the development of IE confirmed by polymerase chain reaction (PCR). Twenty-nine patients with IE were compared with 58 patients with uncomplicated S. aureus bacteremia (SAB). As many as 75.9 % of patients had community-acquired IE (p < 0.005). Multivariate analysis revealed that there is a significant relationship between community-acquired infection and severe sepsis or septic shock and IE. Also, a minimum inhibitory concentration (MIC) of vancomycin ≥1.5 μg/ml was found to be associated with IE. The agr group I was prevalent (55.2 % vs. 31.0 %; p = 0.030). No association was observed between toxin genes (tst-1, etA, etB, and etD) and IE. The superantigen (SAg) most frequently found in SA isolates was tst-1 (12.6 %). We found no association between toxin genes and IE, probably due to the small sample size. However, a direct relationship was found between agr I and the development of IE, which suggests that agr I strains may have more potential to cause IE.

Clinical variables and Staphylococcus aureus virulence factors associated with venous thromboembolism in children

ObjectivesChildren with Staphylococcus aureus (SA) bacteremia risk developing venous thromboembolism (VTE). We sought to identify clinical variables and bacterial virulence factors associated with VTE in SA bacteremia. Study designThis is a single-institution retrospective study of 229 children with SA bacteremia hospitalized from 2005 to 2008. Clinical data were abstracted from patient charts. Two-hundred three SA isolates were analyzed by polymerase chain reaction. The Pediatric Health Information System (PHIS) database was queried to identify subjects with a central venous line (CVL) or complex chronic conditions (CCC). Logistic regression analysis was employed to determine which factors most greatly influenced VTE. ResultsVTE was present in 9.2% (n=21/229). Superficial thrombi were excluded. Mortality was greater in patients with VTE [24% vs. 6% (p=0.016)]. Among SA isolates available for virulence testing, the majority (70%; n=139) were methicillin-sensitive SA (MSSA). Methicillin-resistant SA (MRSA) infection was associated with VTE (p=0.01). The most common sites of thrombosis were extremity deep vein (58%; n=14/24), head/neck (29%; n=7), and visceral (13%; n=3). One subject had a pulmonary embolism. The presence of a CVL or a CCC was not associated with VTE. Independent predictors of VTE were C-reactive protein (CRP)≥20mg/dl [OR 4.2, 95% CI 1.16–15.25] and hemoglobin nadir ≤9g/dl [OR 5.2, 95% CI 1.3–20.64]. ConclusionsIn addition to MRSA infection, CRP≥20mg/dl and hemoglobin nadir ≤9g/dl were associated with VTE in SA bacteremia. These factors may serve as markers for increased risk of VTE with invasive SA disease.

Clinical features and Staphylococcus aureus colonization/infection in childhood atopic dermatitis

Introduction: Staphylococcus aureus (SA) colonization/infection is important in the pathophysiology of childhood atopic dermatitis (AD). This study evaluated which clinical features may predict presence of SA colonization/infection and reviewed antimicrobial sensitivity of SA in patients with AD. Methods: The associations between bacteriologic culture results of skin swabs (taken at the most severely affected area and at the antecubital fossa) and SCORing-Atopic-Dermatitis (SCORAD), skin hydration, transepidermal water loss (TEWL), and quality of life were evaluated. Results: Moderate-to-heavy growth of SA was present in 31% of the swabs of the most severe area and in 16% of the flexural (antecubital fossae) areas of 95 AD patients (12.5 ± 4.8 years). Binomial logistic regression showed moderate-to-heavy growth of SA in the severe area were associated with objective SCORAD (p = 0.004) and lesion intensity [erythema (p = 0.022) and lichenification (p = 0.035)]; and excoriation (p = 0.024) and TEWL (p = 0.009) in the antecubital fossa. The relative risk of isolating moderate-to-heavy growth of SA in the most affected area in patients with severe disease (objective SCORAD >40) is 2.73 (1.43–5.21, p = 0.001). Any growth of SA in either swab sites was associated with objective SCORAD and lesion intensity (p = 0.001–0.019). SA had no association with quality of life and other clinical parameters. All specimens of methicillin-sensitive SA were sensitive to cloxacillin. All methicillin-resistant SA (MRSA) (5.7%) was sensitive to co-trimoxazole and fusidic acid. Conclusions: Clinical features, especially severity and lesion intensity, are useful in “predicting” moderate-to-heavy SA colonization/infection in AD patients. Cloxacillin has a favorable sensitivity profile for MSSA, and co-trimoxazole and fusidic acid for MRSA. As colonization and infection are ambiguous and potentially overlapping clinical states, we recommend to abandon these terms and propose to describe quantitatively/semi-quantitatively SA isolation as none, mild, scanty, moderate or heavy growth instead in clinical trials.

Staphylococcus aureus, Including Meticillin-Resistant Staphylococcus aureus, among General Practitioners and Their Patients: A Cross-Sectional Study.

BackgroundThe role of general practitioners (GPs) as reservoir and potential source for Staphylococcus aureus (SA) transmission is unknown. Our primary objective was to evaluate the prevalence of SA and community-acquired methicillin resistant SA (CA-MRSA) carrier status (including spa typing) among GPs and their patients in Belgium. The secondary objective was to determine the association between SA/CA-MRSA carriage in patients and their characteristics, SA carriage in GPs, GP and practice characteristics.MethodsThe Belgian GPs, who swabbed their patients in the APRES study (which assessed the prevalence of SA nasal carriage in nine European countries; November 2010 –June 2011), were asked to swab themselves as well (May-June 2011). GPs and their patients had to complete a questionnaire on factors related to SA carriage and transmission. SA isolation including CA-MRSA and spa typing was performed on the swabs.ResultsIn eighteen practices 34 GPs swabbed patients of which 25 GPs provided personal swabs. The analysis was performed on 3008 patient records. Among GPs SA carriage (28%) was more prevalent than among their patients (19.2%), but CA-MRSA carriage was not present. SA was more prevalent among younger patients and those living with cattle. Spa typing SA and MRSA strains did not suggest correlation within practices or between patients and GPs, but chronic skin conditions of GPs and always handshaking patients by SA positive GPs were associated with more SA among patients, and hand washing after every patient contact with less SA among patients in practices with high antibiotic prescribing rates.ConclusionNo MRSA was found among GPs, although their SA carriership was higher compared to their patients’. Spa types did not cluster within practices, possibly due to difference in timing of swabbing. To minimise SA transmission to their patients GPs should consider taking appropriate care of their chronic skin diseases, antibiotic prescribing behaviour, handshaking and hand washing habits.

Isolation and Host Range of Bacteriophage with Lytic Activity against Methicillin-Resistant Staphylococcus aureus and Potential Use as a Fomite Decontaminant.

Staphylococcus aureus (SA) is a commensal bacterium and opportunistic pathogen commonly associated with humans and is capable of causing serious disease and death including sepsis, pneumonia, and meningitis. Methicillin-resistant SA (MRSA) isolates are typically resistant to many available antibiotics with the common exception of vancomycin. The presence of vancomycin resistance in some SA isolates combined with the current heavy use of vancomycin to treat MRSA infections indicates that MRSA may achieve broad resistance to vancomycin in the near future. New MRSA treatments are clearly needed. Bacteriophages (phages) are viruses that infect bacteria, commonly resulting in death of the host bacterial cell. Phage therapy entails the use of phage to treat or prevent bacterial infections. In this study, 12 phages were isolated that can replicate in human SA and/or MRSA isolates as a potential way to control these infections. 5 phage were discovered through mitomycin C induction of prophage and 7 others as extracellular viruses. Primary SA strains were also isolated from environmental sources to be used as tools for phage discovery and isolation as well as to examine the target cell host range of the phage isolates by spot testing. Primary isolates were tested for susceptibility to oxacillin in order to determine which were MRSA. Experiments were performed to assess the host range and killing potential of newly discovered phage, and significant reductions in bacterial load were detected. We explored the utility of some phage to decontaminate fomites (glass and cloth) and found a significant reduction in colony forming units of MRSA following phage treatment, including tests of a phage cocktail against a cocktail of MRSA isolates. Our findings suggest that phage treatment can be used as an effective tool to decontaminate human MRSA from both hard surfaces and fabrics.

87 Detection of enterotoxins (A–E) from Staphylococcus aureus isolated from CF sputum: Clinical significance of enterotoxigenic (ET+) strains of S. aureus in paediatric and adult CF patients

Objectives Staphylococcus aureus (SA) can produce several entertoxins (ETs) that may cause nausea and vomiting when ingested. Chronic colonisation of the CF airways by high numbers (10 8 –10 9 cfu/ml sputum) of ET+ SA may allow ET production in situ in the CF airways. It was therefore the aim of this study to examine CF SA isolates and CF sputum for the presence of ETs. Methods Sixteen CF patients, who were chronic/intermittently colonised with SA, were selected at random from adult and paediatric CF services. Following laboratory optimisation of an ELISA (R-Biopharm Rhone) for the detection of SA ETs A–E, spent Brain Heart Infusion broth from late logarithmic SA cultures were examined for SA ETs. In addition, sputum sol samples from 19 SA positive patients were also tested for ETs. Results Five of 16 cultures (31.3%) were positive for ETs. These samples came from 4 females and 1 male, including 4 children and 1 adult [4 delF508 homogygous + 1 delF508/R117H]. When controlled for delF508/delF508, these ET+ SA patients were compared to CF patients with chronic/intermittent colonisation with known ET − SA strains. There was no significant difference (p>0.05) in %FEV1 and BMI values between these two patient groups. ETs were not detected in any of the sputum sol samples. Conclusion The carriage of ETs in CF-related SA (31.3%) is approximately half that previously reported from SA isolated from non-CF student nasal swabs (66.7%). Further work is required to optimise detection of ETs in sputum sol samples.

Antibiotic Resistance in the Treatment of Staphylococcus aureus Keratitis: a 20-Year Review.

We compared the resistance patterns of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA) keratitis isolates with the common topically applied ophthalmic antimicrobials. We reviewed the antibiotic susceptibility results of 122 MRSA and 276 MSSA keratitis isolates from January 1993 to November 2012. In vitro susceptibility testing of each Staphylococcus aureus (SA) isolate was performed using Kirby-Bauer disk diffusion based on modified serum interpretations for cefoxitin, bacitracin, cefazolin, ciprofloxacin, gatifloxacin, gentamicin, moxifloxacin, ofloxacin, polymyxin B, sulfamethoxazole, tobramycin, and trimethoprim. MRSA represented 30.7% (122 of 398) of the total SA isolates. All the SA isolates were susceptible to vancomycin, whereas they were less susceptible to the fluoroquinolones than to the non-fluoroquinolones. In comparison with MSSA, MRSA was significantly more resistant to all the antibiotics tested other than polymyxin B (both equally resistant) and vancomycin (both equally susceptible) (P < 0.001). Besides vancomycin, MRSA demonstrated the best susceptibilities to sulfamethoxazole (94.3%), bacitracin (89.3%), trimethoprim (88.5%), and gentamicin (86.1%). Additionally, MRSA was found to be significantly more resistant to the second-generation fluoroquinolones (ciprofloxacin and ofloxacin) than to the fourth-generation fluoroquinolones (moxifloxacin and gatifloxacin). An increase in resistance to the fourth-generation fluoroquinolones was detected for both MRSA and MSSA over the study period. The in vitro susceptibilities of commonly used topical antibiotics differ for MRSA and MSSA isolates; thus, successful treatment of bacterial keratitis should be supported with laboratory studies. Vancomycin remains the treatment of choice for MRSA keratitis. The empiric use of second-generation fluoroquinolones seems to be contraindicated in the treatment of MRSA keratitis.

Epidemiological and biological determinants of Staphylococcus aureus clinical infection in New York State maximum security prisons.

Large outbreaks of Staphylococcus aureus (SA) infections have occurred in correctional facilities across the country. We aimed to define the epidemiological and microbiological determinants of SA infection in prisons to facilitate development of prevention strategies for this underserved population. We conducted a case-control study of SA infection at 2 New York State maximum security prisons. SA-infected inmates were matched with 3 uninfected controls. Subjects had cultures taken from sites of infection and colonization (nose and throat) and were interviewed via structured questionnaire. SA isolates were characterized by spa typing. Bivariate and multivariable analyses were conducted using conditional logistic regression. Between March 2011 and January 2013, 82 cases were enrolled and matched with 246 controls. On bivariate analysis, the use of oral and topical antibiotics over the preceding 6 months was strongly associated with clinical infection (OR, 2.52; P < .001 and 4.38, P < .001, respectively). Inmates with clinical infection had 3.16 times the odds of being diabetic compared with inmates who did not have clinical infection (P < .001). Concurrent nasal and/or oropharyngeal colonization was also associated with an increased odds of infection (OR, 1.46; P = .002). Among colonized inmates, cases were significantly more likely to carry the SA clone spa t008 (usually representing the epidemic strain USA300) compared to controls (OR, 2.52; P = .01). Several inmate characteristics were strongly associated with SA infection in the prison setting. Although many of these factors were likely present prior to incarceration, they may help medical staff identify prisoners for targeted prevention strategies.

Staphylococcal enterotoxins stimulate lymphoma-associated immune dysregulation

Patients with cutaneous T-cell lymphoma (CTCL) are frequently colonized with Staphylococcus aureus (SA). Eradication of SA is, importantly, associated with significant clinical improvement, suggesting that SA promotes the disease activity, but the underlying mechanisms remain poorly characterized. Here, we show that SA isolates from involved skin express staphylococcal enterotoxins (SEs) that induce crosstalk between malignant and benign T cells leading to Stat3-mediated interleukin-10 (IL-10) production by the malignant T cells. The SEs did not stimulate the malignant T cells directly. Instead, SEs triggered a cascade of events involving cell-cell and asymmetric cytokine interactions between malignant and benign T cells, which stimulated the malignant T cells to express high levels of IL-10. Much evidence supports that malignant activation of the Stat3/IL-10 axis plays a key role in driving the immune dysregulation and severe immunodeficiency that characteristically develops in CTCL patients. The present findings thereby establish a novel link between SEs and immune dysregulation in CTCL, strengthening the rationale for antibiotic treatment of colonized patients with severe or progressive disease.

Changing patterns and antibiotic resistance of Staphylococcus aureus in a pediatric clinic from 2003 to 2012 year

Objective To investigate the changing patterns of Staphylococcus aureus(SA) and its resistance from a paediatric clinic in Beijing Children's Hospital Affiliated to Capital University of Medical Sciences. Methods SA isolated from hospitalized patients in Beijing Children's Hospital Affiliated to Capital University of Medical Sciences from Jan.2003 to Dec.2012 were analyzed.Antimicrobial susceptibility was determined by disk diffusion method and Phoenix 100 microbiological system.Results were analyzed according to the 2012 guidelines of Clinical and Laboratory Standard Institute. WHONET 5.6 software was used to analyze the data. Results The clinical isolates of SA from inpatient were 2 843. The positive rates of SA were 10.0%, 8.7%, 9.0%, 11.6%, 12.7%, 11.7%, 10.5%, 10.8%, 11.9% and 11.7% form 2003 to 2012, respectively.The positive rate of Methicillin-resistant Staphylococcus aureus(MRSA)from inpatients was 10.9%. The positive rates of MRSA were 3.1%, 5.4%, 6.4%, 4.1%, 6.0%, 10.6%, 11.2%, 12.7%, 14.1% and 20.1% form 2003 to 2012, respectively. The resistant rate of Methicillin-susceptible Staphylococcus aureus and MRSA to Penicillin were 91.4% and 100.0%, Oxacillin were 0 and 100.0%, Cefuroxime were 0.5% and 87.7%, Ceftriaxone were 0.1% and 90.3%, Amoxicillin-clavulanic acid were 0.9% and 86.7%, Erythromycin were 72.4% and 92.2%, Clindamycin were 50.6% and 80.3%, Ciprofloxacin were 2.2% and 30.1%, Trimethoprim-sulfamethoxazol were 12.2% and 13.9%. Vancomycin-intermediate and Vancomycin-resistant Staphylococcus aureus were not found. Conclusions The prevalence of MRSA is increasing in paediatric inpatients.And MRSA isolates exhibit multidrug resistance.The sequential surveillance about SA is very important for guiding rational antimicrobial therapy and effective control of infections in paediatric patients. Key words: Staphylococcus aureus; Antimicrobial agent; Antibiotics resistance surveillance; Child

Enhanced surveillance of Staphylococcus aureus at Gauteng Academic Hospitals

Background: Bloodstream infections (BSI) are significant cause of mortality in patients worldwide. Among Gram-positive bacteria, Staphylococcus aureus (SA) is the most common pathogen that expresses virulence factors, develops resistance to antimicrobial agents and is prevalent in the hospital and the community settings. These features explain the need to monitor and report SA trends and patterns of antimicrobial resistance. We aimed to determine the characteristics of S. aureus bacteremia cases during one year study period and to describe the proportion of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) cases by site. Methods & Materials: The surveillance was based on a cross- sectional study design. Bacteraemia cases were reported through an active, enhanced antimicrobial resistance surveillance programme and SA was initiated in September 2012. The data for a one year period was analyzed. Susceptibility testing was performed on MicroScan® using PB28 panels for SA. We established MIC50 and MIC90 breakpoint values and the percentage of susceptibility. CLSI standards were applied for susceptibility breakpoints. We investigated the presence of β-lactamases and mecA genes by PCR. Molecular typing was done using conventional typing methods. Results: During the study period, a total of 307 SA isolates were recorded, equally from each site, of which 254 isolates were received. From susceptibility testing performed, 95 (37%) isolates were MRSA. The proportion of MRSA decreased from 47% in 2012 to 33% in 2013. The most prevalent SCCmec type identified was SCCmec type III (67%) followed by types IV (33%). Clinically, the outcome of patients with MRSA did worse 22 (42%) died (p = 0.0042), had a hospital stay longer than 21 days (p = 0.022) and received antimicrobial treatment two months prior to admission (p = 0.016) compared to patients with MSSA. Empirical treatment of MRSA bacteraemia was appropriate in 24% of cases. Conclusion: There is a high percentage of MRSA at sentinel sites in Gauteng. The majority of isolates have been identified as SCCmec typeIII. A greater proportion of patients with MRSA had received previous antimicrobial agents and had a longer duration of hospitals stay. Infection control measures and appropriate use of antimicrobial agents are critical for the prevention of MRSA.

Inducible Clindamycin Resistance Among the Staphylococcus aureus Colonizing the Anterior Nares of School Children of Udupi Taluk

Clindamycin is one of the preferred antibiotics in the treatment of Staphylococcus aureus (SA) skin and soft tissue infections. However the emergence of inducible clindamycin resistant SA is a major concern for clinicians in the management of such infections. Information about such resistant strains of SA colonizing the anterior nares is very important in planning infection control strategies. The objective of the current study was to assess the proportion of SA showing inducible clindamycin resistance and also to know their association with methicillin resistance. Among the isolates, 11.6% (44/378) strains were showing positive D test which indicates inducible clindamycin resistance and a highly significant 71% (12/17) inducible clindamycin resistance was also noticed in the case of MRSA. The nasal carriage of inducible clindamycin resistant SA showing a significant association with MRSA strains by the paediatric population from this area warrants the inclusion of D test in the routine antibiotic susceptibility testing of SA isolates. Information about the MLSBi status among the colonizing strains would also help the public health authorities to plan and implement infection control strategies at the community level.DOI: http://dx.doi.org/10.3126/nje.v4i1.10136 Nepal Journal of Epidemiology 2014;4 (1): 337-340