Characterization of the clonal profile of MRSA isolated in neonatal and pediatric intensive care units of a University Hospital

MRSA outbreak in a Neonatal Intensive Care Unit in a developed country: importance of rapid detection of reservoirs and implementation of intervention measures

We described a MRSA bloodstream infection outbreak that was rapidly identified and controlled in a Neonatal Intensive Care Unit after implementation of a bundle of measures, including PCR-screening and HCW decolonization. We found 35% of healthcare workers(HCW) colonized with S. aureus by PCR, one of them that presented skin lesion positive for MSSA (same clone and spa type than two patients). Our findings raise the hypothesis that the outbreak could be related to HCW colonization.

Prevalence of methicillin-resistant Staphylococcus aureus colonization among healthcare workers at a tertiary care hospital in northeastern Brazil

BACKGROUND

Staphylococcus aureus is a human pathogen of clinical importance related to a variety of infections.

AIM

The objective of this study was to analyze the molecular and epidemiological characteristics of S. aureus obtained from healthcare professionals (HCP) of a hospital in southwestern Bahia, Brazil.

METHODS

Samples were collected from hands, nasal cavity, and laboratory coats of 80 HCP. The bacterial isolates recovered from 240 samples were identified as S. aureus, and then analyzed for their antimicrobial resistance profile, genotypic characterization, and pathogenicity.

FINDINGS

178 isolates were identified as S. aureus, being mostly isolated from the nasal cavity. Thirty isolates (16.8%) were characterized as MRSA. The virulence gene frequency varied according to isolate source. All virulence genes were identified in at least one hand isolate. Isolates from laboratory coats did not show seb and pvl. Isolates from the nasal cavity did not exhibit pvl. The SCCmec type I was identified in 56.7% of MRSA isolates. Among MRSA isolates, 14 PFGE pulsotypes were characterized, with profile A being predominant (nine isolates). Clonal complexes CC5, CC45, and CC398 were found. MRSA isolates induced cytokine gene expression in macrophages, with IL-10 and IL-17 being expressed more often.

CONCLUSION

We found a high colonization rate for S. aureus among HCP. Moreover, we observed that MRSA strains presented different virulence factors and could induce cytokine gene expression, indicating an urgent need to control colonization rates of HCP by MRSA isolates in order to protect hospital patients and the general public.

The History of Methicillin-Resistant Staphylococcus aureus in Brazil

Since the emergence of MRSA in the 1960s, a gradual increase in infections by resistant bacteria has been observed. Clinical manifestations may vary from brand to critical condition due to host risk factors, as well as pathogen virulence and resistance. The high adaptability and pathogenic profile of MRSA clones contributed to its spread in hospital and community settings. In Brazil, the first MRSA isolates were reported in the late 1980s, and since then different genetic profiles, such as the Brazilian epidemic clone (BEC) and other clones considered a pandemic, became endemic in the Brazilian population. Additionally, Brazil's MRSA clones were shown to be able to transfer genes involved in multidrug resistance and enhanced pathogenic properties. These events contributed to the rise of highly resistant and pathogenic MRSA. In this review, we present the main events which compose the history of MRSA in Brazil, including numbers and locations of isolation, as well as types of staphylococcal cassette chromosome mec (SCCmec) found in the Brazilian territory.

Incidence and characteristics of methicillin-resistant coagulase-negative Staphylococcus aureus in peritoneal dialysis-associated peritonitis in a single center using molecular methods

PURPOSE

Peritonitis is a serious complication of peritoneal dialysis and coagulase-negative Staphylococcus (CNS) is the most frequent cause of peritoneal dialysis (PD)-infections in many centers. This study aimed to investigate the molecular epidemiology of CNS isolated from PD-peritonitis in a Brazilian single center, focusing on the genetic determinants conferring methicillin resistance.

METHODS

Bacterial strains were isolated from peritoneal fluid of patients presenting PD-peritonitis, identified by phenotypic and molecular methods, and those identified as CNS were submitted to mecA detection, SCCmec, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).

RESULTS

Over the 18-year period of this study (1995-2011), a total of 878 peritonitis episodes were diagnosed in this unit, 115 were caused by coagulase-negative staphylococci of which 72 by Staphylococcus epidermidis. mecA gene was detected in 55 CNS (47.8%), more frequently on the more recent years. SCCmec type III was the most frequent cassette, followed by SCCmec type IV and SCCmec type II. A diverstity of pulsotypes was observed among the S. epidermidis isolates, but five clusters (based on the 80% cutoff) were identified. Diversified sequence types (ST02, ST05, ST06, ST09, ST23, ST59 and ST371) were detected.

CONCLUSIONS

Detection of SCCmec type III among coagulase-negative Staphylococcus underscores the role of hospital environments as potential source of methicillin-resistant Staphylococcus causing peritonitis in PD patients.

Molecular epidemiology of methicillin-resistant Staphylococcus aureus in the Brazilian primary health care system

OBJECTIVE

To evaluate the molecular epidemiology and to georeference Staphylococcus aureus isolated from wounds and nares of patients seen at Basic Health Units (BHUs) of a Brazilian city.

METHODS

Observational, cross-sectional study conducted from 2010 to 2013. A total of 119 S. aureus strains isolated from the wounds and nares of 88 patients were studied. The isolates were characterised by identifying virulence genes encoding enterotoxins A-E, haemolysins α, β and δ, exfoliatins A, B and D, biofilm production, Panton-Valentine Leukocidin and toxic shock syndrome toxin 1, and by pulsed-field gel electrophoresis (PFGE), multilocus sequence and spa typing.

RESULTS

Eighteen methicillin-resistant Staphylococcus aureus (MRSA) (6 SCCmec type II and 12 SCCmec type IV) and 101 (85%) MSSA were identified. PFGE typing resulted in the formation of eight clusters, with STs 1, 5, 8, 30, 188, 1176 and 1635 and spa type t002 being the predominant types among MSSA. The 18 MRSA belonged to STs 5, 8 and 1176 and spa types t002 and t062.

CONCLUSION

The results demonstrate widespread dissemination of MSSA and MRSA clones carrying haemolysin, biofilm and toxin genes. Kernel density estimation revealed the highest density of S. aureus in the 4, 5 and 8 BHUs.

Comparison of Nasal Colonization of Methicillin-Resistant Staphylococcus aureus in HIV-Infected and Non-HIV Patients Attending the National Public Health Laboratory of Central Nepal

Background

Staphylococcus aureus is a cardinal source of community- and hospital-acquired infection. HIV infection is a well-recognized risk factor for methicillin-resistant S. aureus (MRSA) carriage and infection. Intrinsically developed antibiotic resistance has sharply increased the burden of MRSA which is often associated with morbidity and mortality of the patients. Moreover, nasal carriage of S. aureus plays a significant role in spread of community-associated (CA) S. aureus infections.

Methods

This study was conducted from June 2016 to December 2016 at National Public Health Laboratory (NPHL), Kathmandu, with an aim to assess the rate of S. aureus nasal carriage and MRSA carriage among HIV-infected and non-HIV patients. A total of 600 nonrepeated nasal swabs were analyzed following standard microbiological procedures, where 300 swabs were from HIV-infected patients while remaining 300 were from non-HIV patients. The isolates were identified on the basis of colony characteristics and a series of biochemical tests. The antibiotic susceptibility test (AST) was performed by the modified Kirby–Bauer disc diffusion method. Inducible clindamycin resistance in isolates was confirmed by the D-test method.

Results

Overall, out of 600 nasal swabs of patients tested, 125 (20.8%) were S. aureus nasal carriers which included 80 out of 300 (26.66%) among HIV-infected patients and 45 (15%) out of 300 among non-HIV patients, and the result was statistically significant (p=0.0043). Among the isolated S. aureus, 11 (13.8%) MRSA were confirmed in HIV-infected while 3 (6.7%) MRSA were detected from non-HIV patients. A higher number of S. aureus carriers was detected among HIV-infected males 40 (26.49%), whereas MRSA carriage was more prevalent among HIV-infected females 7 (5.1%). Among the HIV-infected, patients of age group 31–40 years were the ones with highest carriage rate 36 (45%), while in non-HIV patients, the highest rate 13 (28.9%) of carriage was detected among the patients of age group 21–30 years. Statistically significant difference was found between S. aureus carriage and HIV infection in patients (p < 0.05). Higher rate 2/3 (66.7%) of inducible clindamycin resistance in MRSA was detected from non-HIV patients in comparison to HIV-infected patients 7/11 (63.63%) while the result was statistically insignificant (p > 0.05). All the MRSA isolates (100%) were resistant against co-trimoxazole while ciprofloxacin showed high rate of sensitivity towards both MSSA and MRSA. None of the isolates were detected as VRSA. The major factors associated with nasal colonization of S. aureus were close personal contact, current smoking habit, and working or living in a farm (p < 0.05).

Conclusion

Regular surveillance and monitoring of MRSA nasal carriage and antibiotic susceptibility pattern are of prime importance in controlling S. aureus infections especially in high risk groups like HIV-infected patients.

Characterization of Heterogeneous MRSA and MSSA with Reduced Susceptibility to Chlorhexidine in Kuwaiti Hospitals

The objective of this investigation was to identify the lineages of MRSA and MSSA with reduced susceptibility to chlorhexidine in Kuwaiti hospitals. 121 clinical MRSA and 56 MSSA isolates were included in this study. Antimicrobial susceptibility testing was performed for a selection of agents including chlorhexidine and resistance genes were amplified and sequenced. PFGE, spa typing, and MLST were completed for a selection of isolates. The results showed SCCmec II, III, IV, and V were present in 0.8, 21.5, 69.4, and 8.3% of the MRSA isolates. agr-1Sa was the most prevalent type in both MSSA (48%) and MRSA (54%). Forty-five percentage of MRSA contained pvl and 39% contained lukE-lukD, however, as many as 86% of MSSA contained pvl and 96.4% contained lukE-lukD. qac A-C genes were identified in 12.3% of MRSA, norA was present in 82.6% and blaZ in 94.2%. Among MSSA only 5.4% harbored qacA, 83% contained norA, and 91% blaZ. Multi-drug resistant ST239/t945 lineage containing a qac gene was the most identified S. aureus. However, other lineages, including ST772-MRSA-V/t4867/pvl(+)qacC/smr and non-qac harboring lineages of ST217-MRSAIV/t3244/pvl(-), ST34-MSSA/t161/pvl(+), ST5-MSSA/t688/pvl(+), ST5-MSSA/t4867/norA(+), and ST672-MSSA/t003/pvl(-), also showed reduced susceptibility to chlorhexidine. The observed reduced susceptibility of non-qac dependent MSSA isolates to chlorhexidine suggests the involvement of other elements in promoting higher MBC (≥30 mg/L). Our results confirm that monitoring MSSA is essential as they may have the potential to survive low level biocide exposure.

Genomic diversity and antimicrobial susceptibility profiling of nasal carriage Staphylococcus aureus isolated from pediatric ward in Western Iran

Nasal carriage of Staphylococcus aureus (S. aureus) probably causes the transmission of infection between individuals in hospital and community. This study aimed to evaluate the molecular epidemiology and antibiotic resistance pattern of nasal carriage S. aureus in pediatric ward patients and personnel. A total of 122 Nasal samples were taken from 28 personnel and 94 hospitalized patients in the pediatric ward. Minimum Inhibitory Concentration (MIC) to vancomycin and cefoxitin was determined by Agar dilution method strips. All S. aureus isolates were analyzed by pulsed-field gel electrophoresis (PFGE). A total of 41 S. aureus were isolated from the patients. 16 isolates (39.09%) were hospital-associated S. aureus (HA-SA) and 25 (60.97%) were community-associated S. aureus (CA-SA); also, 13 S. aureus isolates were obtained from the personnel. Based on MIC results, all of S. aureus isolates were susceptible to vancomycin, and in 41 patient isolates, 13 isolates (31.7%) were resistant to cefoxitin (MRSA). Of 13 S. aureus isolates of the personnel, 3 (23%) isolates were MRSA. Totally 11 common clones and 13 single clones were obtained. In conclusion the prevalence of CA-SA in the ward was higher than that of HA-SA. In the strains obtained from a hospital ward, there was a high epidemiology, genotypic diversity in the studied ward. However, horizontal transfer of S. aureus was observed between patients and between personnel and patients, which indicated the risk of transmission of resistant strains in the hospital wards.

Characteristics and risk factors of hospital acquired - Methicillin-resistant Staphylococcus aureus (HA-MRSA) infection of pediatric patients in a tertiary care hospital in Riyadh, Saudi Arabia

Background and objectives

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infections has been steadily increasing. These infections are considered to be either hospital-acquired MRSA (HA-MRSA) or community-acquired MRSA (CA-MRSA). Children are at higher risk of infection than adults. HA-MRSA has been reported to have more serious outcomes than CA-MRSA. However, there are not enough studies in Saudi Arabia to study the characteristics of HA-MRSA in children. We aim to describe the characteristics of HA-MRSA infection, including risk factors, culture site, clinical manifestations, complications, and outcomes among pediatric patients in a tertiary care hospital in Riyadh, Saudi Arabia.

Design and settings

This is a retrospective chart review study. It was conducted in King Abdulaziz medical city in Riyadh.

Patients and methods

The study included all patients 14 years of age or younger who were culture-positive from any site in the body during the period from January 1, 2009 to December 31, 2011. The time of culture compared to admission time was used to differentiate between CA-MRSA (within 72 h of admission) and HA-MRSA (more than 72 h after admission). The final sample size was 39 patients.

Results

We found HA-MRSA to be more common in males and those with risk factors such as previous surgery and previous hospitalization. Patients had a high Pediatric intensive care unit (PICU) admission rate and were commonly septic with positive blood cultures. Seventy-four percent of patients fully recovered, 10% recovered with complications and 15% died.

Conclusion

HA-MRSA is an infection that can cause serious complications and a high rate of PICU admissions. Clinical manifestations such as shock are associated with higher mortality and morbidity rates. Special care should be given to those admitted to PICU, as they have high rates of mortality and morbidity.

Vancomycin modifies the expression of the agr system in multidrug-resistant Staphylococcus aureus clinical isolates

Staphylococcus aureus is an opportunistic pathogen that colonizes human hosts and causes a wide variety of diseases. Two interacting regulatory systems called agr (accessory gene regulator) and sar (staphylococcal accessory regulator) are involved in the regulation of virulence factors. The aim of this study was to evaluate the effect of vancomycin on hld and spa gene expression during the exponential and post-exponential growth phases in multidrug-resistant (MDR) S. aureus.

Methods: Antibiotic susceptibility was evaluated by the standard microdilution method. The phylogenetic profile was obtained by pulsed-field gel electrophoresis (PFGE). Polymorphisms of agr and SCCmec (staphylococcal cassette chromosome mec) were analyzed by multiplex polymerase chain reaction (PCR). The expression levels of hld and spa were analyzed by reverse transcription-PCR. An enzyme-linked immunosorbent assay (ELISA) was performed to detect protein A, and biofilm formation was analyzed via crystal violet staining.

Results: In total, 60.60% (20/33) of S. aureus clinical isolates were MDR. Half (10/20) of the MDR S. aureus isolates were distributed in subcluster 10, with >90% similarity among them. In the isolates of this subcluster, a high prevalence (100%) for the agrII and the cassette SCCmec II polymorphisms was found. Our data showed significant increases in hld expression during the post-exponential phase in the presence and absence of vancomycin. Significant increases in spa expression, protein A production and biofilm formation were observed during the post-exponential phase when the MDR S. aureus isolates were challenged with vancomycin.

Conclusion: The polymorphism agrII, which is associated with nosocomial isolates, was the most prevalent polymorphism in MDR S. aureus. Additionally, under our study conditions, vancomycin modified hld and spa expression in these clinical isolates. Therefore, vancomycin may regulate alternative systems that jointly participate in the regulation of these virulence factors.