Methicillin-resistant S. Aureus Isolates Research Articles

Genomic characterization of Staphylococcus aureus isolated from patients admitted to intensive care units of a tertiary care hospital: epidemiological risk of nasal carriage of virulent clone during admission.

We conducted a molecular epidemiological study of Staphylococcus aureus using whole-genome sequence data and clinical data of isolates from nasal swabs of patients admitted to the intensive care unit (ICU) of Hiroshima University hospital. The relationship between isolate genotypes and virulence factors, particularly for isolates that caused infectious diseases during ICU admission was compared with those that did not. The nasal carriage rates of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) in patients admitted to the ICU were 7.0% and 20.1%, respectively. The carriage rate of community-acquired (CA)-MRSA was 2.3%, accounting for 32.8% of all MRSA isolates. Whole-genome sequencing analysis of the MRSA isolates indicated that most, including CA-MRSA and healthcare-associated (HA)-MRSA, belonged to clonal complex (CC) 8 [sequence type (ST) 8] and SCCmec type IV. Furthermore, results for three disease foci (pneumonia, skin and soft tissue infection, and deep abscess) and the assessment of virulence factor genes associated with disease conditions [bacteremia, acute respiratory distress syndrome (ARDS), disseminated intravascular coagulopathy (DIC), and septic shock] suggested that nasal colonization of S. aureus clones could represent a risk for patients within the ICU. Particularly, MRSA/J and MSSA/J may be more likely to cause deep abscess infection; ST764 may cause ventilation-associated pneumonia, hospital-acquired pneumonia and subsequent bacteremia, and ARDS, and tst-1-positive isolates may cause DIC onset.IMPORTANCENasal colonization of MRSA in patients admitted to the intensive care unit (ICU) may predict the development of MRSA infections. However, no bacteriological data are available to perform risk assessments for Staphylococcus aureus infection onset. In this single-center 2-year genomic surveillance study, we analyzed all S. aureus isolates from nasal swabs of patients admitted to the ICU and those from the blood or lesions of in-patients who developed infectious diseases in the ICU. Furthermore, we identified the virulent clones responsible for causing infectious diseases in the ICU. Herein, we report several virulent clones present in the nares that are predictive of invasive infections. This information may facilitate the design of preemptive strategies to identify and eradicate virulent MRSA strains, reducing nosocomial infections within the ICU.

Study of the sensitivity of methicillin-resistant <i>Staphylococcus aureus</i> to antibiotics and bacteriophage preparations

   Objective. To evaluate the sensitivity of methicillin-resistant Staphylococcus aureus strains to antibiotics and therapeutic and prophylactic preparations of bacteriophages.   Materials and methods. The antibiotic sensitivity of strains of methicillin-resistant S.aureus was studied by the disco-diffusion method, the determination of the minimum inhibitory concentrations of vancomycin and linezolid by broth microdilution method, and ceftaroline by E-tests. The sensitivity of methicillin-resistant S.aureus to bacteriophage preparations was studied.   Results. It has been established that linezolid and vancomycin are quite active drugs against methicillin-resistant S.aureus (MRSA), however, resistance to them begins to develop. MRSA resistance to fluoroquinolones and cefoxitin was the highest of all antibiotics tested; the results obtained with cefoxitin can be interpreted for other cephalosporins (except ceftaroline) and all penicillins. Only 67.9% of MRSA strains retained sensitivity to ceftaroline, but ceftaroline-resistant strains had low levels of minimal inhibitory concentration. The preparations of the bacteriophages “Sextaphage” and “Piobacteriophage Phagio” showed their lytic activity only in relation to 35.8% and 18.9% of MRSA isolates, respectively.   Conclusion. Monitoring the development of antibiotic resistance in methicillin-resistant S.aureus is an important part of the strategy of rational antibiotic therapy for staphylococcal infections. Only taking into account the preliminary step-by-step determination of the phage sensitivity of the causative agent of the disease, bacteriophage preparations can be considered as a completely possible alternative to antibiotics for the treatment of purulent inflammatory diseases caused by MRSA.

Antimicrobial Resistance and the Prevalence of the Panton-Valentine Leukocidin Gene among Clinical Isolates of Staphylococcus aureus in Lithuania.

This study aimed to determine resistance to antimicrobials of Staphylococcus aureus strains isolated from clinical specimens in Lithuanian hospitals and to identify the genes conferring resistance and virulence. The study was carried out from June 2019 to September 2021. S. aureus strains were isolated from skin, soft tissues, blood, lower respiratory tract, urine and other specimens. Antibiotic susceptibility testing was performed using the disc diffusion method according to EUCAST guidelines. All isolates were analyzed for detection of the ermA, ermC, mecA, mecC, tetK, tetM, and lukF-PV genes by multiplex real-time PCR. The 16S rRNA coding sequence was applied as an internal PCR control. Altogether, 745 S. aureus strains were analyzed. Antimicrobial susceptibility testing revealed that all isolates were susceptible to rifampin and vancomycin. Of the 745 strains, 94.8% were susceptible to tetracycline, 94.5% to clindamycin, and 88.3% to erythromycin. The lowest susceptibility rate was found for penicillin (25.8%). Six percent of the tested strains were methicillin-resistant S. aureus (MRSA). The majority of methicillin-resistant strains were isolated from skin and soft tissues (73.3%), with a smaller portion isolated from blood (17.8%) and respiratory tract (8.9%). The ermC gene was detected in 41.1% of erythromycin-resistant S. aureus strains, whereas ermA was detected in 32.2% of erythromycin-resistant S. aureus strains. 69.2% of tetracycline-resistant S. aureus strains had tetK gene, and 28.2% had tetM gene. 7.3% of S. aureus isolates harbored lukF-PV gene. The frequency of the pvl gene detection was significantly higher in MRSA isolates than in methicillin-susceptible S. aureus isolates (p < 0.0001).

Antibiotic resistance, biofilm formation, and molecular epidemiology of Staphylococcus aureus in a tertiary hospital in Xiangyang, China.

Staphylococcus aureus is a common clinical pathogen that causes various human infections. The aim of this study was to investigate the antibiotic susceptibility pattern, molecular epidemiological characteristics, and biofilm formation ability of S. aureus isolates from clinical specimens in Xiangyang and to analyze the correlation among them. A total of 111 non-duplicate S. aureus isolates were collected from the Affiliated Hospital of Hubei University of Arts and Science. All isolates were tested for antibacterial susceptibility. Methicillin-resistant S. aureus (MRSA) was identified by the mecA gene PCR amplification. All isolates were analyzed to determine their biofilm-forming ability using the microplate method. The biofilm-related gene was determined using PCR. SCCmec, MLST, and spa types of MRSA strains were performed to ascertain the molecular characteristics. Among the 111 S. aureus isolates, 45 (40.5%) and 66 (59.5%) were MRSA and MSSA, respectively. The resistance of MRSA strains to the tested antibiotics was significantly stronger than that of MSSA strains. All isolates were able to produce biofilm with levels ranging from strong (28.9%, 18.2%), moderate (62.2%, 62.1%), to weak (8.9%, 19.7%). Strong biofilm formation was observed in MRSA strains than in MSSA strains, based on percentages. There were dynamic changes in molecular epidemic characteristics of MRSA isolates in Xiangyang. SCCmecIVa-ST22-t309, SCCmecIVa-ST59-t437, and SCCmecIVa-ST5-t2460 were currently the main epidemic clones in this region. SCCmecIVa-ST5-t2460 and SCCmecIVa/III-ST22-t309 have stronger antibiotic resistance than SCCmecIVa-ST59-t437 strains, with resistance to 6 ~ 8 detected non-β-lactam antibiotics. The molecular epidemic and resistance attributes of S. aureus should be timely monitored, and effective measures should be adopted to control the clinical infection and spread of the bacteria.

Occurrence and Characteristics of Toxigenic Staphylococcus aureus in Retail Foods in Iran.

Staphylococcus aureus causes various toxigenic and invasive diseases in humans worldwide. This study examined the prevalence, virulence genes, and antibiotic resistance of S. aureus isolates collected from 894 retail food samples in Ardabil, Iran. Staphylococcal cassette chromosome mec (SCCmec), spa, and multilocus sequence typing methods were employed to further investigate the molecular characteristics of methicillin-resistant S. aureus (MRSA) isolates. The results revealed that 11.18% (n = 100) of food samples exhibited contamination with S. aureus (10.50% methicillin-sensitive S. aureus [MSSA] and 0.67% MRSA). Notably, raw minced meat (29.41%), Faloodeh (25%), and Olivier salad (21.42%) emerged as the most frequently contaminated food items. Among the 100 isolates of S. aureus, 94% were characterized as MSSA, with the remaining 6% identified as MRSA. The highest resistance was observed for penicillin (12%). MRSA isolates exhibited significantly higher resistance rates. Seventy-nine percent of the isolates were positive for sea, 14% for seb, 8% for a sec, and 0% for sed enterotoxin-encoding genes. Sixteen percent of isolates harbored two or more staphylococcal enterotoxin genes, simultaneously. Moreover, 97%, 94%, 24%, and 22% of isolates were positive for hla, hld, tst, and pvl virulence-encoding genes, respectively. No isolate was positive for the exfoliative toxins encoding eta and etb genes. MRSA isolates belonged to CC8 (n = 4) and CC22 (n = 2). Isolates in CC8 belonged to lineage ST239-MRSA-III and spa type t030; the isolates in CC22 belonged to ST22-MRSA-IV and spa types t310 and t223. In conclusion, a relatively high proportion of our retail food samples were contaminated with S. aureus. The high incidence of isolates with toxigenic genes raises serious health concerns. Furthermore, the presence of MRSA lineages linked to humans suggests that retail foods may be contaminated with human origin.

Microbiological analysis of skin and soft tissue infections in children presenting to a paediatric tertiary care centre in Sri Lanka

Introduction: Skin and soft tissue infections (SSTIs) are a common cause of hospitalisation in children. They are diverse in spectrum, ranging from impetigo and abscesses to life threatening necrotising infections. The main pathogens associated with SSTIs are Staphylococccus aureus and Streptococcus pyogenes. Emergence of community acquired methicillin resistant S. aureus (CA-MRSA) is of major concern when antibiotics are required, and it is important to know the prevalence of these pathogens in different geographic locations. This study was done with the aim of identifying and characterising the common bacterial pathogens implicated in SSTIs in children presenting to Sirimavo Bandaranaike Children’s Hospital (SBSCH), Peradeniya, Sri Lanka, which is one of the two paediatric referral hospitals in Sri Lanka.Method: A retrospective, descriptive study analysed data gathered from request forms accompanying pus and tissue sent for culture from patients with SSTIs to the SBSCH microbiology laboratory during a period of 13 months from January 2021 to January 2022.Results: Two hundred and ninety samples were received from suspected SSTIs of which 197 (67.9%) were positive for bacterial growth, with S. aureus present in 163 (83%). Methicillin resistant S. aureus (MRSA) was isolated from 113 (57%) and methicillin sensitive S. aureus (MSSA) from 50 (25%). The frequency of coliforms, Pseudomonas spp., and Group A streptococcus were 31 (16%), 3 (1.5%) and 4 (2%) respectively. Sensitivity of MRSA isolates to cotrimoxazole, clindamycin, ciprofloxacin and erythromycin were 97%, 86%,72% and 29% respectively. Among MSSA isolates, 94% were sensitive to cotrimoxazole, while sensitivity to clindamycin, ciprofloxacin and erythromycin were 74%, 67% and 40% respectively.Conclusion: MRSA was the most frequent pathogen associated with purulent SSTIs in children, followed by MSSA. One fourth of MSSA were resistant to ciprofloxacin and clindamycin. Ciprofloxacin and clindamycin resistance in MRSA was 15% and 28% respectively.

Effect of Bioactive Peptide, KR-12-a5, on Growth of Clinical Methicillin-resistant Staphylococcus aureus Isolates

Staphylococcus aureus is one of the most frequent infectious agents causing hospitals and community associated infections. Developing the treatment for methicillin resistant S. aureus (MRSA) is a challenging arena for effective therapeutics. Application of antimicrobial peptides is an alternative option to control MRSA infection. The potential of the bioactive peptide against MRSA was previously revealed; however, the study on the effect of KR-12-a5 on the various clinical MRSA growth was not elucidated. This study aimed to investigate the effect of bioactive peptide KR-12-a5 on the growth of MRSA isolated from patients. Evaluation of KR-12-a5 peptide using antimicrobial susceptibility test was performed. Antimicrobial activity assay showed that the KR-12-a5 at 2-64 μM could inhibit the growth of S. aureus ATCC 29213 in the range of 55.0±0.8%-81.0±6.2%. In case of KR-12-a5 treatment at 2, 4, and 8 μM, growth of all twenty clinical MRSA isolates could be inhibited less than 90% in the range of 0.0-75.9±1.6%, 0.0-73.0±4.2%, and 0.0-77.1±1.7%, respectively. Whereas the treatment of those at 16, 32, and 64 μM, growth of clinical MRSA could be significantly inhibited more than 90% (p &lt; 0.05) in the range of 94.3±6.7%-100.4±0.4% in 3 isolates (15%), 97.3±0.3%-99.5±0.2% in 4 isolates (20%), and 91.6±0.8%-99.0±0.1% in 9 isolates (45%), respectively. These findings indicated that the KR-12-a5 effectively controls growth of both S. aureus ATCC 29213 and clinical MRSA isolates

Study of Methicillin-resistant Staphylococcus aureus Isolated from Various Clinical Specimens from Tertiary Care Hospital

ABSTRACT Introduction: Staphylococci are Gram-positive bacteria, with a diameter of 0.5–1.5 μm and individual cocci, which are divided in more than one plane from the grape-like cluster. In the genus staphylococci, 32 species and 8 subspecies are present in many of which are present as a commensal in the human body. Staphylococci are frequently found as a normal flora of skin mucosal, surface of respiratory, upper elementary, and urogenital tract of the human body. In immunocompromised condition, the infection can be spread by skin-to-skin contact and also by excretion such as saliva aerosol releasing during sneezing and coughing. Infection of staphylococci may also spread from the animal product such as nonpasteurized milk and milk products. Over the last few decades, Staphylococcus aureus has emerge as the most dangerous organism, which is known as methicillin-resistant S. aureus (MRSA). Some strains show vancomycin resistance by S. aureus in hospitalized patients. The present study was conducted to study the prevalence and antibiogram of MRSA isolates in a clinical sample from Acharya Vinoba Bhave Rural Hospital. Materials and Methods: This study was conducted in the Department of Microbiology at Jawaharlal Nehru Medical College (Datta Meghe Institute of Higher Education and Research), Wardha, from August 2020 to December 2021. The samples received in the microbiology laboratory were inoculated on blood agar and MacConkey’s agar, and incubated for 24 h at 37°C for staphylococcal isolation. A total of 145 Staphylococcal aureus were isolated and confirmed by Gram stain and various biochemical tests such as catalase test, oxidase test, coagulase test, and mannitol salt agar. Antibiotic susceptibility test was examined on the Mueller–Hinton agar plate using the modified Kirby–Bauer disc diffusion method. Screening of methicillin resistant was performed by cefoxitin (30 μg) disc diffusion method and interpreted according to CLSI guideline. Results: The prevalence of MRSA was 76 (52.41%) to methicillin-susceptible S. aureus. The highest MRSA was found in the age group &gt;50 years (26.31%). Out of 76 MRSA isolates from different departments, the medicine and orthopedic departments show maximum MRSA as 19.74% each followed by pediatrics (17.11%) and surgery (13.16). Out of 76 MRSA isolates, vancomycin showed 93.42% sensitivity followed by linezolid (85.52%), Gentamicin (71.05%), tetracycline (56.57%), clindamycin (46.05%), and erythromycin (31.57%). Conclusion: With the advancement of new therapeutic agent, MRSA is also being easily resistant. Due to increasing cases of MRSA, there is an increase in the rate of morbidity and mortality. Moreover, except vancomycin, other drugs are resistant, as their MIC is not in the susceptible range. Thus, the results of this study indicate that vancomycin is a suitable medication to take when MRSA cases rise. In such cases, MRSA can be controlled by regular monitoring and checking the irrational use of antibiotics.

Distribution of Staphylococcus aureus carriage among healthcare workers in a Japanese convalescent and rehabilitation hospital.

Earlobes, nasal cavities, and fingers of 145 healthcare workers in convalescent and rehabilitation hospital (60 nurses and 85 rehabilitation healthcare workers) were sampled. Of the 3 sites sampled, Staphylococcus aureus was detected in one or more sites in 25 nurses and 27 rehabilitation workers. S. aureus was detected in all 3 sites in 2 (8.0%) nurses and 2 (7.4%) rehabilitation workers, and the S. aureus isolates in each case showed related PFGE pattern. S. aureus was detected in both the fingers and nasal cavities of 5 (18.5%) of the rehabilitation healthcare workers; in all 5 cases, the PFGE patterns of the S. aureus isolates from each site belonged to same cluster based on PFGE. Of the 2 cases in which methicillinresistant S. aureus (MRSA) was recovered from earlobes, fingers, and nasal cavities, in both cases, MRSA isolates from the 3 sites were the same clone according to PFGE analysis and SCCmec type IV. As S. aureus was detected in pierced earlobes of nurses, hand hygiene must be practiced after touching pierced earlobes and before patient contact. The same S. aureus clone in the nasal cavity and earlobes indicates that the route of transmission is through the fingers.

Occurrence of high level methicillin resistance Staphylococcus aureus in patients from health facilities in Akwa Ibom State, Nigeria

Background: Methicillin resistant S. aureus (MRSA) has become a major public health predicament worldwide. This is owing to its involvement in the evolution of MDR strains and difficulty in therapeutic management of infected patients. This study was conducted to investigate the prevalence of methicillin resistance Staphylococcus aureus among patients in two health facilities in Akwa Ibom State, Nigeria. Materials and Methods: Clinical isolates of patients from University of Uyo Teaching Hospital (UUTH), Uyo and General Hospital, Ikot Abasi (GHIA) were investigated based on the strategic location of the hospitals. The study design was a descriptive cross-sectional study. Three hundred clinical samples were collected from male and female in and out-patients of all ages and processed using standard bacteriological methods. Detection of Staphylococcus aureus and MRSA strains were done according to standard protocols while antibiotic susceptibility testing of MRSA isolates was conducted using Kirby-Bauer disc diffusion method and interpreted following the CLSI 2021 guidelines. Results: The prevalence of MRSA strains in this study was 42.9%. Majority of patients with MRSA were from UUTH (44%) closely followed by patients from GHIA (40%). High antibiotics resistant rates of MRSA were recorded for ampicillin (96.6%), ciprofloxacin (73.3%), erythromycin (63.3%) and cotrimoxazole (60%). Gentamicin and ceftriaxone sensitivity rates were 53.3% and 63.4%, respectively. Conclusion: Health facilities in the state should institute effective antimicrobial stewardship, intensify surveillance and screening of Staphylococcus aureus for MRSA strains to guard against dissemination of multidrug resistant strains in both hospital and community settings because of the clinical implications.

Kinship analysis of mecA gene of methicillin-resistant Staphylococcus aureus isolated from milk and risk factors from the farmers in Blitar, Indonesia.

There are numerous reports of subclinical mastitis cases in Blitar, which is consistent with the region's high milk production and dairy cattle population. Staphylococcus aureus, which is often the cause of mastitis cases, is widely known because of its multidrug-resistant properties and resistance to β-lactam antibiotic class, especially the methicillin-resistant S. aureus (MRSA) strains. This study aimed to molecular detection and sequence analysis of the mecA gene in milk and farmer's hand swabs to show that dairy cattle are reservoirs of MRSA strains. A total of 113 milk samples and 39 farmers' hand swab samples were collected from a dairy farm for the isolation of S. aureus using Mannitol salt agar. The recovered isolates were further characterized using standard microbiological techniques. Isolates confirmed as S. aureus were tested for sensitivity to antibiotics. Oxacillin Resistance Screening Agar Base testing was used to confirm the presence of MRSA, whereas the mecA gene was detected by polymerase chain reaction and sequencing. A total of 101 samples were confirmed to be S. aureus. There were 2 S. aureus isolates that were multidrug-resistant and 14 S. aureus isolates that were MRSA. The mecA gene was detected in 4/14 (28.6%) phenotypically identified MRSA isolates. Kinship analysis showed identical results between mecA from milk and farmers' hand swabs. No visible nucleotide variation was observed in the two mecA sequences of isolates from Blitar, East Java. The spread of MRSA is a serious problem because the risk of zoonotic transmission can occur not only to people who are close to livestock in the workplace, such as dairy farm workers but also to the wider community through the food chain.

The Changing Epidemiology and Antimicrobial Susceptibility of Staphylococcus aureus Isolated from Blood Cultures in a University Hospital from Argentina.

Staphylococcus aureus bacteremia (SAB) is one of the most common serious bacterial infections worldwide. In this study, we demonstrated changes in SAB epidemiology in an Argentinean University Hospital during an 8-year period (2009-2016). A total of 326 S. aureus clinical isolates were recovered in three periods: P1: 2009-2010, P2: 2012-2014, and P3: 2015-2016. Among these, 127 were methicillin-resistant S. aureus (MRSA) and were characterized by phenotypic and molecular methods. We hereby report a significant decline in multiple drug resistance among MRSA isolates associated with an increase in SCCmec IV between the three periods. A diversity of MRSA-IV clones (mainly ST30-MRSA-IV, ST5-MRSA-IV, and ST8-MRSA-IV) replaced between 2009 and 2016 the previous prevalent MRSA clone causing bloodstream infections at this hospital (ST5-MRSA-I). MRSA population structure continued to diversify between P2 and P3. Notably, ST8-MRSA-IV-t008 related to USA300 was first detected during P2, and ST8-MRSA-IV together with ST30-MRSA-IV related to the Southwest Pacific clone were the more prevalent MRSA genotypes circulating during P3.

Variations In The Genotypic And Phenotypic Characteristics Of Methicillin-Resistant Staphylococcus Aureus (Mrsa) From Students Attending Poultry Farms In Umuahia, Abia State, Nigeria

Staphylococcus aureus causes significant epidemiologic and therapeutic challenges with various skin and soft tissue infections, the main forms of disease manifestation. The public health importance of this organism has been heightened by the emergence and spread of species that are resistant to treatment usually referred to as methicillin-resistant S. aureus (MRSA). This study was carried out to detect mecA and mecC genes in phenotypically determined MRSA isolates. Nasal swab samples of the subjects were cultured on mannitol salt agar and the isolates were identified as S. aureus using a combined morphological and biochemical characteristic. Antibiotic susceptibility profile was performed using the disk diffusion susceptibility method whilst phenotypic detection of MRSA isolates was by Cefoxitin disk diffusion method as per CLSI guidelines. Genomic DNA was extracted from the isolates using commercial kits. The extracted DNA was subjected to multiplex PCR to amplify the 163-bp and 188-bp fragment of the mecA and mecC genes respectively in a Pielter thermal cycler. The susceptibility pattern of MRSA isolates showed that the organisms were highly resistant to Augmentin 29 (93.5%), ceftazidime 18 (58.1%), Streptomycin 19 (76%) whilst high levels of susceptibility were seen for Ofloxacin 27 (87.1%), Levofloxacin 28 (90.3%), and Gentamicin 24 (77.4%). The antibiotic resistance profiles in MRSA isolates were recorded as follows: ciprofloxacin 6 (16.2%), Augmentin 32 (86.4%), erythromycin 13 (35.1%), Ceftazidime 22 (59.4%). Of the 10 MRSA isolates that were subjected to PCR, one isolate was found to harbor the 188-bp of mecC gene whilst mecA was absent from the screened isolates. The detection of mecC MRSA in the present study highlights the diagnostic importance of screening for mecC in mecA negative MRSA. We suggest that surveillance for MRSA should include screening for mecC gene where mecA is not detected in resistant isolates. Stamford Journal of Microbiology, 2023. Vol. 13, Issue 1, p. 6-10

First report on genotypic estimation of MRSA load in udder of nomadic sheep flocks affected with subclinical mastitis in Pakistan

Mastitis is one of the highly devastating issues responsible for production and economic losses in all dairy animals including sheep. This study was designed to investigate subclinical mastitis (SCM) associated with S. aureus in lactating nomadic ewes, along with the associated risk factors analysis. Furthermore, molecular characterization and antibiogram profiling of local methicillin-resistant S. aureus (MRSA) isolates of ovine origin were also performed. A total of 384 milk samples (n = 384) were collected from 13 nomadic sheep flocks using a convenient sampling technique. SCM was evaluated using a Surf Field Mastitis test and the S. aureus was isolated using standard microbiological techniques. Kirby-Bauer disc diffusion assay was used for phenotypic identification of MRSA while the mecA gene was tested through PCR. Study results revealed that SCM was prevalent at 34.37% while S. aureus association was recorded at 39.39%. MRSA prevalence was 36.53% and 21.15% using phenotypic and genotypic tests, respectively. The mecA gene sequences of study isolates showed maximum resemblance with already reported sequences from Pakistan, China, and Myanmar. MRSA isolates showed maximum resistance towards penicillin, ceftriaxone sodium, and trimethoprim + sulphamethoxazole while gentamicin, ciprofloxacin, and tylosin showed maximum efficacy. Risk factors analysis revealed that various flock management, housing, and host-related factors positively influenced the incidence of S. aureus-associated SCM. This study is the first report on the prevalence of S. aureus and MRSA associated with SCM in lactating ewes in Pakistan. This study will help to devise effective treatment and control strategies for S. aureus-associated SCM.

Methicillin-resistant staphylococci in clinical bovine mastitis: occurrence, molecular analysis, and biofilm production.

Staphylococcus aureus is an important pathogen that causes mastitis in cattle, and the emergence of methicillin-resistant S. aureus (MRSA) poses a threat to veterinary and human medicine. The aims of the study were to investigate the prevalence of MRSA and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from clinical mastitis, their ability to form biofilms, and the antimicrobial susceptibility of S. aureus strains. In addition, the Staphylococcal Cassette Chromosome mec (SCCmec) type, spa type and the presence of Panton-Valentine Leucocidin in MRSA were evaluated. A total of 326 staphylococcal strains were screened by multiplex-PCR for S. aureus and Staphylococcus intermedius group (SIG) identification. The S. aureus strains (n = 163) were subjected to phenotypic testing for antimicrobial susceptibility and biofilm formation. Molecular analysis was performed on MRSA mecA-positive strains. Of 163 S. aureus isolates, 142 strains (87.1%) were resistant to at least one antibiotic, and all 19 MRSA strains were resistant to at least four out of five antibiotics tested. All S. aureus strains harboured the icaA gene and were biofilm producers. Nineteen MR-CoNS strains were also isolated. The most prevalent spa types among MRSA were t001 (57.9%) and t037 (31.6%), while one MRSA was type t008 and one was type t041. Most MRSA were SCCmec type I (63.2%) and III (31.6%) and only one strain was type IV. None of the MRSA isolates had the PVL gene. The prevalence of multidrug-resistant S. aureus in bovine mastitis is a serious concern. The finding of MRSA with spa types predominant in humans and infrequent in Italian cows and with SCCmec infrequently found in bovine milk or cheese suggest a human origin of these strains. The ability of MRSA and MR-CoNS involved in bovine mastitis to be transferred to humans and vice versa poses a public health concern.

Molecular and Clinical Features of Heterogeneous Vancomycin-Intermediate Staphylococcus aureus in Tertiary Care Hospitals in South India

Objectives: This study aimed to detect heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) among methicillin-resistant S. aureus (MRSA) isolated from healthcare-associated infections and identify staphylococcal cassette chromosome mec (SCCmec) types. Methods: This study was conducted from February 2019 to March 2020 and included patients admitted in 4 tertiary care hospitals in Karnataka, India. Isolation and identification of MRSA were done using standard bacteriological methods. Antimicrobial susceptibility testing was done using Kirby–Bauer disc diffusion; macrolide-lincosamide-streptogramin B phenotypes were identified using the D test. The minimum inhibitory concentration (MIC) of vancomycin was determined using agar dilution. hVISA were confirmed by the modified population analysis profile-area under the curve test. SCCmec types and the Panton- Valentine leukocidin (pvl) gene were detected using multiplex polymerase chain reaction. Results: Of 220 MRSA stains, 14 (6.4%) were hVISA. None of the MRSA isolates was vancomycin-intermediate or -resistant and all hVISA were susceptible to linezolid and teicoplanin. The macrolide-streptogramin B phenotype was present in 42.9% of hVISA; 92.9% of the hVISA strains had vancomycin MIC in the range of 1–2 μg/mL. Majority of the hVISA and vancomycin-susceptible MRSA were isolated from patients with skin and soft tissue infections. SCCmec III and IV were present in 50% and 35.7% of hVISA, respectively; 14.3% of the hVISA harboured SCCmec V. Conclusion: The prevalence rate of hVISA among MRSA was 6.4%. Therefore, MRSA strains should be tested for hVISA before starting vancomycin treatment. None of the isolates was vancomycin-intermediate or -resistant and all the hVISA strains were susceptible to linezolid and teicoplanin. The majority of the hVISA were isolated from patients with skin and soft tissue infections and harboured SCCmec III and IV. Keywords: MRSA; Hospital Infection; Molecular Typing; Vancomycin; India.

Molecular characterisation of Staphylococcus aureus in school-age children in Guangzhou: associations among agr types, virulence genes, sequence types, and antibiotic resistant phenotypes

BackgroundStaphylococcus aureus, one of the most prevalent opportunistic pathogens, mainly colonizes the nasal cavity and is a risk factor for severe infections. Virulence factors and accessory gene regulator (agr) are key to the severity and diversity of staphylococcal infection. In this study, we aimed to characterise S. aureus agr-types and virulence genes and correlated them with genetic background and antibiotic-resistant phenotypes.ResultsAgr types were identified in 704 isolates (98.5%), with only 11 isolates were negative for agr type. Most of our isolates were classified as agr type I, followed by types III, II and IV. The enterotoxin c gene (sec) was detected in 48.6% of isolates, showing the highest prevalence among the five enterotoxin genes detected. The positivity rates for the lukS/F-PV and tsst genes were 4% and 2.2%, respectively, while neither sed nor SasX were detected. ST45, ST59, ST338, ST188, ST6, ST7, ST22, ST25, ST398, and ST944 belonged to agr I group, while ST5 and ST15 belonged to agr II group. ST30 and ST1 were classified into agr III group, and ST121 was assigned into agr IV group. The tsst gene was found exclusively within agr I and III types belonging to ST7 and ST30 isolates, while the lukS/F-PV was predominantly carried by agr I type isolates primarily within CC59 and CC22 clones. Among the methicillin-resistant S. aureus (MRSA) isolates, 89.7% belonged to agr I group, and 97.8% of rifampicin-resistant or intermediate isolates were assigned to agr I group. MRSA isolates harboured more tested virulence genes compared to methicillin-susceptible S. aureus isolates.ConclusionsWe characterized the distributions of agr types and eight major virulence genes of 715 S. aureus isolates, and our findings revealed clear associations between agr types and STs, as well as virulence genes, and drug resistant phenotypes.

2780. Factors associated with Staphylococcus aureus susceptibility to two lytic bacteriophages; Comparison of phage host susceptibility using a reference set of S. aureus

Abstract Background Timely access is a major concern when considering phage therapy. Using susceptible phage is critical for the outcomes of phage therapy. For timely access to susceptible phages, identifying factors associated with phage susceptibility and building a reference set (RS) to compare host ranges is needed. Methods Phage K, which was a well-documented lytic S. aureus phage, and phage PBSA02, which was a new S. aureus phage from the Korean phage biobank, were used. The efficiency of plating (EOP), the relative activity of phage against specific strain/host strain, and growth kinetics assays were used to determine phage susceptibility. The isolates with high lytic activity (HLA) were defined as susceptible (EOP &amp;gt; 1%). The phage PBSA02 and phage K susceptible groups were compared to the non-susceptible groups to determine the associating factors of phage susceptibility. Results We constructed a methicillin-resistant S. aureus (MRSA) RS using the Australian Group on Antimicrobial Resistance (AGAR) repository. We determined the predominant sequence types (ST) of MRSA in Australia in 2021; ST22 accounted for 90.1% of HA-MRSA and 5 STs for 67.9% of CA-MRSA (figure 1). Then, we randomly selected 39 AGAR MRSA isolates corresponding to each ST from each region in Australia (figure 1). Phage PBSA02 exhibited HLA against 56.4% of the 39 RS isolates, while phage K exhibited HLA against 30.8%. Phage PBSA02 showed HLA against 100% of ST93 and ST30 isolates following ST1 (62.5%), ST22 (37.5%), ST5 (20%) and ST45 (16.7%); phage K showed HLA against 100% of ST30 and 62.5% of ST22 isolates but against none of the ST93 isolates. Phage PBSA02 susceptibility correlated with the ST of MRSA isolates and ciprofloxacin susceptibility (table 1). Isolates from pneumonia/empyema tended to show phage PBSA02 susceptibility (table 1). Phage K susceptibility was also significantly associated with the ST (table 2). Conclusion Our study demonstrated that phage susceptibility was associated with the STs of MRSA, and the RS could be useful for a standardised comparison of the phage host range. Phage PBSA02 with broad susceptibility to the RS could be useful for phage therapy. Further work includes antibiotic synergy testing and resistance mechanism identification in these isolates. Disclosures All Authors: No reported disclosures

Australian Group on Antimicrobial Resistance (AGAR) Australian Staphylococcus aureus Surveillance Outcome Program (ASSOP) Bloodstream Infection Annual Report 2022.

From 1 January to 31 December 2022, fifty-five institutions across Australia participated in the Australian Staphylococcus aureus Surveillance Outcome Program (ASSOP). The aim of ASSOP 2022 was to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that were antimicrobial resistant, with particular emphasis on susceptibility to methicillin and on characterisation of the molecular epidemiology of the methicillin-resistant isolates. A total of 3,214 SAB episodes were reported, of which 77.5% were community-onset. Overall, 15.0% of S. aureus were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 21.4%, which was significantly different to the 16.8% all-cause mortality associated with methicillin-susceptible SAB (p = 0.02). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However, in addition to the β-lactams, approximately 31% of methicillin-resistant S. aureus (MRSA) were resistant to ciprofloxacin; 30% to erythromycin; 13% to tetracycline; 11% to gentamicin; and 2% to co-trimoxazole. One MRSA isolate, with a daptomycin MIC of 1.5 mg/L, harboured the A302V mprF and A23V cls2 mutations. When applying the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints, teicoplanin resistance was detected in one MRSA isolate. Resistance to vancomycin or linezolid was not detected. Resistance to non-β-lactam antimicrobials was largely attributable to the healthcare-associated MRSA (HA-MRSA) clone ST22-IV [2B] (EMRSA-15), and to the community-associated MRSA (CA-MRSA) clone ST45-V [5C2&5] which has acquired resistance to multiple antimicrobials including ciprofloxacin, clindamycin, erythromycin, gentamicin, and tetracycline. The ST22-IV [2B] (EMRSA-15) clone is the predominant HA-MRSA clone in Australia. Nonetheless, 86% of methicillin-resistant SAB episodes were due to CA-MRSA clones. Although polyclonal, approximately 72% of CA-MRSA clones were characterised as ST93-IV [2B] (Queensland clone); ST5-IV [2B]; ST45-V [5C2&5]; ST1-IV [2B]; ST30-IV [2B]; ST97-IV [2B]; ST953-IV [2B]; and ST8-IV [2B]. As CA-MRSA is well established in the Australian community, it is important to monitor antimicrobial resistance patterns in community- and healthcare-associated SAB as this information will guide therapeutic practices in treating S. aureus bacteraemia.

Mupirocin resistance patterns in staphylococcus isolates causing cutaneous and soft-tissue infections: An epidemiological study in a tertiary health-care facility, Dhule, Maharashtra, India

Background: Skin and soft-tissue infections (SSI) caused by Staphylococcus aureus remain a significant concern in both community and hospital settings. Mupirocin resistance among these isolates poses challenges for infection management and control strategies. Aims and Objectives: The aim of this study was to determine the prevalence and patterns of mupirocin resistance among staphylococcus isolates responsible for cutaneous and soft-tissue infections in patients attending a tertiary health-care facility. Along with that, the study investigated into mupirocin resistance prevalence and identified risk factors. Materials and Methods: A prospective study was conducted at a medical college, including 256 non-consecutive staphylococcal isolates from SSI. Antibiotic susceptibility testing was performed using Clinical and Laboratory Standards Institute recommended methods. Mupirocin resistance was determined through disk diffusion testing using 5 μg and 200 μg Mupirocin disks for low-level and high-level resistance, respectively. Results: Among the samples, 16.4% were methicillin-resistant S. aureus (MRSA) and 9.37% were methicillin-resistant coagulase-negative staphylococci. Mupirocin high-level resistance was found in 16.6% of S. aureus isolates, and mupirocin low-level resistance in 19% of MRSA isolates. The prevalence of resistance was lower in inpatient departments compared to outpatient departments. Associations were observed between resistance and patient demographics, history of mupirocin use, surgical site infections, hospitalization history, and diabetes. Conclusion: Mupirocin resistance presents a multifaceted challenge in the context of both patient demographics and clinical settings. The prevalence of resistance was influenced by factors such as patient age, gender, and prior mupirocin usage.