Methicillin Resistant Staphylococci Isolated from Goats and Their Farm Environments in Saudi Arabia Genotypically Linked to Known Human Clinical Isolates: a Pilot Study.

We conducted a pilot whole genome sequencing (WGS) study to characterize the genotypes of nine methicillin resistant staphylococci (MRS) isolates recovered from goats and their farm environments in Eastern Province, Saudi Arabia, between November 2019 to August 2020. Seven out of nine isolates were methicillin resistant Staphylococcus aureus (MRSA), and two were methicillin resistant Staphylococcus epidermidis (MRSE). All MRSA isolates possessed genotypes previously identified to infect humans, including isolates harboring ST6-SCCmec IV-t304 (n = 4), ST5-SCCmec VI- t688 (n = 2) and ST5-SCCmec V-t311 (n = 1). 2 MRSA isolates possessed plasmids that were genetically similar to those identified in S. aureus isolates recovered from humans and poultry. In contrast, plasmids found in three MRSA isolates and one MRSE isolate were genetically similar to those recovered from humans. All MRSA isolates harbored the host innate modulate genes sak and scn previously associated with human infections. The genotypes of MRSE isolates were determined as ST35, a well-known zoonotic sequence type and ST153, which has been associated with humans. However, the MRSE isolates were untypeable due to extra ccr complexes identified in their SCCmec elements. Moreover, we identified in ST153 isolate SCCmec element also harbored the Arginine Catabolic Mobile Element (ACME) IV. All MRS isolates were phenotypically resistant to trimethoprim-sulfamethoxazole, an antibiotic for the decolonization of MRS. Three isolates carried antibiotic resistance genes in their SCCmec elements that were not previously described, including those encoding fusidic acid resistance (fusC) and trimethoprim resistance (dfrC) incorporated in the MRSA SCCmec VI. IMPORTANCE Our findings demonstrate a possible cross-transmission of methicillin resistant staphylococci between goats and their local environments and between goats and humans. Due to ever increasing resistance to multiple antibiotics, the burden of MRS has a significant impact on livestock farming, public health, and the economy worldwide. This study highlights that implementing a holistic approach to whole genome sequencing surveillance in livestock and farm environments would aid our understanding of the transmission of methicillin resistant staphylococci and, most importantly, allow us to implement appropriate infection control and hygiene practices.

Characterization of SCCmec, spa types and Multi Drug Resistant of methicillin-resistant Staphylococcus aureus isolates among inpatients and outpatients in a referral hospital in Shiraz, Iran.

OBJECTIVES: Molecular typing such as spa typing is used to control and prevent Staphylococcus aureus widespread in hospitals and communities. Hence, the aim of this study was to find the most common types of S. aureus strain circulating in Shiraz via spa and SCCmec typing methods. RESULTS: Total of 159 S. aureus isolates were collected from two tertiary hospitals in Shiraz. Isolates were identified by biochemical tests. Antimicrobial susceptibility tests were performed by standard disk diffusion method and then genetic analysis of bacteria was performed using SCCmec and spa typing. In this study 31.4% of the isolates were methicillin-resistant S. aureus. The majority of isolates were SSCmec type III. Spa type t030 was the most prominent type among MRSA strains. For the first time in Iran, spa003, t386, t1877, t314, t186, t1816, t304, t325, t345 were reported in this study. It was shown that there is a possibility that these spa types are native to this region. Our findings showed that SCCmec II, III and IV disseminate from hospital to community and vice versa. Thus, effective monitoring of MRSA in hospital and community is necessary.

Clonal change of methicillin-resistant Staphylococcus aureus isolated from patients with impetigo in Kagawa, Japan.

Recently, the USA300 clone, which is a Panton-Valentine leukocidin (PVL)-positive clonal complex 8-staphylococcal cassette chromosome mec type IV (CC8-IV) community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strain, emerged in community and hospital settings in Japan. Hence, clonal types of CA-MRSA strains are predicted to be changing. Nonetheless, long-term surveillance of CA-MRSA has not been conducted in Japan. Here, we investigated the transition and current status of CA-MRSA strains isolated from outpatients with impetigo; the samples were collected between 2007 and 2016 in Kagawa, Japan. The detection rate (22.8%, 488/2139 strains) of MRSA slightly decreased in these 10 years. Molecular epidemiological analyses showed that the prevalence of the CC89-II clone, which is a typical CA-MRSA genotype of causative agents of impetigo, significantly decreased from 48.0% (48/100 strains) in 2007-2009 to 21.9% (16/73 strains) in 2013-2016. By contrast, a non-USA300 CC8-IV clone, which is a highly pathogenic CA-MRSA/J clone, significantly increased in prevalence from 9.0% (9/100 strains) to 32.9% (24/73 strains). The prevalence of PVL-positive CA-MRSA strains increased annually from 2012 (0%) to 2015 (6.7%), whereas only one of these strains turned out to be the USA300 clone. Antibiotic susceptibility data revealed that the rates of resistance to gentamicin and clindamycin among CA-MRSA strains decreased along with the decreased prevalence of the CC89-II clone and increased prevalence of the CA-MRSA/J clone. Our data strongly suggest that the clonal types and antibiotic susceptibility of CA-MRSA isolated from patients with impetigo dramatically changed during the last 10 years in Japan.

Antimicrobial Susceptibility and Enterotoxin-Encoding Genes in Staphylococcus spp. Recovered from Kitchen Equipment from a University Hospital in Rio de Janeiro, Brazil.

This study was conducted to determine the occurrence of antimicrobial resistance and enterotoxin-encoding genes (EEGs) in Staphylococcus spp. recovered from equipment used to prepare hospital meals, in a university hospital in Rio de Janeiro, Brazil. Sixty samples were collected from semi-industrial equipment (one blender and one mixer) in the hospital's kitchen. Resistance genes and SCCmec types were detected by PCR. From the 40 isolates of Staphylococcus spp. identified, 8 were Staphylococcus aureus. Thirty-two (80%) Staphylococcus spp. isolates were resistant to at least one antimicrobial agent. Resistance genetic determinants were detected: erm gene (Staphylococcus epidermidis [n = 2]; Staphylococcus hominis [n = 1]), mecA gene (S. epidermidis [n = 2]), and aa(6')-aph(2'') gene (Staphylococcus caprae [n = 1], S. epidermidis [n = 2], S. hominis [n = 1], Staphylococcus pausteri [n = 1], Staphylococcus simulans [n = 1], and Staphylococcus warneri [n = 1]). The presence of at least one EEG in 83% (n = 33) of the isolates was identified. Two strains of S. epidermidis were methicillin-resistant S. epidermidis (MRSE) and harboring SCCmec type IV. Staphylococcus spp. contaminated some hospital kitchen's equipment, indicating that hygiene procedures should be improved. Results also indicate that meals can be a vehicle to disseminate multiresistant Staphylococcus spp., including MRSE, and Staphylococcus with EEGs.

Comparative Genomics Study of Staphylococcus epidermidis Isolates from Orthopedic-Device-Related Infections Correlated with Patient Outcome.

Staphylococcus epidermidis has emerged as an important opportunistic pathogen causing orthopedic-device-related infections (ODRI). This study investigated the association of genome variation and phenotypic features of the infecting S. epidermidis isolate with the clinical outcome for the infected patient. S. epidermidis isolates were collected from 104 patients with ODRI. Their clinical outcomes were evaluated, after an average of 26 months, as either "cured" or "not cured." The isolates were tested for antibiotic susceptibility and biofilm formation. Whole-genome sequencing was performed on all isolates, and genomic variation was related to features associated with "cured" and "not cured." Strong biofilm formation and aminoglycoside resistance were associated with a "not-cured" outcome (P = 0.031 and P < 0.001, respectively). Based on gene-by-gene analysis, some accessory genes were more prevalent in isolates from the "not-cured" group. These included the biofilm-associated bhp gene, the antiseptic resistance qacA gene, the cassette chromosome recombinase-encoding genes ccrA and ccrB, and the IS256-like transposase gene. This study identifies biofilm formation and antibiotic resistance as associated with poor outcome in S. epidermidis ODRI. Whole-genome sequencing identified specific genes associated with a "not-cured" outcome that should be validated in future studies. (The study has been registered at ClinicalTrials.gov with identifier NCT02640937.).

The effect of antimicrobial photodynamic therapy on the expression of novel methicillin resistance markers determined using cDNA-AFLP approach in Staphylococcus aureus.

BACKGROUND: Widespread methicillin resistant Staphylococcus aureus (MRSA) and absence of effective antimicrobial agents has led to limited therapeutic options for treating MRSA infection. We aimed to evaluate the effect of antimicrobial photodynamic therapy (aPDT) on the expression of novel identified methicillin resistance markers (NIMRMs) in S. aureus using complementary DNA-Amplified Fragment Length Polymorphism (cDNA-AFLP) approaches to address the therapeutic alternatives for MRSA infections. MATERIALS AND METHODS: We used cDNA-AFLP to compare MRSA and methicillin susceptible S. aureus (MSSA) for identification of target genes implicated in methicillin resistance. To determine the sub-lethal aPDT (sPDT), MRSA and MSSA clinical isolates photosensitized with toluidine blue O (TBO), and then were irradiated with diode laser. After sPDT, the colony forming units/mL was quantified. Antimicrobial susceptibility against methicillin was assessed for cell-surviving aPDT. Effects of sPDT on the expression of NIMRMs were evaluated by real-time quantitative reverse transcription PCR. RESULTS: According to our results, serine hydrolase family protein (Shfp) encoding gene and a gene encoding a conserved hypothetical protein (Chp) were implicated in methicillin resistance in MRSA. sPDT reduced the minimum inhibitory concentrations of methicillin by 3-fold in MRSA. sPDT could lead to about 10- and 6.2- fold suppression of expression of the Chp and Shfp encoding genes, respectively. CONCLUSION: sPDT would lead to reduction in resistance to methicillin of MRSA in surviving cells by suppressing the expression of the Shfp and Chp encoding genes associated with methicillin resistance. This may have potential implications of aPDT for the treatment of MRSA infections.

Investigation and Treatment of Fusidic Acid Resistance Among Methicillin-Resistant Staphylococcal Isolates from Egypt.

Methicillin resistance among staphylococci isolated from patients in northern Egypt has escalated alarmingly in the past decade. Data about the prevalence of fusidic acid (FA) resistance in Egyptian clinical isolates are limited. This work investigates the prevalence and mechanism of FA resistance among 81 methicillin-resistant staphylococcal isolates from major hospitals of Alexandria, Egypt. Some combinations for treating infections due to resistant isolates were studied. Twenty-six isolates (32.1%) were FA resistant (minimum inhibitory concentrations [MICs] = 2-1,024 µg/ml), and fusB and fusC genes coding for FA resistance were detected in 30.77% and 34.62% of the FA-resistant strains, respectively. One highly resistant isolate, S502 (MIC = 1,024 µg/ml), possessed both genes. Plasmid curing resulted in fusB loss and MIC decrease by 16-64 folds. Conjugation caused acquisition of FA resistance among susceptible isolates. Serial passages in subinhibitory FA concentrations produced mutants with increased MIC by 4-32 folds. The combination of FA with rifampin, gentamicin, or ampicillin/sulbactam, in a subinhibitory concentration, was synergistic against the isolates, including serial passage mutants, decreasing number of survivors by an average of 2-4 logs. A relatively moderate rate of FA resistance was detected in Alexandria hospitals. Combination therapy with gentamicin, rifampin, or ampicillin/sulbactam is crucial to preserve the effectiveness of FA.

Methicillin resistance & inducible clindamycin resistance in Staphylococcus aureus.

BACKGROUND & OBJECTIVES: Methicillin resistant Staphylococcus aureus (MRSA) isolates with inducible clindamycin resistance (iCR) are resistant to erythromycin and sensitive to clindamycin on routine testing and inducible clindamycin resistance can only be identified by D-test. This study was aimed to detect methicillin resistance and iCR among S. aureus isolates, effectiveness of some commonly used antibiotics and correlation between methicillin resistance and iCR. METHODS: The present cross-sectional study included 46 S. aureus isolates subjected to Kirby-Bauer's disk diffusion method for antibiotic susceptibility testing (AST) to estimate MRSA and resistance to some commonly used antibiotics. D-test was employed to detect iCR. RESULTS: Eleven of the 46 (23.9%) isolates tested were MRSA. Overall, 19 (41.3%) isolates showed of iCR. Vancomycin and linezolid were found to be 100 per cent effective. A positive Karl-Pearson's coefficient of correlation (0.89) between methicillin resistance and iCR was obtained. INTERPRETATION & CONCLUSIONS: Detection of iCR is important for the use of clindamycin in MRSA infections. Methicillin resistance and iCR appear to be clinically unrelated.

Ultrastructural cell wall characteristics of clinical gentamycin-resistant Staphylococcus aureus isolates.

The frequent use of gentamycin (GM) ointment for the treatment of skin infections has led to an increase in the number of GM-resistant clinical isolates of Staphylococcus aureus. We examined the ultrastructural characteristics of 14 clinical strains of S. aureus by transmission electron microscopy. Seven of these isolates were GM-resistant, and seven isolates were GM-sensitive. We found that the cell wall of GM-resistant strains (32.24 ± 5.99 nm) was significantly thicker than that of GM-sensitive strains (19.02 ± 2.72 nm). We genetically characterized these isolates by polymerase chain reaction, targeting the genes for three aminoglycoside-modifying enzymes, aac(6')-aph(2''), aph(3')-III, and ant(4')-I. All GM-resistant strains tested carried the gene encoding aac(6')-aph(2''). However, we were unable to establish a link between a specific gene and cell wall thickening, because one GM-resistant strain was also positive for aph(3')-III. We also demonstrated that a GM-resistant mutant strain, derived in vitro from a GM-sensitive S. aureus parent strain (209P), also exhibited a thickened cell wall. These results strongly suggest that a thickened cell wall is a common ultrastructural characteristic of GM-resistant S. aureus clinical strains.

Methicillin-resistant Staphylococcus aureus (MRSA) detected at four U.S. wastewater treatment plants.

BACKGROUND: The incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections is increasing in the United States, and it is possible that municipal wastewater could be a reservoir of this microorganism. To date, no U.S. studies have evaluated the occurrence of MRSA in wastewater. OBJECTIVE: We examined the occurrence of MRSA and methicillin-susceptible S. aureus (MSSA) at U.S. wastewater treatment plants. METHODS: We collected wastewater samples from two Mid-Atlantic and two Midwest wastewater treatment plants between October 2009 and October 2010. Samples were analyzed for MRSA and MSSA using membrane filtration. Isolates were confirmed using biochemical tests and PCR (polymerase chain reaction). Antimicrobial susceptibility testing was performed by Sensititre® microbroth dilution. Staphylococcal cassette chromosome mec (SCCmec) typing, Panton-Valentine leucocidin (PVL) screening, and pulsed field gel electrophoresis (PFGE) were performed to further characterize the strains. Data were analyzed by two-sample proportion tests and analysis of variance. RESULTS: We detected MRSA (n = 240) and MSSA (n = 119) in 22 of 44 (50%) and 24 of 44 (55%) wastewater samples, respectively. The odds of samples being MRSA-positive decreased as treatment progressed: 10 of 12 (83%) influent samples were MRSA-positive, while only one of 12 (8%) effluent samples was MRSA-positive. Ninety-three percent and 29% of unique MRSA and MSSA isolates, respectively, were multidrug resistant. SCCmec types II and IV, the pvl gene, and USA types 100, 300, and 700 (PFGE strain types commonly found in the United States) were identified among the MRSA isolates. CONCLUSIONS: Our findings raise potential public health concerns for wastewater treatment plant workers and individuals exposed to reclaimed wastewater. Because of increasing use of reclaimed wastewater, further study is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated wastewater.

Antibiotic treatments of a methicillin-resistant Staphylococcus pseudintermedius infection in a dog: a case presentation.

We report the antibiotic treatments administered to a female dog with mastitis and successive pyoderma. Microbiological investigations allowed the identification of Staphylococcus pseudintermedius after 54 days of various antibiotic treatments. The isolate carried the mecA gene and was resistant to 9 of 15 tested antibiotics. Consistent antibiotic treatment of the infection was possible only after accurate microbiological diagnosis.

Methicillin and aminoglycoside resistance in Staphylococcus aureus isolates from bovine mastitis and sequence analysis of their mecA genes.

Although methicillin-resistant Staphylococcus aureus (MRSA) were generally isolated from human beings; these agents were recently isolated from various animal species. It has been shown that MRSA isolates are not only resistant to beta-lactam antibiotics, but can also be resistant to the other commonly used antibiotics. In this study, 18 phenotypic methicillin resistant S. aureus isolates from bovine mastitis cases were analyzed by PCR for the presence of mecA gene encoding methicillin resistance and aac (6')/aph(2″), aph(3')-IIIa and ant(4')-Ia genes encoding aminoglycoside resistance. Out of 18 S. aureus isolates (oxacillin MICs, ≥4 µg/ml), 3 were positive for mecA gene. Only one from 3 mecA positive isolates was positive for genes encoding aminoglycoside-modifying enzymes and this isolate carried aac(6')/aph(2″) in combination with aph(3')-IIIa gene. The aph(3')-IIIa gene was detected in 3 isolates. These three isolates carrying the aminoglycoside-modifying enzyme genes were resistant to gentamicin, kanamycin and neomycin. The mecA gene of 3 MRSA isolates was sequenced. All three mecA genes of these isolates were identical to that found in human MRSA strains, except a one-base substitution at nucleotide position 757. From the data presented in this study, it can be concluded that MRSA isolated from bovine mastitis may be originated from human beings, but further studies are needed to investigate the possibility of zoonotic transfer of MRSA.

Clinical features, epidemiology, antimicrobial resistance, and exotoxin genes (including that of Panton-Valentine leukocidin) of gentamicin-susceptible methicillin-resistant Staphylococcus aureus (GS-MRSA) isolated at a paediatric teaching hospital in New South Wales, Australia.

AIMS: To describe the epidemiological, clinical, and laboratory features of gentamicin-susceptible methicillin-resistant Staphylococcus aureus (GS-MRSA) seen at a paediatric teaching hospital. METHODS: Patients from whom GS-MRSA was isolated between 1 January 2001 and 31 December 2002 were enrolled. Retrospective chart review was performed. Susceptibility testing was performed with the Vitek2 system; PCR confirmed methicillin resistance. Phage typing and pulsed field gel electrophoresis (PFGE) was performed (utilising MLST/SCCmec-defined control strains). PCR detection of tst, luk-PV, and entA-entE was performed. RESULTS: Eighty-five per cent of all Staphylococcus aureus isolates during the study period were methicillin-sensitive, and 15% were MRSA (9% GS-MRSA, 6% gentamicin resistant-MRSA). 100 GS-MRSA infections in 98 children were identified: 59 cases of skin/soft tissue, four bone and joint, four surgical site infections, three pneumonia, eight other types, and 22 represented colonisation. Ninety-nine isolates were non-multidrug resistant, but 17 strains were resistant to erythromycin, 7 to tetracyclines, 12 to ciprofloxacin, 11 to fusidic acid, 1 each to rifampicin and mupirocin. 44 isolates were Oceania strain (ST30-MRSA-IV), 20 were Queensland strain (ST93-MRSA-IV), ten were UK EMRSA-15 (ST22-MRSA-IV), eight were WA MRSA-1 (ST1-MRSA-IV), two were WA MRSA-5 (ST8-MRSA-IV), one was WA MRSA-2 (ST78slv-MRSA-IV), one was WA MRSA-15 (ST59-MRSA-IV), and the remainder were sporadics. Twenty patients were Pacific Islanders, of whom 12 had the Oceania strain; ten were Aboriginal, of whom eight had the Queensland strain. Sixty-eight isolates possessed luk-PV, including all Queensland strains and 91% of Oceania strains. Enterotoxin genes were detected in 25% of the isolates, and tst was detected in four isolates. CONCLUSIONS: GS-MRSA is a significant paediatric problem in New South Wales: two minority groups are over-represented, multiple epidemic strains were detected, most community strains possess luk-PV, and many isolates are multidrug resistant.

Effect of Saliva miltiorrhiza bunge on antimicrobial activity and resistant gene regulation against methicillin-resistant Staphylococcus aureus (MRSA).

This study was conducted in an effort to evaluate the antimicrobial activity and antibiotic-resistant gene regulation from Saliva miltiorrhiza Bunge on methicillin-resistant Staphylococcus aureus (MRSA). A variety of solvent fractions and methanol extracts of S. miltiorrhiza Bunge were tested in order to determine its antimicrobial activities against S. aureus and MRSA. As a result, the hexane fraction of S. miltiorrhiza Bunge evidenced the highest levels of antimicrobial activity against S. aureus and MRSA. The MICs of the hexane fraction against various MRSA specimens were 64

Lack of horizontal gene transfer of methicillin-resistance genetic determinants from PBP2a-positive, coagulase-negative staphylococci to methicillin-sensitive Staphylococcus aureus using transcutaneous electrical nerve stimulation (TENS).

Previous research shows that approximately half of the coagulase-negative staphylococci (CNS) isolated from patients in the intensive care unit (ICU) at Belfast City Hospital were resistant to methicillin. The presence of this relatively high proportion of methicillin-resistance genetic material gives rise to speculation that these organisms may act as potential reservoirs of methicillin-resistance genetic material to methicillin-sensitive Staphylococcus aureus (MSSA). Mechanisms of horizontal gene transfer from PBP2a-positive CNS to MSSA, potentially transforming MSSA to MRSA, aided by electroporation-type activities such as transcutaneous electrical nerve stimulation (TENS), should be considered. Methicillin-resistant CNS (MR-CNS) isolates are collected over a two-month period from a variety of clinical specimen types, particularly wound swabs. The species of all isolates are confirmed, as well as their resistance to oxacillin by standard disc diffusion assays. In addition, MSSA isolates are collected over the same period and confirmed as PBP2a-negative. Electroporation experiments are designed to mimic the time/voltage combinations used commonly in the clinical application of TENS. No transformed MRSA were isolated and all viable S. aureus cells remained susceptible to oxacillin and PBP2a-negative. Experiments using MSSA pre-exposed to sublethal concentrations of oxacillin (0.25 microg/mL) showed no evidence of methicillin gene transfer and the generation of an MRSA. The study showed no evidence of horizontal transfer of methicillin resistance genetic material from MR-CNS to MSSA. These data support the belief that TENS and the associated time/voltage combinations used do not increase conjugational transposons or facilitate horizontal gene transfer from MR-CNS to MSSA.

Methicillin-resistant S. aureus infections among patients in the emergency department.

BACKGROUND: Methicillin-resistant Staphylococcus aureus (MRSA) is increasingly recognized in infections among persons in the community without established risk factors for MRSA. METHODS: We enrolled adult patients with acute, purulent skin and soft-tissue infections presenting to 11 university-affiliated emergency departments during the month of August 2004. Cultures were obtained, and clinical information was collected. Available S. aureus isolates were characterized by antimicrobial-susceptibility testing, pulsed-field gel electrophoresis, and detection of toxin genes. On MRSA isolates, we performed typing of the staphylococcal cassette chromosome mec (SCCmec), the genetic element that carries the mecA gene encoding methicillin resistance. RESULTS: S. aureus was isolated from 320 of 422 patients with skin and soft-tissue infections (76 percent). The prevalence of MRSA was 59 percent overall and ranged from 15 to 74 percent. Pulsed-field type USA300 isolates accounted for 97 percent of MRSA isolates; 74 percent of these were a single strain (USA300-0114). SCCmec type IV and the Panton-Valentine leukocidin toxin gene were detected in 98 percent of MRSA isolates. Other toxin genes were detected rarely. Among the MRSA isolates, 95 percent were susceptible to clindamycin, 6 percent to erythromycin, 60 percent to fluoroquinolones, 100 percent to rifampin and trimethoprim-sulfamethoxazole, and 92 percent to tetracycline. Antibiotic therapy was not concordant with the results of susceptibility testing in 100 of 175 patients with MRSA infection who received antibiotics (57 percent). Among methicillin-susceptible S. aureus isolates, 31 percent were USA300 and 42 percent contained pvl genes. CONCLUSIONS: MRSA is the most common identifiable cause of skin and soft-tissue infections among patients presenting to emergency departments in 11 U.S. cities. When antimicrobial therapy is indicated for the treatment of skin and soft-tissue infections, clinicians should consider obtaining cultures and modifying empirical therapy to provide MRSA coverage.

An extract from teak (Tectona grandis) bark inhibited Listeria monocytogenes and methicillin resistant Staphylococcus aureus.

AIMS: The aim of this study was to characterize the inhibitory mechanism in teak (Tectona grandis) bark and to determine its effectiveness against Listeria monocytogenes and methicillin resistant Staphylococcus aureus (MRSA). METHODS AND RESULTS: Methanol extracts of teak bark were inhibitory to L. monocytogenes and MRSA by means of disc diffusion. Gas chromatography-mass spectrometry, and (1)H and (13)C nuclear mass resonance analyses revealed that the inhibitory compound had a molecular weight of 174, and a structure of 5-hydroxy-1,4-naphthalenedione (Juglone). CONCLUSIONS: 5-hydroxy-1,4-naphthalenedione (Juglone) inhibited L. monocytogenes and MRSA. SIGNIFICANCE AND IMPACT OF THE STUDY: A compound in an extract of teak bark was inhibitory to L. monocytogenes and MRSA.

Activity of medicinal plant extracts against hospital isolates of methicillin-resistant Staphylococcus aureus.

Aqueous and ethanolic extracts of ten traditional Thai medicinal plants were investigated for their ability to inhibit 35 hospital isolates of methicillin-resistant Staphylococcus aureus (MRSA). Nine medicinal plants displayed activity against all isolates tested. Ethanolic extracts of Garcinia mangostana, Punica granatum and Quercus infectoria were most effective, with MICs for MRSA isolates of 0.05-0.4, 0.2-0.4 and 0.2-0.4 mg/mL, respectively, and for S. aureus ATCC 25923 of 0.1, 0.2 and 0.1 mg/mL, respectively. MBCs for MRSA isolates were 0.1-0.4, 1.6-3.2 and 0.4-1.6 mg/mL, and for S. aureus ATCC 25923 were 0.4, 3.2 and 1.6 mg/mL, respectively.