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Green Metal-Based Nanoparticles Synthesized Using Medicinal Plants and Plant Phytochemicals against Multidrug-Resistant Staphylococcus aureus
Published in Richard L. K. Glover, Daniel Nyanganyura, Rofhiwa Bridget Mulaudzi, Maluta Steven Mufamadi, Green Synthesis in Nanomedicine and Human Health, 2021
Abeer Ahmed Qaed Ahmed, Lin Xiao, Tracey Jill Morton McKay, Guang Yang
These MRD bacteria cause numerous infectious diseases and are a global threat. For example, Methicillin-resistant S. aureus causes serious MRSA infections. In addition, other strains of community-acquired methicillin-resistant S. aureus (CA-MRSA) are involved in serious infections of hospital-onset methicillin-resistant S. aureus. MRSA is becoming increasingly resistant to first- and second-line antibiotics, making MRSA infections hard to treat. A major challenge is the unique ability of S. aureus to rapidly develop resistance to antibiotics by developing different resistance mechanisms, including the first discovered penicillin to daptomycin and linezolid (Kaur and Chate, 2015). In the case of MRSA, the resistance developed when methicillin-sensitive S. aureus (MSSA) strains obtained Staphylococcal Cassette Chromosome mec (SCCmec). This carries the mecA gene that encodes the low-affinity penicillin-binding protein (PBP2’ or PBP2a), causing resistance to all of the β-lactam antibiotics, including methicillin (McGuinness et al., 2017; Okwu et al., 2019). The treatment of MRSA infections now uses vancomycin as a last resort, making it the drug of choice to treat severe MRSA infections. It is a glycopeptide antibiotic, inhibiting the biosynthesis of bacterial cell wall (McGuinness et al., 2017).
Staphylococcus aureus
Published in Firza Alexander Gronthoud, Practical Clinical Microbiology and Infectious Diseases, 2020
Methicillin-resistant S. aureus has a PBP2a instead of a PBP2 in its cell wall. This confers resistance to almost all β-lactams including the semisynthetic penicillins, cephalosporins and carbapenems. PBP2a is encoded by the mecA gene. The mecA gene is located in mobile genetic element called staphylococcal cassette chromosome mec (SCCmec). SCCmec also frequently contains resistance genes to other antibiotics including macrolides, clindamycin and tetracycline. MRSA can spread SCCmec to MSSA through horizontal gene transfer.
Role of Bacteria in Urinary Tract Infections
Published in K. Balamurugan, U. Prithika, Pocket Guide to Bacterial Infections, 2019
JebaMercy Gnanasekaran, Kannan Balaji, K. Balamurugan
In 1959, Methicillin was introduced to treat penicillin-resistant S. aureus–related diseases. Methicillin-resistant S. aureus (MRSA) was emerged in the UK around 1961 and spread around European countries and then to Japan, Australia, and the United States. The methicillin-resistance gene (mecA) encodes a methicillin-resistant penicillin-binding protein that is not present in susceptible strains and is believed to have been acquired from a distantly related species. mecA is carried on a mobile genetic element, the staphylococcal cassette chromosome mec (SCCmec), of which four forms have been described that differ in size and genetic composition. Many MRSA isolates are multiresistant and are susceptible only to glycopeptide antibiotics such as vancomycin and investigational drugs. MRSA isolates that have decreased susceptibility to glycopeptides (glycopeptide intermediately susceptible S. aureus [GISA]), reported in recent years, are a cause of great public health concern (Martin et al., 2002). Community-related MRSA is associated with increased disease severity, ranging from cutaneous abscesses to deadly necrotizing pneumonia. USA300 and USA400 are the two dominant CA- MRSA strains. The USA400 strain causes deadly infections but in less frequency, whereas USA300 was widespread and mainly related with community infections and life-threatening infections like necrotizing pneumonia (Wu et al., 2010).
Distribution and antibiotic-resistance of different Staphylococcus species identified by matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) isolated from the oral cavity
Published in Journal of Oral Microbiology, 2021
Katarzyna Garbacz, Maria Wierzbowska, Ewa Kwapisz, Maja Kosecka-Strojek, Marek Bronk, Morteza Saki, Jacek Międzobrodzki
SCCmec is a mobile genetic element consisting of two components, the mec gene complex and the ccr (cassette chromosome recombinase) gene complex. The combination of the genes confers various SCCmec types. SCCmec types I, II and III are predominant in hospital-acquired isolates (HA-MRSA), whereas SCCmec types IV and V are mainly associated with community-acquired isolates (HA-MRSA). SCCmec types IV and V are smaller than SCCmec types I, II and III, which facilitates their mobility and spread [6]. While SCCmec types I, II and III were not identified in the present study, S. aureus and CoNS isolates were shown to harbour SCCmec type IV or V. SCCmec type V was preferentially associated with S. haemolyticus, similar to results demonstrated by Szczuka et al. [30]. No SCCmec type was identified in the case of the four mecA-positive CoNS. These findings are consistent with the results of previous studies in which non-typeable ccr genes were shown to be associated with the heterogeneity of SCCmec elements in methicillin-resistant CoNS strains [31,33].
Novel strategies for rapid identification and susceptibility testing of MRSA
Published in Expert Review of Anti-infective Therapy, 2020
Masako Mizusawa, Karen C Carroll
In addition to rapid detection from nares swabs, molecular assays have also been used to detect MSSA and MRSA directly from skin and skin structure infections. The Xpert MRSA/SA SSTI assay (Cepheid, Inc. Sunnyvale, CA) uses the same single-use cartridge-based disposable system as described above to detect MSSA and MRSA in skin and skin structure infections [152–156]. This assay uses primers and probes to detect sequences within the staphylococcal protein A gene (spa), mecA, and the staphylococcal cassette chromosome (SCCmec) where it inserts into the S. aureus chromosomal attB insertion site. Requiring the latter target along with mecA before reporting a sample as positive for MRSA prevents false positives with mecA ‘dropouts.’ Studies using this version of the test as recommended by the manufacturer and compared to standard or enriched culture reported sensitivities and specificities for S. aureus ranging from 92.2% to 100% and 96.6% to 97.6%, respectively. For MRSA, the reported ranges for sensitivity were 90.9–98.1% and for specificity, the ranges were 96.2-100% [152,154,155]. Combining the use of the Xpert SSTI with an antimicrobial management program, Bouza et al. noted reductions in days of therapy by 2.3 days, reduced treatment costs, length of stay, and related mortality compared to a historical cohort [155].
Important new therapies for methicillin-resistant Staphylococcus aureus
Published in Expert Opinion on Pharmacotherapy, 2019
Matteo Bassetti, Alessia Carnelutti, Nadia Castaldo, Maddalena Peghin
Methicillin-resistant Staphylococcus aureus (MRSA) infections represent a leading cause of infection-related morbidity and mortality worldwide. Originally, MRSA emerged in the 1960s as a cause of nosocomial infections. However, during the 1990s, MRSA became progressively more frequent in community settings [1]. Community-acquired MRSA (CA-MRSA) and hospital-acquired MRSA (HA-MRSA) have traditionally been described to have different epidemiologic profiles and virulence factors, which require distinct clinical management. In particular, CA-MRSA isolates have been described to present with lower rates of resistance to non-β lactam antibiotics when compared to HA-MRSA. Resistance to methicillin is mainly mediated by the mecA gene, which lies on the bacteria’s cassette chromosome mec (SCCmec) and encodes for the penicillin-binding protein 2a (PBP2a). To date, at least 12 SCCmec types have been identified [2]. Among these, SCCmec types I, II, and III have mainly been identified in HA-MRSA and SCCmec types IV and V in community [3]. These differences have been suggested to be responsible for a different resistance profile of CA-MRSA with respect to HA. Overall, CA-MRSA is generally thought to have more susceptibility to trimethoprim-sulfamethoxazole (TMP-SMX), tetracycline, and clindamycin, whereas HA-MRSA strains have generally been resistant to a wider range of antibiotics [4]. Furthermore, according to the classical distinction, CA-MRSA strains encode for certain virulence factors rarely isolated in HA-strains. Among these, it is worth mentioning about Panton-Valentine Leucocidin (PVL), an exotoxin traditionally considered as the culprit factor for CA-MRSA lethality and spreading [5].