Distribution of mecA among methicillin-resistant clinical staphylococcal strains isolated at hospitals in Naples, Italy

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.

Discrepancies between phenotypic and genotypic identification methods of antibiotic resistant genes harboring Staphylococcusaureus

Antimicrobial resistance is a global issue that limits therapeutic options for infections. S. aureus being a member of the ESKAPE group is capable of "escaping" the biocidal action of antimicrobial agents. There are phenotypic and genotypic methods used for the identification of antibiotic resistant genes harboring S. aureus but these methods do not always show concordant results. To address these discrepancies, a total of 335 equine nasal swab samples from four districts of Punjab were collected using a convenient sampling technique. These samples were first subjected to common microbial techniques to identify S. aureus. The disc diffusion assay was performed for the phenotypic identification of antibiotic resistant S. aureus by using discs of oxacillin, penicillin, vancomycin, gentamycin, and tetracycline. After this, PCR was performed by targeting mecA, blaZ, vanB, aaca-aphd, and tetK genes for genotypic identification of respective antibiotic-resistant S. aureus. Phenotypic discrepancies (number of antibiotic resistant isolates found from disc diffusion who appeared to be negative for the resistant gene), and genotypic discrepancies (number of antibiotic sensitive isolates found from disc diffusion who appeared to be positive for the resistant gene) were calculated. The discrepancy ratio for mecA, blaZ, vanB, aaca-aphd, and tetK genes were 3.09, 1.96, 2.67, 1.93, and 1.67 respectively. These discrepant results indicate that the absence or presence of only one gene is not a true marker of resistant or sensitive isolates. There are multiple resistance determinants and resistance mechanisms. This study also highlighted the phenomenon of silencing of antibiotic resistance determinants.

Evidence and Molecular Characterization of Multidrug Resistant Staphylococcus aureus Isolated From Equines in Pakistan

The purpose of the current study was to investigate the nasal colonization and drug resistance profile of Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), and vancomycin-resistant S. aureus (VRSA) in donkeys (n =63), mules (n = 42), and horses (n = 98). MRSA and VRSA were confirmed based on phenotypic and molecular methods, followed by phylogenetic analysis. Furthermore, the association of various animal and management-based risk factors with S. aureus colonization was also evaluated. The presence of nuc gene on polymerase chain reaction showed an overall prevalence of 42.86% of S. aureus in equines. Based on Kirby-Bauer disc diffusion test, 26.44% of isolates showed resistance to vancomycin. Further, mecA and vanB genes were targeted which showed an overall 14.94% and 13.79% prevalence of methicillin and vancomycin-resistant isolates, respectively. The phylogenetic analysis revealed a significant variation of the study isolates with each other and with already reported sequences of mecA and vanB genes. Risk factor analysis revealed that raising purpose (P = .011), work intensity (P < .001), stocking density (P = .006), presence of other livestock animals in surroundings (P = .043), and common drinking water source (P = .023) as significant. Antimicrobial susceptibility testing of MRSA and VRSA isolates showed high resistance to various commonly used antibiotics. Furthermore, all the tested isolates showing resistance to three or more than three antibiotics were considered multiple drug-resistant. The current study manifests the molecular evidence of MRSA and VRSA isolated from equines in Pakistan which will help to address the emerging issue of multidrug resistance in S. aureus in equines and emphasizes the need for possible measures to tackle this issue.

Molecular evidence of β-lactam resistant Staphylococcus aureus in equids with respiratory tract infections: Frequency and resistance modulation strategy

The emergence of antimicrobial-resistant strains in Staphylococcus aureus (β-lactam and methicillin-resistant) is an overwhelming issue worldwide. Using the purposive sampling technique, 217 equids samples were collected from district Layyah which were subjected to culturing followed by genotypic identification of mecA and blaZ genes by PCR. This study revealed that by phenotypic methods, a prevalence of 44.24%, 56.25%, and 47.92% was found for S. aureus, MRSA, and β-lactam resistant S. aureus in equids. While genotypically, MRSA was found in 29.63% and β-lactam resistant S. aureus in 28.26% of equids. In-vitro antibiotic susceptibility testing against S. aureus isolates harboring both mecA and blaZ genes showed a high resistance against Gentamicin (75%), followed by Amoxicillin (66.67%) and Trimethoprim+sulfamethoxazole (58.34%). In an attempt to re-sensitize the resistant bacteria to antibiotics, a combination of antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) was used which revealed synergistic effect of Gentamicin and Trimethoprim+sulfamethoxazole with Phenylbutazone; and Amoxicillin with Flunixin meglumine. Analysis of risk factors revealed significant association with the S. aureus-associated respiratory infection in equids. Phylogenetic analysis of mecA and blaZ genes showed a high resemblance of study isolate's sequences with each other and variable resemblance with already reported isolates obtained from different samples of neighboring countries. This study reports the first molecular characterization and phylogenetic analysis of β-lactam and methicillin resistant S. aureus in equids in Pakistan. Moreover, this study will help in the resistance modulation of resistant antibiotics (Gentamicin, Amoxicillin, Trimethoprim+sulfamethoxazole) and provide a good insight into planning an effective therapeutic regime.

Drug repurposing strategy: An emerging approach to identify potential therapeutics for treatment of bovine mastitis

The current study was designed to characterize methicillin-resistant Staphylococcus aureus (MRSA) isolated from bovine milk, along with its response to antibiotics, and ultimately reverse its mechanism of resistance by modulation with non-antibiotics. The synergistic combination of antibiotics with NSAIDs were tested in-vivo by giving MRSA challenge to rabbits. The current study reported an overall 23.79% prevalence of MRSA. The BLAST alignment of current study sequences revealed 99% similarity with mecA gene of MRSA from NCBI database. The current study isolates were more similar to each other and also with reference sequences as compared to other mecA gene sequences from Turkey, India, and Russia. Antibiogram of MRSA isolates showed a highly resistant response to cefoxitin, amoxicillin, and gentamicin. Amoxicillin, gentamicin, tylosin, vancomycin, and ciprofloxacin elicited a significant response (p < 0.05) in combination with non-antibiotics against tested MRSA isolates. The highest zone of inhibition (ZOI) increase was noted for vancomycin in combination with flunixin meglumine (145.45%) and meloxicam (139.36%); gentamicin with flunixin meglumine (85.71%) and ciprofloxacin with ivermectin (71.13%). Synergistic behavior was observed in the combination of gentamicin with ketoprofen; sulfamethoxazole and oxytetracycline with meloxicam. Hematological analysis showed significant differences (p < 0.05) among lymphocyte count and bilirubin. On histopathological examination of skin tissue, hyperplasia of epithelium, sloughed off epidermis, hyperkeratosis, infiltration of inflammatory cells, and hemorrhages were observed. The highest cure rate was observed in case of gentamicin in combination with ketoprofen as compared to other treatment groups. The current study concluded antibiotics in combination with non-antibiotics as potential therapeutic agents for resistance modulation against MRSA. This study will help to devise treatment and control strategies against bovine mastitis. Although the prospect of using NSAIDs to manage infections caused by MRSA appears to be a promising direction, further studies should be conducted to test these medications using suitable in-vivo models in controlled clinical trials to justify their repurposing as a treatment for MRSA infections.

Prevalence, antimicrobial susceptibilities and risk factors of Methicillin resistant Staphylococcus aureus (MRSA) in dairy bovines

Staphylococcus aureus is a common mastitis pathogen in dairy cows, and methicillin-resistant S. aureus (MRSA) has been found in dairy farms all over the world. The study carried out on bovines from three governorates in Egypt, with the goal of determining the prevalence of MRSA in positive milk samples of subclinical mastitis, performing an antibiotic susceptibility test against MRSA isolates and determining the risk factors associated with MRSA. A total of 350 quarter milk samples (n = 200 mixed breed cow; n = 150 water buffalo) were collected and examined for subclinical mastitis using the California mastitis test (CMT) before being exposed to standard microbiological procedures for S. aureus isolation. The disc diffusion method was used to phenotypically analyse the positive S. aureus isolates for MRSA, which was verified by a PCR assay targeting the mecA gene. According to the findings of the study, 41.4% (145/350) milk samples were positive based on CMT, while 35.7% (125/350) of positive samples identified as MRSA based on PCR assay. However, the obtained results revealed non-significant disparity between cattle and buffalo and all predicted risk factors were strongly associated with prevalence of subclinical mastitis. The in-vitro antibiotic susceptibility test revealed that cefoxitin was completely resistant, whereas linezolid, ciprofloxacin, and trimethoprim + sulphamethoxazole were sensitive against the MRSA isolates. The relevance of S. aureus to public health, as well as the development of resistance to antibiotics like methicillin, needs ongoing testing of antimicrobial medications against MRSA isolates.

Methicillin-Resistant Staphylococcus aureus (MRSA): One Health Perspective Approach to the Bacterium Epidemiology, Virulence Factors, Antibiotic-Resistance, and Zoonotic Impact

Methicillin-resistant Staphylococcus aureus (MRSA) is a major human pathogen and a historically emergent zoonotic pathogen with public health and veterinary importance. In humans, MRSA commonly causes severe infectious diseases, including food poisoning, pyogenic endocarditis, suppurative pneumonia, otitis media, osteomyelitis, and pyogenic infections of the skin, soft tissues. In the horse, MRSA could cause a localized purulent infection and botryomycosis; in cattle and ewe, localized pyogenic infection and severe acute mastitis with marked toxemia; in sheep, abscess disease resembles caseous lymphadenitis caused by anaerobic strains; in dogs and cats, pustular dermatitis and food poisoning; in pig, exudative epidermatitis “greasy pig disease; in birds, MRSA causes bumble-foot. The methicillin resistance could be determined by PCR-based detection of the mecA gene as well as resistance to cefoxitin. In Egypt, MRSA is one of the important occasions of subclinical and clinical bovine mastitis, and the prevalence of MRSA varies by geographical region. In this review, we are trying to illustrate variable data about the host susceptibility, diseases, epidemiology, virulence factors, antibiotic resistance, treatment, and control of MRSA infection.

Antibiotic susceptibility profile and synergistic effect of non-steroidal anti-inflammatory drugs on antibacterial activity of resistant antibiotics (Oxytetracycline and Gentamicin) against methicillin resistant Staphylococcus aureus (MRSA)

Non-steroidal anti-inflammatory drugs (NSAIDs) may exhibit antibacterial activity and have synergistic effects with antibiotics. One way to re-sensitize MRSA to resistant antibiotics is by combining with approved non-antibiotics. The study was intended to explore susceptibility of MRSA to various antibiotics and non-antibiotics (NSAIDs) by micro dilution broth method. MRSA isolates were confirmed by PCR (mecA gene) and in-vitro antibiotic susceptibility was determined by disc diffusion tests. Combinations of NSAIDs with resistant antibiotics were also evaluated in in-vivo trial in mice. In-vitro antibiotic susceptibility profile presented 100% resistance to Cefoxitin, 37.5% to Gentamicin and Amikacin, 25% to Oxytetracycline, 12.5% to Tylosin, Fusidic acid and Vancomycin, while Ciprofloxacin, Levofloxacin, Moxifloxacin, Trimethoprim + Sulfamethoxazole and Linezolid were found sensitive. Synergistic effect was observed when resistant antibiotics (Oxytetracycline/Gentamicin) were combined with sensitive antibiotics (Ciprofloxacin/Linezolid). Combination of Non-antibiotics (NSAIDs) with resistant antibiotics revealed that Meloxicam showed partial synergism with both Oxytetracycline and Gentamicin, while Flunixin Meglumine presented synergistic effect with Oxytetracycline and partial synergism with Gentamicin. Diclofenac Sodium revealed additive effect with Oxytetracycline while in case of Gentamicin indifferent effect was observed. In-vivo results showed that combinations of Oxytetracycline with Meloxicam/Flunixin Meglumine and Gentamicin with Meloxicam/Flunixin Meglumine were effective. The study concluded that the resistance against milk borne zoonotic MRSA infections can be successfully addressed by combining resistant antibiotics with NSAIDs. Flunixin Meglumine can be used in combination with oxytetracycline against MRSA infection.

Emerging discrepancies in conventional and molecular epidemiology of methicillin resistant Staphylococcus aureus isolated from bovine milk

Methicillin resistant Staphylococcus aureus (MRSA) is an emerging public health concern from dairy milk, and its diagnosis by phenotypic methodology is experiencing higher discrepancies. The present study was planned to estimate discrepancies in phenotypic identification of MRSA and MSSA (Methicillin sensitive Staphylococcus aureus) in relation to mecA, and prevalent risk factors from various localities. In-vitro oxacilline antibiotic disks were used for phenotypic identification of MRSA, whereas mecA gene was used as MRSA marker in Staph aureus by PCR. Total of 900 bovine milk samples from private and public farms located in district Faisalabad using convinent sampling technique were collected. Potential risk factors for MRSA prevalence identified by non-parametric statistical tests were compared among different subdistricts. Discrepancy in MRSA was calculated as percentage of mecA negative strains while that of MSSA was determined as percentage of mecA positive strains. Molecular identification presented 17.97% (55/306) of discrepancy in MRSA in terms of negative mecA strains from district Faisalabad while sub-district Faisalabad, sub-district Jaranwala, and sub-district Samundary presented 13.98% (13/93), 18.28% (17/93), and 20.83% (25/120) discrepant results, respectively. On the other hand, 29.1% (55/189) of discrepancy in MSSA in terms of mecA positive strains from MSSA isolates was noted. MSSA results were more discrepant than that of MRSA. Hence discrepancy ratio of MSSA over MRSA was noted to be 1.53, 1.50, and 1.21 from tehsil Faislabad, Samundary, and Jaranwala. Tick infestation, lactation stage, frequency of milking, dirty milker's hands, unhygienic milking procedures, and higher use of beta lactam of antibiotics were risk factors that were prevalent in increasing order from sub-district Faisalabad > Jaranwala > Samundary. The study concluded higher prevalence of MRSA in bovine milk samples, and found remarkable discrepancies in phenotypic and genotypic identification which demand immediate attention to tackle exacerbation in resistance patterns.

Antibiotic susceptibilities and prevalence of Methicillin resistant Staphylococcus aureus (MRSA) isolated from bovine milk in Pakistan

The study was designed to investigate bovine milk for prevalence of an emerging zoonotic pathogen Methicillin resistant Staphylococcus aureus (MRSA), and in-vitro therapeutic response of various antibiotics against MRSA. Nine hundred (900) milk samples were collected (half from cattle and half from buffalo) from private and public farms located in various tehsils of district Faisalabad, using the convenient sampling method. Milk samples were put to biochemical identification of Staphylococcus aureus and later oxacilline disk sensitivity testing for confirmation of MRSA. The MRSA isolates were confirmed by PCR targeting mecA gene in Staphylococcus aureus. The study found 34% prevalence of MRSA in overall bovine milk from district Faisalabad with 30% and 38% prevalence in cattle and buffalo, respectively. Tehsil Samundari presented comparatively higher MRSA prevalence followed by tehsil Jaranwala and tehsil Faisalabad. However, there was non-significant difference of MRSA prevalence between cattle and buffalo, and among different tehsils. All assumed risk factors except specie were significantly associated with mastitis spread. The in-vitro drug trial against MRSA from buffalo milk presented 100% efficacy of Ciprofloxcin, Moxifloxacin, Linezolid, and Trimethoprim plus Sulphamethoxazole combination, followed by Gentamicin and Levofloxacin presenting 90%, and Amikacin becoming 80% efficacious against MRSA from buffalo milk. The MRSA isolates of cattle milk presented similar pattern with some variations of higher susceptibility against Oxytetracycline, and Fusidic acid. The conclusion of the study states uniform prevalence of MRSA in cattle and buffalo milk in study area having assumed risk factors positively associated with disease spread, while Ciprofloxcin, Moxifloxacin, Linezolid, and Trimethoprim plus Sulphamethoxazole drugs showed the highest efficacy to combat this pathogen.

Usefulness of Multiplex Real-Time PCR for Simultaneous Pathogen Detection and Resistance Profiling of Staphylococcal Bacteremia

Staphylococci are the leading cause of nosocomial blood stream infections. Fast and accurate identification of staphylococci and confirmation of their methicillin resistance are crucial for immediate treatment with effective antibiotics. A multiplex real-time PCR assay that targets mecA, femA specific for S. aureus, femA specific for S. epidermidis, 16S rRNA for universal bacteria, and 16S rRNA specific for staphylococci was developed and evaluated with 290 clinical blood culture samples containing Gram-positive cocci in clusters (GPCC). For the 262 blood cultures identified to the species level with the MicroScan WalkAway system (Siemens Healthcare Diagnostics, USA), the direct real-time PCR assay of positive blood cultures showed very good agreement for the categorization of staphylococci into methicillin-resistant S. aureus (MRSA), methicillin-susceptible S. aureus (MSSA), methicillin-resistant S. epidermidis (MRSE), methicillin-susceptible S. epidermidis (MSSE), methicillin-resistant non-S. epidermidis CoNS (MRCoNS), and methicillin-susceptible non-S. epidermidis CoNS (MSCoNS) (κ = 0.9313). The direct multiplex real-time PCR assay of positive blood cultures containing GPCC can provide essential information at the critical point of infection with a turnaround time of no more than 4 h. Further studies should evaluate the clinical outcome of using this rapid real-time PCR assay in glycopeptide antibiotic therapy in clinical settings.

High incidence of oxacillin-susceptible mecA-positive Staphylococcus aureus (OS-MRSA) associated with bovine mastitis in China

Staphylococcus aureus is a main cause of bovine mastitis and a major pathogen affecting human health. The emergence and spread of methicillin-resistant Staphylococcus aureus (MRSA) has become a significant concern for both animal health and public health. This study investigated the incidence of MRSA in milk samples collected from dairy cows with clinical mastitis and characterized the MRSA isolates using antimicrobial susceptibility tests and genetic typing methods. In total, 103 S. aureus isolates were obtained from dairy farms in 4 different provinces in China, including Gansu, Shanghai, Sichuan, and Guizhou. Antimicrobial susceptibility testing of these isolates revealed that the resistance rates to penicillin and sulfamethoxazole were high, while the resistance rates to ciprofloxacin and vancomycin were low. Among the 103 isolates, 49 (47.6%) were found to be mecA-positive, indicating the high incidence of MRSA. However, 37 of the 49 mecA-positive isolates were susceptible to oxacillin as determined by antimicrobial susceptibility assays and were thus classified as oxacillin-susceptible mecA-positive S. aureus (OS-MRSA). These isolates could be misclassified as methicillin susceptible Staphylococcus aureus (MSSA) if genetic detection of mecA was not performed. Molecular characterization of selected mecA-positive isolates showed that they were all negative with Panton-Valentine leukocidin (PVL), but belonged to different spa types and SCCmec types. These results indicate that OS-MRSA is common in bovine mastitis in China and underscore the need for genetic methods (in addition to phenotypic tests) to accurately identify MRSA.