Carriage And Microbiological Characteristics Of Methicillin-resistant Staphylococcus Aureus From Urban Rodent-like Animals In Guangzhou And Xiamen

ObjectiveStaphylococcus aureus(S.aurceus),especially methicillin-resistant Staphylococcus aureus(MRSA),is a leading pathogen of hospital-and community-associated infectious disease throughout the world.The aims of this study were(1)to investigate the carrier rate and antimicrobial resistance of S.aureus and MRSA isolates from urban rodent-like animals in parts of Guangzhou and Xiamen;(2)to compare and analyze the profiles of antimicrobial resistance,the carriage of virulence genes and human immune evasion cluster genes(IEC genes)and the genotype of MRSA isolates from different origins(rodent-like animals and patients).We hope that these data would help to understand relationships of MRSA isolates from urban rodent-like animals and patients.Methods1)Urban rodent-like animals were captured in Baiyun District and Yuexiu District in Guangzhou city and four districts in Xiamen city in Southern China between June,2015 and May,2016.Oropharynx swabs of each animal were subsequently collected.S.aureus was isolated and identified by using biochemical and molecular approaches.2)Antimicrobial susceptibility of S.aureus isolates was tested to obtain resistance phenotype.3)MRSA isolates were determined by the result of antimicrobial susceptibility to cefoxitin and the carriage of specific resistant gene(mecA gene).4)MRSA isolates from patients were collected in Baiyun district of Guangzhou in the same period.Genes of Panton-Valentine Leukocidin(PVL)and human immune evasion cluster(IEC)were detected by using PCR.Spa typing and MLST were performed to study the genotype of MRSA isolates from rodent-like animals and patients according to the protocol described on the website.The relationships of MRSA isolates from rodent-like animals and humans were compared.Results1)Between June,2015 and May,2016,a total of 620 urban rodent-like animals(including 424murine and 196 shrews)were trapped for the presence of S.aureus.Rattus norvegicus and Suncus murinus were dominant species among all rodent-like animals trapped.2)In total,147 S.aureus isolates were retrieved.The carrier rate of S.aureus was 23.7%.In addition,S.aureus isolate was detected in nearly all species trapped.Of all S.aureus isolates,the rate of resistance to penicillin was the highest(46.3%),followed by azithromycin(19.4%),tetracycline(9.5%)and cefoxitin(6.1%).The rates of resistance to clindamycin,rifampin,ciprofloxacin,chloramphenicoland nitrofurantoin were all less than 5%.All of S.aureus isolates were susceptible to trimethoprim/sulfamethoxazole,minocycline,gentamicin and vancomycin.One isolate of methicillin-susceptible S.aureus was resistant to linezolid.The multidrug resistance rate of S.aureus was 12.9%.3)A total of 14 MRS A isolates were detected in 620 samples.The carrier rate of MRSA was 2.3%.Of all 14 MRSA isolates,11 isolates were detected from Rattus norvegicus in Baiyun District of Guangzhou,one was detected from suncus murinus in Baiyun District,another two isolates were detected from Rattus tanezumi and Rattus losea trapped in Xiamen.MRSA was not detected from all samples collected from Yuexiu District.Of all 14 MRSA isolates,the rate of resistance to p-lactams(penicillin/cefoxitin)was 71.4%,followed by azithromycin(28.6%),clindamycin(28.6%),tetracycline(28.6%),rifampin(14.3%)and ciprofloxacin(7.2%).4)Eight MRSA isolates from patients in hospital located in Baiyun-monitoring point were retrieved.The rates of resistance to ?-lactams(penicillin/cefoxitin)and azithromycin were 87.5%(7/8).The resistant rates to clindamycin,tetracycline,ciprofloxacin and gentamycin were 50%(4/8).One MRSA isolate was resistant to trimethoprim/sulfamethoxazole.Two isolates were intermediate to minocycline.All of MRSA isolates were susceptible to linezolid,nitrofurantoin and vancomycin.5)Eight spa types were detected from 14 MRSA isolates in rodent-like animals.The highest frequence of spa type was t437 and t15965,followed by t2582,t034,t127,t011,t4652 and t116,among which t15965 was the new spa type.Eight different spa types were detected among 8 MRSA isolates from patients,including t116,t030,t037,t437,t558,t213,t002 and t1406.The isolates t116 and t437 wre the mutual spa type between rodent-like animals and humans.6)Eight sequence types(STs)were detected from 14 MRSA isolates in rodent-like animals by MLST.The dominant type was ST398,followed by ST59,ST1243,ST45,ST1232,ST1,ST338 and the new type ST3323.Seven STs were detected from 8 human MRSA isolates,among which ST45,ST59 and ST398 were the mutual STs.Conclusions1)The prevalence of MRSA isolates in urban rodent-like animals was 2.3%,of which the carrier rate was highest in Rattus norvegicus.The carriage of MRSA in Suncus murinus,Rattus tanezumi and Rattus losea was not reported before.2)S.aureus isolates from rodent-like animals got a more moderate drug resistance than those from humans or pigs in other study,which was probably associated with the less connection between antibiotics and rodent-like animals in urban environment.However,one methicillin-susceptible S.aureus was resistant to linezolid,which need to be concerned.3)The profiles of drug resistance of MRSA isolates from rodent-like animals were similar with those from humans.There were overlapping genotpyes between MRSA isolates from rodent-like animals and humans.The results of molecular characterizations,including the carriage of PVL gene and IEC genes,and the genotypes of MRSA isolates suggested that MRSA isolates in urban rodent-like animals might play a role in the circulation of MRSA isolates among animals,environment and humans.