In vitro activities of antimicrobials against six important species of gram-negative bacteria isolated from raw milk samples in Korea.
Gram-negative bacteria (GNB) with multidrug resistance pose a serious threat to public health. They are environmental pathogens frequently isolated from raw milk and mastitis in dairy cattle. This study was to examine the in vitro antimicrobial activities against 225 isolates belonging to six important species of GNB from mastitic raw milk samples of dairy herds in the Republic of Korea: Acinetobacter baumannii (n = 17), Citrobacter freundii (n = 19), Enterobacter cloacae (n = 54), Klebsiella pneumoniae (n = 55), Pseudomonas aeruginosa (n = 45), and Serratia marcescens (n = 35). In general, amikacin, gentamicin, and piperacillin exhibited strong antimicrobial activities against all bacterial species tested, whereas rifampin, cephalothin, cefazolin, and ampicillin were ineffective against most of the bacterial species tested. Wide differences were observed in the patterns of resistance among the bacterial species; in particular, resistance to kanamycin, streptomycin, tetracycline, and chloramphenicol was highly variable among the strains belonging to different bacterial species. Almost half of the GNB isolates (45.3%, 102/225) were resistant to 5 or more of 12 antimicrobial agents tested: P. aeruginosa (86.6%, 39/45) showed the highest resistance rate, followed by S. marcescens (65.7%, 23/35). This study indicates that multiple antimicrobial resistances are prevalent among GNB isolates from mastitic milk samples of dairy cattle in the Republic of Korea.
Nam
Hyang-Mi
HM
Bacteriology and Parasitology Division, National Veterinary Research and Quarantine Service, Anyang City, Gyeonggi-do, Republic of Korea. namhm@nvrqs.go.kr
Lim
Suk-Kyung
SK
Kim
Jong-Man
JM
Joo
Yi-Seok
YS
Jang
Keum-Chan
KC
Jung
Suk-Chan
SC
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004305:Dose-Response Relationship, Drug; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy / Q000382:microbiology; D006801:Humans; D007723:Korea; D008414:Mastitis, Bovine / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology*; D015995:Prevalence
D000900:Anti-Bacterial Agents