Antimicrobial susceptibility patterns of Salmonella isolates from cattle in feedlots

OBJECTIVE: To evaluate the antimicrobial susceptibility patterns of Salmonella isolates from feedlot cattle. DESIGN: Cross-sectional study. SAMPLE POPULATION: 263 Salmonella isolates. PROCEDURES: Fecal samples were collected from the floor of 2 pens in each of 100 feedlots. Two hundred eighty Salmonella isolates were recovered after bacteriologic culture from 38 pens. Of these, 263 isolates were available for antimicrobial susceptibility testing to 16 antimicrobials, using microbroth dilution breakpoint plates. RESULTS: Less than 5% of isolates were resistant to any of the antimicrobials tested, with the exception of sulfamethoxazole (15; 5.7%) and tetracycline (61; 23.2%). Most isolates (197; 74.9%) were susceptible to all antimicrobials tested, whereas 18 (6.8%) were resistant to 2 or more antimicrobials. The percentage of isolates with resistance to any antimicrobial varied by serotype. The percentage of isolates resistant to various antimicrobials was not related to concurrent use of antimicrobials in the feed. CONCLUSIONS AND CLINICAL RELEVANCE: With the exception of tetracycline and sulfamethoxazole, resistance of Salmonella isolates to any of the antimicrobials was uncommon. Most isolates were susceptible to all antimicrobials tested. Antimicrobial resistance was not related to the presence of antimicrobials in the ration being fed at the time of sample collection.     

Antimicrobial susceptibility patterns of respiratory tract pathogens from sheep and goats

OBJECTIVE: To determine the antimicrobial susceptibility of common respiratory tract pathogens from sheep and goats. DESIGN: Cross-sectional study. SAMPLE POPULATION: 41 respiratory tract isolates from sheep and 36 isolates from goats. PROCEDURES: Disk diffusion assay was used to determine antimicrobial susceptibility of isolates to amoxicillin-clavulanic acid, ceftiofur, ciprofloxacin, florfenicol, and tetracycline. Minimum inhibitory concentrations of florfenicol for these isolates were determined by use of the microbroth dilution technique. RESULTS: The most common isolates were Pasteurella multocida (n = 28) and Mannheimia haemolytica (39). All isolates were susceptible to amoxicillin-clavulanic acid, ceftiofur, ciprofloxacin, and florfenicol. Five percent (4/77) of isolates were resistant to tetracycline. CONCLUSIONS AND CLINICAL RELEVANCE: Susceptibility of respiratory tract pathogens isolated from sheep and goats to commonly used antimicrobial drugs in this study was high. Treatment of these species for bacterial respiratory tract disease is likely not complicated by antimicrobial resistance.     

Susceptibility testing of tulathromycin: interpretative breakpoints and susceptibility of field isolates

In vitro susceptibility tests were conducted on bovine and porcine respiratory pathogens isolated from European countries during 2004–2006 for susceptibility to tulathromycin using the recommended methodologies for broth microdilution. The results were compared with data from a similar survey conducted prior to launch in 1998–2001 to monitor for any shift in susceptibility. The importance of maintaining the pH of the culture media within the range 7.2–7.4 was re-affirmed as a key factor in obtaining consistent minimum inhibitory concentration data. The use of recently established interpretative breakpoints would indicate that to date there has been no apparent decrease in susceptibility to tulathromycin since it became widely used across Europe.     

Antimicrobial susceptibility patterns of canine Staphylococcus intermedius isolates from veterinary clinical specimens

Sixty-six Staphylococcus intermedius isolates from canine clinical specimens were tested for susceptibility to various antimicrobial agents by the Bauer-Kirby disk diffusion method and a commercial microdilution system. All isolates were susceptible to cephalothin, cloxacillin, gentamicin, methicillin, and vancomycin. Resistance to ampicillin, penicillin G, and tetracycline was frequent. There was an overall 87% agreement of results from the disk diffusion and microdilution methods for 10 antimicrobial agents. There was greater than or equal to 94% agreement between the 2 methods for 7 antimicrobics; discrepancies were minor.     

Orbital abscess bacterial isolates and in vitro antimicrobial susceptibility patterns in dogs and cats

Objective To determine bacterial populations, in vitro antimicrobial susceptibility patterns, and sources of microorganisms for dogs and cats with orbital abscess. Animals studied In total, 34 dogs and 7 cats with orbital abscess participated in the study. Procedure Medical records of dogs and cats with a clinical diagnosis of orbital abscess, confirmed by cytologic or histopathologic evaluation of orbital specimens, were reviewed from the years 1990 to 2007. Animal signalment, presumptive source of microorganisms and mechanism of orbital introduction, bacterial isolates, and aerobic bacterial in vitro antimicrobial susceptibility test results were recorded. Percentages of susceptible aerobic bacterial isolates were compared among antimicrobials. Results Twenty dogs and five cats had positive culture results. The most frequent bacterial genera isolated from dogs were Staphylococcus, Escherichia, Bacteroides, Clostridium and Pasteurella. The most frequent bacterial genera isolated from cats were Pasteurella and Bacteroides. Aerobic bacterial isolates from dogs had the highest percentage of susceptibility to amikacin, ceftiofur, gentamicin, imipenem, ticarcillin and trimethoprim–sulfamethoxazole. Aerobic bacterial isolates from dogs had the lowest percentage of susceptibility to ampicillin, clindamycin, erythromycin and penicillin. Antimicrobial resistance was uncommon among feline aerobic bacterial isolates. The most commonly identified routes of orbital bacteria introduction were extension from adjacent anatomical structures, penetrating exogenous trauma, and foreign bodies. Conclusions Mixed aerobic and anaerobic bacterial infections of the orbit occur commonly in dogs and cats. On the basis of aerobic and anaerobic bacterial isolates and in vitro susceptibility testing of aerobic bacterial isolates, cephalosporins, extended‐spectrum penicillins, potentiated‐penicillins and carbapenems are recommended for initial antimicrobial therapy of orbital abscess in dogs and cats.     

Antimicrobial susceptibility of Actinobacillus pleuropneumoniae isolates from clinical outbreaks of porcine respiratory diseases

Limited data regarding the susceptibility of Actinobacillus pleuropneumoniae to antimicrobials has been published during recent years. Accordingly, the aim of the present study was to investigate the distribution of MICs for the isolates of A. pleuropneumoniae from diseased pigs in the Czech Republic between 2007 and 2009. A total of 242 isolates were tested for susceptibility to 16 antimicrobial agents by a broth microdilution method. A low degree of resistance was observed for florfenicol (0.8%), amoxicillin and clavulanic acid (0.8%), tilmicosin (1.2%), tiamulin (1.7%) and ampicillin (3.3%), whereas resistance to tetracycline was detected more frequently, 23.9% of isolates. Interestingly, resistance to florfenicol has not yet been reported in any study investigating antimicrobial resistance of A. pleuropneumoniae. By PCR the presence of the floR gene was confirmed in all florfenicol resistant isolates.     

Antimicrobial susceptibility of bacterial isolates from 233 horses with musculoskeletal infection during 1979-1989.

Bacterial culture and susceptibility results were analysed from 233 horses with septic arthritis/tenosynovitis or osteomyelitis that developed after fracture repair. Antibiotics were deemed highly effective, effective or ineffective if > or = 85%, 70-84.9% or < 70% of the isolates were susceptible respectively. In total, 424 bacterial types were isolated; 386 were aerobic or facultative and 38 were anaerobic. Enterobacteriaceae (28.8%) were the most common bacterial group isolated, followed by non-beta-haemolytic streptococci (13.0%), coagulase-positive staphylococci (11.8%), beta-haemolytic streptococci (9.4%), and coagulase-negative staphylococci (7.3%). The remainder of the organisms were other Gram-negative (15.8%), other Gram-positive (2.3%) and miscellaneous (2.6%) bacteria. Penicillin and ampicillin were highly effective against beta-haemolytic streptococci, but were ineffective against other bacteria. Ampicillin was no more effective than penicillin against most bacteria. Amikacin was the most effective antibiotic against the wide range of bacteria isolated in this study. Amikacin was highly effective against coagulase-positive staphylococci, Enterobacteriaceae and Pseudomonas and was effective against coagulase-negative staphylococci and Actinobacillus. Gentamycin was not highly effective against any bacterial group; but was effective against coagulase-positive and negative staphylococci, Pseudomonas, Salmonella and Actinobacillus. Kanamycin was ineffective against all bacteria with the exception of Actinobacillus. Cephalothin was highly effective against beta-haemolytic streptococci, coagulase-positive staphylococci and Actinobacillus and was effective against coagulase-negative staphylococci.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antimicrobial susceptibility of Mannheimia haemolytica isolates from cattle in Japan from 2001 to 2002

A total of 27 clinical isolates of Mannheimia haemolytica from cattle in Japan from 2001 to 2002 were examined for antimicrobial susceptibility to 25 antimicrobial agents. The minimum inhibitory concentrations of 25 different antimicrobials were determined by an agar dilution method according to the guidelines of the National Committee for Clinical Laboratory Standards. Of the 27 isolates, seven isolates (26.9%) were resistant to at least one of the 25 drugs and resistance rates ranged from 3.7 to 18.5%. Resistance rates to dihydrostreptomycin (18.5%), oxytetracycline (11.1%), and doxycycline (11.1%) were relatively high and those to the remaining drugs were less than 10%.     

Antimicrobial susceptibility and molecular characterization of avian pathogenic Escherichia coli isolates

Ninety-five avian pathogenic Escherichia coli (APEC) isolates recovered from diagnosed cases of avian colibacillosis from North Georgia between 1996 and 2000 were serotyped and examined for typical virulence-factors, susceptibility to antimicrobials of human and veterinary significance, and genetic relatedness. Twenty different serotypes were identified, with O78 being the most common (12%). The majority of the avian E. coli isolates (60%), however, were non-typeable with standard O antisera. Eighty-four percent of isolates were PCR positive for the temperature-sensitive hemagglutinin (tsh) gene and 86% positive for the increased serum survival (iss) gene. Multiple antimicrobial-resistant phenotypes (> or =3 antimicrobials) were observed in 92% of E. coli isolates, with the majority of isolates displaying resistance to sulfamethoxazole (93%), tetracycline (87%), streptomycin (86%), gentamicin (69%), and nalidixic acid (59%). Fifty-six E. coli isolates displaying resistance to nalidixic acid were co-resistant to difloxacin (57%), enrofloxacin (16%), gatifloxacin (2%), and levofloxacin (2%). DNA sequencing revealed point mutations in gyrA (Ser83-Leu, Asp87-Tyr, Asp87-Gly, Asp87-Ala), gyrB (Glu466-Asp, Asp426-Thr), and parC (Ser80-Ile, Ser80-Arg). No mutations were observed in parE. Twelve of the quinolone-resistant E. coli isolates were tolerant to cyclohexane, a marker for upregulation of the acrAB multi-drug resistance efflux pump. Quinolone-resistant isolates were further genetically characterized via ribotyping. Twenty-two distinct ribogroups were identified, with 61% of isolates clustering into four major ribogroups, indicating that quinolone resistance has emerged among multiple avian pathogenic E. coli serogroups and chromosomal backgrounds.     

副猪嗜血杆菌分离株耐药性、血清型及RAPD基因型分析

为弄清某规模化养猪场感染和流行的副猪嗜血杆菌(HPS)菌株的耐药性、血清型及基因型,本试验自该猪场发生浆膜炎和关节炎病猪的不同组织样品中分离到6株HPS菌株,通过细菌培养特性、生化试验和PCR扩增细菌16S rRNA基因片段并测序对分离株进行鉴定;进而鉴定分离株对不同类别抗生素的耐药性;最后对分离株进行血清分型和RAPD基因分型并分析两者的相关性。结果显示,自病猪不同组织脏器中分离鉴定了6株HPS菌株,体外培养具有典型卫星生长现象;生化试验结果符合HPS反应特性;PCR均可扩增出821 bp的HPS 16S rRNA基因片段,且序列与HPS一致。药敏试验结果显示分离株对头孢菌素类、青霉素类、氨基糖苷类、大环内酯类和四环素类抗生素敏感,而对喹诺酮类、磺胺类、林可霉素类和氯霉素类抗生素产生耐药性。琼脂扩散试验结果显示HPS分离株均为血清5型;RAPD分析显示HPS分离株与15个血清型参考菌株可分为4个基因型。本试验结果为HPS的流行病学调查及防控具有一定的借鉴价值。     

Aerobic and anaerobic bacterial isolates from horses with pneumonia or pleuropneumonia and antimicrobial susceptibility patterns of the aerobes

Frequency of aerobic and anaerobic isolates in 327 aspirates and in 123 pleural fluid samples from 327 horses with pneumonia or pleuropneumonia and antimicrobial susceptibility patterns of the aerobes were reported. Of the 327 horses, 75% survived, 20% were euthanatized, and 5% died. Tracheobronchial aspirates or pleural fluid specimens from 25 of the horses did not yield growth. Of the remaining 302 horses, 221 had only aerobic organisms isolated, whereas only anaerobes were isolated from 6 of the 302 horses. The remaining 75 horses had mixed aerobic and anaerobic bacterial infections. The survival rates for horses with aerobic only isolates was twice that of horses with anaerobic isolates. The aerobic bacteria most frequently isolated were beta-Streptococcus spp, Pasteurella spp, Escherichia coli, and Enterobacter spp. The anaerobic species most frequently isolated were Bacteroides spp and Clostridium spp.     

Antimicrobial resistance patterns and plasmid profiles of Streptococcus suis isolates.

Streptococcus suis isolates recovered from diseased animals in Quebec and western Canada and from human cases in Europe were tested for their susceptibility to different antimicrobial agents and screened for their plasmid content. Most isolates from Quebec were clindamycin, erythromycin, and tetracycline resistant; animal isolates from western Canada were notably less resistant to clindamycin and erythromycin, whereas human isolates were considerably more susceptible to most antimicrobials tested. More than 60% of isolates had plasmids that ranged from 1.5 to 35 kilobases (kb). Of the 7 plasmid profiles found, 2 were particularly frequent in isolates from Quebec and western Canada, suggesting the presence of epidemic strains in the swine population. A particular plasmid band of about 5 kb was present in most Canadian isolates. When this band was used as a probe in colony and Southern blot hybridization, most isolates harboring the 5-kb plasmid hybridized, even though their plasmid profiles were different. Human isolates from Europe differed in their plasmid content from Canadian isolates of animal origin. Although a high degree of antimicrobial resistance was associated with the presence of plasmids in most isolates, it was not possible to establish a causative relationship.     

猪源耐甲氧西林金黄色葡萄球菌的耐药性及其SCCmec基因分型研究

为了解陕西猪场耐甲氧西林金黄色葡萄球菌(MRSA)的耐药表型及其SCCmec基因型分布情况,我们于2009年1月～7月在陕西地区6个规模化猪场,采集鼻腔拭子共计173份,利用选择性培养基分离金黄色葡萄球菌(SA),采用多重PCR方法扩增其中是否含有nuc基因和mecA基因进行MRSA鉴定;以琼脂稀释法进行药敏试验;并通过多重PCR方法对SCCmec进行基因分型。结果显示,调查的6个猪场中有2个猪场分离到MRSA,共分离到83株SA,其中有14株(16.9%)为MRSA,均为SCCmec-IVb型;药敏结果显示MRSA除对CFP、CHL、AMK和VAN敏感外,对CIP、OXA耐药率分别为57.1%和92.6%,对FOX、TET、ERY、甲氧嘧啶和卡那霉素的耐药率均为100%。结果显示了猪源SCCmec-IVb型MRSA株具有多重耐药特点,与人源SCCmec-IV型MRSA株耐药谱存在较大差异,这一结果提示猪源MRSA容易通过猪及其产品感染人。