Antimicrobial Resistance Of Bacterial Isolates Research Articles

Technical specifications on harmonised monitoring of antimicrobial resistance in zoonotic and indicator bacteria from food-producing animals and food.

Proposals to update the harmonised monitoring and reporting of antimicrobial resistance (AMR) from a public health perspective in Salmonella, Campylobacter coli, Campylobacter jejuni, Escherichia coli, Enterococcus faecalis, Enterococcus faecium and methicillin‐resistant Staphylococcus aureus (MRSA) from food‐producing animals and derived meat in the EU are presented in this report, accounting for recent trends in AMR, data collection needs and new scientific developments. Phenotypic monitoring of AMR in bacterial isolates, using microdilution methods for testing susceptibility and interpreting resistance using epidemiological cut‐off values is reinforced, including further characterisation of those isolates of E. coli and Salmonella showing resistance to extended‐spectrum cephalosporins and carbapenems, as well as the specific monitoring of ESBL/AmpC/carbapenemase‐producing E. coli. Combinations of bacterial species, food‐producing animals and meat, as well as antimicrobial panels have been reviewed and adapted, where deemed necessary. Considering differing sample sizes, numerical simulations have been performed to evaluate the related statistical power available for assessing occurrence and temporal trends in resistance, with a predetermined accuracy, to support the choice of harmonised sample size. Randomised sampling procedures, based on a generic proportionate stratified sampling process, have been reviewed and reinforced. Proposals to improve the harmonisation of monitoring of prevalence, genetic diversity and AMR in MRSA are presented. It is suggested to complement routine monitoring with specific cross‐sectional surveys on MRSA in pigs and on AMR in bacteria from seafood and the environment. Whole genome sequencing (WGS) of isolates obtained from the specific monitoring of ESBL/AmpC/carbapenemase‐producing E. coli is strongly advocated to be implemented, on a voluntary basis, over the validity period of the next legislation, with possible mandatory implementation by the end of the period; the gene sequences encoding for ESBL/AmpC/carbapenemases being reported to EFSA. Harmonised protocols for WGS analysis/interpretation and external quality assurance programmes are planned to be provided by the EU‐Reference Laboratory on AMR.

A survey of antimicrobial resistance in Enterobacteriaceae isolated from the Chesapeake Bay and adjacent upper tributaries.

In recent years, the rise in antimicrobial resistance (AR) in the healthcare setting as well as the environment has been recognized as a growing public health problem. The Chesapeake Bay (CB) and its upper tributaries (UT) is a large and biologically diverse estuary. This pilot study evaluated the presence of AR of gram‐negative bacteria isolated from water samples collected at various sites of the Chesapeake Bay. Bacterial organisms were identified and antimicrobial susceptibility testing was performed by phenotypic and genotypic methods. Ninety‐two distinctly different gram‐negative bacteria were identified; Klebsiella pneumoniae, Enterobacter cloacae, Enterobacter aerogenes, Serratia marcescens, and Escherichia coli were most often isolated. Serratia marcescens was more frequently isolated in samples from the UT compared to the CB. Antimicrobial resistance was more frequently detected in organisms from the CB by phenotypic and genotypic methods. Antimicrobial resistance to ampicillin, imipenem, tetracycline, and chloramphenicol were the most frequently observed resistance patterns. ACT‐1, CMY, and SHV genes were the most frequently detected resistance genes, with predominance in organism isolated from the CB. The results from this study emphasize the importance for further developing comprehensive surveillance programs of AR in bacterial isolates in the various environments, such as recreational and other water systems.

Antimicrobial resistance of bacterial isolates from different dairy products and their emergence in the food chain

Abstract The antibiotic resistance of foodborne pathogens represents a healthcare concern globally. This phenomenon has an increasing impact on medicine and economy. A total of 26 spoilage and pathogenic bacterial isolates originating from different dairy products have been screened against eight different antibiotics. Based on the type of the selective agar medium used for their isolation, the isolates were: five staphylococci isolates, six Vibrio isolates, two Pseudomonas sp. isolates, three Salmonella isolates, five E. coli isolates, and five coliform isolates. The overall resistance to the tested antimicrobials of the bacterial isolates was 31.73%, the majority being susceptible. Based on the results, there are isolates with multiple antibiotic patterns that can be possible risk factors and may call for preventive measures.

Prevalence of antimicrobial resistance in fecal Escherichia coli and Salmonella enterica in Canadian commercial meat, companion, laboratory, and shelter rabbits (Oryctolagus cuniculus) and its association with routine antimicrobial use in commercial meat rabbits

Antimicrobial resistance (AMR) in zoonotic (e.g. Salmonella spp.), pathogenic, and opportunistic (e.g. E. coli) bacteria in animals represents a potential reservoir of antimicrobial resistant bacteria and resistance genes to bacteria infecting humans and other animals. This study evaluated the prevalence of E. coli and Salmonella enterica, and the presence of associated AMR in commercial meat, companion, research, and shelter rabbits in Canada. Associations between antimicrobial usage and prevalence of AMR in bacterial isolates were also examined in commercial meat rabbits. Culture and susceptibility testing was conducted on pooled fecal samples from weanling and adult commercial meat rabbits taken during both summer and winter months (n=100, 27 farms), and from pooled laboratory (n=14, 8 laboratory facilities), companion (n=53), and shelter (n=15, 4 shelters) rabbit fecal samples. At the facility level, E. coli was identified in samples from each commercial rabbit farm, laboratory facility, and 3 of 4 shelters, and in 6 of 53 companion rabbit fecal samples. Seventy-nine of 314 (25.2%; CI: 20.7-30.2%) E. coli isolates demonstrated resistance to >1 antimicrobial agent. At least one E. coli isolate resistant to at least one antimicrobial agent was present in samples from 55.6% of commercial farms, and from 25% of each laboratory and shelter facilities, with resistance to tetracycline being most common; no resistance was identified in companion animal samples. Salmonella enterica subsp. was identified exclusively in pooled fecal samples from commercial rabbit farms; Salmonella enterica serovar London from one farm and Salmonella enterica serovar Kentucky from another. The S. Kentucky isolate was resistant to amoxicillin/clavulanic acid, ampicillin, cefoxitin, ceftiofur, ceftriaxone, streptomycin, and tetracycline, whereas the S. London isolate was pansusceptible. Routine use of antimicrobials on commercial meat rabbit farms was not significantly associated with the presence of antimicrobial resistant E. coli or S. enterica on farms; trends towards resistance were present when resistance to specific antimicrobial classes was examined. E. coli was widely prevalent in many Canadian domestic rabbit populations, while S. enterica was rare. The prevalence of AMR in isolated bacteria was variable and most common in isolates from commercial meat rabbits (96% of the AMR isolates were from commercial meat rabbit fecal samples). Our results highlight that domestic rabbits, and particularly meat rabbits, may be carriers of phenotypically antimicrobial-resistant bacteria and AMR genes, possibly contributing to transmission of these bacteria and their genes to bacteria in humans through food or direct contact, as well as to other co-housed animal species.

High burden of antimicrobial resistance among gram negative bacteria causing healthcare associated infections in a critical care unit of Nepal

BackgroundHealthcare associated infections (HCAI) and antimicrobial resistance are principal threats to the patients of intensive care units and are the major determining factors for patient outcome. They are associated with increased morbidity, mortality, excess hospitalization and financial costs. The present study is an attempt to investigate the spectrum and antimicrobial resistance of bacterial isolates involved in healthcare associated infections (HCAI) in the patients of a critical care unit at a tertiary care university hospital in Kathmandu, Nepal.MethodsA laboratory based study was conducted over the period of 15 months (January 2014 to March 2015) among the patients of intensive care unit of Tribhuvan University Teaching Hospital, Kathmandu, Nepal. Clinical specimens from patients with suspected healthcare-associated infection were processed and bacterial isolates were identified with standard microbiological methods. Antimicrobial susceptibilities of the isolated strains were determined according to the CLSI guidelines and β-lactamases (ESBL, AmpC, MBL and KPC) were detected by various phenotypic tests.ResultsOne hundred and forty nine clinical specimens received from 135 patients suspected of HCAI (out of 491 patients) were found with significant bacterial growth. Specimens were from patients suspected of hospital-acquired pneumonia (16%, 79/491), bloodstream infections (5.7%, 28/491), surgical site infections (4.7%, 23/491), and urinary tract infections (3.9%, 19/491). Acinetobacter spp., Klebsiella spp., Escherichia coli and Burkholderia cepacia were the leading bacterial pathogens. Extremely high level of drug resistance (95.8%) along with the production of β-lactamases (ESBL; 43.7%, AmpC; 27.5%), MBL; 50.2% and KPC; 4.2%) was observed among Gram negative bacterial isolates.ConclusionHealthcare associated infections are very common in our ICU. Gram negative bacterial pathogens are major culprits associated with these infections and there is alarming state of drug resistance among these isolates. Continuous surveillance and establishment of preventive and control measures of healthcare associated infections are urgently needed in our setting.

Prevalence of Antibiotic-resistance Enterobacteriaceae strains Isolated from Chicken Meat at Traditional Markets in Surabaya, Indonesia

Antibiotic resistance in bacteria from the family Enterobacteriaceae is an important indicator of the emergence of resistant bacterial strains in the community. This study investigated the prevalence of antibiotic-resistant Enterobacteriaceae isolated from chicken meat sold at traditional markets in Surabaya Indonesia. In all, 203 isolates (43 Salmonella spp., 53 Escherichia coli, 16 Shigella spp., 22 Citrobacter spp., 13 Klebsiella spp, 24 Proteus spp., 15 Yersinia spp., 7 Enterobacter spp., 6 Serratia spp., 3 Edwardsiella spp. were resistant to tetracycline (69.95 %), nalidixid acid (54.19 %), sulfamethoxazole/sulfamethizole (42.36 %), chloramphenicol (12.81%), cefoxitin (6.40 %), gentamicin (5.91 %). Tetracycline was the antimicrobial that showed the highest frequency of resistance among Salmonella, E. coli, Citrobacter, Proteus and Erdwardsiella isolates, and nalidixid acid was second frequency of resistance. Overall, 124 (61.08 %) out of 203 isolates demonstrated multidrug resistance to at least two unrelated antimicrobial agents. The high rate of antimicrobial resistance in bacterial isolates from chicken meat may have major implications for human and animal health with adverse economic implications.

Patterns of infections, aetiological agents and antimicrobial resistance at a tertiary care hospital in northern Tanzania.

To determine the causative agents of infections and their antimicrobial susceptibility at a tertiary care hospital in Moshi, Tanzania, to guide optimal treatment. A total of 590 specimens (stool (56), sputum (122), blood (126) and wound swabs (286)) were collected from 575 patients admitted in the medical and surgical departments. The bacterial species were determined by conventional methods, and disc diffusion was used to determine the antimicrobial susceptibility pattern of the bacterial isolates. A total of 249 (42.2%) specimens were culture-positive yielding a total of 377 isolates. A wide range of bacteria was isolated, the most predominant being Gram-negative bacteria: Proteus spp. (n = 48, 12.7%), Escherichia coli (n = 44, 11.7%), Pseudomonas spp. (n = 40, 10.6%) and Klebsiella spp (n = 38, 10.1%). Wound infections were characterised by multiple isolates (n = 293, 77.7%), with the most frequent being Proteus spp. (n = 44, 15%), Pseudomonas (n = 37, 12.6%), Staphylococcus (n = 29, 9.9%) and Klebsiella spp. (n = 28, 9.6%). All Staphylococcus aureus tested were resistant to penicillin (n = 22, 100%) and susceptible to vancomycin. Significant resistance to cephalosporins such as cefazolin (n = 62, 72.9%), ceftriaxone (n = 44, 51.8%) and ceftazidime (n = 40, 37.4%) was observed in Gram-negative bacteria, as well as resistance to cefoxitin (n = 6, 27.3%) in S. aureus. The study has revealed a wide range of causative agents, with an alarming rate of resistance to the commonly used antimicrobial agents. Furthermore, the bacterial spectrum differs from those often observed in high-income countries. This highlights the imperative of regular generation of data on aetiological agents and their antimicrobial susceptibility patterns especially in infectious disease endemic settings. The key steps would be to ensure the diagnostic capacity at a sufficient number of sites and implement structures to routinely exchange, compare, analyse and report data. Sentinel sites (hospitals) across the country (and region) should report on a representative subset of bacterial species and their susceptibility to drugs at least annually. A central organising body should collate the data and report to relevant national and international stakeholders.

Antimicrobial resistance of bacterial isolates from respiratory secretions of ventilated patients in a multi-specialty hospital.

Context:Ventilator-associated pneumonia (VAP) is a common nosocomial infection occurring in intensive care unit (ICU) settings. VAP occurs due to interplay of three factors - impaired host defense, access of large numbers of pathogenic bacteria to the lower respiratory tract and the virulence of the organism. Knowledge of colonizing microbial flora and their antibiogram in ventilated patients is of great importance in timely institution of empirical therapy, so that mortality and morbidity due to VAP can be reduced.Subjects and Methods:A prospective study was performed over a period of 6 months in a multi-specialty hospital to determine the various pathogens in respiratory secretions and to determine the prevalence of multidrug resistance (MDR).Results:Pseudomonas aeruginosa (26%), Acinetobacter (26%), Klebsiella pneumoniae (26%), followed by Escherichia coli (15%), Staphylococcus aureus (6%) and Citrobacter spp. (1.5%) were the common pathogens isolated in our study. In all, 72.73% (48/66) bacterial isolates were isolated from medical ICU, while 25.76% (17/66) were isolated from surgical ICU. Only one strain (Acinetobacter) was isolated from pediatric ICU. Fifty-seven (86.36%) of the 66 pathogens in our study were MDR.Conclusion:There is increasing colonization of pathogenic bacteria in ventilated patients admitted in ICUs, which are predominantly MDR. These colonizers may cause infection resulting in VAP. Judicious use of antibiotics, guided by local antibiotic resistance profile coupled with strict infection control practices alongside application of VAP bundle are important measures to prevent these pathogens from causing VAP in ICU patients.

PREVALENCE AND ANTIMICROBIAL RESISTANCE ASSESSMENT OF SUBCLINICAL MASTITIS IN MILK SAMPLES FROM SELECTED DAIRY FARMS

This study was conducted in order to determine the prevalence and bacteriological assessment of subclinical mastitis and antimicrobial resistance of bacterial isolates from dairy cows in different farms around Selangor, Malaysia. A total of 120 milk samples from 3 different farms were randomly collected and tested for subclinical mastitis using California Mastitis Test (CMT), as well as for bacterial culture for isolation, identification and antimicrobial resistance. The most prevalent bacteria was Staphylococcus sp. (55%), followed by Bacillus sp., (21%) and Corynebacterium sp., (7%), Yersinia sp. and Neisseria sp. both showed 5% prevalence, other species with prevalence below 5% are Acinetobacter sp., Actinobacillus sp., Vibrio sp., Pseudomonas sp., E.coli, Klebsiella sp. and Chromobacter sp. Selected Staphylococcus sp. showed a mean antimicrobial resistance of 73.3% to Ampicillin, 26.7% to Penicillin, Methicillin and Compound Sulphonamide each, 20% to Oxacillin, Amoxycillin and Cefuroxime, 13.3% to Polymyxin B, Erythromycin, Ceftriaxone and Azithromycin and 6.7% to Streptomycin, Clindamycin, Lincomycin and Tetracycline each. This study indicates the need for urgent and effective control measures to tackle the increase in prevalence of subclinical mastitis and their antimicrobial resistance in the study area.

Carbapenem resistance in Acinetobacter baumannii: laboratory challenges, mechanistic insights and therapeutic strategies

Unprecedented levels of antimicrobial resistance in bacterial isolates have prompted great concerns globally. In 2012 the WHO released a publication outlining the evolving threat of antimicrobial resistance in order to raise awareness and to stimulate coordinated international efforts. The carbapenem class of antibiotics is largely considered as an antibiotic of last-resort when treating infections. Now carbapenem resistance further limits treatment options. In this article the authors discuss carbapenem resistance in Acinetobacter baumannii, a bacterial isolate often implicated in nosocomial infections. Virulence factors, intrinsic and acquired resistance mechanisms, together with laboratory challenges in the detection and antibiotic susceptibility testing of A. baumannii make this a truly problematic isolate. Therapeutic options are exceedingly limited, relying on polymyxins in combinations with other antibiotics, with few, if any, new active agents in the pipeline.

Technical specifications on the harmonised monitoring and reporting of antimicrobial resistance in Salmonella, Campylobacter and indicator Escherichia coli and Enterococcus spp. bacteria transmitted through food

Proposals to improve the harmonisation of monitoring and reporting of antimicrobial resistance in Salmonella, Campylobacter coli and jejuni, indicator Escherichia coli and Enterococcus from food producing animals and derived meat by the European Union Member States are presented. In establishing a list of combinations of bacterial species, food-producing animal populations and food products and in setting up priorities for the monitoring of antimicrobial resistance from a public health perspective, the potential exposure of the consumers has been considered as the first variable to be taken into account. As the prevalence of Salmonella is decreasing, monitoring of antimicrobial resistance should be enforced in indicator bacteria. The concept of a threshold is introduced for some animal populations and their derived meat (whose consumption is limited to certain Member States) to determine whether monitoring of antimicrobial resistance should be mandatory. Currently used phenotypic monitoring of antimicrobial resistance in bacterial isolates is to be retained but recommendations are given for broadening the harmonised panel of antimicrobials used for Salmonella, E. coli and Enterococcus spp. with the inclusion of substances that are either important for human health or that can provide clearer insight into the resistance mechanisms involved. The use of microdilution methods for testing is confirmed as the preferred option and this should be accompanied by the application of epidemiological cut off values for the interpretation of microbiological resistance. A two-step testing strategy has been devised to further characterise those isolates of E.coli and Salmonella spp. showing resistance to extended spectrum cephalosporins and carbapenems. Several analytical methods are suggested for monitoring of ESBL/AmpC-producing E.coli. Finally, full support is given to the collection and reporting of data at isolate level, in order to enable more in-depth analyses to be conducted, in particular on the occurrence of multi-resistance.

Development of statistical methods for the evaluation of data on antimicrobial resistance in bacterial isolates from animals and food

Development of statistical methods for the evaluation of data on antimicrobial resistance in bacterial isolates from animals and food

Antimicrobial resistance of bacterial isolates from respiratory care wards in Taiwan: a horizontal surveillance study comparison of the characteristics of nosocomial infection and antimicrobial-resistant bacteria in adult Intensive Care Units and two respiratory care facilities for mechanically ventilated patients at a tertiary care centre in Taiwan

The objectives of this study were to compare the incidence of nosocomial infections (NIs) and the distribution of resistant nosocomial pathogens in adult Intensive Care Units (ICUs) and two respiratory care facilities for prolonged mechanically ventilated patients [i.e. the respiratory care centre (RCC) and the respiratory care ward (RCW)] in a 1100-bed tertiary care hospital in Taiwan from 2003 to 2006. The overall incidences of NI for adult ICUs, the RCC and the RCW were 14.0, 10.3 and 5.0 per 1000 patient-days, respectively. Urinary tract infections, bloodstream infections and pneumonias occurred most frequently. The most common reported microorganisms in adult ICUs were non-fermentative Gram-negative bacilli (NFGNB) (33.0%), Enterobacteriaceae (26.5%), Candida spp. (18.2%), Staphylococcus aureus (8.9%), coagulase-negative staphylococci (CoNS) (4.9%) and enterococci (4.5%). In comparison, RCW patients had a higher proportion of NIs caused by S. aureus [odds ratio (OR) = 1.9], enterococci (OR = 2.2) and Enterobacteriaceae (OR = 2.2), but a lower proportion of CoNS (OR = 0.3), NFGNB (OR = 0.5) and Candida spp. (OR = 0.2). RCW patients had higher incidence rates of meticillin-resistant S. aureus (OR = 4.91) and extended-spectrum β-lactamase-producing Enterobacteriaceae (OR = 4.06) than ICU patients. Further study is needed to delineate the mechanisms responsible for the differences in resistance profile amongst pathogens associated with nosocomial infection in ICUs, RCCs and RCWs.

Antimicrobial resistance in Escherichia coli isolates from food animals, animal food products and companion animals in China

One thousand and thirty Escherichia coli isolates from food animals, animals-derived foods, and companion animals between 2007 and 2008 in Southern China were used to investigate their antimicrobial susceptibility to 14 different antimicrobials by the standard agar dilution method. More than 70% of isolates showed resistance to tetracycline, trimethoprim–sulphamethoxazole, nalidixic acid, and ampicillin. In general, resistance was less frequent in companion animal isolates vs food animals isolates, but cephalosporin and amikacin resistance was more frequent in companion animal isolates, 42.6% to 56.2% vs 14.1% to 24.3%, and 28.5% vs 18.8%, respectively, which was most likely due to the common use of these antimicrobials as treatment in pet animals. Fluroquinolones resistance was high in all animal isolates (>50%). Food products showed lowest resistance among isolates from these three resources. PFGE analysis indicated that a majority of multidrug-resistant E. coli isolates showed unique, unrelated PFGE profiles and were unlikely to be the spread of a specific clone. This study provides useful information about the prevalence of antimicrobial resistance in E. coli isolated from animals and food products in China and provided evidence of the linkage of the use of antimicrobials in animals and its selection of antimicrobial resistance in bacterial isolates. The data from this study further warns the prudent use of antimicrobials in food and pet animals to reduce the risks of transmission of antimicrobial resistance zoonotic pathogen to humans.

Antimicrobial resistance of bacterial isolates from urinary tract infections at Felge Hiwot Referral Hospital, Ethiopia

Abstract Urinary tract infections are common health problems and vary according to geography and regions. A retrospective analysis was conducted to determine the antimicrobial resistance of bacterial isolates from urine at Felege Hiwot Referral Hospital from September 2003 to June 2008. From 529 urine specimens, bacterial isolates were found in 160 [(30.2%) (95% CI: 26.3-34.1%)]. Of these, 116 (72.5%) of the isolates were gram negatives. Single and multiple drug resistance to the commonly used antibiotics were high among bacterial isolates in the area. Thus, rational use of drugs should be practiced. [Ethiop. J. Health Dev. 2009;23(3):236-238]

Antimicrobial resistance of bacterial isolates from respiratory care wards in Taiwan: a horizontal surveillance study

A horizontal surveillance study was conducted to identify common bacteria and mycobacteria from 611 respiratory aspirates and 165 urinary samples from 611 patients hospitalised at 17 respiratory care wards (RCWs) in Taiwan. Some major resistance phenotypes, including meticillin-resistant Staphylococcus aureus (MRSA), extended-spectrum β-lactamase (ESBL)-producing Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis, and multidrug-resistant Pseudomonas aeruginosa (MDR-PA) and Acinetobacter baumannii (MDR-AB), were identified. Pulsotypes of ESBL-producing P. mirabilis isolates were determined by pulsed-field gel electrophoresis. The prevalences of MRSA, ESBL-producing E. coli ( K. pneumoniae and P. mirabilis), carbapenem-resistant (resistant to imipenem and meropenem) P. aeruginosa, MDR-PA, carbapenem-resistant A. baumannii and MDR-AB were, respectively, 86.7%, 20.0% (50.7% and 24.1%), 18.4%, 1.2%, 32.1% and 8.9% for respiratory aspirates and 100%, 25.4% (27.3% and 25.0%), 48.3%, 10.3%, 50.0% and 21.4% for catheterised urinary samples. Among the 44 respiratory isolates of P. mirabilis with an ESBL phenotype, 22 different pulsotypes (>80% identity) were identified. Among 103 isolates of mycobacteria, 90 (87.4%) belonged to rapidly growing mycobacteria and 4 (4%) were Mycobacterium tuberculosis. Among the 404 patients with available clinical information, true infections were found in 28.0%, the most prevalent of which were urinary tract infection (20.5%) and ventilator-associated pneumonia (10.9%). High prevalences of various multidrug-resistant bacteria among the respiratory and urinary tracts of patients present a clinical difficulty in choosing empirical antibiotic treatment in RCWs.

P1545 Prevalence and antimicrobial resistance of bacterial isolates in neonatal blood-stream infections

P1545 Prevalence and antimicrobial resistance of bacterial isolates in neonatal blood-stream infections

Antibiotic susceptibility patterns from Irish equines

A longitudinal, retrospective investigation was carried out of antimicrobial resistance in bacterial isolates (n = 1060) from horses in Ireland over the period 1990 through 2000. Bacterial isolates that were collected from clinical cases of equine infection from throughout Ireland in 1990 (n = 394), 1996 (n = 323), and 2000 (n = 343), were recultured from archived isolates. Standard antibiotic disk susceptibility tests were performed against the following antibiotics (disk concentration): penicillin, ampicillin, amoxicillin, amoxicillin/clavulanic acid, gentamicin, sulfamethoxazole/trimethoprim, erythromycin, and ceftiofur. In all cases, plates were incubated at 35°C for 18 hours before results were read. Antibiotic resistance rates are shown in the Table (opposite page). Using 2 test for trend, statistically significant rising trends (P < .05) were identified in the resistance of (1) Escherichia coli and gentamicin, (2) hemolytic streptococci and penicillin, (3) hemolytic streptococci and penicillin, (4) hemolytic streptococci, (5) hemolytic streptococci and ampicillin, and (6) hemolytic streptococci and erythromycin. No significant trends were apparent for any of the other organism/drug interactions examined. To date, there has been relatively limited data in the literature regarding antibiotic resistance patterns in horses, and the current study is the first formal report of resistance patterns in horses from Ireland. Ensink et al1 suggested that quantitative antibiotic susceptibility testing of bacterial pathogens in equine infection may serve as a useful means to optimize antibiotic management in the patient. National monitoring of antibiotic resistance patterns in horses is important for several reasons, including (1) optimum employment of licensed anti-infectives for therapeutic purposes, (2) development of a longterm anti-infective strategy between equine veterinarians and the pharmaceutical industry, and (3) examining the potential interaction with human clinical medicine. Currently there has been growing concern over antimicrobial resistance in pathogenic bacterial populations in both human and clinical medicine and a recent report has demonstrated the nosocomial transmission of methicillin-resistant Staphylococcus aureus from humans to horses in a surgical unit in a veterinary teaching hospital.2 The emphasis of antimicrobial resistance in equines differs from other large animals, in that antimicrobials are not used as growth promoters nor is the zoonotic link with humans as strong, given that consumption of horse meat in the British Isles is not common. In conclusion, the main findings of this study were rising trends in resistance by the majority of the isolates tested. Significant differences in resistance levels were found in at least one antimicrobial in each organism isolated. Prospective investigations are needed to identify selection pressures on the development of antimicrobial resistance in bacterial isolates from horses, so that control measures can be put in place to minimize future increases in resistance. Regular surveillance should therefore be encouraged to monitor resistance patterns in healthy, as well as sick, equines.

Survey of antimicrobial susceptibility testing practices of veterinary diagnostic laboratories in the United States

To describe antimicrobial susceptibility testing practices of veterinary diagnostic laboratories in the United States and evaluate the feasibility of collating this information for the purpose of monitoring antimicrobial resistance in bacterial isolates from animals. Cross-sectional study. A questionnaire was mailed to veterinary diagnostic laboratories throughout the United States to identify those laboratories that conduct susceptibility testing. Nonrespondent laboratories were followed up through telephone contact and additional mailings. Data were gathered regarding methods of susceptibility testing, standardization of methods, data management, and types of isolates tested. Eighty-six of 113 (76%) laboratories responded to the survey, and 64 of the 86 (74%) routinely performed susceptibility testing on bacterial isolates from animals. Thirty-four of the 36 (94%) laboratories accredited by the American Association of Veterinary Laboratory Diagnosticians responded to the survey. Laboratories reported testing > 160,000 bacterial isolates/y. Fifty-one (88%) laboratories reported using the Kirby-Bauer disk diffusion test to evaluate antimicrobial susceptibility; this accounted for 65% of the isolates tested. Most (87%) laboratories used the NCCLS (National Committee for Clinical Laboratory Standards) documents for test interpretation. Seventy-five percent of the laboratories performed susceptibility testing on bacterial isolates only when they were potential pathogens. The veterinary diagnostic laboratories represent a comprehensive source of data that is not easily accessible in the United States. Variability in testing methods and data storage would present challenges for data aggregation, summary, and interpretation.

Multiple antimicrobial resistance in bacterial isolates from clinical and environmental sources of Jimma Hospital, Southwest Ethiopia

A total of 545 clinical specimens (pus, blood, urine, and stool) and environmental specimens (air sample, saline solution, nasal swabs etc) were cultured for isolation and identification of aerobic bacteria and antimicrobial susceptibility testing. Out of these, 356(65%) specimens yielded one or more bacterial strains. Frequent bacterial isolates were S. aureus (17%), coagulase-negative staphylococci (25%), Proteus species (10.%), Klebsiella species (8%), E. coli and Enterobacter species (14%). The antimicrobial susceptibility test result shows that all E. coli, Klebsiella, and Enterobacter species were resistant to ampicillin. Similarly 93% S. aureus, 88% coagulase-negative staphylococci were resistant to the same antimicrobial agent. Eighty five percent of Klebisiella, and 79% of E. coli were resistant to tetracycline. Almost all the isolates were found to be multiply resistant to the commonly used antimicrobials, ampicillin, tetracycline, chloramphenicol, and trimethoprim-sulphamethoxazole. Antimicrobial resistant strains of bacteria are increasing and may contribute to spread of serious infectious diseases. Therefore, to prevent and control infections by emerging antimicrobial resistant bacterial strains, measures such as strengthening clinical microbiology laboratory, emphasis on hygienic practices in hospital, and prudent use of existing antimicrobial agents are recommended. Key words/phrases: Antimicrobial resistance, antimicrobial susceptibility, bacterial isolates, microorganisms SINET: Ethiopian Journal of Science Vol.25(2) 2002: 295-302