Epidemiological and molecular characterization of Staphylococcus haemolyticus strains, from a hematology ward, with decreased susceptibility to glycopeptides

In the present study, we report on the reduced susceptibility to teicoplanin among clinical isolates of Staphylococcus haemolyticus in a hematology ward of a teaching hospital. The molecular characterization of 17 S. haemolyticus strains was performed using mec gene complex classification, pulsed-field gel electrophoresis analysis, and minimum inhibitory concentration examination. Pulsotype A strains carrying a class C2 mec gene complex were the most prevalent strains, at 64.7%. In vivo selection of stepwise increase in resistance to vancomycin and teicoplanin was observed in three S. haemolyticus strains serially isolated from a case patient. The results of the present study suggest the regional spread of certain S. haemolyticus clones with diminished susceptibility to glycopeptides, emphasizing the need for continuous monitoring of minimum inhibitory concentration levels of vancomycin and teicoplanin in S. haemolyticus strains, and the importance of infection control practices to prevent its transmission.     

武汉地区医院感染葡萄球菌的耐药性监测

目的了解武汉地区医院感染葡萄球菌的耐药现状。方法采用回顾性分析方法,对2003年1月到2007年12月我院分离的1373株金黄色葡萄球菌和259株表皮葡萄球菌的耐药性进行分析。药敏试验采用K—B纸片法,判断标准根据美国临床实验室标准化委员会（NCCLS）的标准。结果2003年1月到2007年12月我院分离到金黄色葡萄球菌1373株,其中耐甲氧西林的金黄色葡萄球菌（MRSA）有697株,对甲氧西林敏感株（MSSA）有587株,表皮葡萄球菌有259株,其中耐甲氧西林的表皮葡萄球菌（MRSE）有92株,对甲氧西林敏感株（MSSE）有142株。MRSA、MRSE对临床常用的抗生素几乎均耐药,只有对万古霉素和替考拉宁100％敏感;MSSA、MSSE对临床常用抗生素较敏感,但是对青霉素和红霉素耐药率均大于70％。结论武汉地区医院感染MRSA和MRSE对大部分临床常用抗生素均已高度耐药,对万古霉素和替考拉宁依然高度敏感。了解医院感染葡萄球菌的耐药状况,对临床合理选用抗生素十分重要。     

Susceptibility to selected chemotherapeutics of Staphylococcus aureus strains resistant to methycyline isolated from clinical materials in the years 1991-1992 and 1997

The susceptibility to selected chemotherapeutic agents was determined in 100 strains of Staphylococcus aureus methicillin-resistant (MRSA) isolated from clinical materials in 1991-1992 (50 strains) and in 1997 (50 strains). Two methods were used for the determination: disc method and antibiotic dilution in agar. The minimal inhibitory concentration (MIC) was determined for vancomycin, teicoplanin, furazolidone, nitrofurantoin, ofloxacin, gentamicin, netilmicin and trimethoprim. The concentrations of the chemotherapeutics in the substrate ranged from 0.125 to 512 mg/l. The obtained results served for drawing of the following conclusions: all studied MRSA strains isolated in 1991-1992 and in 1997 were sensitive to glycopeptide antibiotics: vancomycin and teicoplanin, to nitrofurans: nitrofurantoin and furazolidone, and to fusidic acid. MRSA strains isolated in 1991-1992 were sensitive to ofloxacin, but in 1997 about 80% of the strains were resistant to that antibiotic, and this resistance was noted in S. aureus strains with homogeneous resistance to methicillin. Increasing frequency of resistance to mupirocin was found, in 1991-1992 4% of the strains were resistant, and in 1997 the resistance of MRSA to that antibiotic was found in 12%. No changes occurred in the sensitivity of staphylococci to trimethoprim/sulfamethoxazole (cotrimoxazole). About 94% of strains in 1991-1992 and 1997 were sensitive to that drug. The sensitivity to cotrimoxazole is connected with one of its components (trimethoprim), with 94% of MRSA strains sensitive to it.     

Drug resistance of 100 clinical strains of Enterococcus spp

The aim of this study was to evaluate the drug susceptibility of 100 Enterococcus spp. strains isolated from patients hospitalized in State Clinical Hospital No 1 in Warsaw. All strains were identified (API 20 STREP) and their susceptibility to antibiotics was tested (ATB STREP) in automatic ATB system. Additionally, PYRase activity, beta-lactamase production (in nitrocefin test), MICs for vancomycin and teicoplanin (E test), HLAR--high level aminoglycoside resistance and susceptibility to vancomycin, teicoplanin, piperacillin and piperacillin/tazobactam (disc diffusion method) were determined. E. faecalis ATCC 29212 was used as the control strain. Fifty E. faecalis, 45 E. faecium, 2 E. casseliflavus, 2 E. durans and 1 E. avium strain were cultured. All strains were PYRase-positive and beta-lactamase-negative. Ten isolates demonstrated intermediate susceptibility to vancomycin (6--E. faecalis and 4--E. faecium). One E. faecalis strain was intermediately susceptible to both glycopeptides. One E. casseliflavus strain showed low-level resistance to vancomycin, but this strain was susceptible to teicoplanin--phenotype Van C. HLAR strains were found among 31 E. faecalis and 40 E. faecium strains. 48 E. faecalis strains were susceptible to piperacillin and 49 to piperacillin/tazobactam. Whereas, 41 E. faecium were resistant to both these drugs. Thirty six per cent of isolates were resistant to penicillin and ampicillin, 73% to erythromycin, 87% to tetracycline, 89% to lincomycin and 56% to nitrofurantoin. Some discrepancies were noticed between the results of different methods applied for susceptibility testing--ATB system, E test and disc diffusion. These discrepancies concerned HLAR detection and susceptibility to glycopeptides determination. The best methods were: disc-diffusion for HLAR detection and E test for determination of resistance to vancomycin and teicoplanin. Increasing resistance to antimicrobial agents is observed in clinical Enterococcus spp. isolates cultured in our laboratory, especially in E. faecium strains. It is necessary to control the dissemination of multiresistant Enterococcus spp. strains in hospital wards.     

Antimicrobial sensivity and ability to slime production of koagulaze-negative staphylococci

The aim of this study was to assess the ability of slime production ofcoagulase-negative staphylococci (CONS) and evaluate the susceptibility of bacteria to antibiotics. Strains were isolated from clinical specimens obtained from hospitalized patients. The most frequently isolated species were S. epidermidis (51%), S. hominis (18%), S. haemolyticus (13%). The result of this study shows that 61% of S.epidermidis produce slime on CRA (Congo red agar), whereas none of the tested S. haemolyticus strains has this ability. All examined strains were susceptible to vancomycin, linezolid and quinupristin/ dalfopristin. The majority of strains were susceptible to minocycline, fusid acid, nitrofurantoin and rifampicin. Sixty six percent of isolates were determined as methicillin-resistant coagulase-negative staphylococci.     

医院感染葡萄球菌菌种变迁与耐药性近况

目的：了解近9年来医院感染葡萄球菌菌种的变迁与近3年来葡萄球菌药状况。方法：1993年1月至2001年12月我院传染病科等13科室住院病人的各种标本采用血琼脂培养,所分离的葡萄球菌采用美国DADE公司生产的MICROSCAN WALKAY-40全自动微生物分析仪鉴定到种及其亚种。药敏试验药物有青霉素、苯唑西林、氨苄西林、哌拉西林、阿莫西林／克拉维酸（阿莫仙）、头孢唑啉、头孢噻肟、头孢哌酮／舒巴坦（舒普深）、庆大霉素、复方新诺明、环丙沙星、氧氟沙星、利福平、万古霉素、红霉素、林可霉素、四环素、伊米配能／西司他丁（泰能）共18种。采用液体稀释法测定每株葡萄球菌对受试药物的最小抑菌浓度（MIC）,操作按说明书进行。质控菌ATCC25923。依据新近NCCLS标准判读结果。结果：1993年至1998年分离的葡萄球菌中,金黄色葡萄球菌（金葡萄）占71.43%,凝固酶阴性葡萄球菌（CNS）占28.57%,包括表皮葡萄球菌（表葡菌）、腐生葡萄球菌、里昂葡萄球菌和头状葡萄球菌4种。1999年至2001年分离的424株葡萄球菌中,金葡菌仅占29.01%,CNS增至13种,占70.995,以表葡菌、溶血葡萄球菌、松鼠葡萄球菌为主。近3年来分离的各种葡萄球菌甲氧西林耐药率在73.03%-100%之间,除对舒普深、复方新诺明、利福平和万古霉素较敏感外,对其余抗菌药物的耐药率均超过60％,以金葡菌、溶血葡萄球菌、松鼠葡萄球菌的耐药率为最高。MRS耐药率普遍高于MSS,且均呈多重耐药。5.42%(23/424)菌株万古霉素MIC＞16mg/L,除1株为MSCNS外,其余22株均为MRS。结论：3年来医院感染葡萄球菌菌种构成比发生了显著变化,以CNS为主。对抗菌药物呈多重耐药,部分菌株对万古霉素敏感性降低,应予警惕。     

Evaluation of susceptibility to antibiotics of Staphylococcus aureus strains resistant to methicillin]

Methicillin-resistant strains of Staphylococcus aureus (MRSA) constitute a serious diagnostic and therapeutic problem. Over 500 strains of Staphylococcus aureus were tested for susceptibility to methicillin. By application of a screening method, 13.7% of these strains were classified as methicillin-resistant. Over 95% of these strains were isolated from hospital infections. Applying criteria of belonging of these strains to methicillin-resistance classes it was found that 49.3% belonged to class II, 31.2% to class III and 19.5% to class IV. Analysis of susceptibility to antibiotics of MRSA strains demonstrated significant differences between class II and between class III and IV in resistance to imipenem, gentamycin, erythromycin and tetracycline. All tested strains were susceptible to ciprofloxacin, ofloxacin, vancomycin and teicoplanin. The screening method (25 mg methicillin/l of TSA medium) results in obtaining of univocal results of determination of methicillin-resistance in S. aureus.     

ICU病房G^＋菌谱及其耐药性连续9年监测

目的了解我院ICU病房分离菌中G^＋菌谱及其耐药情况,为临床防治G^＋菌感染提供依据。方法对ICU病房自1998年1月至2006年12月9年间所分离到的G^＋菌及其耐药性进行回顾性调查。结果9年间共分离获得G^＋菌408株,占总的23.2%（408/1755）。由1998年至2004年,G^＋菌分离率逐年增多,2004年后又有所下降。G^＋菌以金黄色葡萄球菌（SA）为主,占65.7%,其次为溶血葡萄球菌（SH,10.8%）、表皮葡萄球菌（SE,9.5%）。MRSA占SA的89.9%,MRSE占SE的92.3%。体外药敏试验结果显示主要G^＋菌均呈多重耐药特性,只有万古霉素对G^＋具有很强抗菌活性,敏感率达100%。结论ICU病房在所分离的G^＋菌中,耐甲氧西林葡萄球菌（MRS）所占比例很高,细菌呈多重耐药特性。我们应高度重视这一严重问题并尽一切可能预防院内感染和减少多重耐药菌的产生。     

Phage pattern and antibiotic resistance pattern of coagulase-negative staphylococci obtained from immunocompromised patients.

A total of 152 coagulase-negative staphylococcal strains were isolated from clinical samples of 14 patients hospitalized after bone-marrow transplantation in a specialized hospital ward in Hungary, during an 18-month period between 1987 and 1989. Two species, Staphylococcus epidermidis and Staphylococcus haemolyticus, predominated (each, 45%). Using Pulverer and co-workers' phage set for typing, 68% of the isolates were typable; 16 phage patterns were observed. A characteristic long pattern with phages Ph10/Ph13/Ph15/U4/U15/U16/U20/U33 /U46 appeared only in S. epidermidis, among 5 of 11 colonized patients (8.5% of all strains). Single lysis with phage Ph13 was observed in 7 of the 14 patients (49% of all strains), in species S. capitis, S. epidermidis, S. haemolyticus, S. hominis, and S. warneri. In S. haemolyticus, non-typable strains predominated (66%); this character occurred only in 2% among other species. The strains colonizing the immunocompromised patients differed from each other in phage pattern, antibiotic resistance pattern, and/or slime production. No hospital infection was suggested. On the other hand, high incidence of two well-definable phage patterns raises some relationship between phage receptors or some regulatory systems in phage multiplication and factors responsible for special colonization as common surface properties.     

Peptidoglycan synthesis and structure in Staphylococcus haemolyticus expressing increasing levels of resistance to glycopeptide antibiotics.

The structures of cytoplasmic peptidoglycan precursor and mature peptidoglycan of an isogenic series of Staphylococcus haemolyticus strains expressing increasing levels of resistance to the glycopeptide antibiotics teicoplanin and vancomycin (MICs, 8 to 32 and 4 to 16 microg/ml, respectively) were determined. High-performance liquid chromatography, mass spectrometry, amino acid analysis, digestion by R39 D,D-carboxypeptidase, and N-terminal amino acid sequencing were utilized. UDP-muramyl-tetrapeptide-D-lactate constituted 1.7% of total cytoplasmic peptidoglycan precursors in the most resistant strain. It is not clear if this amount of depsipeptide precursor can account for the levels of resistance achieved by this strain. Detailed structural analysis of mature peptidoglycan, examined for the first time for this species, revealed that the peptidoglycan of these strains, like that of other staphylococci, is highly cross-linked and is composed of a lysine muropeptide acceptor containing a substitution at its epsilon-amino position of a glycine-containing cross bridge to the D-Ala 4 of the donor, with disaccharide-pentapeptide frequently serving as an acceptor for transpeptidation. The predominant cross bridges were found to be COOH-Gly-Gly-Ser-Gly-Gly-NH2 and COOH-Ala-Gly-Ser-Gly-Gly-NH2. Liquid chromatography-mass spectrometry analysis of the peptidoglycan of resistant strains revealed polymeric muropeptides bearing cross bridges containing an additional serine in place of glycine (probable structures, COOH-Gly-Ser-Ser-Gly-Gly-NH2 and COOH-Ala-Gly-Ser-Ser-Gly-NH2). Muropeptides bearing an additional serine in their cross bridges are estimated to account for 13.6% of peptidoglycan analyzed from resistant strains of S. haemolyticus. A soluble glycopeptide target (L-Ala-gamma-D-iso-glutamyl-L-Lys-D-Ala-D-Ala) was able to more effectively compete for vancomycin when assayed in the presence of resistant cells than when assayed in the presence of susceptible cells, suggesting that some of the resistance was directed towards the cooperativity of glycopeptide binding to its target. These results are consistent with a hypothesis that alterations at the level of the cross bridge might interfere with the binding of glycopeptide dimers and therefore with the cooperative binding of the antibiotic to its target in situ. Glycopeptide resistance in S. haemolyticus may be multifactorial.     

Species-specific sensitivity of coagulase-negative Staphylococci to single antibiotics and their combinations

The activity of beta-lactam antibiotics (oxacillin, cloxacillin, cephalotin), vancomycin, gentamicin and rifampicin applied in vitro individually and in combination against 37 nosocomial methicillin-resistant strains of coagulase-negative staphylococci (CNS) was assessed to demonstrate the heterogeneity of this group of bacteria and estimate the chance of the efficacy of such therapy. The strains belonged to four species: Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus cohnii, Staphylococcus hominis. They originated from a hospital environment and from the skin of medical staff of the intensive care unit of a paediatric ward at a university hospital. All strains were methicillin-resistant, according to CLSI standards, but individual strains differed in MIC(ox) values. Susceptibility to other tested antibiotics was also characteristic for the species. The increased susceptibility to antibiotics in combinations, tested by calculating the fractional inhibitory concentration (FIC) index, concerned 26 out of 37 investigated strains and it was a feature of a particular species. Combinations of vancomycin and cephalotin against S. epidermidis and oxacillin with vancomycin were significant, as well as cephalotin and rifampicin in growth inhibition of multiresistant S. haemolyticus strains.     

Characteristics of the MRSA clone with reduced susceptibility to vancomycin

The MIC of vancomycin was determined for all S. aureus strains isolated during 1997 in one hospital. MIC values for most isolates were in the range of 0.5-2 mg/l. In 18 strains, MIC was = 6 mg/L. All these strains were MRSA. Recently described VISA strains possessed MIC values for vancomycin equal or higher than 8 mg/l and such strains were not detected in the investigated group. Although strains with MIC = 6 mg/l are not VISA, but they are candidate for reduced vancomycin susceptibility, e.g. during therapy in compromised patients. Analysis of DNA of these strains by pulsed-field gel electrophoresis (PFGE) revealed that 15 of them shared a significant similarity, allowing to place them in the same group. The comparison data of phage patterns as well as antibiotic resistance patterns strongly suggest that all these strains were derivatives of a single clone.     

屎肠球菌的临床分布与耐药性分析

目的了解医院屎肠球菌的临床分布和耐药情况,为临床抗感染的预防与治疗提供参考。方法回顾性分析1999年1月至2011年12月临床标本中分离的1161株屎肠球菌;用WHONET5．6软件分析耐药率变迁。结果临床分离的1161株屎肠球菌,在同期分离的1944株肠球菌属中占59．72％。主要分离自尿液和血液,分别占40．91％和26．87％;主要分离自外科病区、内科病区、ICU和儿科病区的菌株,分别占29．37％、25．15％、13．95％和13．53％;屎肠球菌对多种抗菌药物耐药,对万古霉素、替考拉宁和利奈唑胺的耐药率较低,分别为1．04％、0．94％和1．85％。结论屎肠球菌在临床的分离率逐年增加,已成为医院内感染的主要病原菌之一,其多药耐药和高耐药现象相当严重,目前万古霉素、替考拉宁和利奈唑胺仍然是治疗肠球菌属引起感染的有效药物。     

Prevalence of AA(6')-APH(2")Ia gene among high-level aminoglycoside resistant Enterococci and Staphylococci

According to new reports the AAC (6')-APH (2")Ia gene is no longer the only gene encoding resistance to gentamycin in Gram-positive cocci and therefore the current method for predicting synergism aminoglycosides with bacterial cell wall active agents in this bacteria may need revision. To further our knowledge of aminoglycoside resistance mechanism in Gram-positive cocci in Gdańsk region we tested presence of AAC (6')-APH (2")Ia gene among 22 enterococcal (E. faecalis) and 41 staphylococcal (S. haemolyticus, S. aureus, S. epidermidis) gentamycin-resistant isolates. Presence of AAC (6')-APH (2")Ia gene varied from 50% (n = 6) in gentamycin-resistant S. epidermidis, 80% (n = 10) in gentamycin resistant S. haemolyticus 88% in methicillin-resistant Staphylococcus aureus (MRSA) (n = 25). In Enterococcus faecalis this gene was noticed only in 59% (n = 22) of gentamycin-resistant isolates. These results suggest that spread of resistance gene among different species is limited and AAC (6')-APH (2")Ia mediated gentamycin-resistance mechanism is more common among MRSA and Staphylococcus haemolyticus.     

Infectivity and resistance to antibiotics of bacterial strains isolated from patients hospitalised in intensive care units

The aim of this study was to evaluate the frequency of isolation and antimicrobial resistance testing of bacterial strains isolated from clinical specimens from patients hospitalized in three Intensive Care Units in Wroc?aw. The susceptibility of bacteria (107 strains) to selected antibiotics was determined. The results clearly show that non-fermentative rods were identified as the main agents causing pneumonia (58% of isolates). The second commonest pathogens were Gram-positive cocci (29%). The P. aeruginosa and E. cloacae strains were resistant to ampicillin, amoxicillin/clavulanate, cefuroxime and cefotaxime. All isolates of A. baumanii were susceptible only to imipenem. The rods of K. pneumoniae and E. coli were resistant to ampicillin, about 55% strains of both bacteria were sensitive to other antibiotics, except piperacillin/tazobactam, imipenem and ciprofloxacin. About 90% of methicillin resistant S. epidermidis strains were resistant to all antibiotics, except vancomycin (100% isolates were sensitive). ESBL were detected among E. cloace, K. pneumoniae and E. coli. We found P. aeruginosa rods producing MBL.     

凝固酶阴性葡萄球菌致新生儿败血症临床分析

目的了解本地区凝固酶阴性葡萄球菌（CNS）致新生儿败血症的病原学及耐药性状况,用以指导临床治疗。方法回顾性分析64株CNS致新生儿败血症血培养的病原学及耐药性。结果64株CNS中以表皮葡萄球菌和溶血葡萄球菌为主;耐甲氧西林凝固酶阴性葡萄球菌（MRCNS）39株,分离率为60．9％,β-内酰胺酶检出率达100％,MRCNS对青霉素、红霉素、苯唑西林耐药率最高,对利福平、呋西地酸、替考拉宁、喹奴普汀／达福普汀等耐药率均较低;甲氧西林敏感凝固酶阴性葡萄球菌（MSCNS）25株,分离率为39．1％,13-内酰胺酶检出率为44％,MSCNS对大多数抗生素敏感;64株CNS中未检测到万古霉素耐药株。结论新生儿败血症中CNS以表皮葡萄球菌和溶血葡萄球菌为主,MRCNS检出率高且呈多重耐药,应重视对其监测与控制。     

Susceptibility to antimicrobial agents and genotypic relatedness of enterococcal strains isolated from patients and hospital environment

The aim of this study was to evaluate antibiotic susceptibility of Enterococcus sp. strains isolated from two hospitals in ?ód?, during 2005-2006. The second goal was to determine possible transmission of these strains within hospital wards by using melting profile PCR. Enterococcal strains were identified to species according standard microbiological methods. There was isolated 159 strains of E. faecalis, 51 strains of E. faecium and two E. avium, 1 E. durans. Susceptibility to antimicrobial agents was tested by disc diffusion method. None of these strains was resistant to vancomycin, teicoplanin or linezolid. There was high percentage of strains resistant to aminoglicosides, 22% of E. faecalis strains, and 54.9% of E. faecium strains, respectively. Additionally it was shown that 11.7% of E. faecium is resistant to chinuprisin-dalfopristin. The strains with similar pattern of resistance to antibiotics and fenotypic characteristics were genotyped by mpPCR. This technique was useful to confirm relatedness of bacterial strains suspected of being spread within hospital wards.     

肠球菌的临床感染与耐药性分析

目的了解温州医学院附属第一医院临床分离主要肠球菌的分布及其对常用抗菌药物的耐药现状,以指导临床合理用药。方法对2008年至2011年临床分离的635株粪肠球菌和屎肠球菌的标本来源和药敏结果进行回顾性分析。结果各种临床标本中两种肠球菌的分布比例存在差异,总体以尿液标本所占比例最多,且屎肠球菌的总体分离率高于粪肠球菌。粪肠球菌对利奈唑胺、氨苄西林、万古霉素、呋喃妥因和替考拉宁的耐药率都在5．0％以下,对莫西沙星和青霉素G的耐药率也仅为7．0％和6．7％;屎肠球菌对莫西沙星、左旋氧氟沙星、环丙沙星、氨苄西林、青霉素G和红霉素的耐药率都在90．0％以上,对利奈唑胺、万古霉素、替考拉宁和奎奴敏感。粪肠球菌的多重耐药株占总数的26．4％,屎肠球菌的多重耐药株占总数的78．2％。结论粪肠球菌和屎肠球菌对15种抗菌药物的耐药情况不同,屎肠球菌具有更高的耐药率和更广的耐药谱。临床应根据药敏试验的结果合理选择抗菌药物,以防止耐药菌株的产生和播散。     

下呼吸道感染流行菌及其耐药性

目的:研究本院下呼吸道感染流行菌及其耐药性,为合理使用抗生素提供依据.方法:对下呼吸道感染流行菌进行统计分析.结果:检出病原菌716株,革兰阴性杆菌为主要菌种,而G杆菌中铜绿假单胞菌占13.69%,肺炎克雷伯菌占8.8%,不动杆菌属占8.4%.除嗜麦芽寡养单胞菌外,G杆菌对亚胺培南、阿米卡星敏感性高.G 球菌以表皮葡萄球菌、溶血葡萄球菌为主要菌种,耐甲氧西林表皮葡萄球菌(MRSS)的检出率为85.3%,耐甲氧西林溶血葡萄球菌的检出率为91.6%.真菌分离呈增多趋势,占所有病原菌的23.28%.结论:下呼吸道感染流行菌药敏显示耐药水平较多,临床医生应根据药敏结果合理选择抗生素,以利于疾病的治疗.     

Antimicrobial susceptibility of staphylococci isolated from otitis externa in dogs

Samples were obtained from 65 unmedicated adult dogs, processed for isolation of Staphylococcus species and tested for susceptibility to penicillin G, gentamicin, oxacillin, tetracycline, trimethoprim-sulphamethoxazole, streptomycin, ampicillin and rifampin. Forty-four isolates were obtained, which represents 67.7% of samples. Coagulase-negative species were most commonly found, and the most frequently isolated staphylococcus species were Staph. epidermidis and Staph. aureus. Other species, such as Staph. simulans, Staph. haemolyticus, Staph. saprophyticus and Staph. intermedius were also isolated. Resistance to antibiotics was frequently observed, with 90.9% of the isolates showing resistance to at least one drug. The most active antimicrobial agents against staphylococci isolated from otitis externa of dogs were rifampin and oxacillin. Multidrug resistance was a common finding, and one strain of Staph. haemolyticus species, was resistant to all tested antimicrobial agents. Resistance to three or more different drugs was a common finding, observed in 16 strains (36.4%) of both coagulase-positive and coagulase-negative staphylococci. This study highlights the emergence of cases of otitis externa determined by coagulase-negative staphylococcus strains and once more emphasizes the need for bacterial culture with species identification and susceptibility testing of swab specimens from the ear canal in order to choose appropriate antimicrobial agents.