临床分离肠球菌的耐药性研究

目的了解近3年来粤东地区临床分离的肠球菌的耐药特征,为预防耐万古霉素肠球菌（VRE）的产生和控制VRE播散提供理论依据和实验基础。方法收集临床分离的215株肠球菌,细菌鉴定及药敏试验采用VITEK-60全自动细菌鉴定仪。结果215株肠球菌中,尿标本中分离肠球菌75株（35％）;痰液中分离出34株（16％）。粪肠球菌141株（65．5％）,屎肠球菌74株（34．5％）。粪肠球菌对万古霉素、呋喃妥因、青霉素G和莫西沙星的敏感率较高,70％～100％;对红霉素和四环素的敏感性较差,11％～33％。屎肠球菌对万古霉素敏感性较好为100％,四环素为62％;而对呋喃妥因、高链霉素、青霉素和左氧氟沙星等敏感性较差（5％～47％）。未检出耐万古霉素肠球菌。结论粤东地区近3年来未发现耐万古霉素肠球菌。肠球菌对各种常见抗生素敏感程度呈下降趋势。屎肠球菌较粪肠球菌耐药性更高。应根据细菌学培养结果合理用药,减少耐药菌株的发生率。     

Antibiotic susceptibility patterns as aids in classification and characterization of gram-negative anaerobic bacilli

Patterns of susceptibility of gram-negative anaerobic bacilli to antibiotics have been found to be distinctive and of significant help in classification and identification. Five major groups of gram-negative anaerobic bacilli have been defined on the basis of morphological and biochemical criteria. Antibiotic sensitivity patterns conform to these groupings and provide additional taxonomic criteria. The Bacteroides fragilis group is resistant to penicillin G, whereas the other groups are generally sensitive. B. fragilis strains are relatively sensitive to erythromycin, whereas the Sphaerophorus necrophorus group is resistant. B. melaninogenicus strains, B. oralis, and Fusobacterium are all more sensitive to kanamycin and neomycin than the other two groups. Kanamycin is more active against Fusobacterium strains than neomycin, but less active against all other groups. Colistin or polymyxin B is useful for distinguishing between the resistant B. fragilis and the sensitive S. necrophorus. Antibiotic susceptibility determinations may be more readily performed in clinical laboratories than certain biochemical tests recommended for differentiation of the gram-negative anaerobic bacilli and may serve as helpful adjuncts to morphological and biochemical observations in classifying and characterizing these organisms. The use of standardized procedures for antibiotic susceptibility tests is essential if comparable results are to be obtained in different laboratories.     

In Vitro Susceptibility of Brucella to Various Antibiotics

A series of 27 strains of six species of Brucella was tested for susceptibility in vitro to a representative cross section of antibiotics in current use. The activity against each species was plotted, with the cumulative per cent of strains inhibited indicated for each concentration. As a class, the tetracycline antibiotics were the most effective. Erythromycin, gentamicin, streptomycin, and kanamycin, as well as rifampin, were quite active. The penicillin-cephalosporin group, with the exception of ampicillin, was comparatively ineffective, as were the polypeptides and the miscellaneous group of chloramphenicol, lincomycin, cycloserine, and sulfadiazine. Species differences were noticeable, with some strains of B. canis being considerably more resistant to streptomycin and the tetracyclines than B. suis and B. abortus. B. melitensis, B. ovis, and B. neotomae were intermediate in antibiotic susceptibility.     

Comparative activity of tobramycin and gentamicin against Pseudomonas,Proteus and Providencia species.

Tobramycin is a new antibiotic resembling gentamicin. We measured the minimal inhibitory concentrations of these two antibiotics against five bacterial species that cause hospital-acquired infections and are resistant to many presently available antibiotics. The organisms tested were 500 strains of Pseudomones aeruginosa, 100 strains of each of Proteus rettgeri and Pr. morganii, 50 strains of Pr. vulgaris and 250 strains of Providencia stuartii. Tobramycin was 2 to 4 times more active than gentamicin against Ps. aeruginosa; all except 6 of 70 strains resistant to 4 mug/ml of gentamicin were sensitive to 4 mug/ml of tobramycin. The two antibiotics showed a similar degree of activity against the other four species. Tobramycin promises to be of particular value in the treatment of Pseudomonas infections.     

Antibiotic-resistant strains of Enterococcus isolated from Swedish and Danish retailed chicken and pork

Two hundred and seventy-seven Enterococcus isolates representing the predominating enterococcal flora of retailed chicken and pork were identified by phenotypical features, and by random amplified polymorphic DNA. The resistance to nine different antibiotics was determined. Enterococcus faecium was the most frequently occurring species in both Swedish and Danish chicken. Enterococcus faecalis and unidentified groups of Enterococcus dominated in pork. Seventy-three per cent of the Enterococcus isolates from Swedish chicken were resistant to one or more of the tested antibiotics. The corresponding values for Swedish pork, Danish chicken and Danish pork were 9%, 55% and 14%, respectively. Tetracycline resistance was most frequent in isolates from Danish pork and Swedish chicken, while erythromycin resistance was most frequent in Danish chicken. Strains with acquired vancomycin resistance, mainly Ent. faecium , were found only on Danish chicken, except for one isolate from Danish pork. All vancomycin-resistant isolates contained the van A gene. Vancomycin resistance could be transferred to a vancomycin-sensitive Ent. faecium strain from four of nine tested donor strains.     

Investigation of antibiotic and antibacterial agent cross-resistance in target bacteria from homes of antibacterial product users and nonusers

AIM: To describe the relationship between antibiotic and antibacterial resistance in environmental and clinical bacteria from home environments across geographical locations, relative to the use or nonuse of antibacterial products, with a focus on target organisms recognized as potential human pathogens. METHODS AND RESULTS: In a randomized study, environmental and clinical samples were collected from the homes of antibacterial product users (n=30) and nonusers (n=30) for the isolation of target bacteria for antibiotic and antibacterial testing in three geographical areas (in USA and UK). Isolates were tested for antibiotic susceptibility, with selected antibiotic-resistant and antibiotic-susceptible isolates tested against four common antibacterial agents (triclosan, para-chloro-meta-xylenol, pine oil and quaternary ammonium compound). Prequalified users and nonusers at each location were randomly selected after meeting exclusionary criteria. Of 1238 isolates, more target bacteria were recovered from nonuser than user homes. Of Staphylococcus aureus isolates (n=33), none showed resistance to oxacillin or vancomycin; for Enterococcus sp. (n=149), none were resistant to ampicillin or vancomycin; and for Klebsiella pneumoniae (n=54)and Escherichia coli (n=24), none were resistant to third generation cephalosporins. Antibiotic resistance to one or more of the standard test panel drugs for Gram-positive and Gram-negative target bacteria was comparable between nonuser and user homes for both environmental and clinical isolates [e.g. resistance of environmental coagulase-negative (CN) Staphylococcus sp. was 73.8% (124/168) from nonuser homes and 73.0% (111/152) from user homes, and Enterobacteriaceae other than E. coli, 75.9% (186/245) from nonuser homes compared with 78.0% from user homes]. Of 524 Gram-negatives tested against preferred/alternative drugs, 97.1% (509/524) were susceptible to all antibiotics, across both groups. Isolates of S. aureus, Enterococcus sp. and CN Staphylococcus sp. susceptible to all preferred treatment drugs showed comparable antibacterial minimum inhibitory concentration (MIC) results between nonuser and user home isolates. For Gram-positives resistant to one or more preferred drugs, greatest resistance to antibacterial active ingredients was found in the nonuser group. For Gram-negatives, the antibacterial MIC data were comparable for isolates that were fully susceptible and resistant to one or more preferred/alternative treatment antibiotics. CONCLUSIONS: The results showed a lack of antibiotic and antibacterial agent cross-resistance in target bacteria from the homes of antibacterial product users and nonusers, as well as increased prevalence of potential pathogens in nonuser homes. SIGNIFICANCE AND IMPACT OF THE STUDY: It refutes widely publicized, yet unsupported, hypotheses that use of antibacterial products facilitates the development of antibiotic resistance in bacteria from the home environment.     

临床分离肠球菌的分布特征及耐药性分析

目的:了解我院临床分离肠球菌的分布特征及耐药现状,为临床合理用药提供依据。方法:对我院2010年1月至2012年12月期间所有临床分离的肠球菌分布情况及药敏结果进行回顾性分析。结果:临床共分离肠球菌242株,粪肠球菌分离率(55.0%)高于屎肠球菌(40.9%),屎肠球菌分离率有增高的趋势。标本来源以尿液(62.9%)、分泌物(10.3%)、血液(6.9%)为主。肠球菌对万古霉素、替考拉宁的敏感性最高,均高于90%。发现耐万古霉素的肠球菌(VRE)7株,其中5株同时耐高浓度的氨基糖苷类抗生素(HLAR);对克林霉素、复方磺胺、阿米卡星、庆大霉素、妥布霉素、苯唑西林耐、头孢西丁耐药率最高,均高于95%。屎肠球菌对青霉素类、氨苄西林、红霉素、呋喃妥因、环丙沙星耐药率均高于粪肠球菌;对四环素、奎努普丁/达福普汀耐药率低于粪肠球菌。结论:肠球菌是临床感染重要病原菌,且具有多重耐药性,屎肠球菌和粪肠球菌耐药水平差异较大,临床应根据药敏结果合理选择抗菌药物。     

Activity of four antimicrobial cocktails for tissue allograft decontamination against bacteria and Candida spp. of known susceptibility at different temperatures

Several antimicrobial cocktail solutions of differing composition and concentrations are widely used to decontaminate viable banked tissue allografts at different temperatures and times of exposure. We compared the efficiency of four cocktails comprising nine antimicrobials to kill suspensions of a panel of 27 strains of 13 bacterial species, and 3 Candida spp. at 4, 22 and 37 °C for 24 h. All but one bacterial strains were susceptible to one or more of the agents tested individually at concentrations at least fourfold below the recommended susceptibility breakpoint minimum inhibitory concentrations for drug/species combinations. Candida lusitaniae was resistant to nystatin and amphotericin. The concentrations of several of the cocktail constituents were often greatly in excess (50–1,000-fold) of that required to inhibit the growth of susceptible strains. All cocktails were ineffective against a pan-resistant strain of Enterococcus faecium and one of the four cocktails failed to kill two strains of methicillin resistant Staphylococcus aureus. Each cocktail was most efficient at 37 °C, less so at 22 °C, and poorly active at 4 °C. We conclude that the practice of decontamination of tissues with antimicrobials at low temperatures is not supported by in vitro susceptibility tests.     

Effect of lysozyme on mycobacteria

The effect of lysozyme on the growth of several strains of mycobacteria was examined at pH 5.0-7.0 in Dubos medium containing various concentrations of lysozyme (100-2,000 microgram/ml). Mycobacterium smegmatis and M. phlei were susceptible to lysozyme at pH 5.0-7.0. The effect of lysozyme was marked between pH 6.0 and 7.0 and the colony counts were reduced to approximately 0.1-10% after incubation with 100 micrograms of lysozyme per ml for 48 hr. At pH 5.0, 10-40% of the organisms survived treatment with 1,000 micrograms of lysozyme per ml for 48 hr. M. bovis strain BCG, M. tuberculosis, and M. fortuitum appeared to be more resistant to lysozyme than M. smegmatis and M. phlei. M. smegmatis and M. phlei did not contain detectable amounts of poly-L-glutamic acid, although the susceptibility of the mycobacteria to lysozyme did not correlate with the amounts of the polymer in the cell walls. The role of lysozyme in animal infections with so-called saprophytic mycobacteria is discussed.     

尿培养中病原菌分布及耐药性分析

目的研究大连市中心医院2007年1月至2012年9月尿培养中常见病原菌（真菌除外）的分布及其耐药性,为临床治疗尿路感染提供诊断及用药依据。方法采用MicroScan—Walkaway40全自动微生物鉴定药敏分析仪和ATBExpression自动细菌鉴定仪及K—B纸片法药敏试验,应用WHONET5．4软件对结果进行回顾性统计分析。结果五年间尿培养中共分离出病原菌1012株（真菌除外）,其中革兰阴性菌802株（79．2％）,主要是大肠埃希菌538株（53．2％）、肺炎克雷伯菌95株（9．5％）、铜绿假单胞菌51株（5．1％）、奇异变形杆菌30株（2．9％）、鲍曼不动杆菌26株（2．6％）。革兰阳性菌210株（20．8％）,主要是粪肠球菌86株（8．6％）,屎肠球菌83株（8．2％）,凝固酶阴性葡萄球菌21株（2．1％）,金黄色葡萄球菌13株（1．3％）。抗生素敏感试验中碳青霉烯类（亚胺培南及美洛培南）对肠杆菌科细菌大肠埃希菌、肺炎克雷伯菌及奇异变形杆菌抗菌活性最强,无耐药菌株,对非发酵菌中铜绿假单胞菌和鲍曼不动杆菌耐药率为30％～40％,革兰阳性菌对糖肽类（万古霉素、替考拉宁）和利奈唑胺等抗菌药物高度敏感。结论应当根据主要易感菌种类及其抗生素敏感试验结果指导临床合理使用抗生素。     

Susceptibility and frequency of selected groups of bacteria isolated in 2001 from patients at the Holy Cross Cancer Center

The aim of the presented study was the analysis of microbiological data obtained from patients hospitalized in The Holly Cross Cancer Center in Kielce in 2001. The frequency of important nosocomial pathogens in selected specimens and their susceptibility to antibiotics were determined. The strains were identified by using commercial tests (bioMerieux) and their antibiotic susceptibility patterns were performed by disc diffusion technique. The most prevalent bacteria were Gram-negative rods of Enterobacteriaceae family (43%), mainly Escherichia coli. Only 2.7% strains of isolated Escherichia coli isolated from clinical specimens collected from hospitalized patients were beta-lactamase--positive (ESBL+). The second important group of microorganisms were Staphylococci, followed by Enterococcus spp., Pseudomonas aeruginosa and Candida spp. About twenty eight percent of Staphylococcus aureus isolates were resistant to methicillin.     

Sensitivity of Corynebacterium diphtheriae isolated in Saint-Petersburg to antibacterial drugs]

One hundred and thirty strains of Corynebacterium diphtheriae isolated in St. Petersburg (42 toxigenic and 88 nontoxigenic) were tested with the method of serial dilutions in solid media for their susceptibility to 20 antibacterial drugs. The MICs of the drugs for the isolates ranged from < or = 0.015 to > or = 32.0 micrograms/ml. 13 per cent of the isolates was resistant at least to one antibacterial drug. The isolates resistant to erythromycin (11.5 per cent), lincomycin (11.5 per cent) and trimethoprim (8.5 per cent) were most frequent. 3 isolates (2.3 per cent) had multiple resistance to 8 drugs: benzylpenicillin, ampicillin, oxacillin, chloramphenicol, erythromycin, lincomycin, trimethoprim, and nitroxolin. No significant differences in the susceptibility of the toxigenic and nontoxigenic strains of C. diphtheriae were detected. Gentamicin, rifampicin, tetracycline, doxycycline and pefloxacin were the most active antibiotics.     

In vitro activity of cefamandole, cefoxitin, cefuroxime, and carbenicillin, alone and in combination with aminoglycosides against Serratia marcescens.

Synergistic antibiotic studies were undertaken to compare the effectiveness of two new beta-lactamase resistant cephalosporins, cefamandole, and carbenicillin, with four aminoglycosides against clinical strains of Serratia marcescens. The strains demonstrated various combinations of resistance and/or susceptibility to the antibiotics tested. Tobramycin was the most effective aminoglycoside when used in combination with beta-lactam antibiotics. Carbenicillin and cefamandole demonstrated similar activity with aminoglycosides in synergy experiments. Tobramycin-carbenicillin was found to be the superior pairs as indicated by the total number of strains inhibited. This combination was the only one effective against certain high drug resistant strains and the strain resistant to all four aminoglycosides. Carbenicillin or cefamandole with tobramycin exhibited comparable activity against multiple drug resistant organisms. However, mutants significantly more resistant to cefamandole developed during susceptibility testing. The findings of this study have clinical relevance for treating infections by this formidable pathogen.     

Antimicrobial susceptibility of lactic acid bacteria isolated from a cheese environment

In the production of the Spanish traditional blue-veined Cabrales cheese, lactic acid bacteria strains free of antibiotic resistance that have a transferrable capacity are necessary as components of a specific starter. To select for these bacteria, the minimum inhibitory concentration (MIC) of 12 antibiotics and 2 mixtures (containing beta-lactamase inhibitor and penicillin) were determined by microbroth and agar dilution techniques in 146 strains belonging to the genera Lactococcus, Enterococcus, Lactobacillus, and Leuconostoc. The antibiotic-resistance profiles of Lactococcus and Enterococcus species were different from those of Lactobacillus and Leuconostoc, but clear genus- or species-associated patterns were not observed. Cefoxitin and metronidazole were not effective against bacteria of these genera. The MICs of beta-lactam antibiotics for lactobacilli and leuconostoc isolates were higher than those for lactococci and enterococci, but no strain was clinically resistant. All lactobacilli and leuconostoc isolates were resistant to high levels of vancomycin, a type of resistance not seen among the tested members of the genera Lactococcus and Enterococcus. The majority of the observed resistance appeared to be either intrinsic or nonspecific, although some strains of Lactococcus lactis, Enterococcus spp., and Lactobacillus spp. were resistant to antibiotics, such as chloramphenicol, erythromycin, clindamycin, or tetracycline.     

鲍曼不动杆菌院内感染调查与耐药性分析

目的 研究鲍曼不动杆菌院内感染情况及对常用抗生素的敏感性。方法 采用Microscan Walk Away-40全自动微生物仪及配套药敏复合板进行细菌鉴定与药敏试验。结果 46株不动杆菌中有35株为鲍曼不动杆菌,占76．09％。主要分布在ICU、康复科、呼吸内科。标本主要以脓、痰及呼吸道分泌物为主。药敏结果显示：亚胺培南、头孢吡肟、阿米卡星对鲍曼不动杆菌高度敏感,但3代头孢菌素大多数耐药。结论 鲍曼不动杆菌易引起伤口、呼吸道继发感染,且耐药现象严重,诊断与治疗有赖于细菌培养和药物敏感结果,应引起临床的高度重视。一旦发现感染株,必须迅速采取控制措施,避免引起医院感染的暴发流行。     

Partial characterization of enterocin MR99 from a corn silage isolate of Enterococcus faecalis

AIMS: To assess the inhibitory activity on Gram-positive and Gram-negative bacteria of several species of enterococci recovered from a natural corn silage. METHODS AND RESULTS: The inhibitory activity of strains of Enterococcus faecalis (58), Enterococcus faecium (35), Enterococcus gallinarum (3) and Enterococcus casseliflavus (4) were studied employing indicator strains from various sources (clinical, food and ATCC). Enterococcus faecalis MR99, the only strain with inhibitory activity, inhibited other enterococci, Listeria spp., Staphylococcus aureus, Clostridium spp., Bacillus spp., Escherichia coli, Shigella sonnei and Shigella flexneri. The bacterium contained only one conjugative pheromone-responsive plasmid. The partially chromatography-purified MR99 enterocin (PPE) had a molecular weight of approx. 5000 Da and a pI of 6.2, was sensitive to proteolytic enzymes and could be extracted in benzene and butanol. It appeared stable to adjustment of pH 4.0, 5.0, 6.0, 7.0 and 8.0 and was resistant to heat. Inactivation was at 15 min at 121 degrees C. Enterocin MR99 was bactericidal on strains of Listeria monocytogenes, Staph. aureus, and bovine mastitis agents, it was bacteriostatic on E. coli. Although enterocins MR99 and AS48 have inhibitory activity on Gram-negative bacilli, PCR studies demonstrated a lack of relationship between them. CONCLUSIONS: The active component had a protein nature, was resistant to heat and presented a wide inhibitory spectrum. SIGNIFICANCE AND IMPACT OF THE STUDY: The biological properties of Ent. faecalis MR99 suggest that this strain merits further investigations so it can be applied in human and veterinary health programmes.     

Antimicrobial activity of mupirocin, daptomycin, linezolid, quinupristin/dalfopristin and tigecycline against vancomycin-resistant enterococci (VRE) from clinical isolates in Korea (1998 and 2005)

It is a hot clinical issue whether newly approved antimicrobial agents such as daptomycin, linezolid, quinupristin/dalfopristin (synercid) and tigecycline are active enough to be used for infections caused by vancomycin resistant bacteria. We performed susceptibility tests for mupirocin, which is in widespread clinical use in Korea, and four new antimicrobials, daptomycin, linezolid, quinupristin/dalfopristin and tigecycline, against vancomycin-resistant Enterococcus faecalis and Enterococcus faecium isolated from Korean patients in 1998 and 2005 to evaluate and compare the in vitro activity of these antimicrobials. Among these agents, quinupristin/dalfopristin, which is rarely used in hospitals in Korea, showed relatively high resistance to several vancomycin-resistant enterococci (VRE) isolated in 2005. Likewise, daptomycin, linezolid and tigecycline have not yet been in clinical use in Korea. However, our results showed that most of the 2005 VRE isolates were already resistant to linezolid and daptomycin (highest minimum inhibitory concentration (MIC) value >100 microg/ml). Compared with the other four antimicrobial agents tested in this study, tigecycline generally showed the greatest activity against VRE. However, four strains of 2005 isolates exhibited resistance against tigecycline (MIC >12.5 microg/ml). Almost all VRE were resistant to mupirocin, whereas all E. faecium isolated in 1998 were inhibited at concentrations between 0.8 to approximately 1.6 microg/ml. In conclusion, resistances to these new antimicrobial agents were exhibited in most of VRE strains even though these new antibiotics have been rarely used in Korean hospitals.     

Antibiotic resistance dynamics and isolation rate of staphylococci and enterococci from patients of reconstructive surgery units

The dynamics of isolation of staphylococci and enterococci from clinical material of patients and their antibiotic susceptibility within a 5-year period (2005-2009) was analysed. 5990 isolates were tested: 1250 isolates of Staphylococcus aureus, 3268 isolates of S. epidermidis, 1005 isolates of Enterococcus faecalis and 467 isolates of E. faecium. Grampositive infections were shown to be prevailing within the last 2-3 years, the nosocomial epidermal staphylococci more and more replacing S. aureus (the ratio of S. epidermidis and S. aureus in 2009 was 3.3). The isolation rate of E. faecalis significantly increased (by 3.5 times) and the ratio of E. faecalis and E. faecium in 2009 was 4.3. The microflora composition with respect to the isolation source was analysed and its clinical significance was estimated. The study of the antibiotic susceptibility showed that oxacillin had its own specific niche, while antibiotics active against resistant grampositive cocci, such as rifampicin, fusidic acid, fluoroquinolones (moxifloxacin), cefoxitin, as well as amoxicillin/clavulane in infections due to E. faecalis, might be considered as the drugs of choice. In the treatment of nosocomial infections, when the etiological role of MRSA or VRE is suspected or confirmed, the complex therapy should obligatory include the most active antibiotics (vancomycin or linezolid among them).     

Antibacterial activity of enterococci strains against Vibrio cholerae

Thirty-seven strains of enterococci isolated from milk and milk products from Santa Fe (Argentina) region were tested for antagonistic activity against Vibrio cholerae 01 and non-01. Seven of 17 strains of Enterococcus faecalis , five of 10 strains of Enterococcus faecium and four of 10 strains of Enterococcus durans produced inhibition zones against the indicator species. The activity of the antibacterial compounds was completely destroyed by treatment with trypsin and pronase E in most cases (only the supernatant fluids of a few strains remained weakly active after the treatment), but was resistant to heat treatment at 100°C during 10 and 30 min. When the 10-fold concentrated supernatant fluids were added to a fresh culture of sensitive cells it produced a rapid inactivation. According to these preliminary tests, different strains of enterococci produced compounds with slightly different antivibrio properties, and these compounds were heat-resistant and had a predominantly proteinaceous nature.     

Antibiotic resistance in Staphylococci isolated from the vaginas of captive female Leontopithecus (Callitrichidae-Primates)

The purpose of this study was to provide current data on Staphylococcus species from the vaginas of clinically normal captive lion tamarins and to determine the antimicrobial susceptibility of these isolates. Samples were collected from 25 adult lion tamarins, processed to isolate Staphylococcus species, and tested for susceptibility to penicillin G, gentamicin, chloramphenicol, tetracycline, trimethoprim-sulfamethoxazole, streptomycin, ampicillin, and rifampicin. Isolates with the typical characteristics of the genus Staphylococcus were recovered from all 25 samples. Coagulase-negative species were the most common (68% of the isolates), and the most frequently isolated species (10 samples) was S. simulans. Other coagulase-negative species, including S. saprophyticus (n=5), S. epidermidis (n=1), and S. arlettae (n=1), were also recovered. Coagulase-positive Staphylococci were obtained from eight animals (six of from the S. aureus species and two from S. intermedius). Resistance to antibiotics was frequently observed, and 88% of the isolates (23 samples) showed resistance to at least one drug. Resistance to penicillin G was a common finding, and the most active antimicrobial agents were chloramphenicol and gentamicin. Coagulase-positive strains were more frequently resistant to antibiotics (79.7%, average=6.4 drugs) than coagulase-negative strains (38.2%, average=3.0 drugs). The high frequency of resistance observed in those isolates is surprising and very alarming. A detailed history of the use of antimicrobial drugs in these subjects did not reveal any previous exposure to any of the tested antibiotics that could justify the observed resistance rate.