Pathogenicity and Antimicrobial Resistance in Coagulase-Negative Staphylococci

The coagulase-negative staphylococci (CoNS) group was considered saprophytic or rarely pathogenic for many years. Since the first case of septicemia caused by CoNS, there has been a progressive increase in the prevalence of healthcare-associated infections caused by CoNS. The CoNS group has emerged as one of the main causes of nosocomial infections related to vascular catheters and prostheses, especially among immunocompromised patients. This gradual increase in infections is due to the change in the relationship between patients and procedures since CoNS are closely related to devices implanted in the human body. CoNS are successful in colonizing the host because they have several virulence mechanisms, such as biofilm formation and production of enzymes and toxins, in addition to several mechanisms of resistance to antimicrobials. Despite their great clinical relevance, few studies have focused on CoNS’s pathogenicity and resistance to antimicrobials, which reveals the current need to better understand the factors by which this group became pathogenic to humans and other animals. This review aims to synthesize the aspects related to the pathogenicity and antimicrobial resistance in CoNS.

Identification of Quinolones/Fluoroquinolones Resistance Genes from Staphylococci Strains Isolated at the University Hospital of Brazzaville, Republic of the Congo

Staphylococci strains, like the majority of bacterial strains, have developed the resistance to several antibiotics, including Quinolones and Fluoroquin-olones In the Republic of the Congo, cases of resistance leading to treat-ment failures have been observed during the treatment of staphylococcal infections with antibiotics in hospitals. The objective of this study was to identify the Quinolone/Fluoroquinolone resistance genes from staphylo-cocci strains isolated in hospitals. A total of 51 strains of Staphylococci were isolated, including 16 (31.37%) community strains, and 35 (68.62%) clinical strains. 46 strains of Staphylococcus aureus (S. aureus) and 5 SCNs were identified. A total of 34 DNA fragments from different strains resistant to Quinolones/Fluoroquinolones, including 21 (61.67%) DNA fragments from clinical S. aureus and 13 (38.23%) from community SCN strains were analyzed by the molecular method (genotypic detection) by PCR. The genotypic results made it possible to identify the gyrA, grLA and norA genes and to show that these genes are involved in the resistance of the strains to the various antibiotics used. The grLA gene was the most identified gene with a frequency of 75%. The gyrA and grLA genes have been identified in Staphylococcus aureus and Coagulase Negative Staphy-lococci. The norA gene, on the other hand, has only been identified in Staphylococcus aureus. Two mechanisms are essentially involved in the resistance of Staphylococci to quinolones/Fluoroquinolones, the mecha-nism of resistance by efflux, which takes place thanks to a transmembrane protein coded by the norA gene and by point mutations (substitution and deletion of acids or nucleotides) observed within the protein and nucleic sequences of the chromosomal gyrA and grLA genes.

A comparative evaluation of methicillin-resistant staphylococci isolated from harness racing-horses,breeding mares and riding-horses in Italy

Objective:To investigate the prevalence of methicillin-resistant staphylococci(MRS)which is a potencial risk factor of transmission between animals and humans in different types of horses(harness racing-horses,breeding mares and riding-horses)and to compare the antimicrobial resistance of the isolates.Methods:A total of 191 healthy horses,housed at different locations of the Campania Region(Italy),were included in the study.Nasal swab samples were collected from each nostril of the horses.The mecA gene was detected by a nested PCR technique.Antibiotic susceptibility was tested for each isolate.Results:MRS was isolated from nasal samples of 68/191(35.6%;95%CI:28.9%-42.9%)healthy horses.All isolates were coagulase-negative with the exception of two coagulase-positive MRS strains,identified as Staphylococcus aureus and Staphylococcus pseudintermedius.2/83(2.4%;95%,CI:0.4%-9.2%).Interestingly,both coagulase-positive MRS isolates were from harness racing-horses.These horses also presented a significantly higher positivity for MRS(53.3%;95%CI:40.1%-66.1%)than the breeding mares and riding-horses groups.Antibiotic susceptibility testing showed difference between isolates due to different origins except for an almost common high resistance to aminopenicillins,such as ampicillin and amoxicillin.Conclusions:It can be concluded that harness racing-horses may act as a significant reservoir of MRS as compared to breeding mares and riding-horses.

Antibiotic Effect on Planktonic and Biofilm-Producing Staphylococci

The pathogenic effect of Staphylococci is due to extra-cellular factors and properties such as adherence and biofilm production. The nature of the biofilm and the physiological properties of biofilm-producing bacteria result in an inherent antibiotic resistance and require further investigation. Two hundred and sixty Staphylococcal strains were cultured from 600 clinical specimens obtained from hospitalized patients. Among these, 155 were identified as coagulase-positive (CPS) and 105 as coagulase-negative (CNS) staphylococci. Staphylococcal strains were tested for biofilm production using the tissue culture plate (TCP) method. TCP detection showed that of the 155 CPS, 124 (80%) were biofilm producers, while 63 (60%) of the 105 CNS were biofilm producers. Biofilm-producing strains were scanned by scanning electron microscope (SEM) to confirm biofilm formation, study biofilm production, and examine antibiotic effects on biofilm formation. Disc diffusion method was used to study resistance of planktonic and biofilm-forming cells to antibiotics. Planktonic cells were less resistant to antibiotics than biofilm-forming cells. Microbroth dilution method and a new BioTimer assay were used to determine antibiotic MICs affecting planktonic and biofilm cells. Both methods showed that the MICs for planktonic cells were less than that for biofilm cells. The BioTimer assay was therefore found to be sensitive, accurate, and reliable, with results in agreement with those from the broth dilution method and SEM.

Coagulase Gene Typing with Emphasis on Methicillin-Resistance Staphylococci: Emergence to Public Health

Emerging antimicrobial resistance among CNS is a concern in veterinary and human medicine. Coagulase test is considered as the key test to differentiate staphylococci to two groups, coagulase positive staphylococci (CPS) and coagulase negative staphylococci (CNS). A total of 200?Staphylococci?strains were isolated with percentage 66.7% (200/300) from quarter milk samples. The total of?S. aureus?strains are 70 with percentage 35% (70/200). Among 70 strains of?S. aureus, 30 strains are coagulase positive?S. aureus?with percentage 43% (30/70) and coagulase negative?S. aureus?57% (40/70). CNS other than?S. aureus?was detected with percentage 65% (130/200) from subclinical mastitic cows. We examine sixty isolates of staphylococci recovered from subclinical mastitis in dairy cattle which divided as ten isolates of coagulase positive?S. aureus?(CP?S. aureus), ten isolates of coagulase negative?S. aureus(CN?S. aureus) and forty isolates of coagulase negative staphylococci (CNS) which identified using API-Staph Kits as?S. chromogenes,?S. simulans,?S. haemolyticus,?S. epidermidis?and?S. cohnii.?The genotypic detection of?coa?gene and?mecA gene was screened in CP?S. aureus, CN?S. aureus?and CNS.

Batumin—A Selective Inhibitor of Staphylococci—Reduces Biofilm Formation in Methicillin Resistant <i>Staphylococcus aureus</i>

The antibiotic batumin, produced by Pseudomonas batumici, has been shown to be highly active against 123 type and reference strains and clinical isolates of 30 Staphylococcus species (including MRSA and small colony variants—(SSCVs) of S. aureus, S. epidermidis and S. haemolyticus). Batumin activity against these bacteria did not depend on the species, origin or resistance to other antibiotics and its MIC was 0.0625 - 0.5 mg/ml. Batumin influence on biofilm formation was studied in clinical isolates of S. aureus, S. epidermidis and S. intermedius. Addition of batumin at a concentration of half of the MIC in the broth, i.e. 0.125 μg/ml, decreased the biofilm of 16 out of 20 S. aureus strains to varying degrees. Batumin was more effective against Staphylococcus strains with strong biofilm formation. Using atomic-force microscopy, it could be shown that batumin reduced the number of S. aureus ATCC 25923 adherent cells more than fourfold. The adherent cells of staphylococci were visualized as monolayers of separate islets. A detailed study of the surface of bacterial cells treated with batumin allowed to establish significant reduction of their roughness values. Observed values were typical for planktonic S. aureus cells. The obtained data explain one of the mechanisms of the antimicrobial activity of batumin, which is based оn preventing the formation of S. aureus biofilm. As such, batumin could be considered as an agent offering opportunities for the treatment of staphylococcal biofilm-associated infections.

凝固酶阴性葡萄球菌在发酵食品中的应用

凝固酶阴性葡萄球菌(CNS)是一类广泛存在于自然界中的革兰氏阳性球菌,是自然发酵肉制品、乳酪、腌鱼等食物生境中的优势菌群。CNS作为优势生产菌群,可以赋予发酵食品良好的风味、色泽及质地,是有助于提高发酵食品质量的有益微生物菌群。因生产特性良好,开发CNS食品发酵剂的研究一直被业界关注。然而,CNS在食品工业生产中存在的潜在安全隐患也引起不少学者的担忧。本文基于近年来发酵食品中CNS的研究,综述CNS对发酵食品品质形成的影响。同时,对其用作发酵剂时可能存在的安全隐患进行阐述,以期为推进CNS发酵剂的筛选及其安全性评估提供参考。

Determination of antimicrobial resistance profile and inducible clindamycin resistance of coagulase negative staphylococci in pediatric patients: the first report from Iran

Background:Currently,coagulase negative staphylococci(CoNS)have got much attention as a serious health problem especially in neonates and children.High incidence of antibiotic resistance,in particular methicillin resistance,has complicated the treatment of these organisms.The aim of this study is to determine the susceptibility to different antimicrobial agents and the prevalence of macrolides-lincosamides-streptogramins B(MLS_(B))resistance in CoNS isolates obtained from pediatric patients.Methods:Totally 157 CoNS isolates from various clinical samples were examined for antibiotic resistance using disk diffusion and E-test methods.Double-disk test was applied to detect constitutive and inducible MLSB resistance(cMLS_(B)and iMLS_(B))phenotypes.Results:Resistance to methicillin was seen in 98(62.4%)isolates.All isolates were susceptible to vancomycin and linezolid.The prevalence of resistance to antibiotics tested was as follows:fusidic acid(n=58,36.9%),gentamicin(n=73,46.5%),ciprofloxacin(n=81,51.6%),clindamycin(n=112,71.3%),erythromycin(n=129,82.2%)and trimethoprim/sulfamethoxazole(n=133,84.7%).iMLS_(B)phenotype was seen in 14(8.9%)isolates,and 18(11.5%)and 98(62.4%)isolates showed MS and cMLS_(B)phenotypes,respectively.We observed that high overall antibiotic resistance rates were associated significantly with methicillin resistance.Conversely,iMLS_(B)phenotype was correlated neither with methicillin resistance nor with invasiveness.Conclusion:Given the similarity observed between the prevalence of iMLS_(B)and MS phenotypes,the performance of disk diffusion induction test is strongly recommended in our region.

Microbiological Quality of Freshly Prepared, Packaged Fruit and Milk Juices Sold in Cafés, Shops, and Supermarkets in Hargeisa, Somaliland

Background: Due to their delicious taste, high nutritional content, and health benefits, fruit juices are well-known drinks in many countries and are now an essential component of the modern diet. Objective: Determining the microbiological quality of both packaged and freshly made fruit and milk juices. Method: The spread-plate approach was employed to isolate and count the bacteria. 90 ml of sterile peptone water were blended with 10 ml of well-mixed, packed, and freshly made fruit juices. The samples were sequentially diluted (101 - 105) in accordance with the Indian Manual of Food Microbiological Testing Methods. Results: From eight samples of imported packaged fruit and milk juice, the average of total coliform, staphylococci, and viable bacterial counts were zero, 1.39 × 102, and 2 × 102 CFU/ml, respectively. In contrast, from three samples of locally produced fruit and milk juice, the average of total coliform, staphylococci, and viable bacterial counts were zero, 5.83 × 102, and 2.73 × 103 CFU/ml, respectively. Four samples of handmade prepared fruit and milk juices had a mean of total coliform, staphylococci, and viable bacterial count of 1.441 × 104, 4.1 × 103, and 2.35 × 105 CFU/ml, respectively. Conclusion: 33.3% of the results from microbiological analysis of freshly made fruit and milk juices met the permissible range of the Revised Microbiological Standards for Fruit and Vegetables and Their Products, which were published in 2018 and as well as the Hong Kong Center for Food Safety, whereas 66.7% of the microbiological analyses of freshly prepared fruit and milk juices were above the permissible reference range of GSO standard 2000. 12.5% of the investigated imported and packed fruits and milk juices had one failed test (TSC), which was above the acceptable limit, 87.5% of the tested samples of fruit and milk juices fulfilled the necessary standards of TCC, TVBC, and TSC. 100% of the tested locally manufactured fruit and milk juices complied with TSC, TCC, and TVBC requirements. All investigations showed that freshly made fruit and milk juices were heavily contaminated (Total viable bacterial count, total coliform count, and total staphylococcus count). .

肉源凝固酶阴性葡萄球菌对多环芳烃的消减作用

多环芳烃(polycyclic aromatic hydrocarbons,PAHs)是一类食品中广泛存在的危害物,降低其含量有利于提升产品安全性。在模拟体系中考察不同肉源凝固酶阴性葡萄球菌对PAHs的消减作用,筛选出消减PAHs能力最强的菌株,并探讨其作用机理。研究结果表明:在受试菌株中,马胃葡萄球菌(Staphylococcus equorum)E1对模拟体系中PAHs的消减效果最强(P<0.05)。在S.equorum不同细胞组分中,全细胞提取液(whole cell extracts,WCE)和细胞碎片悬液均对PAHs有显著的降低作用(P<0.05)。进一步酶处理发现,WCE中关键消减物质是蛋白类物质;同时,在WCE中检测到了PAHs降解酶活性,这表明S.equorum消减PAHs存在生物降解途径。另一方面,热灭活处理使S.equorum对PAHs消减能力显著提升(P<0.05);通过傅里叶变换红外光谱分析,发现S.equorum的WCE存在与物理吸附PAHs相关的官能团,说明S.equorum消减PAHs存在物理吸附途径。因此,S.equorum可通过生物降解和物理吸附两种作用途径消减PAHs。研究为生物法消减食品中的多环芳烃提供了新途径。

广东省部分地区鸡源凝固酶阴性葡萄球菌的耐药基因检测及耐药性分析

目的 了解广东省部分地区鸡源凝固酶阴性葡萄球菌(Coagulase-negative Staphylococci, CNS)的耐药情况。方法 对广东省部分地区养鸡场324份鸡肛拭子进行CNS的分离鉴定,并对所分离的菌株进行12种抗生素的最小抑菌浓度(Minimum inhibitory concentration, MIC)检测以及11种耐药基因检测。结果 共分离出58株CNS,占检出葡萄球菌的92.1%。其中,检出率最高的CNS为松鼠葡萄球菌(24.1%)。MIC结果显示CNS分离株对青霉素、环丙沙星和苯唑西林的耐药水平较高,分别为79.3%、74.1%和67.2%。此外,CNS分离株的多重耐药率高达70.7%,耐药谱种类多至20种。CNS的耐药基因检出率最高的为gryA(60.3%),gryA主要介导喹诺酮类药物如环丙沙星的耐药表型。耐药基因的基因组型复杂(28种),有53.4%的分离株携带两种以上的耐药基因。结论 本研究揭示了广东部分地区鸡源CNS对喹诺酮类、β-内酰胺类抗生素有较强的耐药性,并且喹诺酮类的耐药基因携带率较高,该地区鸡源CNS耐药情况复杂多样。本研究成果对指导本地区鸡场科学合理使用抗菌药物具有重要意义。

万古霉素异质性耐药葡萄球菌的分离及其药物敏感性分析

目的 调查葡萄球菌对万古霉素异质性耐药亚群发生频率以及对常见抗生素的药物敏感性。方法 利用菌群分析法筛选万古霉素异质性耐药葡萄球菌亚群 ,Microscan Microbiology System对萄萄球菌分型和鉴定并分析对 19种常用抗生素的药物敏感性。结果 115株耐甲氧西林的葡萄球菌 ,9株对万古霉素耐药亚群的 MIC8～ 12 mg/ L,其发生频率为 10 - 4～ 10 - 7,其中 3株金葡球菌 ,6株溶血性葡萄球菌。传至 7代后万古霉素 MIC6 4 mg/ L。对 19种抗生素药敏显示 ,万古霉素敏感 2株、中介 7株 ,敏感率 2 2 .2 % ;利福平敏感7株 (MIC≤ 1mg/ L)、中介 1株 (MIC=2 mg/ L)及耐药 1株 (MIC>2 mg/ L)、敏感率 77.8% ;SMZ/ TMP敏感 6株 (MIC≤ 2 / 38mg/ L)、耐药 3株 (MIC>2 / 38mg/ L) ,敏感率 6 6 .7% ;克林霉素敏感 3株 (MIC=0 .5或≤ 0 .2 5 )、耐药 6株 (MIC>2 mg/ L) ,敏感率 33.3% ;四环素敏感 3株 (MIC≤ 2 mg/ L)、耐药 6株 (MIC>8mg/L) ,敏感率 33.3% ;左氧氟沙星敏感 1株 (MIC≤ 2 mg/ L)、耐药 8株 (MIC>4 mg/ L) ,敏感率 11.1%。其余 13种抗生素耐药。结论 下呼吸道分离的葡萄球菌存在一定频率的对万古霉素异质性耐药株 ,可能是万古霉素治疗失败的原因之一 ,利福平、SMZ/ TMP具有较好的敏感性 。

凝固酶阴性葡萄球菌所致血行感染的相关研究

目的分析凝固酶阴性葡萄球菌（CNS）所致血行感染的相关因素，为临床诊治CNS菌血症提供参考依据。方法对本院2004年1月～2005年5月间血中分离到CNS143例病历进行回顾性分析。结果143例患者中79例为CNS菌血症的确诊病例（55．24%），血培养阳性出现时间20．8h，早于污染菌（31h）（P〈0．01）；病原菌与污染菌对常用抗菌药物敏感性差异无显著性；多瓶血样本均在48h内培养出CNS，全部为菌血症的确诊病例。结论CNS污染率较高，护士在采集血培养标本时，尽可能减少污染；血中分离出CNS时应综合分析临床和实验室资料，做出正确判断后，再用药，避免滥用抗菌药物。

耐甲氧西林凝固酶阴性葡萄球菌及糖肽类耐药的检测与分析

目的了解中日友好医院临床耐甲氧西林凝固酶阴性葡萄球菌(MRCNS)糖肽类耐药的流行情况和耐药机制,为MRCNS医院感染的预防与控制提供可靠依据。方法头孢西丁纸片法、mecA基因PCR检测MRCNS;万古霉素耐药确证试验筛选对万古霉素敏感性下降的凝固酶阴性葡萄球菌(CNS),E-test法检测其MIC及多重PCR检测其van基因。结果CNS对头孢类、β-内酰胺类、氨基糖苷类、大环内酯类、克林霉素类抗菌药物耐药程度较高;52株CNS菌中头孢西丁纸片法与mecA基因检测MRCNS的符合率为96.2%,mecA基因阳性率为92.3%;256株CNS菌中筛选出4株异质性耐万古霉素葡萄球菌(VRS),均为MRCNS,未检出vanA、vanB、vanC1及vanC2基因。结论对VRS和MRCNS进行有效的实验室检测与院内监测并采取有效措施预防与控制其传播是非常重要的。

发酵香肠中的菌种分离及鉴定

从发酵香肠混合发酵剂中分离菌株 ,确定用于发酵香肠生产的菌株名称 ,并研究了其生理生化性质。实验结果表明乳酸菌中 3 2MRS的生长速度最快 ,3MRS的生长速度最慢 ;2种葡萄球菌的生长速度差异不显著。在筛选的菌株中 3MRS的最适生长温度为 35℃ ,其余 6种菌株的最适生长温度为 30℃。

湿疹皮炎中葡萄球菌及对常用抗生素耐药性状况与硝酸益康唑/曲安奈德霜治疗的观察

为了探讨湿疹皮炎中金黄色葡萄球菌(金葡菌)及其它葡萄球菌定殖或感染,以及对某些常用外用抗生素敏感性,对149例湿疹皮炎类皮肤病患者的皮损进行细菌分离,并对分离出的125株葡萄球菌进行6种抗生素的药敏试验。临床上同时使用硝酸益康唑/曲安奈德霜治疗,观察疗效。结果149例患者有121例查出细菌,共有135株菌,其中金葡菌58株(42.96%)等。细菌对抗生素的敏感率以利福平最高(82.4%)。硝酸益康唑/曲安奈德霜治疗,3周内痊愈率88.6%。比较带金葡菌者与未带金葡菌者的疗效,两组结果无显著性差异。本研究显示湿疹皮炎类皮肤病皮损中带菌率高,疾病与细菌可能有重要关系。治疗这类疾病时,合用敏感性高的抗菌药物很有帮助。

血培养凝固酶阴性葡萄球菌阳性的临床意义

目的 :评价血培养中凝固酶阴性葡萄球菌 (CNS)阳性的临床意义。方法 :对本院 1995～ 1999年血中分离到CNS的70例住院患者进行回顾性分析 ,判定是菌血症还是血样本污染。结果 :70例患者中 37例 (5 2 .9% )为菌血症 ,其入侵部位 15例 (4 0 .5 % )为静脉插管及人工装置 ,8例 (2 1.6 % )为术后伤口感染 ,4例为呼吸道 ,4例为脐带 ,1例为眼部 ,5例不明。 37例菌血症主要发生于重症监护病房、新生儿病房、外科病房和血液科病房。入院 48h内检出的CNS中 ,2 4株 (39.3% )为污染菌 ,入院 48h以后检出的CNS ,均为污染菌 (9株 ) ;污染菌的检出时间显著长于病原菌 (36 .2h/2 1.9h ,P =0 .0 1)。病原菌与污染菌对青霉素、苯唑西林、庆大霉素、环丙沙星、万古霉素的敏感性差异无显著性 (P >0 .2 5 )。在 15例由静脉插管及人工装置引起的菌血症中 ,10例经拔除导管后 ,菌血症得到控制 ;另 5例还同时使用了万古霉素 ,菌血症才得以控制。结论 :CNS血培养阳性时污染率较高 ,需综合临床和实验室的资料判定其临床意义 。

大蒜素联合头孢唑林或苯唑西林对葡萄球菌的抗菌作用

目的：评价大蒜素分别与头孢唑林或苯唑西林联合用药,对于临床分离的革兰阳性球菌,包括金黄色葡萄球菌（staphylococcus aureus）和表皮葡萄球菌（staphylococcus epidermidis）的体外联合抗菌效应.方法：采用棋盘法设计,微量肉汤稀释法测定.测定不同浓度组合的二组抗菌药物对40株临床分离的革兰阳性球菌的最低抑菌浓度,并计算FIC指数,也称部分抑菌浓度（Fractiona inhibitory concentration index）判定联合效应.FIC≤0.5 为协同作用,0.5＜FIC≤1为相加作用,1＜FIC≤2为无关作用,FIC＞2为拮抗作用.结果：大蒜素与头孢唑林或苯唑西林联合应用后,其MIC50显著降低.FIC指数分布：FIC≤0.5占55%～75%;0.5＜FIC≤1占20%～40%;1＜FIC≤2占0～5.88%;FIC＞2为0.结论：头孢唑林或苯唑西林这2种抗菌药物与大蒜素联合用药后,对革兰阳性球菌基本表现为协同作用和相加作用.

2011—2013年临床血培养病原菌的分布及耐药性变迁

目的了解福建医科大学附属第一医院血液培养标本中病原菌分布及耐药性变化规律。方法回顾性分析2011年至2013年从32779份血培养标本中分离的3098例阳性标本中病原菌种类及其药敏检测结果。结果病原菌血培养阳性率为9.45%(309 8/32779),居前5位的是大肠埃希菌(20.92%,648/3098)、凝固酶阴性葡萄球菌(16.59%,514/3098)、肺炎克雷伯菌(11.14%,345/3098)、金黄色葡萄球菌(6.23%,193/3098)和鲍曼不动杆菌(6.10%,189/3098)。但从2013年开始出现对碳青霉烯类药物耐药的肺炎克雷伯菌菌株,其对亚胺培南和美罗培南的耐药率分别为3.18%和3.16%;凝固酶阴性葡萄球菌、金黄色葡萄球菌尚未发现对万古霉素耐药。结论血培养分离的细菌菌种呈多样化,大肠埃希菌仍然是血流感染的首要致病菌,且其耐药率有上升趋势;凝固酶阴性葡萄球菌和肺炎克雷伯菌的分离率有所增加。应继续开展病原菌分布及其耐药性监测,用于指导临床医生合理使用抗生素。