Methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii: An unexpected difference in epidemiologic behavior

Background: The Dutch guideline on hospital policy for the prevention of nosocomial spread of methicillin-resistant Staphylococcus aureus (MRSA) states that patients transferred from hospitals abroad must be placed in strict isolation immediately on admission to a hospital in the Netherlands. Three patients colonized with both MRSA and a multiresistant Acinetobacter were transferred from hospitals in Mediterranean countries to 3 different hospitals in the Netherlands. Despite isolation precautions, Acinetobacter spread in 2 of the 3 hospitals, whereas nosocomial spread of MRSA did not occur. Methods: For outbreak analysis, the Acinetobacter isolates, identified as Acinetobacter baumannii by the use of amplified ribosomal DNA restriction analysis, were comparatively typed by 4 methods. Comparison of isolation measures in the hospitals was performed retrospectively. Results: In the 2 hospitals in which nosocomial spread of Acinetobacter occurred, most of the epidemiologically related isolates were indistinguishable from the index strains. In these 2 hospitals, isolation measures were in concordance with those recommended for the prevention of contact transmission. The precautions of the hospital in which no outbreak occurred included the prevention of airborne transmission. Conclusions: Precautions recommended for multiresistant gram-negative organisms are insufficient for the prevention of nosocomial spread of multiresistant Acinetobacter . The airborne mode of spread of acinetobacters should be taken into account, and guidelines should be revised accordingly. (AJIC Am J Infect Control 1998;26:544-51)     

Methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii on computer interface surfaces of hospital wards and association with clinical isolates

Background  

Computer keyboards and mice are potential reservoirs of nosocomial pathogens, but routine disinfection for non-water-proof computer devices is a problem. With better hand hygiene compliance of health-care workers (HCWs), the impact of these potential sources of contamination on clinical infection needs to be clarified.     

Control of naeethicillin-resistant Staphylococcus aureus in a pediatric burn unit

Background: Control of methicillin-resistant Staphylococcus aureus (MRSA) is particularly difficult in burn units, which are often cited as sources of hospital-wide MRSA outbreaks. We developed a successful MRSA control program and document here its apparent effectiveness in controlling MRSA transmission in a pediatric burn unit.Methods: An MRSA control program that included surveillance culturing, clinician feedback, flexible, site-specific isolation, and a list of known carriers was consistently applied in a pediatric burn unit through a 7-year period. Microbiology reports of MRSA isolates from patients and environmental surfaces and records of all patients from whom MRSA was isolated were reviewed.Results: During calendar years 1985 through 1991, a total of 991 acutely burned children were admitted to the Boston unit of the Shriners Burns Institute. Forty MRSA cases (4%) were identified. One patient both had MRSA at admission and met our criteria for nosocomial MRSA. Of the remaining 39 patients, 11 had MRSA at admission and 28 had nosocomial MRSA. There were 17 wound infections, two cases of pneumonia, and two bloodstream infections. No deaths were attributed to MRSA sepsis.Conclusion: An MRSA control program including surveillance culturing, clinician feedback, flexible, site-specific isolation, and a list of known carriers is associated with a low rate of nosocomial MRSA in a pediatric burn unit.     

Immuno-detection of Staphylococcus aureus biofilm on a cochlear implant

Case presentation:   

A 46-year-old man suffering from progressive deafness since childhood received a Clarion 90 K cochlear implant with the HiRes^? preformed electrode in his left ear in October 2006. A persistent Staphylococcus aureus infection failed to be treated with corticoids, amoxicillin/ clavulanate, ciprofloxaxin, and rifampin. The processor was removed on July 2007.     

Echocardiography for the diagnosis of Staphylococcus aureus infective endocarditis

Staphylococcus aureus bacteremia (SAB) is a serious and growing problem. A longstanding controversy in infectious diseases has centered around the duration of therapy for patients with SAB. Fortunately, the refinement of echocardiography and the creation of new diagnostic criteria have aided in the diagnosis of infective endocarditis in patients with SAB. These advancements have resulted in the development of an algorithm that combines clinical, microbiologic, and echocardiographic findings to stratify patients with SAB into different treatment regimens.     

Quinolone resistance inPseudomonas aeruginosa andStaphylococcus aureus. Development during therapy and clinical significance

This review focuses on published information on the experimental as well as clinical data on the emergence of quinolone resistant isolates. In the course of clinical use of fluoroquinolones, only a sporadic emergence of quinolone resistance has been noted. The resistant organisms emerged particularly in certain clinical settings where large numbers of organisms frequently causing chronic infections are present and/or in loci where quinolone concentrations may not be optimal. In terms of occurrence in individuals, quinolone resistance has emerged most frequently in hospitalized and nursing-home patients with identifiable risk factors. Epidemiological studies revealed that in nearly all the cases studied one or one predominating quinolone resistant clone was selected that was horizontally transmitted. Thus, the emergence of quinolone resistance is not due to an independent selection of resistant strains in a number of patients, but to the clonal spread of one strain once it has acquired quinolone resistance. Therefore, the rate of quinolone resistance is very likely to be lower than reported.Die publizierten präklinischen sowie klinischen Daten zur Chinolonresistenz sind synoptisch dargestellt. Im Verlauf der klinischen Anwendung von Fluorochinolonen wurde bislang nur sporadisch das Auftreten Chinolon-resistenter Stämme beobachtet. Diese resistenten Stämme traten vor allem unter solchen klinischen Bedingungen auf, unter denen entweder hohe Bakterienzellzahlen chronische Infektionen verursachen und/oder in solchen Infektlokalisationen, in denen die Chinolonkonzentrationen nicht optimal sein können. Bezogen auf die individuelle Wahrscheinlichkeit des Auftretens Chinolon-resistenter Stämme treten diese vorrangig in hospitalisierten Patienten oder Pflegeheimbewohnern mit identifizierbaren Risikofaktoren auf. Epidemiologische Studien ergaben, daß in nahezu allen untersuchten Fällen ein oder ein vorherrschender Chinolon-resistenter Klon selektiert worden war, der sich anschließend horizontal ausbreitete. Somit ist das Auftreten einer Chinolonresistenz nicht auf eine unabhängige Selektion einer Vielzahl resistenter Stämme in entsprechend vielen Patienten zurück-zuführen, sondern vielmehr auf eine klonale Ausbreitung eines einzigen Stammes sobald dieser eine Chinolonresistenz erworben hat. Folglich ist die Rate der Chinolonresistenz sehr wahrscheinlich geringer als publiziert.     

Methicillin-resistant Staphylococcus aureus prevalence in community in the east Delhi area

Methicillin-resistant Staphylococcus aureus (MRSA) continues to be an important nosocomial pathogen. Various hospital-based studies have described the incidence of MRSA and carriage of this organism in health care workers. Recently, even community acquired S. aureus strains have shown resistance to methicillin. This changing epidemiology prompted us to study the nasal carriage of MRSA amongst healthy individuals in a community. A total of 319 nasal swabs were taken from both anterior nares of healthy parents attending a well-baby clinic. Of these, 94 yielded growth of S. aureus (29.4%). Out of these 94 isolates, 17 (18.1%) were found resistant to oxacillin. These strains showed low level resistance only to clindamycin.     

Extended broad-spectrum beta-lactamases conferring transferable resistance to newer beta-lactam agents in Enterobacteriaceae: hospital prevalence and susceptibility patterns

Before 1985 at the Pitié-Salpêtrière Hospital in Paris (2,400 beds), resistance to cefotaxime in clinical isolates of Enterobacteriaceae involved only species producing inducible class 1 beta-lactamase. Between November 1985 and April 1987, however, 62 isolates (57 of Klebsiella pneumoniae and five of Escherichia coli) showed decreased susceptibility to cefotaxime (mean MIC, 8-16 micrograms/mL). The transferability of cefotaxime resistance in E. coli K12 was demonstrated for 15 of 16 selected isolates. By isoelectric focusing using iodometric detection with 20 mg of ceftriaxone/100 mL and determination of substrate and inhibition profiles, three beta-lactamases mediating cefotaxime resistance were identified as SHV-2 (isoelectric point [pI] 7.6), CTX-1 (pI 6.3), and "SHV-2-type" or SHV-3 (pI 6.98). The three beta-lactamases hydrolyzed penicillins and cephalosporins (including cefotaxime and ceftriaxone) and were therefore designated "extended broad-spectrum beta-lactamases" (EBS-Bla). The enzymes conferred to derivatives a high level of resistance to amoxicillin, ticarcillin, piperacillin, and cephalothin and a decreased degree of susceptibility (i.e., MICs increased by 10- to 800-fold) to cefotaxime, ceftriaxone, ceftazidime, and aztreonam. These beta-lactamases did not affect the activity of cephamycins (cefoxitin, cefotetan, moxalactam) or imipenem. Synergy between clavulanate or sulbactam (2 micrograms/mL) and amoxicillin was greater against derivatives producing EBS-Bla than against those producing TEM-1, TEM-2, or SHV-1; this synergy was greater with clavulanate than with sulbactam against derivatives producing SHV-2 and the SHV-2-type enzyme but was similar with clavulanate and sulbactam against those producing CTX-1. A double-disk synergy test performed with cefotaxime and Augmentin disks (placed 30 mm apart, center to center) seemed a useful and specific test for the detection of strains producing EBS-Bla.     

Antibiotic susceptibility of Atopobium vaginae

Background  

Previous studies have indicated that a recently described anaerobic bacterium, Atopobium vaginae is associated with bacterial vaginosis (BV). Thus far the four isolates of this fastidious micro-organism were found to be highly resistant to metronidazole and susceptible for clindamycin, two antibiotics preferred for the treatment of BV.     

异质性万古霉素中介的金黄色葡萄球菌感染发生率及相关危险因素分析

  目的 调查复旦大学附属中山医院（中山医院）异质性万古霉素中介的金黄色葡萄球菌(hVISA)的发生率,了解hVISA菌群对新型抗生素的敏感性,研究下呼吸道hVISA感染的危险因素和影响病死率的相关因素。方法 收集2008年1月至2010年11月中山医院临床分离的甲氧西林耐药的金黄色葡萄球菌（MRSA）菌株,采用脑心浸出液琼脂（BHIA）筛选平板和宏量Etest试条检测法（macroEtest,MET）进行hVISA的筛选,改良菌群分析策略-曲线下面积(PAP-AUC) 确证hVISA。肉汤稀释法测定MRSA对万古霉素、替考拉宁和利奈唑胺的最小抑菌浓度（MIC）,用SPSS16.0比较hVISA和万古霉素敏感的金黄色葡萄球菌（VSSA）在不同MIC区间的分布差异。通过病例调查表收集筛选的hVISA病例和VSSA组的临床信息,使用t检验、Mann-Whitney检验、χ²检验及Fisher精确检验进行相关危险因素。结果 从457株MRSA菌株中经含5 mg/L替考拉宁的BHIA （BHIA5T）、含6 mg/L万古霉素的BHIA（BHIA6V）法筛选的hVISA为105株(23.0%),MET法筛选出23株hVISA(5.0%),PAP-AUC法确证的hVISA为21株(4.6%)。hVISA对万古霉素和利奈唑胺均敏感,hVISA和VSSA对万古霉素的MIC分别为（1.76±0.16） mg/L 和（1.09±0.07） mg/L（P<0.01）,hVISA和VSSA在不同MIC区间的分布差异无统计学意义（P>0.05）。单因素分析发现,hVISA组合并慢性阻塞性肺疾病者（5/11）明显高于VSSA组（14.3%,P< 0.05),但未发现hVISA感染与临床病死率相关。结论 中山医院hVISA的总体发生率为4.6%,血标本中hVISA的发生率高达12.5%。hVISA对万古霉素和利奈唑胺均为敏感,但hVISA的万古霉素MIC高于VSSA者。下呼吸道内发生hVISA感染与慢性阻塞性肺疾病可能有关。        

Emergence of SCCmec Type IV as the Most Common Type of Methicillin-Resistant Staphylococcus aureus in a University Hospital

Abstract Background:   The epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) has dramatically changed over the last decade by the emergence of community-associated MRSA (CA-MRSA). Recent studies indicate that these strains have already spread to hospitals. To evaluate if SCCmec type IV and Panton–Valentine leukocidin (PVL) are unambiguous markers of CA-MRSA, we analyzed 77 sporadic MRSA strains isolated, in our low MRSA incidence university hospital, from inpatients between 2000 and 2004. Methods:   MRSA strains were analyzed by staphylococcal cassette chromosome mmecec (SCCmec) typing, PCR for PVL genes and pulsed-field gel electrophoresis (PFGE). MRSA was classified in HA-MRSA or CA-MRSA according to Centers for Disease Control and Prevention (CDC) criteria. Antimicrobial susceptibility testing was performed using microbroth dilution method following CLSI recommendations. Results:   Among 77 sporadic single-patient strains, SCCmec types I–IV and four subtypes were identified. Type IV/IVA was most common (42.9%).The distribution of SCCmec types changed over the years. Type IV/IVA strains increased from 33.3% in 2000 to 57.9% in 2004. Type IV strains were resistant to ciprofloxacin in 81.8%, and in 9.1% to tobramycin while type IVA strains were 100% resistant to both antimicrobials. In contrast, non-type IV/IVA strains were resistant to ciprofloxacin in 86.4%, and in 75.0% to tobramycin. Only one strain was PVL positive and harbored SCCmec type III variant. By PFGE analysis, the 33 SCCmec type IV/IVA strains comprised 12 distinct genotypes. 36.4% of 11 CA-MRSA and 43.9% of 66 HA-MRSA harbored SCCmec type IV/IVA. Conclusion:   Type IV/IVA has become the most common SCCmec type in inpatients of our university hospital. The SCCmec type IV/IVA is present in both CA-MRSA and HA-MRSA limiting its use as a marker for CA-MRSA.