Community-acquired methicillin-resistant Staphylococcus aureus: Review

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) have emerged worldwide. These CA-MRSA are different from classical hospital-acquired MRSA. They share common characteristics: they affect mainly young subjects, without past medical history. The majority of strains produce the Panton-Valentine leukocidin. They are mainly responsible for suppurative skin infections and rarely for invasive infections such as necrotizing pneumonia. The situation in the US is alarming with a main circulating clone the USA300 clone, whereas in Europe, the diffusion of CA-MRSA strains remains limited. It is important to take advantage of the experience acquired from the US to limit the potential spread of such CA-MRSA strains.     

Community-acquired methicillin-resistant Staphylococcus aureus prostatic abscess

We present a 43-year-old man with a history of intravenous drug abuse who presented to the emergency department with a 5-week history of lower urinary tract symptoms. On digital rectal examination, a firm prostate with exquisite tenderness was noted. Computed tomography scan of the pelvis with contrast demonstrated a 4.4 by 2.7-cm prostatic abscess in the right lobe. Suppurative fluid was expressed from the right prostatic lobe during transurethral resection of the prostate. Cultures of blood and suppurative prostatic fluid grew methicillin-resistant Staphylococcus aureus.     

Importance of methicillin-resistant Staphylococcus aureus eradication in carriers to prevent postoperative methicillin-resistant Staphylococcus aureus surgical site infection

Although infrequent, postoperative methicillin-resistant Staphylococcus aureus (MRSA) surgical site infection (SSI) is associated with significant morbidity and cost. Previous studies have identified the importance of MRSA screening to diminish the risk of postoperative MRSA SSI. The current study quantifies the importance of eradication of the MRSA carrier state to prevent MRSA SSI. Beginning February 2007, all admissions to an 800-bed tertiary care hospital were screened for MRSA by nasal swab using rapid polymerase chain reaction-based testing. Patients found to be nasal carriers of MRSA were treated with 2 per cent mupirocin nasal ointment and 4 per cent chlorhexidine soap before surgery. The subset of patients undergoing procedures that are part of the Surgical Care Improvement Project (SCIP) were followed for MRSA SSI (n = 8980). The results of preoperative MRSA screening and eradication of the carrier state were analyzed. Since the initiation of universal MRSA screening, 11 patients undergoing SCIP procedures have developed MRSA SSI (0.12%). Of these, six patients (55%) had negative preoperative screens. Of the five patients with positive preoperative screens, only one received treatment to eradicate the carrier state. In patients who develop MRSA SSI, failure to treat the carrier state before surgery results in MRSA SSI.     

A study on postoperative enteritis caused by methicillin-resistant Staphylococcus aureus

We investigated the production of staphylococcal enterotoxin (SE) with respect to coagulase types by methicillin-resistant Staphylococcus aureus (MRSA). A total of 138 strains of MRSA, which were isolated from clinical materials in the surgical ward between 1983 and 1990, were studied. Coagulase type IV strains produced SE A only, whereas coagulase type II strains were classified into four groups by SE production: SE B producing strains (32.7%), SE C producing strains (29.8%), SE B and C coproducing strains (12.5%), and SE A and C coproducing strains (25.0%). Almost all of the organisms (nine of ten) which were isolated from the feces of patients with MRSA enteritis were SE A and C coproducing strains. The coincidence in time of the prevalence of MRSA enteritis and the isolation SE A and C coproducing strains also demonstrated that these strains caused MRSA enteritis. Although SE C producing strains and SE A and C coproducing strains were simultaneously prevalent in 1990, the former tended to be sensitive while the latter tended to be resistant to minocycline. Considering the variety of antibiotic sensitivity in coagulase type II strains, it is thus considered to be of critical importance for epidemiologic purposes to further characterize isolates by SE typing.     

Clinical studies of enteritis caused by methicillin-resistant Staphylococcus aureus.

OBJECTIVE: To study the clinical features of methicillin-resistant Staphylococcus aureus (MRSA) enteritis in our surgical ward. DESIGN: Retrospective study. SETTING: Teaching hospital, Japan. SUBJECTS: 16 men and 1 woman who developed MRSA enteritis from January 1995 to October 1999. MAIN OUTCOME MEASURES: Causes and treatments. RESULTS: The underlying diseases were as follows: gastric cancer (n = 13), colorectal cancer (n = 2), recurrent cancer (n = 1) and bowel obstruction following gastrectomy (n = 1). 16 patients were operated on. Two cases were treated with histamine H2 receptor blockers. The mean age of patients was 65 years (range 50-80). In 13 cases MRSA enteritis developed within 6 days of operation. 10 strains of MRSA were isolated from stools, 8 from gastric juice, and 3 from intra-abdominal exudate. 10 patients were treated with vancomycin given through a nasogastric tube and 2 through a nasogastric tube and by drip intravenous infusion. 15 patients survived and 2 died. CONCLUSIONS: Patients who are given broad-spectrum antibiotics and whose gastric secretion is reduced are at high risk of MRSA enteritis. In the surgical ward, early diagnosis, treatment, and isolation are essential for patients with MRSA enteritis.     

In vitro infectability of prosthetic mesh by methicillin-resistant Staphylococcus aureus

Although mesh use is important for effective herniorrhaphy in adults, prosthetic infections can cause serious morbidity. Bacterial adherence to the mesh is a known precursor to prosthetic infection. We compared the ability of common mesh prosthetics to resist bacterial adherence. The meshes studied included polypropylene (Marlex^®), expanded polytetrafluoroethylene (PTFE) with and without silver chlorhexidine coating (DualMesh Plus^® and Dualmesh^®) composite meshes (Composix E/X^®, Proceed^?, and Parietex Composite^®) and lightweight polypropylene meshes (TiMesh^®, Ultrapro^®, and Vypro^®). Fifteen samples of each mesh type were individually inoculated with a suspension of 10⁸ methicillin-resistant Staphylococcus aureus (MRSA) in tryptic soy broth. After incubation at 37°C for 1 h, the mesh pieces were then removed and serially washed. The colony-forming units (CFU) of MRSA present in the initial inoculum, at the end of the 1-h warm-water bath (broth count), and the pooled washes (wash count), were determined using serial dilutions and spot plating. The bacteria not accounted for in the broth or wash counts were considered adhered to the mesh. Samples of each mesh type were also analyzed using scanning electron microscopy (SEM). Data are presented as the mean percentage adherence with ANOVA and Tukey’s test used to determine significance (P<0.05). The DualMesh Plus^® mesh had no detectable MRSA in the broth or the pooled wash samples. Dualmesh^® had less adherence compared with Marlex^®, Proceed^?, and Vypro^® (P<0.05). Conversely, Vypro^® had a statistically higher adherence (96%, P<0.05) as compared to TiMesh^®, Ultrapro^®, Composix E/X^®, and Parietex Composite^®. SEM confirmed bacterial adherence to all the mesh types except DualMesh Plus^®. The ability of a biomaterial to resist infection has an important clinical significance. DualMesh Plus^®, due to its antimicrobial coating, is the only mesh type of the nine tested that demonstrated a bactericidal property. Standard PTFE (Dualmesh^®) also had less bacterial adherence. Vypro^® demonstrated an increase in bacterial adherence; this was possibly due to the multifilament polyglactin 910 weaved within the prolene component of the mesh.     

甲氧西林耐药金黄色葡萄球菌基因分型及耐药现状研究

目的 研究烧伤病房分离的甲氧西林耐药金黄色葡萄球菌(MRSA)的葡萄球菌盒式染色体mec(SCCmec)基因分型及耐药现状. 方法 2012年9月-2013年9月,从笔者单位烧伤整形科ICU及普通病房送检的患者创面分泌物、血液及痰液标本r中,检出非重复金黄色葡萄球菌179株(ICU来源68株、普通病房来源111株).采月头孢西丁K-B纸片扩散法检测金黄色葡萄球菌MRSA表型,对ICU和普通病房中MRSA检出率进行比较.采用PCR法对MRSA进行SCCmec.分型,经检测甲氧西林耐药决定子mecA基因对前述MRSA鉴定结果进行验证 . 采用用 K-B纸片扩散法检测MRSA与甲氧西林敏感金黄色葡萄球菌(MSSA)对23种临床常用抗菌药物的耐药情况 除去MRSA对其耐药率为100.0％或0的抗菌药物,将SCCmecⅢ型MRSA与非SCCmecⅢ型MRSA 对剩余抗菌药物的耐药率进行比较对数据行Pearsonx2检验或校正x2检验. 结果 179株金黄色葡萄球菌中148株鉴定为MRSA占82.7％,其中ICU来源62株、普通病房来源86株;其余31株为MSSA占 17.3％.ICU中 MRSA在该病区内检出金黄色葡萄球菌中所占百分比为91.2％(62/68),显著高于普通病房中的77.5％(86/111),x2=5.526,P=0.019. PCR检测显示148株MRSA均携带mecA基因,其中106株为SCCmecⅢ型阳性占71.6％;ICU与普通病房中 SCCmecⅢ型MRSA占各自病区内检出MRSA的百分比分别为72.6％ (45/62)和70.9％ (61/86),差异无统计学意义(x2=0.048,P=0.826).148株MRSA对青霉素及头孢类抗生素共8种抗菌药物100.0％耐药,对万古霉素、替考拉宁、利奈唑胺、替加环素、呋喃妥因及奎奴普丁/达隔普汀的耐药率均为0除2种菌对其耐药率为0的6种抗菌药物外,MRSA对剩余17种抗菌药物的耐药率均显著高于MSSA(x2值为4.091 ～138.546,P＜0.05或P＜0.01) 106株SCCmecⅢ型MRSA对左氧氟沙星、环丙沙星、利福平、四环素、红霉素、林可霉素、庆大霉素、克林霉素的耐药率分别为56.6％(60/106)、85.8％ (91/106)、89.6％ (95/106) 、86.8％(92/106)、84.9％ (90/106)、78.3％(83/106)、92.5％ (98/106)、74.5％ (79/106),均显著高于42株非SCCmecⅢ型MRSA的33.3％ (14/42)、61.9％(26/42) 、71.4％ (30/42)、66.7％ (28/42) 、69.0％(29/42)、57.1％(24/42)、71.4％(30/42)、52.4％ (22/42),x2值为4.801 ～11.377,P＜0.05或P＜0.01. 结论 笔者单位烧伤病房的MRSA检出率高且耐药现状十分严峻,流行情况以SCCmec.Ⅲ型为主,未见对糖肽类抗生素耐药情况.     

Monomicrobial necrotizing fasciitis caused by coagulase-negative Staphylococci and methicillin-resistant Staphylococcus aureus

Background

Coagulase-negative staphylococci (CoNS) have been reported to cause necrotizing fasciitis; however, there are some difficulties in differentiating the roles of CoNS infections as contaminants or pathogenic isolates. Methicillin-resistant S. aureus (MRSA) has emerged as the most common isolate to cause necrotizing fasciitis in the past decade. This study was to compare the clinical presentation and surgical outcome of CoNS and MRSA monomicrobial necrotizing fasciitis, and to assess the prevalence of CoNS and MRSA infection in diabetic patients.

Methods

Necrotizing fasciitis caused by CoNS in 11 patients and that caused by MRSA in 27 patients was retrospectively reviewed. Demographic data, underlying diseases, laboratory results, and clinical outcome were analyzed for each patient in two groups.

Results

All patients underwent fasciotomy and received broad-spectrum antibiotic therapy. The mortality of MRSA group and CoNS group was 18.5 and 9%, respectively. Mortality, patient characteristics, clinical presentations, and laboratory data did not differ significantly between the two groups. Eight of CoNS patients (73%) and fourteen of MRSA patients (52%) had significant association with diabetes mellitus.

Conclusions

Necrotizing fasciitis caused by CoNS is a surgical emergency and should be considered to be serious as that caused by MRSA. Diabetic patients with a history of abrasion injury or chronic ulcer should be cautioned about the risk of developing CoNS and MRSA necrotizing fasciitis.     

Community-acquired methicillin-resistant Staphylococcus aureus infections in otolaryngology.

Soon after the introduction of methicillin, strains of Staphylococcus aureus resistant to methicillin were reported. Methicillin-resistant Staphylococcus aureus (MRSA) has become a common hospital pathogen, often resistant to multiple antibiotics, while causing significant morbidity and mortality. Community-acquired MRSA infections have been infrequently documented. Most reports have been associated with intravenous drug abuse. This report reviews 15 patients with community-acquired MRSA infections of the head and neck. None admitted to intravenous drug use. Additionally, no patient was known to be a healthcare worker. The MRSA strains showed antibiotic susceptibility and resistance profiles different from typical hospital-acquired MRSA isolates. All but one infection resolved with adequate surgical or appropriate antibiotic therapy. Clinicians should become aware of the possibility of community-acquired MRSA in the patient who has had continued infection despite antibiotic therapy.     

Necrotizing fasciitis caused by Staphylococcus aureus: the emergence of methicillin-resistant strains

Staphylococcus aureus is an uncommon causative agent of monomicrobial necrotizing fasciitis, but we have noted several cases over the years. The patients treated for necrotizing fasciitis between January 1998 and December 2008 in our institution were identified, and their medical records were reviewed. Of 105 necrotizing fasciitis cases during the study period, 18 were caused by monomicrobial S. aureus infection (17%). The median age was 62 years (range, 12-81 years). Among this cohort, 10 patients had coexisting medical conditions or risk factors, including diabetes and hypertension. Lower limbs and upper limbs are the most commonly involved sites. Among the bacterial isolates from these cases, 8 were methicillin-sensitive S. aureus (MSSA) and 10 were methicillin-resistant S. aureus (MRSA). One patient died in the MSSA group, and 5 patients died in the MRSA group. The mortality rate and other clinical characteristics were not significantly different between the 2 groups. However, all MRSA necrotizing fasciitis developed after the year 2000, and it was significantly different from MSSA necrotizing fasciitis that predominantly took place before the year 2000. In conclusion, S. aureus is an important pathogen of monomicrobial necrotizing fasciitis, and MRSA has emerged as the predominant causative agent in recent years. Therefore, MRSA-directed antibiotic therapy should be considered when treating patients suspected with necrotizing fasciitis in endemic areas.