The role of nasal carriage in Staphylococcus aureus infections

Staphylococcus aureus is a frequent cause of infections in both the community and hospital. Worldwide, the increasing resistance of this pathogen to various antibiotics complicates treatment of S aureus infections. Effective measures to prevent S aureus infections are therefore urgently needed. It has been shown that nasal carriers of S aureus have an increased risk of acquiring an infection with this pathogen. The nose is the main ecological niche where S aureus resides in human beings, but the determinants of the carrier state are incompletely understood. Eradication of S aureus from nasal carriers prevents infection in specific patient categories-eg, haemodialysis and general surgery patients. However, recent randomised clinical trials in orthopaedic and non-surgical patients failed to show the efficacy of eliminating S aureus from the nose to prevent subsequent infection. Thus we must elucidate the mechanisms behind S aureus nasal carriage and infection to be able to develop new preventive strategies. We present an overview of the current knowledge of the determinants (both human and bacterial) and risks of S aureus nasal carriage. Studies on the population dynamics of S aureus are also summarised.     

Mediastinitis and mycotic aneurysm of the aorta after orthotopic heart transplantation

After cardiac transplantation, bacterial mediastinitis is a rare but dangerous early complication. Of the 113 patients who underwent heart or heart-lung transplantation at our hospital from August 1981 to April 1989, 8 developed purulent mediastinitis. Treatment involved surgical débridment, local irrigation, drainage, and high-dose systemic antibiotics. No patient died of an acute mediastinal infection. In 2 cases, however, chronic mediastinitis led to the formation of a huge mycotic aneurysm of the ascending aorta. Eleven days after surgical intervention for rupture, 1 patient died of aneurysmal rerupture; the 2nd patient remains well 16 months after prosthetic replacement of the ascending aorta and reconstruction of the necrotic proximal portion of the left coronary artery with a saphenous vein patch.     

An esophageal cancer case unresectable due to tuberculous fibrosing mediastinitis: report of a case

We present a case of esophageal carcinoma in which esophagectomy was not possible because of tuberculous fibrosing mediastinitis. A 77-year-old man was diagnosed with carcinoma of the thoracic esophagus and admitted to our hospital. Chest radiography on admission revealed no abnormality except pleural thickening of the pulmonary apices, suggesting a history of subclinical infection of tuberculous pleurisy. The patient underwent surgery with a curative intent. Thoracotomy revealed that the mediastinum had been replaced with dense fibrous tissues and was widely encased with laminar calcification. Esophagectomy was not performed because it was considered impossible to do so safely. Although diagnosis of fibrous mediastinitis was not made preoperatively, review of the preoperative computed tomographic scans revealed proliferation of mediastinal soft tissues that were associated with patchy and laminar calcifications. Tuberculous fibrosing mediastinitis is an uncommon but clinically important disease for physicians who are involved in the diagnosis and treatment of esophageal cancer.     

Transmission of Staphylococcus aureus from maternity unit staff members to newborns disclosed through spa typing

BACKGROUND: We observed previously that newborn infants are colonized with Staphylococcus aureus, even if their mothers do not carry S aureus. This observation indicated a cross colonization, and, thus, a risk for nosocomial infection, although the infants are roomed in with their mothers. METHODS: The S aureus colonization of infants, their parents, and staff members was measured at 3 maternity units. Possible transmission routes were determined using spa typing of S aureus isolates. RESULTS: Infants had the highest S aureus carriage (45%) compared with fathers (39%), mothers (27%), and staff members (27%). In 13 out of 44 colonized infants, transmission from staff members was indicated. This transmission was more frequent than was transmission from their own parents (11 cases), and occurred even in cases when parents were colonized with S aureus of other spa types. CONCLUSIONS: We confirm a high level of transmission of S aureus from staff members to infants, indicating a risk for patient safety, which necessitates continuing work with implementing scientific evidence for infection control. The spa typing is a rapid and valuable epidemiological tool, and it can be used in improving hospital hygiene control programs.     

The burden of Staphylococcus aureus infections on hospitals in the United States: an analysis of the 2000 and 2001 Nationwide Inpatient Sample Database

BACKGROUND: Previous studies have investigated the impact of Staphylococcus aureus infections on individual hospitals, but to date, no study using nationally representative data has estimated this burden. METHODS: This is a retrospective analysis of the 2000 and 2001 editions of the Agency for Healthcare Research and Quality's Nationwide Inpatient Sample database, which represents a stratified 20% sample of hospitals in the United States. All inpatient discharge data from 994 hospitals in 28 states during 2000 and from 986 hospitals in 33 states during 2001, representing approximately 14 million inpatient stays, were analyzed to determine the association of S aureus infections with length of stay, total charges, and in-hospital mortality. RESULTS: Staphylococcus aureus infection was reported as a discharge diagnosis for 0.8% of all hospital inpatients, or 292 045 stays per year. Inpatients with S aureus infection had, on average, 3 times the length of hospital stay (14.3 vs 4.5 days; P<.001), 3 times the total charges (48,824 US dollars vs 14,141 US dollars; P<.001), and 5 times the risk of in-hospital death (11.2% vs 2.3%; P<.001) than inpatients without this infection. Even when controlling for hospital fixed effects and for patient differences in diagnosis-related groups, age, sex, race, and comorbidities, the differences in mean length of stay, total charges, and mortality were significantly higher for hospitalizations associated with S aureus. CONCLUSIONS: Staphylococcus aureus infections represent a considerable burden to US hospitals, particularly among high-risk patient populations. The potential benefits to hospitals in terms of reduced use of resources and costs as well as improved outcomes from preventing S aureus infections are significant.     

New trends in Staphylococcus aureus infections: glycopeptide resistance in hospital and methicillin resistance in the community

PURPOSE OF REVIEW: Methicillin-resistant Staphylococcus aureus is prevalent in hospitals throughout the world, and we have got used to its presence in daily clinical practice. However, methicillin-resistant S. aureus has not remained static over the past four decades, but seems to be evolving in unfamiliar directions. This review focuses on recent findings on two directions of methicillin-resistant S. aureus evolution: the acquisition of multiple antibiotic resistance in the hospital and the trend towards methicillin-resistant S. aureus as a community pathogen. RECENT FINDINGS: We looked at reports on glycopeptide resistance in S. aureus and those on community-acquired methicillin-resistant S. aureus strains, with some references of historical value to explain the entire picture of this 'new field' of the methicillin-resistant S. aureus problem. SUMMARY: The references given here (excluding some of low credibility) attest the increasing awareness of the two conspicuous problems concerning methicillin-resistant S. aureus infection. One is the increasing trend of glycopeptide-resistance, making difficult the successful treatment of multi-drug-resistant methicillin-resistant S. aureus infection in the hospital. On the other hand, non-multi-drug-resistant methicillin-resistant S. aureus strains are emerging as novel threats in the community, the genetic analysis of which indicates that they are independent clones from those found in hospitals.     

Mediastinitis after cardiac surgery in Madani Heart Center, Tabriz, Iran

Post-sternotomy infections are a kind of nosocomial infection involving the mediastinum space and the sternum, with a high morbidity and mortality rate. The present study was carried out to identify the incidence of mediastinitis following cardiac surgery and the most common risk factors. Cardic patients undergoing surgery were studied for suspicious mediastinitis infection at the Madani Heart Center, Tabriz, Iran from 2004 to 2006. The most common isolated agents included the coagulase-negative staphylococci, Staphylococcus aureus, Pseudomonas aeruginosa and Enterobacter spp. Incidence of postoperative mediastinitis after cardiac surgery was 1.2%. The mortality rate of postoperative mediastinitis was high (34.3%). Wound infection, especially mediastinitis following cardiac surgery, is rare but could be life-threatening. The most important step in the management of wound infections is prevention, and preventive measures could be strengthened by identifying the risk factors.     

A fatal case of acute mediastinitis caused by periodontal infection]

A 57-year-old man had suffered from poorly controlled diabetes mellitus and liver cirrhosis due to alcohol and hepatitis C for about 10 years. He developed fever and swelling of the right cheek and neck due to periodontal infection. The symptoms worsened in spite of antibiotic therapy and were accompanied by dyspnea. He was therefore referred to our hospital. Chest radiographs and computed tomographs revealed widening of the superior mediastinum, pulmonary infiltrates and right pleural effusion. He was diagnosed as having mediastinitis, right pyothorax and pneumonia caused by periodontal infection. Tracheotomy and mechanical ventilation were performed. Antibiotic therapy resulted in improvement of the mediastinitis and pyothorax. However, renal and liver dysfunction developed and the patient died of multiorgan failure after 35 days of hospitalization. Death due to periodontal infection is rare. We give a review of the literature.     

National trends in Staphylococcus aureus infection rates: impact on economic burden and mortality over a 6-year period (1998-2003).

BACKGROUND: We evaluated historical trends in the Staphylococcus aureus infection rate, economic burden, and mortality in US hospitals from 1998 through 2003. METHODS: The Nationwide Inpatient Sample was used to assess trends over time of S. aureus infection during 1998-2003. Historical trends were determined for 5 strata of hospital stays, including all inpatient stays, surgical procedure stays, invasive cardiovascular surgical stays, invasive orthopedic surgical stays, and invasive neurosurgical stays. RESULTS: During the 6-year study period from 1998 through 2003, the rate of S. aureus infection increased significantly for all inpatient stays (from 0.74% to 1.0%; annual percentage change (APC), 7.1%; P=.004), surgical stays (from 0.90% to 1.3%; APC, 7.9%; P=.001), and invasive orthopedic surgical stays (from 1.2% to 1.8%; APC, 9.3%; P<.001). For invasive neurosurgical stays, the rate of S. aureus infection did not change from 1998 to 2000 but increased at an annual rate of 11.0% from 2000 to 2003 (from 1.4% to 1.8%; P=.034). The total economic burden of S. aureus infection for hospitals also increased significantly for all stay types, with the annual percentage increase ranging from 9.2% to 17.9% (P<.05 for all). In 2003, the total economic burden of S. aureus infection was estimated to be $14.5 billion for all inpatient stays and $12.3 billion for surgical patient stays. However, there were significant decreases in the risk of S. aureus-related in-hospital mortality from 1998 to 2003 for all inpatient stays (from 7.1% to 5.6%; APC, -4.6%; P=.001) and for surgical stays (from 7.1% to 5.5%; APC, -4.6%; P=.002). CONCLUSIONS: The inpatient S. aureus infection rate and economic burden of S. aureus infections for US hospitals increased substantially from 1998 to 2003, whereas the in-hospital mortality rate decreased.     

Therapy of Staphylococcus aureus bacteremia associated with a removable focus of infection.

We did a retrospective study of Staphylococcus aureus bacteremia--from removable foci of infection--treated with short course antimicrobial therapy. Patients with S. aureus endocarditis were excluded from our study. The majority of patients had sepsis from intravascular devices. After removal of the focus of bacteremia, antibiotics were administered for a mean period of 15.2 days. There were no relapses, and no patient developed endocarditis. A 10- to 21-day antibiotic regimen can be curative in S. aureus bacteremia associated with a removable focus of infection.     

Mediastinitis complicating cardiac operations: evidence of postoperative causation

An excess rate of mediastinitis complicating cardiac operations occurred in one of two hospitals served by the same surgeons. The rates were 4% at hospital A and 0.48% at hospital B for the same period (P = .002). At hospital A five patients who underwent a thoracic reoperation experienced postoperative pneumonia or bacteremia prior to onset of mediastinitis; these infections were caused by the same bacterial species. This circumstance provided a unique opportunity for comparing infection control practices, in which one hospital served as a control for interventional changes. At hospital A regular and temporary critical care nursing personnel, who took care of both infected and uninfected patients, did not antisepticize their hands before manipulation of percutaneous catheters. After cohorts of nurses were formed and antisepsis of the hands with alcohol was strictly enforced (no diminution in the number of temporary personnel was instituted), the frequency of mediastinitis decreased significantly among patients who underwent reoperations at hospital A (P = .002), but no concurrent change was noted at hospital B. Preventable postoperative remote-site infection may lead to mediastinitis.     

Preventing Staphylococcus aureus bacteremia and sepsis in patients with Staphylococcus aureus colonization of intravascular catheters: a retrospective multicenter study and meta-analysis

Two previous studies in tertiary care hospitals identified Staphylococcus aureus colonization of intravascular (IV) catheters as a strong predictor of subsequent S. aureus bacteremia (SAB), even in the absence of clinical signs of systemic infection. Bacteremia was effectively prevented by timely antibiotic therapy. We conducted this study to corroborate the validity of these findings in non-university hospitals.Using the laboratory information management systems of the clinical microbiology departments in 6 Dutch hospitals, we identified patients who had IV catheters from which S. aureus was cultured between January 1, 2003, and December 31, 2008. Patients with demonstrated SAB between 7 days before catheter removal and 24 hours after catheter removal were excluded. We extracted clinical and demographic patient data from the patients' medical records. The primary risk factor was initiation of anti-staphylococcal antibiotic therapy within 24 hours, and the primary endpoint was SAB >24 hours after IV catheter removal. Subsequently, we performed a systematic review and meta-analysis of all observational studies evaluating the effect of antibiotic therapy for S. aureus IV catheter tip colonization.In the current study, 18 of the 192 included patients developed subsequent SAB, which was associated with not receiving antibiotic therapy within 24 hours (odds ratio [OR], 4.2; 95% confidence interval [CI], 1.1-15.6) and with documented exit-site infection (OR, 3.3; 95% CI, 1.2-9.3). When we combined these results with results of a previous study in a university hospital, a third risk factor was also associated with subsequent SAB, namely corticosteroid therapy (OR, 2.9; 95% CI, 1.3-6.3). We identified 3 other studies, in addition to the present study, in a systematic review. In the meta-analysis of these studies, antibiotic therapy yielded an absolute risk reduction of 13.6% for subsequent SAB. The number needed to treat to prevent 1 episode of SAB was 7.4.We conclude that early initiation of antibiotic therapy for IV catheters colonized with S. aureus prevents subsequent SAB.     

Recurrent prosthetic valve endocarditis caused by Staphylococcus aureus colonizing skin lesions in severe atopic dermatitis

Infective endocarditis, a serious infection most commonly affecting rheumatic or prosthetic valves, generally occurs after bacteremia. Atopic dermatitis, a very common disease, carries a high prevalence of skin infections, particularly with Staphylococcus aureus. While cutaneous colonization by S. aureus represents an important source of bacteremia, few cases of infective endocarditis arising from the skin lesions of atopic dermatitis have been reported. We describe a patient with recurrent S. aureus prosthetic valve endocarditis developing in this manner.     

Molecular differentiation of historic phage-type 80/81 and contemporary epidemic Staphylococcus aureus

Staphylococcus aureus is a bacterial pathogen known to cause infections in epidemic waves. One such epidemic was caused by a clone known as phage-type 80/81, a penicillin-resistant strain that rose to world prominence in the late 1950s. The molecular underpinnings of the phage-type 80/81 outbreak have remained unknown for decades, nor is it understood why related S. aureus clones became epidemic in hospitals in the early 1990s. To better understand the molecular basis of these epidemics, we sequenced the genomes of eight S. aureus clinical isolates representative of the phage-type 80/81 clone, the Southwest Pacific clone [a community-associated methicillin-resistant S. aureus (MRSA) clone], and contemporary S. aureus clones, all of which are genetically related and belong to the same clonal complex (CC30). Genome sequence analysis revealed that there was coincident divergence of these clones from a recent common ancestor, a finding that resolves controversy about the evolutionary history of the lineage. Notably, we identified nonsynonymous SNPs in genes encoding accessory gene regulator C (agrC) and α-hemolysin (hla)--molecules important for S. aureus virulence--that were present in virtually all contemporary CC30 hospital isolates tested. Compared with the phage-type 80/81 and Southwest Pacific clones, contemporary CC30 hospital isolates had reduced virulence in mouse infection models, the result of SNPs in agrC and hla. We conclude that agr and hla (along with penicillin resistance) were essential for world dominance of phage-type 80/81 S. aureus, whereas key SNPs in contemporary CC30 clones restrict these pathogens to hospital settings in which the host is typically compromised.     

Successful conservative therapy for mediastinitis caused by multiple esophageal perforations

A 77-year-old man was admitted to our hospital on a diagnosis of acute mediastinits, 17 days after he had high fever. Computed tomography of the chest revealed an abscess cavity in the left upper mediastinum. Endoscopic examination showed multiple pin-hole perforations in the upper esophagus from 23 to 24cm distal from the incisors and drainage through the perforation. We diagnosed acute mediastinitis caused by multiple esophageal perforations of unknown etiology. We initiated conservative therapy. Oral intake was restarted on the 17th day because radiological examination showed the esophageal perforation had closed. The patient was discharged on the 36th day from admission. Although mediastinitis caused by esophageal perforation often demands surgical treatment, conservative nonoperative therapy was successful in this patient.     

Successful salvage therapy with daptomycin after linezolid and vancomycin failure in a liver transplant recipient with methicillin-resistant Staphylococcus aureus endocarditis

Abstract: Infective endocarditis is a rare complication affecting solid organ transplant recipients. Staphylococcus aureus is a common cause of infective endocarditis accounting for about 30% of cases. We present a case of nosocomial methicillin-resistant S. aureus endocarditis with persistent bacteremia, in a patient following orthotopic liver transplantation. We were unable to eradicate this infection with primary linezolid therapy or with secondary treatment with combined vancomycin and rifampicin, but successfully treated it with daptomycin, in addition to tricuspid and aortic valve replacement.     

The changing profile of bacterial endocarditis as seen at an australian provincial centre

Background: The clinical profile of endocarditis has changed over the past four decades with studies showing trends towards increasing age, more nosocomial and prosthetic valve infection and increasing rates of Staphylococcus aureus infection. However, these studies have been biased by referral patterns. Methods: We reviewed data collected at three hospitals in the Barwon-South-West region in Victoria, Australia. All cases identified between 1994 and 1999 were reviewed according to the Duke criteria. Results: During this period, 58 patients were diagnosed as having endocarditis. The incidence rate during this time was 3.0 per 100 000 with a rise in the rate of admissions from 0.15 to 0.26 per 1000 from 1995 to 1999. Sixteen (28%) were nosocomial with the majority from line-related sepsis. No intravenous drug users were identified. Eighteen (31%) involved endovascular prosthetic material. S. aureus was the causative pathogen in 23 (40%), with 'viridans' streptococci contributing 12 (21%) and other organisms accounting for 12 (21%). Attributable mortality in this series was 17%. Conclusions: We have seen a rise in the rate of endocarditis during this time. The proportions of endocarditis due to S. aureus and 'viridans' streptococci, as well as rates of nosocomial and prosthetic valve infection, are consistent with more recent series at referral hospitals and district hospitals, representing a change since studies performed in the 1960s and 1970s. Our findings confirm a trend towards a clinical profile seen at referral centres and reinforce the emerging importance of S. aureus, nosocomial bacteraemia and prosthetic valve endocarditis.     

Methicillin-resistant staphylococci and their treatment in the intensive care unit

Methicillin resistance in Staphylococcus aureus (MRSA) and the coagulase-negative staphylococci (MRCNS) is widespread and continues to increase in prevalence, particularly in the health care setting. The clinical significance of methicillin resistance for patients with staphylococcal infections is not clear: studies in patients with bacteremia, pneumonia, and mediastinitis show a higher mortality with MRSA infection compared to methicillin-sensitive Staphylococcus aureus (MSSA) infection, though this may be due to underlying patient, pharmacodynamic, or microbiological differences. For serious methicillin-resistant staphylococcal infections, vancomycin-based regimens are preferred. Treatment alternatives for patients with severe methicillin-resistant infections who are unable to tolerate vancomycin include linezolid and quinupristin/dalfopristin; these agents should be considered second-line options, given the relative lack of clinical experience and the nonsignificant but consistent trends toward worse outcomes in bacteremia and pneumonia with these agents compared to vancomycin. For less severe infections, treatment options also include trimethoprim-sulfamethoxazole, or fluoroquinolones in combination with rifampin.     

Staphylococcus aureus meningitis: review of 28 cases

Staphylococcus aureus is a relatively uncommon cause of meningitis associated with high mortality in neonates and neurosurgical patients. The infrequency of this infection has made its study difficult and has complicated the issues of treatment and prognosis. We reviewed 28 cases of S. aureus meningitis occurring over a 10-year period at three hospitals. Eight cases in children and 20 in adults were identified. Seventy-five percent of the children and 35% of the adults had central nervous system trauma or surgery; 45% of adults had comorbid disease that might have predisposed them to infection. Clinical presentation did not distinguish this form of meningitis from other bacterial meningitides. Findings in cerebrospinal fluid were characteristic of acute bacterial meningitis. Blood cultures were positive in 65% of cases. Overall mortality was 37%; 50% of adults but no children died of meningitis. No patients with S. aureus meningitis complicating cerebrospinal fluid shunts died; however, nine of 11 patients with identifiable foci of infection outside the central nervous system died. Only one patient receiving initial treatment with a penicillinase-resistant penicillin died of meningitis, whereas six of 12 patients not so treated died.     

Sternal and costochondral infections with gentamicin and methicillin resistant Staphylococcus aureus following thoracic surgery

Six patients in a thoracic unit developed sternal osteomyelitis and costochondritis following median sternotomy. Five of the patients were operated on in another hospital. Gentamicin and methicillin resistant Staphylococcus aureus was isolated in pure culture in each case. The S. aureus isolate from 2 patients was of the same phage type suggesting cross-infection. Antibiotic prophylaxis administered in the perioperative period was ineffective. One patient, treated with amikacin (to which all of the strains were sensitive in vitro) and cefuroxime, died from overwhelming infection in spite of débridement and resuturing of the wound. The remaining 5 patients were cured with vancomycin therapy usually coupled with surgical intervention.