Pediatric pneumonia death caused by community-acquired methicillin-resistant Staphylococcus aureus, Japan

Community-Acquired Methicillin-Resistant Staphylococcus aureus in Hospitals: Age-Specificity and Potential Zoonotic-Zooanthroponotic Transmission Dynamics

Methicillin-resistant Staphylococcus aureus (MRSA) lineages are a devastating clinical and public health issue. Data on local lineage profiles are limited. We report on the frequency of community-acquired and hospital-acquired cases (CA-MRSA, HA-MRSA). We studied 147 isolates from King Khalid tertiary care hospitals (KKH), each from a case in a patient and including 33 patients at the Maternity and Children's Hospital (MCH). Of the 147 isolates, 87 males (59%) and 60 females (41%) were in KKH. The overwhelming majority (80%; n = 119/147) were CA-MRSA in KKH. Intriguingly, despite significant differences between males (70%) and females (53%), lineage-acquisition remained age-specific around 58-60 years in both genders. However, while CA-MRSA dominated early in life (0-20, 70% MCH), it increased with age in KKH adults; 21-50 (28%), >50 (59%) until the overall 80% (n = 144/180). Major specimens included skin-wounds, surgeries (70.3%), blood (13.5%), sputum (8.8%), very rarely urine (4.1%), and nasal (3.4%), albeit most patients showed severe enteritis and necrotizing pneumonia. Antibiograms showed high beta lactam resistances, including amoxicillin-clavulanate (83%), oxacillin (84%), cefoxitin FOX (100%), penicillin and ampicillin (~100%), as well as high resistance (82%) to carbapenem. Fortunately, high susceptibility was seen to non-beta lactams and, to a lesser extent, gentamicin, erythromycin, and fusidic acid; 33%, 34%, and 38%, respectively, in KKH. A similar pattern was seen in MCH except for a low resistance pattern to gentamicin CN, clindamycin CD, erythromycin E, and tobramycin TOB; 34%, 31%, 39%, and 41%, respectively, except for fusidic acid. These findings have significant clinical implications for MRSA patient management strategies. Clinical- and lineage-profiles imply host-selection and zoonotic-zooanthroponotic transmission dynamics. Future molecular typing, sequencing, and characterization of dominant clone(s) is imperative.

Methicillin-Resistant Staphylococcus aureus: Molecular Characterization, Evolution, and Epidemiology

Staphylococcus aureus, a major human pathogen, has a collection of virulence factors and the ability to acquire resistance to most antibiotics. This ability is further augmented by constant emergence of new clones, making S. aureus a "superbug." Clinical use of methicillin has led to the appearance of methicillin-resistant S. aureus (MRSA). The past few decades have witnessed the existence of new MRSA clones. Unlike traditional MRSA residing in hospitals, the new clones can invade community settings and infect people without predisposing risk factors. This evolution continues with the buildup of the MRSA reservoir in companion and food animals. This review focuses on imparting a better understanding of MRSA evolution and its molecular characterization and epidemiology. We first describe the origin of MRSA, with emphasis on the diverse nature of staphylococcal cassette chromosome mec (SCCmec). mecA and its new homologues (mecB, mecC, and mecD), SCCmec types (13 SCCmec types have been discovered to date), and their classification criteria are discussed. The review then describes various typing methods applied to study the molecular epidemiology and evolutionary nature of MRSA. Starting with the historical methods and continuing to the advanced whole-genome approaches, typing of collections of MRSA has shed light on the origin, spread, and evolutionary pathways of MRSA clones.

Community-Acquired Pneumonia in the Asia-Pacific Region

Community-acquired pneumonia (CAP) is an important cause of mortality and morbidity worldwide. Aging population, dense urbanization, and poor access to health care make the Asia-Pacific region vulnerable to CAP. The high incidence of CAP poses a significant health and economic burden in this region. Common etiologic agents in other global regions including Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, Chlamydophila pneumoniae, Staphylococcus aureus, and respiratory viruses are also the most prevalent pathogens in the Asia-Pacific region. But the higher incidence of Klebsiella pneumoniae and the presence of Burkholderia pseudomallei are unique to the region. The high prevalence of antimicrobial resistance in S. pneumoniae and M. pneumoniae has been raising the need for more prudent use of antibiotics. Emergence and spread of community-acquired methicillin-resistant S. aureus deserve attention, while the risk has not reached significant level yet in cases of CAP. Given a clinical and socioeconomic importance of CAP, further effort to better understand the epidemiology and impact of CAP is warranted in the Asia-Pacific region.

Emerging ST121/agr4 community-associated methicillin-resistant Staphylococcus aureus (MRSA) with strong adhesin and cytolytic activities: trigger for MRSA pneumonia and fatal aspiration pneumonia in an influenza-infected elderly

The pathogenesis of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) pneumonia in influenza-infected elderly individuals has not yet been elucidated in detail. In the present study, a 92-year-old man infected with influenza developed CA-MRSA pneumonia. His CA-MRSA was an emerging type, originated in ST121/agr4 S. aureus, with diversities of Panton–Valentine leucocidin (PVL)⁻/spat5110/SCCmecV⁺ versus PVL⁺/spat159^(etc.)/SCCmec⁻, but with common virulence potentials of strong adhesin and cytolytic activities. Resistance to erythromycin/clindamycin (inducible-type) and gentamicin was detected. Pneumonia improved with the administration of levofloxacin, but with the subsequent development of fatal aspiration pneumonia. Hence, characteristic CA-MRSA with strong adhesin and cytolytic activities triggered influenza-related sequential complications.

Invasive Community-Acquired Methicillin-Resistant Staphylococcus aureus in a Japanese Girl with Disseminating Multiple Organ Infection: A Case Report and Review of Japanese Pediatric Cases

Pediatric invasive community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection is very serious and occasionally fatal. This infectious disease is still a relatively rare and unfamiliar infectious disease in Japan. We report a positive outcome in a 23-month-old Japanese girl with meningitis, osteomyelitis, fasciitis, necrotizing pneumonia, urinary tract infection, and bacteremia due to CA-MRSA treated with linezolid. PCR testing of the CA-MRSA strain was positive for PVL and staphylococcal enterotoxin b and negative for ACME. SCC mec was type IVa. This case underscores the selection of effective combinations of antimicrobial agents for its treatment. We need to be aware of invasive CA-MRSA infection, which rapidly progresses with a serious clinical course, because the incidence of the disease may be increasing in Japan.

Molecular epidemiology of community-associated meticillin-resistant Staphylococcus aureus in Asia

In Asia, most reports on the epidemiology of community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) are from developed countries, with few data from resource-limited countries, not because of low actual prevalence, but probably because of scarce diagnostic facilities. The rate of MRSA in all community-associated S. aureus infections in Asian countries ranges from 2·5% to 39%. Unlike the predominance of USA300-sequence type (ST) 8 staphylococcal cassette chromosome mec (SCCmec) type IV in the USA, the molecular epidemiology of CA-MRSA in Asia is characterised by clonal heterogeneity, similar to that in Europe. The emergence of CA-MRSA is a threat in both community and hospital settings because such strains are now more prevalent than are health-care-associated MRSA (HA-MRSA) strains. Many epidemic clones are in circulation in Asia and with scarce data available, concern has arisen that CA-MRSA could have devastating results if it becomes epidemic in resource-poor regions. The epidemiology of CA-MRSA in Asia is closely linked with the health of both developing and developed countries. The present situation of CA-MRSA in Asia is important not only for local public health, but also to provide a better understanding of the successful epidemic clones of this global pathogen.

Necrotizing pneumonia in the community

A 62-year-old man presented with general fatigue. He was diagnosed with septic shock and severe pneumonia. The sputum at admission yielded methicillin-sensitive Staphylococcus aureus (MSSA) strain and methicillin-resistant S. aureus (MRSA) strain. Despite antibiotic treatment, he did not improve. A chest computed tomography (CT) revealed multilobar cavity lesions. Only MRSA strain was confirmed at that time. We diagnosed him with necrotizing pneumonia. Despite treatment with vancomycin, his pneumonia worsened and he died. At autopsy, many gram-positive cocci were observed in the lungs. The clinical presentation of our patient was different from typical CA-MRSA-mediated necrotizing pneumonia.

Community-acquired methicillin-resistant Staphylococcus aureus: community transmission, pathogenesis, and drug resistance

Methicillin-resistant Staphylococcus aureus (MRSA) is able to persist not only in hospitals (with a high level of antimicrobial agent use) but also in the community (with a low level of antimicrobial agent use). The former is called hospital-acquired MRSA (HA-MRSA) and the latter community-acquired MRSA (CA-MRSA). It is believed MRSA clones are generated from S. aureus through insertion of the staphylococcal cassette chromosome mec (SCCmec), and outbreaks occur as they spread. Several worldwide and regional clones have been identified, and their epidemiological, clinical, and genetic characteristics have been described. CA-MRSA is likely able to survive in the community because of suitable SCCmec types (type IV or V), a clone-specific colonization/infection nature, toxin profiles (including Pantone-Valentine leucocidin, PVL), and narrow drug resistance patterns. CA-MRSA infections are generally seen in healthy children or young athletes, with unexpected cases of diseases, and also in elderly inpatients, occasionally surprising clinicians used to HA-MRSA infections. CA-MRSA spreads within families and close-contact groups or even through public transport, demonstrating transmission cores. Re-infection (including multifocal infection) frequently occurs, if the cores are not sought out and properly eradicated. Recently, attention has been given to CA-MRSA (USA300), which originated in the US, and is growing as HA-MRSA and also as a worldwide clone. CA-MRSA infection in influenza season has increasingly been noted as well. MRSA is also found in farm and companion animals, and has occasionally transferred to humans. As such, the epidemiological, clinical, and genetic behavior of CA-MRSA, a growing threat, is focused on in this study.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

Estimating influenza-associated deaths in the United States

Most estimates of US deaths associated with influenza circulation have been similar despite the use of different approaches. However, a recently published estimate suggested that previous estimates substantially overestimated deaths associated with influenza, and concluded that substantial numbers of deaths during a future pandemic could be prevented because of improvements in medical care. We reviewed the data sources and methods used to estimate influenza-associated deaths. We suggest that discrepancies between the recent estimate and previous estimates of the number of influenza-associated deaths are attributable primarily to the use of different outcomes and methods. We also believe that secondary bacterial infections will likely result in substantial morbidity and mortality during a future influenza pandemic, despite medical progress.

Emergence of the community-acquired methicillin-resistant Staphylococcus aureus USA300 clone in Japan

We isolated methicillin-resistant Staphylococcus aureus (MRSA) from a 3-month-old Indian girl who was born in the United States, moved to Japan, and suffered from subcutaneous abscesses in 2007. The MRSA (strain NN36) belonged to multilocus sequence type (ST) 8, exhibited agr1, staphylococcal cassette chromosome mec (SCCmec) type IVa, and coagulase type III, and was positive for Panton-Valentine leukocidin (PVL) and the arginine catabolic mobile element (ACME), just like the USA300 clone, which is the predominant community-acquired MRSA (CA-MRSA) in the United States. Strain NN36 shared an identical pulsed-field gel electrophoresis (PFGE) pattern with the USA300 clone. Although the USA300 clone is of spa1, strain NN36 possessed spa985. Strain NN36 was resistant to erythromycin and kanamycin, in addition to beta-lactam agents (e.g., oxacillin). The data suggest that the USA300 clone has emerged in Japan. Because the USA300 clone has recently spread to European countries, surveillance of the USA300 clone should be actively performed in Japan.