Increasing clindamycin resistance among methicillin-resistant Staphylococcus aureus in 57 northeast United States military treatment facilities

Antimicrobial Resistance Patterns of Outpatient Staphylococcus aureus Isolates

Importance

Oral non-β-lactam antibiotics are commonly used for empirical therapy of Staphylococcus aureus infections, especially in outpatient settings. However, little is known about potential geographic heterogeneity and temporal trends in the prevalence of S aureus resistance to non-β-lactams in the US.

Objective

To characterize the spatiotemporal trends of resistance to non-β-lactam antibiotics among community-onset S aureus infections, including regional variation in resistance rates and geographical heterogeneity in multidrug resistance.

Design, Setting, and Participants

This cross-sectional study used data from Veterans Health Administration clinics collected from adult outpatients with S aureus infection in the conterminous 48 states and Washington, DC, from January 1, 2010, to December 31, 2019. Data were analyzed from January to November 2023.

Exposures

Resistance to lincosamides (clindamycin), tetracyclines, sulfonamides (trimethoprim-sulfamethoxazole [TMP-SMX]), and macrolides.

Main Outcomes and Measures

Spatiotemporal variation of S aureus resistance to these 4 classes of non-β-lactam antibiotics, stratified by methicillin-resistant S aureus (MRSA) and methicillin-sensitive S aureus (MSSA), and subdivided by regions of the US (Northeast, Midwest, South, and West). Trend tests and bivariate mapping were used to determine significant changes in resistant proportions over time and identify counties where rates of resistance to multiple non-β-lactams were high.

Results

A total of 382 149 S aureus isolates from 268 214 unique outpatients (mean [SD] age, 63.4 [14.8] years; 252 910 males [94.29%]) were analyzed. There was a decrease in the proportion of MRSA nationwide, from 53.6% in 2010 to 38.8% in 2019. Among MRSA isolates, we observed a significant increase in tetracycline resistance (from 3.6% in 2010 to 12.8% in 2019; P for trend < .001) and TMP-SMX resistance (from 2.6% in 2010 to 9.2% in 2019; P for trend < .001), modest and not significant increases in clindamycin resistance (from 24.2% in 2010 to 30.6% in 2019; P for trend = .34), and a significant decrease in macrolide resistance (from 73.5% in 2010 to 60.2% in 2019; P for trend < .001). Among MSSA isolates, significant upward trends in clindamycin, tetracyclines, and TMP-SMX resistance were observed. For example, tetracycline resistance increased from 3.7% in 2010 to 9.1% in 2019 (P for trend < .001). Regional stratification over time showed that the Northeast had slightly higher rates of clindamycin resistance but lower rates of tetracycline resistance, while the South had notably higher rates of resistance to tetracyclines and TMP-SMX, particularly among MRSA isolates. Bivariate mapping at the county scale did not indicate clear regional patterns of shared high levels of resistance to the 4 classes of antimicrobials studied.

Conclusions and Relevance

In this study of outpatient S aureus isolates, MRSA became less common over the 10-year period, and MRSA isolates were increasingly resistant to tetracyclines and TMP-SMX. Geographic analysis indicated no spatial overlap in counties with high rates of resistance to both tetracyclines and TMP-SMX. Examining the regional spatial variation of antibiotic resistance can inform empirical therapy recommendations and help to understand the evolution of S aureus antibiotic resistance mechanisms.

Rising incidence of severe maxillofacial space infections in Germany

OBJECTIVES

Severe maxillofacial space infection (MSI) as an end stage of dentoalveolar diseases or complication of sialadenitis is a potentially life-threatening disease accompanied by complications including airway obstruction, jugular vein thrombosis, descending mediastinitis, sepsis and acute respiratory distress syndrome. The aim of this study was to analyze the incidence and time trends of severe MSI and potentially influencing factors in the German healthcare system over time.

MATERIALS AND METHODS

Nationwide data regarding the national diagnosis-related-group (DRG) inpatient billing system was received from the German Federal Statistical Office. A retrospective analysis of incidence and time trends of MSI-associated procedures classified with the Operation and Procedure Classification System (OPS), were statistically evaluated using Poisson regression analysis between 2005 and 2022 and were associated with different epidemiological factors.

RESULTS

The total standardized incidence rate of MSI-associated procedures in the observational period 2005-2022 was 9.8 (♀8.2; ♂11.4) per 100,000 person years. For all age groups a significant increase of 46.1% in severe MSI - related surgical interventions was registered within the observational period. The largest increase (120.5%) was found in elderly patients over 80 years. There were significant differences of the incidences of MSI-associated surgeries between the different federal states in Germany.

CONCLUSIONS

Severe MSI are a growing challenge in German health care especially among elderly patients over 80 years.

CLINICAL RELEVANCE

Severe MSI is a promising target for prevention. There should be more focus in primary dental and medical care especially in groups depending on social support.

Characterization of compound A, a novel lincomycin derivative active against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of causative bacteria for hospital- and community-acquired infections. In order to overcome MRSA infection, we synthesized compound A, a lincomycin derivative, and evaluated the biological properties. The MIC₅₀ and MIC₉₀ values of compound A against MRSA clinical isolates, which were susceptible to clindamycin, from infected skin in Japan were 0.12 and 0.25 μg ml^-1, respectively, and those against hospital-acquired MRSA with clindamycin resistance were 1.0 and 2.0 μg ml^-1, respectively. Linezolid non-susceptible MRSA selected in the laboratory had mutations in the 23S rRNA gene and exhibited cross-resistance to compound A. MRSA non-susceptible to compound A selected in laboratory was not cross-resistant to linezolid, implying that the binding site to 23S rRNA partly overlaps with clindamycin and linezolid. The in vivo efficacies of compound A against mouse skin abscess model infected with clindamycin-susceptible and -resistant MRSA were superior to those of clindamycin and linezolid, respectively. The well-known linezolid-induced myelosuppression is caused by its inhibitory effect on mitochondrial function, but inhibition was weaker for compound A than that of linezolid. In short, compound A has broader anti-MRSA activities than clindamycin and linezolid due to additional binding site, and demonstrated preferable safety profile as a potential anti-MRSA drug.

S. aureus Infections in Chicago, 2006-2014: Increase in CA MSSA and Decrease in MRSA Incidence

OBJECTIVE To examine trends in Staphylococcus aureus infections in adults and children at a single academic center in 2006-2014. DESIGN Retrospective cohort study. SETTING Inpatient, outpatient, and emergency department settings in a private, tertiary referral center. PATIENTS Patients with an infection culture that grew S. aureus in January 1, 2006, through March 31, 2014. METHODS The first isolate per year for each patient was classified as community-associated (CA-), healthcare-associated (HA-), or HA-community-onset S. aureus. The incidence density of S. aureus, methicillin-susceptible S. aureus (MSSA), and methicillin-resistant S. aureus (MRSA) infections were calculated per quarter year. RESULTS Overall, 5,491 MRSA and 5,398 MSSA isolates were included. MRSA infections decreased by an average of 5.2% annually (P<.001). MRSA skin and soft-tissue infection (SSTI) incidence density decreased in adults (-3.5%; P<.001) and children (-2.9%; P=.004). MSSA infections at all anatomic sites increased by an average of 1.9% annually (P=.007) in adults and decreased 5.1% annually (P<.001) in children. MSSA SSTI incidence density increased in adults (+3.8%; P<.001) and children (+5.6%; P<.001). For MRSA and MSSA SSTI isolates, susceptibility to tetracycline and clindamycin decreased significantly. CONCLUSIONS In 2006-2014, MRSA SSTI incidence decreased among children and adults. MSSA SSTI incidence density increased in children and adults, suggesting that current empiric SSTI treatment recommendations may not be optimal. Adults experienced an overall increase in MSSA infections, which may prompt consideration of the need for horizontal infection control practices to decrease MSSA infection risk. Infect Control Hosp Epidemiol 2017;38:1226-1234.

Pharmacokinetic drug evaluation of tedizolid for the treatment of skin infections

INTRODUCTION

Tedizolid is indicated for the treatment of acute bacterial skin and skin structure infections (ABSSSI). Although tedizolid shares many similar properties with linezolid, another oxazolidinone used to treat ABSSSI, the two antibiotics have several key differences. Areas covered: This review provides a detailed summary of the overall pharmacodynamics, pharmacokinetics, clinical efficacy, and safety of tedizolid for the treatment of ABSSSI. Expert opinion: Compared to other antibiotics used for ABSSSI, tedizolid has several advantages. Tedizolid has a long half-life, allowing for once daily dosing. Tedizolid also has broad spectrum of activity against Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus, Coagulase-negative Staphylococci, and Enterococci - including isolates demonstrating resistance to linezolid. It is available in both oral and intravenous formulations, and, has outstanding oral bioavailability, allowing for oral-step down therapy. There is also some evidence that, tedizolid has fewer significant interactions with serotonin reuptake inhibitors or monoamine oxidase inhibitors than linezolid. Finally, thrombocytopenia may occur less often with tedizolid than linezolid. However, these benefits must be weighed against the financial cost of tedizolid and the availability of alternative antibiotic choices.

Integrating a Rapid Diagnostic Test and Antimicrobial Stewardship: Optimizing Discharge Antibiotics in Skin and Soft Tissue Infections

A rapid test to detect methicillin resistance in Staphylococcus aureus through the penicillin-binding protein 2a antigen was introduced for pediatric patients hospitalized for purulent skin and soft tissue infections. Integration of this test with physician education and stewardship guidance improved targeted antibiotic use for infections caused by methicillin-susceptible S. aureus (44%-80%, P < 0.001), including when final culture results were not available.

Changing Susceptibility of Staphylococcus aureus in a US Pediatric Population

BACKGROUND

Staphylococcus aureus is a major cause of infection in both adult and pediatric populations. After several decades of increasing prevalence, the proportion of S aureus infections due to methicillin-resistant S aureus has been reported to be in decline in adults. Data for similar changes in pediatric populations are limited.

METHODS

Evaluation of S aureus susceptibility data for pediatric patients receiving care in the US Military Health System was performed. Microbiology and demographic data were collected for years 2005 through 2014. Trends in antibiotic susceptibility results were evaluated. Clinical and demographic characteristics were explored to assess for association with antibiotic susceptibilities.

RESULTS

In this study, 41 745 S aureus isolates from 39 207 pediatric patients were included. An overall increase in susceptibility of isolates to oxacillin was noted over this 10-year period; with over 60% of isolates oxacillin-susceptible in 2014. S aureus susceptibility to clindamycin declined over the study period; notably methicillin-susceptible S aureus susceptibility to clindamycin declined from 90% to 83% (P < .0001). Differences in oxacillin susceptibility between US regions decreased over time.

CONCLUSIONS

Similar to recent trends seen in adults, the proportion of pediatric S aureus infections secondary to methicillin-resistant S aureus appear to be decreasing, as is variability in US geographical resistance rates. Increasing clindamycin resistance among methicillin-susceptible S aureus should raise caution in the use of empirical clindamycin in presumed S aureus infection. Clinicians should be aware of regional susceptibility patterns when choosing empirical regimens.

New developments in the management of severe skin and deep skin structure infections - focus on tedizolid

Tedizolid, a novel oxazolidinone, is approved for treatment of acute bacterial skin and skin structure infections (ABSSSIs). Tedizolid offers several potential advantages over current ABSSSI treatment options. First, tedizolid has a prolonged half-life, which allows for once-daily dosing. Second, tedizolid has broad spectrum activity against Gram-positive organisms including methicillin-resistant Staphylococcus aureus, coagulase-negative staphylococci, and enterococci. Third, tedizolid, available in both intravenous and oral formulations, has high oral bioavailability, allowing for easy oral step-down therapy. Fourth, in patients who have been prescribed selective serotonin reuptake inhibitors or monoamine oxidase inhibitors, tedizolid may have fewer drug interactions than linezolid. Finally, tedizolid may have fewer or comparatively delayed onset side effects than linezolid, including thrombocytopenia and nausea. This review covers the microbiology, pharmacology, mode of action, and pharmacokinetics of tedizolid as well as patient-focused perspectives such as quality of life, patient satisfaction/acceptability, adherence, and uptake and provides expert opinion on the current use of tedizolid for ABSSSIs and potential future therapeutic applications.

Methicillin-resistant staphylococcus aureus bone and joint infections in children

Methicillin-resistant Staphylococcus aureus has been a clinically significant pathogen in orthopaedics for more than a decade. Research shows that these infections are more virulent and that treatment requires greater use of hospital resources. A multidisciplinary approach involving emergency department physicians, radiologists, interventional radiologists, MRI technicians, pediatricians, infectious disease specialists, anesthesiologists, and orthopaedic surgeons is necessary to optimize outcomes and minimize costs. Early use of MRI helps delineate the extent of infection, aids in the consideration of surgery, and provides valuable information for surgical planning. Healthcare providers need to stay vigilant during the course of the disease to detect other sites of infection or complications of methicillin-resistant S aureus, such as deep vein thrombosis and septic pulmonary emboli. Patients with infections near growth centers require long-term monitoring to ensure the absence of growth disturbances. Physicians should help educate patients and families on prevention strategies and be aware of guidelines for students to return to school and athletes to return to play.

Feasibility of rapid polymerase chain reaction for detection of methicillin-resistant Staphylococcus aureus colonization among emergency department patients with abscesses

Purpose

In the era of community-associated methicillin-resistant Staphylococcus aureus (MRSA), clinicians face a difficult challenge when selecting antibiotics to treat abscesses. The lack of rapid diagnostics capable of identifying the causative organism often results in suboptimal antibiotic stewardship practices. Although not fully elucidated, the association between MRSA colonization and subsequent infection represents an opportunity to enhance antibiotic selectivity. Our primary objective was to examine the feasibility of utilizing a rapid polymerase chain reaction (PCR) system (Cepheid’s GeneXpert^®) to detect MRSA colonization prior to patient discharge in the emergency department (ED).

Methods

This feasibility study was conducted at a tertiary care, urban, academic ED. Patients presenting with a chief complaint related to a potential abscess during daytime hours over an 18-week period were screened for eligibility. Subjects were enrolled into either the PCR swab protocol group (two-thirds) or traditional care group (one-third). PCR swabs were obtained from known MRSA carriage sites (nasal, pharyngeal) and the superficial aspect of the wound.

Results

The two groups were similar in terms of demographics, abscess location, and MRSA history. The PCR results were available prior to patient discharge in 100% of cases. The turnaround times in minutes for the PCR swabs were as follows: nasal 73 ± 7, pharyngeal 82 ± 14, and superficial wound 79 ± 17. No significant difference in length of stay was observed between the two groups. The observed ideal antibiotic selection rates improved by 45% in the PCR group, but this trend was not significant (P = 0.08).

Conclusion

When collected in triage, PCR swabs demonstrated turnaround times that were effective for use in the ED setting. Utilizing a rapid PCR MRSA colonization detection assay for ED patients with abscesses did not adversely impact the length of stay. Real-time determination of MRSA colonization may represent an opportunity to improve antibiotic selectivity in the treatment of abscesses.

Enlarged neck lymph nodes in children

Pediatric cervical lymphadenopathy is a challenging medical condition for the patient, family, and physician. There are a wide variety of causes for cervical lymphadenopathy and an understanding of these causes is paramount in determining the most appropriate workup and management. A thorough history and physical examination are important in narrowing the differential diagnosis. Diagnostic studies and imaging studies play an important role as well. This article reviews the common causes of lymphadenopathy, and presents a methodical approach to a patient with cervical lymphadenopathy.

Improved understanding of factors driving methicillin-resistant Staphylococcus aureus epidemic waves

Methicillin-resistant Staphylococcus aureus (MRSA) remains one of the most important causes of nosocomial infections worldwide. Since the global spread of MRSA in the 1960s, MRSA strains have evolved with increased pathogenic potential. Notably, some strains are now capable of causing persistent infections not only in hospitalized patients but also in healthy individuals in the community. Furthermore, MRSA is increasingly associated with infections among livestock-associated workers, primarily because of transmission from animals to humans. Moreover, many MRSA strains have gained resistance to most available antibiotics. In this review, we will present current knowledge on MRSA epidemiology and discuss new endeavors being undertaken to understand better the molecular and epidemiological underpinnings of MRSA outbreaks.

Preadmission screening of adults highlights previously unrecognized carriage of Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus in London: a cause for concern?

In the first study of its kind in the United Kingdom, we describe the colonization rate of ciprofloxacin-sensitive Panton-Valentine leukocidin-positive methicillin-resistant Staphylococcus aureus (PVL-MRSA) in adult patients who were screened systematically at the time of hospital admission. We also describe the molecular characteristics of PVL-MRSA and antibiotic resistance phenotypes. A total of 55,760 specimens were screened for MRSA between April 2008 and December 2010. MRSA was identified in 1,998 specimens, and ciprofloxacin-susceptible (CSMRSA) isolates (385/1,998, or 19.3%) were subjected to PVL testing. Of these, 70 (18.1%) were identified as PVL-CSMRSA. During the study period, the MRSA colonization rate decreased from 4.6% to 2.8%. In contrast, the colonization rate of PVL-CSMRSA increased over time, rising from 0.075% in 2008 and 0.07% in 2009 to 0.22% in 2010. The mean patient age was 52 years (range, 18 to 90 years); over two-thirds were male. Seven different lineages of PVL-CSMRSA were identified. Over the 3 years, the Southwest Pacific clone (CC30) was dominant in our population. The CC5 clone was detected once in 2008 and not at all in 2009 but accounted for a third of all PVL-CSMRSA strains in 2010. This lineage was commonly associated with clindamycin resistance and, less frequently, tetracycline resistance. We conclude that there is hitherto unrecognized low-level carriage of PVL-CSMRSA among patients being admitted to hospitals in northwest London. We observed the emergence of the CC5 clone in 2010 with associated clindamycin and tetracycline resistance.

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) skin infections

PURPOSE OF REVIEW

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has become increasingly important as a cause of skin and soft tissue infections (SSTIs), particularly abscesses, in patients seen in the emergency department setting. The antibiotic sensitivity profile of Staphylococcus aureus isolates from SSTIs has changed over time in many geographic locations. Whether antibiotics are needed in the management of skin abscesses, and, if so, when, is controversial.

RECENT FINDINGS

A number of studies have looked at antibiotic therapy in conjunction with incision and drainage in managing abscesses. Factors evaluated were resolution of infection, need for change in antibiotic therapy, hospitalization after initial outpatient management, need for an additional drainage procedure, and recurrence of infection within 30 days after the initial incision and drainage procedure. For abscesses, clinical failure was associated with lack of adequate incision and drainage and not antibiotic use, regardless of the size of the abscess or the choice of antibiotic therapy. For other soft tissue infections, when antibiotic susceptibility data were available for the infection (impetigo or cellulitis with purulent drainage but no abscess), there was no difference in clinical resolution of MRSA infection even if the infecting organism was resistant to the antibiotic chosen for therapy.

SUMMARY

CA-MRSA has become an important cause of SSTIs. Current data suggest that most abscesses can be treated successfully with incision and drainage alone. Antibiotic choice is more crucial for management of cellulitis and should be guided by the prevalence of CA-MRSA in the community and its antibiotic susceptibility profile.

Community-associated meticillin-resistant Staphylococcus aureus

Meticillin-resistant Staphylococcus aureus (MRSA) is endemic in hospitals worldwide, and causes substantial morbidity and mortality. Health-care-associated MRSA infections arise in individuals with predisposing risk factors, such as surgery or presence of an indwelling medical device. By contrast, many community-associated MRSA (CA-MRSA) infections arise in otherwise healthy individuals who do not have such risk factors. Additionally, CA-MRSA infections are epidemic in some countries. These features suggest that CA-MRSA strains are more virulent and transmissible than are traditional hospital-associated MRSA strains. The restricted treatment options for CA-MRSA infections compound the effect of enhanced virulence and transmission. Although progress has been made towards understanding emergence of CA-MRSA, virulence, and treatment of infections, our knowledge remains incomplete. Here we review the most up-to-date knowledge and provide a perspective for the future prophylaxis or new treatments for CA-MRSA infections.

Staphylococcus aureus osteomyelitis in Hawaii

BACKGROUND

The clinical and laboratory findings and outcomes of methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) Staphylococcus aureus osteomyelitis have not been studied in Hawaii.

METHODS

Retrospective inpatient chart reviews of 62 culture-proven osteomyelitis patients between 1996 and 2007 were performed.

RESULTS

Fifteen patients (24%) had MRSA infection, and 47 patients (76%) had MSSA infection. Length of stay, chronic health problems, total duration of fever, and length of treatment were not significantly different between MRSA- and MSSA-infected patients. The peak erythrocyte sedimentation rate and C-reactive protein values were higher among MRSA infected patients (P values: .009 and .003, respectively).The systemic complication rate was higher in MRSA-infected patients (P value: .018).

CONCLUSIONS

Differing from other pediatric staphylococcal infections in Hawaii, the majority of the patients had MSSA infection. Pacific Islander and Native Hawaiian ethnicities were affected disproportionately and had MRSA infection more frequently. MRSA-infected patients had frequent surgical procedures and systemic complications.

Community-associated methicillin-resistant Staphylococcus aureus infections at an Army training installation

To assess the burden of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in a high-risk population, the monthly incidence of laboratory-confirmed MRSA in service members/trainees stationed at Fort Benning, Georgia, USA without hospitalization or surgery documented 30 days prior to infection was calculated for calendar years 2002–2007. Clinical management and antibiotic susceptibility patterns were also evaluated. By 2007, ~67% of S. aureus strains were MRSA, and ~82% of these were community-associated, primarily in trainees. In total, 3531 CA-MRSA infections were identified. Rates appeared to be seasonal, peaking at 42 cases/1000 soldiers in 2005, with rates remaining above 35/1000 soldiers thereafter. Increased prescription of effective antibiotics was documented. Susceptibility to clindamycin, ciprofloxacin, and levofloxacin decreased from 2002 to 2007 by 6%, 17%, and 14%, respectively. The sustained high prevalence of CA-MRSA observed highlights the need for more vigilant population-based counter-measures at military training installations.

Trimethoprim-sulfamethoxazole for methicillin-resistant Staphylococcus aureus: a forgotten alternative?

Methicillin-resistant Staphylococcus aureus (MRSA) is a growing infectious concern, mainly in the context of its rapid adaptation to novel antibiotic options for its treatment and the growing morbidity, mortality, and healthcare costs associated with its emergence. the authors sought to investigate whether an older antibiotic, such as trimethoprim-sulfamethoxazole (SXT), may have a role in treating MRSA-related infections, according to the available literature on the subject. The authors reviewed literature data on: resistance of MRSA to SXT worldwide in recent years, efficacy of SXT for MRSA decolonization or prophylaxis from MRSA infections, and clinical therapeutic efficacy of SXT in treating mild or severe community-acquired or hospital-acquired MRSA infections. Resistance varies worldwide, in general being low in the industrialized world and higher in developing countries. SXT is one of the numerous understudied options for MRSA decolonization and is growingly recognized as potentially effective in preventing MRSA infections in certain settings. Limited data on its therapeutic efficacy are encouraging, at least for mild, community-acquired infections. SXT may represent a cost-effective alternative weapon against MRSA. Its utility against this increasingly threatening pathogen need clarification through further clinical trials.

MRSA breast abscesses in postpartum women

BACKGROUND

Infections caused by community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) are being increasingly observed in patients who lack traditional risk factors. While mastitis and breast abscesses are commonly encountered in post-natal women, CA-MRSA breast infections have rarely been reported.

MATERIALS AND METHODS

We reviewed 15 postpartum women with methicillin-resistant Staphylococcus aureus (MRSA) breast abscesses observed in our unit from June 2005 to April 2007. Ultrasonographic examination was performed in all cases. MRSA infection was diagnosed on microbiological analysis cultured from the abscesses of these patients.

RESULTS

The median age of the patients was 31.5 years. The majority of the patients were primiparae (80%). Only one patient was immunocompromised. None of the patients had history of previous breast infection and none developed recurrence. Eleven patients (73.3%) underwent aspiration of pus and four patients (26.7%) underwent incision and drainage. All the cultures were sensitive to co-trimoxazole and vancomycin. Eight (53.3%) of the cultures were also sensitive to erythromycin.

CONCLUSION

CA-MRSA is an emerging problem in our obstetric population. CA-MRSA breast infections are clinically responsive to common oral antibiotics such as co-trimoxazole and erythromycin. A high index of suspicion is essential to avoid delay in the clinical response to empirical beta-lactams as these patients may benefit from an early change of antibiotics.

Changing trends in acute osteomyelitis in children: impact of methicillin-resistant Staphylococcus aureus infections

BACKGROUND

Staphylococcus aureus remains the most common etiologic agent of acute osteomyelitis in children. Recently, methicillin-resistant S. aureus (MRSA) has emerged as a major pathogen.

METHODS

Records of all children admitted with acute osteomyelitis from January 1999 to December 2003 were reviewed. For the comparative analysis, the study population was evenly distributed in 2 periods: period A, January 1999 to June 2001; n = 113; and period B, July 2001 to December 2003; n = 177. In addition, clinical findings of MRSA osteomyelitis were compared with non-MRSA osteomyelitis, including methicillin-sensitive S. aureus infections.

RESULTS

Two hundred ninety children (60% male subjects) with acute osteomyelitis were identified. Median (25th-75th percentile) age at diagnosis was 6 years (range, 2-11 years). Significant clinical findings included the following: localized pain (84%), fever (67%), and swelling (62%). Affected bones included the following: foot (23%), femur (20%), tibia (16%), and pelvis (7%). Thirty-seven percent of blood cultures were positive, and a bacterial isolate was obtained in 55% of cases. Bacteria most frequently isolated included the following: methicillin-sensitive S. aureus (45%) (57% in period Avs 40% in period B), MRSA (23%) (6% in A vs 31% in B; P < 0.001), Streptococcus pyogenes (6%), and Pseudomonas aeruginosa (5%). Children with MRSA compared with those with non-MRSA osteomyelitis had significantly greater erythrocyte sedimentation rate and C-reactive protein values on admission and increased length of hospital stay, antibiotic therapy, and overall rate of complications. We observed significant changes in antibiotic therapy related to increased use of agents with activity against MRSA.

CONCLUSIONS

Methicillin-resistant S. aureus was isolated more frequently in the second study period and was associated with worse clinical outcomes.

Skin and soft-tissue infections caused by community-acquired methicillin-resistant Staphylococcus aureus

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infection has become epidemic. Skin and soft-tissue infections (SSTIs) are the most frequent forms of the disease. Obtainment of culture specimens is important for documentation of the presence of MRSA and for susceptibility testing to guide therapy. Purulent lesions should be drained whenever possible. In areas where community-acquired MRSA isolates are prevalent, uncomplicated SSTI in healthy individuals may be treated empirically with clindamycin, trimethoprim-sulfamethoxazole, or long-acting tetracyclines, although specific data supporting the efficacy of these treatments are lacking. In healthy patients with small purulent lesions, drainage alone may be sufficient. In patients with complicated SSTI requiring hospitalization or intravenous therapy, vancomycin is the drug of choice because of the low cost, efficacy, and safety. Linezolid, daptomycin, and tigecycline are also effective, although published studies on the last 2 agents for the treatment of SSTI due to MRSA are more limited. Dalbavancin, telavancin, and ceftobiprole are investigational agents that may expand our therapeutic options for the treatment of SSTI caused by MRSA.

Community-acquired methicillin-resistant Staphylococcus aureus: an emerging pathogen in orthopaedics

Staphylococcus aureus (S aureus) remains one of the most common pathogens for skin and soft-tissue infections encountered by the orthopaedic surgeon. Community-acquired methicillin-resistant S aureus (CA-MRSA) has become increasingly prevalent, particularly among athletes, children in day care, homeless persons, intravenous drug users, men who have sex with men, military recruits, certain minorities (ie, Alaskan Natives, Native Americans, Pacific Islanders), and prison inmates. Risk factors include antibiotic use within the preceding year, crowded living conditions, compromised skin integrity, contaminated surfaces, frequent skin-to-skin contact, shared items, and suboptimal cleanliness. When a patient presents with a skin or soft-tissue infection, the clinician should determine whether an abscess or other infection needs to be surgically incised and drained. Cultures should be performed. When the patient is a member of an at-risk group or has any of the risk factors for CA-MRSA, beta-lactam antibiotics (eg, methicillin) are no longer a reasonable choice for treatment. Empiric treatment should consist of non-beta-lactam antibiotics active against CA-MRSA.

What would pediatric infectious disease consultants recommend for management of culture-negative acute hematogenous osteomyelitis?

OBJECTIVE

To assess the opinion of pediatric infectious disease (PID) specialists regarding the management of culture-negative acute hematogenous osteomyelitis.

METHODS

A questionnaire that included a hypothetical case scenario of a 4-year-old boy with culture-negative osteomyelitis was distributed via a Web-based system to PID specialists across the United States.

RESULTS

Of 481 eligible participants surveyed, 147 (31%) responded. For initial therapy of osteomyelitis, 37% of respondents chose a beta-lactam, 24% chose clindamycin, 10% chose vancomycin as the sole therapy, and 29% chose a combination of these. The initial choice of antibiotics was correlated with the reported incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) in the institution (P < 0.01). In areas where the prevalence of CA-MRSA was intermediate (between 25% and 50%), the choice of antibiotics was more heterogeneous. For change from intravenous to oral therapy, approximately 70% of respondents would change to oral therapy sooner than 3 weeks depending on clinical, laboratory, and social factors. After significant clinical and laboratory (sedimentation rate and C-reactive protein) improvements, most respondents (69%) chose to treat for a total duration (intravenous and oral) of 3 to 4 weeks.

CONCLUSIONS

This study illustrates that the empiric choice of antibiotics for treatment of acute hematogenous osteomyelitis was driven by the local prevalence of CA-MRSA. When the prevalence of CA-MRSA was intermediate, the recommendations for management of bone infections were more heterogeneous. Clinical trials are needed to compare the effect of different management strategies on outcome, side effects, and costs.

LEVEL OF EVIDENCE

Level V.

Antibiotic-resistant Staphylococcus aureus in community-acquired pediatric neck abscesses

OBJECTIVE

To determine the microbiology, particularly the prevalence of MRSA, in pediatric patients with community-acquired bacterial lymphadenitis. Long considered a nosocomial organism, methicillin-resistant Staphylococcus aureus (MRSA) has recently emerged as a cause of community-acquired infections. Resistance to other classes of antibiotics, including clindamycin, is prevalent amongst S. aureus, as well.

METHODS

A retrospective review of the medical records and culture results of patients under the age of 18 who underwent trans-cervical surgical drainage of abscessed lymph nodes between the years 2000 and 2006.

RESULTS

Sixty-two patients were identified for whom microbiology data were available. Six infections were classified as parapharyngeal on imaging; the remainder involved cervical chain lymph nodes. Forty-nine patients grew microorganisms on culture while 13 collections had no growth. The most common organism was S. aureus (63% of positive cultures); followed by beta-hemolytic group A Streptococcus (22%). Of S. aureus isolates, 27% were oxacillin-resistant (MRSA). All MRSA isolates were sensitive to clindamycin and trimethoprim/sulfamethoxazole; 63% were sensitive to ciprofloxacin, and 25% sensitive to erythromycin. Of methicillin-sensitive S. aureus isolates, 100, 86, and 82% were sensitive to trimethoprim/sulfamethoxazole, clindamycin, and ciprofloxacin, respectively. All MRSA isolates were identified during the latter half of the study period (2003-2006); none grew prior to 2003.

CONCLUSIONS

MRSA is a common pathogen in community-acquired lymphadenitis, and its incidence is rising. Resistance to clindamycin, a drug commonly used to treat MRSA, is prevalent amongst methicillin-sensitive S. aureus. This has important implications regarding the empiric treatment of lymphadenitis in children.

Community-acquired methicillin-resistant Staphylococcus aureus skin infections: a review of epidemiology, clinical features, management, and prevention

Community-acquired methicillin-resistant Staphylococcus aureus (CAMRSA) infection is a global problem of epidemic proportions. Many of the patients who develop CAMRSA skin lesions do not have infection-associated risk factors. Abscess, abscess with accompanying cellulitis, and cellulitis are the most common presentations of cutaneous CAMRSA infection; occasionally, these CARMSA-related lesions are misinterpreted as spider or insect bites. Other manifestations of cutaneous CAMRSA infection include impetigo, folliculitis, and acute paronychia. The management of CAMRSA skin infection includes incision and drainage, systemic antimicrobial therapy, and adjuvant topical antibacterial treatment. In addition, at the initial visit, bacterial culture of the lesion should be considered. Direct skin-to-skin contact, damage to the skin surface, sharing of personal items, and a humid environment are potential mechanisms for the acquisition and transmission of cutaneous CAMRSA infection. Measures that strive to eliminate these causes are useful for preventing the spread of CAMRSA skin infection.

Modes and modulations of antibiotic resistance gene expression

Since antibiotic resistance usually affords a gain of function, there is an associated biological cost resulting in a loss of fitness of the bacterial host. Considering that antibiotic resistance is most often only transiently advantageous to bacteria, an efficient and elegant way for them to escape the lethal action of drugs is the alteration of resistance gene expression. It appears that expression of bacterial resistance to antibiotics is frequently regulated, which indicates that modulation of gene expression probably reflects a good compromise between energy saving and adjustment to a rapidly evolving environment. Modulation of gene expression can occur at the transcriptional or translational level following mutations or the movement of mobile genetic elements and may involve induction by the antibiotic. In the latter case, the antibiotic can have a triple activity: as an antibacterial agent, as an inducer of resistance to itself, and as an inducer of the dissemination of resistance determinants. We will review certain mechanisms, all reversible, that bacteria have elaborated to achieve antibiotic resistance by the fine-tuning of the expression of genetic information.

Cholera-like diarrhea and shock associated with community-acquired methicillin-resistant Staphylococcus aureus (USA400 clone) pneumonia

A 14-year-old girl presented with florid watery diarrhea, vomiting and hypotension without respiratory prodrome. Shock, multiorgan system failure and death rapidly ensued. Influenza A was detected from her nasopharynx and CA-MRSA (USA400), positive for pvl, mecA, sea, sec and seh genes was cultured from a deep tracheal aspirate.

Skin and soft tissue infections

The spectrum of skin and soft tissue infections seen by the primary care physician can be as benign as folliculitis to as life-threatening as NF. Cellulitis remains the most common skin and soft tissue infection seen in primary care. The ever present danger of ca-MRSA, however, has changed the way primary care physicians approach the common problem of cellulitis. The presence of risk factors for colonization with ca-MRSA and a history or examination finding of skin abscess should raise the suspicion of ca-MRSA, and antibiotic therapy should include TMP-SMZ, clindamycin, doxycycline, or minocycline. Skin abscess may occur independently of cellulitis, and often may safely be incised and drained in the primary care setting as long as timely follow-up is assured to assess for wound healing. Available evidence suggests that abscess formation without accompanying cellulitis does not require oral antibiotic therapy. Finally, although NF is rare as an outpatient clinical presentation, it is a diagnosis that the primary care physician should be familiar with. Failure to consider the diagnosis and refer may lead to significant morbidity and even mortality.

Antimicrobial Susceptibility and Staphylococcal Chromosomal CassettemecType in Community- and Hospital-Associated Methicillin-ResistantStaphylococcus aureus

STUDY OBJECTIVE

To differentiate the characteristics of community-associated methicillin-resistant Staphylococcus aureus (MRSA) and hospital-associated MRSA isolates on the basis of their susceptibility profiles, induction of clindamycin resistance, and staphylococcal chromosomal cassette (SCC) mec types.

DESIGN

In vitro molecular and susceptibility study of isolates obtained from December 2004-January 2006 as part of a large, ongoing clinical study.

SETTING

Level I trauma center in Detroit, Michigan. BACTERIAL STRAINS: Three hundred eight MRSA isolates randomly collected from patients; 130 were classified as community-associated, and 178 were classified hospital-associated by using definitions from the Centers for Disease Control and Prevention (CDC).

INTERVENTION

Minimum inhibitory concentrations were tested on the basis of current guidelines from the Clinical and Laboratory Standards Institute.

MEASUREMENTS AND MAIN RESULTS

All tested MRSA isolates were susceptible to daptomycin, linezolid, and vancomycin. In addition, community-associated MRSA isolates were significantly (all p < or = 0.05) more susceptible to trimethoprim-sulfamethoxazole (99%), clindamycin (96%), and a fluoroquinolone (76%) than hospital-associated MRSA isolates. Inducible resistance to clindamycin was demonstrated in 8.4% of community-associated MRSA isolates versus 50% of hospital-associated MRSA isolates (p < or = 0.001). Of interest, 35% of the MRSA isolates collected from hospitalized patients (> 48 hrs after admission and according to the CDC definition) possessed SCCmec type IV.

CONCLUSION

Overall, inducible clindamycin resistance occurred at significantly higher rates in the hospital-associated MRSA isolates, susceptibility differed significantly between community- and hospital-associated MRSA, and most of the hospital isolates contained SCCmec type IV.

Community-acquired methicillin-resistant Staphylococcus aureus

Published data confirm that community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infections are increasing in incidence in both urban and rural settings. The statistical risk is higher for athletes, military personnel, prison inmates, intravenous drug abusers, the homeless, children in daycare, and certain Native American groups, but the infections are by no means restricted to these populations. Roughly 85% of the infections involve the skin and subcutaneous tissue, with the most common presentations being an abscess or folliculitis. The typical associated gene cassette is quite small and codes only for methicillin resistance. Abscesses generally respond to drainage.

LEARNING OBJECTIVE

At the conclusion of this learning activity, participants should recognize groups at high risk for community-acquired MSRA infections and manage these infections appropriately.

Fifteen-year study of the changing epidemiology of methicillin-resistant Staphylococcus aureus

PURPOSE

The study's purpose was to elucidate the evolutionary, microbiologic, and clinical characteristics of methicillin-resistant Staphylococcus aureus (MRSA) infections.

METHODS

MRSA cases from military medical facilities in San Diego, from 1990 to 2004, were evaluated and categorized as community-acquired or nosocomial. Sequence type, staphylococcal chromosomal cassette gene type, and Panton-Valentine leukocidin gene status were determined for a subset of isolates.

RESULTS

Over the 15-year period, 1888 cases of MRSA were identified; 65% were community acquired. The incidence (155 infections/100000 person-year in 2004) and household-associated cases rapidly increased since 2002. Among persons with community-acquired MRSA, 16% were hospitalized and only 17% were initially given an effective antibiotic. Community-acquired MRSA cases compared with nosocomial MRSA cases were more often soft-tissue and less often urinary, lung, or bloodstream infections (P<.001). Patients with community-acquired MRSA were younger (22 vs 64 years, P<.001) and less likely to have concurrent medical conditions (9% vs 98%, P<.001). Clindamycin resistance increased among community-acquired MRSA isolates during 2003 and 2004 compared with previous years (79% vs 13%, P<.001). Genetically, nosocomial MRSA isolates were significantly different than those acquired in the community. Although community-acquired MRSA isolates were initially diverse by 2004, one strain (staphylococcal chromosomal cassette type IV, sequence type 8, Panton-Valentine leukocidin gene positive) became the predominant isolate.

CONCLUSIONS

Community-acquired and intrafamilial MRSA infections have increased rapidly since 2002. Our 15 years of surveillance revealed the emergence of distinct community-acquired MRSA strains that were genetically unrelated to nosocomial MRSA isolates from the same community.

Low prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in a southwestern region of Germany

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) has developed into an important human pathogen and is increasingly being found to be the cause of skin and soft tissue infections or invasive infections in many communities. We have determined the prevalence of MRSA among S. aureus isolates from pediatric in- and outpatients of the University Children's Hospital of Freiburg, from children attending primary care pediatricians and from healthy children entering school in a prospective study carried out in a southwestern region of Germany. Of the healthy children tested, all between 5 and 7 years of age, 25.8% were intra-nasally colonized with S. aureus. A total of 1455 S. aureus isolates were tested for antibiotic susceptibility. Apart from penicillin resistance (82.1%), an overall high susceptibility of S. aureus to antibiotics, including clindamycin, was common, while resistance among the S. aureus isolates to erythromycin and clindamycin had even significantly decreased from 2002 to 2004. Methicillin-resistance was exceedingly rare (0.3%).

CONCLUSION

In the southwestern region of Germany, about one quarter of the healthy children tested at school entry were found to be colonized with S. aureus. The prevalence of MRSA among healthy as well as hospitalized children colonized with S. aureus is still extremely rare in this region.

Ophthalmic Manifestations of Infections Caused by the USA300 Clone of Community-Associated Methicillin-Resistant Staphylococcus aureus

PURPOSE

To report the microbiological, clinical, and pathological characteristics of community-associated methicillin-resistant Staphylococcus aureus (CAMRSA) infections of the eye and orbit.

DESIGN

Prospective case series.

PARTICIPANTS

Nine patients with CAMRSA infections of the eye and orbit were identified during a 6-month period at 2 tertiary care hospitals in San Francisco.

METHODS

Case identification was by prospective case selection and retrospective laboratory review of 549 MRSA cultures collected in the 2 hospitals. Ophthalmic microbial isolates were analyzed by pulsed-field gel electrophoresis and compared with a control CAMRSA clone (USA300). Clinical characteristics of patients infected with CAMRSA were reviewed, and all surgical specimens underwent pathological examination.

MAIN OUTCOME MEASURES

Pulsed-field gel electrophoresis banding patterns of MRSA isolates, antibiotic sensitivity profiles, patient demographics, systemic and ocular complications of infection, and posttreatment visual acuities.

RESULTS

Nine ophthalmic isolates were CAMRSA clone USA300. The infections included orbital cellulitis, endogenous endophthalmitis, panophthalmitis, lid abscesses, and septic venous thrombosis. Patients were treated with trimethoprim-sulfamethoxazole, rifampin, clindamycin, or vancomycin based on microbial sensitivity studies and severity of infection. Eight of the 9 patients had no history of hospitalization. Seven patients required hospitalization, 3 required surgery, and an additional 4 required invasive procedures. Eight patients had good visual outcomes, but 1 deteriorated to no light perception. Pathological analyses showed extensive necrosis in eyelid and orbital specimens, and disorganized atrophy bulbi in an enucleated eye.

CONCLUSION

The USA300 CAMRSA clone, which carries Panton-Valentine leukocidin genes, can cause aggressive infections of the eye and orbit in hospital-naive patients. Treatment of infections often required debridement of necrotic tissues in addition to non-beta-lactam class antibiotics. In communities where CAMRSA is prevalent, ophthalmologists should obtain microbial cultures and sensitivity studies to help guide antibiotic therapy for severe ophthalmic infections.

Community-associated Methicillin-resistant Staphylococcus aureus: Overview and Local Situation

Introduction: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged worldwide. In contrast to healthcare-associated MRSA (HA-MRSA), CA-MRSA isolates are usually susceptible to multiple non-beta-lactam antibiotics and cause a distinct spectrum of infections in epidemiologically disparate populations – in particular, cutaneous abscesses, necrotising fasciitis and necrotising pneumonia. They arise from a broader genetic background, and possess differing virulence genes. We aim to describe the distribution of different molecular subtypes of CA-MRSA among various regions and discuss briefly the implications of CA-MRSA from a local perspective. Methods: Literature review of articles on CA-MRSA, focusing mainly on reports where the genetic background of isolates had been analysed using multi-locus sequence typing (MLST). Singapore data were obtained from the local CA-MRSA database. Results: MLST analysis demonstrated the presence of epidemic subtypes of CA-MRSA within most geographic areas. In parts of the United States, community MRSA infections currently exceed those caused by their methicillin-susceptible counterparts. In Singapore, CA-MRSA infections are increasing, predominantly as a result of the spread of ST30 clones. Conclusion: Available evidence suggests that the emergence of MRSA from the community is not going to be a transient phenomenon. Local guidelines for dealing with this phenomenon at both therapeutic and preventive levels are needed prior to the potential development of a situation mirroring that of meso-endemic HA-MRSA in local hospitals or CA-MRSA epidemics in parts of USA. Key words: Bacterial typing, Epidemic, Epidemiology, Infection control