Fredrick M. Abrahamian

Bacteriologic Analysis of Infected Dog and Cat Bites

BACKGROUND AND METHODS To define better the bacteria responsible for infections of dog and cat bites, we conducted a prospective study at 18 emergency departments. To be eligible for enrollment, patients had to meet one of three major criteria for infection of a bite wound (fever, abscess, and lymphangitis) or four of five minor criteria (wound-associated erythema, tenderness at the wound site, swelling at the site, purulent drainage, and leukocytosis). Wound specimens were cultured for aerobic and anaerobic bacteria at a research microbiology laboratory and, in some cases, at local hospital laboratories. RESULTS The infected wounds of 50 patients with dog bites and 57 patients with cat bites yielded a median of 5 bacterial isolates per culture (range, 0 to 16) at the reference laboratory. Significantly more isolates grew at the reference laboratory than at the local laboratories (median, 1; range, 0 to 5; P<0.001). Aerobes and anaerobes were isolated from 56 percent of the wounds, aerobes alone from 36 percent, and anaerobes alone from 1 percent; 7 percent of cultures had no growth. Pasteurella species were the most frequent isolates from both dog bites (50 percent) and cat bites (75 percent). Pasteurella canis was the most common isolate of dog bites, and Past. multocida subspecies multocida and septica were the most common isolates of cat bites. Other common aerobes included streptococci, staphylococci, moraxella, and neisseria. Common anaerobes included fusobacterium, bacteroides, porphyromonas, and prevotella. Isolates not previously identified as human pathogens included Reimerella anatipestifer from two cat bites and Bacteroides tectum, Prevotella heparinolytica, and several porphyromonas species from dog and cat bites. Erysipelothrix rhusiopathiae was isolated from two cat bites. Patients were most often treated with a combination of a beta-lactam antibiotic and a beta-lactamase inhibitor, which, on the basis of the microbiologic findings, was appropriate therapy. CONCLUSIONS Infected dog and cat bites have a complex microbiologic mix that usually includes pasteurella species but may also include many other organisms not routinely identified by clinical microbiology laboratories and not previously recognized as bite-wound pathogens.

Methicillin-resistant Staphylococcus aureus in community-acquired skin infections.

Community-associated methicillin-resistant Staphylococcus aureus (MRSA) is the most common pathogen among patients with skin and soft tissue infections seeking treatment at a Los Angeles (USA) area emergency department. The proportion caused by MRSA increased from 29% in 2001 to 2002 to 64% in 2003 to 2004. No clinical or historical features reliably predict MRSA etiology.

Microbiology of Animal Bite Wound Infections

SUMMARY The microbiology of animal bite wound infections in humans is often polymicrobial, with a broad mixture of aerobic and anaerobic microorganisms. Bacteria recovered from infected bite wounds are most often reflective of the oral flora of the biting animal, which can also be influenced by the microbiome of their ingested prey and other foods. Bacteria may also originate from the victims own skin or the physical environment at the time of injury. Our review has focused on bite wound infections in humans from dogs, cats, and a variety of other animals such as monkeys, bears, pigs, ferrets, horses, sheep, Tasmanian devils, snakes, Komodo dragons, monitor lizards, iguanas, alligators/crocodiles, rats, guinea pigs, hamsters, prairie dogs, swans, and sharks. The medical literature in this area has been made up mostly of small case series or case reports. Very few studies have been systematic and are often limited to dog or cat bite injuries. Limitations of studies include a lack of established or inconsistent criteria for an infected wound and a failure to utilize optimal techniques in pathogen isolation, especially for anaerobic organisms. There is also a lack of an understanding of the pathogenic significance of all cultured organisms. Gathering information and conducting research in a more systematic and methodical fashion through an organized research network, including zoos, veterinary practices, and rural clinics and hospitals, are needed to better define the microbiology of animal bite wound infections in humans.

Clinical Presentation and Bacteriologic Analysis of Infected Human Bites in Patients Presenting to Emergency Departments

Previous studies of infected human bites have been limited by small numbers of patients and suboptimal microbiologic methodology. We conducted a multicenter prospective study of 50 patients with infected human bites. Seventy percent of the patients and assailants were young adult men. Fifty-six percent of injuries were clenched-fist injuries and 44% were occlusional bites. Most injuries were to the hands. Fifty-four percent of patients were hospitalized. The median number of isolates per wound culture was 4 (3 aerobes and 1 anaerobe); aerobes and anaerobes were isolated from 54% of wounds, aerobes alone were isolated from 44%, and anaerobes alone were isolated from 2%. Isolates included Streptococcus anginosus (52%), Staphylococcus aureus (30%), Eikenella corrodens (30%), Fusobacterium nucleatum (32%), and Prevotella melaninogenica (22%). Candida species were found in 8%. Fusobacterium, Peptostreptococcus, and Candida species were isolated more frequently from occlusional bites than from clenched-fist injuries. Many strains of Prevotella and S. aureus were beta-lactamase producers. Amoxicillin-clavulanic acid and moxifloxacin demonstrated excellent in vitro activity against common isolates.

Prevalence and Risk Factor Analysis of Trimethoprim-Sulfamethoxazole— and Fluoroquinolone-Resistant Escherichia coli Infection among Emergency Department Patients with Pyelonephritis

BACKGROUND High rates of resistance to trimethoprim-sulfamethoxazole (TMP-SMX) among uropathogenic Escherichia coli are recognized, and concerns exist about emerging fluoroquinolone resistance. METHODS Adults presenting to 11 US emergency departments with (1) flank pain and/or costovertebral tenderness, (2) temperature >38 degrees C, and (3) a presumptive diagnosis of pyelonephritis were enrolled; patients for whom 1 uropathogen grew on culture were analyzed. Epidemiologic and clinical data were collected at the time of care. The prevalence of E. coli in vitro antibiotic resistance and risk factors associated with TMP-SMX-resistant E. coli infection were determined. RESULTS Among 403 women with uncomplicated pyelonephritis caused by E. coli, the mean site rate of E. coli resistance to TMP-SMX was 24% (range, 13%-45%). Mean site rates of E. coli resistance to ciprofloxacin and levofloxacin were 1% and 3%, respectively. Only TMP-SMX exposure within 2 days before presentation and Hispanic ethnicity were associated with E. coli resistance to TMP-SMX (compared with resistance rates of approximately 20% among women lacking these risk factors); antibiotic exposure within 3-60 days before presentation, health care setting exposure within 30 days before presentation, history of urinary tract infections, and age >55 years were not associated with E. coli resistance to TMP-SMX. Among 207 patients with complicated pyelonephritis, mean site rates of E. coli resistance to ciprofloxacin and levofloxacin were 5% and 6%, respectively. CONCLUSIONS These results suggest that the prevalence of TMP-SMX-resistant infection among patients with uncomplicated pyelonephritis is > or =20% in many areas of the United States, and risk stratification cannot identify patients at low risk of infection. Rates of fluoroquinolone-resistant E. coli infection appear to be low among patients with uncomplicated pyelonephritis but higher among those with complicated infections. Fluoroquinolones should remain to be the preferred empirical treatment for women with uncomplicated pyelonephritis.

Trimethoprim–Sulfamethoxazole versus Placebo for Uncomplicated Skin Abscess

BACKGROUND U.S. emergency department visits for cutaneous abscess have increased with the emergence of methicillin-resistant Staphylococcus aureus (MRSA). The role of antibiotics for patients with a drained abscess is unclear. METHODS We conducted a randomized trial at five U.S. emergency departments to determine whether trimethoprim-sulfamethoxazole (at doses of 320 mg and 1600 mg, respectively, twice daily, for 7 days) would be superior to placebo in outpatients older than 12 years of age who had an uncomplicated abscess that was being treated with drainage. The primary outcome was clinical cure of the abscess, assessed 7 to 14 days after the end of the treatment period. RESULTS The median age of the participants was 35 years (range, 14 to 73); 45.3% of the participants had wound cultures that were positive for MRSA. In the modified intention-to-treat population, clinical cure of the abscess occurred in 507 of 630 participants (80.5%) in the trimethoprim-sulfamethoxazole group versus 454 of 617 participants (73.6%) in the placebo group (difference, 6.9 percentage points; 95% confidence interval [CI], 2.1 to 11.7; P=0.005). In the per-protocol population, clinical cure occurred in 487 of 524 participants (92.9%) in the trimethoprim-sulfamethoxazole group versus 457 of 533 participants (85.7%) in the placebo group (difference, 7.2 percentage points; 95% CI, 3.2 to 11.2; P<0.001). Trimethoprim-sulfamethoxazole was superior to placebo with respect to most secondary outcomes in the per-protocol population, resulting in lower rates of subsequent surgical drainage procedures (3.4% vs. 8.6%; difference, -5.2 percentage points; 95% CI, -8.2 to -2.2), skin infections at new sites (3.1% vs. 10.3%; difference, -7.2 percentage points; 95% CI, -10.4 to -4.1), and infections in household members (1.7% vs. 4.1%; difference, -2.4 percentage points; 95% CI, -4.6 to -0.2) 7 to 14 days after the treatment period. Trimethoprim-sulfamethoxazole was associated with slightly more gastrointestinal side effects (mostly mild) than placebo. At 7 to 14 days after the treatment period, invasive infections had developed in 2 of 524 participants (0.4%) in the trimethoprim-sulfamethoxazole group and in 2 of 533 participants (0.4%) in the placebo group; at 42 to 56 days after the treatment period, an invasive infection had developed in 1 participant (0.2%) in the trimethoprim-sulfamethoxazole group. CONCLUSIONS In settings in which MRSA was prevalent, trimethoprim-sulfamethoxazole treatment resulted in a higher cure rate among patients with a drained cutaneous abscess than placebo. (Funded by the National Institute of Allergy and Infectious Diseases; ClinicalTrials.gov number, NCT00729937.).

Acute bacterial skin infections: developments since the 2005 Infectious Diseases Society of America (IDSA) guidelines.

BACKGROUND Patients with acute bacterial skin and skin structure infections (ABSSSI) commonly present to Emergency Departments (EDs) where physicians encounter a wide spectrum of disease severity. The prevalence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has increased in the past decade, and CA-MRSA is now a predominant cause of purulent ABSSSI in the United States (US). OBJECTIVES This article reviews significant developments since the most recent Infectious Diseases Society of America (IDSA) guidelines for the management of ABSSSI in the CA-MRSA era, focusing on recent studies and recommendations for managing CA-MRSA, newer antimicrobials with improved MRSA activity, new diagnostic technologies, and options for outpatient parenteral antimicrobial therapy (OPAT). DISCUSSION The increasing prevalence of CA-MRSA has led the IDSA and other organizations to recommend empiric coverage of CA-MRSA for purulent ABSSSI. The availability of rapid MRSA detection assays from skin and soft tissue swabs could potentially facilitate earlier selection of targeted antimicrobial therapy. Several newer intravenous antibiotics with expanded MRSA coverage, including ceftaroline fosamil, daptomycin, linezolid, and telavancin, may be utilized for treatment of ABSSSI. OPAT may be an option for intravenous administration of antibiotics in selected patients and may prevent or shorten hospitalizations, decrease readmission rates, and reduce nosocomial infections and complications. CONCLUSION The growing prevalence of CA-MRSA associated with ABSSSI in the US has a significant impact on clinical management decisions in the ED. Recent availability of new diagnostic testing and therapeutic options may help meet the demand for effective antistaphylococcal agents.

Management of skin and soft-tissue infections in the emergency department.

Skin and soft-tissue infections are among the most common infections encountered by emergency physicians. This article is written from the perspective of the initial evaluation and management of skin and soft-tissue infections in the emergency department. Management pitfalls and clinical dilemmas pertinent to emergency physicians that are not often encountered by infectious disease specialists are highlighted. Special emphasis is placed on the utility of wound and blood cultures, disposition, methicillin-resistant Staphylococcus aureus infections, animal and human bites, and necrotizing skin and soft-tissue infections.

Antimicrobial prophylaxis for wounds and procedures in the emergency department.

Emergency physicians are often confronted with situations in which a patient with an acute injury is at high risk for an infection. Although most traumatic wounds have a low risk for developing infection, certain types of high-risk trauma justify antimicrobial prophylaxis. This article reviews antimicrobial wound infection prophylaxis for high-risk traumatic wounds, including the prevention of rabies and tetanus. Prophylaxis to prevent infections related to invasive procedures in the emergency department is also addressed.

Emergency Department Management of Meningitis and Encephalitis

Bacterial meningitis and viral encephalitis are infectious disease emergencies that can cause significant patient morbidity and mortality. Clinicians use epidemiologic, historical, and physical examination findings to identify patients at risk for these infections, and central nervous system (CNS) imaging and lumbar puncture (LP) may be needed to further evaluate for these diagnoses. The diagnosis of bacterial meningitis can be challenging, as patients often lack some of the characteristic findings of this disease with presentations that overlap with more common disorders seen in the emergency department. This article addresses considerations in clinical evaluation, need for CNS imaging before LP, interpretation of cerebrospinal fluid results, standards for and effects of timely antibiotic administration, and recommendations for specific antimicrobial therapy and corticosteroids.