Diagnostic clinical microbiology.

Technological advancements have changed the way clinical microbiology laboratories are detecting and identifying bacterial, viral, parasitic, and yeast/fungal pathogens. Such advancements have improved sensitivity and specificity and reduce turnaround time to reporting of clinically important results. This article discusses and reviews some traditional methodologies along with some of the technological innovations introduced into diagnostic microbiology laboratories. Some insight to what might be available in the coming years is also discussed.

In vitro killing of canine strains of Staphylococcus pseudintermedius and Escherichia coli by cefazolin, cefovecin, doxycycline and pradofloxacin over a range of bacterial densities.

BACKGROUND: Bacterial densities likely fluctuate during infection and may exceed the bacterial density used in susceptibility testing. As such, investigation of bacterial killing by antibiotics over a range of varying bacterial densities may provide important differences between compounds and could impact drug selection for therapy. HYPOTHESIS/OBJECTIVES: To measure killing of clinical isolates of Staphylococcus pseudintermedius and Escherichia coli by cefazolin, cefovecin, doxycycline and pradofloxacin at clinically relevant (minimum inhibitory, mutant prevention, maximum serum and maximum tissue) drug concentrations against varying densities of bacteria. ANIMALS/MATERIALS: Bacterial strains collected from dogs with urinary tract infections were studied. METHODS AND MATERIALS: High bacterial densities ranging from 106 to 109 colony forming units (cfu)/mL were exposed to minimum inhibitory, mutant prevention, blood and tissue drug concentrations, and the percentages (log10 ) of viable cells killed following 30 min, 1, 2, 4, 6, 12 and 24 h of drug exposure were quantified. RESULTS: Doxycycline exhibited bacteriostatic properties with less killing than the other three agents. For example, at a 107  cfu/mL density of S. pseudintermedius, more cells were killed by pradofloxacin (P < 0.0001) and cefovecin (P = 0.0014) but not cefazolin when compared to doxycycline at the maximum serum drug concentration following 12 h of drug exposure. CONCLUSIONS AND CLINICAL IMPORTANCE: Differences were seen between some drugs in the speed and extent of bacterial killing; this could be clinically important and may impact drug selection and length of therapy.

Characterization of carbapenem-resistant and XDR Pseudomonas aeruginosa in Canada: results of the CANWARD 2007-16 study.

OBJECTIVES: Carbapenem-resistant Pseudomonas aeruginosa are emerging worldwide with increasing reports of carbapenemase-producing isolates. Carbapenem-resistant isolates may also be XDR. This study characterized carbapenem-resistant and XDR P. aeruginosa isolated from patients receiving care at Canadian hospitals from 2007 to 2016. METHODS: Antimicrobial susceptibility testing was performed using CLSI broth microdilution methods. PCR was used to detect carbapenemases (GES, KPC, NDM, IMP, VIM, OXA-48) and other resistance markers; specific carbapenemase gene variants were identified by DNA sequencing. Genetic relatedness was assessed by MLST and PFGE. RESULTS: From 2007 to 2016, 3864 isolates of P. aeruginosa were collected; 466 (12.1%) isolates were carbapenem resistant. The prevalence of carbapenem-resistant P. aeruginosa reached a peak of 17.3% in 2014. Colistin (94% susceptible) and ceftolozane/tazobactam (92.5%) were the most active agents against carbapenem-resistant P. aeruginosa. XDR P. aeruginosa comprised 4.5% of isolates; they were found to be genetically diverse and remained susceptible to colistin and ceftolozane/tazobactam. Only 4.3% (n = 20) of carbapenem-resistant P. aeruginosa harboured a carbapenemase; most were blaGES-5 (35%, n = 7). Wide genetic diversity was observed among carbapenem-resistant P. aeruginosa with >200 different sequence types identified. CONCLUSIONS: Although the prevalence of carbapenem-resistant P. aeruginosa in Canada spiked in 2014 and 2015, carbapenemase-producing P. aeruginosa remain rare with only 20 (4.3%) isolates identified over a 10 year period. Broad genetic diversity was observed among both carbapenem-resistant and XDR phenotypes of P. aeruginosa. Pan-drug-resistant P. aeruginosa have not yet been identified in Canada.

A pilot study on the comparative minimum inhibitory and mutant prevention concentration values for moxifloxacin and pradofloxacin against canine and human isolates of Staphylococcus pseudintermedius and S. schleiferi.

BACKGROUND: Moxifloxacin is a fourth-generation fluoroquinolone (FQ) that is approved for use in people to treat a variety of infections. Some veterinary microbiology laboratories report moxifloxacin in culture and sensitivity profiles for Staphylococcus pseudintermedius and S. schleiferi albeit using Clinical & Laboratory Standards Institute (CLSI) breakpoints for S. aureus. Previous studies have shown that S. aureus breakpoints can mischaracterize S. pseudintermedius susceptibility to various drugs. Pradofloxacin is a third generation veterinary FQ with a similar mechanism of action and spectrum of activity to moxifloxacin; however, the dose format (25 mg/mL solution) available in the USA may limit its practical use in large dogs. OBJECTIVE: To determine the minimum inhibitory concentration (MIC), mutant prevention concentration (MPC) and mutant selection window (MSW) of moxifloxacin and pradofloxacin for isolates of S. pseudintermedius and S. schleiferi. METHODS AND MATERIALS: Pulsed-field gel electrophoresis was performed to establish that each bacterial isolate selected for testing represented an unique strain. The MIC, MPC and MSW for moxifloxacin and pradofloxacin were determined from 60 strains of S. pseudintermedius and seven strains of S. schleiferi. RESULTS: The MIC and MPC ranges of moxifloxacin and pradofloxacin for meticillin-susceptible S. pseudintermedius were similar. However, MIC and MPC ranges were much wider and resistance to both drugs was more common for meticillin-resistant strains of S. pseudintermedius and S. schleiferi. CONCLUSIONS AND CLINICAL IMPORTANCE: The narrow MSW of these drugs may reduce the risk of selecting for antibiotic-resistant subpopulations. Pharmacokinetic, pharmacodynamic and safety studies are needed.

The in vitro antibacterial activity of the anthelmintic drug oxyclozanide against common small animal bacterial pathogens.

BACKGROUND: Repurposing existing drugs is one approach to address the growing concerns of multi-drug resistant bacterial pathogens in veterinary medicine. Oxyclozanide is in the anthelmintic drug class salicylanilide, which has been used primarily as a treatment and preventative for Fasciola hepatica in ruminants. The antimicrobial activity of oxyclozanide has been studied in human medicine; its activity against common small animal bacterial pathogens such as Staphylococcus pseudintermedius has yet to be determined. OBJECTIVE: The aim of this study was to measure and establish the minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) of oxyclozanide against S. pseudintermedius and other common small animal bacterial pathogens. METHODS AND MATERIALS: The MIC and MPC of oxyclozanide were determined from eighteen meticillin sensitive S. pseudintermedius (MSSP) isolates and eleven meticillin-resistant S. pseudintermedius (MRSP), as well as single isolates of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis. RESULTS: The MIC of the eighteen meticillin-sensitive S. pseudintermedius isolates was 0.5-1 µg/mL and the MPC ranged between 16 and 32 µg/mL. The MIC of the eleven meticillin-resistant strains of S. pseudintermedius ranged from 0.5 to 2 µg/mL with a MPC ranging between 16 and 32 µg/mL. A single isolate of meticillin-resistant S. aureus (MRSA) had an MIC of 1 µg/mL and MPC 16 µg/mL. No inhibition of growth was seen at the concentrations tested for bacterial isolate strains E. coli, P. aeruginosa and E. faecalis. CONCLUSION AND CLINICAL IMPORTANCE: Oxyclozanide demonstrated in-vitro antibacterial activity against meticillin-resistant S. pseudintermedius. Further studies are needed to evaluate the potential use of oxyclozanide as a topical bactericidal agent.

Comparative in vitro killing of canine strains of Staphylococcus pseudintermedius and Escherichia coli by cefovecin, cefazolin, doxycycline and pradofloxacin.

BACKGROUND: Bacterial eradication is necessary for clinical cure of infections and antimicrobial agents are important adjunctive therapies for inhibiting the growth of or killing bacteria. Pre-existing skin diseases predispose animals to infection by Staphylococcus pseudintermedius and, more rarely, by Gram-negative bacilli. The property of rapid killing of bacteria may influence drug selection and duration of therapy in the setting of infection. OBJECTIVES: To test the killing of canine isolates of S. pseudintermedius and Escherichia coli by cefazolin, cefovecin, doxycycline and pradofloxacin at the minimum inhibitory, mutant prevention, maximum serum and maximum tissue drug concentrations. METHODS: Under standard conditions, bacterial cells were exposed to clinically relevant drug concentrations in vitro and the log10 reduction (and % kill) of viable cells measured at 5, 10, 15, 20, 25, 30, 60, 120 and 180 min after drug exposure. RESULTS: Statistically significant differences were seen between killing efficiencies by pradofloxacin versus the other agents, whereby pradofloxacin killed cells more rapidly than the others. For example, against the S. pseudintermedius strains, significantly more cells were killed by pradofloxacin following 15 min of maximum tissue drug concentration exposure than for cefazolin (P = 0.0002), cefovecin (P = 0.0007) and doxycycline (P ≤ 0.0001). CONCLUSION AND CLINICAL IMPORTANCE: The rank order of potency based on these kill experiments was pradofloxacin > cefazolin > cefovecin > doxycycline. Rapid killing of bacteria affects the speed of clinical resolution and may influence drug selection and duration of therapy for skin infections.

Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis (Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases).

BACKGROUND: Superficial bacterial folliculitis (SBF) is usually caused by Staphylococcus pseudintermedius and routinely treated with systemic antimicrobial agents. Infection is a consequence of reduced immunity associated with alterations of the skin barrier and underlying diseases that may be difficult to diagnose and resolve; thus, SBF is frequently recurrent and repeated treatment is necessary. The emergence of multiresistant bacteria, particularly meticillin-resistant S. pseudintermedius (MRSP), has focused attention on the need for optimal management of SBF. OBJECTIVES: Provision of an internationally available resource guiding practitioners in the diagnosis, treatment and prevention of SBF. DEVELOPMENT OF THE GUIDELINES: The guidelines were developed by the Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases, with consultation and advice from diplomates of the American and European Colleges of Veterinary Dermatology. They describe optimal methods for the diagnosis and management of SBF, including isolation of the causative organism, antimicrobial susceptibility testing, selection of antimicrobial drugs, therapeutic protocols and advice on infection control. Guidance is given for topical and systemic modalities, including approaches suitable for MRSP. Systemic drugs are classified in three tiers. Tier one drugs are used when diagnosis is clear cut and risk factors for antimicrobial drug resistance are not present. Otherwise, tier two drugs are used and antimicrobial susceptibility tests are mandatory. Tier three includes drugs reserved for highly resistant infections; their use is strongly discouraged and, when necessary, they should be used in consultation with specialists. CONCLUSIONS AND CLINICAL IMPORTANCE: Optimal management of SBF will improve antimicrobial use and reduce selection of MRSP and other multidrug-resistant bacteria affecting animal and human health.

Comparative Minimum Inhibitory and Mutant Prevention Drug Concentrations for Pradofloxacin and Seven Other Antimicrobial Agents Tested against Bovine Isolates of Mannheimia haemolytica and Pasteurella multocida.

Pradofloxacin-a dual-targeting fluoroquinolone-is the most recent approved for use in food animals. Minimum inhibitory and mutant prevention concentration values were determined for pradofloxacin, ceftiofur, enrofloxacin, florfenicol, marbofloxacin, tildipirosin, tilmicosin, and tulathromycin. For M. haemolytica strains, MIC50/90/100 values were ≤0.016/≤0.016/≤0.016 and MPC50/90/100 values were 0.031/0.063/0.063; for P. multocida strains, the MIC50/90/100 values ≤0.016/≤0.016/0.031 and MPC50/90/100 ≤ 0.016/0.031/0.063 for pradofloxacin. The pradofloxacin Cmax/MIC90 and Cmax/MPC90 values for M. haemolytica and P. multocida strains, respectively, were 212.5 and 53.9 and 212.5 and 109.7. Similarly, AUC24/MIC90 and AUC24/MPC90 for M. haemolytica were 825 and 209.5, and for P. multocida, they were 825 and 425.8. Pradofloxacin would exceed the mutant selection window for >12-16 h. Pradofloxacin appears to have a low likelihood for resistance selection against key bovine respiratory disease bacterial pathogens based on low MIC and MPC values.

Comparative In Vitro Killing by Pradofloxacin in Comparison to Ceftiofur, Enrofloxacin, Florfenicol, Marbofloxacin, Tildipirosin, Tilmicosin and Tulathromycin against Bovine Respiratory Bacterial Pathogens.

Pradofloxacin is the newest of the veterinary fluoroquinolones to be approved for use in animals-initially companion animals and most recently food animals. It has a broad spectrum of in vitro activity, working actively against Gram-positive/negative, atypical and some anaerobic microorganisms. It simultaneously targets DNA gyrase (topoisomerase type II) and topoisomerase type IV, suggesting a lower propensity to select for antimicrobial resistance. The purpose of this study was to determine the rate and extent of bacterial killing by pradofloxacin against bovine strains of Mannheimia haemolytica and Pasteurella multocida, in comparison with several other agents (ceftiofur, enrofloxacin, florfenicol, marbofloxacin, tildipirosin, tilmicosin and tulathromycin) using four clinically relevant drug concentrations: minimum inhibitory and mutant prevention drug concentration, maximum serum and maximum tissue drug concentrations. At the maximum serum and tissue drug concentrations, pradofloxacin killed 99.99% of M. haemolytica cells following 5 min of drug exposure (versus growth to 76% kill rate for the other agents) and 94.1-98.6% of P. multocida following 60-120 min of drug exposure (versus growth to 98.6% kill rate for the other agents). Statistically significant differences in kill rates were seen between the various drugs tested depending on drug concentration and time of sampling after drug exposure.

In vitro killing of drug susceptible and multidrug resistant bacteria by amikacin considering pulmonary drug concentrations based on an inhaled formulation.

Nosocomial infections with drug resistant bacteria impact morbidity and mortality, length of therapy and stay and the overall cost of treatment. Key pathogens with ventilator associated pneumonia may be drug-susceptible or multi-drug resistant and inhaled amikacin has been investigated as an adjunctive therapy option. High pulmonary drug concentrations (epithelial lining fluid [ELF]) along with minimal systemic toxicity is seen as an advantage to inhaled formulations. In vitro killing of bacteria using clinically relevant drug concentrations provide insight on bug-drug interactions. The aim of this study was to measure killing of clinical isolates of Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus and methicillin-susceptible S. aureus using the minimum inhibitory concentration (MIC), mutant prevention concentration (MPC) and median (976 µg/ml) ELF drug concentration for amikacin. Overall killing took longer at the MIC drug concentration and was inconsistent amongst the pathogens tested with the percentage of bacteria killed following 180 min of drug exposure ranging from growth in the presence of the drug to 95% kill. At the MPC drug concentrations, killing ranged from 55-88% for all pathogens following 30 min of drug exposure and increased to 99-100% following 180 min of drug exposure. At the ELF amikacin tested, killing was 81-100% following 20 min and 94-100% by 30 min of drug exposure. Rapid killing against MDR respiratory pathogens by amikacin ELF drug concentrations is encouraging.

Recovery of Vandammella animalimorsus from an immunocompetent female patient following cat bite to the lower leg.

We report a case of Vandammella animalimorsus in an adult female patient following a cat scratch/bite. Animal bite/scratches may lead to zoonotic transmission of bacteria that subsequently lead to infection. Wound management and antimicrobial therapy is often necessary. The organism was initially misidentified as Neisseria animaloris/zoodegmatis and highlights the difficulty of correctly identifying some bacteria in clinical microbiology laboratories.

Dogs and cats carry bacteria that are not carried in humans. Dog and cat bites or scratches may lead to these bacteria being spread to humans. This can lead to infection. These infections are usually treated by wound care and antibiotics. We describe a case of infection in a human with a bacteria from a cat following a cat bite/scratch to the patient's leg and discuss how the infection was diagnosed and treated.

Microbiological analysis of tunneled hemodialysis catheters isolated from patients receiving hemodialysis in Saskatchewan.

Aim: To compare the microbial communities inside hemodialysis catheters from symptomatic and asymptomatic patients to determine their differences.Materials & methods: Catheters (n = 41) were removed from patients in the Saskatchewan Health Authority over an 18-month period. The catheter section inside the body was flushed and the contents were evaluated using culture-dependent and culture-independent analysis.Results: All catheters were colonized by bacteria, with considerable overlap between groups based on microbial communities and the individual species detected. More Gram-negative species were detected by sequencing, whereas predominantly Gram-positive strains were cultured. Antibiotic resistance and biofilm formation was widespread and not correlated with either catheter group.Conclusion: Common pathogens were detected in each set of catheters, therefore predicting infections based on the microbiology is difficult.

Many patients use catheters to help clean their blood, a process called hemodialysis. The use of catheters is also associated with complications, such as blood infections. We looked at the types of bacteria associated with catheters from patients who had infections (n = 21) and compared them to catheters from patients who had no signs of infection (n = 20). Once removed from the patient, we flushed out each catheter and tried to grow bacteria in different conditions. We also looked at DNA from within the catheter to identify bacterial species that were present. All 41 catheters had bacteria and there were many common species detected. We detected species known to cause illness such as Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Pseudomonas, Enterobacter, Morganella and Stenotrophomonas species. S. aureus was only grown from patients that had infections. Resistance to antibiotics was found to be common in bacteria grown from catheters. This did not seem to be influenced by whether patients were infected or not. Finally, we identified several catheters where two species, S. epidermidis and P. aeruginosa, were detected together. Our main conclusion was that bacteria are commonly present inside catheters that are used for hemodialysis, regardless of whether patients are infected or not.

Minimal inhibitory and mutant prevention concentrations of azithromycin, clarithromycin and erythromycin for clinical isolates of Streptococcus pneumoniae.

BACKGROUND: Previous work showed a higher prevalence of macrolide/azalide resistance in provinces of Canada where azithromycin was the major treatment for Streptococcus pneumoniae as compared with regions where clarithromycin was the dominant treatment. These data provided a way to test the mutant selection window hypothesis, which predicts that the serum drug concentration (AUC(24)) relative to the mutant prevention concentration (MPC) would be higher for clarithromycin than for azithromycin. METHODS: The MIC and MPC were determined for 191 penicillin/macrolide-susceptible clinical isolates of S. pneumoniae with azithromycin, clarithromycin and erythromycin using agar plate assays. RESULTS: The MIC(50/90) (mg/L) and MPC(50/90) (mg/L), respectively, were as follows: azithromycin 0.13/0.25 and 1/4; clarithromycin 0.031/0.063 and 0.13/0.5; erythromycin 0.063/0.13 and 0.25/2. We calculated from published pharmacokinetic values that the AUC(24)/MPC(90) for azithromycin was 0.85; for clarithromycin it was 96, and for erythromycin base and estolate it was 4 and 10, respectively. Thus the AUC(24)/MPC(90) was about 50 times higher for clarithromycin than for azithromycin. CONCLUSIONS: The elevated prevalence of azithromycin resistance may derive in part from a low value of AUC(24)/MPC(90) and/or time above MPC, since previous work indicates that the number of prescriptions per person was similar in the geographical regions examined.

Trends in antibiotic resistance over time among pathogens from Canadian hospitals: results of the CANWARD study 2007-11.

OBJECTIVES: Antimicrobial resistance patterns change over time and longitudinal surveillance studies provide insight into these trends. We sought to describe the important trends in antimicrobial resistance in key pathogens across Canada to provide useful information to clinicians, policy makers and industry, to assist in optimizing antimicrobial therapy, formulary choices and drug development. METHODS: We analysed longitudinal data from the CANWARD study using a multivariate regression model to control for possible effects of patient demographics on resistance, in order to assess the impact of time on antimicrobial resistance independent of other measured variables. RESULTS: We identified several key trends in common pathogens. In particular, we observed a statistically significant increase in the proportion of Escherichia coli isolates that were resistant to extended-spectrum cephalosporins and fluoroquinolones, an increase in the proportion of Klebsiella pneumoniae isolates that were resistant to extended-spectrum cephalosporins, a reduction in the proportion of Staphylococcus aureus that were methicillin, clindamycin and trimethoprim/sulfamethoxazole resistant, and a reduction in the proportion of Pseudomonas aeruginosa that were fluoroquinolone and gentamicin resistant. CONCLUSIONS: Although some of these trends, such as the dramatic increase in fluoroquinolone and cephalosporin resistance in E. coli, can be attributed to the emergence and global spread of resistant clones (e.g. ST131 E. coli), others remain unexplained. However, recognizing these trends remains important to guide changes in empirical antimicrobial therapy and drug development.

Immunomodulatory Effects of Macrolides Considering Evidence from Human and Veterinary Medicine.

Macrolide antimicrobial agents have been in clinical use for more than 60 years in both human and veterinary medicine. The discovery of the non-antimicrobial properties of macrolides and the effect of immunomodulation of the inflammatory response has benefited patients with chronic airway diseases and impacted morbidity and mortality. This review examines the evidence of antimicrobial and non-antimicrobial properties of macrolides in human and veterinary medicine with a focus toward veterinary macrolides but including important and relevant evidence from the human literature. The complete story for these complex and important molecules is continuing to be written.

In Vitro Killing of Canine Urinary Tract Infection Pathogens by Ampicillin, Cephalexin, Marbofloxacin, Pradofloxacin, and Trimethoprim/Sulfamethoxazole.

Urinary tract infections are common in dogs, necessitating antimicrobial therapy. We determined the speed and extent of in vitro killing of canine urinary tract infection pathogens by five antimicrobial agents (ampicillin, cephalexin, marbofloxacin, pradofloxacin, and trimethoprim/sulfamethoxazole) following the first 3 h of drug exposure. Minimum inhibitory and mutant prevention drug concentrations were determined for each strain. In vitro killing was determined by exposing bacteria to clinically relevant drug concentrations and recording the log10 reduction and percent kill in viable cells at timed intervals. Marbofloxacin and pradofloxacin killed more bacterial cells, and faster than other agents, depending on the time of sampling and drug concentration. Significant differences were seen between drugs for killing Escherichia coli, Proteus mirabilis, Enterococcus faecalis, and Staphylococcus pseudintermedius strains. At the maximum urine drug concentrations, significantly more E. coli cells were killed by marbofloxacin than by ampicillin (p < 0.0001), cephalexin (p < 0.0001), and TMP/SMX (p < 0.0001) and by pradofloxacin than by cephalexin (p < 0.0001) and TMP/SMX (p < 0.0001), following 5 min of drug exposure. Rapid killing of bacteria should inform thinking on drug selection for short course therapy for uncomplicated UTIs, without compromising patient care, and is consistent with appropriate antimicrobial use and stewardship principles.

Characterization of Polybacterial versus Monobacterial Conjunctivitis Infections in Pediatric Subjects Across Multiple Studies and Microbiological Outcomes with Besifloxacin Ophthalmic Suspension 0.6.

INTRODUCTION: The choice of empiric therapy for bacterial conjunctivitis should be guided by an awareness of typical causative pathogen distributions. Bacterial conjunctivitis can be polybacterial, although pediatric-specific data are lacking. METHODS: This was a post-hoc analysis of data in pediatric subjects (1-17 years) from five bacterial conjunctivitis trials evaluating besifloxacin ophthalmic solution 0.6%. RESULTS: Of the 730 pediatric subjects with culture-confirmed conjunctivitis, nearly one-fourth (23.6%) had polybacterial infections and three-fourths (76.4%) had monobacterial infections at baseline. In both polybacterial and monobacterial infections, the most prevalent organisms were Haemophilus influenzae, Streptococcus pneumoniae, Staphylococcus aureus, and Streptococcus mitis/S. mitis group. In polybacterial versus monobacterial infections, S. mitis/S. mitis group (8.7% vs 4.3%; P=0.032) and Moraxella catarrhalis (4.7% vs 0.5%; P<0.001) were identified more frequently, whereas S. pneumoniae (14.0% vs 28.1%; P<0.001) was identified less frequently, as the dominant infecting species. MICs for individual species were similar for tested antibiotics regardless of polybacterial or monobacterial infection, except Staphylococcus epidermidis for which fluoroquinolone MICs were ≥3 dilutions higher for isolates of this species sourced from polybacterial compared to monobacterial infections. Treatment with besifloxacin resulted in microbial eradication in 79.1% of polybacterial and 92.3% of monobacterial infections (P≤0.005 vs vehicle). DISCUSSION: One in four pediatric bacterial conjunctivitis infections is polybacterial, highlighting the need for a broad-spectrum antibiotic when choosing empiric therapy.

Recovery of borderline oxacillin-resistant Staphylococcus pseudintermedius (BORSP) from bone and soft tissue of a rheumatoid arthritis patient with severe osteoporosis: transmission from the family dog.

We report a case of borderline oxacillin-resistant S. pseudintermedius (BORSP) in a rheumatoid arthritis patient with severe osteoporosis. The organism is also resistant to erythromycin and clindamycin. We also present clear evidence on transmission from the family dog.

A case of multifocal cutaneous alternariosis in a patient with hairy cell leukemia.

We present a case of multifocal cutaneous alternariosis in a 69-year-old man with hairy cell leukemia. The patient presented with painful, violaceous nodules of the lower extremities and left forearm. His physical examination was otherwise normal. Biopsy specimens were submitted first for histopathological examination, followed by microbiological testing. Histopathology showed epidermal hyperplasia, intraepidermal abscess formation, and intracellular and extracellular fungal elements. Subsequent microbiological investigations, including fungal culture and polymerase chain reaction (PCR), isolated Alternaria alternata. The patient was treated for cutaneous alternariosis with itraconazole for 12 weeks and demonstrated significant improvement of the lesions. This case highlights the role of dual histopathological and microbiological laboratory investigation in suspected opportunistic cutaneous mycoses.

Les chercheurs présentent un cas d'alternariose cutanée multifocale chez un homme de 69 ans atteint d'une leucémie à tricholeucocytes. Le patient a consulté à cause de nodules violacés et douloureux sur les extrémités inférieures et l'avant-bras gauche. Son examen physique était autrement normal. Des biopsies ont été d'abord soumises en vue d'un examen histopathologique, puis de tests microbiologiques. L'histopathologie a révélé une hyperplasie épidermique, la formation d'abcès épidermiques et des éléments fongiques intracellulaires et extracellulaires. Les explorations microbiologiques subséquentes, y compris les cultures fongiques et l'amplification en chaîne par polymérase, ont isolé l'Alternaria alternata. Le patient a reçu un traitement de 12 semaines à l'itraconazole pour vaincre une alternariose cutanée, et ses lésions ont considérablement diminué. Ce cas souligne l'intérêt de conjuguer l'exploration histopathologique à l'exploration microbiologique dans les cas présumés de mycose opportuniste.

Characterization of baseline polybacterial versus monobacterial infections in three randomized controlled bacterial conjunctivitis trials and microbial outcomes with besifloxacin ophthalmic suspension 0.6.

BACKGROUND/PURPOSE: To date, studies examining polymicrobial infections in ocular disease have mostly been limited to keratitis or endophthalmitis. We characterized polybacterial infections compared to monobacterial infections in prior clinical studies evaluating besifloxacin ophthalmic suspension 0.6% for the treatment of bacterial conjunctivitis and report on associated microbiological outcomes. METHODS: In this post-hoc analysis, microbiological data for subjects with conjunctivitis due to one or more than one bacterial species in three previous studies (two vehicle-, one active-controlled) of besifloxacin were extracted. Bacterial species identified at baseline were deemed causative if their colony count equaled or exceeded species-specific prespecified threshold criteria. In subjects with polybacterial infections, the fold-increase over threshold was used to rank order the contribution of individual species. Baseline pathogens and their minimum inhibitory concentrations (MICs) for common ophthalmic antibiotics were compared by infection type, as were microbial eradication rates following treatment with besifloxacin. RESULTS: Of 1041 subjects with culture-confirmed conjunctivitis, 17% had polybacterial and 83% had monobacterial conjunctivitis at baseline. In polybacterial compared to monobacterial infections, Haemophilus influenzae and Streptococcus pneumoniae were identified less frequently as the dominant infecting species (P = 0.042 and P<0.001, respectively), whereas Streptococcus mitis/S. mitis group was identified more frequently as dominant (P<0.001). Viral coinfection was also identified more frequently in polybacterial infections (P<0.001). Staphylococcus aureus was the most common coinfecting species in polybacterial infections and the second most common dominant species in such infections. With few exceptions, MICs for individual species were comparable regardless of infection type. Clinical microbial eradication rates with besifloxacin were high regardless of infection type (P≤0.016 vs vehicle at follow-up visits). CONCLUSIONS: Approximately one in five subjects with bacterial conjunctivitis are infected with more than one bacterial species underscoring the need for a broad-spectrum antibiotic for such infections. Besifloxacin treatment resulted in robust eradication rates of these infections comparable to monobacterial infections. TRIAL REGISTRATION: NCT000622908, NCT00347932, NCT00348348.