Prevalence and antibiotic resistance of mastitis pathogens isolated from dairy herds transitioning to organic management

Changes in udder health and antibiotic resistance of mastitis pathogens isolated from dairies upon conversion from conventional to organic management over a 3-year period was studied. Coagulase-negative staphylococci (CNS) were the most prevalent mastitis pathogens isolated. CNS were significantly less resistant to beta-lactam antibiotics when isolated from milk after the herd transitioned to organic management. Cessation of the use of antimicrobial therapies in dairies in combination with organic management could lead to a reduction in the antimicrobial resistance of mastitis pathogens.

Comparison of susceptibility testing methods for the detection of methicillin/oxacillin resistance in Staphylococcus aureus

To compare the accuracy of disk diffusion method and E-test for the detection of methicillin resistance and low-level methicillin-resistance in Staphylococcus aureus [S. aureus] and the PBP2a latex agglutination test for confirmation. A total of 76 methicillin resistant S. aureus [MRSA] isolates from different clinical specimens were tested by disk diffusion method. Disk d i ffusion method was performed using methicillin [MET] 5microg disk, oxacillin [OX] 1 microg disk, moxalactam [MOX], and cefoxitin [FOX] 30 microg each on Mueller Hinton agar [MHA] plates supplemented with 2% NaCl and incubated at 35 °C for 24 hours. Minimum inhibitory concentration [MIC] was performed by E-test for MET and OX on MHA plates containing 2% NaCl. Results for all tests were read according to NCCLS recommendations for zone of inhibition and break points. Low-level MRSA strains were confirmed by PBP2a latex agglutination test. All strains were tested for ?-lactamase production. All MRSA strains were detected by disk diffusion methods using MET, OX and FOX [100%]. Four [5.2%] strains were low-level MRSA by MOX disk. E-test detected 72 [94.7%] using MET and 74 [97.3%] MRSA strains using OX. No heterogeneous growth within the zones of inhibitions was noticed. One MRSA was misclassified as methicillin sensitive by MET E-test [MIC 6 microg /ml], but was 32 microg/ml by OX E-test. Two strains were low-level MRSA by E-tests but showed resistance by MET, OX and FOX disk diffusion method. One strain had MIC of 12 microg/ml both by OX and MET E-tests. All four strains showed low-level resistance by MOX disk and were positive for PBP2a latex agglutination test. All the strains produced ?-lactamase. Conclusion: Disk diffusion method using MET, OX, and FOX can reliably be used to detect methicillin resistance in S. aureus. MOX and E-test can be used to detect lowlevel methicillin resistance and these can further be confirmed by PBP2a latex agglutination test in diagnostic laboratories

Septicemia neonatal: incidencia, letalidad y características bacteriológicas: comparación de dos períodos / Neonatal septicemia: incidence, mortality and microbiological findings along 2 different periods

Objetivos: describir y comparar la incidencia y letalidad de la septicemia neonatal, en dos períodos en un hospital universitario. Pacientes y método: se compararon recién nacidos que tuvieron septicemia entre los meses de julio de 1987 a junio de 1989 con los del período de enero de 1995 a diciembre de 1996. Resultados: la incidencia de septicemia neonatal aumentó (2,9 a 8,7 por mil) y la letalidad (44 por ciento a 2,2 por ciento) disminuyó en el segundo período. Las poblaciones estudiadas y los métodos de diagnóstico fueron similares. En las septicemias connatales el germen preponderante fue el Streptococcus grupo B sin diferencias entre períodos (50 por ciento ante 52 por ciento). Entre las septicemias nosocomiales, aumentaron las producidas por estafilococo (desde 25 por ciento a 91 por ciento), siendo Staphylococcus epidermidis devino el principal agente durante el segundo período (57 por ciento del total), disminuyendo la sensibilidad a cloxacilina (100 por ciento a 33 por ciento). Conclusiones: se demuestra un aumento de la incidencia y mejoría del pronóstico de las septicemias neonatales con un cambio en sus características bacteriológicas entre los períodos estudiados, similar a lo observado en otros países

Warfarin resistance in a patient with prosthetic valve endocarditis treated with cloxacillin

Systemic anticoagulation with warfarin is the mainstay therapy for patients with valve prosthesis. Such drug therapy is of crucial importance in patients with prosthetic valve endocarditis [PVE] because of higher incidence of thrombo-embolism. We are reporting a case of PYE where the patient developed warfarin resistance due to Cloxacillin administration in spite of concomitant administration of I.V. Heparin. Warfarin dose was increased from a baseline of 5 mg daily before Cloxacillin was started to 30 mg daily during Cloxacillin treatment. Six weeks after completion and discontinuing the antibiotic course, the patient's International Normalized ratio [INR] value gradually increased and Warfarin dose was tapered down over eight days. Cloxacillin-Warfarin interaction seems to be due to rapid metabolism in susceptible subjects leading to a reduction in the hypoprothombinemic effect of warfarin. Our finding is consistent with the reported cases which documented such interaction with other members of Penicillinase-resistant Penicillins such as NafcilIin and Dicloxacillin