Adaptation of methicillin-resistant Staphylococcus aureus during antibiotic therapy.

Colonization of a patient by methicillin-resistant Staphylococcus aureus (MRSA) of a single phage-type for over four years is described. During this period we observed the appearance and disappearance of resistance to erythromycin, clindamycin, gentamicin, kanamycin, tobramycin, neomycin and mupirocin. We also saw stepwise increases in methicillin resistance and reversible changes in physical appearance and the colonizer pathogen role. Correlation of clinical observations, details of antibiotic therapy and laboratory studies demonstrated that adaptation of MRSA during antibiotic therapy favoured MRSA establishment and predominance.

Cephalosporin susceptibility of methicillin-resistant, coagulase-negative staphylococci.

Coagulase-negative staphylococci were tested for susceptibility to methicillin, cephradine, ceftriaxone, cephalothin, and cefamandole by standard broth microdilution. Most of the 26 methicillin-resistant isolates were susceptible to cephalothin and cefamandole, but very few were susceptible to ceftriaxone, and none was susceptible to cephradine. The proportion of bacterial cells that grew in the presence of 128 micrograms of methicillin per ml was calculated for each methicillin-resistant isolate. Those with every cell or 1 in 10 cells resistant to 128 micrograms of methicillin per ml included the isolates that were most resistant to the cephalosporins and highly resistant to methicillin. Those with 1 cell resistant in 10(5) or 10(6) cells were the isolates most susceptible to the cephalosporins, and their methicillin MICs were lower. When cells resistant to 128 micrograms of methicillin per ml were used as inocula for broth microdilution tests, resistance to cephradine remained the same, but resistance to ceftriaxone, cephalothin, and cefamandole increased significantly. Cefamandole was the only cephalosporin which retained antibacterial activity against some methicillin-resistant isolates (12 of 26). Cephradine, ceftriaxone, cephalothin, and cefamandole resistance appeared to be expressed by the same cells that expressed methicillin resistance. In this way, cross resistance was demonstrated between methicillin and the cephalosporins.

Blood culture isolates at Green Lane Hospital, 1972-1982.

Bacteraemic patients identified annually at Green Lane Hospital by positive blood culture increased by 215% between 1972 and 1982. In the same period the patient population increased by 22%. There was a disproportionate increase in gram-positive organisms. Antibiotic sensitivity patterns are discussed.

In-vitro activity of cefoxitin against recent clinical bacterial isolates.

The susceptibility of 635 clinical isolates of bacteria to cefoxitin was determined. Isolates from the urinary tract showed 97% sensitivity, isolates from infected wounds showed 93% sensitivity and 82% of blood culture isolates were sensitive. Streptococcus faecalis isolates showed only 50% sensitivity and pseudomonas organisms were predominantly resistant. Bacteria isolated from unprepared heart valves submitted for use as homografts showed only 71% sensitivity due to the large proportion of Streptococcus and Pseudomonas species isolated.

Endocarditis due to Citrobacter diversus developing resistance to cephalothin.

A 43-year-old man was admitted with acute bacterial endocarditis. Citrobacter diversus susceptible to cephalothin was isolated from blood cultures. Citrobacter diversus was later isolated from the aortic valve cusps at surgery, but this isolate was resistant to cephalothin. Laboratory testing showed that the Citrobacter diversus recovered from blood cultures was capable of producing mutants highly resistant to cephalothin.

Onychomycosis due to Aspergillus candidus: case report.

A patient is described who suffered from chronic fungal involvement of right great toe nail. Serial cultures of the removed nail demonstrated a non-dermatophyte, Aspergillus candidus, as the causative agent.

In vitro resistance of haemophilus influenzae to co-trimoxazole and trimethoprim.

Over a period of five months Haemophilus influenzae isolated from 123 patients were tested for resistance to co-trimoxazole and trimethoprim by the disc method of sensitivity testing and isolates from four patients were found to be resistant. However, the minimum inhibitory concentrations of trimethoprim lactate were estimated for the isolates from these four patients only one was found to be resistant. This H. influenzae strain was from one of the two patients in the survey who had a history of repeated courses of co-trimoxazole therapy. The discrepancy between the results of the disc sensitivity tests and the minimum inhibitory concentration estimations of the resistance of H. influenzae to co-trimoxazole and trimethoprim. The appearance of co-trimoxazole and trimethoprim resistance in H. influenzae isolated from a patient who has had prolonged treatment with co-trimoxazole is in agreement with the findings of other authors.

Torulopsis glabrata endocarditis complicating aortic homograft valve treated with 5-fluorocytosine: case report with discussion of antifungal chemotherapy.

A case of Torulopsis glabrata endocarditis occurring in a patient 14 months after aortic homograft valve replacement is reported. The infection was not controlled by amphotericin B which led to progressive renal impairment. Re-operation was delayed by the development of multiple infarctions due to coronary emboli. The infection was subsequently eradicated by oral treatment with the newer antifungal agent, 5-fluorocytosine, but death of the patient eventually occurred from an arrhythmia related to the persisting myocardial failure consequent upon episodes of transmural infarction. Current evidence favours the use of early re-operation in all cases of endocarditis in addition to aggressive chemotherapy with a combined regime of amphotericin B and 5-fluorocytosine. Clinical pharmacology of 5-fluorocytosine is briefly discussed.