Chlamydia pneumoniae is emerging as a significant cause of respiratory disease, including pneumonia and bronchitis, in humans. In this recently completed study of infection due to C. pneumoniae in patients presenting with pneumonia to SUNY Health Science Center at Brooklyn, we identified two individuals for whom cultures were positive on multiple occasions over a 1-year period. To determine the frequency of persistent respiratory infection with C. pneumoniae, follow-up specimens were obtained from nine individuals with culture-documented C. pneumoniae infection. Five of these individuals had persistent infection: four had a flulike illness characterized by pharyngitis, and one had bronchitis with prominent bronchospasm. All five individuals appeared to have acute C. pneumoniae infection as determined by results of serologic tests (titers of IgM antibody for all individuals were greater than or equal to 1:16). For three patients, cultures remained positive for 11 months despite therapy with 10- to 21-day courses of tetracycline or doxycycline. These observations suggest that persistent infection with C. pneumoniae may follow acute infection and may persist for many months. Infection with C. pneumoniae may be very difficult to eradicate with use of currently available antibiotics even if there is a clinical response to therapy.

At pH 5.0, the electrical potential (A', interior negative) across the plasma membrane of Staphylococcus aureus exhibits a minimum of -85 to -90 mV; the pH gradient (ApH, interior alkaline) across the membrane approximates a maximum of about -100 mV. Under these conditions, uptake of the aminoglycoside gentamicin is negligible, and viability of the organism is not impaired by the antibiotic. In contrast, at pH 7.5, at which At is about -130 mV and ApH is 0, gentamicin uptake is observed and the drug markedly decreases viability. Dramatically, when the ionophore nigericin is added at pH 5.0,.gentamicin uptake is induced, there is a striding decrease in viability, and. the effect is associated with an increase inAl' at the expense ofApH. Consistently, valinomycin, which dissipates A' in the presence ofpotassium, abolishes gentamicin uptake andkilling. In addition, from pH 5.0 to pH 7.5, there is a direct relationship between the magnitude ofAl and both gentamicin.uptake and its bactericidal effect. However, a threshold A' of -75 to -90 mV is apparently necessary to initiate uptake and killing. These observations provide a strong indication that Al plays a critical role in the uptake and antibacterial action of gentamicin and. suggest that nigericinlike ionophores may be clinically useful in synergy with aminoglycosides.The aminoglycoside antibiotics (e.g., streptomycin and gentamicin) are transported across the bacterial cytoplasmic membrane prior to inhibition ofprotein synthesis, and there appears to be an association between antibiotic susceptibility and the rate and magnitude of drug accumulation (1-6, f). Although aminoglycoside uptake as described in Escherichia coli (1)(2)(3)(4)(5) and Staphylococcus aureus (6, f) is a complex phenomenon, the lethal effect of these antibiotics is associated with an aminoglycoside-induced accelerated phase of uptake. Mutations affecting ribosomal binding (4, 7, ), the bacterial respiratory chain, and the H+-ATPase (5) all abolish this rapid uptake phase. In addition, strains that produce plasmid-mediated aminoglycosidemodifying enzymes (8, 9) also exhibit defective drug accumulation.According to the chemiosmotic hypothesis (10, 11), proton extrusion during respiration or ATP hydrolysis leads to the generation of a transmembrane electrochemical gradient of hydrogen ions (Aj!H+)l that is the immediate driving force for many biological processes, and recent studies (6, h) suggest that A/.H+ may be important for aminoglycoside uptake. The proton electrochemical gradient is composed ofelectrical and chemical parameters according to the following relationship: AjiH+ = AT-ZApH [1] in which AT represents the electrical potential across the plasma membrane and ApH is the transmembrane difference in H' concentration (Z is equal to 58.8 at room temperature).With regard to active transport, the chemiosmotic hypothesis predicts that transport is driven by AT (interior negative) for cationic substrates, by ApH (interior alkaline) for anionic substrates, and by A-gH+ for neutral s...

The results suggest that prior administration of vancomycin, especially in the patient who develops nosocomial infection, can influence the acquisition of vancomycin-resistant enterococci and that VAREC may be transmitted from patient to patient. Using a modification of the standard infection control practice of isolation, we were able to control the spread of this resistant strain of E faecium.

Gentamicin uptake and killing were studied in aminoglycoside-susceptible wildtype Staphylococcus aureus strains and aminoglycoside-resistant small-colony mutants selected by gentamicin from these strains. In wild-type S. aureus three phases of gentamicin accumulation were noted, and killing occurred during the last and most rapid phase of uptake. Uptake and killing were abolished by anaerobic growth and sodium azide, suggesting that energy-dependent active drug transport required respiration. Treatment ofwild-type strains with the uncouplers N,N'-dicyclohexyl carbodiimide (DCCD) and carbonyl cyanide-m-chlorophenyl hydrazone showed disparate effects on gentamicin uptake, producing enhanced and diminished accumulations, respectively. Small-colony mutants demonstrated markedly deficient uptake compared with the wild-type strains and were not killed by gentamicin in concentrations up to 10 ,Lg/ml. Several classes of aminoglycoside-resistant mutant strains are described. One mutant strain was a menadione auxotroph which, when grown in the presence of menadione, exhibited normal gentamicin uptake and killing. Gentamicin uptake and killing in this strain were abolished by KCN (21,24). The decreased susceptibilities to a wide variety of aminoglycosides observed in these mutant strains suggest a more general mechanism of resistance than specific enzymatic modification or altered ribosomal binding of particular aminoglycosides. In view of data indicating that similar small-colony variants of S. aureus have impairments in oxidative processes (19,20) and the demonstration that oxidatively generated energy is required for aminoglycoside uptake in gram-negative bacilli (4-6), we were interested in studying gentamicin accumulation and its relationship to oxidative metabolism in wild-type and aminoglycoside-resistant small-colony mutants of S. aureus.