Robert L. Marier

Comparison of the activities of penicillin G and new beta-lactam antibiotics against clinical isolates of Bacteroides species.

MICs were determined for 218 clinical isolates of Bacteroides by a broth microdilution method. Imipenem was the most active antibiotic tested. Azlocillin, mezlocillin, and cefoxitin had comparable activities, with resistance among members of the B. fragilis group and B. capillosus. Ceftizoxime was the most active cephalosporin tested. Members of the B. fragilis group showed high levels of resistance to cefotetan and ceftazidime. Resistance to penicillin G varied from 0 to 14%.

Single-dose cefaclor therapy of urinary tract infection: Evaluation of antibody-coated bacteria test and C-reactive protein assay as predictors of cure

The efficacy of single-dose (cefaclor, 2 g orally) and multidose (cefaclor, 250 mg orally three times a day for 10 days) antibiotic regimens in the therapy of acute uncomplicated urinary tract infections (UTI) in nonpregnant women were compared. The patients clinical status and results of urine cultures were compared in retrospect with the results of the antibody-coated bacteria (ACB) test and C-reactive protein (CRP) test in order to determine if either test would predict the patients response. Overall, 10 of 30 patients (33 percent) and 18 of 22 patients (81 percent) given single doses and multidoses, respectively, had negative urine cultures four weeks after completion of therapy. A negative urine culture at four weeks correlated with a negative ACB test utilizing the less inclusive criteria for negativity (less than 5 bacteria with fluorescence in 5 minutes of search) but not with a negative ACB test utilizing the more inclusive criteria (less than 10 percent bacteria with fluorescence) or with a negative CRP test. The cure rate in the ACB-negative single-dose group (7 of 9 patients) utilizing the less inclusive criteria for negativity was similar to the cure rate in the ACB-negative multidose group (8 of 10 patients). This study suggests that the ACB test, if properly standardized, might permit identification of a population of patients with UTI who would respond to single-dose cefaclor therapy.

Cefamandole and Cefoxitin

Cefamandole and cefoxitin, introduced only 7 years ago, are now the most commonly prescribed parenteral antibiotics in the United States. These drugs are similar to the first-generation cephalosporins in toxicity, but their in-vitro spectrum of activity is greater. Their serum half-lives are longer than those of cephalothin and cephapirin but shorter than that of cefazolin. Although cefamandole has been recommended in empiric therapy for patients with community-acquired pneumonia and as a prophylactic agent for patients having various surgical procedures, other regimens are less expensive and just as effective. Cefamandole should not be used to treat intra-abdominal, enterobacter, or ampicillin-resistant Haemophilus influenzae infections. Cefoxitin is effective in the treatment and prevention of mixed aerobic-anaerobic skin and soft-tissue, intra-abdominal, gynecologic, and penicillinase-producing, spectinomycin-resistant Neisseria gonorrhoeae infections. Cefoxitin represents a greater advance than cefamandole in our continuing search for safe and more effective antimicrobial agents.

SUSCEPTIBILITY OF ANAEROBIC BACTERIA TO BETA-LACTAM ANTIBIOTICS AND BETA-LACTAMASE PRODUCTION

We examined the susceptibility of various anaerobes to four beta-lactamase susceptible (ampicillin, amoxycillin, cyclacillin, and penicillin G) and two beta-lactamase resistant (moxalactam, and N-F-thienamycin) beta-lactam antibiotics and measured beta-lactamase production. Members of the Bacteroides groups were most resistant to the six antibiotics. N-F-thienamycin was the most effective antimicrobial agent against all the test strains, moxalactam the next most effective, and penicillin G the least. Beta-lactamase production was mainly confined to Bacteroides species. Cephalosporinase was the most common beta-lactamase produced; penicillinase was detected less often. About two thirds of the penicillin-resistant isolates produced cephalosporinase. N-F-thienamycin and moxalactam were the most active agents against those anaerobes that were resistant to many beta-lactam antibiotics.

A ventilation-filtration unit for respiratory isolation.

OBJECTIVE The development of a new method for achieving respiratory isolation in hospitals, clinics, and residential facilities, in response to the increasing risk of transmission of tuberculosis and the limitations of the currently available isolation systems. DESIGN Ultraviolet (UV) light and ultra-low-penetration air filtration were combined with a ventilation unit and adapted for use in modular isolation rooms or for conversion of existing rooms. RESULTS The ventilation-filtration unit efficiently cleared bacterial aerosols and particles > 0.2 microns from the air, maintained required negative pressures and airflows, and provided directional airflow within rooms.

Moxalactam in the therapy of serious infections.

Sixty-seven patients were treated with moxalactam in a noncomparative trial of hospitalized patients; 32 had endometritis or chorioamnionitis, 12 had skin and soft tissue infections, 5 had osteomyelitis, 5 had pneumonia, 5 had urinary tract infections, 4 had arthritis, 2 had sepsis from an unknown source, 1 had endocarditis, and 1 had peritonitis. Bacteremia was present in 12 of these patients. Patients were given 3 to 12 g of moxalactam per day (mean, 6.24 g/day) in divided doses every 6 to 8 h. Seven patients were given intramuscular treatment for 3 to 20 days for part or all of their therapy. The rest were given intravenous treatment exclusively. Treatment was continued for 2 to 42 days (mean, 10 days). The dose and the duration of therapy were determined by the type of infection and the response of each patient. There were four treatment failures and one enterococcal-clostridial superinfection. Moxalactam was well tolerated. Allergic reactions led to the discontinuation of the antibiotic in three patients. Prolonged prothrombin and partial thromboplastin times were observed in 2 of 11 patients tested; in both instances in patients had severe underlying diseases, including malnutrition and alcoholism. Pain on intramuscular injection was noted in two patients receiving 1,500 mg, but not in five receiving a lower dose; in one case the pain forced the use of intravenous therapy after one dose, and in the other case the pain was mild and the patient was treated for 20 days. We concluded that moxalactam was effective in the treatment of the types of infections included in this study and produced few adverse reactions.

Role of imipenem/cilastatin in the treatment of soft tissue infections

Imipenem/cilastatin was given to 243 evaluable patients with moderately severe to severe soft tissue infections. Cultures prior to therapy yielded Staphylococcus aureus (108 isolates), group D and non-group D enterococci (49), group A streptococci (42), other aerobic gram-positive cocci (72), Pseudomonas aeruginosa (54), Escherichia coli (32), Proteus mirabilis (31), Enterobacter (21), Klebsiella (20), other aerobic gram-negative rods (58), Bacteroides fragilis group (16), and other anaerobes (65). Overall, 95 percent (230 of 243) of the patients treated had clinical cure (137 of 243) or improvement (93 of 243). Of the 506 strains of etiologic bacterial pathogens isolated from these patients and tested against imipenem, 498 (98 percent) were susceptible to the antibiotic. Many were resistant to both older and newer penicillins and cephalosporins. Serial cultures of infection sites revealed that 426 of 498 (86 percent) of pre-therapy bacterial isolates were eradicated by imipenem/cilastatin therapy. Eight of 498 etiologic pathogens (1.6 percent) acquired resistance to imipenem (seven P. aeruginosa and one enterococcus). Such resistance acquisition was associated with clinical failure in two patients. Imipenem/cilastatin appears to be a highly effective, relatively safe therapy of soft tissue infections caused by a wide variety of gram-positive and gram-negative aerobes and anaerobes, both polymicrobial and monomicrobial in nature. Imipenem/cilastatin should be considered particularly when infection by the more antibiotic-resistant of these bacteria is suspected or proved.

N-formimidoyl thienamycin (MK0787): in vitro activity against anaerobic bacteria.

The in vitro activity of N-formimidoyl thienamycin (MK0787) was tested against 239 anaerobic bacteria clinical isolates: 70 of Bacteroides fragilis, 18 of B. distasonis, 16 of B. thetaiotaomicron, 10 of B. vulgatus, 24 of Bacteroides spp., 22 of B. melaninogenicus (all three subspecies), 26 of Fusobacterium spp., 10 of Peptococcus spp., 15 of Peptostreptococcus spp., 15 of Clostridium perfringens, and 13 of Clostridium spp. Ninety-five percent of the isolates were inhibited by less than or equal to 0.125 microgram/ml, and all were inhibited by less than or equal to 4 micrograms/ml.

The Design of Isolation Rooms

In their study of ventilation efficiency in the design of protective isolation rooms, Marshall et al have demonstrated that effective distribution of air in ventilated rooms is critical to the control of airborne contamination. The methods used are elegant and will provide engineers and others involved in the design of protective isolation rooms with improved methods for design of environments that are intrinsically safer. The approach, as suggested by the authors, might well be extended to other applications in hospitals and to other environments in the hospital or elsewhere wherever protection of people from airborne pathogens is a concern.2 The use of inert tracer gases to investigate the performance of ventilation systems is well established and may be used to measure overall ventilation rates and distribution (mixing) of air in occupied buildings.3 In one method, a quantity of tracer (inert gas) is injected into a volume of air (building) and allowed to mix. The ventilation rate (I) in air changes per hour (ACH) is given by the following equations where “t” is time (h), Co is initial concentration of tracer, C, is final concentration of tracer, Q, is the ventilation or airflow rate (CF/h), and V is the volume of the space being measured.3