Clinical trial of piperacillin with acquisition of resistance by Pseudomonas and clinical relapse

Five-year surveillance and correlation of antibiotic consumption and resistance of Gram-negative bacteria at an intensive care unit in Serbia

A surveillance study was performed in an intensive care unit in the largest tertiary health care center in Vojvodina, Serbia from 2014 to 2018. Antibiotic prescription data were collated in the WHO anatomical therapeutic chemical (ATC)/defined daily dose (DDD) format, while antibiotic resistance was expressed as incidence density adjusted for total inpatient-days. Individual trends were determined by linear regression, while possible associations between antibiotic prescription and resistance were evaluated using cross-correlation analysis. An overall decrease in antibiotic utilization was observed. The prescription rates of piperacillin-tazobactam increased significantly, while consumption of 3rd and 4th generation cephalosporins and fluoroquinolones decreased. There were rising incidence densities of doripenem resistant Acinetobacter spp., piperacillin-tazobactam resistant Pseudomonas aeruginosa and carbapenem and colistin resistant Klebsiella pneumoniae. These results can serve as a basis for the development of antimicrobial stewardship strategies in the current setting.

Bacteriology of the burn wound at the Bai Jerbai Wadia hospital for children, Mumbai, India-A 21 year study of predominant Pseudomonas species

This study aims to assess the change in the antibiotic sensitivity pattern of Pseudomonas species with time. Microbiological data of 2399 patients admitted to the burns unit of the Bai Jerbai Wadia Hospital for Children, Mumbai over a period of 21 years (1994-2014) was reviewed. The age group of patients admitted to our facility ranged from one month to fifteen years. A total of 11,402 burn wound swabs were cultured and 17507 isolates were tested for their antibiotic sensitivity. Pseudomonas was found to be 31.8% of the total number of isolates found on the burn wound which is second in line to Klebsiella species at our unit. It was found that the sensitivity of Pseudomonas species to various antibiotics tested has been restricted to very few antibiotics. The organism out plays most of the antibiotics that it is subjected to in vitro. Our efforts should now be channelized towards limiting the use of antibiotics. We must focus on preparing proper antibiotic policy which exercises control of irrelevant and excessive use of antibiotics. It should also be noted that every treatment facility has microorganisms unique to it and these change with time. It is, therefore of paramount importance to have an in-depth knowledge of the resident organisms and their antibiotic sensitivity. This will not only help to control infection related morbidity and mortality but will also curb the growing resistance to antibiotics.

Burn Wound Sepsis

Wound sepsis remains perhaps the most feared sequela in the patient who has suffered major burn injuries and leads to overwhelming mortality among patients with extensive burn wounds. The presence of large areas of devitalized, necrotic tissue, coupled with the profound immunosuppression that usually follows major injury, sets the stage for rapid microbial proliferation in the wound; when microbes invade subjacent, previously vi able tissues, invasive burn wound sepsis is defined. Top ical antimicrobial drugs probably have only a limited effect in preventing wound sepsis, and organisms now frequently emerge that are resistant to the commonly used topical agents. Salient factors in the diagnosis and treatment of invasive wound sepsis are discussed in this review. Prevention of wound sepsis, however, is one of the primary objectives of current burn care. Early burn wound excision and immediate wound closure with autograft or a suitable biologic dressing has emerged as the best means for prevention of generalized wound sepsis.

Antibiotic use in Cystic Fibrosis

Chronic pulmonary infections contribute significantly to the morbidity and mortality of patients with CF. The primary pathogens are Pseudomonas aeruginosa (PA) and Staphylococcus aureus. Hemophilus influenzae has been isolated from a significant number of patients also. A number of the β-lactam and aminoglycoside antibiotics reportedly have altered pharmacokinetic variables in CF. Therapy of acute pulmonary deterioration consists of intravenous antibiotics for two weeks. Antibiotic selection is based on culture and sensitivity results. Currently, the combination of a broad-spectrum penicillin and an aminoglycoside seems to provide the best results. Prophylactic antibiotics are effective if the primary isolates are sensitive to the agents used. Chronic PA infections are problematic because effective oral agents are not available. Aerosolized antibiotics do not improve results over adequate systemic therapy for acute exacerbations. Questions regarding optimal dosages, frequency, and duration of therapy remain.

Pseudomonas infections in the thermally injured patient

Pseudomonas aeruginosa, remains a serious cause of infection and septic mortality in burn patients, particularly when nosocomially acquired. A prototypic burn patient who developed serious nosocomially acquired Pseudomonas infection is described as an index case which initiated investigations and measures taken to identify the source of the infection. The effect of changes in wound care to avoid further nosocomial infections was measured to provide data on outcome and cost of care. The bacteriology of Pseudomonas is reviewed to increase the burn care providers understanding of the behaviour of this very common and serious pathogen in the burn care setting, before reviewing the approach to detection of the organism and treatment both medically and surgically. After controlling the nosocomial spread of Pseudomonas in our burn unit, we investigated the morbidity and mortality associated with nosocomial infection with an aminoglycoside resistant Pseudomonas and the associated costs compared to a group of case-matched control patients with similar severity of burn injury, that did not acquire resistant Pseudomonas during hospitalization at our institution. We found a significant increase in the mortality rate in the Pseudomonas group compared to controls. The morbidity in terms of length of stay, ventilator days, number of surgical procedures, and the amount of blood products used were all significantly higher in the Pseudomonas group compared to controls. Costs associated with antibiotic requirements were also significantly higher in the Pseudomonas group. Despite this increased resource consumption necessary to treat Pseudomonas infections, these efforts did not prevent significantly higher mortality rates when compared to control patients who avoided infection with the resistant organism. Thus, in addition to the specific measures required to identify and treat nosocomial Pseudomonas infections in burn patients, prevention of infection through modification of treatment protocols together with continuous infection control measures to afford early identification and eradication of nosocomial Pseudomonas infection are critical for cost-effective, successful burn care.

Development of resistance during antibiotic therapy

The frequency of development of resistance during antibiotic therapy was evaluated by reviewing the literature according to prescribed criteria. Mean resistance rates were calculated to be 9.2% for broad spectrum penicillins, 8.6% for second and third generation cephalosporins, 10.0% for latamoxef, 4.7% for imipenem, 11.8% for ciprofloxacin and 13.4% for aminoglycosides. Emergence of resistance of the infecting organism was associated with therapeutic failure in about half of the cases with the exception of patients treated with aminoglycosides in whom development of resistance resulted in treatment failure in 85% of the cases. The possible benefit of combination therapy in terms of resistance development is discussed.

Clinical comparison of piperacillin and cefoxitin in patients with bacteriologically confirmed infections

The objective of this double-blind study was to compare the efficacy and safety of piperacillin with that of cefoxitin in patients with bacterial infections. Seventy hospitalized patients were treated with intravenous piperacillin (18 g/day) or cefoxitin (12 g/day) for a mean period of 11.5 days. Multiple serious underlying conditions were present in 91% of the patients in both treatment groups. The infection sites were the respiratory, urinary, and gastrointestinal tracts, the skin and skin structures, and the bones. Among the patients with evaluated courses of therapy, 87% (20 of 23) of the patients in the piperacillin-treated group and 90% (19 of 21) of the cefoxitin-treated patients were cured or improved. Multiple sites of infection were present in 6 patients given piperacillin and in 11 patients given cefoxitin. Gram-negative aerobic bacteria were the most frequently isolated organisms (56% of isolates). In each treatment group, 91% of the pathogens were eradicated. Three piperacillin-treated patients (9%) and four cefoxitin-treated patients (11%) had adverse clinical effects related to therapy; most of the effects were moderate in intensity. In conclusion, both piperacillin and cefoxitin were clinically safe and effective antibiotics for the treatment of these patients, most of whom had severe underlying conditions.

Emergence of resistance in gram-negative bacteria: a risk of broad-spectrum beta-lactam use

A number of new beta-lactam antibiotics have been developed to overcome bacterial resistance to older agents. Such resistance usually is caused by plasmid-mediated, constituently produced beta-lactamases. Second- and third-generation cephalosporins, ureidopenicillins, acylamino penicillins, and monobactams generally are resistant to hydrolysis by these enzymes. However, inducible beta-lactamases may confer resistance to these antibiotics. This induction may occur spontaneously or in response to cefoxitin or other beta-lactam agents. The mechanisms by which inducible enzymes produce this resistance are reviewed and implications for the prophylactic and therapeutic use of newer beta-lactams are considered.

Aminoglycoside resistance: a worldwide perspective

Two concerns, neither of which is particularly new, underlie the current reluctance to use aminoglycosides more broadly. First, an undeniable fact is that these compounds can be toxic, particularly in patients with impaired renal function or those receiving other nephrotoxic medications. Second, a more emotional concern is that widespread use of aminoglycosides, particularly the newer compounds that are more resistant to enzymatic inactivation, may engender widespread resistance. In fact, several sources lead one to doubt whether widespread use of potent and highly effective agents like amikacin will by itself increase a clinical reservoir of more resistant microbes. First, the surveillance studies undertaken in many hospitals show some modest reduction in overall aminoglycoside resistance even when a drug like amikacin is used to supplant antecedent compounds of the same class. Second, in institutions where no official surveillance programs have been undertaken but where ongoing surveillance has been maintained, susceptibility to amikacin has remained constant when recent blood isolates are compared with blood isolates from more than 10 years ago. Third, in controlled clinical trials, particularly in immunocompromised patients, the overall emergence of resistance has been remarkably low and contrasts rather strikingly with what has been observed in some monotherapeutic studies of beta-lactam agents. The presence of aminoglycoside-resistant strains cannot be denied, but the circumstances leading to the emergence of such resistance must be carefully assessed, particularly outside of the setting in which these drugs are used as first-line therapy for critically ill patients. For instance, there is substantial evidence to suggest that the topical use of aminoglycosides or the use of these agents when there may be environmental contamination could lead to the emergence of resistance. Before one incriminates the use of any one drug as predisposing to the emergence of resistance, one needs to have more information about the total exposure of a given bacterial population to aminoglycoside therapy. The emergence of resistance to aminoglycosides has been associated with exposure to the more commonly used agents such as gentamicin or tobramycin. With some of the newer beta-lactam agents, the rate of emergence of resistance, unlike that of the aminoglycosides, has appeared to be remarkably high. If the concern about emergence of resistance is genuine, and to maintain consistency of approaches, the infectious disease community should focus more attention on limiting or restricting the use of the more widely used beta-lactam compounds.(ABSTRACT TRUNCATED AT 400 WORDS)

Ciprofloxacin therapy of infections caused by Pseudomonas aeruginosa and other resistant bacteria

Ciprofloxacin was administered orally to 48 patients with 24 Pseudomonas aeruginosa infections and 13 other infections caused by cephalothin-resistant gram-negative bacilli. The types of infections treated included those of skin or skin structure, bone, urinary tract, and respiratory tract. In 83% of P. aeruginosa infections, a favorable clinical outcome occurred, compared with 85% for all infections. Failure to achieve a cure correlated with the emergence of resistant P. aeruginosa and Acinetobacter calcoaceticus strains in four instances and superinfection with Candida (two cases) and Streptococcus (two cases) species. Therapy was discontinued in three patients because of the development of nausea. Ciprofloxacin appears to be safe and effective in the therapy of infections caused by resistant gram-negative bacilli.

Role of amikacin in the management of intra-abdominal sepsis

Controversy has developed regarding the antibiotic management of intra-abdominal sepsis because of the recent availability of the third-generation cephalosporins and ureidopenicillins as alternatives to traditional combination therapy (aminoglycosides plus clindamycin). Most observers now acknowledge the need to provide anti-anaerobic as well as anti-aerobic gram-negative drug coverage. Although most of the newer agents do provide such broad-spectrum coverage, doubt remains regarding their efficacy because of flaws in comparative study design and the observation that resistance to the newer agents, which may even extend to the aminoglycosides, can emerge in individual patients during single courses of antibiotic therapy. Indeed, such resistance is most likely to occur during the treatment of seriously ill, immunodepressed patients who have undergone multiple reoperation for persistent or recurrent intra-abdominal sepsis--the precise group for which the new drugs were most desired as less toxic alternatives to the aminoglycosides. On the basis of such observations, combination therapy with the aminoglycosides, appears to remain the most logical choice. In the setting of nosocomial sepsis and pathogen resistance to other aminoglycosides, amikacin may be especially effective. Recent surveillance data indicate that the use of amikacin under such circumstances not only may provide effective antibiotic therapy, but also may actually reduce the level of microbial resistance to the other aminoglycosides. Past concern regarding the development of resistance to amikacin has probably been excessive and should not deter the use of this agent under appropriate clinical circumstances.

Penicillins with antipseudomonal activity

The escalating role ofPseudomonas aeruginosaas a nosocomial pathogen, the relatively high mortality rate associated with pseudomonal infections, the intrinsic antibiotic resistance of this versatile, ubiquitous organism, and the growing number of reports of multiple antibiotic resistance developing during therapy ofPseudomonasinfections prompt a review of currently available penicillins with antipseudomonal activity. Ticarcillin, piperacillin, mezlocillin and azlocillin have upstaged carbenicillin, the first antipseudomonal, β-lactam agent clinically used, with other products “in the wings.”

Antimicrobial combinations in the therapy of infections due to gram-negative bacilli

Antimicrobial combinations are used most frequently to provide broad-spectrum coverage; however, they are also frequently employed to enhance antimicrobial activity (synergism). Although there is extensive in vitro documentation of synergism for many antibiotic combinations, a clear advantage for these combinations has been difficult to demonstrate in clinical studies. Several types of combinations have been useful in clinical medicine and frequently result in synergism. These include combinations of a cell wall-active agent with an aminoglycosidic aminocyclitol, combinations of a beta-lactamase inhibitor with a beta-lactam, and combinations of agents that inhibit sequential steps in a metabolic pathway. Given its spectrum of activity, aztreonam will often be used with clindamycin or a beta-lactam antibiotic. Combinations of beta-lactams may be synergistic via several mechanisms. However, these combinations also exhibit significant potential for antagonism when used against gram-negative bacilli and, therefore, require careful evaluation prior to clinical use.

Treatment with aztreonam or tobramycin in critical care patients with nosocomial gram-negative pneumonia

During the course of one year, 47 critical care patients with gram-negative bacillary pneumonia at Millard Fillmore Hospital were randomly assigned to aztreonam or tobramycin therapy (two to one). Of these, 40 were fully evaluable for microbiologic and clinical response. All evaluable patients had gram-negative organisms in tracheal aspirate culture specimens and confirmed susceptibility of the organism to both study drugs. There was no difference between the two groups with respect to the percentage of patients who received concurrent antibiotics for gram-positive organisms. More than 60 percent of the patients received mechanical ventilation. Essentially, all had new lung infiltrates as shown by chest radiography, leukocytosis, recent onset of fever, and increased volume of purulent secretions. Half had multilobar pulmonary infiltrates. Their mean age was 73 years, with none under age 50. Most had chronic obstructive pulmonary disease, congestive heart failure, or both. By the prognostic nutritional index criteria, over 70 percent were nutritionally deficient at entry. The majority of infections were caused by Pseudomonas, Enterobacter, Klebsiella, and Escherichia coli. Aztreonam eradicated 92 percent of the causative gram-negative organisms, compared with 57 percent for tobramycin (p less than 0.05). Aztreonam produced a favorable clinical response (cure or improvement) in 93 percent of patients, compared with 50 percent for tobramycin (p less than 0.05). There were no differences in the minor adverse effects observed in the two treatment groups. Overall, aztreonam was superior to tobramycin for treatment of pneumonia due to susceptible gram-negative bacteria in these critical care patients.

Imipenem therapy of Pseudomonas aeruginosa and other serious bacterial infections

Imipenem is the first of a new class of beta-lactam antimicrobial agents with remarkable and extremely potent in vitro activity against most commonly isolated bacterial pathogens, including Staphylococcus aureus, enterococcus, members of the family Enterobacteriaceae, Pseudomonas aeruginosa, Bacteroides fragilis, and Hemophilus influenzae. The clinical efficacy and toxicity of imipenem were evaluated in 35 patients with 38 different infections. The overall clinical response was favorable (infections cured or improved) in 89% of the infections (34 of 38). Of the 17 infections with P. aeruginosa, 15 were cured or improved. However, P. aeruginosa isolates resistant to imipenem emerged during the therapy of six infections, and two cases of P. aeruginosa septicemia later relapsed after imipenem therapy. Gastrointestinal toxicity (nausea with or without emesis) occurred in 17% of the patients (6 of 35) but was ameliorated by slowing the rate of intravenous infusion or lowering the dose of imipenem. Except for certain severe P. aeruginosa infections, imipenem is effective and relatively safe therapy for infections caused by susceptible organisms.

Piperacillin. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Piperacillin is one of the new generation of semisynthetic penicillins which can be administered intravenously or intramuscularly. It has a broad spectrum of activity against Gram-positive and Gram-negative aerobic and anaerobic bacteria. Although piperacillin has shown greater activity against beta-lactamase-producing organisms than the other penicillins, it is hydrolysed by the plasmid-mediated beta-lactamases (TEM-1). Activity against Pseudomonas aeruginosa is better than that of ticarcillin, carbenicillin and mezlocillin. Although only limited controlled studies have been reported, in those which have been conducted and in a larger number of open studies piperacillin was effective in the treatment of complicated urinary tract infections and lower respiratory tract infections, particularly pneumonia, caused by Gram-negative bacilli. Favourable clinical results have been obtained in patients with infections caused by mixed aerobic/anaerobic organisms (such as intra-abdominal infections) but the relatively average in vitro activity of piperacillin against Bacteroides fragilis may not indicate its usage in situations where this organism is the suspected or proven pathogen. Piperacillin in combination with an aminoglycoside or a 'third generation' cephalosporin gave encouraging results in the treatment of infections in immunocompromised patients, whilst its penetration into the diseased central nervous system and lack of toxicity indicate a potential value in the treatment of neonatal Gram-negative bacillary meningitis, particularly where the causative organism is Pseudomonas aeruginosa. Whether piperacillin alone is appropriate therapy for conditions usually treated with aminoglycosides (other than pseudomonal infections) needs additional clarification, but if established as equally effective in such conditions it has the advantages of its apparent lack of serious adverse effects and freedom from the need to undertake plasma concentration monitoring. These advantages would not, however, apply when considering one of the new (third generation) cephalosporins as alternative therapy in non-pseudomonal infections. Generally, however, it is still considered necessary to treat serious and complicated infections with combination therapy, either a cephalosporin, or in cases of resistance to P. aeruginosa an aminoglycoside.

Antibiotic use in cystic fibrosis

Chronic pulmonary infections contribute significantly to the morbidity and mortality of patients with CF. The primary pathogens are Pseudomonas aeruginosa (PA) and Staphylococcus aureus. Hemophilus influenzae has been isolated from a significant number of patients also. A number of the beta-lactam and aminoglycoside antibiotics reportedly have altered pharmacokinetic variables in CF. Therapy of acute pulmonary deterioration consists of intravenous antibiotics for two weeks. Antibiotic selection is based on culture and sensitivity results. Currently, the combination of a broad-spectrum penicillin and an aminoglycoside seems to provide the best results. Prophylactic antibiotics are effective if the primary isolates are sensitive to the agents used. Chronic PA infections are problematic because effective oral agents are not available. Aerosolized antibiotics do not improve results over adequate systemic therapy for acute exacerbations. Questions regarding optimal dosages, frequency, and duration of therapy remain.

Moxalactam plus piperacillin versus moxalactam plus amikacin in febrile granulocytopenic patients

In a prospective randomized trial, febrile granulocytopenic patients received either moxalactam plus piperacillin or moxalactam plus amikacin as initial empiric antimicrobial therapy. Most patients were also given prophylactic vitamin K. The overall response rates for the two regimens were similar (105 of 136, or 77 percent, for moxalactam plus piperacillin versus 107 of 136, or 79 percent, for moxalactam plus amikacin). For Pseudomonas aeruginosa infections, the response rate was better in patients receiving moxalactam plus amikacin (seven of nine versus one of five, p = 0.06); two patients treated with moxalactam plus piperacillin experienced relapse of P. aeruginosa bacteremia in association with the emergence of beta-lactam-resistant P. aeruginosa isolates. On the other hand, bacteremic enterococcal superinfections occurred in seven patients receiving moxalactam plus amikacin but in none given moxalactam plus piperacillin (p = 0.02). Serious side-effects were minimal with both regimens, and nephrotoxicity was less common in patients receiving moxalactam plus piperacillin (two of 136 versus six of 136, p = 0.28). There was no antibiotic-related hemorrhage. These results suggest that the overall efficacy and toxicity of moxalactam plus piperacillin and moxalactam plus amikacin are similar. Moxalactam/piperacillin therapy may be limited in certain patients by the emergence of beta-lactam-resistant P. aeruginosa, whereas enterococcal superinfections may complicate moxalactam/amikacin therapy.

Imipenem antagonism of the in vitro activity of piperacillin against Pseudomonas aeruginosa

The MICs of imipenem and piperacillin, alone and in combination, against Pseudomonas aeruginosa were determined in a checkerboard titration microdilution assay. A dramatic, one-way antagonism of imipenem for piperacillin was demonstrated in 28 of the 35 strains examined; antagonism was associated with the induction of a beta-lactamase.

Activities of cefoxitin and cefotetan against Mycobacterium fortuitum infections in mice

Mice inoculated intravenously with Mycobacterium fortuitum 18367 were treated subcutaneously with cefoxitin or cefotetan once daily for 4 weeks, beginning 24 h after challenge. Both drugs suppressed spinning disease, and both reduced the severity of renal lesions and the number of organisms in the kidneys and liver but not in the lungs or spleen. These therapeutic effects were dose-dependent.

Prospective randomized trial of piperacillin monotherapy versus carboxypenicillin-aminoglycoside combination regimens in the empirical treatment of serious bacterial infections

Piperacillin as a single agent was compared in a prospective randomized trial with carboxypenicillin-aminoglycoside combinations in empirical therapy of serious bacterial infections. The difference in the clinical response rates with piperacillin (77% of 26 infection episodes) and combination therapy (75% of 24 infection episodes) were not statistically significant. Fewer adverse effects occurred in the piperacillin-treated group (42%) than in the combination-treated group (71%) (P = 0.0399 by Fisher's exact test), although neither nephrotoxicity nor hypokalemia alone was significantly less frequent in patients receiving piperacillin. However, the emergence of resistant organisms during therapy was more frequent among patients receiving piperacillin alone (42% of patients) than among patients receiving combination therapy (17% of patients) (P = 0.465 by Fisher's exact test). Moreover, emergence of resistance accounted for 5 of 9 patients with treatment failure, superinfection, or both when piperacillin was used as a single agent, compared with 2 of 10 similar patients in the combination group (P = 0.1299 by Fisher's exact test). The use of piperacillin as a single agent in the treatment of serious bacterial infections is not advocated, and the addition of an aminoglycoside to prevent emergence of resistance during empirical therapy of such infections is strongly recommended.

Pseudomonas aeruginosa

P. aeruginosa is widely distributed in nature and in the hospital environment with a predilection for moist areas. Its inherent resistance to many antimicrobials and its ability to produce many enzymes contribute to its pathogenic potential as both a primary and a secondary cause of infection. It is easily grown and identified in the microbiology laboratory. However, susceptibility testing remains a problem. Currently, the best approach to treatment is an aminoglycoside and an antipseudomonal beta-lactam antimicrobial. Typing can differentiate strains, but should be reserved for specific epidemiologic problems.

Investigation of an epidemic of multi-drug resistant Pseudomonas aeruginosa

Inter- and intrahospital epidemics of nosocomial infections due to gram-negative bacilli resistant to many antimicrobials have been well-documented. Prospective studies on the use of isolation along with epidemiologic analysis and appropriate environmental control have been lacking. In the six-month period from November 1978 to April 1979 Pseudomonas aeruginosa (MDR) resistant to all antibiotics except amikacin was isolated from 15 patients. This organism had not previously been seen in our hospital. Epidemiologic assessment of infected patients revealed that nine of 15 patients had contact either with a previously infected case or contaminated area. All strains of P. aeruginosa were identical by pyocin typing and antibiogram. The organism was present in an environmental reservoir, the urine graduated cylinder, and was found in three of eight receptacles (p = 0.002 vs. other environmental cultures). A case control study of patient risk factors showed aminoglycoside use, other antibiotic use, surgery, intravenous lines, Foley catheter use and mechanical ventilation to be no more frequent in cases than controls. The use of aminoglycosides in only 40% of cases suggests that antibiotic pressure was not the sole factor in perpetuating the epidemic.

Preliminary report comparing piperacillin and carbenicillin for complicated urinary tract infections

Piperacillin is a new semisynthetic penicillin with a broad spectrum of in vitro activity against common gram-negative urinary tract pathogens. We compared the efficacy and safety of piperacillin versus carbenicillin in patients with complicated urinary tract infection. A total of 56 adult patients (mean age 55 years) in stable medical condition with 1 or more structural genitourinary abnormalities entered the study. Of these patients 27 were evaluated for antibiotic efficacy. There were 20 lower tract and 7 upper tract infections, of which 17 were acute and 10 were chronic. Patients were randomized into 2 groups: 17 patients with 18 organisms received single agent treatment with 181 mg. per kg. intravenous piperacillin daily for 6 days and 10 patients with 11 organisms received 270 mg. per kg. intravenous carbenicillin daily for 6 days. Infecting organisms were Escherichia coli 45 per cent, Proteus mirabilis 14 per cent, Klebsiella pneumoniae 14 per cent. Enterobacter species 10 per cent, Pseudomonas aeruginosa 7 per cent and so forth. Antimicrobial susceptibility assessed by measurement of minimal inhibitory concentration and disk diffusion zone size demonstrated superior activity of piperacillin over carbenicillin for most micro-organisms tested. All patients responded clinically. The bacteriologic cure rate was 72 per cent at 5 to 9 days after therapy in both groups. Three patients who received piperacillin had urosepsis and were cured. No resistance emerged during therapy. Superinfections developed in 5 patients on carbenicillin (50 per cent) and in 4 patients on piperacillin (24 per cent), and none was resistant to piperacillin. Superinfections were attributed to catheterization and structural genitourinary abnormalities. The over-all incidence of adverse effects in patients on piperacillin was less than that of those on carbenicillin, 31 and 51 per cent respectively. Side effects in both groups were mild and did not require discontinuation of therapy. There were no significant alterations in fluid and electrolyte balance, or hematologic or renal function.

Piperacillin pharmacokinetics in pediatric patients

The pharmacokinetics of piperacillin were studied in 15 pediatric patients (age range, 3.3 to 14.3 years). Piperacillin was administered in a dosage of 1.5 +/- 0.4 g/m2 (mean +/- standard deviation) every 4 to 6 h. Peak serum concentrations ranged from 69 to 354 micrograms/ml. The mean elimination half-life was 37.0 +/- 13.3 min, which is shorter than that observed in most adults with normal renal function. The mean elimination half-life in three patients with renal impairment was 60.1 +/- 12.4 min, and the mean ratio of renal clearance to total clearance was 0.57. These results suggest a significant nonrenal elimination of piperacillin. Based on these data, a dosage of 1.5 g/m2 given as a 30-min infusion every 4 h is suggested for children with normal renal function. For patients with renal impairment, the daily dosage could be calculated as follows: corrected dose = normal dose x (0.35 + [0.65 x (ClCr/0.06)]), where ClCr is the creatinine clearance expressed as liters per minute per square meter.

Activity and synergy of ureido penicillins and aminoglycosides against Pseudomonas aeruginosa

The in vitro activities of piperacillin, azlocillin, mezlocillin, sulbenicillin and ticarcillin were compared with those of carbenicillin using 88 clinical isolates of Pseudomonas aeruginosa. The minimum inhibitory concentrations (MIC) and the minimum bactericidal concentrations (MBC) were determined by standard techniques. The MIC for 90% of the strains was 7.5 mg/l for piperacillin, 10.0 mg/l for azlocillin, 26.5 mg/l for mezlocillin, 48.4 mg/l for sulbenicillin, 50.0 mg/l for ticarcillin and more than 100 mg/l for carbenicillin. The MBC/MIC ratio was 1.3 for piperacillin, 1.9 for ticarcillin, 2.1 for sulbenicillin, 3.3 for mezlocillin and 4.5 for azlocillin. The susceptibilities of the same strains to four aminoglycosides were tested. The MIC for 90% of the strains was 0.3 mg/l for sisomicin and tobramycin, 1.5 mg/l for amikacin, and 2.2 mg/l for gentamicin. The effect of combining piperacillin, azlocillin and mezlocillin with gentamicin, tobramycin, sisomicin and amikacin was studied using checkerboard titration. The highest degrees of synergy were found with the combinations of piperacillin and an aminoglycoside. Strong potentiation was observed in 85% of the strains with piperacillin - sisomicin and in 50% with piperacillin - gentamicin. The synergistic effects of azlocillin and mezlocillin in combination with an aminoglycoside (observed in 30-65% of the strains) were for the most part moderate or slight. No antagonism was observed.

Principles of antibiotic therapy

Many host factors influence both the presentation and response to therapy of clinical infections. Since the selection of an appropriate antibiotic depends significantly upon results of in vitro susceptibility testing, great care should be taken to obtain suitable specimens for culture and susceptibility studies. The likelihood that antibiotic therapy will be successful depends upon whether the drug will reach the infected site at the desired concentration and for an optimal duration of time. Local factors such as pH, oxygen tension, and the presence of inactivating substances may affect antibiotic activity. At present, many of our recommendations for dose, dosage intervals, and duration of therapy are largely empiric. Enhanced understanding of the pharmacokinetics of antimicrobial agents should provide the basis for more rational therapy in the future. The remainder of this symposium will present the data from which such recommendations can be drawn.

Piperacillin in surgical infections: a clinical trial

Piperacillin was administered in eighteen patients with mixed infections. Three had osteomyelitis, two had peritonitis, two had gangrenous toes, one had bronchopneumonia, and the other ten had leg ulcers of various types accompanies by cellulitis. In eleven patients one of the infecting organisms was Pseudomonas aeruginosa, and another had Pseudomonas maltophilia. All had appropriate surgical treatment, which in nine patients included skin grafting in the presence of Pseudomonas aeruginosa. All the patients were clinically cured except for one with osteomyelitis who relapsed and was found to have a residual sequestrum. None of the skin grafts failed. In other patient who underwent grafting, cloxacillin was also given because she had a beta-lactamase-producing staphylococcus. The only adverse reaction was thrombophlebitis of the vein used for drug administration in 15 out of 18 patients. One hundred and five other isolates of Pseudomonas aeruginosa were tested in the laboratory against piperacillin and resistance to the drug was found to be rare. It was concluded that piperacillin is a safe drug to use, is effective against a wide range of organisms, and is particularly effective in preventing the destruction of skin grafts by Pseudomonas aeruginosa. It is likely to be ineffective against beta-lactamase-producing staphylococci, and when these are present also, it would be wise to use another drug such as cloxacillin in addition.

Clinical evaluation of piperacillin with observations on penetrability into cerebrospinal fluid

Piperacillin, a new semisynthetic penicillin, was evaluated for efficacy and safety in 26 patients, most of whom had pneumonia. Included were four patients with gram-negative meningitis in whom the penetration of piperacillin into cerebrospinal fluid was determined. Cure was achieved in 11 of 17 patients with pneumonia; another 4 were improved. One relapse and one failure occurred among nine patients with gram-negative pneumonia. Cure or improvement occurred in seven of nine patients with gram-negative infection in various extrapulmonary sites. Piperacillin given by continuous infusion in a dosage ranging from 324 to 436 mg/kg of body weight per day to four patients with meningitis resulted in a mean cerebrospinal fluid level of 23 micrograms/ml at 24 h; the mean penetration of piperacillin into the cerebrospinal fluid was 32% at this interval. Levels of piperacillin in cerebrospinal fluid collected later during the course of therapy were also adequate. Adverse effects were noted in six patients, but only one episode of granulocytopenia was serious. Emergence of resistance to piperacillin did not occur, and only one superinfection was noted. Piperacillin appeared to be efficacious in the treatment of pneumonia. It penetrated well into the cerebrospinal fluid of patients with meningitis and may be useful for treatment of selected gram-negative infections in extrapulmonary sites.

Clinical evaluation of piperacillin in bronchopulmonary infection

Piperacillin sodium, a new semi-synthetic penicillin, was administered to eleven patients with acute bronchial infection and to fourteen patients with pneumonia. Piperacillin dosage was either 8 g/day (twenty-one patients) or 16 g/day (four patients) intravenously for periods of between 5 and 15 days. Clinical assessment was determined by diminution of sputum purulence, eradication of pathogen from sputum, clinical and radiological progress. There was a beneficial response in all but six patients, two of whom had severe chronic infective bronchial disease and four had underlying pulmonary malignancy. The low toxicity of piperacillin was confirmed, although one patient with chronic renal failure had a significant decline in renal function. Dosage should be reduced in patients with renal impairment.