Klebsiella neonatal injections: mechanism of broadening aminoglycoside resistance

Development of immunization trials against Klebsiella pneumoniae

Klebsiella pneumoniae is the most common cause of nosocomial respiratory tract and premature intensive care infections, and the second most frequent cause of Gram-negative bacteraemia and urinary tract infections. Drug resistant isolates remain an important hospital-acquired bacterial pathogen, add significantly to hospital stays, and are especially problematic in high impact medical areas such as intensive care units. Many investigations worldwide proved the increasing resistance of such pathogen, resulting in an average rate of 1.63 outbreak every year. A variety of preventive measures were applied to reduce such incidences. Immunotherapy and passive immunization researches as well found their way to the treatment of Klebsiella. During the last 40 years, many trials for constructing effective vaccines were followed. This up-to-date review classifies such trials and documents them in a progressive way. A following comment discusses each group benefits and defects.

Two different types of fosfomycin resistance in clinical isolates of Klebsiella pneumoniae

The fosfomycin susceptibility of 100 clinical isolates of Klebsiella pneumoniae and the resistance mechanisms utilized by resistant strains were examined. Washed cells prepared from the strains demonstrating MICs of more than 8 micrograms ml-1 of fosfomycin inactivated the drug. A crude extract from strain Tf129B, highly resistant to fosfomycin, was used to study the enzymatic properties of the drug-inactivating enzyme. The optimum pH for inactivation was 7.8 and the optimum temperature of the reaction was 37 degrees C. Glutathione was shown to be effective as a cofactor in the inactivation. It was suggested that the inactivating enzyme of Klebsiella pneumoniae was fosfomycin: glutathione-S-transferase, a constitutive enzyme located in the periplasmic space. A good correlation was found between the specific activities of this enzyme and the MIC levels; however, certain strains showed a low level of fosfomycin:glutathione-S-transferase activity which could not account for the increased MIC. Strains Tf129B and Tf408E, both demonstrating MICs of more than 1024 micrograms ml-1 of fosfomycin carried a transferable resistance plasmid. In strain Tf129B, the mechanism of fosfomycin resistance was due to a high level of enzymic activity. In strain Tf408E, it was determined to be mainly due to the reduced permeability of the cell membrane.

Susceptibility of multidrug-resistant isolates of Klebsiella pneumoniae to silver nitrate

Multidrug-resistant (MDR) clinical isolates of Klebsiella pneumoniae were checked for their sensitivity toward silver nitrate by the tube-dilution method. Nearly 75% of MDR strains could be successfully inhibited by 5 mg/L of silver nitrate. A significant correlation was observed between incidence of silver and trimoxazole resistance and silver and kanamycin resistance in these isolates. The genetic linkage of these two properties could not be proved since simultaneous curing and co-transfer studies gave negative results.

Association between colistin resistance and broad-spectrum recipient deficiency in Klebsiella pneumoniae

A colistin-resistant mutant of Klebsiella pneumoniae served well as a donor but not as a recipient in conjugation. A nearly 1,000-fold difference between colistin-susceptible and colistin-resistant forms of this strain was observed by using donors of plasmids of four incompatibility groups. Recipient efficiency was not restored by filter matings.

The epidemiology of nosocomial infections caused by Klebsiella pneumoniae

Klebsiella pneumoniae causes serious epidemic and endemic nosocomial infections. We conducted a literature review to characterize the epidemiology of epidemic K. pneumoniae outbreaks. Eighty percent of the outbreaks (20/25) involved infections of the bloodstream or urinary tract. Person-to-person spread was the most common mode of transmission, and nearly 50% of the outbreaks occurred in neonatal intensive care units. No one serotype predominated, and no association was found between serotype and either the site of infection or antimicrobial susceptibility pattern. We used data reported to the Centers for Disease Control (CDC) by hospitals participating in the National Nosocomial Infections Study (NNIS) to describe the epidemiology of endemic K. pneumoniae infections. In the 8-year period from 1975 through 1982 the nosocomial K. pneumoniae infection rate was 16.7 infections per 10,000 patients discharged. The rate of infection at medical school-affiliated hospitals was significantly greater than at nonaffiliated hospitals; furthermore, the rate of infection at large affiliated hospitals was greater than at small affiliated hospitals. The rate of infection varied by service, with the highest rate found on the medicine service. During the 8-year period, 184 deaths were caused by nosocomial K. pneumoniae infections (184 deaths/16,969 infections, case-fatality ratio 1.1%), with higher ratios in pediatrics (5%) where there was a 12% mortality in children infected with an aminoglycoside-resistant strain.

Antimicrobial agent susceptibility patterns of bacteria in hospitals from 1971 to 1982

Bacterial susceptibility to 16 commonly used antibiotics was analyzed for a 12-year period (from 1971 to 1982, inclusive). Susceptibilities of 5,828,243 strains isolated from a mean of 242 hospitals nationwide and of 194,575 strains isolated at the Massachusetts General Hospital, Boston, Mass., and the Bronx Lebanon Hospital Center, New York, N.Y., were compared. Strains of Escherichia coli, Staphylococcus aureus, Haemophilus influenzae, and Pseudomonas aeruginosa showed virtually the same susceptibilities to antibiotics throughout the 12-year period, whereas Streptococcus faecalis and Staphylococcus epidermidis showed significant increases in resistance to most antibiotics. The close similarity between antibiotic susceptibilities shown at both the 242 hospitals and the 2 individual hospitals suggests that this analysis accurately reflects trends of bacterial resistance to antibiotics in U.S. hospitals. Since most of the species analyzed produce serious disease and high mortality, their susceptibility to antibiotics is relevant both to physicians treating infectious diseases and to epidemiologists.

Lipopolysaccharide changes in impermeability-type aminoglycoside resistance in Pseudomonas aeruginosa

Clinical isolates of Pseudomonas aeruginosa were examined for the basis of impermeability-type aminoglycoside resistance. Two apparently related burn isolate strains with high-level (strain 8803) and low-level (strain 13934) gentamicin resistance each had a plasmid. Transformation of the plasmid from either strain to P. aeruginosa PAO503 resulted in low-level gentamicin resistance. No mechanism for this resistance could be determined. Low-level gentamicin and streptomycin resistance from strain 8803 (but not 13934) was transduced with phage E79.tv2 to PAO503 without transfer of plasmid DNA. Transductants like strain 8803 showed absence or reduction of the lipopolysaccharide (LPS) "ladder" pattern of PAO503, had a change in chemical composition of LPS, and, like strain 8803, had a reduced capability to accumulate streptomycin. Comparison of the resistant clinical isolates 8803 and P10 with the apparently related but less-resistant strains 13934 and P10R, respectively, showed the latter strains had LPS ladder patterns and the former strains did not. Strain 8803 had normal outer membrane protein profiles, electron transport components, and transmembrane electrical potential relative to PAO503 and has been previously shown to have no detectable gentamicin-modifying enzymes and normal protein synthesis. We conclude that low-level impermeability-type aminoglycoside resistance in P. aeruginosa results from conversion of smooth LPS to superficial or deeper rough LPS phenotypes. High-level resistance apparently results from a plasmid-specified, but as yet unknown, mechanism combined with the preceding change in LPS structure.

Molecular epidemiology of sequential nursery epidemics caused by multiresistant Klebsiella pneumoniae

Multiresistant Klebsiella pneumoniae has been endemic among adult patients at Vanderbilt University Medical Center since 1973. Multiresistant K. pneumoniae was absent from pediatric wards until 1979, when it produced an epidemic in the intensive care nursery followed a year later by a second epidemic involving K. pneumoniae of the same serotype. The 105 megadalton (Md) conjugative resistance (R) plasmid (pCER7999) transferring multiple antibiotic resistance in the adult, endemic strain was found also in isolates from the first epidemic in the intensive care nursery. The mother of a child in the nursery harbored E. coli containing the same 105 Md R plasmid. The second epidemic also involved a 105 Md conjugative R plasmid, which, however, by molecular analysis was different from the first epidemic plasmid and also pCER7999. Thus, the second epidemic resulted from the introduction of a new, unrelated multiresistant K. pneumoniae strain. Contemporary hospital epidemiology often requires the application of molecular techniques for an understanding of nosocomial infections.