Emergence of clinical isolates of Staphylococcus aureus resistant to gentamicin and correlation of resistance with bacteriophage type

Successful Treatment of Apparent Methicillin-Resistant S. Aureus Endocarditis with Gentamicin and Cephalothin

A pediatric patient with Staphylococcus aureus endocarditis was treated unsuccessfully with methicillin 74 mg/kg/day as an initial dosage and 185 mg/kg/day as a maximum dosage over a 21-day period. Treatment failure was a result of apparent methicillin resistance, which may have been induced by the initial use of suboptimum methicillin dosages. The methicillin was discontinued and the patient became afebrile within six hours of receiving a combination of cephalothin and gentamicin. Combination therapy was continued for a total of 42 days, with eventual trough serum MBC dilutions of 1:32 and gentamicin and cephalothin dosages of 2.7 and 166 mg/kg/day respectively.

The patient was cured without any adverse sequelae. The rapid improvement in this patient's condition and his cure after receiving the combination therapy was probably due to the synergistic activity of gentamicin and cephalothin against S. aureus.

Phage typing, PCR amplification for mecA gene, and antibiotic resistance patterns as epidemiologic markers in nosocomial outbreaks of methicillin resistant Staphylococcus aureus

Staphylococcus aureus is one of the major causes of community and hospital-acquired infections. Bacteriophage considered as a major risk factor acquires S. aureus new virulence genetic elements. A total number of 119 S. aureus isolated from different specimens obtained from (RKH) were distinguished by susceptibility to 19 antimicrobial agents, phage typing, and PCR amplification for mecA gene. All of MRSA isolates harbored mecA gene, except three unique isolates. The predominant phage group is belonging to the (mixed group). Phage group (II) considered as an epidemiological marker correlated to β-lactamase hyper producer isolates. MRSA isolates indicated high prevalence of phage group (II) with highly increase for phage types (Ø3A), which were correlated to the skin. Phage types (Ø80/Ø81) played an important roll in Community Acquired Methicillin Resistant S. aureus (CAMRSA). Three outpatients MRSA isolates had low multiresistance against Bacitracin (Ba) and Fusidic acid (FD), considered as CAMRSA isolates. It was detected that group I typed all FD-resistant MSSA isolates. Phage groups (M) and (II) were found almost to be integrated for Gentamycin (GN) resistance especially phage type (Ø95) which relatively increased up to 20% in MRSA. Tetracycline (TE) resistant isolates typed by groups (II) and (III) in MSSA. Only one isolate resistant to Sulphamethoxazole/Trimethoprim (SXT) was typed by (III/V) alone in MSSA. MRSA isolates resistant to Chloramphenicol (C) and Ba were typed by all groups except (V). It could be concluded that (PERSA) S. aureus isolates from the wound that originated and colonized, and started to build up multi-resistance against the topical treatment antibiotics. In this study, some unique sporadic isolates for both MRSA and MSSA could be used as biological, molecular and epidemiological markers such as prospective tools.

Phage-typing of Staphylococcus aureus from cases of bacteraemia

Isolates of Staphylococcus aureus from 98 cases of bacteraemia from 16 different hospitals were phage-typed. Fifty-six isolates were associated with sporadic infections and 42 with hospital outbreaks. In the sporadic cases, group I strains, particularly types 29, 52, or 29/52, were very frequent (39.2%), followed by non-typable strains. Type 94/96 was also common (14.2%). In hospital outbreaks, mixed I and III strains (multiply-resistant) were found in 73.6% and non-typable strains in 21.4%.

Nosocomial infections with methicillin and tobramycin resistant Staphylococcus aureus--implication of physiotherapy in hospital-wide dissemination

From January 1979 to July 1980, methicillin and tobramycin resistant Staphylococcus aureus was isolated from 45 patients at a Veteran's Administration hospital. Of these 45, 36 (80%) had clinical infections involving non-surgical wounds (16), urinary tract (10), blood (8), surgical wounds (7), and sputum (5). The epidemic strain had a single phage type (47/54/75/77/83A), a single, 16.4 Md plasmid, and produced an aminoglycoside inactivating enzyme (AAD[4']). Compared to a control group of patients with nosocomial antibiotic susceptible S. aureus infections, patients with the epidemic strain had more hospital days before a positive culture (p = .004), more severe underlying disease (p = .006), received antibiotics more often (p = .0018), and underwent physiotherapy more often (p = .00007). Although selected environmental and personnel cultures were negative for the epidemic strain, epidemiologic investigation suggested that hospital-wide dissemination of S. aureus may have occurred through patient contacts in the physiotherapy department with subsequent clusters of cases occurring on several wards.

Comparison of phage typing, plasmid mapping, and antibiotic resistance patterns as epidemiologic markers in a nosocomial outbreak of methicillin-resistant Staphylococcus aureus infections

Isolates of methicillin-resistant Staphylococcus aureus obtained during a nosocomial outbreak were analyzed by phage typing, plasmid mapping, and antibiotic susceptibility patterns for epidemiologic markers. Antibiotic susceptibility patterns were of limited use epidemiologically because of multiple resistance and similarity of the strains. Phage typing demonstrated that the outbreak consisted of multiple introductions of MRSA organisms into the hospital from the community and from other hospitals, and of circulation of one predominant phage type, 6/47/54/81. Plasmid mapping further subdivided the organisms of this phage type into two different groups, one of which carried two particular plasmids. Organisms carrying these plasmids were significantly more resistant to methicillin and cephalosporins and were isolated from patients who had received prior antibiotic treatment.

Quantitative antibiogram as a potential tool for epidemiological typing

Forty stock, sink drain and clinical isolates of gram-negative bacilli were tested by broth microdilution against eight aminoglycoside antibiotics. Results show that quantitative antibiograms provide more information as epidemiological tools than qualitative antibiograms.

Gentamicin-resistant Staphylococcus aureus strains isolated in Denmark in 1979

In 1979 seven gentamicin (G)-resistant (res.) Staphylococcus aureus strains caused epidemic episodes in eight Danish hospitals. Furthermore, a total of 37 resistant strains were isolated from separate incidents. All the G-res. strains were resistant to kanamycin, sisomicin and tobramycin, five to amikacin and two to cephalothin. None were resistant to netilmicin. Twelve out of the total of 44 strains were multiply-res. (resistant to penicillin, streptomycin and tetracyclines), and 10 of these were also resistant to methicillin (M). All phage groups/complexes were represented, group III by 13, and the 83A complex by seven strains. Multiply-res. strains, resistant to both M and G were all resistant to mercury, but sensitive to arsenate, whereas such strains resistant to either M or G usually have been found resistant to both metals. Twenty-three strains lost resistance to G upon storage, among them only one multiply-res. Loss of resistance did not influence the metal resistance pattern. From one patient only, the various isolates (nine) differed in respect to bacteriological properties. It was concluded, however, that they all were descendants of the same unstable strain. In the majority of the cases treatment with G had preceded isolation of the resistant strain.

Eradication of epidemic methicillin-gentamicin-resistant staphylococcus aureus in an intensive care nursery

A methicillin-resistant strain of Staphylococcus aureus (phage type 47,54,75,83A) became epidemic in our 50 bed level III nursery, with a colonization rate of 70 percent and an infection rate of more than 25 percent. This prevalence and the appearance of gentamicin resistance necessitated epidemic control measures. Standard measures included separate housing for infants in whom colonization had occurred and infants in whom it had not, low nurse to patient ratios, and cohorting of all personnel. Use of all antibiotics was curtailed by the requirement of infectious disease consultation. Gentamicin was available only on order of the Director. The colonization rate fell from 55 percent to 25.4 percent, the first-week colonization rate from 31 percent to 0 percent, and the infection rate from 29.3 percent to 15.9 percent over eight weeks. The mean duration of antibiotic therapy decreased from 12.21 to 9.05 days per treated patient; however, the frequency of gentamicin usage and the proportion of gentamicin resistance were unchanged. Nurse to patient ratios were modified to allow increased admissions, but cohorting was continued for 12 weeks until all infants in whom colonization had occurred were discharged. With the elimination of the reservoir, no further colonization occurred and antibiotic resistance did not reappear. Standard infection control measures can eliminate epidemics of multiple antibiotic-resistant Staph. aureus, and control of antibiotic usage may present re-emergence of resistant strains.